Ron's Jowitt Popett Valve Engine

Having a tea break, I have been playing with the engine for over 3 hours and cant get it to run, something is amiss but I cant fathom what.

Is there any sign of the piston moving on the power stroke away from the head?

Have you plugged the holes on the outside of the cylinder?

Edited By JasonB on 01/04/2020 16:20:13

Yes Jason when I flick it over it sometimes manages an extra rotation on its own as if its almost there. Also with the air on if I slowly turn it over I can feel what seems to be good compression as the piston approaches TDC..

Edited By Ron Laden on 01/04/2020 16:28:01

Yes I have the holes plugged, how critical is the timing..?

You should not be able to feel any compression or air trying to push the piston until you are over TDC

Inlet valve should open just after TDC and close say 20 degrees before BDC.

Exhaust wants to open at or just after the inlet closes so open at 20deg before BDC and should remain open until the piston is back up at TDC

Jason, I reset the eccentrics and I have the engine running but I only have one speed (slowish) but at least I have it running and have had it running for half an hour now.

I know the crank, big and small end are all good so I am guessing the O ring is holding back the speed, do they take much running in. I am hoping that once it gets easier I will be able to fine tune it and get variable speed.

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You could try it without the O ring.

If your springs are a bit strong that won't help either as they will be taking engergy to compress, the inlet can be lighter than the exhaust.

I did try it without the O ring but couldnt get it to run, I,ve checked the springs and think they are ok.

A bit of handheld video below of what I have at the moment, it is certainly a bit better for some running. Going to give it some longer runs and see if it beds in some more. Despite the teething problems I am quite happy with it and hopefully can get them sorted.

p.s. apologise for the sound of the compressor, I need a longer airline to get it off the bench.

Edited By Ron Laden on 02/04/2020 16:06:45

How big is your compressor Ron, could that be the limiting factor?

Looks a very nice engine.

Looks to be running smoothly enough so I would also say you may be at the limit of what your compressor can deliver, the volume is about 50% more than the oscillator that you did so will be a bit hungrier.

Thanks Clive/Jason, I think you are right it did cross my mind but thought it was the engine being tight and not set up correctly. The engine is now set correctly and spinning it over it feels really good, smooth and free so I,m sure it is now ok.

My compressor is an on demand type it doesnt have a tank, it is rated as 40psi and 0.8 cu ft per min. Using it to run the little oscillator it switched on and off but with Jowett it is running full time so I guess thats a sign that it is at its limit.

Anyway, now I know the engine runs ok I will sort a new compressor it will be good for shop use as well.

I dont want a largish type with a large tank, I dont have the room so would have to bring it into the shop when needed and then store it somewhere else.

I have found a bench type compressor with a 6 litre tank, 8 bar and 6.3 cfm I,m guessing that should be fine..?

That should be a lot better

Thanks Jason, thinking of getting one of these, should do the job and quite compact can live under a bench.

Edited By Ron Laden on 03/04/2020 08:33:56

Made some further adjustments and I am really pleased with it, yes its a bit starved of air hence the need for a higher output compressor. It starts first time every time so the settings must be pretty close a bit more video below.

The Muncaster wheels arrived, amazed at how clean the castings are..excellent.

Is that hole open?

Also make sure the brass fittings don't have too long a thread which could be blocking the hole from cylinder to valve chambers.

Edited By JasonB on 03/04/2020 16:20:16

No Jason it has a M4 grub screw locked in there and I will fill over the top on finishing. Also the fitting threads are short of the cylinder hole.

Edited By Ron Laden on 03/04/2020 16:42:58

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