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Part built Allchin 1.5 inch

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Jeff Dayman10/09/2019 23:37:11
1596 forum posts
39 photos

Exh pipe for the Allchin in bronze should be ideal material, I would say.

derek blake11/09/2019 12:41:46
428 forum posts
116 photos

Thanks Jeff

derek blake14/09/2019 21:59:33
428 forum posts
116 photos

Evening all,.

now my next question has been asked many times and I’ve done my best to work this one out myself, however.

if my piston is central in the bore, should my valve slide be central as well? I’ve set my eccentrics only by eye at the moment and I can get the valve to move across the ports equally if I reduce the length of the rod which makes sense as I had to reduce the piston rod length also to get that to a good position.

if I know the piston position relative to the slide valve I could check if I’m in the ball park, I have read all the posts about TDC and 90 degrees and read the book but mathematics is not my strong point, is there a real basic way to position the eccentrics on the crank,

kind regards


JasonB15/09/2019 07:03:38
16045 forum posts
1684 photos
1 articles

Looking from the flywheel side.

Set the crank so that the piston is towards the front of the engine, this will put the crankpin at 9 0'clock.

The thickest part of the forward eccentric should then be about 10 degrees past noon. Just a sit is on drawing No6

The thickest part of the reverse eccentric should be at about 10 degrees before 6 o'clock which is hard to see on drawing 6.

derek blake15/09/2019 08:30:58
428 forum posts
116 photos

Hi Jason

Many thanks as that seems a simple explanation, just checking if I look from flywheel side and move piston to the front of the bore towards the chimney would that not put the crankpin at 3 o clock? I’m obviously not questioning your correct I’m just checking I understand it correctly,



derek blake15/09/2019 09:45:40
428 forum posts
116 photos

Sorry Jason, I can see it’s 9 o clock now I have engine in front of me, I shall give it a go today.

thank you

derek blake15/09/2019 23:12:18
428 forum posts
116 photos

So I had my first go at setting the eccentric with Jason help and a few pictures, it seemed pretty good.

however when I push the linkage to the top which I’m not sure is forward or reverse the lifting arm badly rocks forward and back.

but doesn’t in the other position, slightly odd but is probably clear to someone that something is out.

i will have another go tomorrow to make it more accurate as I’ve obviously not got it correct yet...

derek blake16/09/2019 23:51:42
428 forum posts
116 photos

So I had another go at setup, probably a weird way but I printed a circle with the degrees added and attached this to the gear on the crank.

i move both the eccentrics the 10 degrees as told, and I’m pretty sure they are in the correct position now or at least the best I can do, I do still get rock on the lifting arm but when I held this tight with the push rod it stopped so maybe this is normal.

moving the eccentrics didn’t seem to help the rock so I’m assuming it’s maybe something else or just how the mechanics works, this week I will make a new rod for the slide valve as the other I cut slightly too short.

and see how the movement is, my intention will be to run on air to see how things go, hopefully this week would be nice.

probably just with a foot pump for now, and if the engine comes alive not only will I feel a sense of accomplishment I will spend time making the steam fittings, I will change that into attempt to make the steam fittings...

JasonB17/09/2019 09:24:05
16045 forum posts
1684 photos
1 articles

Things will move about if the whole linkage is not in place back to the reverser, can't seem to get the embed code to post video of mine but so here

Ron Laden17/09/2019 09:32:05
1307 forum posts
224 photos

Excellent Jason, I am getting lots of information from that video, seeing how things run, fit and how they look.

Edited By Ron Laden on 17/09/2019 09:43:59

derek blake17/09/2019 10:02:21
428 forum posts
116 photos

Many thanks Jason, that's great

derek blake19/09/2019 21:08:54
428 forum posts
116 photos

So to add a little variety to the engine build I’ve decided to attempt two extra model, a living van and trailer scratch built from pictures.

very early stages but a bit of fun, if they end up looking half decent I shall sell them to fund engine parts.


derek blake19/09/2019 21:09:13
428 forum posts
116 photos


derek blake19/09/2019 21:20:58
428 forum posts
116 photos

Only progress on engine is a new valve rod, as other one was too long.

piston rod and valve rod have had to be made shorter, I’ve lost around 2.3mm on length of boiler if I was to copy drawing exactly so it’s possible this is the answer to why I’ve had to shorten both rods but hopefully this won’t make any difference to the running of the engine.

I am presently blanking the steam fixings to attempt to run the engine on a foot pump as the book suggests, she will either come alive, not run, or leak like a sieve.

i think I have set the eccentrics correctly from Jason’s help and the movement on the valve looks reasonable so let’s see.

if we have life I shall take a short YouTube video.

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