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Scott Vacuum Engine

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NJH27/07/2010 20:26:19
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I changed my (imperial) lathe recently and the new one is metric. It was a fairly cheap and easy process to upgrade my measuring equipment from imperial - but not so my brain! I thought therefore that a quick (and not too expensive) project would be good and I selected the Scott Vacuum Engine. I explained the principles of its operation to my 10 year old grandson, before he departed for a holiday to Australia, and then set to work. 

Construction was straightforward and I took care to get good fits and a smooth action. As advised I honed the cylinder – a first for me - and all looked well and turned over freely and smoothly. Then I tried to get it going………..

Fiddle with timing – adjust spring pressure – adjust and reposition flame at cylinder inlet port. Perhaps it takes a bit longer to stop with the flame applied  - or maybe I am kidding myself. So far I have come across four people who have made this engine but they all say they can’t get it to run either! Now to some extent it doesn’t matter as my objective was to gain familiarity with my lathe and this has been achieved. However has anyone got one working and, if so, can they please supply a few face saving tips for Grandad?

 

Here’s hopeful

Norman

Edited By NJH on 27/07/2010 20:27:59

Ian S C28/07/2010 13:31:30
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7468 forum posts
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Hi Norman, now the feeling, I'v got two vacuum engines, one the Minature by Jan Ridders I have been unable to get going. The other in a drawing by Edgar T. Westbury in the Model Engineer of the 17 april 1970, its called the Atkinson air engine. It goes well but took a long time to get that way, at first it needed an extra flywheel, extra aluminium fins jambed into the existing fins on the cylinder, and it needed quite a big gas flame. Now it runs with the flywheel in the diagram, and uses a meths burner. I'll try and put the diagram in an album- I'm just getting into this, its a bit hit and miss for now. With these engines, and Stirling engines patience is the key. Ian S C
John Wood129/07/2010 09:51:51
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Now here's a familiar topic! I too built the Jan Ridders engine from the plans in ME and, although I can get it to fire it just won't keep going. I put it aside in frustration several months ago but am thinking of getting it back out and having another go. I also have a half-scale Hercules Economy engine from LE Services and have had the devil of a job to get that going as well, so far it will start sometimes, usually only when its cold (!) but I cant get it to run for very long before petering out and I cant yet get reliable starting. It's just the same on Butane. Then there's the governor to set up - not even gone there yet.
 
I have been thinking of the Scott engine recently since, like you Norman it looks quite easy to construct etc but, I really do need something which works so I am having second thoughts now. There will be one at the Bristol exhibition next month on the Poly stand which I shall have a look at but I'm getting a bit put off now.
 
I do find there are any number of builders like us with similar problems so it would certainly be helpful if others who have gone through the same traumers and have succeeded in the end, to tell of their experiences. The only trouble-shooting gen I see just covers the usual; "make sure the spark is OK, check the timing carefully, make sure petrol is getting to the carb, check the valve seatings, check for leaks around the head etc" all fairly basic stuff but I guess there can be a lot more to the subject.
 
I'm looking out for a 'real' open crank hit and miss engine at the moment, just so I have at least one engine which works and I can play with whilst soldiering on with the home builds.
 
Ian, I firmly agree about needing patience with Stirling engines and it looks like similar patience may be needed with i/c's as well.  Lets all keep at it though and I, for one, will certainly report any successes on this forum.
 
All the best
John
Ian S C29/07/2010 10:30:11
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7468 forum posts
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If any ones interested, I built the one in the diagram in the album just using the scale next to it. The cylinder is steel with a cast iron piston, the cylinder head is cast iron, as are the valve guides and valve.The flywheel is fabricated fom steel, asis the cam/crank disk. the rocker arm is aluminium, and the con-rod at the moment is steel, but would be better if it was aluminium. he base is steel.
John I'v got an own design open crank 4 strokeunder way/under bench(at moment), at the moment  the patience is required while I spend time thinking about it, then it will be trying to get it going. Ian S C
NJH29/07/2010 14:12:41
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2314 forum posts
139 photos
Hi Ian The Atkinson engine looks very similar to the Scott engine I built except that mine is water cooled. The valve is made from a block of graphite and my flame is from a propane burner. From your drawing it seems that the flame is directed straight into the port where as mine is angled 45 deg. upwards towards the port. The flame is yellow, about 15mm wide and may be adjusted up to (about) 50mm long. ( see I am beginning to get metricated!) As a starter then how does your flame appear? -  I'm sure I'll have many more questions!
 
John, I too will be at Bristol next month beating a path to Polly Model's door  - maybe between us we will sort some answers. It is an interesting and quick project - a bit different from my previous steam ventures.
 
Regards Norman
Ian S C30/07/2010 10:34:52
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7468 forum posts
230 photos
Norman, when I first got it going I used a gas torch, just aimed it in the hole at an angle pointing toward the center of the interior of the cylinder, but now that it runs on meths the wick comes to about 10mm below the hole. It looks quite good if its run in the dark, and if the flame is kept close to the head it does'nt blow out. At the moment it is sitting on a mechano frame with wheels, and has a friction roller on the crankshaft. It can propell its self at quite a rate if I get every thing adjusted just right, I'll get it out next time my nephew brings the kids out this way. Oh the burner- I make mine as I found in Vol 1 of Model Engineer, a little container with a wick tube as usual, but the wick is made of a bundle of reasonably fine iron wire (florists wire), not sure the size, proberbly 26 or 28 swg. it lasts for ever, just pack the wire in the wick tube fairly tight. Ian S C

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