Wheels to Axles - locomotives

I'm putting this in beginners because I feel I should know this but am having trouble finding reference to it anywhere.

On model live steam locomotives, how are the wheels mounted to the axles? Is it just an interference fit? As the drive is applied directly to the wheel and not via the axle I can understand this working but feel there should be more to it than that? On the Britannia rolling chassis I have the wheels are not exactly a loose fit on the axles but they can be removed by hand without any tools. Obviously any permanent method of fixing would make maintenance harder but I don't see models using visible keyways or similar?

I realise its a bonehead question.

As a newbie and still learning questions like this are a bonus. I think I know the answer but will wait for the experienced among us to answer at least it will also help me in the future

In the past they were usually pressed on. These days it's usually a close fit plus a high-strength retainer, which makes quartering driven wheels a little less fraught.

Neil

I'd suggest using Loctite 638 (other retaining compounds are available).

Mark.

.

Me too [especially as I have it in stock]

... but I think Neil is being honourably even-handed.

MichaelG.

Edited By Michael Gilligan on 14/08/2018 10:29:51

I had a feeling that was the modern way of doing things, thanks. I've even got some from my last stationary engine, so that's all good, though I won't need it for a few years yet!

Thanks to all who replied.

I dare not use the L-word qualified by a number or not!

I got chucked out of B&Q for going round with a sharpie writing 'retainer' on everything...

Neil

i have used 'a well-known brand of retainer' to aid in keeping my push-fit wheels on the axles, but plan to add pins for additional security, either in holes drilled longitudinally into the joint between wheel and axle or holes cross-drilled from behind through the wheel boss and axle.

.

Would that have been a Sharpie, Neil ... or just some generic fibre-tipped writing instrument being passed-off as the real thing ?

MichaelG.

Surely the real thing would be the aluminium bodied 'FloMaster' pen my infant school teacher used nearly 60 years ago? I can still recall the smell of the ink (no H&S issues then!) and the appalling squeaking it made as she wrote with it!

Does this mean we'll stop writing 'I machined it on the Myford' and just use lathe instead?

From looking at a loco, an Evening Star I noticed that a skt. head screw placed in the join between the axle and driving wheels. Easy to get out with a positive lock up. This would have been a Skt head screw with an extended pin like end. This need not be done until all is complete and the chassis can freely roll.

I think Clive Hartland is referring to what is often known as a Dutch key with half the thread in each component. Given the inevitable thread clearances and the probably unquantifiable distribution of tightening loads between each component I often wonder what the actual strength of such threaded keys is when compared to more conventional keys. Or even a simple round pin held in place by a bolt and washer. Whenever I've tried to think rationally and thoroughly about it the result has been a "whole bottle of whiskey hangover" strength headache.

So far as additional mechanical retainers applied to a loctite joint my understanding was that any such usually reduced the strength of the joint. Often quite significantly due to stress raisers et al. The absolute strength of a properly made loctite joint is surprisingly high due to the relatively large area over which loads are carried.

Weak point of all adhesive systems is peel strength as very high loads can be applied over near negligible area at the angle between the two components being separated.

Clive.

Edited By Clive Foster on 14/08/2018 13:50:59

Possibly the weakness is even more important than the strenth. If the parts ever have to come apart a socket grubscrew can split and become immoveable, as the components then become too. A plain pin is no problem as after applying some heat the wheels can be pressed off and the pin falls out!

Am NOT a loco man, but realise that the wheels on each side of a steam loco must remain in the same relationship to each other to ensure freedom of movement. (In an extreme case, a two cylinder loco would not be self starting).

With regard to the strength of anaerobic sealants, they can be extremely strong. For many tears cars have been manufactured where the crown wheel is secured to the differential by such "adhesives", happily transmitting upwards of 100 bhp to the wheels.

In my own experience, I bought two ER chucks (ER25 and ER32) for use on the lathe, but had to fabricate backplates. Having smeared very old anaerobic retainer over both faces, the ER taper was clocked and tapped until running true within 0.0005", before tightening the retaining bolts. Some years later, I obtained and machined some Backplate castings to suit the ER Collet Chucks. Having slacked the bolts on the original set ups, it was impossible to remove the ER chuck from the fabricated backplate. (Stopped when I began to fear damaging the chuck with the strength of the blows from a copper/hide mallet) WAY past its "safe to use " date, but the retainer was extremely tough. So does anyone want a couple of 2.25 x 8 tpi threaded cast iron backplates?

Howard

When we made a batch of 16 wheel/axles for our new riding cars, the intent was to press fit the wheels. One of them was a bit slack so it got Loctited. Some time later we realised the back to back dimension on the drawing was wrong. I fairly easily pressed 31 wheels off, but the Loctited one would not budge. Scaffolding bar on the handle of the 1 te jack resulted in the jack cylinder bursting. Yes I know I should have warmed it up, but I was in a hurry. I have no qualms about Loctited joints after that.

Experience suggest a real Sharpie is essential. I think I scored 2 out of 4 for the last lot of 99p ones...

Neil

Splendid result ... Neil now uses the S

MichaelG.