Saturday, March 19, 2011

Updated Sketch Up model and piston assemblies

I have shared the model in Google and will upload it to the web site. The pistons now have 4 nylon screws that protrude through the cores and shell to keep its base centered. This should prevent the piston crown from scraping the plastic seal, which is just a polyethylene bag, because the pressure on it should center the front.

The seal bag is not included in the model, I am still trying to figure out how to represent it.

The current heat exchangers are also shown attached, but without the hoses for the hot and cold water.

Added the piston core caps and the push rod guide's bearings. Push rods have cutouts to allow snapping them on and off the wrist pin, to make changing the bags easier.

It now pretty much represents the current state of the real prototype. I still have to rebuild 2 more of the pistons to install the new shells with 50 mil clearance and the Nylon spacer screws.

I hoping once back together this time, it should be able to hold pressure long enough it to get it run. It has a low displacement cam, so should run with a pretty low temperature difference ~40 degrees F. So far I only have one pair of heat exchangers, which I pump ice water through. Still need a heating means for the hot cylinders. I was just heating the heads with torch, but since most of other parts are plastic or rubber, that is not a good idea. I may just use some high wattage resistors, it would be less messy than using hot water.


Adam Bradley said...

Looks very similar to


Carl T. Knox said...

Heat Source - consider a used electric wall paper steamer, reuse the condensate.
Crankshaft Cam - consider a "Scotch Yoke" (Google Images)

Tom Belpasso said...

Hi Adam,

Thanks for the input. I have a link to the whispergen on the main site.

Yes, from a mechanical point of view, my design is very similar to the whispergen. The whispergen has a very innovative variable pressure piston seal to reduce the friction at startup. It also can vary the piston stroke, by changing the tilt of the swash plate, which is what they use instead of a cam. The swash plate converts the vertical motion of the parallel pistons to rotate the also vertical shaft.

The main difference with my design, besides the seal is the ease of scaling the power output by stacking 4 piston stages on a single shaft. Stroke can be varied to modify the temperature difference, by changing only the cam.

Tom Belpasso said...

Hi Carl,

Thanks for the suggestion.
As long as I have the polyethylene bags, the maximum temperature for the hot side will be under 180 degrees F. I'm afraid the steamer would be too hot for now. After switching to a higher temperature seal material a steam is an intriguing idea. I have a propane fired hand pumped Colman hot water heater that I will add an electric pump to when I get all the pistons sealed.

Er Russi said...

Hi Friends

I will like to construct a stirling engine model but dont know about the parts required for my prototype. please suggest me how to start and components required. i shall be very very thankful to you.

With Regards

Engine Mounting said...
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