# Conversion Option for your Accu Brittania?



## Pete Thornton (Jan 2, 2008)

_My sister lives near the NYMR and sends me photos occasionally. This is 71000 "Duke of Gloucester" visiting the railway a few weeks ago._










The Duke is the only class member - it was a testbed for features to improve the Brittania class - double kylchap chimney, caprotti valves, etc. Since restopration, it has been continually improved and now holds the record for climbing Shap Summit - I think!


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## tacfoley (Jan 3, 2008)

Pete - IMO it would be very difficult to make anything other than a cosmetic re-modelling of the 7P Britannia locomotive. For a start, the 'Duke' has three cylinders, as well as the Caprotti [rotary poppet] valve gear. The G1MC Britannia has slip eccentric operating where the third crank would be. However, as the external valve gear is cosmetic, perhaps a simple replication of the rotating parts of the Caprotti gear is not out of the question. Making it, on the other paw, is another thing. 

tac 
www.ovgrs.org


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## iceclimber (Aug 8, 2010)

Isn't that a 'Clan' class 7?


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## tacfoley (Jan 3, 2008)

Posted By iceclimber on 13 May 2011 11:28 AM 
Isn't that a 'Clan' class 7? 
Nossir. It is the unique BR Class 8P. Only the one was built as a possible precursor to improving the Britannia Class locos, but it was a frightful failure in its original form. It took a total rebuild and restoration over 13 years and the correction of a number of faults to get it into the shape you see in Pete's photo. It also cost three marriages, I'm told. Read all aboit it on the 71000 society's webpage.

The Clan's were a lightweight version of the Britannia - made specifically to run on the lighter lines in Scotland. 

Most folks would be fooled if you simply made a non-operational cosmetic set of external valve gear for the G1MC Britannia - as I noted before, all the actual valving is done inside the frames. 

tac
http://www.ovgrsd.org/


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## iceclimber (Aug 8, 2010)

Thanks Tac, 
I didn't have my book on the britannias handy. Back when I was really interested in getting a Britannia I bought two books (still very good to have as I still like the Britannia).


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## rwjenkins (Jan 2, 2008)

Not that it would necessarily be practical in this case, but has anyone ever made a working Caprotti valve gear in gauge one? I'm thinking ambitious individuals here, certainly can't think of any manufacturers.


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## David Leech (Dec 9, 2008)

Richard, 
This was asked before some time ago, and my response at the time went something like this: 
In an old G1MRA Newsletter there is a write up about how to make a working rotary poppet valve system, but I was never able to ascertain if the writer did indeed ever make it, or if so, how well it worked. 
So, I don't have an answer for you. 
I think Ryan added some information, so perhaps he can remember what he said. 
All the best, 
David Leech, Delta, Canada


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## tacfoley (Jan 3, 2008)

THIS is the description of the Caprotti valve gear as applied to British locomotives - 

http://www.dukeofgloucester.co.uk/?page=British Caprotti Valve Gear 

I think you'd agree that it would take some genuine modern-day micro-engineering to make a working Caprotti gear in Gauge 1. To tell the truth it makes conventional valve gears like Walschaert, Heusinger, Baker, Cossart and Stephenson look as though they were products of the stone age. 

I'm pretty sure that a watch-maker could make a good try, but as Mr Leech notes in his post, we have yet to see any results of what may have been wishful thinking. 

tac 
www.ovgrs.org


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## Pete Thornton (Jan 2, 2008)

However, as the external valve gear is cosmetic, perhaps a simple replication of the rotating parts of the Caprotti gear is not out of the question. 
I might have guessed someone would think abut real valve gear . . 

I was just thinking it would make a neat cosmetic project!


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## tacfoley (Jan 3, 2008)

Posted By Pete Thornton on 14 May 2011 10:05 AM 
However, as the external valve gear is cosmetic, perhaps a simple replication of the rotating parts of the Caprotti gear is not out of the question. 


I might have guessed someone would think abut real valve gear . . 

I was just thinking it would make a neat cosmetic project! 

Sure it would, but even non-effective Caprotti valve gear is whirling around like a dervish on LSD. Have you SEEN it in action? 

Lots of whirling rods and shafts and miniature couplings....see from 00:37 of this clip...

http://www.youtube.com/watch?v=bxvh...re=related

tac
http://www.ovgrs.org/


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## CapeCodSteam (Jan 2, 2008)

tac, thank you for that video. Now it finally all makes sense to me.


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## Pete Thornton (Jan 2, 2008)

but even non-effective Caprotti valve gear is whirling around like a dervish on LSD. Have you SEEN it in action? 
I have to confess I haven't, as far as I know. I was wondering how the drive gears could be made to function at the axle, but that little universal looks like a bigger problem!


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