How to replace wheelsets?

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CSL
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How to replace wheelsets?

Post by CSL » Sun Jul 09, 2017 5:43 pm

Hi all,

First post here, although I've been lurking a bit...

Anyway, my ancient Mamod SL3 is suffering from what I gather on this forum is the usual problem of wheels that are loose on the axles. I opted for buying replacement MSS wheelsets from Dream Stream which have now arrived, but I am unsure whether I have worked out the best way actually to do it yet.

My first thoughts were that I should try to disturb as little as possible, since the loco must be pushing 30 years old and has never been disassembled but in my opinion works surprisingly well. However, a little experimentation - which I hope hasn't done any significant damage! - suggests that bending the frames inwards to release the wheelsets without unscrewing the frames from the reverser block won't work for the leading axle.

So exactly how much disassembly is absolutely necessary?

Oh, and can the connecting rod circlips be removed without buying a specific tool?

Apologies for naive questions, but I'm just not in the same model engineering league as many of you here (yet)!

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Re: How to replace wheelsets?

Post by Big Jim » Mon Jul 10, 2017 11:06 pm

If memory serves, I think there is a fair bit of dismantling needed, don't worry it is not overly hard.
Have a look/search in the Mamod section on this forum and I am sure there is a post about it.
Good Luck and feel free to ask anymore questions you need.
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Re: How to replace wheelsets?

Post by CSL » Tue Jul 11, 2017 7:18 am

Thanks for the reply. I did search through the forum but although there was much debate about the type of wheelsets to use (and I'm sure my choice would meet with disapproval from some!), I didn't find anything saying what you did with them...

Anyway, I can work out what to do, but was wondering if there were any less obvious tricks of the trade.

My concern was not the complexity of the job but more about disturbing the set-up of the loco when I am rather surprised that it still works as well as it does (it came out of loft storage last year after the best part of two decades, and apart from the meths burner which I fitted not too long after it was first bought all I've done is swapped the safety valve for the slightly higher pressure version).

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Re: How to replace wheelsets?

Post by Big Jim » Tue Jul 11, 2017 8:00 am

Its always nice to resurrect something that has been dormant for a while.
With an oscillator there is not much to set up as there is no valve gear, if you remove the cylinders/faces make sure they go back one the same side and make sure the replacement wheels are quartered correctly, there is not much else that can go wrong.
Just had a look at a couple of my mamods and one you could remove the wheels with out removing the cylinders and the other you can't as the trunnion bolts seem to be of differing length, one set allows the cylinders to be pulled away far enough to disconnect the piston from the crank pin. The other set doesn't.

What wheels are you planning to use?
If at first you don't succeed, use a bigger hammer!

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Re: How to replace wheelsets?

Post by CSL » Tue Jul 11, 2017 1:20 pm

Yes - bringing this little Mamod down from the loft caused a chain of events resulting in our small garden layout! If I can find the time I might do a write up of the railway on this forum.

I've got no problem disconnecting the pistons from the crank pins, but the issue seems to be that in order to release the bearings I need to get the frames close together.

Removing the frame spacer (there's only one at the rear) enables me to bend the rear ends of the frames together to release the rear axle bearings, but if I try to do the same with the front axle I get the distinct impression that I will permanently bend the frames because the reverser block holds them apart close to the front wheels.

Therefore I deduce that I need to disconnect the frames (with cylinders) from the reverser block, then slide them downwards, before I can remove the wheelsets from the frames. This is what I was thinking might cause issues as there may be some small difference in the set-up when I reassemble it, but I am happy to do it anyway if there's no other way.

Unless anyone knows otherwise?

Second question: how do you get the circlips off?! (I do have spares as I rather assume they won't be reusable.)

I have gone for new front and rear wheelsets from MSS/Dream Steam - and, yes, I have read various comments on this forum about them!

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Re: How to replace wheelsets?

Post by tom_tom_go » Tue Jul 11, 2017 1:23 pm

CSL wrote: Tue Jul 11, 2017 1:20 pm Second question: how do you get the circlips off?! (I do have spares as I rather assume they won't be reusable.)
You can buy tools that do this but I just use a small screw driver although be prepared for it to ping off!

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Re: How to replace wheelsets?

Post by Big Jim » Tue Jul 11, 2017 1:27 pm

Small screwdriver, I use a rag around the work peice to try and catch them. They should be resuseable.

Frames are quite easy to bend but can be bent back. But as you say it might be worth dismantling.
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Re: How to replace wheelsets?

Post by Chris Cairns » Thu Jul 13, 2017 1:59 am

I've had a couple of these e-clips (circlips) come off locos during running. They are generally re-usable and I use a a pair of long nosed pliers to nip them tight after refitting.

