Globe Valves

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Globe Valves

Post  LiveSteam on Sun 28 Jun 2015, 3:03 pm

When I bought my MW 4" it suffered from leaky globe valves and talking to others the early engines seemed to.

I looked about and wondered about replacing them with either new ones or these pfte types, and then wondered if I could knock up something myself, well may be not actually me but ask a mate to do a bit on his lathe for me, so bought some PTFE rod and we then set about butchering the cones on the valves to make them accept a small PTFE washer.

Below is the result



Then we then drilled a hole in the rod and paired off a number of small washers and they are a interference fit on the end of the valve head  Cool





I've been running with these now for best part of a year and thought I'd take one out to see how its fairing, so heres a shot of two washers the right hand one is old and the left is a new one.



Its flattened out a bit but nothing that causes me concern and I've got a dozen spares that we made at the time but apart from today I've never changed one of them, and even now I dont think this one needed changing just as I had it out I thought I would.

The ability to turn the valves on and off with almost one finger is a pure joy and they never leak even a wisp of steam, and no worries of them ever sticking when the engine cools.

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Re: Globe Valves

Post  Kevster on Sun 28 Jun 2015, 10:36 pm

Looks a good mod to do ,
Kev

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Re: Globe Valves

Post  LiveSteam on Mon 29 Jun 2015, 12:25 pm

Well I wasnt sure if it would work due to the possible temperatures because the melting point of PTFE is just above 300C but I thought it was unlikely to get that hot, but hoped they wouldnt go all squidgy above 180 as I've measured those sort of temps on the boiler before now, but they dont seem to.

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Re: Globe Valves

Post  mikero on Mon 29 Jun 2015, 2:45 pm

I have seen smaller engines with PTFE piston rings that were CNC milled as a spiral spring about 0.5mm thick giving a ring 2mm thick.

Mike

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Re: Globe Valves

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