Wheel/ Tyre profiles

[Half centreParticipant @halfcentre]

I was wondering if anyone had any tips on ways to help with accurately and reproducibly cutting the required wheel/tyre profile for a 3 ½ inch gauge loco.

This link describes making a profile tool for a smaller gauge model. I am not at all sure if this would scale up without bringing my lathe to a stop! Perhaps a partial profile tool covering the flange? The 3 degree coning is straight forward to cut separately?

Any ideas gratefully received.

Martin

[Half centreParticipant @halfcentre]

Accurate and reproducible cutting

[Sub MandrelParticipant @submandrel]

Hi Martin, thi is how I machined mine.

First I roughed out the flanges of all four wheels, using a mandrel turned in place in the 3-jaw chuck.

Then I sharpened up an HSS tool, like a standard knife tool but with a significant nose radius.

I turned the top slide to give the 3-degree taper of the cone.

I then fitted the tool so the cutting (left) side of the tool was at the flange angle.

For each wheel in turn I then thinned down the flange so it was the right thickness at the top of the flange (before rounding off) The nose of the tool then created the root radius, using the cross slide to make sure the depth was consistent even though the cone was not yet turned. I then used the topslide to create the cone angle until it blended in nicely at the root, while keeping an eye on the outside diameter, just in case.

This may sound hit and miss, but using a saddle stop and always starting with the top slide in the same place made sure the initial turning of the flange was OK.

I didn't suffer chatter on the flanges, but the wheels are only 2 1/4" diameter and teh depth of the flange is quite small in 3 1/2G.

Neil

[Half centreParticipant @halfcentre]

What a terrific and detailed reply. I have tried several techniques and always found the root radius the most difficult to cut reliably. I will have a go with a tool radiused (is that a word!) to 0.05". Its a very good idea to use the same tool for the flange angle and RR. My wheels are 3" – hopefully with plenty of cutting oil and very gentle feed I can avoid chatter – many thanks Neil

Martin

[Kerrin GalvinParticipant @kerringalvin72662]

Hi Martin,

If you can get a hold of back issues of ME check out the series by David Hudson on his trolley design. He figured out how to profile the tread to the form used in full size, sorry not at home so can't give you issue numbers, he gives drawings for making the tool to do it. I've made a trolley to his latter design & profiled the wheels as he described & boy do they self center, track & ride smooth……just my 2 cents worth. Oh his design is for a 5" trolley but says there is no reason why you cannot Use it on a loco.

Buy the way I made my trolley duel gauge, 5 & 71/4, & have run may k's on 71/4 & they work great

Cheers Kerrin

[Sub MandrelParticipant @submandrel]

Martin,

It's interesting thet both LBSC and even Maertin Evans recommended straight profiles for 3 1/2" gauge, although Martin conceded defeat in the face of much evidence that coning in 3 1/2 gauge was worth it. I think it was Dennis Monk who set up a convincing demonstration using two otherwise matched axles and simply showing how the coned one would roll much further!

That said, I'm not sure how much difference David Hudson's approach would make on very small wheels, however, the device he designed for guiding the profiling tool would make the process of profiling straightforward and repeatable.

Neil

P.S. these are my wheels (as the teenagers say):

And the end result…

[Ian S CParticipant @iansc]

Martin, I presume your wheels are steel, you mention plenty of cutting oil and I was thinking that if they were cast iron, forget about the cutting oil, you proberly know about that, but someone may not. Ian S C

[Half centreParticipant @halfcentre]

Hi chaps – Thanks for the tip off Kerrin, I know someone who has back copies so I can hopefully track the article down. Nice model Neil – well done on the spokes, I know from experience what an effort they are to get right.

Ian could I pick your brains about cast Iron? I know of its self lubricating properties, but have little practical experience of using it in potentially high friction situations. In your opinion would it be possible to run cast iron pistons/rings inside a cast iron cylinder in a model loco without addition lubrication, would it still work with superheated steam? My model will be very much a prototype and I anticipate about 50psi with a simple loop/hairpin superheater in the smokebox (defiantly not present in the original ‘Royal George’! – but without a dome I would like to try dry the steam as well as add energy before letting it into the cylinders). I think the amount of superheat could possibly be described as ‘moderate’?

Martin

[Perko7Participant @perko7]

Interesting discussion. I need to turn up some 115mm dia wheels for 5in gauge to AALS dimensions and i am having trouble turning the tapers on each side of the flange. I've done the tread taper by setting the topslide to the right angle, but when i spin it the additional 90 degrees to turn the flange taper the carriage gets in the way unless i have an unreasonable overhang on the tool, which then causes too much chatter.

Is using a normal tool with the cutting edge at the correct angle the only option for these tapers?

Geoff P.

[duncan webster 1Participant @duncanwebster1]

I've turned quite a few wheels using exactly Stub Mandel's method. Works a treat. Biggest were 6" diameter, done on a ML7 which was not in the first flush of youth. Use a brazed tip carbide tool ground to the correct tip radius (no top rake).

You cannot achieve all the SMEE dimensions as they are not consistent. I'll post a sketch showing what I mean, together with a method of using a micrometer to measure flange thickness if you have to resharpen the tool, but I'm minding the grand daughter now so it probably won't be soon!

Edited By duncan webster on 09/04/2016 19:05:32

[Neil WyattModerator @neilwyatt]

Interesting to see this thread revive.

A thought I had recently –

Most 3 1/2" / 5" tracks are dual gauge.

As the smaller gauge's flanges run fine on the same track, why not use 3 1/2" gauge-sized flanges on a 5" gauge model to get a better scale appearance?

Is it because larger wheels are more likely to derail?

Neil

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