Ivatt 2-6-2t 2MT front pony axle

[trainthusiast101]

Hello, I'm looking for some help on a second hand logo I got from Ebay. This is the first time I've done maintenance on my own loco so please be patient and understanding when replying.

It's a lovely runner, but the wheels on the front pony freeze up and do nothing but scratch the track. On looking at it, I noticed a split in the axle 'isolator' as a representative from Bachmann referred to it as. I think the split was catching on the underneath of the chassis and stopping the axle from rotating.

split_axle

axle_split.png (203.85 KiB) Viewed 2709 times

When I took it to my local model shop for a service, I showed them the damaged axle isolator and asked if they could replace it. They've serviced the motor, but did nothing about the isolator.

I've resorted to calling Bachmann for a replacement isolator, which is practically a sturdy tiny plastic tube. I've managed to take the wheels off, but I'm having trouble getting the axles to squeeze into the plastic tube. The hole is quite small and I'm worried I'll not just damage my replacement isolator, but the wheels too.

wheels_new_axle

Any advice on what I can do?

Many thanks

[Bigmet]

How do you feel about very slightly opening out the bore of the tube? I would use a micrometer to measure the stub axle diameters (two measurements at right angles on each) and then select a suitable drill of matching diameter. (A taper broach would be even better, but if you had one you would have used it by now...) You want a snug sliding fit - no real force required to put the stub axles into the isolator - which can then be secured with a tiny dot of cyano. Watch the gauging, a collar or two of packing may be needed so the wheelsets cannot be pushed home undergauge.

[mahoganydog]

A taper broach

Don't you mean a taper reamer? A broach is for making a keyway slot in a pulley for example.....

Jim

[Bigmet]

Yup, brain fart there....

[Roger (RJ)]

Keyway broaches aren't the only type of broach. https://cpc.farnell.com/modelcraft/pbr2 ... _lEALw_wcB

[D605Eagle]

I think this is why the isolator splits in the first place as its super tight fit. You might want to use a vice to push one wheel into it and the again once you have put the axle assembly into the pony truck. Knowing how old Bachmann tooling has worn, the hole has probably got even smaller now so be careful!

[Bufferstop]

It's a poor design, and may well fail again. I'd look for a pair of the correct pattern wheels on a 2mm steel axle. You would need to find some bushes 2mm internal, same external diameter as the half axles.
I'm assuming Bachmann haven't released a re-chassied version, in which case I'd replace the old chassis parts with as much of the new chassis as you can afford.

[D605Eagle]

You can't use a steel axle on these as the two halves are electrically opposed. It uses these wheels for pickup. Yes there is a new chassis version of these, but they are eye wateringly expensive for some reason.

[Bigmet]

I think this is why the isolator splits in the first place as its super tight fit...

Many of the split chassis models carrying wheels are like this, and have been since the models were launched. Once I was aware of the resulting splitting I took every example I then had apart, reamed them all out for snug sliding fit and reassembled with a tiny dot of adhesive. Result, no problems from this aspect of the construction, and most are still in service taken from clapped out split chassis and transferred to other models providing low friction pick ups on carrying and tender wheels.

[trainthusiast101]

Yeah, I've been thinking if I had a small enough drill I could make the holes slightly wider.

How do you feel about very slightly opening out the bore of the tube? I would use a micrometer to measure the stub axle diameters (two measurements at right angles on each) and then select a suitable drill of matching diameter. (A taper broach would be even better, but if you had one you would have used it by now...) You want a snug sliding fit - no real force required to put the stub axles into the isolator - which can then be secured with a tiny dot of cyano. Watch the gauging, a collar or two of packing may be needed so the wheelsets cannot be pushed home undergauge.

[trainthusiast101]

Duly noted. Probably not going to be able to do anything until I get hold of the right tools for the job.

I think this is why the isolator splits in the first place as its super tight fit. You might want to use a vice to push one wheel into it and the again once you have put the axle assembly into the pony truck. Knowing how old Bachmann tooling has worn, the hole has probably got even smaller now so be careful!

[Mike Parkes]

I'm assuming Bachmann haven't released a re-chassied version, in which case I'd replace the old chassis parts with as much of the new chassis as you can afford.

They have
31-440 41243 BR Early emblem
31-441DC 41291 BR late crest fitted with a DCC decoder.

Not sure if any parts are interchangeable and I have tried to fit an old body onto the new chassis without success, seems to be a slight difference in the body fixing point dimensions

[Mike Parkes]

Just an idea on fixing the axle - try dipping the plastic part in a cup of boiling water - its may become slightly pliable allowing the wheels to be pushed on.

[Bigmet]

Bachmann have subtly altered the body fixing points on the few re-chassied (ex-split chassis) models I have so far looked at, other than the V1/V3.

But that said the old B1 and V2 bodies were very easy to alter to make fit on the new chassis: a little plastic carved away here, a new plastic boss to take the self tapper cemented on there. A quick look at the underside of the two bodies is recommended to assess. Haven't seen the new mickey mouse tank as my mucker who does midland is currently on a long term assignment in Canada, so cannot provide direct advice from knowledge.

[Mike Parkes]

Think it was the plastic peg that a fixing screw fastens into is thinner on the new model than the old with the result the old body would not fit down on to the chassis. Suppose with care the peg on the old body might be thinned down but I took the simple way out of deciding to keep the split chassis one rather then ebaying it (at the moment) - I had DCC fitted it, not the easiest of jobs as you have to dismantle the valve gear to get the chassis apart and there are at least two different fixing arrangements for the pin on the centre axle, early ones have it retained by a circlip.