what's the minimum driving wheel flange in gauge 3?

geoff_nicholls

Western Thunderer
How much can I trim off a driving wheel flange, and still take the loco to G3 get-togethers?

I'm having the underframe of a J70 steam tram built, to run without skirts, (as per the prototype in BR days) because it would be just right for my layouts, and with Walschearts valve gear would be quite a crowd pleaser on Lea Siding.
However the scale wheelbase is 45mm + 45mm, and the wheels have arrived from walsall at 45.3mm diameter. I can take 1mm off the diameter to bring it down to G3 soc standard 2mm flanges, but could I get away with 1.5mm flanges? I'm sure that would be okay with my cliff Barker indoor track, but what about visiting other garden layouts? the extra space would help accommodate the guide bar support(is that the correct name? )
Does anyone out there have any experience, or thoughts? I'm hoping the axles will be sprung, if that helps.
 

unklian

Western Thunderer
I would have thought that with sprung axles 1.5mm deep flanges would be fine. The short wheelbase will also help. The published standards recommend 2mm maximum, with no minimum specified. The prototype is allowed to vary between 36 and 25 millimetres, which is about 1.6 to 1.1 millimetres in G3. The width of the flange along with wheelset back to back, is more critical for compatibility with others track I would have thought .
"guide bar support" will do, I knew what you meant, I think "motion bracket" is more correct perhaps. Would be nice to see a J70 with the correct number of wheels...
 

jamiepage

Western Thunderer
Geoff,
I can't offer the practical experience you need to prove 1.5mm flanges are ok on an 'average' G3 outside track.
However, you did also ask for thoughts. G1 standard standard calls for 1.5mm flange depth with sprung axles; this has turned out to be very accommodating of a variety of tracks.
The only practical difference between your J70 and an average G1 loco would be the lateral dimensions (track gauge/ Back to back etc), so the question is whether the difference in gauge substantially affects the flange depth requirement. I can't really think it does, to be honest, but regrettably have no expertise to give that any credibility.
 
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