Jan Ridders eggcup stirling

[J. Tranter]

Bogstandard I am sorry to keep bothering you with my questions. What material did you use for the hot cylinder wall?
John T.

 

[Bogstandard]

John,

It is no trouble answering your questions, just ask away whenever you want.

If you are referring to the clear plastic displacement cylinder, it is a bit of a long story.

The plans call for 50mm clear acrylic tube, with a 2mm wall thickness, obtainable on ebay at very realistic prices. But if you have any plastic tube (it doesn't have to be clear, but it looks nice if it is) of about that diameter, it should work, just modify the groove it sits in for thickness and width. Then make the displacement piston diameter to match (2mm smaller than the internal diameter of the tube).
I changed the material for the displacement piston as well, but don't know if it will work yet. To get recycled clear plastic for making those out of (as per the plan), find the wife's most prized CD (the one you really hate to listen to) and deny all knowledge where it is, the clear plastic that makes up the case is just the job, a bit brittle, but machines up into discs very well. I wouldn't tap it as suggested, but drill a 2mm centre hole, and turn the piston rod overlength, by the same thickness as the plastic, with a 2mm diameter spigot on the end the same thickness as the piston, and epoxy it on (do not use superglue anywhere near these types of engines, you stand a great chance of making the plastic 'bloom' with a white powdery deposit). This brittle type of material has a tendency to crack if you put any tightening stresses on it, as in trying to tighten a thread, but perfect for this little job. Don't forget to destroy all evidence of the case contents, don't put it into the recycle box, she is bound to find it, and want answers.

My long story is that a few years ago I purchased some very modern looking wall lights to go around my garden, stainless steel tubes, mounted on the end of which was a super bright bulb that was housed in a clear tube about 8" long. Within two weeks of installation two of the bulbs had blown ($10 each), the units had only cost a bit more than $16 for 5 of them (2 sets, 10 lamps in all, cheap chinese imports), so they were duly ripped off the fence and normal lights fitted. They were consigned to my bits to recycle boxes. When I got this plan and saw the size of tubing, I immediately checked the ones in the box for size, 51mm (2"), "close enough for me", says I, you are seeing the results. I have enough, with wastage, to make over 60 of these little devils, but not enough spare time to do them all.

I hope this helps

John

BTW if you need to know how to turn up the discs, just ask away.

 

[Bogstandard]

Got one of them sealed up and almost looking like an engine, then duly dropped it and bent the crank like a banana. Must use good hand to pick things up.

Two hours straightening in the lathe later, I managed to get it on its first tentantive steps to actually working.
For those that remember the elbow engine builds we did (how many are still under the bench?), well this one nearly matches that. Because of the V-E-R-Y limited power output because of its size, fart anywhere near it and it just won't turn over. Friction is the killer, and oil will kill it dead, perfectly smooth fits and adjustments all around are the order of the day.
This roughie vid explains the first steps. BTW, the reason it wouldn't run when I took it off the warmer was I was trying to start it in the wrong direction (a real Homer moment), but it is difficult to do when looking thru an eyepiece, trying to keep everthing steady with a gammy arm, and the old anal sphincter is twitching, trying to keep up with everything that is going on. Excuses over, here is my version of Jans eggcup engine.

[youtube=425,350]6VsuC9sLT9U[/youtube]

Now for a few remarks about the engine.
This was my first LTD engine, and I really enjoyed the build. But a very big BUT, if it wasn't for all my years of experience getting little things to work I think I would have really struggled on this one. So I would suggest not as a first build, try one of the larger ones first and gain a bit of experience in friction reduction, then come back to this.
I was going to build three of these, and all the bits are made, ready for assembly, but because of all the time spent getting it to run, it has meant I have overrun my time for this project, and the others will be stored away for a time when a bit of play is called for. So you won't see the red, white and blue bouncing up and down in unison just yet.

Next project, an experimental impulse (pocket edged) three rotor turbine with reverse and throttle. I walked into this one without realising. Due to start early next week, or even earlier.

John

 

[Brass_Machine]

Nice work John. Less than 15 days from your initial post you have a runner!

Glad to hear your review of it. I have a set of Jan's plans as well. I think I will wait til I have some more experience.

This turbine project sounds neat... Please keep us informed.

Eric

 

[J. Tranter]

Bogstandard can you please explain how you turned up the disks.
John T.

 

[Bogstandard]

When I get into the shop later, I will do a little article on it and put it in the tips and tricks section.

John

 

[Powder keg]

As always, Great job and thanks for sharing) I hope I can get mine to run again.

Wes

 

[Bogstandard]

You will Wes, just take it one micro step at a time, as I had to do with this one.

Try jiggery, pokery, flickery and trickery, if that doesn't work, start at the beginning again.
Exactly what I did. That is why I wouldn't recommend this one for a beginner, with something a little larger you can see what you are doing, with one this small you are stabbing in the dark.
But now I have been thru it, when I build the others up, I know exactly where the problems lie.

