Mystery engine

[RayW]

What a difference a bit of JB Weld and a coat of Very High Temperature paint makes.

[Roger B]

    

[RayW]

Now re-assembled in air cooled format and definitely looking better than with the old copper water jacket.

[Alyn Foundry]

Blimey Ray….

That’s looking great.   

Merry Christmas.

[RayW]

Thanks Graham.
Happy Christmas to you and to all other members and here's hoping for a happy and healthy New Year.

[RayW]

Finally got the engine to run really well, to the point that it would even start by hand, rather than having to use the electric drill to spin it over. All the settings, ie gas pressure, needle valve setting and ignition timing are super critical at the moment, so some more fine tuning is required, but at least it starts and keeps going now!
I have found that the air valve on top of the cylinder needs to hang slightly open normally, being  closed by pressure in the cylinder on the compression stroke.

<a href="https://www.youtube.com/watch?v=fbL2bfyWV90" target="_blank">http://www.youtube.com/watch?v=fbL2bfyWV90</a>

[Jasonb]

It's quite lively now you have it running well.

[Roger B]

Excellent     

[Admiral_dk]

It is really taking off - so even if you are not totally happy about it yet - I will say that this is a major milestone you have passed with it 

Per

[Alyn Foundry]

She’s running a treat Ray.

Now you’ve found the “ sweet spot “ perhaps it’s time to try the hot tube again?

Cheers Graham.

[RayW]

Had it running most of the morning today. Lost a bit of compression when it blew the gasket between the two halves of the valve chest but still ran. I did make up an adaptor and fitted the hot tube that came with the engine, but couldn't even get the tube hot. I have a stainless tube that I made that screws in place of the spark plug, so might try that.

[Admiral_dk]

I do not have much experience running small scale IC engines in this regard - but I can tell you that on full size ones you can often destroy the gasket surface quickly, if you run it for a while with a broken gasket ....
But I guess that pressure and temperature has a lot to do with it - so a coasting engine, might not do any damage 

Do you think it was the gasket material, surfaces or the pressure holding them together that was the reason ...?

Per

[RayW]

Hello Per,
The two mating surfaces are machined and grooved so should seal OK with a good gasket. The one I used originally was a bit too thin.
I replaced the thin gasket with some silicone gasket sealant, which held for a while, but I was too impatient and ran the engine before the sealant had had time to cure properly. I will try that again, but if that fails, I will replace with a thicker gasket.

[RayW]

Had an unsuccessful try with the hot tube this morning, but couldn't get the engine to fire. Had a couple of minor gas leaks around the inlet air inlet valve on top of the cylinder, and around the gas inlet valve stem, both of which ignited. Reverted to spark ignition and had a very successful mornings running until the gasket between the two halves of the valve chest blew (again!!).
Up to that point compression was really good with strong bounce back and good steady running.

The valve chest effectively forms part of the combustion chamber and gets very hot, as shown by the discolouration in the attached photo. The gasket I had fitted this time was thicker than the previous one, and fitted with a smear of silicone gasket sealant on either side.The two halves of the valve chest are held together with three small round headed screws (similar in size to 4BA).

Due to the proximity of the screw holes to the outside edge, there are several places where a fibre or paper gasket will inevitably be weak. I am wondering whether a thin annealed copper gasket would solve the problem.


 

[Admiral_dk]

The three holes kind of ruins the idea of how the groove should keep it 'tight' .... but I wonder if a lapping of the surfaces will help / be necessary - if you either drop the gasket or use a metal one (here aluminium or copper comes to mind) ....

If you try a metal one, it must be thin and soft (heat treated copper - I'm not sure about how to make the aluminium one).

I'm sure that you're right about the heat + pressure destroys normal gasket material.

Best wishes

Per