Author Topic: Slaters Motor/gearboxes : Increasing axle size?  (Read 528 times)

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Offline John Candy

Mike Danby is building some GWR locos for me and the first (nearing completion) is a "Bulldog" 4-4-0.

Mike has encountered a problem and I spoke with him today. The spec. had been for a Slaters 50:1 gearbox unit but these are supplied with roller bearings for 1/4 inch axles.

The wheels (from Mark Wood) were turned and quartered by Walsall but they have fitted 8mm axles.
Mike has tried to open up the gearbox to accept 8mm axles but has (his own words) made a hash of it.

WMI have proposed a 30:1 unit fitted with the "Powermaster" motor..... those are the motors supplied to members of this forum at a "give away" price a couple of years ago.

I am not convinced that it would have enough "oomph" to haul several GRS metal carriages up the gradients on my line..... it is good enough for motor bogies and shunting locos (the Sentinels have the same motor) but I am not so sure about a single motor in an "express" loco.

Has anyone here modified one of the Slater's units to accept larger axles?

The loco is scheduled for delivery early in the New Year, so I need to find a solution as matter of urgency.

Regards,
John.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline IanT

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #1 on: Dec 13 2018 14:38 »
Hi John,

Without knowing what has been done to the gearbox (and what its physical limitations were/are) - one solution might be to 'plug' the MW wheels and then very carefully jig them to centre on the tread and re-drill and ream them to 1/4". Given that the difference in diameter between 1/4" and 8mm is only 1.65mm - it might be necessary to enlarge (bore out) the existing 8mm holes a bit before plugging them, to give sufficient replacement lining metal. Not having seen the castings - I don't know whether this would be doable in practice on your wheels but I'm sure it would be possible on some G3 wheel castings I've seen.

This would be far from ideal of course - but given where you are currently, might offer one potential solution (as I'm pretty sure your MW wheels were quite expensive...)

The best/simplest solution would be to use 8mm axles of course - but that needs a suitable gearbox solution.

Regards,

IanT
Nothing's ever Easy - At least the first time around.

Offline John Candy

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #2 on: Dec 13 2018 19:24 »
Hi Ian,

Thanks for suggestion.

Mike D has since confirmed problem was inaccurate alignment when opening out of the axle holes to 8mm, with result the motor would not sit square in the gearbox. I think they may have been drilled and not reamed.
I have a few of the Slater's motors here to fit into GCR and GNR locos I am building and can see methods one could employ to correct problem (e.g. plating over the existing gearbox casing and re-drilling to take a bush insert).

Mike says he now has a plan for dealing with issue, so I don't need (for moment at least) to work on an alternative.

Regards,
John. 
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline Peaky 556

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #3 on: Dec 13 2018 21:19 »
WMI have proposed a 30:1 unit fitted with the "Powermaster" motor..... those are the motors supplied to members of this forum at a "give away" price a couple of years ago.  I am not convinced that it would have enough "oomph" to haul several GRS metal carriages up the gradients on my line..... it is good enough for motor bogies and shunting locos (the Sentinels have the same motor) but I am not so sure about a single motor in an "express" loco.
John, to answer just one of you questions, I too doubt that the Powermaster motor is suitable on its own to propel an express train.  My experience has been using three of them in the power bogie of “Hillock”, the baby Peak, and in this guise with12v supply they do pull eight Kingscale coaches on the level.
Regards, Tim

Offline John Candy

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #4 on: Dec 13 2018 22:17 »
Thanks Tim.
I can imagine a "Bulldog", fitted with a single "Powermaster" at 30:1, pumping out lots of smoke (and not from the chimney) when attempting to climb with four heavy B-set coaches in tow! The same motor with 50:1 gearing would, I suspect, be suitable for a smaller-wheeled goods loco. and be capable of "slogging it out" with a long, slow, coal train.
Regards,
John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline MikeWilliams

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #5 on: Dec 14 2018 10:53 »
Since 1/4in axles are the almost universal standard size for G3 engines why did they use 8mm?  The engineering solution would be as Ian says - plug and re-bore.  But I'll be very interested to hear how he gets around it.

Sorry that's not very helpful!

Mike

Offline cabbage

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #6 on: Dec 14 2018 12:08 »
I use 8mm axles for my locos. This is mainly because the MOD1 bull gear is normally an 8mm bore.

Regards

Ralph

Offline John Candy

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #7 on: Dec 14 2018 14:20 »
Quote
Since 1/4in axles are the almost universal standard size for G3 engines why did they use 8mm

A good question....to which only WMI know the answer! I had assumed Mike D would have sent the Slater's unit to WMI so they could fit it together with horn blocks before quartering the wheel sets.

