# Edison dynamo



## deverett

I've recently completed making an Edison dynamo from about 1890.  This has been an on/off project for a couple of years filling in during other jobs.

















It started off with me buying a set of castings from Poland.  At the time, I had no idea what an Edison dynamo was or looked like, but it seemed like an interesting project and the price was cheap.  The kit was quite complete including the rotor, which looks like it came from an old electric drill.






Looking at pics of Edison dynamos on the internet, I soon realised that the model as designed would not look anything like the real thing.  I tried to modify the base casting to match the full size, but eventually gave up on that idea, so everything apart from the bearing housings and rotor were ditched and I set about carrying on with odds and sods lying around.

The numerous internet pics were of different sized machines and in different state of preservation/decay, but most of them showed a family likeness regardless of generating capacity.  So I have no idea what size/generating capacity this represents.   The motor armature was the dictating factor of model size.


Dave
The Emerald Isle


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## Rod Cole

Very nice, wonder if the kit is still available?


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## kuhncw

Dave,

Nice work on an interesting project.  Have you driven it to check voltage, etc?

Chuck


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## Rod Cole

I was thinking the same as I hit post, how is the out-put?


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## k2steve

Great looking model. Do you have plans to power it with a engine?


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## deverett

Rod
I bought the kit off eBay, and as far as I know it was just a feeler for eBay sales because they have not advertised there since.  The Polish company can be found here:  https://www.danielasteam.com/e-generator-kit
If you look at their finished article and mine, you will understand why I changed it.  I would not recommend buying the kit, everything is so simple to make up from stock materials.  I should have taken the ball bearings off the rotor shaft, but was worried that I would score it in the process.




These two were the main inspiration for my version, although they are a slightly later version.

Chuck et al
I haven't yet powered it up.  Wondering what to use as a flat belt.  My latest idea is a strip of denim from old jeans, dyed in tea and with some pva glue added to prevent fraying; trying to replicate a canvas belt.  I tried a strip of leather, but that wasn't a success.  I'll be using a fractional hp electric motor to power it (I don't have a suitable model engine).

Dave
The Emerald Isle


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## Jasonb

Looks good Dave, I've half drawn up an old bi-polar motor which is not dissimilar just you put the power in and get rotation out.

You can get some 1mm thick drive belts that have reinforcing in them that work quite well, I have used them for governors and cooling pumps on  a screen cooled H&M engine

https://www.beltingonline.com/rubber-nylon-flat-endless-belts-1mm-thick-13049


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## bobden72

Hi Dave nice dynamos but showing my ignorance what does the large leaver to the rear of the stator do please.


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## deverett

JB.
I'll try my 'artificial canvas' first and if not successful, I might try you r suggestion.
Have you watched this video 

Bob
The lever on the bridge piece is the on/off switch.  The other (larger) one adjusts the phase (I think) but to be honest I don't have a clue!
Come up and see it at Doncaster in May.

Dave
The Emerald Isle


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## bobden72

deverett said:


> JB.
> I'll try my 'artificial canvas' first and if not successful, I might try you r suggestion.
> Have you watched this video
> 
> Bob
> The lever on the bridge piece is the on/off switch.  The other (larger) one adjusts the phase (I think) but to be honest I don't have a clue!
> Come up and see it at Doncaster in May.
> 
> Dave
> The Emerald Isle



Thanks for that Dave yes I can see now how it would change the phase of the output.  Would love to come and see it in May but by then I will be half way through walking from Lands End to John O Groats.  Will catch up with you  some time.


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## deverett

bobden72 said:


> Thanks for that Dave yes I can see now how it would change the phase of the output.  Would love to come and see it in May but by then I will be half way through walking from Lands End to John O Groats.  Will catch up with you  some time.



Only a small detour then?

Dave
The Emerald Isle


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## tjwal

Very nice.  The ephf museum is only a few hundred kms away.  I’ll have to check it out someday.
The large lever is to adjust the angle of the brushes and hence the rotor magnetic field angle in relation to the armature field.  Since this is a DC generator it really doesn’t change the phase.  I don’t recall why this is done but I’m guessing that it has to do with the optimum rotor/armature angle changing with load.


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## Jasonb

Thank's Dave, I think I did come across that one a while ago, bit bigger than what I'm thinking of which will be more along the lined of the Edison antique fan motors which could almost be made full size. The problem with all these videos and images is that I get distracted by other things that come up, this "electric engine" was something I saw while looking at the bi polar motors and had to make one.


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## bobcjohn

We have museum in town that has one of Edison's type K dynamos in the basement, (poor condition). They allowed me to gather dimensions and pictures a few years ago. I built a dynamo based on those dimensions. It was scaled from an old armature (2" dia) I had in the junk drawer. Initially, I had to run it as a motor to put a small magnetic field into the poles. At first it would only produce 3 volt at no load, but the more I used the better it got, magnetic field I'd guess. Now it will run 12 volts no load and drop to 6 volts depending on the load. I found that the handle that moves the brushes changes the voltage. I was told that's because it picks the voltage off of the armature at different angles to the pole magnetic line of flux. 90° is the highest voltage.

Your dynamo is a much better representation of the Edison dynamo than mine. I'd be real interested in your test results.

Don't know how to insert a picture, sorry about that.


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## skyline1

I used to work for a motor and generator manufacturer some years ago and that lever is indeed for altering the angle of the brushes with respect to the field slightly to maximize (or reduce) output.
as bobcjohn has explained
Large modern machines often have it too but it is preset by the manufacturer and doesn't need to be touched.

bobcjohn yes they do get more powerful as time goes on in fact self exciting machines have a small number of magnetic steel plates in the field poles along with the normal "soft" iron ones to maintain a little residual magnetism. this helps the machine "pick up" 

As the machine starts it acts as a primitive permag machine which produces a small voltage energising the field which then produces more voltage further energising the field and so on until it reaches full power

But this only happens when there is a little residual magnetism in the first place. This is probably what was happening with your machine it was remagnetising itself. Running it as a motor for a little while was exactly what we did on full size machines for exactly the same reason. It also "beds in" the brushes.

jasonb I love your little solenoid motor I might build something like it myself. It makes some nice sparks from the switches. This is due to the back EMF  from the solenoid coils as the magnetic field collapses. If you put your fingers across the coil while it is running you will probably actually feel them. They can be several hundred volts but with negligible energy unless it is a VERY large coil. (Attention Mr Tesla) 

These back EMFs might zap your USB power supply eventually though. The best way to deal with it is to put a reverse biased diode across the coil ( CATHODE to coil +ve NOT ANODE) a 1N5408 or similar would be ideal 
This will also prolong the life of your "switches" and they only cost pennies.

Best Regards Mark


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## TonyM

Has anyone tried contacting Danielasteam re the Edison.  She was a one woman band located not too far from me in the Czech republic. She was, and probably still is, working on the Prince of Wales loco in Darlington. https://www.thenorthernecho.co.uk/n...osts-girl-power-behind-darlington-loco-build/  I was interested in having some castings made. I am not sure if anyone has taken over her enterprise but I cannot get a response.


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## deverett

Tony 
Here's Daniela's email address:
Daniela Filová <[email protected]>

Dave
The Emerald Isle


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## deverett

Following on from bobcjohn's suggestion, I thought I would test the dynamo by trying to use it as a motor. 
First I checked the continuity from brush holder to brush holder.  Power switch open, open circuit; power switch closed 0 ohms.  All good so far.
I hooked up a 12v car battery charger and was very disappointed to see the amp. meter needle go off the clock (low power, 4 amps) and not a sign of movement of the rotor.  I tried the power lever from full ahead to full astern, but it made no difference.  Reversing the connections of the battery charger didn't help.
The circuit is such that from one brush holder, it goes through one column coil across the bridge then down through the other coil back to the second brush holder.  The coils are wound such that if they were placed one above the other, the windings would be continuous, not a reversed winding.  There are also some neodymium magnets in the bridge above the coils, again N down on one side and N up on the other.

Dave
The Emerald Isle


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## Jasonb

Dave I have this image saved and will be winding mine as per the lefthand illustration, windings in opposite direction.


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## deverett

Ahh so, JB.
Seems like my coil windings are wrong.  I got my (bum) info from the owner of the two full size ones shown.
I'm not going to do anything to it at least until after Doncaster.  Will need to get some more cotton covered wire to do a rewind.

