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Brian Camps
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Joined: Tue Jan 29, 2019 2:13 pm


Post by Brian Camps » Fri Feb 01, 2019 11:24 am

has anyone that has built speedy had any problems with the valve gear? we built it using the don young modified valve gear.it does run but the exhaust seems to be a beat missing it runs better with the drain cocks open soon as you shut them it seems to slow it down like the exhaust is not getting away only on one cylinder anybody got any clues as what is wrong with it.i should have stuck to slide valves
norton norm
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Joined: Mon Jul 07, 2014 6:32 pm

Re: speedy

Post by norton norm » Fri Feb 08, 2019 9:48 am

Hi Brian

If you have the interest in solving it, the best answer is to gain an understanding of Walschaerts, get all the dimensions from YOUR Speedy, and put these numbers into a spreadsheet and simulator. I did this to find out how my Britannia should be configured, and in the process found an error in the original Perrier design.

It was interesting to do and just needed a bit of maths. The tricky bit is finding out EXACTLY where the expansion link (edit - wrong word!) bracket is mounted with respect to the axle centre and cylinder centre line. I used Don Ashton's spreadsheet (available from his website) to see if all the dimensions made sense. Then I put the numbers into Bill Hall's simulator to see it running and get all the valve event timings.

I understand that Speedy is a compromise of design because it is compressed in length giving steeper motion angles. However, I feel that even a bad design will still run in full gear - it is when you 'notch up' to bring the die block to the middle that a poor design stops running. If all your parts are exactly to Don's drawing then just check that the valve bobbins are moving at the right times. If one of them is opening the steam inlet say 0.050" early then you might get the symptoms you describe of it needing the drain cocks open. If you built it all then please note that the bobbin length has to be accurately related to the length across the outside edges of the transfer ports. Get that 0.050" wrong and same problem.

Best wishes, Norm.
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Re: speedy

Post by Lucas » Fri Jun 12, 2020 4:17 pm

Hallo Brian
This is Dr. Johannes Grabsch, GL5 Member, German by Origin, now living in Valkenburg/LB in the extreme south of the Netherlands.

Please forgive me for answering later than late....
Never noted this question before ...
I do own "Otto" a SPEEDY that was originally built by Bernhard Walker, clubmate of mine at the West Riding Small Locomotives Club in Leeds, were we once lived. I inherited that wonderful Loco.

There are several problems associated with SPEEDY besides the Valvegear.
I have changed a number of things on the SPEEDY:

1 Improved the water system in an effort to keep the water on the loco cool(er)
2 Added a drive pump
3 Changed the setup from 2 injectors to 1 injector/drive pump with adjustments on the pipework
4 Modified the Smokebox: I added a sleeve in the Stack/Pettycoat, so that the exhaust fills the stack (silly LBSC mistake)
i.e. reducing the inner diameter of the stack
5 Relocated the whistle
6 Changed some piping in the cab
7 Changed grate, removed ashpan as the system as per drawings restricts air flow.

The loco has the unusual valvegear of the original, and I can confirm it works perfectly. Sadly Bernhard died before he could tell me the hidden secret in the valvegear, that many builders simplify to an (ugly) Walshearts. He told me though that (as a railwayman) he travelled to London to take measurement and he compared these to the Original drawings kept in the York Museum. And he changed one pin to be a tiny bit excentric - but I do not know which one it was.

The unusual valvegear of the original is a determining feature. Building a bread & butter Walshearts in a model GWR 1500 is something like throwing acid onto a Rembrandt painting. I would try to recreate the original.

I do have the Orignals drawings, large scale photos of Otto and a large percentage of all pictures of that loco ever published on the internet.

There is a story going on https://modeleng.proboards.com/
The author of that story is a bit wierd, he does not listen to any hint and builds truely to scale, inclusive correct scale the checker plates on the floor of the cab. My hunch: this loco will run maybe once and the disappear in a museum...

Kind regards
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Re: speedy

Post by Scrat » Thu Jun 25, 2020 12:53 pm

Hi Johannes,

your link only leads to the top page of the forum.
Can you give us a link directly to the topic?

Best regards

Matt Fowles
Engine Driver
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Joined: Wed Dec 26, 2018 10:06 pm

Re: speedy

Post by Matt Fowles » Tue Jun 30, 2020 11:32 am


it is here, on the general chat page. It is a very impressive bit of modelling and engineering.

I must go through the drawings for my "Speedy" and see what valve gear variants are in there, I assume it was built to the Don Young modifications- I know it's not pure LBSC. I remember helping the builder set the timing many years ago and after much patience we got a lovely even beat out of it. Some 20 years later it's not quite so smooth and I should probably repeat the exercise- I just wish I could remember how we did it but I was only 12 or 13 at the time!
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