Jumbo Driving Wheels

How to do it, advice sought and offered.
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JimG
Posts: 257
Joined: Tue Aug 14, 2012 11:15 pm

Jumbo Driving Wheels

Post by JimG » Mon Feb 18, 2019 12:26 pm

I'm just about to start making the drivers for a Jumbo and I'm looking for some confirmation about the balance weights - specifically those on the centre axle. I can see from many pictures that the balance weights on the front and rear axles were relatively small and square ended across the spaces between three spokes opposite the crank pin. But it's the balance weight on the centre driver that I can't quite see enough to confirm what's actually there. The best picture I can find is Plate 70 in the Jumbo book and it looks as though the weights fill in the spaces between the three spokes in line with the crankpin and extend right up to the boss. It also looks as though the weights are flush with the spokes, unlike the front and rear weights which are proud of the spokes.

Jim G.

jimwatt2mm
Posts: 632
Joined: Fri Nov 16, 2012 5:36 pm

Re: Jumbo Driving Wheels

Post by jimwatt2mm » Mon Feb 18, 2019 3:58 pm

Hi Jim,

I have three postcard photos of jumbos, 305, 335 and 748, all with the coupling rods in the standard bottom centre position, but in all three cases the centre balance weight would appear to be as you describe.

Jim W

Alan K
Posts: 339
Joined: Mon Aug 13, 2012 9:41 pm

Re: Jumbo Driving Wheels

Post by Alan K » Mon Feb 18, 2019 8:11 pm

Hi Jim

Have a look at George Russell's item on Caledonian Jumbos in TL33. He summarises the features of the Drummond, Lambie and McIntosh engines. The Drummond and Lambie ones seem to have been as you've given, but he says that some McIntosh engines had crescent shaped balence weights. I looked at the pictures of Jumbos in 'LMS Locos Vol 3' and found ex 550 (on p88), ex 1318 (on p90) and ex 563 (on p94) with crescent shaped weights on centre drivers. Admittedly these are pictures from LMS days, but there are plenty of others with 'your' (ie Drummond) pattern!
Looks like if you stick with Drummond or Lambie then you're OK, but for McIntosh engines, get out the photos....!

Alan

JimG
Posts: 257
Joined: Tue Aug 14, 2012 11:15 pm

Re: Jumbo Driving Wheels

Post by JimG » Thu Feb 21, 2019 4:40 pm

Jim W. and Alan,

Thanks for the confirmations. I managed to dig out True Line 33 and found the paragraph in the Jumbo article which fully describes the centre driving wheel weight. The Jumbo will be a Drummond one with his boiler fittings and a Stroudley style tender. If I manage to get to a second one, that could be a MacIntosh one with Westinghouse fittings and maybe crescent balance weights.

Is there a good drawing of a Westinghouse pump available?

Jim G.

Alan K
Posts: 339
Joined: Mon Aug 13, 2012 9:41 pm

Re: Jumbo Driving Wheels

Post by Alan K » Thu Feb 21, 2019 7:58 pm

Jim
Can't help with a Westinghouse pump drawing, but I think the problem you may have is that there seems to have been several different varieties. Sure they all look alike and have basically 2 cans mounted on top of one another, but the geometry seems to vary, the 'bits' on top can be different etc etc. That may not matter at all for the smallest scale (no disrespect Jim W!) and may only be mildly annoying for the 4mm brigade, but for the bigger scales like yours it might be more of a problem...!

Alan

PS I got bumped off with a 'you must log in' message the first time I did this post even although I was already logged in, so it's still happening!

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