Hornby 51xx to P4

[doggeface]

Martin, The Gibson part number is 4800. They came in a pack of 6 or 10. I am told (by Gibsons ) that they now appear in the latest pdf catalogue.
I am not sure that they are 2.5mm OD as I have been using them on my Hornby locos -- they need a little careful reamerand hand drill treatment in oder to fit them. The Bachmann which I did some months back (57xx) fitted rather tightly.
I do have a couple of 43xx moguls but something to do with the axle diametre made me think that a new chassis would have to be made up. I think it was the fact that only split chassis with moulded driving sprocket/pinion existed and so made life difficult! I did try this in my 00 decades without managing to get a concentric unit. I would be delighted if there is a way to P4 these without too much effort ( I do have rather a lot of track work to get on with before my eyes or other bits give up!

Peter

Stop press: The 4800 reducing bushes are the last item listed in the 4mm section of the catalogue . It does not tell you how many are in a pack.

Some have just arrived and there are 10 in a pack.

[Philip Hall]

Re Gibson crankpin bushes: following my post about the (sometimes) differing sizes of coupling rod holes, here's a new one. I am just converting a Bachmann BR Class 3MT 2-6-2T, and the front and rear holes in the coupling rods are 2.5mm, but the centre ones are 2.7mm. And yes, the Bachmann crankpins are also at different sizes - 2.01mm for the outer ones and 2.45 for the centre. Nor do the rods match the axle centres...

Philip

[doggeface]

It is now about a week since I set out to P4 a second GW 14xx after the successful conversion of the first. Getting the bits together turned up a pair of smart looking conn rods. Everything went very smoothly, including replacing the hard wired DCC chip and on the track it went. The alignments which had been checked and rechecked resulted in a major collapse of quartering and seizure! It also wrecked several crank pins. Today I finally found some time to get back to it. This time the conn rods were the originals bushed to suit. Result = excellent. The fault, of course, was in the shiney new (comet)conn rods; One of them was the correct 29.3 mm centre distance but the other was 30mm. It must have been from a different fret and I had been careless . Normally, I would have popped in a spare motor and given it a power run with it's legs in the air and a hand roll before fitting the DCC motor -- it takes me by surprise rather when I prove myself to be still human and thus prone to the odd cock-up! (gives my wife a good laugh - if I tell her!)
Anyway, that puts the 4th loco into commission. By the time I have done the 2nd 51xx (its valve gear will take the reducing bushes without further work) and a 27xx and second Bachmann 57xx (which can share a body with a Jinty as we are modelling the F-o-D [Severn & Wye] GW : MR Joint period). This should be enough to run some trains whilst extending the track. As I am obliged to use the base boards as the work bench for the track construction it is already starting to feel restricted. As I have P4'd a Hornby Turntable to enable entry & exit from my loco dept (keeping curves to an absolute minimum of 0.8M rad) this will take a lot of track.
Telling the tale of poor engineering technique is intended as a "don't do it like this" advice!

[doggeface]

[b]I have now finished converting a new unit to P4. This was an interesting exercise which involved changing just the wheels and axles (and transferring the driven gear). All of the motion and cylinders remain the original.

I decided at the outset that I would split the cylinder block and remake it 2mm wider. This was easily achieved using 2mm thick plasticard inserted and glued into the horizontal ways of the original block. This provided the clearance on the front between crank and crosshead but even this demanded the reversal of the crankpin nuts (Gibson type). The wider assembly needed the running board angle framing to be removed in way of each cylinder.

The end result looks quite good to me. [/b

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]

Showing the cutaway area.

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The underside detail of the widened cyl block. A view of the cyl block mounting:

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Detail of the original motion bars fitted with Gibson 4800 bushes. These are a direct fit.

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The finished chassis.

A slightly better view of the same:

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This view shows the 2mm material which forms a very strong arrangement.

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The rather blurred shot is attempting to show the rear pony spring arrangement. I realised that there was no need to retain a head on the bolt which passes through the body floor and into the truck as it is always compressed. To enable removal quickly by removing the swivel bolt I removed the swing pin head.

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The finished chassis:

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Having a set of Gibson wheels in stock with 1/8" axles it is worth noting that they fitted without pain into the ways provided for the original 3mm axles. The builders tolerances are very generous!