Engines > Your Own Design

Jekyll's "Pendulous" Engine c1870

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Jasonb:
I first became aware of this engine about six years ago when it appeared along with some others in a Bonham's Auction and filled the image and description away in my "Future Projects" folder on the PC. It seems quite a few others like it as the image crops up quite often on sites like Pinterest but I have not seen anyone else have a go at making one.



The original was a fairly large model and I settled on a scale of about 4/10ths based on using a piece of 203mm thick wall tube to make the flywheel rim from which gave me a bore of 16mm and stroke of 48mm. Armed with these numbers I set to and drew it out in Alibre. It took a while to arrive at the right pivot point and length of the valve links to get the slide valve to move correctly on the 3D simulation hopefully it will do the same on the physical model. There are a few areas that I have done a bit differently such as the valve chest but the finished model should be reasonably close to Jekyll's original.



I have not taken photos of all the work but will show the main fabrications and more interesting bits.

I decided to make a start on the two arched column supports. The actual arch part was made by turning down some more thick walled steel tube to the correct inner and outer diameters and then milling away what was not needed before parting the 4 pieces off.



The remaining parts were cut from flat and square bar, I left the feet as one long piece of bar which allowed a bolt to go through the middle with a suitable spacer to hold the square part central and at the correct height for silver soldering.



The two "castings" after a dip in the pickle



The waste material was then sawn out and the cuts edges milled to final size. The counterbored hole will take a cap head screw to attach the column. The tops will be skimmed to final height once the base plate is made and they can be screwed to it in exact position.

Michael S.:
Hello Jason,
that will be a fine model!
When I discovered a video of yours on YouTube about the engine a few days ago, I thought I had seen an engine like that somewhere before. (I have attached a picture from "The Steam Model" issue 2 from 1998)
But now I know it will be something different.

Greetings Michael

Jasonb:
Thanks for the interest, there are a few similar engines such as the Maudsley but all have a few differences. The engine on this one pivots right at the bottom with the trunnions being mounted on what is effectively a thick cylinder end cover where as the kientzy's pivots closer to the middle and the valve arrangement is a bit different too.

Anthony Mount also did the Kientzy, and the kit can be bought from Pollyengineering.

An original that is quite similar though again a different valve layout

Michael S.:
Yes, the cylinder in the video reminded me of the Kientzy at first.
In any case, you built the first parts very well.

Michael

Charles Lamont:
Looks potentially a very elegant model. Would I be being rude if I made a couple of aesthetic suggestions? I think your flywheel rim could be a good deal lighter. It is hard to tell, but in the photo of the original, I think the spokes are slightly tapered so as to be recessed from the faces of the rim, though they do not seem tapered as viewed face-on. 

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