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Long tender means the controls need extending

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terry callaghan04/09/2019 13:07:24
186 forum posts
5 photos

hi. I am coming to the end of my Martin Evans designed Columbia, and need some help. The tender is very long and there is no way I will be able to get to the controls. I have figured a way to extend the regulator by using a Bowden cable. But what is the best way to extend the injector valves. Thanks.

Brian G04/09/2019 13:56:43
586 forum posts
25 photos

Could you use a radio control servo and a servo tester to work the valves. I have seen this solution work for Columbia's regulator.

Brian

terry callaghan04/09/2019 14:48:29
186 forum posts
5 photos

Hi. Not to sure that would work due to the heat, and I would always worry about fire from the firebox catching any servos.

Nigel Bennett04/09/2019 15:16:04
297 forum posts
11 photos

I could lend you a hacksaw to shorten your tender...

I've seen quite a few contrivances to operate loco valves from the rear of the tender. It usually involves a number of controls attached to a cross-plate secured to the tender. The controls are usually rotary (for steam valves) and generally involve a long operating rod provided with a couple of universal joints. The "loco end" of the long operating rods also need some kind of bearing/support.

There needs to be some provision for changing the effective length of the rods as the tender and loco negotiate curves. This could be a pin through one part of the rod and a slotted tubular section on the other. Water valves can be sited at the rear of the tender so that their operating valves can be sited where it suits you.

It depends on how you feel about your loco; if you want it to look realistic when you aren't using it, then it would be an idea to have all the jiggery-pokery removable - but that will add to the complexity of the design.

It does need very careful thought to make the regulator control safe; you don't want to be faced with the loco running away and you being unable to shut the regulator. Hence give a bit of thought to fail-safe design of the linkages so that if the loco-tender coupling parts, then the loco will coast to a halt.

You've got a big task to operate a pole reverser remotely, but a screw reverser might be susceptible of remote control.

My advice is to stay away from electronic/radio operating devices and use something mechanical.

terry callaghan04/09/2019 15:21:02
186 forum posts
5 photos

Thanks Nigel. Lots of input. I have spoken to a chap using a Bowden cable for regulator and it clipped onto the rear wall of the tender. However as you stated the injector controls would be a lot harder to deal with. I like the idea of placing the tender controls at the rear. Thanks. Michael

Nigel Graham 220/09/2019 23:23:07
386 forum posts

Re the effects of curves on control-rod lengths.

I propose it might actually be negligible, and certainly easy to accommodate.

Even at this loco's curve limit, the linear movement will be small enough to allow the rod to slide through a bush; but you could make a short telescopic section based on either a slotted tube and cross-pin, or small-section square tube and bar.

I'd think the injector steam valves the easier, not harder, to arrange, assuming they are on the turret and have spoked-pattern hand-wheels.

Lever-type reversers: I have seen an extension control used on a miniature traction-engine, I think based on a tube ending in a clevis gripping the handle, and an internal rod that operated the trigger, with a suitable grip and push-button on the operating end. A Bowden cable might work but would need a return spring on the lever.

duncan webster21/09/2019 00:12:03
avatar
2226 forum posts
32 photos

If you got to **LINK** and scroll down you'll find video of a RC 5"g loco. Only the regulator, but it works a treat. Having said that if you're riding behind anyway, I'd use a more direct method, no need to over complicate the issue

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