Miss Prism Posted March 16, 2013 Share Posted March 16, 2013 I'm without my early GWRJs at the moment, so could someone with GWRJ#8 look at the big GA of the 57xx and tell me what the wheel crankpin throw is, please. (AG says 9.5", Ultrascale say 10", and I'm not sure whether the old Sharman wheel spec book can be trusted!) Link to post Share on other sites More sharing options...
Guest dilbert Posted March 16, 2013 Share Posted March 16, 2013 It's 10"... Link to post Share on other sites More sharing options...
Miss Prism Posted March 16, 2013 Author Share Posted March 16, 2013 Thanks. I ought to do a note to Colin Seymour (Alan Gibson) saying that his G4855W wheel is incorrectly listed. But then I spotted his G4849B 4' 1.5" spoked wheel is also listed as a 9.5" throw. Hmmm. What does the 2021 drawing in GWRJ#20 say? I just knew this was going to be trouble... Link to post Share on other sites More sharing options...
buffalo Posted March 16, 2013 Share Posted March 16, 2013 I'll have to go back and fix my blog entry... Unfortunately, the drawing in GWRJ 20 only shows the body of the pannier version. Nick Link to post Share on other sites More sharing options...
Miss Prism Posted March 16, 2013 Author Share Posted March 16, 2013 Castle - do you have any contacts in the Kent & East Sussex Railway who would know what the throw on 1638's wheels is? Link to post Share on other sites More sharing options...
Castle Posted March 16, 2013 Share Posted March 16, 2013 Hi Miss P, Sorry - no connections for the K&ESR. The best I can do is measure the throw on the 8750s for you at Didcot later in the week if this is of any use? All the best, Castle Link to post Share on other sites More sharing options...
Kev_Lewis Posted March 16, 2013 Share Posted March 16, 2013 Slaters 7mm scale wheels for the GWR 2021 class are listed as being 10" throw. As are those for a 57XX. Link to post Share on other sites More sharing options...
Miss Prism Posted March 16, 2013 Author Share Posted March 16, 2013 Castle - thanks for the offer, but I think we're now happy about the 57xx crankthrow. Kev, thanks - that makes sense. Link to post Share on other sites More sharing options...
Castle Posted March 23, 2013 Share Posted March 23, 2013 Hi All, Having consulted the experts and applied a little common sense. The drawing for the 16XX shows a stroke of 24" therefore the crank throw has to be half of that of the stroke so it should be a 12" throw. All the best, Castle Link to post Share on other sites More sharing options...
buffalo Posted March 23, 2013 Share Posted March 23, 2013 Having consulted the experts and applied a little common sense. The drawing for the 16XX shows a stroke of 24" therefore the crank throw has to be half of that of the stroke so it should be a 12" throw. Yes, that's right for the inside driving cranks on the axles, but not necessarily so for the crankpins on the wheels. 24" stroke cylinders with bores between 16" and 171/2" have been common to almost all GWR large 0-6-0T since the 302 class of 1864. Nick Link to post Share on other sites More sharing options...
asmay2002 Posted March 23, 2013 Share Posted March 23, 2013 Hi All, Having consulted the experts and applied a little common sense. The drawing for the 16XX shows a stroke of 24" therefore the crank throw has to be half of that of the stroke so it should be a 12" throw. All the best, Castle On an inisde cylineder loco the outside cranks on the wheels don't have to the same as the inside cranks on the axle and in some cases weren't, hence, I think the original poster's question. Link to post Share on other sites More sharing options...
buffalo Posted March 23, 2013 Share Posted March 23, 2013 ...hence, I think the original poster's question. Yes, Andy, the origin of the question was a discussion Miss P and I had on my blog where I was making a simple jig to drill the crankpin holes in the older type of Gibson wheels. These have a small dimple marking the position rather than a moulded hole. I'd used the 91/2" figure from the Gibson catalogue but noticed a slight mismatch with the dimple. Miss P had seen the 10" figure elsewhere, but neither of us knew which was correct. The result was that both my 57XX and 8750 now have a (roughly) 0.167mm error in the throw I can live with that but can now correct the original text so that others are not mislead. Nick Link to post Share on other sites More sharing options...
Horsetan Posted March 23, 2013 Share Posted March 23, 2013 Crankpin drilling jigs would also be useful for correcting a crankpin throw. I think Dave Bradwell includes one in his K1 kit... Link to post Share on other sites More sharing options...
Castle Posted March 23, 2013 Share Posted March 23, 2013 Hi All, And of course you are after the crank pin throw and not the crank throw... Note to self: read O.P. CAREFULLY in future. I had the right answer, it was just to the wrong question... Oh well, back to the drawing board! All the best, Castle Link to post Share on other sites More sharing options...
Castle Posted March 23, 2013 Share Posted March 23, 2013 Hi All, Right, gone back to an expert and a couple of drawings that we had forgotten we had to hand and I would agree with Dilbert et al on it most likely being a 10" throw on the crank pin on the wheel. This is scaled off a couple of different drawings but my dodgy maths seems to come out pretty much the same every time. 3.33mm in 4mm scale which is 10". It would be best to measure the real thing of course but that is why we are in this position in the first place! Sorry for the earlier, self inflicted confusion! Where chaos reigns supreme, Castle is somewhere near the middle of it... All the best, Castle Link to post Share on other sites More sharing options...
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