Heatshrink sleeving as a heat insulator for valve handles?

I have run my Kingscale Std 4 for the first time and all went well except for the fact that I found the handles on the steam valves too hot to handle.

Can an kind member let me know if say two layers of heatshrink sleeving on the handles would help? This would be an easy solution as the handles are straight.

The gloves I had on simply melted where covered with grip rubber.

Just do what the big boys do and use rag or wear leather gloves! Aside from that and following full size practice also, fit wooded handles.

Paul.

Even one layer would help to reduce the rate of heat transfer.

Personally, if I was thinking of two layers, I would use one heat shrink sleeve over an inner layer of insulation. Got to be better if the right sort of insulator is chosen.

The ATUM range of heat shrink tubing should be better than standard as it has an internal layer of hot melt adhesive that would secure it to the surface it was on.

Martin C

Silicone tubing as used for model aircraft fuel tube is perfect for this problem. Unaffected by the temperatures involved and a good insulator. Comes in a variety of bore diameters, wall thickness etc and easy to slip on for use.

Not particularly visually aesthetic it's easily removed after use and can be used over and over.

Tug

Handles used to be "Sleeved" with Tufnol.

Regards Ian.

Hi Ian

Tufnol was my first thought but will try the heat shrink tubing first as much easier to do. A friend made his handles in Tufnol but it is almost a clockmakers job to achieve the very fine square sockets that my loco requires.

Two wee points about heatshrink: one, it only shrinks to about 50% of its size, so it needs to be carefully sized for the part. Second, over time it will lose the inherent tension it has when shrunk, and can slip if it's not mechanically secure.

I'd give the silicon tube serious consideration - it's easy to find in various sizes and colours and should be ideal, I would think.

ATUM of similar glue lined hestshrink is not a good idea as the glue will soften with heat.
Silicone rubber tube is a good option. The only issues are that it tends to be thick wall and most types have poor resistance to oil and grease.
If you want to try heatsink I'd suggest Raychem DR-25. This is a durable thick wall tube and will give reasonable insulation. As Calum points out it can loosen with time. The best solution for this is to use a thin layer of epoxy under the heatshrink. Try it without and if happy but it loosens replace it and use epoxy.

Robert G8RPI.

I agree with Robert that glue lined heat shrink is not a good idea as the glue will get soft and slippery every time the handle gets warm.

I wouldn't suggest an epoxy layer under the heat shrink tube, as there may be some chemical reaction between the epoxy and the heat shrink tube. Heat shrink tubes are mainly made from cross linked polyolefins, a long time reaction such as brittleness can not be excluded if they are in long time contact with other polymers, especially under elevated temperatures.

I would suggest to apply a heatshrink tube (or more then one) direct over the metal handle, or, if possible, produce wooden sleves which go over the handle.

Edited By Gerhard Novak on 27/09/2021 15:35:23

Just so you know, non adheasive heat shrink is 2 to 1 and adhesive heat shrink is 3 to 1.

regards Martin

Edited By Martin Kyte on 27/09/2021 15:26:46

There is a yellow plastic tube available very similar to the silicon tubing mentioned in earlier posts that is resistant to petrol. It is used on garden machinery for fuel feed from tank to carb. I have seen two sizes of it, may be more available but the larger one should do the job.

Seems to me this is one of those things (not uncommon here) that's easier to try than to spend two days discussing it.

My own feeling is that the material is too thin to be of much help even though it may be nominally a thermal insulator. Like the insulating washer between a power transistor and heat-sink. The washer material is actually an excellent thermal (as well as electrical) insulator - but at the thickness that is used it hardly matters.

I’m for the tufnol ones like these