Jump to content
  • entries
  • comments
  • views

P4 wheels for a Dapol Class 22



Earlier today I posted a short note on the Dapol Class 22 thread about my first attempt at converting the Dapol wheels to P4 using tyres from Gibson coach wheels. With the aid of a fan heater, I'd survived the cold garage for long enough to produce my first wheel.






Since then, I've made three more so it is probably worth explaining how I did it in greater detail. The next two photos show the various stages of the process from the original Dapol wheel at the left to the new P4 wheel at the right. The brass objects in the first photo are the two halves of a simple tyre press that I knocked up to help ensure the tyres seated correctly.


The wheels appear to be made of aluminium or aluminium alloy and are tightly pressed onto the axles. The latter are non-magnetic, so I assume they are made of stainless steel. The fit is almost, but not quite, tight enough to machine the wheels with the axle held in the chuck. I managed to do this first one this way but there was occasional slipping so, for the remaining wheels, I held the axle in a collet that was adapted to also hold the wheel. This was done by drilling a hole in the front of the brass collet and inserting a short piece of 1mm diameter silver steel rod. This then passed through a pair of the spokes to provide a dog drive to the wheel.




The first stage is to turn the wheel down so that it is a tight fit to the inner diameter of the Gibson tyre. This appears to be a nominal 13mm, though my measurements did vary, perhaps affected by temperature differences indoors and in the garage. In practice, I aimed for about 12.98mm for this cut and two of the four wheels needed a fraction more to get a good press fit.


The Gibson tyre has a small flange at the outside end of this surface to ensure the tyre sits squarely on the centre. The next step (third wheel from left) was to cut a 0.4x0.4mm step at the outer end of the previous cut to match the flange on the tyre.


Next, the wheel and tyre were cleaned and the tyre pressed on to the centre until the slot and flange were firmly seated. The brass press was intended to be used between the chuck and tailstock on the lathe but, in practice, it was just as easy to do this in the vice.




The photo above shows how a thin piece of metal extends beyond the new tyre at the back of the wheel. This is all that remains of the original inset part of the Dapol wheel in the area beneath the flange. The final machining operation is simply to face this off to give a clean back to the wheel in line with the flange of the new tyre.


Finally, the wheels were re-fitted to the bogie using the original Dapol muffs, brass bushes and plastic washers. additional brass spacer washers were added to take up sideplay.






With luck, I'll get the other four wheels done tomorrow. Before everything goes back together, the bogie sideframes will need trimming to clear the new wheels and, perhaps, to adjust their height. Others have commented on how the axle boxes are not in line with the axles.


Coincidentally, Geoff (sparky) has drawn my attention to a new development on the Ultrascale web site. Putting two and two together, it looks like they may be considering offering to do something similar with customers wheels. Either that or they've managed to get a supply of the standard Dapol wheels.




Update, 14:40, 20th Jan 2012:


All eight wheels done and after a quick test on the rollers D6331 assists with track laying at Camerton (though strangely devoid of bogie frames):



  • Like 19


Recommended Comments

  • RMweb Premium

Very interesting. Here's hoping Ultrascale decide to offer some kind of wheel turning service as suggested.

Link to comment

Nick, ok, so I don't own a lathe, but the process is well described, and I can see how it's done... which is hopefully this entry's intent. A good soultion to a trying problem; very well written and illustrated. Thanks. Hope she runs well!


Link to comment

Hi Jon, yes that was the intention as well as confirming that it was actually possible and, maybe, encouraging others to have a go or even pursuade a friend with a lathe to do it for them. Hopefully, as ullypug says, Ultrascale may be able to make this sort of solution more generally available.


With luck, I'll be able to report back later about how well it runs...



Link to comment

Many thanks for showing us your efforts Nick, I may just be able to undertake this one myself! Just need to find a bit of time and some courage!



Link to comment

Give it a go, Paul. The wheels are quite soft and there's the issue of making sure the wheel doesn't rotate on the axle. I found it best to take no more than about 0.05mm off at each pass.




ps. we also now know that Dapol Dave has a small stock of spare wheels which I think may give some folk the confidence to try this.

Link to comment
  • RMweb Gold

Many thanks for showing us your efforts Nick, I may just be able to undertake this one myself! Just need to find a bit of time and some courage!Paul

On the other hand, Paul, if you're feeling a bit less brave, like me, you could try the tender wheel wheeze - should work fine based on what I've seen so far about the way the Dapol wheels come apart...

Link to comment

It's probably worth saying that I'm a long way from being an expert machinist, and I did agonise over whether I could actually do this for about a month. In the end, I found it very straightforward. It is, after all, just three straight cuts. I decided in the end that I could always try the spoked tender or coach wheel as a fallback if I made a mess of the Dapol wheels, but that would also be new ground for me as I've never tried fitting shorting strips on a plastic wheel before.



Link to comment

Dragging this thread back to life eight years later.


Can you remember how you got the Gibson tyres off the plastic centres? 

I’ve decided I need a Dapol 29 on Clackmannan Goods and have ordered a set of 22 wheelsets to have a go at using your method. Hopefully they are the same as the 29 wheelsets. I know Gibson wheels have had a reputation for having loose tyres in the past but my spare ones seem to be fairly well attached.

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...