Just another learning curve of life.

John

 

[Bogstandard]

John T,
I have done a little article showing how I do the discs.

http://www.homemodelenginemachinist.com/index.php?topic=1510.0

John

 

[J. Tranter]

Bogstandard how did you connect your piston rods to your crank?
John T

 

[Bogstandard]

John,

Because the little crankpins are an integral part of the strength of the whole crank, I V-E-R-Y carefully silver soldered 2mm pins in from the outside faces of the crank webs, ensuring that I didn't put too much silver solder on so that it could migrate too far thru the hole and solder the conrods up as well. All I managed to do is lock it up with flux, and that was easily removed by my pickle bath. Only after doing this bit of soldering could the main shaft be cut away between the crank discs to make a true crank.


The bottom end of the conrods are held with 1.5mm hardened dowel pins, just a push fit, and will be left like this so that the engine can at least be partially stripped down if needs be.

Please excuse the quality of the pic and parts, nothing has been cleaned up and polished yet. Just enough to get it on trial runs.
The soldered pins will eventually be ground back to blend in with the crankdiscs.

If you can manage to do this, you will never have any trouble silver soldering anything together ever again. This is about as tight as it will ever get.

Hope this has helped

John

 

[cfellows]

That sure is a purty flywheel. Actually, the whole engine is very nice, but I'm kind of partial to flywheels!

Chuck

 

[Bogstandard]

Thanks Chuck,

I too have a fetish for flywheels. It is sometimes the only way when building from plans to put your own 'mark' on an engine. When making them I try to think of new shapes that can be easily made. Once you can get your head around the concept on the RT, you can imagine the outcome. The 'snowflake' shaped one at the beginning of this article only took about half hour to cut from the basic blank.

What does take more time than anything else is blending all the radii and straight lines together afterwards.

Marvs 'Flywheel' prog is about the best place to start when you first start out. It does all the basic calculations for you.

John

 

[cfellows]

John,

The hub looks like it was added after the flywheel was turned. Is it a separate piece?

Chuck

 

[Bogstandard]

Chuck,

Or should I call you Hawkeye.

I wasn't really happy with the look and the width of the hub (for securing to crank with loctite) so I put a small extension piece in the middle and blended it in. It didn't really need it, it was just me being fussy.

I can't get away with anything with you lot.

John

 

[DickDastardly40]

John,

You've mentioned about balancing the flywheel, when you get the time (god knows how you find any), could you describe the process you use.

Do you see where the wheel naturally settles at rest a few times and add weight to the high side or remove material from the low side?

Thanks in advance.

Al

 

[Bogstandard]

Al,

I only ever balance just as you suggested, that to me is good enough for what I do. There are purists that go the whole hog and I am sure that they will speak up.
I made my turbine last year and did a quickie balance by reducing the heavy side and that run with no vibrations at all to way over 40k.

What I do is use a piece of blutack on the light side, adding or subtracting (maybe in a couple of places) until the wheel stops in a totally random position. You should really do it on levelled knife edges or a purpose made leveller, but I use the bearing that I will be using in the engine( if it is free enough), and have found that is sufficient for me.

Anyway, it now gets super technical.
Mark the wheel opposite to where you have your blutack positioned.
I have a set of not too precision scales (sold to the junkie trade), and balance the blutack with shavings of the material the wheel is made from (it pays not to clean up too often). This gives me a rough eyeball size to drill the heavy side, maybe it will take a few shallow holes next to each other to get it stopping in no particular place. If you are way out of wack, drill where the light spot is and fill with lead first, just to get some semblance of balance, then go back to balancing and drilling the heavy side. I have only ever had to do this once and that was with a commercial cast flywheel. Either there must have been an air inclusion in the casting or one or two of the spokes was a bit thicker, or both.
Just remember, it is easier taking it off than putting it back on. Try a bit, not enough, try a bit more.
This might seem a bit of a slapdash method to the purists, but it works for me, and I have never had any balancing problems with my engines.

Just as a note, on this little eggcup engine, Jan says to balance it all up after the engine is assembled before the bottom plate is fixed permanently in position. In a rush, I forgot to do it, but it runs, and runs well, so it can't be far out.

You might say that if you machined it correctly, it shouldn't be out of balance. You only have to be 1 thou out on one side, and you are out of balance. But in most cases I would ignore balancing of flywheels unless it is either a very fast engine or one that requires a lot of friction reduction, as in sterling engines.

You can actually use the balancing in a visual manner, use a small coin and move it about on the side face of the flywheel until you get balance and just superglue it on.

Nothing is tabboo, if it looks right do it, it is your engine.

BTW I will be balancing the rotor in my turbine project this afternoon. I will take any relevant piccies and put them in the post.

BTW2 On the piccy of the flywheel above, there is a blue mark on the flywheel. That is the light area mark for the flywheel on its own.

John

 

[Bogstandard]

I have put my article on balancing here

http://www.homemodelenginemachinist.com/index.php?topic=1552.0

John