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Theseus Horizontal Steam Engine Completed...

Started circa 1959 - completed January 2018!

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Peter Benning29/01/2018 21:56:20
10 forum posts
8 photos

Apparently this may not be a record! Anyway I have now completed it and mechanically it works, but I'm trying to run it on compressed air and it will not turn. The slide valve timing via the eccentric strap has been adjusted so that when the piston is at the far end, the slide valve is at the far end, so that as the piston starts to go up the cylinder the valve will open the port to allow air into the end of the cylinder to complete the stroke. When I add the compressed air (No particular pressure) to the top of the steam chest, it comes straight out of the exhaust port! I have taken the end cylinder cover off and air does come out the port... At the right time?

Does the slide valve timing need to be advanced (like in a car engine)?

Any help would be appreciated.

Peter Benning - New email:

Robbo29/01/2018 22:07:54
1504 forum posts
142 photos

Have a look at this link for starters : **LINK**

Peter Benning30/01/2018 00:22:10
10 forum posts
8 photos

Hi Robbo, Thanks a lot - The original plans by Edgar T. Westbury showed the valve gear at 90 degrees - I thought it was a mistake! I'll have a play tomorrow and report back...


Peter Benning01/02/2018 21:30:52
10 forum posts
8 photos

The Link was a great help and I have been able to adjust the eccentric strap to get the timing correct. I have tested with compressed air and it runs quite well...

I'm quite pleased that after nearly 59 years I have managed to complete it! It tested my engineering skills somewhat and I'm not sure they have improved much since I was 15; even though my whole working life I was employed as an "Engineer"

I'll post a few pictures next...

Peter Benning01/02/2018 21:47:41
10 forum posts
8 photos

How do you create an album and put pictures in?


JasonB02/02/2018 07:22:41
17885 forum posts
1955 photos
1 articles

Have a read of this which should explain how to do it.

Peter Benning03/02/2018 12:10:06
10 forum posts
8 photos

Thanks JasonB. Have created & Uploaded photos of how the steam engine progressed...

Peter Benning03/02/2018 12:26:20
10 forum posts
8 photos

final assembly.jpg

JasonB03/02/2018 13:32:27
17885 forum posts
1955 photos
1 articles

Looks good Peter.

I knew the Stuarts description was still about, you can read it here if you are still having problems.

Basically if you look at your engine from the flywheel side, have the crank pin nearest to the cylinder then the high (thickest) point of the eccentric should be at about 11 o'clock. This would be for anti- clockwise rotation.

Once this is done look at the valve as you turn the engine over and adjust the valve rod so you get equal movement each side of central.

Peter Benning03/02/2018 14:41:06
10 forum posts
8 photos

Thanks again Jason. Yes I have it running now and after seeing your video, I'm trying to upload a short video, via YouTube...

I think the picture here is before I had adjusted the eccentric strap and added the two missing steam chest bolts!

Once I realized that the steam should be starting to be cut off half way on the stroke and be ported to the other end of the cylinder, adjustment became easier. Of course had I been using real steam, that would keep expanding within the cylinder, as the piston transited.

A keen eye may have noticed that on the exploded view of the steam chest, I have missed the two ports to the cylinder. I had to send off for two 1.5mm and 2.0mm end mills from Japan to complete...

In the early 70's I was on a training course up on the west coast of Scotland and had a day trip on PS Waverley - I spent most of the sea journey in the engine room looking at the Triple Expansion Steam Engine! - Now that's a proper steam engine!

Brian H03/02/2018 19:14:40
1592 forum posts
104 photos

Congratulations on finishing your engine, it looks good. What's next? a triple expansion engine?


Peter Benning07/02/2018 20:27:35
10 forum posts
8 photos

Thanks Brian, sorry for delay in answering, but have been fine tuning (fixing) and tarting up to put on a presentation plinth, with brass plaque!!

I think a Triple Expansion Steam Engine maybe a bit too advanced and I would have to use real steam. I still find it difficult to understand that the largest cylinder, works on negative pressure... I have looked at modern videos of the Waverley and it seems to have been modified from when I was on it. At that time it had a large "banana" link, which allowed the crankshaft to change direction from "Ahead" to "Astern" almost in one revolution! Since the Paddles were fixed it was the only way of stopping and sort of steer... I see now it has "Feathering" Paddles, which would allow greater control.

I may try and go to one of the Model Engineering shows to get an idea for my next project. The trouble with living in West Wales, you are a long way from everywhere!


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