Part built Allchin 1.5 inch

Right here we go.

First sketch is what you currently have on the top and the book sizes at the bottom with valve at the mid point.

And now at full valve travel. With the large amount of lap and the overall width of the ports not being that different you will get fairly similar running. I would be inclined to leave as is for now.

If you do find it won't run well then it is not too hard to change the valve at a later stage, this has the top valve reduced in overall length an the cavity reduced, at mid point

Part way along the inlet now opens at the same time as the drawing version

And at full eccentric throw

If you do decide to alter it then the overall needs to be 19.78mm and the cavity 10.34mm, you could solder in some metal to reduce the cavity of just make up a new valve from scratch.

Thank you so much Jason.

I'm really surprised that it would still work with the valve not fully covering the exhaust when in mid point, but that's why I'm not an expert but I do need to learn how it all works.

I will leave alone for now then and see how we go, are you saying that the cylinder block will be fine and the only thing we would need to change is the valve itself? which of course would be a lucky escape for me.

many thanks again for taking time to look into this for me.

what I have found is the valve casting cavity is actually oversized compared to the drawing anyway, and that was without me even touching it.

I guess the casting just wasn't very good.

Yes the cylinder can be left as it is. You may loose a bit of economy and power but the little Allchin is not the type of engine that is going to be rallied every weekend and expected to do road runs.

Thanks very much Jason, and everyone else who commented.

Just one last question, if you wanted to use the valve casting I have but reduce the steam cavity how would YOU go about it?

Thank you in advance

You could silver solder a piece of similar metal into the cavity.

Probably even be OK to use something like JB Weld to build up the edge and then that is easy to trim back to size, should take the temperature OK.

Another option would be to file off the lower half and then make a new piece with a suitable hole in it and then silver solder that back onto the top half. I've made a few valves that way.

Right ok I'm with you, the steam cavity itself has an angled curve within is that critical and must match drawing? sorry for all the questions but trying to learn.

Does not have to be shaped

I wouldn't think so. The cavity only controls the exhaust, steam inlet is controlled by the outside edges of the valve. In theory you might want a small radius on the internal corners of the cavity to reduce turbulence. But in models where efficiency is unimportant it's not necessary.

Andrew

interesting, thanks very much guys its great to be able to learnt about these things.

I find that a joy to understand what I'm doing.

Good morning all, hope everyone safe in this snow.

Many thanks again for the help with the slide valve issue, exhaust hole now drilled from centre port to base of cylinder.

Side hole I’ve not drilled yet as I’d like to have boiler and chimney together first to make sure all lines up, so the next two or three main stages are the regulator port in the top and the boring of the cylinder.

Unfortunately even with all the will in the world I cannot do these operations on my lathe as there is just no way to clamp cylinder to it.

It’s just too small and to be honest if I go off line I’ve ruined hours of work, with thanks to all on here I’m half way through the build more than I ever thought I would be and I’m proud I’ve got this far.

However I am going to have to ship out for these two three operations, bore cylinder, mill regulator port area and drill connecting steam ways from bore to valve face.

I’m not expecting anyone to be able to talk about machine shops on the forum but if anyone has used someone and can recommend there work please could you PM me, my original quote was £740+VAT im hoping that I’ve reduced that slightly now but doing the work I’ve done.

I’d love to get this cylinder finished, and if that means I hand over for some precision finishing that’s fine by me as I never thought I’d get this far, it’s the confidence and help of this forum that I’ve got this far.

Many thanks

Derek

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Thank you Bill, that’s very kind

Couldn’t resist seeing how it may all look, just stuck trunk guide on with some double sided tape, fingers crossed everything will line up.

Evening all

Little bit of work done tonight, thought I’d have a go at the Pickering governor gives me practice at least on the lathe.