Putting correct profile on someone elses wheels

[Jon LawesParticipant @jonlawes51698]

[Jon LawesParticipant @jonlawes51698]

I have a partially built 3.5 gauge Britannia which I'm currently working on. Only the main frames, front bogie and wheels have been made by the previous owner before they passed away; I took over from there. Most of my time so far has been redoing the work done so far; its been quite variable in quality.

The previous owner has machined the wheels with a good profile to the rim and shoulder, but the tread has been machined parallel. I understand LBSC thought this wouldn't be a problem but convention seems to say otherwise. Can I just shave the profile down to a 3 degree angle to the root of the shoulder or is there more to it than that? Am I just overcomplicating this?

[Neil WyattModerator @neilwyatt]

I'd guess the challenge will be lending in the radius in the corner. My thought is to use a button-nosed tool that fits the corner and cut outwards. the amount to remove won't be much.

Neil

[paul rushmerParticipant @paulrushmer83015]

Coning the tread should help centre the wheels on the track, the root radius is just as important. These two help stop the flange banging in to the side of the rail and improve ride. The root radius should be 0.050 inch but I use a broken No1 centre drill in a tangential holder sharpened to the appropriate angle to cut as a form tool (0.062 radius) this works fine on our multi gauge track. Both wheels on an axle should be the same diameter or they will try to go round in circles.

Hope this helps Paul

[Jon LawesParticipant @jonlawes51698]

Useful, thank you chaps. I guess I'll just make a stub mandrel to run in the centre of the wheel, and cut a tool to the right profile. Thank you.

[Brian OldfordParticipant @brianoldford70365]

Another point is to ensure all coupled wheels are the same diameter. To give you some idea of the accuracy required full sized BR practice was to ensure all wheels on the rolling diameter were inside a 0.010" window.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian Oldford on 03/09/2018 15:52:54:

Another point is to ensure all coupled wheels are the same diameter. To give you some idea of the accuracy required full sized BR practice was to ensure all wheels on the rolling diameter were inside a 0.010" window.

.

Scale that down and it's 'instrument making' on the model

MichaelG.

[Neil WyattModerator @neilwyatt]

Intersting.

On an 08 shunter (coupled wheels) the allowable variance between wheelsets is indeed 0.25mm.

For some types (uncoupled) it can be as high as 25mm.

Search MT288 wheelset standards PDF

The number of dimensions measured is bewildering!

Neil

[Jon LawesParticipant @jonlawes51698]

I've given the wheels 3 degrees, on closer inspection they already had a subtle profile, I'd guess at 1.5 to 2 degrees. My reprofiling took a skim off and I've done my utmost to keep them all the same size. Time will tell. Still need to make the tender and trailing truck wheels from scratch!

[Brian OldfordParticipant @brianoldford70365]

3 degrees or 1 in 20 is what most use.

[duncan webster 1Participant @duncanwebster1]

There is an SMEE standard for wheel profiles in various gauges. It appears in Tubal Cain's 'Model Engineer's Handbook@. I mean the real Tubal Cain (TDWalshaw) not that American upstart.

[paul rushmerParticipant @paulrushmer83015]

There is an error in this table if using metric units the 3 1/2 back to back is given as 83mm, this should be 83.35mm. Not a lot I know but worth knowing.

Paul

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