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Wheels and axles – Bachmann’s early B1s

Continuing my BR(NE) saga I have resurrected a couple of elderly Bachmann B1s that have been quietly slumbering in their boxes.

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Bachmann B1s – Widlebeeste and Hartebeeste

There is an issue with these particular early models and mine were not immune! For whatever reason the black plastic wheel centres expand with time and catch on the coupling rods preventing the wheels from freely turning. The affliction does not affect the centre driving wheel and rather puzzlingly it is the rear pair of driving wheels that is most at risk. Fellow modellers report that Bachmann BR standard 4MT models of a similar vintage are also affected.
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Bulging rear wheel centre

Another view of the problem.
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Bulging Plastic

The wheel centre appears to be a type of nylon and can be poked out from behind the wheel using a cocktail stick or very small screw driver. I think it is a push fit into the wheel casting but I cannot be sure.

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Bachmann B1 rear wheel set

I guess it is possible to remove the wheel centre whilst leaving the wheel set on the engine. However I think it makes life a whole lot simpler to unbolt the connecting rods and lift out the complete wheel set.

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Bachmann B1 plastic wheel centre

The outside edge of the plastic inlay can then be carefully rubbed with 400 grade wet and dry (emery) paper, at the same time gently massaging the spokes back into a flat shape (a bit of warmth seems to help). The ‘nylon’ is tough and it is a slow process to reduce the diameter such that the plastic centre is a snug fit into the cast metal wheel. I have repaired two models and have not used any adhesives to hold the resized wheel centres back in place.

There is a short video here comparing before and after running:

http://youtu.be/BaXy6XUSMoA

Comments from fellow modellers suggest that the wheel centres will continue to expand with time. I have no knowledge of the type of plastic or the chemical mechanism that is causing the expansion, but given that the models are now at least 25 years old I am not expecting a huge increase in expansion over the next couple, or even the next five or more years. We shall have to wait and see!

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Bachmann A4 Split Axles

The other issue with these old ‘split chassis’ models is the fragile state of the nylon axles. Bachmann refer to the axles as ‘isolators’. They are a force fit onto the ‘squared’ wheel stubs and over time they will crack and break even without any use.

http://youtu.be/YWP0htE-4qM

EBay has lots of listings where old Bachmann models are offered ‘for sale’ – tested working, where subsequently it is obvious that the nylon ‘isolators’ have failed. Even in their broken state the bits of nylon will offer sufficient grip to propel the mechanism backwards and forwards in a straight line. It is only when the wheels are subjected to side forces such as when negotiating a long curve that the wheels will be forced apart – revealing the true nature of the problem.

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Insulators and Circlips courtesy of Bachmann

Salvation is at hand and sets of isolators are available to purchase direct from Bachmann Technical Department in Leicester.

 

Thank you for your recent e-mail, we can supply a set of axle isolators (2 plain & 1 geared) for £3.00 and 4 circlips for £1.00 plus £2.00 p&p. The isolators may have different tolerances due to the wear on the tooling. If they are a little slack our technicians use a small amount of glue to keep them in place. If you wish to order please contact us on 01455 245 575 to pay via card, alternatively please send a cheque/postal made payable to Bachmann Europe with your order details, name and address. Please quote SD##### on all correspondence, offices are open 8.30am until 5pm.


Why buy ‘circlips’ you ask? In order to replace the ‘isolators’ I find it best to remove the whole wheel set from the model. On Bachmann split chassis locomotives the valve gear and connecting rods are held by a circlip which slots into a groove on the end of the middle axle. Prising the circlip out of the groove with a pin or fine screw driver allows the valve gear to be disconnected, the connecting rods lifted off and the coupled wheel set lifted out from the chassis. The only problem being that the circlips are very ‘springy’ and if they haven’t shot off the model whilst being first removed, they are likely to disappear out of sight whilst being replaced. Life is too short to spend time searching for missing circlips – you just need a supply of replacements!

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Bachmann B1 – spot the circlip

My experience over a number of years is that the ‘standard’ isolators fit the majority of Bachmann’s split chassis models. One exception is the old Bachmann J72, where the centre gear wheel is offset.

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Bachmann J72 Split axles – from an advertisement on eBay

I have not tried to source isolators from Bachmann for the J72 but I have seen 3D printed copies offered ‘for sale’ on eBay. Bachmann isolators are ‘nylon’. I am guessing that 3D printed isolators will not be nylon and may have different mechanical properties.