Dave
The Emerald Isle


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## bobcjohn

Dave:
I'm sorry to hear your having trouble. I too had a hard time to get my dynamo running. I also experienced high current when running the dynamo as a motor. However after I gave it a helping spin, off she went and after a time the current came down. I think 4 amps is probably reasonable.

I don't know anything about magnetic theory, but I wound both of my coils in the same direction. It's like they are connected S/N to S/N, sort of in series. I look at the Bi-Pole arrangement like a horseshoe magnet.

I wonder, what is the purpose of neodymium magnets??

Wish I could be of more help.
Bob


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## peterl95124

I too have built an Edison Bipolar Dynamo, based on google images, and fun facts of electromagnetism from my college physics text. Its not quite as detailed as the awesome work displayed in this project, but you can see some photos at   http://www.baemclub.com/crkcallarchive/jan20nl.pdf

The armature was a replacement part for an electric drill from eBay, everything else is from bar-stock.  I designed the field coils for 12 volts at 1200 RPM, and hit the mark pretty well, I got about 11.7, not too shabby.
The dynamo built around a 1.5" diam armature is a good looking match for the 1.5" bore Stuart-9 I'm powering it with. 

If there's interest I will write up the equations for the field coil and have it added to the baemclub newsletter as a "tech topic".

Peter A Lawrence, San Jose, CA.


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## skyline1

Dave:

You probably don't need to do a complete rewind just reverse one pole with respect to the other and have another go. This would happen quite often in full size practice and when you are dealing with a four pole split compound machine with interpoles and compensating windings it can get pretty complicated. You can end up with different windings "fighting" each other and often at different parts of the RPM range. 

We had the occasional "runaway" through these sorts of effects.  Quite scary on a large machine, you need to be "quick on the breakers" to stop it damaging itself.

The neodymium magnets are probably to retain some residual magnetism as I mentioned previously. It might be worthwhile inverting one or both of these also to see what effect it has

Best Regards Mark


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## bluejets

Jasonb said:


> Dave I have this image saved and will be winding mine as per the lefthand illustration, windings in opposite direction.



The left and right diagrams are correct.
The centre diagram is incorrect.
Reason being one must have a north and a south pole.

Where the confusion came with the centre top illustration is, it is common to connect start of one winding to the finish of the next to reverse the poles.
This only applies where the winding was all done in the same direction.
It can clearly be seen this is not the case here.
Centre diagram has 2 north ( or 2 south )poles, depending on which way the current flows.
A tip for generators and motors is the right or left hand rule respectively.


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## peterl95124

I too have build an Edison Bipolar Dynamo so I can appreciate your work. I'll add that I recommend going to the trouble of removing those ball-bearings from the armature so you can make some more Edison-period looking bearings. FYI, I once had to use a slitting abrasive disk on a dremel to do that as sometimes they're a press fit.

To design mine I dusted off my college physics text book and did the math so that it puts out 12-volts at 1200 RPM.  anyone that wants to see how to do it just say so and I'll post the formulas here.

I've set mine up on a board with a Stuart No 9, the 1-1/2" bore is a good match for a 1-1/2" armature at least looks wise, and a cabinet with meters on the front and a light bulb in a socket on top.


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## William May

deverett said:


> JB.
> I'll try my 'artificial canvas' first and if not successful, I might try you r suggestion.
> Have you watched this video
> 
> Bob
> The lever on the bridge piece is the on/off switch.  The other (larger) one adjusts the phase (I think) but to be honest I don't have a clue!
> Come up and see it at Doncaster in May.
> 
> Dave
> The Emerald Isle



I think you are right about the phase adjustment. If you watch old movies of German U-Boats, the electric motor guys have handles that they move that seem to slide around the periphery of the electric motors, and I assume they are shifting the brushes from one setting to another. (Trading higher speed for lower torque perhaps, as the U-boat speeds up?) All I really know about electricity is what I learned putting a 9 volt battery on my tongue. The rest of it is a mystery to me.


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## Steamchick

Love it! - But don't put anything larger than 9V. on your tongue- or anywhere else for that matter. Electricity burns nerves and flesh - so can leave long lasting pain and disability (As people who sat in Electric chairs found out!). Remember, I think it was that "wonderful guy Eddison" who killed Elephants to demonstrate how "powerfully" electricity can kill - and to try and discredit that really clever guy Nicolai Tesla who promoted Alternating voltage and current. And didn't Eddison sell the Electric chair to the US government? - And it used "Tesla's AC", not his own DC.... I think?
What do you use for control of the field current to control the voltage? 40 years ago I converted a few motorcycle dynamos from 6V to 12V by the addition of a few coils to the voltage contacter of the Regulator, and a resistance in the field-coil circuit. Interesting simple devices. But modern electronics come "off-the shelf" at such cheap prices, that you don't seethe old electro-mechanical regulators any more. I think on WW2 ships and submarines it was all done by Manual-switching of the field - depending on load -to keep the voltage in the right range. (My grandfather was on the dynamos when "4th" on White Star ships during the first world war (- wish I could ask him....!). But post WW2 I'm sure voltage control went automatic.
Anyway: Perhaps like you, I would like to see something to explain DC motors and generators and how to determine the "lag" or "Lead" required for brushes? I have been thinking of replacing the Armature in my Unimat - SL 90W motor - that burnt-out when I ran it for more than the book allowance of 10 minutes. Anyone with clever ideas will be a help.
Biggest I worked on was the Dinorwig Power station - But I was on the design team for Busbars for the Starting circuits... so didn't ever get involved in Motor or Generator design. (And there are only brushes for the Excitation coils in the Dinorwig Motor-Generators as far as I understand).


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## skyline1

Yes indeed Edison wasn't entirely the "great guy" he seemed to be, in fact a bit of a commercial "shark" . He was willing to try to discredit the technically superior and much more efficient Tesla system by any means possible, including executing an elephant. He wanted to "prove" for commercial advantage that Tesla's A.C. was dangerous as it used much higher transmission voltages. In fact Edison's own  D.C. system used voltages that were also lethal, any high power distribution system is going to be dangerous due to the sheer amount of energy in it.

Tesla's polyphase A.C. system had many advantages and because transformers could be used to step voltages up and current down power could be transmitted over long distances with low losses (I²R). Edisons's system however, although limited by transmission distance could provide large amounts of torque at low RPM 
(theoretically zero) ideal for traction use.

As a result of these "dirty tricks" Edison became very wealthy and Tesla died in total poverty a broken man.

Today, High voltage A.C. transmission is almost universally used. and until fairly recently D.C. was used for high torque applications (like locomotives for example)

Many of Tesla's more exotic ideas that Edison (and others) thought fanciful or even impossible have actually become very useful today. 

Wireless Phone chargers and Switch Mode Power Supplies (which seem to be in everything nowadays) actually use Tesla's high frequency induction technique, as do induction cooking hobs.

Early "spark gap" radio transmitters so beloved of the likes of Marconi were nothing more than Tesla's famous induction coils with a large antenna attached

Steamchick you have probably guessed that I too am a great Tesla fan and could go on for hours about the man, but I will stop here before I bore the whole forum to death.

Best Regards Mark


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## Steamchick

Thanks Mark. I like your response - some new information form there. Here's another snippet - if my memory is correct from over 40 years ago... Dinorwig Power station Motor-generators were designed for an A.C. spec something like: 0.3Hz to 50 Hz. (3 Phase). 18Kv. nominal voltage: I think they are 135Mw per set - or something.... so LOADS of current for the torque to start pumping water UPHILL. There were a few operating modes: e.g.  Starting from zero to full speed in 3 minutes "in Air" (Blown-down water turbines) - or maybe this was in water, much quicker in air ... , but also starting with WATER in the turbines: They had starting (variable frequency) via a power supply, or by using another turbine generator from rest to synchro-speed connected to a pump, already wet, that was similarly run-up from Zero to Sychro-speed, when it was switched to pumping water up to the Top reservoir. I think this was the preferred way to start the pumps wet, only using the "electronic" variable frequency starter on the last of the 6 pumps after it had been used as the generator to start the first 5? The Electronic variable frequency starter was used mostly (I think?) to spin-up Generators "in-air" ready to supply electric demand at peak times - such as the half-time whistle in a football match of "coronation street" when everyone switches on their electric kettles for tea... When demand was needed all they did was open the water valves simultaneously and let the water generate... then turn off when demand dropped 2 minutes later! I would enjoy anyone else's experiences of how these things were operated.  Much more interactive than keeping a big compound steam engine pushing a large ship across oceans for days at a time, I would think? Sorry, I have prattled on too long...