What you have described is the usual method of dismantling a loco to allow a wheelset change. You may get lucky with just removing one chassis side frame from the smokebox & regulator/reverser block.

For your reference download these re-written SL1K instructions which include cleaned up exploded diagrams at the back - http://www.hglw.co.uk/Mamod%20SL1K%20Lo ... ctions.pdf

Chris Cairns

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Re: How to replace wheelsets?

Post by CSL » Thu Jul 13, 2017 6:05 pm

Chris,

Thanks for that (I assume you mean that the dismantling I've described is the usual method).

I built an SL1 kit back in the '90s with high hopes for it accompanying the SL3 in my parents' garden but it never worked properly - wouldn't steam and was front heavy. While I had cut down the cab, it was only copying what I'd seen in Mamodification articles (or so it seemed, anyway). It went for scrap metal years ago, which is a bit of a pity as it would look quite nice parked outside slowly rotting on a scrap line now I've got a railway in the garden, or even taken to bits and rebuilt somehow!

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Re: How to replace wheelsets?

Post by CSL » Sun Jul 16, 2017 8:35 pm

So, I guess this has now turned into something of a cautionary tale...

On further investigation, I found that the reason I hadn't been able to squeeze the frames close enough together to release the front wheelset was that one of them was catching on a bit of metal that hadn't been cut off when I fitted the meths burner years ago.

So I went for the frame-bending method, without disturbing the cylinder/frame/reverser block assembly. New wheelsets fitted, loco run by hand on a bit of track - all good.

However, out in the garden it doesn't work. It runs fine on rollers, and on straight sections, but it now usually stalls on curves, and has an increased tendency to derail. Pushing the loco reveals a distinct resistance to curving.

I take it that this is because the frames are bent inwards between the wheels, causing some kind of irregularity in the axles' alignment which is affected by curves? And I suppose the solution is to try to bend the frames back straight? Does anyone have a view on effecting this in situ?

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Re: How to replace wheelsets?

Post by Gralyn » Mon Jul 17, 2017 10:21 am

Don't forget to check the Back to Back measurement of the wheels first.
Tightness on curves is a sure sign that it may be too wide.
Regards Graham.

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Re: How to replace wheelsets?

Post by CSL » Tue Jul 18, 2017 12:58 pm

Graham - excellent suggestion; why didn't I think of that? (Answer: because I was preoccupied with thinking that it was my intervention that was going to cause problems.)

At first sight that *might* explain it. The new MSS wheelsets seem to have thicker flanges and possibly a larger "front-to-front" dimension (if you see what I mean) than the original Mamod ones.

Haven't had time yet to dismantle the loco again and refit the old wheelsets to check. Since I use Peco track it won't be down to any vagaries of track gauge.

However, it seems quite possible that - if you are correct - that the old, faulty Mamod wheels will function better than the brand new ones. In which (still hypothetical) case, I would have demonstrated that the frame-bending was not the problem and also that I'd purchased supposedly 32mm gauge wheelsets that do not work on 32mm track.

Now to find the time...

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Re: How to replace wheelsets?

Post by CSL » Tue Jul 18, 2017 10:05 pm

Well, I found the time and the results were... interesting.

In short, defective near-30-year-old Mamod wheelsets with loose wheels resulting in cranks settling at about 180 degrees work, while brand new MSS replacements don't, because the flanges are too tight on the rails.

Presumably performance would be better still if I could find accurately-gauged wheelsets that were properly quartered...

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Re: How to replace wheelsets?

Post by Chris Cairns » Thu Jul 20, 2017 12:26 pm

Sounds like MSS quality control has not changed then.

The problems I've heard of with MSS wheels is either they are wide to gauge (back to back greater than 28.5mm) or their flanges are too thick so that even with the correct back to back they still end up wide to gauge (greater than 32mm across the flanges).

One of our 16mm Group members has an MSS side tank loco, which was having problems running round a member's layout. Whilst others were shouting 'check your back to back', I added 'check the flange depth'. Closer inspection revealed that one axle had thicker flanges compared to the other axle.

If your MSS wheels are indeed wide to gauge I'd get back onto Dream Steam for a replacement set.

Chris Cairns.

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Re: How to replace wheelsets?

Post by CSL » Fri Jul 21, 2017 3:19 pm

Chris - yup, that's what seems to be the problem and what I'm doing about it. Got to say that it's at least noteworthy that, apart from one location on a curve where it always seems to stop (I'm thinking it'll make a good place for an outer home signal!), my ancient Mamod can pull two vehicles around the circuit despite having loose wheels on both axles. Two things help it: firstly it has a meths burner and uprated safety valve, and secondly I didn't make such a bad fist of laying an almost dead level trackbed, even if I say it myself.

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