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Fitting Hornby Coupling Rods to Gibson Wheels


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Hi all,

 

I recently bought a half finished Hornby Ivatt 2mt upgrade project off Ebay which has been fitted with Gibson wheels but still came with the original valve gear/connecting rods etc. Annoyingly, the plugs (I don't know what else to call them, sorry!) on the outer ends of the connecting rods don't stay in the holes on the wheels when the chassis is motion - is there a good way to stop this from happening or would it be better to just buy new coupling rods from Gibson? I've included a picture below to illustrate. Sorry if this is a silly question - I'm slowly building my way up through chassis building/restoration etc. so am still learning!

 

Thanks

 

20210104_151827.jpg.c659541cffb7edcc69c625eaa1deed22.jpg 

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They look like Romford wheels as they have the axle nut on them. 

 

Unfortunately, we dont know if the previous owner opened up the crankpin holes to accomodate the rtr crankpin. 

 

You could try threading a BA 16, 14 or 12 screw from the back and tightening the rods with a nut. I am no expert in this area so i am sure you will get a much better response from those that are.

 

To add. You may need to countersink the screw into the rear of the wheel so it doesnt catch the chassis, and cut a thread so its a good fit, then solder the nut and file smooth once you are happy it all works smoothly with no binding. 

 

It may be easier in the long run to get a replacement wheel set from Peters Spares or ebay.

 

Ian

Edited by ianLMS
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If they are Romford/ Markits wheels, which is ones held on with a brass slotted nut and fitted over a squared axle end then you may well have ruined the crankpin threads in the wheels.   I have done Romford conversions on several of these chassis , 43XX, 78XX and 74XX Bachmann bodies on Triang Hornby chassis. I source 4 Triang coupling rod screws from the M7 or Nellie  which I believe are 10BA and some 10BA washers. I Punch the "Plugs" fronm the rods while supporting the rod around the outside of he "Plug" and the pins should fit neatly, or need minimal opening up.  File the point off the crank pins beyond the threads as the Romfords are thinner than Triang wheels and put a thin washer between rod and wheel to keep the rod off the wheel tyre. Fit these screws to front and rear wheels.  For a walchaerts valve gear  I would bodge return cranks etc  on the centre wheels using your existing crank pin . 

However the drawback is limited clearance between rods and wheel tyres, you can't have any side play much without the rods fouling the tyres and shorting out so you really need 24" minimum radius, or fit flangeless centre wheels. Mine have to get round a 3rd radius so run fllange less centre wheels. 

You can bush the rods using Top Hat pin point bearings filed and drilled  and use romford crankpins to give sideplay but I found the soldered on bushes work loose and the pins snap if the loco derails.

As Bcjmann make a much better Ivatt maybe sell the Romford wheels, the motor and body separately on eBay and buy the Bachman.   That's basically what I did with mine built pre Bachmann detailed with separate handrails etc and with a drastically shortened Tender Romfords etc, except the chassis went under my 74XX...

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The original centre wheels had a long boss over which the coupling rod fitted, followed by a spacing washer and then the connecting rod. The whole lot was then retained by the return crank which was held in place by a tiny screw. the crank pins on the outer axles just rest in the holes in the wheels and are retained by the centre axle assembly (a bit of a bodge, but it does work).

Here, I would suggest a nut on the threaded rod centre crankpin, held firm by locking compound and then the return crank soldered to secure the connecting rod.

Some play will be necessary to allow the chassis to go around curves. Trial and error will show how much.

The service sheet for the original chassis is here:

 

http://www.hornbyguide.com/service_sheet_details.asp?sheetid=10

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