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## deverett

When I wound the coils on my dynamo, I _Thought_ I had them wound like a horseshoe magnet as shown in Bluejets fig 1.  
There is only one layer of copper wire in the coils and the neo. magnets were to try and make up for the lack of coil layers.   The magnets were placed in the bridge N down on one side and N up on the other.  One possibility is that I put the magnets in the wrong way up/down!  Without stripping the dynamo down, I can't say now which side is up.  The cores and bridge are made from mild steel.
Other projects at the moment have put this on the back burner for now.

Dave
The Emerald Isle


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## Steamchick

Hi, a relatively quick check is with a compass needle. Check each item in turn. E.g.

Without magnets, 1 coil at a time (half the voltage you would use for the whole field). Be sure you apply the voltage the  correct way per coil.
The combined coils at your normal voltage.
1 magnet at a time, without any current in the field coils,
With it all assembled, no current in the coils.
Fully assembled and with the current applied to the coils.
The compass positioned in place of the armature should follow the field in the same direction for all conditions.
I think you'll pick-up any assembly glitch immediately by following this procedure. 
Thanks, I am enjoying this thread.


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## Shopgeezer

If I could borrow a time machine I would head back to Tesla’s era and whisper in his ear 1 cent, 1 cent.  George Westinghouse offered Tesla a fairly high license fee for each kw sent down the lines from Niagara Falls. The partners in the company complained about this and Westinghouse had to go back to Tesla several times to get the fee reduced. Finally in the greatest mistake of his life Tesla just gave the license to Westinghouse. No further payment. If he had just kept 1 cent per kw he would have been a rich man instead of living in poverty for the rest of his life.


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## Steamchick

Must remember that one.... A bit like the song "seven and a half cents" from the Pyjama Game? The most useful lessons come from everyday life....


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## ytrose2

I have been thinking of replacing the Armature in my Unimat - SL 90W motor - that burnt-out when I ran it for more than the book allowance of 10 minutes. Anyone with clever ideas will be a help.

[/QUOTE]
Last year I had a similar problem with my Unimat motor. After looking around, I finally made use of a sewing machine motor. However, I had to modify the wiring to make it rotate in the opposite direction, and machine the motor bracket to get the pulley in line, with new mounting holes. Good luck.


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## Steamchick

Thanks for that. I'll look further for something suitable.  I am currently using a old lawn mower motor, an open type with fan cooling - about twice the size of the correct SL motor. (I have t use a speed controller to get is slow enough for the SL! - and it sounds like it is "mis-firing" or stuttering most of the time at slower speeds.). But like you, it was wired to wrong way. It is VERY noisy, so I want to change it for something more user friendly. 
This thread interested me, because the motor I am now using did not have the brushes "at 90 degrees" to the alignment of the pole pieces. I suspect that the way it was wired was the opposite to the manufacturer's original - and I think I am now replicating the original - but I suspect there is some "phase angle" built-in to the armature, so when the brushes were originally swapped it didn't run very well. (It had been used on a small home-made bench grinder that I don't need). Therefore the person who made the small grinder rotated the brush holder to the optimum - which (I guess) is twice the phase angle (built-in to the armature) away from the original brush position. 
The Edison motor/generator seems to have some way of using a lever to rotate the brush holder around the axis of the commutator - like a manual "advance-retard" for the timing of the armature as it passes the pole pieces. I am interested to know (from anyone who knows DC Motors and generators, if there is a "lead" required to get the optimum magnetic field from the armature when armature aligns with the field in the poles. Would this "lead" be the same for a motor and generator? Or would it be a "lead" for the motor, and "lag" for the generator? Or does it swing a full 180 degrees to be used asa a reversing device? I think I can work it out, but don't want to write my own "Text-book", when someone has already done that.
Thanks for the posts. Most interesting!


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## Steamchick

peterl95124 said:


> I too have build an Edison Bipolar Dynamo so I can appreciate your work. I'll add that I recommend going to the trouble of removing those ball-bearings from the armature so you can make some more Edison-period looking bearings. FYI, I once had to use a slitting abrasive disk on a dremel to do that as sometimes they're a press fit.
> 
> To design mine I dusted off my college physics text book and did the math so that it puts out 12-volts at 1200 RPM.  anyone that wants to see how to do it just say so and I'll post the formulas here.
> 
> I've set mine up on a board with a Stuart No 9, the 1-1/2" bore is a good match for a 1-1/2" armature at least looks wise, and a cabinet with meters on the front and a light bulb in a socket on top.
> 
> View attachment 115533


Hi - I love what you have done here. It is in the right style for demonstrating the period of DC generation. Please can you explain the brush holder? - as I am "guessing" from what I can see in the photo? 
I assume the brush holder rotates around the axis of the armature, so is set such that when the current flows into a segment of the commutator, the poles of the armature are passing from the axis of the poles, towards where the "generating" segment of the armature leaves the poles? I'E. for a particular pair of armature poles, they enter the magnetic field of the poles, and "reluctantly" build up an EMF as the rotation cuts the lines of flux until they reach a maximum EMF - at which point the brushes align and "discharge" the magnetic flux by drawing out the electric current and "de-magnetising" to segments of the armature? 
If the poles do rotate around the axis of the generator, have you rotated the brush holder to a "maximum" point where the generator is matched to the speed at which you run the generator? I have figured-out that this angle of "lag" may need to vary to get the optimum for any particular speed? - But my reasoning may be completely cock-eyed! I would like to hear more about this from your experience. 
It strikes me that if the brush holder is at the wrong phase angle for the speed and "phasing of the armature windings", then the generator will be "poor" (low current, even if the voltage is OK). - This could be the problem with poor generation after the resolution of any "field and winding issues.
But thinking a bit further: Generator problems may be as simple as "not enough speed" - to develop the voltage. The current will then depend on the ability to maintain that speed and voltage against the load by an adequate current in the field coils - up the the safe limit (which is usually the temperature inside the windings, which, if too hot, causes catastrophic breakdown of insulation, shorting and burn-out of the windings). The "rating" of the insulated wire is "in free air" - not when buried inside a hot coil - so PLEASE watch the field coil temperature. Too "Hot to the touch" is over about 55 degrees and the current needs to be turned-down. (Windings inside th coils will be hotter than on the outside!). If there is insufficient field for the generator at a "comfortable warm" then you simply need lots more windings to get more magnetic field into the generator. - And possibly more neodymium magnets to get it started? The design problem of too many Neodymium magnets is that you can't regulate the generator "down" as low as may be necessary. The remanent magnetism is a "minimum"  - which needs to be high enough to start the generation, but low enough the generator isn't doing too much at low load. - The consequence is that the voltage will be too high, so you need to slow the generator.  The current in the field coils is simply increasing the field from the "neodymium" minimum to the max that you can get at the field-coil current limit. Check the WWW as I am sure there will be a text book to explain it better than I can( - as a total amateur!).
Another comment: If there is no "initial remanence" of magnetic field in the Pole arrangement, then the generator cannot generate. (A car alternator is initially excited by a small current from the controller until it "kicks-in" - Years ago this was the main purpose of the "warning light" circuit!). I think the neodymium magnets are built-in to the pole assembly to achieve an initial remanent magnetic field for the generator to start. When running, the field needs to be controlled to keep the generator at the correct voltage for the speed and load.


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## peterl95124

Steamchick, lots of good questions, lets see if I can answer any of them, starting with the most interesting.

if you replaced the armature's commutator with a series of rings arranged axially, with each separate winding in the armature connected to its own ring(s), and then placed separate brushes one for each ring, so in the end instead of having two brushes you had say 20 brushes, and then if you had a 20-input oscilloscope you would see 20 AC sine-waves, each one at a different phase. But an Edison Dynamo puts out DC ?. Aha, that's the right question. What the commutator does is select the one winding that is at its peak AC voltage, and as the armature turns and that winding's voltage is going down the brushes switch over to the next winding whose voltage is about to peak. etc. etc. etc.  The brushes are adjustable because you have to find that peak by trial and error. The peak occurs when the winding is passing through the maximum magnetic field flux, which is typically at the center of the pole pieces, but you don't know which commutator pieces the winding that's nearest to the pole centers is connected to. As you can see in the photo the commutator in my armature is connected such that the brushes are vertical while the poles are horizontal, that's 90-degrees away from how the commutators were wired in Edison's time, but I can't do anything about that, so mine looks a little weird if you know what to look for.  Notice that the word "lag" doesn't appear in this description, only "peak", which by the way is independent of both speed and load, IE there are no analogies with IC engines.

