# How Slow Can You Go



## bretk

Ok, Based on the recent posting, here are vids of my slow runners. One, an old wobbler with a history unknown to me, was an ebay basket case find that needed alot of TLC but it sure runs nice now, and very slow for a wobbler. The second was a half completed casting kit that I finished some years ago with the help of a knowledgable steam sage of yesteryear. I'm sure he forgot more about steam engines than I will ever know.

Enjoy -Bret


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## Powder keg

Those are great!!! Dosen't get much slower than that. The first one is neat! I like how the con rod goes all the way through. 

Wes


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## CrewCab

Bret, they are both nice engine's but, I particularly like the second one 8) ......... don't s'pose you have any plans ???

Thanks for the video's, dam fine work 8)

CC


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## bretk

CC,

No plans, That was part of the fun : we just used the castings we had, and fabricated what we didn't,  I have seen similar engines on ebay, but they haven't had the tunnel crosshead guide casting like this one does. I seem to recall someone saying the castings may have come from power models, but scince his place blew up I can't say for sure.

-Bret


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## CallMeAL

Verry Nice! The speed is just about perfect.


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## Paula

Hi Bret,

I know this is an old thread, but I couldn't help but notice how similar your second engine is to one that I built from a casting kit sixteen years ago. It's not *exactly* the same, but they seem too much alike for it to be merely coincidence. Here is a picture of mine (Note: the base originally had mounting lugs like yours, but I removed them and bolted them from beneath the wood platform): 







I purchased the casting set for this engine from "D & M Model Engineering" in late 1990, and have seen very few examples since then. Here is a scan of the 1986 D & M catalog page:






Unfortunately, my engine will not run as slowly as yours! There is no binding in any of the linkage, but it has two cast iron rings on the piston which still impart a significant drag on the cylinder wall. I've tried adjusting the valve for slower running, with negligible results. 

Thanks for posting the videos, Bret! If anyone's interested, I could take a video of my engine running, and post it here for comparison.

Cheers,
Paula


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## steamer

I still have the "who got Sabino to run the slowest" title

She's 7 x 14 x 12... 75 HP compound in the steamboat Sabino at Mystic Seaport.

The record.... 13 rpm.  She was turning so slow the tide was pushing the boat backwards ;D

Set the condensor vacuum to 18 in Hg, open the LP drain valves, set her to full link, and keep your pressure up(110 plus)

Dave


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## Mcgyver

very nice build Paula


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## dparker

Paula: Very nice looking engine there, and WELCOME to the forum. It certainly looks like quite a few hours went into that engine and the paint job is superb! Truly a masterpiece!
Thank you for showing it to us, if you have more please let us see pictures or videos.
don


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## Paula

Thank you for the kind words!

Here is a back view of the engine. I equipped it with a displacement lubricator, just for appearance sake -- it's never been run on steam (ditto the cylinder drain cocks):






The handwheel on the steam valve is custom-made. The original knurled plastic one just didn't look very good to me (though it probably would have saved some burnt fingers if I was using steam).

I will make a video of it running as soon as I can -- my compressor is down for repairs right now.

Thanks again for the compliments.

Paula

(PS - Sorry Bret... I didn't mean to hijack your thread! 
	

	
	
		
		

		
		
	


	




)


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## steamer

That's beautiful Paula!


 ;D :bow:

Dave


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## Paula

Hi again!

Well, I finally got my compressor up and running, so I took a short video of my D & M #11 engine in action. It's running on around 5-7 PSI, with the throttle set to run just fast enough to give a smooth motion. (It will run slower, but in a rather herky-jerky fashion):





Much faster than Bret's engine, I'll grant you. No doubt the main reason is the two 1/16" wide cast iron piston rings, comprising fully one-half the length of the piston. I made it per the drawings, but knowing what I know now, I probably would have used an oil-grooved (ringless) piston, like the one specified for my Stuart 10V. Particularly since this is not a "working" engine, but an occasionally-run "shelf queen". Still, I'm very pleased with how it runs. At higher speed and pressure, it puts out very respectable torque. I only wish that I had known (or cared) how to balance an engine when I built this one.

All comments welcome 

Paula


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## Maryak

Paula and bretk,

That is three very nice engines 
	

	
	
		
		

		
		
	


	







Paula, whats wrong with the balance? 
	

