Slaters Crankpins in 7mm - Hudswell Clarke diesel shunter

[John Tomlinson]

I wonder if I might ask the advice of those with experience in 7mm.

 

A little while ago I started my first "O" gauge loco kit, a Mercian models Hudswell Clarke diesel shunter, as found particularly in Birkenhead. After assembling the basic chassis in a jig and the basic body, I paused awaiting sourcing motor and gearbox which I did at Kettering. Work resumed, and assembling the three deep coupling rods re-affirmed what others before have found, namely that the holes aren't quite right compared to the chassis. Yesterday I very carefully filed out the holes in the rods to correct the error in the etch, and also split and laminated the rods, and now have a nice, free running chassis with articulated rods. This is running on the threaded screw of the Slaters crankpin.

 

As you'll all know, the Slaters crankpins have a brass "top hat" bearing to fit over the screw and inside the holes in the rods. If I enlarge the holes sufficiently to allow this bearing to fit, there will be little or no material left on some of the holes. So my question is, particularly as this is a diesel shunter that won't be required to do much, can I just leave off the "top hat" crankpin bearing and let the rods sit against the screw part? In retrospect I could have avoided this by moving the axle holes on the chassis, but in fact there isn't much spare material for the crankpins on the rods anyway, even if the holes had matched, and of course its easy to be wise after the event.

 

Many thanks,

 

John.

[Michael Edge]

You can but the screw thread will wear the coupling rods faster - depending on how much running the loco does this might not matter much I have some 4mm locos with coupling rods running directly on steel screws (Sharman wheels, same problem with the bush being too big) which have been running for more than 30 years now. You could try sleeving the screw with some thin walled brass tube which might leave enough meat on the rods.

[doilum]

Two possible routes.

First a phone call to Trevor at Mercian Models. I have found him to be amazingly helpful.

Second. You seem to be well on the way to mastering the black art of locomotive motions. Time to have a go at scratch building a set of rods. 

Either way you might consider buying a. Set of 10 ba taps and uprating the Slater's wheels to the larger size. This way you thread the bushes and use them instead of nuts.

[Marshall5]

7 hours ago, doilum said:

 

Either way you might consider buying a. Set of 10 ba taps and uprating the Slater's wheels to the larger size. This way you thread the bushes and use them instead of nuts.

Wasn't the OP's problem that there was insufficient 'meat' on the rods to allow the use of Slater's bushes?

I'd tend to agree with Michael's suggestion of soldering some thin wall brass tube into the rod holes to act as bearings.

Ray.

[david.hill64]

A generic learning point here is that it is always a good idea to build up the coupling rods first and use these as a template to check that the axle bearings are in the correct place. It can be easier to make adjustments to the frames (elongate the holes) than to the rods. Use an alignment aid appropriate to the scale you are working in.

 

This is often an issue with older designs where the artwork was hand drawn, but rarely so with modern CAD work.

[doilum]

10 hours ago, Marshall5 said:

Wasn't the OP's problem that there was insufficient 'meat' on the rods to allow the use of Slater's bushes?

I'd tend to agree with Michael's suggestion of soldering some thin wall brass tube into the rod holes to act as bearings.

Ray.

That's why scratch built rods would be needed

[John Tomlinson]

Thanks to all of you for your informed and very helpful comments.

 

Having already made up the rods and spent a fair time cutting and filing them to articulate, I think on this occasion I'll take the easy way out and try the loco just on the steel pins, and if I can find some thin walled brass tube I'll go for that instead. The idea of scratch rods is a good one, and an idea in the back pocket for future projects. As Dave Hill says it would have been better to adjust the frames in the first place - learning by doing!  My next project will be a Gladiator C13 bought from Dave's predecessor and I'm hoping that will be a relatively straight ride.

 

Thanks again.

 

John.

Edited April 9, 2020 by John Tomlinson
typo

[Michael Edge]

I think that will be a lot better.