My dynamo has no magnets, I first run it as a motor from a battery or DC power supply and (if I don't disassemble it) there's enough residual magnetism in the steel to get it started (self excited) as a dynamo after that.  The nice thing about not having magnets is you find out if its wired correctly when you try to run it as a motor. If the field coils are wired backwards they cancel each other's magnetism and you end up with effectively no field, and if you connect the brushes to the field backwards, again the field is reversed compared to what the armature requires. These are the two ways in which the wiring can be incorrect, which can be difficult to diagnose, and made worse if you're using magnets in addition to coils. That and the fact that magnetic alloys didn't exist in Edison's time mean to be period faithful you shouldn't use magnets if you're designing from scratch.

The output voltage of generators with magnets is linearly proportional to speed, but with field coils is quadratic with speed, IE with magnets double the speed and that doubles the voltage but with field coils double the speed and that quadruples the voltage. This is because with magnets the field flux is constant, but with coils the field strength keeps going up with speed, and the voltage is proportional to the product of speed times field strength ("Faraday's law of induction").  Hence voltage regulators are required in automobile generators and alternators and what they control is the current in the field.

The current in the field coils (if they are producing the field flux alone without magnets) is limited by their resistance, and is typically an order of magnitude or more higher than the armature resistance as the field coils are usually made with hundreds to thousands of turns while the armature has tens of turns. This is done because current in the field coils is lost power so they are intentionally made with as many turns and as much resistance as possible to reduce lost power. This also means the armature will burn up way before the field coils do if you let too much current through them (load resistance is too low).

well, I think that's enough for one post, hope that helps, additional questions welcome,
Pete.


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## skyline1

peteri95124

Wonderful, simple explanation of what is quite a complex subject if you go into it in any detail, well done.

I have worked on large rotating machines both A.C. and D.C. mostly military stuff but also traction motors. But this was a very long time ago and it is nice to have one's memory refreshed by someone who knows what he's talking about.

Best Regards Mark


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## Steamchick

I plan to convert a bicycle wheel-hub generator into a generator for a model steam engine. (an old - but working - Sturmey Archer 6v 1A unit). Has anyone done this - and made plans - before I attempt to re-invent the "


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## skyline1

I think it is possible to do it but IIRC these are actually small brushless permag alternators, the old "rub on the tyre" type certainly were. You could use some electronics to turn it into D.C. though. I have designed a regulator for doing this sort of thing for use on my steam turbines. It would simply need a small bridge rectifier in front of it I'll PM you the circuit and PCB layout if you are interested it uses very common and easily available components.

The regulator unit itself forms the basis of a miniature switch board with real working little knife switches, working rheostats and indicator lights.

despite being solid state internally it looks very period and using the knife switches and regulators to control the loads is great fun.

Best Regards Mark


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## Steamchick

Thanks Mark. Sounds good. I was simply going to slap the output through a bridge rectifier and see what volts and current are available. This is a 6v 1 AC unit at Wheel speed for 10 mph. From what I have read... It is a permanent magnet rotor around the outside of the stator, so the "hard-task" will be making a "simulated wheel axle" and drive from the  steam engine. But the fun is working out the solutions to the hard-tasks. The circuit diagram will be a help as I don't  know about voltage control after the power is generated... when you can't control the excitation.
Thanks,


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## Steamchick

I found the "round tuit" - I have started making the "Whizzing magnet" generator. A very simple design so nothing to talk about - just needs a bit of time applied at the lathe...
But I have a question about the Edison DC generator. Are the field coils in series or parallel with the armature? Back in the 1970s I was converting motorcycle generators on engines that had 6V DC generators (Lucas, Wipac, Eastern European of East German and Czech bikes, etc.), as well as those with 6V alternators, to give a 12V controlled DC output, using a bulb to give me the resistance I needed in series with the field coils to avoid cooking the field coils, and I re-wired the electro-mechanical regulators for a 12v armature output. - I am pretty sure I remember the fields being in parallel with the armatures - via the regulator. I also bought a "transistorised regulator and 12V DC conversion" for 1 bike, before I started converting the PAL and other  regulators. 
But I now have some electric drill (mains) brush motors, which have the field coils in series with the armature - presumably as the motors run from AC and "rectify" by the field switching in phase with the armature? I have wondered, if I can re-wire one of these to act as a generator (directly driven from a steam turbine perhaps?) by setting the field coils in parallel with the armature and fitting a regulator - as per the pre-1970 vehicles? I am aware that there are a variety of configurations for winding armatures, and note that the brushes often cover more than 1 pair of commutator contacts at any time (copper strips much narrower than the brush width)...  I wonder if I would have to rotate the brush alignment from the motor application? - Or would it require the generator to run in the opposite direction to the direction i was designed to run at as a motor? I'm sure someone has done this and has the answers to save me re-developing the solution. - Thanks.


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## skyline1

Older electric drill motors and many domestic appliance motors are what are called "universal" or AC/DC type. They are series wound D.C. machines that can be run on A.C. as the field polarity changes in sync with the armature polarity as you have pointed out. This actually applies to many D.C. machines. 

They are fairly compact and powerful and above all cheap to produce. (we are back to that old chestnut again, economics) but they have several disadvantages.

They usually need to run at high speed which makes them noisy (very noisy sometimes) and entails a reduction gearbox to give higher torque and lower speed.

They have a high brush wear rate and a tendency to "eat" their commutators if the brushes get worn. You see many old drills still going but "sparking at the comm" in a most alarming manner. 

They can produce large amounts of Radio Frequency Interference (RFI) and need to be well suppressed (Ask any Sound Engineer or Radio Amateur)

But even with their shortcomings they are pretty reliable and rugged and we have been using them for years in all manner of applications. 
Speed control can be arranged by using simple SCR phase control (basically a ruggedised light dimmer)

Recently however there has been a trend towards using "brushless D.C.  or Digital motors" in these applications, This is a slight bending of the truth as there is no such thing as a true brushless D.C. machine. What they actually are, is a miniaturized 3 phase A.C. machine coupled to an equally miniaturized Variable Frequency Solid State Drive, No Mr Dyson you didn't invent it Tesla did many years ago.

Using one of these "universals" as a generator might be possible but there are several snags 

I suggest you go with them "as is " putting the existing field winding in parallel instead of series would not work as it's resistance is far too low it would simply use most of your power turn it into heat and probably burn out the armature winding. designing a new field with more turns but thinner gauge wire is beyond my ability I'm afraid but other members with more knowledge (and superior maths skills) might like to have a go at it.

They are pretty powerful in the order of several hundred watts, so you would need a big turbine to drive them and the efficiency (or lack of)  of a single stage De Laval or Stumpf Like I use would mean a big fuel and water guzzling boiler. A small scale multistage like a Parsons type would give you the efficiency but the complexity of design and construction probably make it impossible (and expensive)

But "Doing the Impossible" is a theme here and judging from the Merlins, V8s and Radials some have built, someone is likely to likely to have a crack at it.
The model jet chaps would have the required expertise and equipment for example.

Best Regards Mark


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## Steamchick

Thanks again Mark for another bit of clear thinking, and advice. 
That helps me get on the lines of what to study, and consider for re-engineering one of these motors as a generator. I now realise I need to check-out the motor, to understand the field resistance and armature resistance. Then consider the limitations of a generator for the speed I expect to be able to drive it at. As well as the max permissable current in both armature and field coils. I reckon I can check it simply with my AVG meter, but also check voltage drop across the field coils and armature when I drop 12v DC from a car battery across the motor "as it is". I suspect I'll get into calculations comparing the impedance at 50Hz (As the motor is rated for 240V, 50Hz.) with the resistance at DC.... but, here is the nitty-gritty... do I need to consider the impedance of the armature at rated speed for the effective "AC" I each windings it is energised then de-energised as it passes through the magnetic field when I use it as a generator?
One of the contributors to the Edison Generator thread has used an armature from a electric motor, and wound the field coils for the Edison dynamo. So what speed is it running at to use in this application, what resistance of armature, and how many turns and what wire make the field coils, and what are the relative currents in field coils and armature when running? - Please forgive all the questions, and I think the design was yours but I haven't got that bit of thread to know the author.
The thing is, I suspect the Electric drill motor that I am considering converting, may be limited by current simply because running at AC the field coil and armature impedance (inductance) is the current limiting factor, not the resistive element alone. So supposing it was run on DC, at the same voltage as RS mains, I may expect it to burn-out from overheating as the energy of oscillating the magnetic field isn't there with DC to limit the current...? Or have I got my ideas "out-of-phase"? I'll start looking at the motor and try doing the sums, then let you know my conclusions - then I may consult Maxwell 
(James, the one who wrote the text books!), although I last read his books 45 years ago... But Tesla understood Maxwell.
Regards,


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## Steamchick

Flippin' spell checker again! AVG should be A V O, it manages "nitty-gritty" but not "Tesla"! - and "Edinburgh son" or "Editor" for Edison? Makes me wonder....


