Author Topic: Alternative methods of fixing coupled wheels to axles.  (Read 336 times)

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Offline John Candy


I had always thought the "normal" method of fixing cast iron wheels to axles was an interference fit, aided by Loctite, but other methods have come my way over the past few years.

Telescopic axle secured with a taper pin is one and another where the wheels are screwed onto a threaded axle.... this was recently used with the "Bulldog" wheels which were turned by Walsall MI and those had me puzzled for a while.... after heating and tapping with a hammer, thinking they were held by Loctite, I tried twisting them, only to find they were threaded!

The most unusual which I have come across are ones which are square-shouldered and held by a screw....identical to the method used by Slaters for their wheels (and similar to Romfords 4mm  in days of yore). Is this a common method in G3?

The set of this latter type came with a chassis (I understood to have been made by Roger Marsh) but they are a loose fit on the axles..... the "play" is rotational (i.e. in relation to the quartering not sliding off the axle). I have dismantled these sets for re-use but am wondering how to secure them correctly and firmly quartered......perhaps some kind of packing?
Perhaps turning them again, to be quartered and fitted to "normal" plain axles would be a better option (they are fitted to 8mm axles and I believe the wheel are probably from the N2.5GA.

Regards,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline IanT

Re: Alternative methods of fixing coupled wheels to axles.
« Reply #1 on: Jun 25 2019 22:19 »
There are quite a few quartering methods John and you've already mentioned a few.

One that I've seen in G1 (but not G3 as far as I'm aware) is to drill each end of the axle with holes at 90 degrees to each other. This can be done with any indexing device or simply in something like a [square] 5C collet block. A slot is then milled in the back of the wheel casting, through the centre of the wheel and to be a tight fit for the pins that fit the drilled holes. The pins then quarter the wheels when assembled.

Not tried it myself but it sounds easier than squaring the axles and then making square holes in the wheels to match....or of course you can make a quartering jig and use that.

Regards,

IanT
Nothing's ever Easy - At least the first time around.

Offline John Candy

Re: Alternative methods of fixing coupled wheels to axles.
« Reply #2 on: Jun 25 2019 23:21 »
Ian,

The wheels are puzzling me because EVERY ONE of the 6 wheels has approx. 1 degree of rotational play, which suggests it is deliberate and not accidental (if Roger Marsh made them, I cannot believe it would be sloppy workmanship).

I wonder whether it was to allow for some "play" to prevent the rods locking up (e.g. as the springing moves).
Could it be something that is "acceptable practice" in model engineering circles?

It is unlikely the result of wear, since the model from which the wheels have been taken is only a few years old and cast iron doesn't wear that easily.

I don't think it would be easy to drill into and pin the axles as matters stand (see photo), I certainly wouldn't feel confident to do it.
It may be simpler to scrap the wheels and buy a set from Slaters!

Regards,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline IanT

Re: Alternative methods of fixing coupled wheels to axles.
« Reply #3 on: Jun 25 2019 23:53 »
I would be pretty sure Roger knew exactly what he was doing too John.

This method is much easier if you are set-up to do it quickly, as I'm sure Roger would be - given he was in the model manufacturing business. I'd guess it probably works well in terms of the trade-off between production time vs assembly time. I assume he drills a suitable hole in the casting and then broaches it square. The axles are then a simple repeat milling job in an indexing fixture.

The 'rotation' is probably just the tolerance/fit Roger decided was acceptable but possibly it does also help to prevent binding (more built in tolerance). Roger wrote a very interesting article in the G1MRA Journal some years ago - in the early days of the ARMIG discussion. Rogers suggestions for making ARMIG more "doable" (for the Trade) were very interesting - not only showing his decades of experience but also a fairly lateral approach to making models commercially/efficiently. As he commented - time is money when you are trying to make a living at it (or words to that effect).

So, if it's not broken, then why try to fix it? I'd just re-assemble them.

Regards,

IanT   
Nothing's ever Easy - At least the first time around.

Offline John Candy

Re: Alternative methods of fixing coupled wheels to axles.
« Reply #4 on: Jun 26 2019 06:45 »
Ian,

Yes, I suspect it may well be a case of "commercial expediency".
A few months ago, I spent a whole day easing the rods on a LNWR Coal Tank to get it to run without binding .... having "slack" in the quartering would have been a solution.

Regards,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.