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Bachmann B1 – disconnected valve gear

Handling elderly models can be quite stressful! Bits just break and ping off – almost without touching! On one of my B1s the plastic motion brackets supporting the valve gear just fell off the mazak chassis casting. Luckily this is an easy repair - use a drop of Wilkinson’s super glue and push back into place.

http://youtu.be/MKVoG1SsIOI

The proof of the pudding is in the eating, and I now have two nice smooth running models.

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Two Elderly Sisters

For the moment I have two good runners which can be bought for a fraction of the price of the latest offerings from Hornby, Bachmann and Dapol – food for thought?

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A proper wheel centre - (19thC?) un distorted cast iron, from out of our garden
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All the nylons expand as they absorb water, but the extent depends on which particular nylon is used.

 

There is a lot of data out there on the net, with some suggestions that it can be reversed by heating the components. Might be an idea if the rtr manufacturers looked at other plastics, but that might push up costs. 

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Thanks Dave John

All the nylons expand as they absorb water, ... 

I had guessed something like that.  If it isn't oxidation (usually rusting) it is degredation of the rubber and plastic parts that are a cause of concern on my old MG.

 

Ray

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I never knew this, very interesting. Thinking back I may have given up on one or two locos in my early modelling days without realizing this was the problem.

 

Thanks also for yet another informative and well presented post, Ray. The amount of information stored in your blog is impressive. You ought to have a regular entry in one of the mags! Suggested title: "Ray's RTR fixes" :-)

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Thanks Mikkel

 

Do you have any contacts?

 

......... You ought to have a regular entry in one of the mags! ...

 

In a past life, apparently, I was working at the 'cutting edge of technology' and writing and publishing learned papers.  Old habits die hard but it is good to keep the little grey cells working.

 

Thanks

 

Ray

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No contacts, I'm afraid - but BRM seems obvious.

 

I was just looking at the header photo again, there's something about that photo which really captures my imagination. Who says black locos can't be stylish!

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Thanks Mikkel

 

Of course it rather nice not to have to work to deadlines

 

No contacts, I'm afraid - but BRM seems obvious

.

... Who says black locos can't be stylish!

Well - I thought that the BR lined black livery owe its origins to the LNWR?  Being one of the larger pre grouping railways I am guessing that the company would have chosen a suitably stylish livery to compete say with your GWR?

 

Ray

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I wish I had had this idea earlier. I was forced to replace the wheels on my own old B1 due to the small problem. She is in need or another modernised now however. 

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Thanks ST, you might go down the route of buying a replacement model for spares?

I wish I had had this idea earlier. I was forced to replace the wheels on my own old B1 due to the small problem. She is in need or another modernised now however. 

I guess as other's have said - if the nylon continues to take in moisture and expand there might come a time when there is no rim of plastic left to file away.  Might have to experiment drying things out in the Aga!

 

Thanks Ray

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I think overall, if you want to stop the problem the new chassis is the way to go unless you able to construct a kit chassis. Still though, tinkering is what a lot of us are about.

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Yes - I like tinkering.

I think overall, if you want to stop the problem the new chassis is the way to go unless you able to construct a kit chassis. Still though, tinkering is what a lot of us are about.

You have to balance sourcing a preloved chassis compared to making a new chassis and buying new wheels and motor.  It imight not be just a money matter there can be time constraints.  Tinkering can be a very attractive option.

 

Thanks Ray

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Again your Blog has proved invaluable! I recently picked up a "Witherslack Hall" on ebay, perfect condition, except that the isolators had failed completely. My order to Bachmann was delivered in 48 hours and the axles are now under repair.

 

I found the isolators had some flash and were overtight on two axles, and carefully cleaned them out with a file and sharp knife. On the third undriven axle they are too slack - I have tried all the isolators from my three pack order, which suggests Bachmann's axle stubs do have variations in size. I'm hoping a bit of glue will do the trick, as recommended.

 

Many thanks,

 

John.

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Hello John

 

Good to hear you have had some success and that my Post has had some use.

 

I found the isolators had some flash and were overtight on two axles, and carefully cleaned them out with a file and sharp knife. On the third undriven axle they are too slack - I have tried all the isolators from my three pack order, which suggests Bachmann's axle stubs do have variations in size. I'm hoping a bit of glue will do the trick, as recommended.

 

Thank you for the tip about the excess 'flash' on the outside.  I had wondered why one particular wheel set was stiff (and is temporarily resting).  All my latest isolators have been too slack and I have used a drop of Wilkinson's super glue on the end of the wheel spigot and also a smear on the outside of the nylon spigot.  You just need to be quick at pushing the wheels up to the desired spacing.  So far so good.

 

Cheers

 

Ray

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