Poppet valve info

[John HollowayParticipant @johnholloway99594]

Hello all

this is my first post so please be gentle, I am trying to get the valves on my first engine to seal but am having problems.

Hopefully I have attached the pic’s of the valves (drawings) I don’t think I will be steaming this engine it will only run on air so does anyone have any suggestions on how to get these to seal or would it be better to redesign the valves to incorporate a silicone/rubber “o”ring.

many thanks in advance

John

[John HollowayParticipant @johnholloway99594]

First silly question

[JasonBModerator @jasonb]

The main things are to make sure the features on the valves are concentric with the stems so try to do all the machining in one set up. Also you want the stems a good fit in the guides.

Likewise the seating in the valve body needs to be concentric and should ideally be cut with a D bit to give a good crisp edge.

[John HollowayParticipant @johnholloway99594]

Could you please tell me what a D bit is please

[John HollowayParticipant @johnholloway99594]

Thanks I’ve checked online and found D bits next is to order some

[duncan webster 1Participant @duncanwebster1]

Make your own from silver steel, it's easy enough and a good learning exercise

[John OlsenParticipant @johnolsen79199]

I've only made one steam engine with a poppet valve, a uniflow with a poppet valve inlet. I think for this sort of thing, the seal on the valves is not going to be as critical as it would be for an internal combustion engine. I don't recall going to any great trouble with the valve for mine, although the seat and the guide would have been machined on the same setting.

John

[John HollowayParticipant @johnholloway99594]

Many thanks everyone for the feedback,

I have stripped the 4 valves down and checked them and they are seating very well, I now see that various threads are leaking and the timing and settings are out so this is the source of the problem.

I have done some rough timing and the engine is trying to work, so the next thing to do is the setup of the multitude of linkages and timing, once I have got my head around it.

Many thanks again and I will be making some "D" drills in the future.

Onwards and upwards

All the best

John

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