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Locomotive wheels

Simulating the tyres

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Trevor Crossman 104/10/2020 20:34:50
152 forum posts
18 photos

I have started to machine the wheel castings for my Salisbury and now seek the advice of our expert builders on two details.

1/ The drawings show the tyre tread to be parallel to the axle and the rim flange to be at 15deg. On other drawings and in the Martin Evans books I have seen a coning angle of 2 deg. and a flange angle of 20 Deg. called for. I understand the benefits of the coning and the need for relief between the rail and flange, but is there a great difference in the effect of the two sets of dimensions, and what do you do?

2/ Once again referencing the Evans books, it's suggested that a narrow line is turned on the front face of the wheel to simulate the distinction between the wheel and the tyre, but nowhere have I been able to find any sort of dimension as to how far in from the edge (which also has a small bevel) this groove should be formed. The wheels in question is 7 5/16" and the rims are 7" diameter with the face of the rim 3/8" wide. Would 7/64" be about right? I suppose that tyres are probably a little over an inch thick in real life and 5" gauge is roughly 1/10 I believe. It's a minor detail but one that I'd like to add and I definitely don't want to make these expensive castings look *wrong* when the beady eyes of the knowledgeable see it!!

Trevor

norm norton05/10/2020 10:27:17
141 forum posts
7 photos

I wish I knew what a 5" Salisbury was, but I apologise that I do not. If it is a very early engine the designer might be replicating a simple tread.

If you plan to run it on a club's 5" track it will be very worthwhile adding the cone angle, as they run better, and taking care over the gauge and back to back of the flanges, i.e. do not make them too thick. The 5" track should sit just at the point where the coned portion rises into a radius before the flange.

Type 'GL5 wheel standards' into Google to see the generally accepted UK standard for 5". It will also come up with other profile discussions.

As for the wheel/tyre groove you do not often see this on full size engines. You really need a photograph of a Salisbury to see how it might have been finished.

Norm

SillyOldDuffer05/10/2020 11:07:34
Moderator
6699 forum posts
1507 photos

This one from Kennions?

Can't the answer the question - out of my league!

Dave

IanT05/10/2020 11:35:54
1750 forum posts
164 photos

Nice loco SoD.

I cone all my wheels (in Gauge 3) - it's not hard to do and I think it looks better.

Whether there are other (technical) advantages to doing so (in models) I really have no idea - but the improved cosmetics are sufficient reason for me.

Regards,

IanT

Phil H105/10/2020 13:17:40
338 forum posts
40 photos

Trevor,

Tyre

This is probably not so helpful but it is what I have done because I had a very similar unanswered question some time ago about the 'tyre' for my Rob Roy wheels (3 1/2" gauge).

I simply machined into the face (front to back) as much as I dare before the cutting tool touched the spokes.(probably about 1/32". The diameter cut is about 3/64" (3/32" total) to reduce the wheel tread depth appearance. I was aiming for a little bit more on both and was using photographs from the net as guidance and most locomotive pictures I have seen show a very clear tyre. Like you, I was aiming for a scale 1" at least in both directions.

Tread

I have also seen 20 degree flange, 2 degree cone and 1/16" radius - so that is what I did. The book on Rob Roy suggests that the cone is not necessary because of the shape of most model tracks but it does suggest a 1/16" radius at the root.

Phil H

Trevor Crossman 105/10/2020 13:26:03
152 forum posts
18 photos

A final go at interrogating our mutual friend Google actually yeilded a result and I have been read that although it's really only relevant to much more modern locomotives and rolling stock than 19century items. It is British Railways RDDS MT288 and tyre thickness is, depending on the size and class of wheel, somewhere between 36-41mm . So for 5" g approximately a 1/10 of that I guess.

Norm , I see that SoD has posted a picture of the model in question, thanks for that Dave.

As Norm suggested I'll follow the Gl5 guide.

Thanks for your reply IanT, I don't have any problem with turning the cone/flange just a bit unsure of the best choice of angle. Apparently and unbeknown to this locomotive noobie, according to the document mentioned, more modern locomotives generally do not have separate tyres but are fitted with monobloc wheels.

Thank you for your replies.

Brian H05/10/2020 13:26:31
avatar
1971 forum posts
108 photos

Just had a look at Kennions site, what a superb looking engine. If only I did not have so many unfinished ( as well as unstarted) projects I could be very tempted.

Brian

Nigel Bennett05/10/2020 13:27:27
avatar
379 forum posts
11 photos

Definitely cone your wheels if you're thinking of running it. On my last three locos I've not had the bother of simulating the tyre - because I've fitted shrunk-on steel tyres as per prototype. I would imagine on a 4-4-0 like Salisbury you'd be fighting for adhesion anyway, due to the less than ideal weight distribution. Steel tyres confer a much better grip.

Speedy Builder505/10/2020 14:41:25
2187 forum posts
152 photos

STOP - Before its too late - Think about painting- if all machined surfaces are going to be bright, now may be the time to paint spokes and rims before the final polish of bright parts and quartering - just my opinion.

Peter Layfield05/10/2020 15:12:00
34 forum posts

I don,t think you could do any better than looking at the GL5MLA website and bring up the pages on standards, all the info you will need is contained in the wheel standard page. There has been a number of articles in M.E. over the years on wheel profiles, David Hudson and Dennis Monk were two members that did a great deal of work on the topic which were incorporated into the GL5 standards, look at the back to back measurement as well, which has changed since your drawings were produced

Trevor Crossman 105/10/2020 21:13:50
152 forum posts
18 photos

Thanks for your thoughts guys!

Peter​​ I've downloaded & printed out the pages that you mentioned and will work to those.

Nigel I'm impressed! Your last three locomotives!! I'll be lucky to get just my first one up and running and I'm not sure that I would be able to produce rolled and welded steel tyres with sufficient accuracy from steel strip and suitably large steel tube might be difficult to find for this size of wheel. Regarding the traction, or perhaps the lack of, I don't suppose that this loco is particularly powerful anyway with a 90psi boiler and a pair of 1 9/16th bore cylinders. I have been unable to find any reference or pictures of any examples of this Adams 4-4-0 other than the picture shown on the Kennions website, so I've no idea how it will perform.

Brian H​​​​​​ It is indeed very attractive and was chosen because the class of locomotive that the model is based on would have been familiar to my ancestors in the New Forest, Wiltshire, Dorset region .it was a choice between this and Combpyne.

Speedy, thanks for your caution but I never paint any model until all the building is done and I'm sure that I won't have to rework anything. I think that my one exception to my rule has been with unproven self designed flying models because if I didn't fuel proof them before test flying, an oily airframe was impossible to paint. With this loco though I do however spray every iron and steel component with acid etch primer as soon as it passes inspection to prevent rusting.

Thanks again one and all for your contribution, I'll get back to work on the wheels.

Trevor

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