Radio control servos

[michael howarth 1Participant @michaelhowarth1]

What sort of servo and linkage do I need to control a rotary (screw in-out) steam valve. About 200 degree movement of the screw would be ideal.

Mick

[michael howarth 1Participant @michaelhowarth1]

[Ray Wood 3Participant @raywood3]

Hi Mick,

You could try a retract servo for a model aeroplane, they traverse 180 deg but you may only get open or closed .

Maybe try the 16mm narrow gauge society as they have rc controlled regulators.

Regards Ray

[michael howarth 1Participant @michaelhowarth1]

Thanks Ray.

Mick

[TelstarParticipant @telstar]

Hi Mick,

If you fitted a small sprocket to the hand wheel of the valve you could use the chain (like the old style Meccano chain} and attach a larger sprocket to the servo disk (about 3 times bigger, ) giving the needed movement,

Just a thought

Tom

[michael howarth 1Participant @michaelhowarth1]

Thanks Tom. All ideas welcome.

Mick

[Richard SimpsonParticipant @richardsimpson88330]

Do you not think it would be easier to control using a ported valve rather than a screw down valve? You would only require 90 degrees of servo movement then from full open to full closed and a standard single linkage from the servo arm to the control valve arm.

I would not recommend a screw down valve for engine control mainly as the response will be no where near linear and fine control for manoeuvring will be very difficult to achieve. Ported valves are designed to give linear response making control of your model considerably easier.

[michael howarth 1Participant @michaelhowarth1]

I like this idea and have considered it Richard and indeed I might well go down this road. I am also experimenting with making tapered plug cocks which would also require only 90 degree movement. This is my first "boat build" and I have been transferring elements of model loco design (with which I have some experience in Gauge 1) and trying to make it fit the boat. Some things will work but others perhaps not. It seems to have gone quite well so far though. By tinkering with the screw down valve actuating arm design I have now got something workable but not perfect. Another transfer from loco building that has not come off is the incorporation of a miniature feed-water pump to the boiler. I have found that the advantage of extra feed-water (extra running time) is virtually cancelled out by the amount of steam required to work the pump. Not to mention the difficulties involved in controlling the bypass remotely. I have now opted for (another loco element), a simple low boiler water LED indicator on the boiler. This gives me about 25 minutes run time plus 5 minutes warning…….sound reasonable ?

Mick

[Ray Wood 3Participant @raywood3]

Hi Mick,

I'm also a G1MRA member having built a Project 0-6-0 a few years back, the regulator works well through 90 Deg as I recall with a course thread 5" gauge drain cocks are also handy, I guess that's what you have made??

Regards Ray

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