Old HST ringfield motor back to back problem, gears not engaging

[North Cowes]

I have an ebay purchased, Old Hornby Swallow HST power car. Never run on DC and converting to run on DCC.

 

I have updated the ringfield motor with the excellent Strathpeffer motor kit.

 

When I reassembled I pushed the wheels on the driving axles to fit. Not related to changing the motor type, as i removed the wheels to clean away decades of grime. When run it derails over points, when I checked the back to back it was 13mm.

 

If I set the back to back to 14.5mm there is so much movement on the shift, the driving gears disengage on the curves.

 

Has anyone seen this problem before? Is there a solution?

 

Thanks in advance for any support.

[JSpencer]

The back to backs on these old HSTs was a lot closer than 14.5. More like 14.2 or even 14.1.

[Dagworth]

1 hour ago, North Cowes said:

Has anyone seen this problem before? Is there a solution?

A couple of shim washers on the axle behind the non-geared wheel.

 

Andi

[andyman7]

I've done so many of these I can set the back to back by eye. It should not be tight against the bearing but their should not be so much float that the gear can disengage. As JSpencer says the nominal B2B is about 14.1mm. I do find shim washers added in some cases by previous owners but personally have not found them necessary if the gap is set correctly. 

[cessna152towser]

Around a year ago I bought a 1978 Hornby BR Freight set, untested, from a local antique shop.    All in new condition.   The loco was a class 25, D7596, with the Ringfield motor bogie, similar to the one on the Hornby HST of that era.   On bringing it home, I found that the motor ran perfectly but the gears did not mesh with the gears on the axle.   Easily fixed with thin perspex shims and D7596 has proved a reliable workhorse on my layout.  One can imagine the sheer disappointment forty years ago when some child got a train set for Christmas and the engine wouldn't move so it was stashed away unused for many years until an eventual house clearance!

[andyman7]

It also showed up the divide between households that could repair things and those that didn't. The quality of goods was much more variable in those days (think of cars!) but fortunately my Dad was excellent at repairing and improving things. 

These days, a model railway loco is very likely to work properly out of the box, but if it doesn't the fault is likely to be in a PCB or a tiny hairline solder. I've had my share of repairing those, and find it quite stressful, and in terms of pleasure, a crude, push-and-clip together Ringfield is much more enjoyable to work on where I will likely know straight away what the fault is and how to tackle it... 

Edited May 18, 2021 by andyman7

[Barry Ten]

I glued a thin piece of plastic card under my 9F tender drive to cure this problem, just bearing against the wheel. Crude but it worked.

[North Cowes]

Thanks for all the replies. When I get 5 minutes I will be heading out to the shed to find/make some washers.

 

I will let you know how it goes. 

[dmu 156]

8BA or 2mm brass washers are perfect for this job, you can set your back to backs at 14.5mm which will leave tiny amount of play in the axle. Eileen's Emporium sell them in packs of 20.

 

[North Cowes]

Thanks for all the recommendations. I made some washers from PTFE and they seem to have done the trick.