Sharman Wheels in P4

triumph3
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Sharman Wheels in P4

Postby triumph3 » Thu Jul 29, 2021 4:11 pm

I have a couple of locos which I have bought in which have Mike Sharman wheels in OO and EM and which I want to convert to P4. However I am aware that the tyre profile Mike used was a bit variable to say the least! I want to reuse both sets of wheels as one set is the ex LNWR 6’ 8” drivers with the centre boss ( which no one else makes) and a set of H section wheels with the balance weights formed in.
I measured the width of the tyres on the 6’8” drivers is 2.38mm ( Gibson is 2.28mm) and the H section wheels are 2.15 mm (Gibson 2.03).
So I presume that these won’t run on P4 track so my next problem is there any one out there who can re profile the tyres for me? I already have some replacement axles.
2C2C0D0A-BEAC-4645-8BBA-B5D7E78A48E2.jpeg


David
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John Palmer
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Re: Sharman Wheels in P4

Postby John Palmer » Thu Jul 29, 2021 5:07 pm

It's not that Mike's tyre profile was variable; rather, he manufactured two different profiles. One (designated Type A) was intended for use on track built to P4 standards, the other (Type B) for other standards. I think your photograph illustrates wheels representing these two different profiles.

You may find the thread at https://www.scalefour.org/forum/viewtopic.php?t=4587 helpful as it goes into the subject in rather greater depth. As Philip Hall comments, these are robustly manufactured wheels with centres mechanically locked to the tyres, so lending them to reprofiling. I imagine the projected P4 form tool would be well-suited to such a job, but think it must still be under development.

Philip Hall
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Re: Sharman Wheels in P4

Postby Philip Hall » Thu Jul 29, 2021 5:09 pm

The tyres don’t need reprofiling, you can probably get away with just thinning down the back and reducing the thickness of the flange. If you’re not bothered about a slightly deeper flange (schhh…!) you can do this either with a file or by gently rubbing the wheel down on a flat sanding board. I have a very useful one of these made from an old belt sander belt. So long as the running surface of the tyre isn’t touched the wheel will still run fine. Keep rubbing down until you can waggle it about in a flangeway so that it feels the same as a normal P4 wheel. If you do have a rotating device of some sort - a lathe is best but a drill is OK - you can (gently) touch a file on the flange edge to reduce it slightly.

The reason that you can do this is that I recall that in the very early days (before he actually produced two profiles) MIke supplied one profile only (a fine-ish EM) and the P4 ers were instructed to reduce the width of the tyre; the actual profile was pretty close to P4.

I’m a bit mystified by the width of one set of tyres as 2.38mm as MIke used one width of tyres for both P4 and EM. The P4 wheels being slightly over width and the EM slightly less. So the 2.15mm you have ties in with this, and reducing the thickness of the tyre from the back will give you a wheel very close to the P4 upper standard.

I have a final note of caution. I have had some Sharman wheels that were once concentric but no longer are. Maybe they haven’t aged well, being a more bendy kind of plastic than Ultrascale, for example. I have heard of this phenomenon before. However, the upside of this is that they can be put on a mandrel in a lathe and turned true again, because the tyres are locked on to the centres. If this does have to be done, the new Society form tool would be useful here so that you could adjust profile and true at the same time.

I have a set of 44xx wheels that I was contemplating using the new form tool on, but never having done that amount of work on a wheel before it was going to be a bit of learning curve. I say was because I now have a set of Ultrascales so the need has gone away.

Philip

davebradwell
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Re: Sharman Wheels in P4

Postby davebradwell » Thu Jul 29, 2021 7:07 pm

Surprised that you've found a Gibson wheel at 2.28 wide - his P4 wheel tyres should be 2mm wide so you might have measured an EM wheel.

Will add a warning before you start attacking the tyres that the wheel should be gripped around the tyre as just sticking it on a stub axle can result in swept back spokes and the soft plastic offers little resistance. How do I know this?