	
	
		
		

		
		
	


	




Best Regards
Bob


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## Paula

Thanks, Bob!



> ...whats wrong with the balance?



At higher speeds, the engine wants to jump around bit. There is a cast-in counterweight feature in the crank disk, but it doesn't seem sufficient to accurately balance the rotating and reciprocating weights. It was only after completing this engine that I learned how to balance an engine properly (I.E. -- I read an article ) However, since the goal with these engines seems to be to run as slowly as possible, high-speed balancing seems a non-issue. 

Cheers,
Paula


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## Maryak

Paula,

Thanks for that. The reason for my question was my concern re balancing my small 1 pot IC engine.

To give it a somewhat rudimentary check I ran it flat out using a drill. I was pleased with the lack of jumping around but the drill is at best 1/4 - 1/2 the operating speed.

It looks like a suck it and see exercise.

Best Regards
Bob


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## cfellows

I have a hit n miss engine that is 1" bore and 1.5" stroke. I balanced it by placing 1/2" neodymium magnets on each of the flywheels, opposite the connecting rod journal, on the inside step of the outer rim. I kept adding magnets side by side until the engine would run with no noticable vibration. Someday, I'll weigh the magnets and make steel plates to attach to each flywheel. For now, the magnets work fine and show no tendency to fly off. I can provide a picture if anyone is interested in seeing it.

Chuck


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## Paula

Chuck, that's a neat idea! 

The method I've used is based on an old article in "Strictly I.C." magazine, by Richard Condon. Basically it states that, for the lowest bearing load and minimum vibration, you want to counterbalance all of the rotating weight + 1/2 of the reciprocating weight (you need an accurate scale for this):

1) Weigh the big end of the connecting rod (place the crank-end on the scale, whilst the piston-end rests on a fixed surface)

2) Weigh the crank bearing (if there is one)

3) Add the above two weights to equal the Total Rotating Weight (TRW)

4) Weigh the piston, pin, and ring(s) to equal Reciprocating Weight (RWT)

5) Weigh the connecting rod (without bearing) to equal Weight of Connecting Rod (WCR)

6) Receprocating Weight (WR) = WCR + RWT - TRW

7) Balance Weight (P) = .5(WR) + TRW

With the crankshaft (or crankshaft-flywheel assembly) resting on knife edges, hang a weight equal to P from the crank pin. The crank assembly should balance the weight. If not, apply weights, drill holes, etc. to achieve balance. That's it.

On my Odds'n Ends engine, I elected to do three things to balance the crank:

1) Made bolt-on counterweights for the crank:






2) Drilled out the crank pin, and

3) Chamfered the crank throws:






There is definitely some trial-and-error involved in getting the crank to balance the P weight. If you know Statics, and calculating density of materials, you should be able to save some time here. 

It worked like a charm for me -- on several engines.

Paula


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## loggerhogger

Nothing better than the quiet magesty of a slow running engine. it almost makes me cringe when I see people 'tacking up" their model steam engines until all you can see is a blur of rods and wheels. they look so much better running slow.


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## Philjoe5

I'm with you loggerhogger on that. I've been able to build a steam (air operated) engine that will rotate at 60 rpm. That's the best I can do to this point. I hope when I put more hours on some of them I'll be able to get them running slower.

Cheers,
Phil


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## Philjoe5

Again I'm resurrecting an old thread, but when I first read it I kept it in the back of my (convoluted?) mind. One of my aims in building an engine is always to see how slow I can run it. 

During the recent Cabin Fever Expo I picked up some needle valve air flow controllers. These valves allow really fine air control. I set up two of my engines that had some break-in time on them. From my compressor I have ¼ air hose going to a 1/8 NPT line that connects to the flow control. Out of the flow controller I have 3/32 OD polyethylene tubing of 0.105 ID going to the intake of the engines. 

The engine shown here has a 1.5 bore x 2.1 stroke and is double acting. The flywheel is 6 diameter. Im able to run it at about 50 rpm.  

[ame]http://www.youtube.com/watch?v=vrxSkJBz7HI[/ame]

The engine shown here has a 1.25 bore x 1.8 stroke and is also double acting. The flywheel is 6 diameter. Im able to run it at just shy of 50 rpm.  

