Part built Allchin 1.5 inch

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

Thanks Jeff

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

Derek

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.

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,

regards

Derek

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

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...

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...

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

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

Many thanks Jason, that's great

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.

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.

So I had a quick go with the foot pump tonight, and yes of course it leaked.

air seemed to just get pumped straight up the blast pipe, maybe regulator not seated? And my safety valve leaked badly also.

i will do a better sealing job Sunday and try again, I’m not really worried about seeing engine work I’d like to just my mind at rest that the cylinder is sealed.

any advice on why air goes straight up the chimney and why the safety valve leaks would be greatly received.

regards,

Derek

I'd be looking at the valve if it is going right through the engine and out the blast pipe.

One problem with a foot pump is that it won't give much initial pressure that is needed to hold the regulator puck and valve against the port faces, if you have a small compressor that would be better.

A car tyre foot-pump isn't ideal for testing engines because they produce low-volume bursts of air at high-pressure when the engine wants a steady flow at moderate pressure. The pressure may be enough to lift the safety while the bursts fail to seat the valve properly.

Try making a couple of pipes to fit in the cap of a 2 litre lemonade bottle. Connect one to the pump and the other to the engine so the bottle acts as a reservoir. The bottle has the effect of reducing pressure and increasing flow to match the pump to the engine better.

Dave

Right OK, thanks Jason.

i will do a bit more work before trying again and look to see if you can buy a quiet air compressor.

Thank you Dave that’s very interesting info, I will see if I can find a cheap small compressor.

Derek,

a low cost alternative for testing purposes - if you can lay your hands on a car wheel and tyre, bodge-up a screw that will fit tightly in the end of a plastic aquarium-type tube, flatten two sides of the head to allow air to pass and position the head of the screw to depress the pin on the Schrader valve when the tube is pushed on. You can adjust the tyre pressure to suit. Good for a few attempts to run/seal whilst you wait for a compressor.
DaveD

Edited By Meunier on 20/09/2019 20:49:04