Presumably you've no outside cylinders to worry about as over-thick wheels will give clearance issues. I've been known to thin wheels to a scale 1.85 to achieve this.

I never liked his crankpin. If he pulled the wheel out of the mould too soon they would lean and I have a bag of eccentric bushes which can't be used.

DaveB

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Re: Sharman Wheels in P4

Postby bécasse » Thu Jul 29, 2021 7:19 pm

Are you sure that those Sharman wheels were once concentric, Phillip? I fitted a two-axle set that were supplied with a Backwoods Miniature kit and was rather disappointed when the completed loco "waddled" along even though it was quite happy to run so slowly that one could watch the worm turn. Investigation showed that none of the wheels were concentric although the lack of concentricity was absolutely consistent in all four wheels - hence the waddle. They must have been manufactured well after Mike sold the range on and I am not quite sure whether the fault resulted from wear on Mike's Heath Robinson set-up or simply because not enough care had been taken with aligning the mould with tyres when injecting the centres. I am inclined to suspect the former though.

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Re: Sharman Wheels in P4

Postby Enigma » Fri Jul 30, 2021 2:47 pm

I am presuming that the wheels have already been mounted and subsequently removed from their axles. My experience is that if remounted, the grip is nowhere near as good as the first mounting. Might be an idea to investigate the various methods of mechanical fixing that have been expounded here and in the press (MRJ?) over the years. I fitted a set of the 'B' profile wheels to a converted Airfix 14xx tank BITD (Mike had run out of P4 profile ones at his hot dog stand) and they worked - after a fashion! Not as good as the 'proper thing' though.

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Re: Sharman Wheels in P4

Postby davebradwell » Fri Jul 30, 2021 3:32 pm

Hmmm! Have abandoned all supplementary wheel fixings - with the soft plastic, any sort of small pin will not prevent wheel turning on axle by the small amount that would put the quartering out of kilter. Try it, that's what convinced me. Only useful way is Loctite but it's a shame if quartering isn't quite right. You might find a bit of silver steel that's a little larger than the Sharman axle - or you might not of course!

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Winander
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Re: Sharman Wheels in P4

Postby Winander » Fri Jul 30, 2021 4:32 pm

In Chris Pendleton's article in MRJ 219 he bushes the wheels with brass inserts but requires a lathe and some skill.

I like the sound of the pin that acts like a keyway i.e. slips between axle and wheel longitudinally along the axle. Requires a slot in the axle that may be difficult to make but could be filed, fit the wheel and then drill along the slot into the wheel - the benefit is the wheel will just pull off if you ever need to do so. To be successful, the wheel still has to be a tight fit on the axle but, in theory, should correct any tendency to slip and be mechanically better than an angled pin.

Is araldite an option? Would be pretty much permanent but if the 24 hour variety is used, plenty of opportunity for adjustment.
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davebradwell
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Re: Sharman Wheels in P4

Postby davebradwell » Fri Jul 30, 2021 4:42 pm

Even with this type of pin you can shift them. It's easy to make the slot - put axle in hole in piece of steel plate and drill into joint. Did it once but never bothered since - you don't actually need a very tight fit between wheel and axle except on heavy locos. If you're using glue it's useful to turn or file a narrow groove in the wheel seat to act as a reservoir for the glue. Chris has found it difficult to remove wheels stuck on like this whereas without this feature it's usually easy.

DaveB

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Re: Sharman Wheels in P4

Postby Enigma » Fri Jul 30, 2021 4:45 pm

Winander wrote: the benefit is the wheel will just pull off if you ever need to do so. To be successful, the wheel still has to be a tight fit on the axle but, in theory, should correct any tendency to slip and be mechanically better than an angled pin.


I tried this following Steve Hall's article in MRJ but discovered that, as you say, the wheel will still pull off and B2B can't be maintained. OK for maintaining quartering and probably fine as a belt and braces first fix but not for subsequent ones.

davebradwell
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Re: Sharman Wheels in P4

Postby davebradwell » Fri Jul 30, 2021 4:55 pm

I'm saying that it isn't guaranteed to maintain quartering with soft plastic wheel.