The wheel sets (if fitted to the axles and quartered by WMI) will have to be disassembled to fit the gear wheel.

Has anyone else had WMI turn their wheels and received them back with 8mm axles?

John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline Nick

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #8 on: Dec 14 2018 17:55 »
When I turned the wheels for my T3 I made the driving axles 10mm diameter and the carrying axles 8mm diameter, because those were very close to scale dimensions. Only very light locos had axles close to a scale 1/4in. Personally I think it is a great pity that Slaters chose this dimension (though they probably had commercial reasons for doing so), to me their axles look much too spindly.

Nick

Offline Peaky 556

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #9 on: Dec 14 2018 18:22 »
Only very light locos had axles close to a scale 1/4in. Personally I think it is a great pity that Slaters chose this dimension (though they probably had commercial reasons for doing so), to me their axles look much too spindly.
Nick
Well Nick, i do agree with you.  My models have adopted 8mm as the standard.  I’ve just checked the G3S Technical Standards, however, and I see axles depicted that look very much like Slaters, with 4mm journals sticking outside the wheels for the bearings.  So which came first, the Society standard or Slaters axles???  I know that the Society does not specify the diameter of the axle between wheels, but what other sizes would Slaters contemplate in order to comply, if not either 6mm (even more spindly), or quarter inch? 🤔
Rgds, Tim

Offline MikeWilliams

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #10 on: Dec 14 2018 20:03 »
That is interesting Nick.  Wikipedia has a drawing of some Mansell wheels and the axle diameter at the centre is 4 1/2in, which scales just over 5mm whereas 1/4in is a scale 6.35in and your 8mm is way overscale, but I accept that is the Wiki diameter in the centre of the axle and for old vehicles, so BR stock will be more.

Not looked at the diameter of loco axles, but suspect you may be correct there.

The Society standard (or at least commonly used) axle size used to be 3/8in for live steam, but commonly now electric engines have dropped that down to 1/4in because the larger size isn't needed.

Mike 

Offline MikeWilliams

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #11 on: Dec 14 2018 20:44 »
Just looked at a GA for an LNWR Cauliflower 0-6-0 and the leading driving axle is 6 1/2in diameter, which scales 7.3mm, so you are right, 1/4in is only 6.35mm.  Anyone have the diameter of a leading or trailing wheel axle to hand?

Offline IanT

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #12 on: Dec 14 2018 23:19 »
I've always assumed the journal dimensions given by the S01 standard related just to wagon axles and were not really related to 'scale' per-se but more to enabling standardisation amongst (cottage industry) suppliers to make rolling stock supplies inter-changeable...

This was from the second dawn of G3 of course (pre-MW/Slaters) - when Men were Men - and hacked their W irons out of raw metal and turned their wagon wheels from castings!     ;)

IanT
Nothing's ever Easy - At least the first time around.

Offline Nick

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #13 on: Dec 15 2018 09:26 »
I spent some time checking the drawings that I have available to me, covering British steam from the 1840s up to the BR era. Like everything to do with steam locos, axles came in a range of sizes. Generalising massively, early locos had driving axles of about 6in. diameter (so about 1/4in. in our scale). By the end of the 19th century and through to BR days, driving axles were typically 9-10in. diameter. Carrying axles were a couple of inches smaller. The smallest locos kept the smaller axles.

So Slaters axles are not bad for the smaller and earlier locos, but definitely too small for scale for many prototypes. Interestingly, Slaters use 3/16in. diameter for gauge O, and 1/4in. diameter for gauge 1, and people there seem happy with that. Scaling up, gauge 3 should be about 3/8in. I'm not going to speculate why they chose 1/4in. but somehow I doubt that conformance with the G3S standard was the (only) reason.

As Mike points out, the larger size is not necessary for mechanical reasons and if people are happy with the smaller size, that is fine. Maybe I'm just fussy, but to me it makes a difference, not just for the axle itself but because it makes the wheel centre look wrong. But as always, YMMV.

Nick

Offline MikeWilliams

Re: Slaters Motor/gearboxes : Increasing axle size?
« Reply #14 on: Dec 15 2018 10:28 »
Nick, you make a very good point about the look of the wheel centre.  The Slaters design is easy to use and simple for them to make, but to me they spoil the look of a model because you can spot them straight away.  A cast iron wheel forced onto an axle with its end profiled to shape will always look so much better.  But I am not clever enough to do that and suspect most modellers are not either.

Talking of axles, I would love to see wagon axles properly profiled so that the end view of the vehicle is more to scale.  If Slaters axles were smaller one could add a sleeve, but turning each one down to shape is a bit of a bind.

Mike