Improved run Simpson and Shipton

Improved the running of the engine by changing the PTFE piston for cast iron, I've olso re-sculptured the base to improve access.

http://youtu.be/WmSIJhs8Vgo

That's running great now Stew, nice job.

JD

Thanks for you're interest Jeff

I'm still not 100% happy with the engine, it should run slower at a lower pressure, I think I may have the fly wheel size wrong, I've ordered a 7" fly wheel casting from RDG that I'm going to mount on a new bed plate supported with two bearings either side.

Still a way to go with this one I think

Stew

Stew, I think all thats needed is a much heavyer rim on the flywheel, I would not go up too much in diameter, but the weight does not scale, as seen with flyweights on a govenor on models. Sounds good, what speed would the full size engine run at? I always think the test of an engine is how slow will it go, Its often easy to get it to go fast, demonstrated that when we had a night class building a little wobbler, and boiler, the standard flywheel was 40 mmx 12mm, min 300 rpm, so I made my flywheel from brass, same size, min about 50 rpm. Ian S C

Thanks for your input Ian

There is a video on Utube of a extreamly nice engine running at a slow speed, this one has quite a large flywheel, suported with two bearing one either side, I think my support of the fly wheel is wrong.

No idea waht speed the full size engines ran at, there is only firm proof of one engine ever being built this one was displayed at the great exhibition, though a second may have bin made.

I stuck a taco on mine and it belts along at 850 rpm at full pressure 50psi, with not a lot of vibration

Stew

I emailed Stewart about a possible drawing error on the Simpson and Shipton engine piston. He emailed back that the 15 mm dia hole shown on the piston drawing in ME 4437 is a mistake, it should not be there. It was a holdover from the original PTFE piston design which is no longer used.

The piston as shown in photos in ME 4439 has no 15 mm dia hole and is shown correctly there.

Hopefully no one has got this far with the engine and drilled the 15 mm hole yet. If they have, the hole could be plugged with a solid piece of CI secured with press fit, loctite or silver solder, or two plugs could be fitted at ends of the hole.

(In ME 4437 the drawing shows the gland packing trepanned groove crossing the 15 mm hole and the 8 mm
hole. When I first saw it, I remember thinking the gland packing would fall
into the 15 mm hole and sealing would be lost, but since the text describing
the piston was to follow in the next article, I figured details of loctited
or brazed or pressed plugs in the ends of the 15 mm hole would follow, or a similar
method.)

JD