vapour carburetor

[william cubbonParticipant @williamcubbon74452]

safety

[william cubbonParticipant @williamcubbon74452]

What risk of flash back explosion might exist by adopting a glass jar petrol vapour carburetor? The engine in question is 1 inch bore, 4 stroke, with Hall effect ignition operated at crank speed. Petrol vapor will be drawn to the air inlet of a Nemett designed barrel throttle carb through a clear plastic tube. Of concern is possible leaky valves, valve overlap period, valve timing events in general, and also the extra spark in the valve overlap period. Thanks in advance for any comments. Patrick Cubbon

[Brian Sweeting 2Participant @briansweeting2]

Have you seen the carbs made by Jan Ridders? They are glass cylinders or glass end plates.

**LINK**

http://ridders.nu/Webpaginas/pagina_1-cilinder_glas_4takt/1cil_glas_frameset.htm

[JasonBModerator @jasonb]

I've run a couple of my engines on quickly knocked up vapour carbs when I was having flooding problems did not even think of blowback. Seen plenty of other engines running with them and all seem OK. The propane ones are more likely to singe your eyebrows!

[william cubbonParticipant @williamcubbon74452]

Thanks to Brian Sweeting and JasonB who suggest experience with this form of carburation presents little risk. The problem engine was given part finished as a challenge to complete. Numerous adjustments to the carb and ignition timing failed. However, the plug needs deepening to ensure the spark is within the chamber, then, combined with petrol vapour success may be the prize? If not it is back under the bench! Thanks for the mention of Jan Ridders and his web link.. Patrick Cubbon

[MichaelRParticipant @michaelr]

I have run a Hit and Miss (RLE) engine on a vapour carb and like Jason never gave blowback a thought, the engine ran OK with the setup, a air bleed in the intake line helps with the running. Mike.

[Neil WyattModerator @neilwyatt]

If really concerned, a short section of fairly large diameter pipe stuffed loosely with wire ought to serve as a flash arrestor, it would both cool and slow a flame front.

There should be no real problem as a surface carb is not a pressure vessel and has a pretty much unrestricted airflow through it so I imagine the worst case would be a loud >pop<

Neil

[pgk pgkParticipant @pgkpgk17461]

I supose potential is there if the fluid level gets really low. Back in my RC Heli flying days we carried ot an experiment with a used up 4L 30% nitromethane fuel bottle… obvious dregs tipped out, sat bottle on ground and applied a lit match on the end of a pole – instant huge flame out of the neck of thing 2-3 feet long. Self evidently more dramatic due to the nitro.

pgk

[Neil WyattModerator @neilwyatt]

Posted by pgk pgk on 15/08/2018 19:17:54:

I supose potential is there if the fluid level gets really low. Back in my RC Heli flying days we carried ot an experiment with a used up 4L 30% nitromethane fuel bottle… obvious dregs tipped out, sat bottle on ground and applied a lit match on the end of a pole – instant huge flame out of the neck of thing 2-3 feet long. Self evidently more dramatic due to the nitro.

Puny!

As a teenager I fitted a meccano gear wheel to the end of a butane canister and improvised a flame thrower capable of 10-foot flames. Probably was NOT a good idea to ry bit out in the kitchen…

In these days of paranoia I won't detail my other teenage misdeeds, but there were some big bangs

Neil

[pgk pgkParticipant @pgkpgk17461]

Posted by Neil Wyatt on 15/08/2018 22:18:53:

Posted by pgk pgk on 15/08/2018 19:17:54:

I supose potential is there if the fluid level gets really low. Back in my RC Heli flying days we carried ot an experiment with a used up 4L 30% nitromethane fuel bottle… obvious dregs tipped out, sat bottle on ground and applied a lit match on the end of a pole – instant huge flame out of the neck of thing 2-3 feet long. Self evidently more dramatic due to the nitro.

Puny!

As a teenager I fitted a meccano gear wheel to the end of a butane canister and improvised a flame thrower capable of 10-foot flames. Probably was NOT a good idea to ry bit out in the kitchen…

In these days of paranoia I won't detail my other teenage misdeeds, but there were some big bangs

Neil

I knew some large girls too…

pgk

[Howard LewisParticipant @howardlewis46836]

Presumably, the concern is that in the event of a"backfire" there would be an explosion closely followed by flying glass particles.

