Video of an engine just made from bits hanging around the shop.
No pretence to be elegant, just curious to see if I could make one.
Lots of parts not made too well, the clattering is from the Displacer big-end bearing.
Actually sounds a lot louder on the clip than for real.
No need to mention I'm a rubbish camera operator. I know.
Don't worry about the sound, I have the same problem, the camera really needs a separate microphone, or some way of adjusting the volume. A nice runner. Ian S C
Well, ran it for over two hours today, stripped the engine and found no real problems. Bit surprised ...
The power piston is 20mm dia. PTFE. I did expect to see some scoring, but it was quite OK apart from a small 2mm dia. mark, and a similar mark on the bore.
Why, I don't know. Does not seem to have 'picked up'. I would expect a linear mark on the bore?
The hot cap is only hard soldered with Cad free 440 grade solder. This has a melting point around 680 - 700 C.
When I first ran the engine last week it went a lot faster than the clip...... until the solder let go ..
Which is why the flame is not directed at the solder joint.
RPM in the clip is about 700. Hard to measure, I have to use the 'surface speed' wheel on my tachometer.
This slows the engine as a fair bit of pressure is needed on the rubber wheel, otherewise it just skids.
It will run with a very low flame, just the edge playing on the hot cylinder, but it does have one serious problem.
It takes a LOT of heat to get it to start.
There is far, far too much metal on the power cylinder.
I assume that when the power piston moves down the power stroke, there is a lot of cold metal exposed to the gas, and it drops pressure.
I get it going by using a rubber disc on the edge of the flywheel, powered by a battery drill.
After 3-4 minutes of this nonsense it just goes ..
I will post some details later if you wish. There is some work to be done re-making the poor parts. I'll post the major dimensions.
Bearing in mind it was made from available materials, many are not ideal.
You'l proberbly find that it will go with a flick if you just leave it 4 or 5 miniutes.
I think it may start, and run with more power if the diameter of the flywheel was increased say about 1" and theinner diameter thinned, and some holes drilled (spokes), the weight toward the hub is of no use, its the weight at the rim that does the work, the flywheel may not be heavier than the origional one.
Interested in the use of a trunk guide on the power piston, that may be a point of friction. I use as long a con rod as I can to keep the angle as small as possible, and use a cast iron piston with a gudgion pin. I presume it has to do with the Teflon piston, Another place to use the Teflon is the bush in the displacer rod gland, and maybe it could be used in the trunk guide. Ian S C
Didn't have any CI for the piston. The original was made from aluminium alloy, but it scored very badly.
No idea what alloy grade it was, just a bit of bar lying around. The only other option I had without going to buy metal for the job was either M.Steel, S/Steel or more brass. As the bore is brass, that was discounted. So, I tried the PTFE. I had some 25mm round, so that was it.
Many thermoplastics have quite a high thermal expansion rate, which is why I had to skim .002" off the thing ... after seizing it on the first run. It looks fine now.
Flywheel was made from a 4" dia Phosphor Bronze offcut. The only other stuff I had remotely like it was some 20mm M.Steel plate.
Not about to spend an unhappy day sawing and turning that !! I don't want to machine the flywheel as I want it for a steam engine later.
Rather surprised it goes as well as it does. I need to re-make the hot cylinder, The solder will not take any real heat.
Needs to be welded, rather than soldered. But that's for another day. Need to go on the scrounge at a local engineering shop, see if I can get something more suitable for the flywheel.
For the hot end, if I need to braze it I use brass, either swarfe from the lathe, if I get a brass that comes of in long strips (its usually fine little chips), or .5 mm brass wire. The brass takes a bit more heat, but LPG is ok if you have a big enough burner.
When you get the balance of expansion right the Teflon should be good.
The 2.5 cc motor in my photo gallery has a aluminium piston with a thin skirt of carbon impregnated teflon running in a bit of brass tube as a cylinder. I did'nt lap the cylinder, the tube is just as I got it, it's a bit more polished now. Ian S C