[ame]http://www.youtube.com/watch?v=zSucuwlOTBU[/ame]

I think this will be the best I can do with this design but I am still wondering.whats the lower limit. Has anyone constructed a model engine (air or steam powered) and run it at 10 rpm or less? ??? I feel like Monty Python and the Holy Grail here. :big:

Cheers,
Phil


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## Jones

When I have it running next I will try to get a video of the wobbler I made. It would have to be one of the slowest running 'single acting wobbler' engines out there. It has ball races on the crank and big end.


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## fdew

I don't know if this will work on an engine or not, but on pneumatics, when you want to go slow you put a needle valve on the exhaust, not on the input. It might be worth a try.

Don't do this with steam. Just air.

Frank


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## rake60

Now THAT is some impressive lack of speed Phil! :bow: :bow: :bow:

Rick


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## chuck foster

i have seen allot of slow running engines but phil that has to be the slowest 8) 

chuck


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## Philjoe5

Funny, that's exactly what many of my former teachers said about me. Little did they know that some folks find that a noble goal :big:

Cheers,
Phil


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## steamboatmodel

fdew  said:
			
		

> I don't know if this will work on an engine or not, but on pneumatics, when you want to go slow you put a needle valve on the exhaust, not on the input. It might be worth a try.
> 
> Don't do this with steam. Just air.
> 
> Frank


I remember when taking a pneumatics course the instructor telling us " When in doubt meter out". if you have the needle valve on the exhaust you are creating a back pressure which will work with some valves (piston), but may cause problems with slide valves.
Regards,
Gerald


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## old_bones

Hi All,

This is my entry for the "How Slow Can You Go" challenge. It's a horizontal mill engine with 1.0" bore and 2.0" stroke.

[ame]http://www.youtube.com/watch?v=1FguWF5nef0[/ame]

I don't think it wins the prize but my grandchildren love to watch it go.


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## chuck foster

i think you have won just by having your grandchildren intersted in the engine 8)

chuck


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## potman

I've noticed that some of these engines appear to slow down when the crankpin is moving up and almost stall just as it reaches it's highest point. I assume this is because energy to lift the connecting rod against gravity is being sucked from the engine. If one were to add a counterweight on the flywheel just opposite the crank would the engine be able to run slower?

Anybody want to try it and report back?

earl...


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## Philjoe5

Being a fan of the slo-mo engine at some point I'll try a needle valve restrictor on the exhaust and the flywheel counterweight. Both sound feasible and easy enough to try. Just don't know when I'll get to it. ???

Cheers,
Phil


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## Noitoen

potman  said:
			
		

> I've noticed that some of these engines appear to slow down when the crankpin is moving up and almost stall just as it reaches it's highest point. I assume this is because energy to lift the connecting rod against gravity is being sucked from the engine. If one were to add a counterweight on the flywheel just opposite the crank would the engine be able to run slower?
> 
> Anybody want to try it and report back?
> 
> earl...


My understanding of the thing is that the area of the piston is different because of the connecting rod. Since the pressure is constant, the low pressure has grater difficulty to move the piston "up" than "down. :


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## rake60

This is a great thread!

Models that are running this slow are actually producing output power.
It might not get you from 0 to 60 in 5 seconds, but it is just as impressive
for the scale. 

It's a model powering a flywheel rather than a flywheel keeping a model
running. Does that make any sense at all? scratch.gif

Beautiful Works Everyone! :bow:

Rick


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## dparker

Hello All: This intrigues me I suppose when things are running fast they don't seem to last (Hopped up motors). I enjoy seeing something running slow and lasting forever or at least being reliable.
My examples seem to gather more interest when running slow than running at higher speeds.
McCabes Runner:
[ame]http://www.youtube.com/watch?v=_0OlpkLcddM[/ame]
The Stuart 10V will run very slow if desired (sorry not what we were trying for when these pictures were made) but It may give you somewhat of a idea about the model.
[youtube=425,350]gxPKYE4ZVqg[/youtube]
These engines sit on the shelf most of the time because I know of only two brothers in the neighborhood who are even interested in this kind of toys. It is amazing that the wife can find the remanents of home machine shops at estate sales around the area. I wish we were not so paranoid to let people know our interests but then you open yourself to exposure to the bad element and it is safer to keep your mouth shut I guess.
--don


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## Philjoe5

Hey Don,
Neat engines....you've got that McCabes Runner to go pretty slow :bow: I like the Stuart too and hope to build one someday

Cheers,
Phil


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## Philjoe5

I have a video of my latest engine running at about 30 rpm. I can't get it to run slower without stalling but it only has an hour of break-in time on it. I had thought that this design would allow for slower operating speeds based upon some of the discussion here and elsewhere. Here you go:

[ame]http://www.youtube.com/watch?v=F2c9oPjSbW0[/ame]

I think, for now, I've reached a personal goal and will now move on ;D

Cheers,
Phil


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## zeeprogrammer

That is so cool.
I like slow.


