Revolving crankpins

Bilton Junction
Posts: 34
Joined: Wed Dec 31, 2008 1:02 am

Revolving crankpins

Postby Bilton Junction » Thu Jul 15, 2010 11:17 pm

What is the easiest way to stop crankpins revolving with the return crank? I am using Gibson wheels which I don't really like because the crankpins have sliding top hats and I have had this problem before. I used Loctite and this time I even reinforced the screw head with a blob of Araldite. I have read about Chris Pendlenton's method of a made up top hat with a flat on the inside to engage with a flat on the wheel boss but that seems to require a high level of skill. I also tried John Hayes method of drilling the screw slot to insert a pin but stainless steel is awful hard and broken drills in the finger tip are quite painful :o Is this problem peculiar to Gibson pattern crankpins or does it also affect the Ultrascale pattern and the new Exactoscale pins that sit in aluminium bushes? Any solutions would be gratefully received as I am reluctantly coming to the conclusion that Walschaerts valve gear is best avoided.

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Forum Team
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Joined: Sun Jun 29, 2008 8:02 pm

Re: Revolving crankpins

Postby grovenor-2685 » Fri Jul 16, 2010 7:18 am

Fixing return cranks is a definate problem area and no current crankpin supplier offers any real attempt at a solution. IMHO reliance on solder is a no-no with plastic wheels, glueing is very difficult with such small parts, and some other suggested solutions such as filing the back of the nut until it is tight at exactly the right angle don't work for me.
An enterprising manufacturer who can come up with a proper engineering solution will get an ovation.

Meanwhile study what Bachmann and Hornby do and see if you can improve on it. The Hornby version probably being more adaptable .
Grovenor Sidings

Philip Hall
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Re: Revolving crankpins

Postby Philip Hall » Fri Jul 16, 2010 8:30 am

My usual solution is from one of Guy Williams' ideas. I fit a U shaped piece of brass wire into two holes drilled either side of the crankpin slot. Guy used to melt this wire into the wheel (you're not touching the soldering iron on the crankpin, just the wire, so you won't affect the pin), but I now make the wire a tight fit in the holes and secure with Hafixs cyano. I also usually substitute a brass 14BA screw for the steel one, as I often finally secure the crank with a touch of solder (!) If you substituted a brass screw you might find it easier to drill for John Hayes' method. He was using Ultrascale wheels, I think, and of course their crankpins are brass.


Alan Turner
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Joined: Sun Jul 20, 2008 4:24 pm

Re: Revolving crankpins

Postby Alan Turner » Fri Jul 16, 2010 8:42 am

Bilton Junction wrote: I am using Gibson wheels which I don't really like because the crankpins have sliding top hats and I have had this problem before.

Use Exactoscale crank pins - they have a threaded "top hat".


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Mike Garwood
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Re: Revolving crankpins

Postby Mike Garwood » Fri Jul 16, 2010 8:54 pm

I recent cheat that I learned, from one of our Naggers meetings, was to use Romford crank pins (used with Gibbo wheels) and solder to the retaining bush that comes with these. I have not tried this personally as I always solder to the crank pin without problem...up till now!



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Stephen F
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Re: Revolving crankpins

Postby Stephen F » Sun Jul 18, 2010 8:51 pm

Like Mike, I soldered the return cranks on my Black 5 Gibson wheels, so far so good. I used low melt, which makes removal easy if required, also on some of the other crankpin nuts to stop them unscrewing as they obstinately wanted to.
I just followed instructions screwing in the crankpins. I can't remember if I used superglue or some type of loctite, but it might be worth a try, and then glue the bushes on for good measure. Anyhow, now I've put this in writing, sod's law dictates they'll start slipping :?

Good luck with it

Bilton Junction
Posts: 34
Joined: Wed Dec 31, 2008 1:02 am

Re: Revolving crankpins

Postby Bilton Junction » Sun Jul 18, 2010 9:31 pm

Many thanks for all the helpful suggestions. I currently have one side with a crankpin screw with a u shaped wire soldered into the slot and Araldited onto the back of the wheel either side of the boss and the other firmer screw with a wire Araldited in the slot and the back of the wheel. The replies were interesting as clearly some people haven't had a problem with a revolving screw but have had more problems with the return crank coming loose on the screw. I thought that I had that problem on a K3 that I converted which was until then quite a reasonable runner. The soldered return crank started to revolve and being in a hurry I didn't waste time on the niceties of putting in a sheet of fag paper just a good splash of green flux. You can imagine the rest. Blue flux.


Re: Revolving crankpins

Postby Philbax » Wed Mar 09, 2011 5:04 pm

One for those of you into etching. :!:
How about an etched washer that fits either over the axle or over the boss on the rear of the drivers with a slot in it to solder the crankpin to.
This would fit behind the wheel, and obvoiusly would not be of a diameter that could be see between the spokes, may be more sophisticated in shape to do this.
It would provide a solid location which is prevented from turning by the fact that it is fitted round the axle/wheel boss.
It would also need to be fairly thin as it is usually the driver where you want most side to side allowance for curves.

Over to you guys

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