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## skyline1

Ah James Clerk Maxwell (1831 - 1879) James Clerk Maxwell - Wikipedia another misunderstood and under appreciated genius.

(oops I can feel another rant coming on so back to dynamos)

Yes rotating machine design whilst the basic principles are simple can get very complex, very quickly. So before you go completely potty and start quoting Maxwell's Equations to your therapist I think I may have a cheap and almost ready made solution,

What about the armature from a cordless drill they are D.C. and rated for about the right voltage and current you need. 
They are very rugged in fact almost indestructible. (they need to be in a machine that has to withstand regular overloads and even complete stalls).
The best bit is they are likely to be cheap or even free as people often chuck out usable cordless drills because the battery or charger has died or is too expensive to replace. The field assembly and brushgear from the existing miniature Edison that quite a few have built should match quite nicely with one of these.

Meanwhile it will be interesting to see how your Duplex "whizzy magnet" machine develops keep us posted on how it's going.

Best Regards Mark


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## awake

Luckygen1001 on YouTube has quite a few videos on converting motors into generators - might be helpful?


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## Richard Hed

Steamchick said:


> Thanks again Mark for another bit of clear thinking, and advice.
> That helps me get on the lines of what to study, and consider for re-engineering one of these motors as a generator. I now realise I need to check-out the motor, to understand the field resistance and armature resistance. Then consider the limitations of a generator for the speed I expect to be able to drive it at. As well as the max permissable current in both armature and field coils. I reckon I can check it simply with my AVG meter, but also check voltage drop across the field coils and armature when I drop 12v DC from a car battery across the motor "as it is". I suspect I'll get into calculations comparing the impedance at 50Hz (As the motor is rated for 240V, 50Hz.) with the resistance at DC.... but, here is the nitty-gritty... do I need to consider the impedance of the armature at rated speed for the effective "AC" I each windings it is energised then de-energised as it passes through the magnetic field when I use it as a generator?
> One of the contributors to the Edison Generator thread has used an armature from a electric motor, and wound the field coils for the Edison dynamo. So what speed is it running at to use in this application, what resistance of armature, and how many turns and what wire make the field coils, and what are the relative currents in field coils and armature when running? - Please forgive all the questions, and I think the design was yours but I haven't got that bit of thread to know the author.
> The thing is, I suspect the Electric drill motor that I am considering converting, may be limited by current simply because running at AC the field coil and armature impedance (inductance) is the current limiting factor, not the resistive element alone. So supposing it was run on DC, at the same voltage as RS mains, I may expect it to burn-out from overheating as the energy of oscillating the magnetic field isn't there with DC to limit the current...? Or have I got my ideas "out-of-phase"? I'll start looking at the motor and try doing the sums, then let you know my conclusions - then I may consult Maxwell
> (James, the one who wrote the text books!), although I last read his books 45 years ago... But Tesla understood Maxwell.
> Regards,


Just so you know, Oliver Heavyside is the guy who really is responsible for "Maxwell's" Equations (that is the ones about what light is)--Maxwell had 20 equations which Heavyside reduced to the four now known as "Maxwell's Equations".  Really, they should be known as the Heavyside-Maxwell equations.  Anyway, Heavyside was an underknown, under-acknowledged, unappreciated genius of the electric age.  His stuff is in magazines all over the place, particularly in one magazine (don't remember which, but am sure it has the word "electric" or some derivation of that in it) which he wrote for.  Look up Heaviside (sp?), he has very much of what you might be looking for.


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## skyline1

Yes quite so he reduced Maxwell's correct but rather long winded ideas to something more manageable among his other many accomplishments including research into Characteristic Impedance leading to the development (and patenting) of the coaxial cable.

I think Europeans and the British in particular have a tendancy towards science as an end in itself whereas Americans are more open to the commercial and practical applications of ideas, which may explain why many European scientists tend to be less well known.

Best Regards Mark


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## Richard Hed

skyline1 said:


> Yes quite so he reduced Maxwell's correct but rather long winded ideas to something more manageable among his other many accomplishments including research into Characteristic Impedance leading to the development (and patenting) of the coaxial cable.
> 
> I think Europeans and the British in particular have a tendancy towards science as an end in itself whereas Americans are more open to the commercial and practical applications of ideas, which may explain why many European scientists tend to be less well known.
> 
> Best Regards Mark


It just irritates the heckout of me when I read "Maxwell's" equations, when realistically, they are WHOLLY Heavisides.  He did derive them from Maxwell, but still they are NOT Maxwell's equations!  Incidentally, did you know Heaviside is the REAL inventor of radio?  He demonstrated in 1888 (I believe) that he could transmit a signal from one side of a room to the other.  Then he quit.  That was enough and very few peeps knew about this.  Yes, as you say, he failed to exploit this for commercial purposes.  Heaviside is a real hero and he should be better known.  I thimk I downloaded a bundle of his magazine articles.  But trying to find them might be a difficulty.  They are freely available if you know where to look.


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## Steamchick

Hi Richard, I apologise for quoting Maxwell instead of Heavyside... I have not heard o Heavyside, so again this blog has taught me something more than school. The reason I consult Maxwell, is the text book Ho wrote, I have my Grandfather's copy from his schooling, dated 1890 somthing. Maxwell made fame amongst his peers, FRS, University top-dog, etc. And was (is?) Used as the text book since he wrote it until at least 1980s in the UK. But there are many clashes of ownership of ideas, and mostly the richer people with better (more business) sponsors won the accolades. Just look at what Edison did for Tesla, Bell, Swan, et al. And James Watt, versus Trevethick, Newcomen, & co. Nuff said. Back to spinning magnets!
K


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## Richard Hed

Steamchick said:


> Hi Richard, I apologise for quoting Maxwell instead of Heavyside... I have not heard o Heavyside, so again this blog has taught me something more than school. The reason I consult Maxwell, is the text book Ho wrote, I have my Grandfather's copy from his schooling, dated 1890 somthing. Maxwell made fame amongst his peers, FRS, University top-dog, etc. And was (is?) Used as the text book since he wrote it until at least 1980s in the UK. But there are many clashes of ownership of ideas, and mostly the richer people with better (more business) sponsors won the accolades. Just look at what Edison did for Tesla, Bell, Swan, et al. And James Watt, versus Trevethick, Newcomen, & co. Nuff said. Back to spinning magnets!
> K


I wasn't criticising you, it's just that Maxwell certainly deserves the credit for the work he did on light, but even so, in all the books, those four equations are given as "Maxwell's Equations" when indeed, they are NOT!  This is in ALL the books I have ever seen.  I thot they were Maxwells equations till I discovered that they were Heavisides stuff.  I was reading some of Heaviside's writing when he told how he came up with them.  No one in their right mind would bother with maxwells original 20 equations when they could use Heaviside's simple 4 equations (in various forms too).

What I thimk is more important is to learn about Heaviside and his very important contributions to electrical thot and function.  He was very much like Tesla except without being very well known at this time.  He was better known 100 years ago.  He also made some important discoveries in Calculus in which the mathematicians complained that he had not "proved" what he was doing (only used it in electrical calculations).  Later, some mathematician "proved" it.


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## Steamchick

I think of the simple Phase "Standing on the shoulders of Giants"... Well, we all are... Modern Technology comes from a collective of the incredible thoughts of mankind... "Never in the History of Man can we say we owe so much to so few.." - to quote another giant.
I consider the length of the "stone age". "Bronze age", "Iron Age". .... modern "iron and steam age", "Electrical (power) age". electrical "Communication age", "Aeronautic age", "Oil (materials) age", "Nuclear age".... etc.... We are even communicating globally via the electrical "Communication age" - which is a veritable "Tower of Babel"! - Started by Tommy Flowers....? - Or was it started by the German teleprinter engineer who invented the Lorenz machine? So where next? And how fast will we learn to live within new ages? - I'll get back to the fundamental building block of whizzing magnets! - And I can do most of it without even reading Heaviside's and Maxwell's equations... But they will solve some problems before I "cut-metal". - So maybe that is the "Beautiful lesson" for today? - "Brain work" can save a lot of wasted "workshop time"! - Oh... I may have started a new debate....