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## Cheshire Steve

Its a shame if a model with an interesting linkage can't be run slow enough to see it. I am currently building a true-to-scale beam engine so people could watch the Watts linkage, and it occurred to me that this one will have to run slow if people are going to appreciate the motion.

Apart from the obvious issues of balancing and reducing friction, there is a fundamental role of scale - they say you can't scale nature - and in some ways this is true. Some things scale with volume (like weight), so at 1/10th scale you have 1/1000th of the weight. Other things scale with area, like force on a piston or area of bearings, and as for flywheels, well they don't scale well at all.

So getting a scale model to run slowly is a real challenge, with best chance being for engines that are multi-cylinder, large scale, and those that had big flywheels to give excellent speed stability (such as those used to generate electricity). You may not get the speed stability, but at least they should run fairly slow.

Has anyone any thoughts on whether the type of piston rings (or no rings) is important in getting slow running ? I am guessing having no rings, but a couple of oil grooves, is lowest friction as this seems the common type for hot air engines.

Steve


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## Philjoe5

Steve,
FWIW I'm using 3 oil grooves that are 0.003" deep. 

Cheers,
Phil


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## DavesWimshurst

My Stuart beam engine has piston rings but no packing on the rods. It seems to have more friction than the similar bore Stuart 10V with graphited yarn packing. Here it is running at 44 rpm:





Dave


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## Kermit

Cheshire Steve  said:
			
		

> Its a shame if a model with an interesting linkage can't be run slow enough to see it. I am currently building a true-to-scale beam engine so people could watch the Watts linkage, and it occurred to me that this one will have to run slow if people are going to appreciate the motion.



Perhaps the key to success with slow speed is to keep a decent amount of pressure, say something that gets you 70 RPM and then INCREASE friction thereby loading down the motor. You should be able to get much slower. try a piece of felt over the top of a rubber band. The more you stretch the rubber the more the friction increase.



Throwing ideas at the wall, hoping something helpful sticks,
Kermit


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## Florian

Hello

Guess i can also show my engine: 
It runs really nice for the first minute... 
The fizzy sound in the background comes from the safety valve...
At 1:22 you can see the small amount of steam coming out of it.

[ame=http://www.youtube.com/watch?v=bM71fK6xOWA]http://www.youtube.com/watch?v=bM71fK6xOWA[/ame]

Florian


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## SignalFailure

Florian  said:
			
		

> Guess i can also show my engine....



Glad you did Florian, I really enjoyed that. What a great engine :bow: :bow: :bow:


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## zeeprogrammer

Very nice.
Nice boiler too. I hadn't seen one like that (I'm new).
Built?


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## rake60

Very well done Florian! :bow:

Rick


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## kustomkb

Very nice engine and boiler too!!

The sound is very soothing.


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## Maryak

Congratulations to all you slow runners :bow: :bow:

A special one for Florian as it's powered by his own Scotch Boiler. :bow:

Florian is that an adaptation of Walscherts valve gear ??? Neat.

Best Regards
Bob


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## Florian

Hi Bob

Yeah, its kind of an excenter which has been copied from the walscherts gear. 
But without the reversing gear. 
But that is an option for later... 

@zeeprogrammer: 
Here you can see pictures of what i have built: http://www.homemodelenginemachinist.com/index.php?topic=1877.0

Florian


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## hammers-n-nails

this is my first engine at what i figure to be 22 rpm at between 5 and 10psi air(gauge doesnt realy read below 10) and yes its not very pleasing to look at
[ame]http://www.youtube.com/watch?v=0wuRjfjlv7I[/ame]


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## zeeprogrammer

Florian....just ran across the link you posted for me. Wow. Very glad I found it. I have to go to work soon but I'll be spending some time there. Thanks.


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## itowbig

hammers that is slow alright  looks good to me


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