Metal Pipe Gamma Type Engine

[Beauregard]

I am working on a Gamma Type engine using metal pipes.

Here is a rough work-in-progress 3D model of it.

http://skfb.ly/4j3h2f1ba

The Displacer Cylinder is made from two 6" long 2" pipe nipples connected at a T joint. I then have a 2" to 1.5" bushing and a 1.5" to 1" bushing. A 1" street elbow and a 4" pipe nipple. The displacer is a de-pressurized mousse bottle (the dollar store person kept looking at my buzz cut when I bought that...) connected to a threaded rod with locked nuts. I will put a bracket on the top of the cap on the displacer to keep the rod going straight. I do not yet know what I will use for the crankshaft or the piston. I spent hours trying to file down a ridge in the pipe for the power cylinder, but I thing I need to do some machining to get it smooth enough. My family inherited a metal lathe, but I have only used it for wood. I want to learn how to use it so I can machine a simple piston.

[Beauregard]

It might be worth mentioning that the lathe is at least 50 years old, but has worked very well for all the projects using wood I have done.

[Beauregard]

I recorded a short video showing it off, I ramble on, so you might just want to skim through it.

http://www.youtube.com/watch?v=OEfhWWEmaks

[Ian S C]

Beauregard, welcome, I'll have to wait untill Monday to view your vidio, I'm on dial up, andit would take at least 2 hours to down load. Is your lathe an engineers lathe, or a wood lathe? As for your motor, I'll wait till I see the vidio, I don't quite understand your design from the little I'v seen, but you may find that the aluminium can does not last too long, when the motor is at working temperature the aluminium looses its strength, and collapses. If you could, a steel can would be better. Ian S C ps: you might like to put one or two photos in a photo gallery, even a scan of a sketch.

[Ian S C]

Had a look at your vidio, Your lathe is made of metal, but its a wood turning lathe from what I can see. First problem I see is the displacer rod, Threaded rod will not do, it must slide through a hole that is tight enough to have both minimum friction, and minimum leakage of air, so it must be smooth, and round, and pass through a bearing/gland of something like brass, this could be a brass bolt drilled down its length. The displacer must have no leaks, you can find these by putting the displacer in a pot of boiling water, and look for bubbles. The displacer cylinder at the hot end is rather thick, 1.5 mm/1/16" is about right if you use steel, .5 to 1mm if you use stainless steel.
The power CYLINDER; where you have the ridge, cut it off , but you need to polish the bore to get rid of the mark of the welded seam, and if the pipe is galvanised, the zinc has got to go. The piston should have less than half a thousandth of an inch clearance, and just slide down the cylinder under its own weight with NO oil. As metals go, cast iron is best, bronze or brass would be next. Ian S C

[Beauregard]

According to my father it was originally used for metal, even though the bed looks more like a wood lathe. It was made between 1940-1960, maybe back then they used that kind of bed for metal turning.

"a threaded rod will not do"
---possibly, I am remaking the displacer

"a brass bold drilled down its length"
---This is the kind of advice I came to this forum for, thank you very much.

"The displacer cylinder at the hot end is rather thick, 1.5 mm/1/16" is about right if you use steel, .5 to 1mm if you use stainless steel."
---I am not sure what you mean here, are those the dimensions for the gap between the displacer and the displacer cylinder?

"The power CYLINDER; where you have the ridge, cut it off"
---I assume you capitalized CYLINDER because I called it a piston in the video. I am sorry for that, I also said a half turn off, when I believe it should be a quarter turn off.
I was talking about the welding seam when I said ridge, but I may also cut off the top of the pipe nipple.

"but you need to polish the bore to get rid of the mark of the welded seam"
---How would you suggest going about this?

"and if the pipe is galvanised, the zinc has got to go."
---I didn't know that would be a problem, but I will see what I can do to get rid of it.

"The piston should have less than half a thousandth of an inch clearance, and just slide down the cylinder under its own weight with NO oil."
---I wouldn't put oil into it unless I wanted to smell smoke.

"As metals go, cast iron is best, bronze or brass would be next."
---I thought most internal combustion engines used aluminum pistons, why would iron be better? wouldn't it just be heavier? I am sure you are right, but I just don't understand why.

Thank you for your help, I appreciate it.