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## Steamchick

Hi Mark,
I have learned from Utube videos that the series brush motors will generate DC when spun in the correct direction (still getting my head around that one?) - and anything up to normal running speed (thousands of RPM!). They need a load (resistance /conductance) to close the circuit and the EMF developed across the Armature then drops volts - Through brush resistance, field coil resistance (not impedance as DC is being used), then load resistance (conductance). As the resistance of the total circuit drops (limited by load being short-circuited and all the load seen by the armature is the internal resistance of the whole motor/generator) then the current increases - so power output increases as the load gets bigger - up to the limit. But re-wiring with Field coils driven by a regulator will simply make a "traditional" dynamo - which I think is the direction I may try first. I have learned that the application of AC to these motors is limited significantly by the AC frequency across an inductance: I.E. the impedance. Therefore as a DC machine (especially with Parallel field coils) they have completely different properties to there designed use as "AC. High speed" motors.
Thanks everyone for the tips!
Ken


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## Richard Hed

Steamchick said:


> I think of the simple Phase "Standing on the shoulders of Giants"... Well, we all are... Modern Technology comes from a collective of the incredible thoughts of mankind... "Never in the History of Man can we say we owe so much to so few.." - to quote another giant.
> I consider the length of the "stone age". "Bronze age", "Iron Age". .... modern "iron and steam age", "Electrical (power) age". electrical "Communication age", "Aeronautic age", "Oil (materials) age", "Nuclear age".... etc.... We are even communicating globally via the electrical "Communication age" - which is a veritable "Tower of Babel"! - Started by Tommy Flowers....? - Or was it started by the German teleprinter engineer who invented the Lorenz machine? So where next? And how fast will we learn to live within new ages? - I'll get back to the fundamental building block of whizzing magnets! - And I can do most of it without even reading Heaviside's and Maxwell's equations... But they will solve some problems before I "cut-metal". - So maybe that is the "Beautiful lesson" for today? - "Brain work" can save a lot of wasted "workshop time"! - Oh... I may have started a new debate....


That's perfectly all right.  It's better to thimk than be a couch potato.  It's better to have some ambition than be a dead beat, 'cause dead beats just expect a handout.  My son talks about what you have mentioned above and he says that the discoveries of fire, copper, bronze and all those other slowly developed inventions/discoveries are worth billions in todays dollars.  Those discoveries were all necessary for us to have the civilization we have today.  The single most un-appreciated chunk of technology we have today is Sewers!  They are hidden below the street, they save us from cholera, typhus, stink and who knows what else?  And yes, reading a few articles can save us lots of time.  That's also why we have this and other forums.  It's like some of us know one sector and others know another. 

BTW, I managed to cut some internal threads today on my crappy enco lathe.  I had to build a hand wheel to do it and turn the thing by hand because the enco could not go slow enough for me to stop it at the end of the threads.  It was a great pleasure to do this.  Am starting another, identical set of threads tomorrow.  These are for the internal threads to an ER-25 and 11 collets using a 1-1/2" X8tpi spindle nose.  Also, I had to grind a 60deg thread cutter out of carbide which wasn't so bad and then to silver solder it to a holder.  That is the first time I ever did silver solder and didn't have much hope for it to hold together (experience with mere lead solder), but it held very well and workt just fine.  Very happy about that.


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## awake

One of the things I have found most fascinating, when I have visited archaeological sites in Greece and Turkey, is the fact that cities they had systems for dealing with water and waste - 2000 years ago and more. When you think about it, you really can't have a city without some way to handle at least the water issue. You _could_ have privies out back for the waste, as was true in many a western city up until relatively recently (recently in the time scale we are talking about) - but in these 2000 year old cities, they had _indoor_ toilets, with water washing through them to clean them out. I also saw a village on Thera (Santorini) that was covered by volcanic ash and preserved more than 3000 years ago - and in one of the houses, on the second floor, there was an indoor toilet - though I couldn't see how the waste was handled. All this time, I had thought the invention of indoor plumbing was a modern miracle ... apparently not!


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## awake

Richard Hed said:


> Also, I had to grind a 60deg thread cutter out of carbide which wasn't so bad and then to silver solder it to a holder.  That is the first time I ever did silver solder and didn't have much hope for it to hold together (experience with mere lead solder), but it held very well and workt just fine.  Very happy about that.



Richard, out of curiosity, why did you grind the thread cutter out of carbide instead of HSS? Were you threading particularly hard material?


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## Richard Hed

awake said:


> Richard, out of curiosity, why did you grind the thread cutter out of carbide instead of HSS? Were you threading particularly hard material?


Probably because I don't know any better.  I also have tons of carbides that have no holders.  I wanted to test out the silver soldering--never done it before--works great.  The material I am cutting is hydraulic piston rods--don't know the exact stuff.  Do you suggest I should try silver soldering HSS?  I suppose I could use a HSS in a boring bar of some sort--there is a hole all the way thru the part.


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## awake

Hmm, hydraulic piston rods are likely to be hard on the outside; not sure if they are hardened through. And I apologize - I missed the fact that you were doing internal threads. I was thinking of how much easier it would be to grind an _external_ threading tool from an ordinary HSS blank. You _can_ grind an internal threading tool from an HSS blank, all in one piece - I have done it, successfully, but it is a persnickety process. Silver soldering a bit ground to 60° onto a bar is going to be way easier and less error prone. And if you are going to sliver solder the bit in place, then the only reasons to go with HSS rather than carbide would be if you don't have carbide handy or don't have the means to grind it easily - sounds like neither of those apply in your situation. Carry on!


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## Richard Hed

awake said:


> Hmm, hydraulic piston rods are likely to be hard on the outside; not sure if they are hardened through. And I apologize - I missed the fact that you were doing internal threads. I was thinking of how much easier it would be to grind an _external_ threading tool from an ordinary HSS blank. You _can_ grind an internal threading tool from an HSS blank, all in one piece - I have done it, successfully, but it is a persnickety process. Silver soldering a bit ground to 60° onto a bar is going to be way easier and less error prone. And if you are going to sliver solder the bit in place, then the only reasons to go with HSS rather than carbide would be if you don't have carbide handy or don't have the means to grind it easily - sounds like neither of those apply in your situation. Carry on!


I have limited tools, green stone for grinding the carbide, will attempt to buy a diamond grinder this year, but always the factor of limited funds.  Anyway, I am in the process of making tools to make the tools for making the parts.  I have known for many years that that is what a machinist is, a person who makes tools for making parts, often a tool to be used exactly once!  Hopefully to be used often.   So am making ER for quickly being able to change parts out and be accurate in doing so.  (As opposed to fiddling with the 4-jaw).  It's very much fun and satisfying but slow too.


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## Steamchick

And I thought the Romans had invented city plumbing.... but I do remember that Ephesus and Siraceus had ancient plumbing, so I wasn't paying attention properly.... 
On Internal threads -In blind holes: If the lathe will run backwards, you can make the tooling "up-side down", and working on the back surface of the hole,  start at the bottom of the hole and work the tool out (as if un-screwing  the to from the job). This is contrary to the loading of the taper slides on the lathe, but if the slides have correctly set gib-strips then the slack will be negligible and you'll find it will work if not overloaded. Also, when cutting threads, consider cut in on one face only. Set the top cross-slide around 60 degrees, so the tool progresses along one face of the thread and only cuts the second face - make this the leading face for the direction of feed. Then the tool can have correct relief of cutting angles, and not bind or chatter when working hard or difficult materials. The set-up takes time but the reward is the finished job. Enjoy!


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## Steamchick

Sorry, got my head screwed-on the wrong way today. If working at the front and with lathe running backwards, the tool needs to be upside-down, or if working on the back face needs to be a back-to-front (opposite hand) boring bar. But you'll work it out anyway, I'm sure!


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## Richard Hed

skyline1 said:


> Yes quite so he reduced Maxwell's correct but rather long winded ideas to something more manageable among his other many accomplishments including research into Characteristic Impedance leading to the development (and patenting) of the coaxial cable.
> 
> I think Europeans and the British in particular have a tendancy towards science as an end in itself whereas Americans are more open to the commercial and practical applications of ideas, which may explain why many European scientists tend to be less well known.
> 
> Best Regards Mark


Yes, I thimk Heaviside is responsible for some of the important work on impedance.