DaveB

Philip Hall
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Re: Sharman Wheels in P4

Postby Philip Hall » Fri Jul 30, 2021 8:49 pm

I have a set of Sharmans fitted to my oldest engine, a little SECR P Class now over 45 years old. It’s been through three gauges, two motors and two sets of gears and is still quite smooth but it sways a bit and I don’t remember it always doing that. However. I did think the 44xx wheels were ok (bought via eBay) but checks recently showed them to be slightly off.

Maybe it was later batches of wheels that have been like that; maybe I’m just getting fussier with age.

Chris Pendlenton’s idea of the little groove in the axle to retain Loctite works a treat and I now do it on all Ultrascale wheels and any others that have lost their grip on axles. I do occasionally pin through the boss into the axle but in one case I did it twice from different angles. On that engine the boss on the wheels had a hairline crack which I managed to rescue with large brass washers epoxied to the axle and the wheel.

I don’t think Araldite 24 hr is much better at gluing ‘bendy plastic’ than the quick stuff. I do avoid the 5 minute Araldite which is too brittle and prefer 5 minute Devcon. I wouldn’t use it to glue wheels to axles though.

We have got away from the original question though about finding someone to do the reprofiling if necessary? I’d be happy to rub them down a bit, but I’m reluctant to offer to help with the truing or proper reprofiling which I’ve only ever done on one wheel!

Philip

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Captain Kernow
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Re: Sharman Wheels in P4

Postby Captain Kernow » Wed Aug 04, 2021 9:30 am

On the question of retaining plastic centered wheels on axles, I've seen it written that Mike Edge applies a 'knurl' on the axle ends, by rolling the axle on a surface with the edge of a big file.
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grovenor-2685
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Re: Sharman Wheels in P4

Postby grovenor-2685 » Wed Aug 04, 2021 11:32 am

OK if you are confident that there will be no need to adjust the quartering after pressing the wheels on.
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Enigma
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Re: Sharman Wheels in P4

Postby Enigma » Thu Aug 05, 2021 10:59 am

grovenor-2685 wrote:OK if you are confident that there will be no need to adjust the quartering after pressing the wheels on.

Hopefully with a GW wheelpress there shouldn't be any need.

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Re: Sharman Wheels in P4

Postby Philip Hall » Thu Aug 05, 2021 12:09 pm

I sometimes knurl the end of an axle but the little turned groove in the end of the axle works very well. On occasion I have had to use both, and once two pins as well! But those were old wheels that had clearly been on and off a few times.

Philip

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Horsetan
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Re: Sharman Wheels in P4

Postby Horsetan » Mon Aug 16, 2021 7:49 am

Philip Hall wrote:The tyres don’t need reprofiling, you can probably get away with just thinning down the back and reducing the thickness of the flange. If you’re not bothered about a slightly deeper flange (schhh…!) you can do this either with a file or by gently rubbing the wheel down on a flat sanding board. I have a very useful one of these made from an old belt sander belt. So long as the running surface of the tyre isn’t touched the wheel will still run fine. Keep rubbing down until you can waggle it about in a flangeway so that it feels the same as a normal P4 wheel. If you do have a rotating device of some sort - a lathe is best but a drill is OK - you can (gently) touch a file on the flange edge to reduce it slightly.

The reason that you can do this is that I recall that in the very early days (before he actually produced two profiles) MIke supplied one profile only (a fine-ish EM) and the P4 ers were instructed to reduce the width of the tyre; the actual profile was pretty close to P4....


Yes, I have some Britannia wheels, plus a set for the SECR "H", which were produced to this single profile. The width is not far off average P4; it's the flange which needs a tiny reduction in depth and thickness. The latter you could probably do by rubbing along the back of a file.
That would be an ecumenical matter.


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