[Ian S C]

Sorry thought the ridge was at right angles to the seam. The galvanizing can't really be got smooth enough, you want the bore polished. The piston in a hot air motor, unlike an IC engine has no piston rings, and relies on the seal between the piston and the bore, Although you'll read of people using ally pistons, Aluminium is not a good metal to run as a bearing surface unless it's hard anodised. Hot air motors is a study of metalergy, thermodynamics, physics, every bit you can learn is an aid to designing a better motor. One of the most important things with a hot air motor is the reduction of friction, second on the list is eliminating air leaks.
The 1/16" is the thickness of the metal, but that or just a little more would also be the gap between the cylinder and the displacer.
I could not really see, but your lathe does not seem to have a saddle and cross slide, I could be mistaken, or has it been taken off, it would be great if you can use it, a lathe is a/the most valuable tool that you can have. Ian S C

[Beauregard]

Thanks for all your help, you have saved me quite a bit of guess work on the materials to use. I will next be trying to figure out how to polish the bore, and make a steel displacer.

From a page of WoodCraft Magazine on the Delta No. 1460 (c 1939) Lathe, "...with the addition of a specialized tool rest, the lathe could also be used for light metal turning"

I assume that specialized tool rest is the saddle and cross slide you mentioned.

I am also looking for a manual for it.

[Beauregard]

I did some research and found that the lathe had an optional cross slide, and I have found pictures of them. Unfortunately, the lathe was made in 1940 and it is hard to find accessories for machines this old. I did find in my shop a drill press cross slide vise. I am wondering about jerry-rigging it to be used for the lathe. I don't know how much the cutter that mounts onto the cross slide would cost, or where to get it, or what it is called. I will keep looking online to see if anyone is selling a cross slide that would work on this bed.

[Ian S C]

If you know the make of the lathe, and quote its size, ie., if in the USA the maximum diameter that can be swung without hitting the bed, or in UK or a good number of other countries it's the hight of the center of the spindle. If you can do it, boring the power cylinder on the lathe, unless you can find a suitable smooth bored tube. To see what you need, have a look down the bore of any piston engine, whether its a lawn mower, or any other. Ian S C

[Beauregard]

Delta-Milwake No.1466

12inch maximum diameter.

36inch bed length.

I do have a chuck in which the pipe fits nicely.

[Ian S C]

Had a look on google and found the Delta- Milwaukee 1460 12" X 36" wood lathe. One thing that might work for the bore of the power cylinder is one of those flap wheels, its a cylindrical tool that fits in an electric drill. it has a whole lot of bits of carborundum clothand is good for a light clean up, get one a wee bit bigger than the bore, maybe 1/2" or so. The other way is to find some tame fellow modeler/ home engineer who has an engineering lathe.
It could be worth having a look on google(or anything else), put in Dr Koichi Hirata, And look for stirling engined, lets build stirling engines. He has plans, you don't have to follow the exact model, but scale, and adapt to suit yourself. The plans will give you a good idea of whats required. In some motors he uses glass, you don't need to. If you hunt through his sites, you'll find a good bit of information. Ian S C

[Beauregard]

I signed up for classes (high school) yesterday. One of my classes will be "Welding and Machine Tool".

Unfortunately, it is not until February, so my project will be placed on hold. Thanks for all your help so far, I hope to still complete it.

Since I can no longer work on the engine, I will try to make a Parabolic Mirror and Heliostat. (I am good with wood, so I think I will make the mirror framework out of wood, then try to find some sort of reflective coating.)

[Jerry]

If you haven't already, I would suggest you build a tin can or soda can model while you are waiting for your class. Theory is great, but actually building a working Stirling will give you a greater understanding of the little details that make all the difference. Things like side loading torque, placement of connecting points, the advantages/disadvantages of a square design. All these things can be talked/written about, but you don't fully comprehend them without building working models.

I look forward to seeing your progress through your classes!

[Beauregard]

If you haven't already, I would suggest you build a tin can or soda can model while you are waiting for your class. Theory is great, but actually building a working Stirling will give you a greater understanding of the little details that make all the difference. Things like side loading torque, placement of connecting points, the advantages/disadvantages of a square design. All these things can be talked/written about, but you don't fully comprehend them without building working models.

I look forward to seeing your progress through your classes!

I already have my design (for some reason the link to my 3D model is broken, so I may post it again). The only problem I see with is would be too much of a gap in the T joint, bushing (I replaced the 2 bushings with one), and the street joint. If my welding/ machining class is advanced enough, and it needs it, I May fill in some of the pipe to have less air inside. (Most I see have a small little hole between the displacer cylinder and the power cylinder, not a big gap like in mine)