----------



## Richard Hed

Steamchick said:


> Sorry, got my head screwed-on the wrong way today. If working at the front and with lathe running backwards, the tool needs to be upside-down, or if working on the back face needs to be a back-to-front (opposite hand) boring bar. But you'll work it out anyway, I'm sure!


That's one of the problems with a crappy enco==yes, it has a reverse switch, but I wouldn't call it "reverse", that is, what we would expect if we wanted to make LH threads.  I can't slow it down to a manageable speed to turn off the switch, as I can't disengage the thread nut--it will lose it's place no matter what I try--it is a total peice of (Be nice)  BLEEP.  So my solution was to make a wheel to work the spindle by hand.  It works just fine, have to back out the cutter by hand but it is very slow process.


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## Steamchick

Hi Mark, on Turbines... I have been considering shaft speeds and loads of various options for driving engines.... directly, rather than with gearboxes. I have a Stuart and Turner  Sun engine - good for 20 00pm - but needs a reliable oiling system to counter crank journal wear. I made it 20 years ago for a launch, but it was just too heavy for the hull. The boiler is quite big....  so I changed to the smaller Star engine. But as I have not found a suitable generator for 1000 - 2000rpm, (maybe I should make an Edison generator?), my mind has wandered to thoughts of a turbine for 10,000 rpm.... but maybe that's too slow for a Tesla model turbine... I have seen turbines for model sizes going 10 times faster... and need special bearings and lubrication to cope! Not my game. But as I have a field coil from a burnt-out drill, maybe I could make a rotating permanent magnet armature and use it at "Model Steam engine speed" as a 2-pole alternator? Or maybe just converting my good brush motor to a dynamo with regulated field is the simple option? Choices! Back to the calculator to match desires and expectations....


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## Richard Hed

skyline1 said:


> Ah James Clerk Maxwell (1831 - 1879) James Clerk Maxwell - Wikipedia another misunderstood and under appreciated genius.
> 
> (oops I can feel another rant coming on so back to dynamos)
> 
> Yes rotating machine design whilst the basic principles are simple can get very complex, very quickly. So before you go completely potty and start quoting Maxwell's Equations to your therapist I think I may have a cheap and almost ready made solution,
> 
> What about the armature from a cordless drill they are D.C. and rated for about the right voltage and current you need.
> They are very rugged in fact almost indestructible. (they need to be in a machine that has to withstand regular overloads and even complete stalls).
> The best bit is they are likely to be cheap or even free as people often chuck out usable cordless drills because the battery or charger has died or is too expensive to replace. The field assembly and brushgear from the existing miniature Edison that quite a few have built should match quite nicely with one of these.
> 
> Meanwhile it will be interesting to see how your Duplex "whizzy magnet" machine develops keep us posted on how it's going.
> 
> Best Regards Mark


I'll have to remember to tell my therapist about Heaviside and Maxwell, Thanx for the tip. LOL


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## Steamchick

The brush motor in question as a total resistance of 98ohms, (38 ohm armature). So at 240V it could draw 2.4A.  But it only takes 0.75 at 50Hz. - obviously due to the added impedance from the inductance. So should I expect the same motor performance if I ran this motor at 75 DC?  - Or would the impedance of the Armature - switching coils at 183Hz. - reduce the current and performance? I can imagine there will be a DC portion running in the field coils, with a ripple from the Armature switching coils. So perhaps I need a text book on DC motor design, now? Or am I thinking too hard?


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## skyline1

The reason your motor draws less current than it's D.C. resistance would suggest is due to back EMF.
At a standstill the supply only "sees" the D.C. resistance plus a little due to the inductance of the windings so it WILL draw about 2.4 Amps but as the speed increases it will produce Back EMF according to Lenz's law Lenz's law - Wikipedia so that at running speed it only draws 0.75 amps

The ratio of starting current to running current is about 3.2:1 which is probably about right for this motor although some machines can have a starting current of 10 times  their running current or more

Starting Current is a big problem on large machines and is the reason for Star Delta and wound rotor resistance starting. More recently electronic soft starts are used.

I think you may be concentrating on winding impedance and not considering the Back E.M.F. which has a far greater effect

If you are thinking of going the turbine route my little DeLaval's run at about 30,,000 R.P.M. and produce about 4 Watts at 12 Volts Ish using small permag motors like you get in electric toys I have quite a collection of them of various shapes and sizes (Somewhere amongst my other junk).

This Is quite a modest speed by turbine standards. The model jet chaps are running at  80,000 R.P.M plus. But even at this speed they do eat bearings I have to change them fairly regularly. (about every 50 Hours or so) I might change them for Ceramic ones at some later date they are available in these small sizes but they are very expensive.

If you decide to build a little permag alternator I suggest you go for a 4 pole rather than a 2 Pole as this will keep the speed requirement down synchronous speed for a 4 pole machine is 1500 R.P.M. at 50Hz as against 3000 R.P.M. for a 2 pole.

Decisions, Decisions It's a real Pandoras Box this mini generator caper as I'm sure you are finding out. Experimentation is the name of the game as much as science in small scale as effects that can be largely ignored in larger scales have a much greater effect the smaller you go.


Best Regards Mark


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## Steamchick

Thanks Mark. More useful advice there!


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## L98fiero

Richard Hed said:


> I can't disengage the thread nut--it will lose it's place no matter what I try


If that's the case, it may have a metric leadscrew and then, you can't disengage the halfnuts.


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## gunner312

It's not necesarily true, you can disengage the half nuts when threading metric with imperial screws. it's all in the method.
I do it all the time and don't find it a problem. If you have a metric screw, then threading metric is normal operation. What I think is the problem is that you must engage on the even numbers if the pitch is an even number (2,4,6,12,24, etc) and on odd numbers (3,5,7,13,etc) when the pitch is an odd number. When the pitch is an even number, you should be able to engage on any number of the thread indicator but some lathes I have found will work better when you engage on the even numbers for an even pitch number and odd for odd etc. also you must change the drive gears to compensate for the difference between inch (imperial) and metric lead screws. If you don't do this then even engaging on the correct numbers won't work.



L98fiero said:


> If that's the case, it may have a metric leadscrew and then, you can't disengage the halfnuts.


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## Steamchick

If you decide to build a little permag alternator I suggest you go for a 4 pole rather than a 2 Pole as this will keep the speed requirement down synchronous speed for a 4 pole machine is 1500 R.P.M. at 50Hz as against 3000 R.P.M. for a 2 pole.
Best Regards Mark
[/QUOTE]
Hi Mark, I am thinking of driving the generator for 12V or 24V DC - so would be doing simple rectification of the AC from a spinning magnet alternator - then manage the DC voltage with a Buck controller - and just lighting some bulbs or LEDs. As I have a few Boilers and Steam engines, I am not even sure which combination I shall match to a generator - when I get that elusive Round Tuit!


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## L98fiero

gunner312 said:


> It's not necesarily true, you can disengage the half nuts when threading metric with imperial screws. it's all in the method.
> I do it all the time and don't find it a problem. If you have a metric screw, then threading metric is normal operation. What I think is the problem is that you must engage on the even numbers if the pitch is an even number (2,4,6,12,24, etc) and on odd numbers (3,5,7,13,etc) when the pitch is an odd number. When the pitch is an even number, you should be able to engage on any number of the thread indicator but some lathes I have found will work better when you engage on the even numbers for an even pitch number and odd for odd etc. also you must change the drive gears to compensate for the difference between inch (imperial) and metric lead screws. If you don't do this then even engaging on the correct numbers won't work.


I guess I should have been more specific.
If you are threading inch threads on a metric lathe you can't usually disengage the halfnuts and pick up the threads with a thread dial or vise versa. You can do it but not easily, there is a good explanation of why in the Martin Cleeve book Screwcutting in the Lathe, pp 73, 79. One of the examples he uses suggests that if you wanted to cut a 1.75 mm pitch screw on a lathe with an 8 tpi leadscrew with a 50/127 translation ratio, if you disengage the halfnuts, you'd have to wait until the leadscrew turned 874 times before you could re-engage the halfnuts. He also says that geared thread dials for metric threads on inch machines is possible as well but not particularly useful and I've never seen a setup like that in 45+ years.
Is it possible, yes, practical, no in most cases.


