Building Grizzly Stirling Engine

[alexkuzn]

My son and I have build a Grizzly horizontal Stirling engine.
It does not want to work on a regular alcohol burner.
It takes a Map gas torch to get the heating cylinder red hot to keep it going.
There is no too much friction. If you flick it with no heat it'll rotate 5-6 times before stopping.
Cooling cylinder and cooling piston have pretty good fit. When oiled there are no visible air leaks between cooling piston and the cylinder.
But heating piston is machined pretty loose inside heating cylinder. I mean really loose.
Is it OK? I am thinking about machining a new heating cylinder on a lathe.
Part #21 in this manual - http://cdn0.grizzly.com/manuals/h8101_m.pdf
My question is how thick the heating cylinder wall should be. The kit's cylinder has very thin walls should we try to get it as thin as possible or a little thinker wall is OK?

Thanks,
Daniel & Alex

[jimlarsen]

I have built one of these. Part of the problem is that Grizzly created their own unique terminology for the parts.

The "cooling piston" is actually the drive piston. It needs to be a sealed fit.

The "heating piston" is what we call the displacer piston. It must be a loose fit. The function it serves is to move the gas inside the engine back and forth between the heated end and the non-heated end of the horizontal pressure chamber. As the piston slides to the left, it forces the air inside the motor to go around it to the space on the right. The loose fit allows the gas to move around as it is intended to do.

The one I built had a bit of trouble with friction. The main challenge for me was that the various sections of the crankshaft were not coplaner (not aligned on a parallel axis) after assembly. I solved the problem by drilling out the bearings to make the shaft holes a tiny fraction larger, and then I loosened the mounting bolts on the bearings so they could move a little as the crankshaft rotated.

http://www.youtube.com/watch?v=A3uSlb86iBs

That's my engine. It runs between 850 and 1000 rpm.

[Ian S C]

Thats unfortunate about the crankshaft. Instead of loosening the bearings, would it not be better to either adjust the crankshaft, or make a new one.
What are you using for fuel, it seems to have a fairly yellow flame. Meths gives a good blue flame, yellow tends to leave a carbon deposit on anything it touches. Ian S C

[jimlarsen]

Yes, making a new crankshaft would have been better. But I don't have the tooling for that. I was building the pre-machined kit. I sent a note to Grizzly and asked for a price quote on the replacement parts to build another crankshaft and it was a bit over $70. That is about half the price of the whole kit, so I didn't do it.

[Ian S C]

Was going to put it here, but have not worked out how. There is a rough sketch in my gallery of a simple way to make an accurate crankshaft. Clamp the two bits of metal for the crank cheeks, and drill as one. The important thing is not to cut the main shaft until the loktite is well set. Just ensure that the webs are parallel. This is how I'll make the crankshaft for my latest motor, it's going to be similar to the Grizzly engine, just a bit smaller, the displacer cylinder is 13 mm diameter (made that bit so far). The crank shaft will be about 2 mm dia, and use the bearings out of the tape pinch wheel from a VHS recorder. Ian S C[album][/album]

Simple Crankshaft.jpg (66.46 KiB) Viewed 7515 times

Oh well looks like I found out how to get a pic on here.

[jimlarsen]

Yes, that is a much better method. I wish I could have done it that way, but in the Grizzly kit all the shaft pieces are cut to length, and the holes already drilled. I found the best fit I could, and then I knurled the ends of the shaft so that it was a pressed fit into the arms.

[Ian S C]

For my crankshaft I'll be using some pins salvaged from the innards of an old VHS recorder. The pins are pressed into the cast aluminium frame that supports all the bits. Another place to find bits is old printers. If any of you are like me, any bit of machinery tends to get stripped for parts, from microwave ovens to worn out angle grinders. Ian S C

[Ian S C]

I got the motor I mentioned earlier going last night, Its a little beam engine, 1/2" stroke, the power cylinder is 3/8" bore, and the displacer is 1\2" bore, the displacer cylinder is made from the steel case of a AA size Ni Cad battery. It runs that freely that it will run without the flywheel, biggest problem is getting a small enough flame. Eventually I'll get a photo of it. it needs a bit of finishing work. Ian S C

[theropod2]

Ian you've just GOT to post a pict of that engine ASAP!

How about distance of the heat source in stead of size?

Way Cool!

R

[Ian S C]

I,v yet to get the little motor finished, mounted on a base, and some sort of burner. It also will get some weight reduction work on bits like the flywheel. Up date, the motor is near enough to finished, found an interesting thing tonight, the pillar that supports the beam on my motor can be moved backward, or foreward (its held in place by two small grub screws), this changes the effective phase angle. While it was running I moved it foreward toward the crankshaft, and the speed increased, move it back and the motor slowed. The only major problem I seem to be having is making a good small burner that won't flood meths every where, The smaller ones seem more difficult than bigger ones. The flame is about 1/2" high, and this is quite adequate. Ian S C