Loco driving wheels, 21mm dia. 17 spoke reqd.

[philsandy]

I have a Bachmann BR 3MT tank which I converted to EM using the original Bachmann wheels with reduced flange thickness.

However there is not enough clearance between the front crank pins and the valve gear. I've come across this problem before a couple of times, and replaced the front wheels with Alan Gibson wheels,  which gives 0.6mm more clearance, but there are no 21mm dia. 17 spoke wheels in their catalogue. The only source I can find are Romford wheels which use a different axle and crank pin set up. Does anyone know of any other source for these wheels.

[RexAshton]

The Romford wheel won't give you the clearance you need. One thing that does help though is to reverse the front crank pin. Instead of assembling as per the instructions after fitting the screw through the wheel fit a thin washer so that the rods clear the centre boss then fit the top hat bush with the flange to the outside. After final testing lock the bush in place with a wipe of solder and file the remaining screw thread flush. This method saves you the thickness of the nut on both sides. Remember also to eliminate all but clearance side play on the front axle. I don't know of anyone other than possibly Ultrascale who would do the correct wheel. The Romford wheels wouldn't help. Alan has a conversion set for the 3MT which comes with special wheels and the correct 3mm axles. Ref 4800/32 .

[philsandy]

On 20/09/2019 at 08:13, RexAshton said:

The Romford wheel won't give you the clearance you need. One thing that does help though is to reverse the front crank pin. Instead of assembling as per the instructions after fitting the screw through the wheel fit a thin washer so that the rods clear the centre boss then fit the top hat bush with the flange to the outside. After final testing lock the bush in place with a wipe of solder and file the remaining screw thread flush. This method saves you the thickness of the nut on both sides. Remember also to eliminate all but clearance side play on the front axle. I don't know of anyone other than possibly Ultrascale who would do the correct wheel. The Romford wheels wouldn't help. Alan has a conversion set for the 3MT which comes with special wheels and the correct 3mm axles. Ref 4800/32 .

 

Thanks for your reply Rex. Will the Romford not give the additional clearance because of the the crankpin arrangement, are they not as narrow as Gibsons?

This method you describe, what wheel is being used?  I don't quite follow, what is holding the coupling rod in place on the front wheel, please can you elaborate.

 

Ultrascale do not do a 17 spoke wheel, and the Gibson conversion set are 16 spoke.

Edited September 21, 2019 by philsandy

[RexAshton]

On ‎20‎/‎09‎/‎2019 at 08:35, philsandy said:

Thanks for your reply Rex. Will the Romford not give the additional clearance because of the the crankpin arrangement, are they not as narrow as Gibsons?

I don't think the Romford wheel is any thinner that Alan Gibson but you might save some space by using Romford crank pins in the Alan Gibson wheels behind the cross heads and retaining the coupling rods with Markits etched crank pin washers if you can get them. It's easy to fit the Romford crank pins into Alan's plastic centres retaining them with Loctite or similar. I did that on an old North London 0-6-0T. Reversing the Alan Gibson crank pins works as follows. Fit the screw through the wheel in the normal manner. Fit a washer over the screw against the face of the wheel to prevent the coupling rod fouling on the wheel centre. Instead of fitting the top hat bush in the normal manner fit it through the rod with the flange to the outside and assemble both onto the crank pin so that the flange acts as the retainer for the rod. When you're happy with the running (quartering etc) apply a little solder to the bush and remove the projecting thread. I've attached a photo of the process being used on a High Level Kits Pug leading axle. It's not my photo it's courtesy barrowroad on here.

Hope that's a bit clearer. Scalelink do a 21mm 17 spoke wheel but having used some I personally don't think they're as good as the competition - just my opinion

 

[philsandy]

Thanks Rex, got it now.

 

I was mistaken, the 21mm 17 spoke wheels I was looking at are Scale Link and not Romford, I misread it ie. they use a Romford axle. 

I did a search on here, and people have had an issue with them, not concentric etc. some have had no problem with them, but no one else seems to make that size with 17 spokes.

I'll take a chance an order 2, can send them back if there not right.

By the way do you know if the Romford EM axle is 3mm or 1/8" diameter?  as it does not specify on Scale Link website.

Edited September 21, 2019 by philsandy

[RexAshton]

Hi

Romford axle is 1/8". They do a 3mm one but only - I think - for 00. You may get away with a 0.8mm washer on each square section to space the wheels out but it's not something I've ever tried. It's always worth a try but best reliable solution might end up being Alan Gibson's and sacrifice the extra spoke.

As regards the Scalelink wheels I have a set for a DJH Lickey Banker I'm building for a client but I've not got to fitting them yet. Hope they're ok.

Edited September 22, 2019 by RexAshton

[Michael Edge]

You can get 3mm Romford axles for EM, it's a standard item from Markits. In my experience the Scalelink wheels are reasonable but you have to be careful with the fitting on the plastic centre. It's very easy to damage the wheel with the steel axle.

[RexAshton]

1 hour ago, Michael Edge said:

You can get 3mm Romford axles for EM, it's a standard item from Markits. In my experience the Scalelink wheels are reasonable but you have to be careful with the fitting on the plastic centre. It's very easy to damage the wheel with the steel axle.



Thanks for the correction. I'd only looked on the Scalelink site. I read somewhere that smoothing off the edge of the square can help reduce the likelihood of damaging the wheel.

Edited September 22, 2019 by RexAshton

[philsandy]

Ordered and received 2 Scale Link wheels and 3mm EM Romford axle the other day. First thing I did was check the wheels for being concentric, they were spot on.

Never used Romford axles before, and was surprised how short the square section was, can't have been much more than 1mm in length, and could only get them to stay in the wheel hub once the nuts were tightened. The B2B measurement was only 16.25mm, so had to make 2 shim washers, with a square hole, from 0.006" brass shim. This did the job, the B2B was now 16.55 mm and the wheels were bang on square to the axle.