(In a former life, I exposed a glass filter/agglomerator bowl, used for 5 -10 psi, to 60 -70 psi as an air bell to reduce fuel pressure fluctuations, and lived to tell the tale! )

Does the chamber have to be glass, other than to view the level? Metal would be stronger, and less likely to become shrapnel.

Neil's suggestion of steel wool as a flashback arrester is a good one, also it might serve to revapourise any fuel that condenses en route to the engine. Possibly just a little copper gauze would suffice for both functions?

Howard

[william cubbonParticipant @williamcubbon74452]

MichaelR – air bleed in the intake – a sensible idea

Neil Wyatt – wire mesh as a flash arrestor, a good suggestion thanks, reminder not a pressure vessel. Flame thrower! I am older than you, in the 50's gunpowder ingredients could be purchased from the chemist – my friend was able to fire ball bearings from a small brass canon, me – lit some powder in the fireplace (Father not aware).

PGK – 2 to 3ft flame out thanks for the warning.

Hi Howard – Yes, I have a copper tank that could be used though I like to see what is going on with petrol levels. Wished to add a picture of the problem engine for general inteterest but did not succeed. I see MichaelR managed with his photo.

[JasonBModerator @jasonb]

I've just plumbed an RC "klunk" tank the opposite way round when needed but a nice little jam jar does look mor ethe part for display.

Have a look at this for how to add a photo of your engine

[Neil WyattModerator @neilwyatt]

Posted by william cubbon on 16/08/2018 17:09:43:

could be purchased from the chemist

And in the 70s, along with other useful products.

Neil

[MichaelRParticipant @michaelr]

 

My RLE Running on Vapour. Mike. https://youtu.be/bNx0TpJKulk

Edited By JasonB on 16/08/2018 19:25:44

[MichaelRParticipant @michaelr]

Hi Jason, Many thanks for sorting my video out, much appreciated. Mike.

[David Standing 1Participant @davidstanding1]

Posted by william cubbon on 16/08/2018 17:09:43:

my friend was able to fire ball bearings from a small brass canon

That's a poor way to treat a cleric

[william cubbonParticipant @williamcubbon74452]

Problem engine, thanks JasonB for photo guide input, quite a bit of time for the result to appear.

David standing – canon/cannon that really provoked more than a smile a real laugh!

Will be pressing on with a vapour bottle, the photo shows petrol supply to a Nemett carb. on the other side.

Patrick Cubbon.

[Tim StevensParticipant @timstevens64731]

It might help some readers to know that a vapour carburettor is also known (historically) as a surface carburettor. As distinct, in pre WW1 days, from a spray carburettor. Several early cars had them, including Lanchester, and a few motorcycles. But the latter have not survived well as a minor spill usually meant a major fire. Especially if the ignition was by hot tube.

Cheers, Tim

[Michael GilliganParticipant @michaelgilligan61133]

That sure does 'cut the mustard'

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Being a surface carburretor, how about following the prototype ones and drawing the petrol vapour from above a felt pad that was moistened by the petrol?

Also lessens the risk of mixture variations caused by vibration disturbing the actual surface of the fuel.

Howard

[william cubbonParticipant @williamcubbon74452]

Hi Howard, Felt pad above petrol – thanks for a good suggestion. First rushed attempt with surface carb was not a success. Vibration resulted in a haze of petrol droplets from the exhaust. Blutac, to secure plastic pipe into tapered mouth of emett carb, does not take kindly to petrol! Next step is to be more professional with a remote petrol container and plastic feed pipe directly into inlet port via a proper adaptor. Still to be done is to position the spark plug gap within the combustion space. The engine has a reprieve from under the bench for now!!

[Howard LewisParticipant @howardlewis46836]

Modern petrol, with ethanol (or is it methanol?) added seems to dissolve things that the leaded petrol from "the bad old days" did not touch.

Looks like you have hours of fun ahead of you, Jim, optimising the carburettor and then the position of the spark plug. (within the combustion chamber, or merely the protrusion into it?)

A nice job for when nothing else outdoors is suitable.

Keep us posted!

Howard

[william cubbonParticipant @williamcubbon74452]

Just to close this forum thread. Re positioning spark plug made no difference. Engine remains a non runner. Problem is LEAKY inlet and exhaust valves with little compression. New valves, re-machined seats, and better cams needed. The challenge presented with this engine was to complete the build and then see if it was a runner. The engine moves to display only! Now it is a return to steam – a single cylinder version of Bertinat's Borderer ME 1989 issue 3862. A year has passed playing about with this engine and an enjoyable time spent in the workshop.

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