Different materiel

This topic has 5 replies, 5 voices, and was last updated 16 March 2012 at 17:49 by MICHAEL WILLIAMS.

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12 March 2012 at 15:53 #87065
brian bruun
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@brianbruun25047
hello fellow builders.

I almost started building the lsbc virginia steam locomotive. Before i am going to do that i am trying find materiels that i suiteble for it. But i have a little problem i am from denmark and we use the metric system. and the frames on the drawing is 1/4 thick that is 6,35 mm here is my problem most of the materiel i can get is in metric and most of the time it is a little thinner then the imperiel messure back to the frames mine is only 6 mm thick its 0,2362 inch thick wil it be a strengt problem or wil it do?

regards bab
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12 March 2012 at 15:53 #6032
brian bruun
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@brianbruun25047
12 March 2012 at 16:07 #87067
JasonB
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@jasonb
It will do the job, you just need to take into account the thinner material and make all the cross pieces slightly wider so the outside width of the frame ends up the same overall size.

In fact even here sheet metal has to be bought in metric thickness so as the frames are usually cut from sheet rather than using flat bar we have the same issues.

J
15 March 2012 at 19:36 #87288
nigel jones 5
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@nigeljones5
hi…on the face of it almost all mainstream uk suppliers are metric, but if you find a bespoke model engineering shop im sure they will supply both, they seem to here
16 March 2012 at 16:03 #87335
colin hawes
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@colinhawes85982
The only reason for originally specifying 1/4 inch must have been because that was the nearest standard size available. The normally designed factor of safety should make the difference between 1/4 inch and 6mm insignificant if you allow for the change in spacing. Colin
16 March 2012 at 17:49 #87338
MICHAEL WILLIAMS
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@michaelwilliams41215
Hi Brian ,

Virginia is a BAR framed engine . Virginia has no specific prototype but most American engines of similar type had frames made of standard 4 inch thick bar components . This is where the 1/4 inch frames specified on Virginia come from – 4 inch scaled down .

In most full size engines this 4 inch dimension controlled the sizes of many other standard interchangeable parts .

Just for example the axleboxes either ran bare in slots in the frames or in standard cast guides which themselves slotted into the frames horn guides .

Another example is the common cylinders and saddle assembly (GWR style) which just slotted over the two 4 inch frames at standard spacing .

Model frames made of much thinner material would probably be strong enough but would spoil the look and the character of the thing completely .

Why not follow the proyotype construction and make the frames from square bars and milled joining pieces . Since these frames are mostly open space a well thought out cutting plan would mean that some of the square bar assemblies could actually be made in one piece and milled all over .

Michael Williams .
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