Curing the Bachmann Split chassis loco waddle

[shildonboy]

I had two 4MT 4-6-0s and a B1 which all suffered from poor running and a peculiar side to side waddle when running. I checked the axles and all were good: no spilt axles, the wheels were not loose on the axles, the quartering was good. 

I found nothing on any of the forums and then I noticed the plastic centres of the driving wheels and the spokes were bulging out and catching the connecting rods. You can see this if you invert the loco and turn the wheels slowly.

I unscrewed the connecting rods on on pair of wheels and removed them from the loco and noticed the plastic centre was bulging outwards. I found I can pull the plastic centre out of the wheel. There is a small outer lip on the outside edge of the wheel which was full of crud. I cleaned the crud out and tried the plastic centre again, it was a better fit but still did not fit flush. 

I realised that that oil from the connecting rods made the plastic swell slightly causing it to buckle. It is a soft soapy plastic. I sanded the back of the plastic with fine abbraisive (1500 grade) and scrapped the outside diameter with a scalpel blade to remduce the diameter until it would fit into the wheel and could be pushed down to sit flat.

A quick clean of both parts with 99% alcohol, aliow to dry and then I smeared thick super glue across the back of the insert making sure to cover all the backs of the spokes etc. I then refitted the insert in the wheel and used 3 small spring clamps to squeeze the insert down onto the wheel and left to cure.

After a couple of hours I removed the clamps and checked that when I pushed the insert with my finger there was no movement. A check with a steel rule confirmed the insert was now flat.

Reassembled the wheels and con rods and now the locos run without the Bachmann waddle.

       

[Silver Sidelines]

You might be interested in this recent thread:

 

http://www.rmweb.co.uk/community/index.php?/topic/129751-Bachmann-wheel-centre-woes/

 

and a Post on my Blog

 

http://www.rmweb.co.uk/community/index.php?/blog/880/entry-20345-wheels-and-axles-%E2%80%93-Bachmann%E2%80%99s-early-b1s/

 

Reading around the subject, the nylon is moisture sensitive and will swell with time.

 

Regards

 

Ray

[shildonboy]

Bachmann have replacement wheels for the China made locos for 17 GBP a set.  A bit pricey.

 

Your blog shows exactly what I found with my locos.  I am hoping that by reducing the insert diameter and gluing them in place to avoid a repeat failure.  At some point in the future when the wheels finally give out I may resort to fitting Markits wheels depending on the other alternatives available at that time.

[34theletterbetweenB&D]

Attempts to fit alternative steel axled wheelsets of decent mechanical integrity have been made. Graeme King was one contributor here who described his method - and abandoning it - but that will be a good while past now, possibly on the RMweb archive. Candidly, once the plating wears through on the tyres, axle stubs and the half chassis recesses they run in, the mechanism is definitely life expired. Strip it for re-usable parts, dump the rest.

 

The replacement mechanism options are very simple: build - from an etched kit or scratch - a replacement frame to take kit wheels etc. which can yield a very superior result; or buy the current incarnation of the model for its mechanism, sell on the body and any other surplus pieces as spares to reduce the net cost. (The lack of spare bodies for Chinese RTR productions works in our favour, body shells in good order usually sell readily.)

[Dunsignalling]

Beware trying to fit old bodies onto new chassis, as one sometimes wants when the older model has been super-detailed etc. They aren't always a straight swap.

 

Certainly Mainline 4MT shells don't fit late Bachmann chassis without filing the top corners of the chassis block. The same may apply to different generations of Bachmann locos.

 

Nothing like the hassle of fitting a Hornby County mechanism into a Dapol body, but worth bearing in mind for those with more than two thumbs.

 

John

Edited February 22, 2018 by Dunsignalling