Sneft ringbom engine simulation

[sumit]

Hi everybody,

As a part of my Master's project I have to fabricate a ringbom engine prototype.
Here is the link of my Isothermal simulation http://www.youtube.com/watch?v=R1z7geI7Y5Y

I want to know how much valid is this simulation?
I came across sites saying 0.4*efficiency of an isothermal efficiency is a good prototype, how much correct is it?

Thanks and regards,
Sumit Jadhav
IIT Hyderabad
me10b017@iith.ac.in

[Ian S C]

If you look on my gallery you will find a "blue print" of J. R. Sneft's Tapper, Ringbom motor, you can make it air cooled as per the original, or make it water cooled as I did, it could be reduced in size ie., a power piston of 6 mm would work, just gets more difficult as you get smaller, or you can scale it up, I have one with a 35 mm bore, 20 mm stroke power cylinder. The larger one was being developed as a stove top fan, but proved to be too powerful for what I needed, and also made too much noise, it must be possible to design a motor that is less noisy. If you scale off the "blue print", you should get a working motor. Ian S C

[sumit]

Thank you much for the design scaling information and the blueprint!!
Can you please tell me any information about the efficiency and power output of it?

[Ian S C]

Efficiency, not very, power not much for two of mine, the third one, the stove top fan is much better, too powerfull for a fan, the gyroscopic effect of the fan causes the motor to rotate on the stove. Ian S C

[blade]

Sumit,

If you're interested in efficiency, you may want to check out the following paper.

http://www.readanybook.com/ts-3-thermod ... df-i284489

Dead space plays a huge role in engine efficiency, and Senft's books completely neglect the issue of dead space. However, the analysis in his books is great for other stuff. The paper I linked has two errors. They heat the entire mass of gas instead of just the mass of gas in the displacer, and they make an algebra error replacing Cv with (k-1) in one location. These two errors are easily fixed, and their paper is well written.

[Ian S C]

With the Ringbom engine the displacer finds it's own stroke, this varies according to the load on the power side of the motor, so with no load the displacer moves over a short stroke, then with the load coming on the stroke increases, until it lives up to the name of tapper when the displacer hits the ends of the cylinder.
Ian S C

[sumit]

Thanks a ton, Ian and Blade!!!
:)

[Ian S C]

The simulation of a Ringbom engine was not too convincing in my opinion, draw up your engine with pencil and paper if you need to, then build it, first of all you must under stand how one of these motors works, also understand the the standard of work required to make it, and get it working.
I would start by building an ordinary Stirling Engine model to a design that is known to work. I would not make a low temperature Ringbom, unless I had made, and got running, a LTD SE, it may be possible to make a low temp Ringbom, don't know. See the blue print of Tapper in my album. Ian S C[album][/album]

[sumit]

I am about to start manufacturing one!!

As it is my honors project I am supposed to manufacture a new design, arrived with some research.
Any idea from where we can get the exact dimensions of the blueprint design and other parameters like mass of displacer and flywheel, temperature difference etc..?

[Ian S C]

Do as I did ,and scale it of the drawing, direct from the drawing gives a power cylinder bore of 19 mm, this would work well, or it could be increased up to double that. The fins could be replaced, as I did, with a water jacket, connected to a water tank or radiator. Ian S C

[sumit]

Thanks Ian for the info!!

I wanted to know how much should be crank rod to connecting rod ratio?

[Ian S C]

I'm away from home at the moment, but you will fid the aproxament stroke off the drawing, the piston is at, or about half stroke in the drawing, it's probably near 20 mm.
Ian S C