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## Richard Hed

skyline1 said:


> The reason your motor draws less current than it's D.C. resistance would suggest is due to back EMF.
> At a standstill the supply only "sees" the D.C. resistance plus a little due to the inductance of the windings so it WILL draw about 2.4 Amps but as the speed increases it will produce Back EMF according to Lenz's law Lenz's law - Wikipedia so that at running speed it only draws 0.75 amps
> 
> The ratio of starting current to running current is about 3.2:1 which is probably about right for this motor although some machines can have a starting current of 10 times  their running current or more
> 
> Starting Current is a big problem on large machines and is the reason for Star Delta and wound rotor resistance starting. More recently electronic soft starts are used.
> 
> I think you may be concentrating on winding impedance and not considering the Back E.M.F. which has a far greater effect
> 
> If you are thinking of going the turbine route my little DeLaval's run at about 30,,000 R.P.M. and produce about 4 Watts at 12 Volts Ish using small permag motors like you get in electric toys I have quite a collection of them of various shapes and sizes (Somewhere amongst my other junk).
> 
> This Is quite a modest speed by turbine standards. The model jet chaps are running at  80,000 R.P.M plus. But even at this speed they do eat bearings I have to change them fairly regularly. (about every 50 Hours or so) I might change them for Ceramic ones at some later date they are available in these small sizes but they are very expensive.
> 
> If you decide to build a little permag alternator I suggest you go for a 4 pole rather than a 2 Pole as this will keep the speed requirement down synchronous speed for a 4 pole machine is 1500 R.P.M. at 50Hz as against 3000 R.P.M. for a 2 pole.
> 
> Decisions, Decisions It's a real Pandoras Box this mini generator caper as I'm sure you are finding out. Experimentation is the name of the game as much as science in small scale as effects that can be largely ignored in larger scales have a much greater effect the smaller you go.
> 
> 
> Best Regards Mark


I would very much like to know more about those ceramic bearings you are talking about.  Have you ever used them for anything?


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## Richard Hed

L98fiero said:


> If that's the case, it may have a metric leadscrew and then, you can't disengage the halfnuts.


I'm sure that for imperial threads I am doing something wrong, but I don't know what it is.  I engage the half-nut properly but the threads walk all over the place anyway.  For internal threads it is impossible so now I just do the turning by hand and leave the half-nut engaged.


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## goldstar31

Richard

Have you checked the  leadscrew, please?  My Myford is 8 TPI whereas my Sieg is 3mm but  3 milli is nearly 1/8th== but NOT.

If you have a worn- well anything or sloppy fits to the gearing???????------or WORSE if your lathe has all of these, time to buy something better

always remember that Martin Cleeve( for those who have read the book) that he made his micrometers using his Myford leadscrew

Points to ponder?

Norman


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## Richard Hed

goldstar31 said:


> Richard
> 
> Have you checked the  leadscrew, please?  My Myford is 8 TPI whereas my Sieg is 3mm but  3 milli is nearly 1/8th== but NOT.
> 
> If you have a worn- well anything or sloppy fits to the gearing???????------or WORSE if your lathe has all of these, time to buy something better
> 
> always remember that Martin Cleeve( for those who have read the book) that he made his micrometers using his Myford leadscrew
> 
> Points to ponder?
> 
> Norman


This lead screw is 16tpi, screwy, eh?  I'll double check however, now that you mention it to see if it is EXACTLY 16 tpi or NEARLY


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## goldstar31

I look forward to your further observations

16 turns= 1 or 2 inches travel


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## Richard Hed

goldstar31 said:


> I look forward to your further observations
> 
> 16 turns= 1 or 2 inches travel


16 tpi = 1 inch.  Altho' I have had this lathe for about 10 years, I have used it very little, as I usually live in the Philippines and haven't had much time to play with it.  But recently, I have been turning parts for toy steam engines.  I am also designing some not-toy engines.  The gears are fine, despite some of them being plastic.  I want to cut some new gears before the plastic ones self destruct.  My daughter and I are working on building a small foundry to cast parts for various projects.  I will needs to make some mold blanks.  Been eyeing those 3D printers, am wondering if my local community college has a 3D printer.  It is much cheaper to "go to school" to use the tools they have than buy one myself--That's something some of you might consider doing if'n you caint afford tools.  Problem is, this weeks (month's, year's decade's) virus is stopping a lot of stuff including the schools.  (Newton had to quit school because of the plague!)

Well, to pay the fees is very little as one pays $5 per unit hour of classroom time plus a bit for general fees at my age (anyone over 60 in my Soviet of Washington).  I planned on going in April of this year (2020) but the school is shut for the virus.


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## goldstar31

Well 16 factorises as well as 8TPI and there should be no difficulty in getting a suitable gear train to cut gears.

My Myford has a set of gears happily tied up in a box to do most things but a tad expensive perhaps whilst the Sieg seems equally at home without!

I, at almost 90 am tied down, sensibly having already disbursed money as the remaining share holder in Mum and Dad's Bank Limited and at the suggestion of my friends have spent a little on my self- for a change.

Meantime, I wish you well in your pursuits

Norman


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## goldstar31

Incidentally and back to dynamos, what happened to Joseph Swan in all this, please?

Again, no mention of the first electric light in the home by Armstrong. It was water powered and the water came into  Cragside from-  Nelly's Moss Lakes

The name Swan also appears in shipbuilding especially on the Tyne. Grand son or great grandson or whatever was involved in shipbuilding until the firm went bust. David and his kids were neighbours of mine.


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## Pedro Walter Lamberti

skyline1 said:


> Yes quite so he reduced Maxwell's correct but rather long winded ideas to something more manageable among his other many accomplishments including research into Characteristic Impedance leading to the development (and patenting) of the coaxial cable.
> 
> I think Europeans and the British in particular have a tendancy towards science as an end in itself whereas Americans are more open to the commercial and practical applications of ideas, which may explain why many European scientists tend to be less well known.
> 
> Best Regards Mark


It is not completely true. William Thomson (Lord Kelvin) was an extraordinary physicist, with great contributions to basic science (electromagnetism and thermodynamics). However, it was related to many technical and commercial ventures. He was in charge of designing the laying of the transoceanic telegraph cable. In addition, in some European museums there are still navigation devices with the Kelvin brand. 

Best Regards, Pedro


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## awake

The typical 7x12 mini-lathes (and variants) typically use 16 tpi leadscrews - at least for the ones sold in the USA. I would guess units sold in other countries might have metric leadscrews?


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## goldstar31

awake said:


> The typical 7x12 mini-lathes (and variants) typically use 16 tpi leadscrews - at least for the ones sold in the USA. I would guess units sold in other countries might have metric leadscrews?


I have no idea  about the UK  7 x 12 varieties but the larger C4 from Sieg is metric to go with the metrication here.
 To go in an out between both only requires a transposing gear. 127 is the exact translation but will not fit the Myford in 20DP form. Hence 63 is normal but with a decent banjo( don't be daft) it is possible to get reasonable results with 20's

But £350 I got  metric outfit and for a few quid more, I could convert the bulk of my Myford accessories to work on the Metric Sieg and vice versa. 

I'm NOT an engineer but I did Economics and Accountancy  way back in the days of blackboards and chalk.


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## Richard Hed

L98fiero said:


> I guess I should have been more specific.
> If you are threading inch threads on a metric lathe you can't usually disengage the halfnuts and pick up the threads with a thread dial or vise versa. You can do it but not easily, there is a good explanation of why in the Martin Cleeve book Screwcutting in the Lathe, pp 73, 79. One of the examples he uses suggests that if you wanted to cut a 1.75 mm pitch screw on a lathe with an 8 tpi leadscrew with a 50/127 translation ratio, if you disengage the halfnuts, you'd have to wait until the leadscrew turned 874 times before you could re-engage the halfnuts. He also says that geared thread dials for metric threads on inch machines is possible as well but not particularly useful and I've never seen a setup like that in 45+ years.
> Is it possible, yes, practical, no in most cases.


What you are saying makes me thimk of exactly what method I used:  I markt an even thread marker on the dial and waited for that to come around to that mark only to engage the half nut.  --  Still no goo.  So I built a hand turning device that one of the Brits had on utube and simply left the nut in place, cutting threads on the in and backing out all by hand.  I thot I was going to destroy my carbide blade, but only chipt it once.  Since my son helpt me do this, I had to make sure HE knew not to stop once a thread was started.  Of course it was much easier with two peeps anyway, as I didn't have to look while turning.  So far I have done two of these for an ER set of collets.  Want to do ER-11, 25, and 40.  and possibly design something that would work for even larger pieces. 

Anybody got any ideas on that?  I was thimking maybe using ER-40 body with some kind of enlarged chuck that sticks out of the body made to grip something maybe up to twice as large as "40".  Somebody probably already makes something like this.


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