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Engine Identity

Twin vertical labelled Start 6A - but is it?

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Journeyman16/10/2016 11:29:14
1174 forum posts
236 photos

Whilst at the Midlands MEX I took this picture of an engine on the Hereford SME stand which I posted on my website. A comment suggested that I had mis-identified the engine. The display label says: Stuart 6A to a John Bertinat design.


Looking at Stuarts website the 6A is a compound the commenter suggested that the photo might be of a 5A but the 5A is a singe vertical. I cannot find any info about this particular John Bertinat engine although he has designed quite a few others.

Does anyone recognise the engine or know of this particular design variation. It looks to me like two 5A's back to back or similar. Unfortunately I can't scale the image easily as there are no size references in any of the photos I took but it is probably 200mm to 300mm high from memory.

Thanks. John

Edited By Journeyman on 16/10/2016 11:33:27

JasonB16/10/2016 13:17:05
23042 forum posts
2769 photos
1 articles

The 6A did not have A frame standards, had a single cast standard with cross head guide for each cylinder and turned columns on the opposide side. At one time Stuarts stopped doing the 6A and the Swan (twin) which did have A frame standards so its is possible the Bertinat was a way to get a twin when none was available using 5As.

The finish on the "cast" base looks a lot smoother than the rest of the cast parts so could well be fabricated.

Edited By JasonB on 16/10/2016 13:18:08

Neil Wyatt16/10/2016 14:19:04
19076 forum posts
736 photos
80 articles

Perhaps it's based loosely on Bertinat's triple expansion marine design, but using Stuart frame castings?


Bazyle16/10/2016 17:30:52
6381 forum posts
222 photos

Jason has it I think. Dug out my 1980 catalogue and it looks like a Swan which seems to be a 5a x2 with a smaller flywheel and no sub-base to raise it, same bore and stroke at 2 1/4 x 2. The cygnet seems to be a 5a really maybe with a modified crankshaft to drive the air pump.
There was a 6a on the Stuart stand which is 5 in taller, 2 1/4 & 4 x 3in stroke. I got waylaid by the sign on it in my note to you John and forgot about the Swan.

Journeyman16/10/2016 18:59:14
1174 forum posts
236 photos

Ah, things become clearer. I have never heard of the "Swan" before that would make sense, I think the Bertinat design is quite old so he may indeed have used the A frame castings in his design.

Thanks. John

V8Eng16/10/2016 20:17:24
1730 forum posts
6 photos

When I was at the show the card had been altered by hand to say "Swan".

Certainly looks very like a Stuart Swan (IMHO).




Edited By V8Eng on 16/10/2016 20:24:15

Edited By V8Eng on 16/10/2016 20:26:58

Journeyman17/10/2016 08:57:27
1174 forum posts
236 photos

Many thanks gents. Definitely a Swan which is indeed 2 back to back 5A's. Armed with the right name I found several pictures to confirm the identity. An article on The Model Engineering Website has photos and a description. I can still find no definitive information about J.P. Bertinat's involvement in the design. There is an entry in the ME index for 1980 issue 3646 page 1457 which shows "J.P. Bertinat's Stuart Turner Swan Engine" but the article is about the Warrior engine. I have no access to the magazine though to check.

V8Eng, someone at the show obviously recognised the engine after I had taken my photo, thanks for the update.

Bazyle, thanks for the original "heads up" I will make the necessary changes on the website.


JasonB17/10/2016 13:08:37
23042 forum posts
2769 photos
1 articles

Its not a true swan as it does not have all the pumps etc just a twin vertical in the style of the swan, as I said probably something JB came up with as a substitute for a swan type engien when it was not being produced.

Journeyman17/10/2016 16:50:00
1174 forum posts
236 photos

Rumaging in the workshop I found this:-


It seems that you could get the engine either with or without the feed pumps, air pumps, lubricator etc.
In 1988 it would have cost:-
Basic engine - £260
Condensing Installation - £650

Well worth the money. You could also get the single version the Cygnet.


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