# Vapor Carburetor



## Rustkolector (Sep 13, 2009)

Has anyone built and used a vapor (bubble) carburetor based on Jan Ridders designs? If so, can you briefly relate your experience and any operating issues you observed?
Jeff


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## nemt (Sep 14, 2009)

Hy Jeff,

I myself have not build that vapouriser yet, but several of my Dutch modell builder colleges have. Very satisfying. Only after a some time, when the petrol goes out, the lighter parts of the petrol seem to be gone, so the mixtyre becomes unusable. You have to refresh the tankfilling. 

Nemt.


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## Debian (Sep 14, 2009)

Hi Jeff,
I could be wrong, but I'd take a look here:

http://www.homemodelenginemachinist.com/index.php?topic=4922.105

Looks like Cedge used a vapour carburetor for His marvellous "Victorian" IC engine.
Hope this helps.

Paolo


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## putputman (Sep 14, 2009)

Jeff, I built Jan's carb some time ago. I mounted it on my Red Wing engine and it functioned well. The only negative I found was as the fuel level changed it had some effect on the carb adjustment. 

Jan's first design was extremely simple and worked fine. I then built his new version that was supposed to have better speed control. I didn't have much luck with the new version. I must have done something wrong and after awhile, just gave up on it. 

I would be interested in hearing how it works out for you if you build it.

Here is a video of it on the Red Wing.


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## Rustkolector (Sep 14, 2009)

Putputman,
I have built the latest version of Jan's vapor carb using the two disks. It works, but not well on my "particular" engine. I have a slow speed throttle governed engine. It starts exceptionally easy on a lean mixture setting, and runs nicely, but at about twice its design RPM. I cannot slow it down with the vapor carb throttle without the engine running roughly. It just won't run smoothly at the richer setting like Jan's engines do. I contacted Jan and he says he has experienced the same results, but since his engines are higher speed, they work fine. His pressure controlled 2 stroke, however, seems to be the exception and runs down to 300 RPM. I have had two different thoughts on correcting the problem. First, add a second rotary barrel throttle in-line to throttle the mixture volume after adjusting it to the best running mixture using the vapor carb throttle. Second thought is to add a throttling screw on the excess air intake on the vapor carb throttle. That way I can use Jan's 3 way rotary valve to set the vapor flow, and the air valve to adjust for a better air/fuel ratio. I will probably do the latter first. But to do that, I have to remake the throttle valve into the earlier one like you used. The disk version doesn't lend itself to neatly adding an air throttle valve. Any thoughts would be greatly appreciated.


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## Cedge (Sep 14, 2009)

I've seen 3 of the engines owned by local builders running on the Vapor system, one of which was a 9 cylinder radial engine. They seem to just work fine and all 3 users say they are quite simple and pretty dependable to use. The only downside I've heard from them was cold weather negatively effecting the vaporization.

I briefly experimented with the Vapor Tank but my little engine is so darned fickle and my deadline so closing so rapidly that I went back to the aspiration set up. I intend to revisit the Vapor Tank and in fact adapted the fuel tank on the Victorian so that I can make the switch over with little additional work.

Steve


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## putputman (Sep 14, 2009)

Jeff, how about building Jan's first version of the carb. It is very simple and fast to build. See if your engine run better with that one.

I had very similar problems with his second version. He may be right when he says they work better on higher speed engines. Mine are all low speed.


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## Rustkolector (Sep 14, 2009)

Thanks, I will look around for info on Jan's first version. I am not familiar with it. 
Jeff


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## EMARCH55 (Sep 11, 2012)

built one with copper pipe worked well on both my model rngnes


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## Brian Rupnow (Sep 11, 2012)

I just built one three weeks ago for my Atkinson engine to Jans new design, but I haven't got the engine running yet.


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## EMARCH55 (Sep 12, 2012)

I ran the intake pipe right to the bottom of the tank  unlike Jans that only went to the surtace of the fuel.


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## cfellows (Sep 12, 2012)

EMARCH55 said:


> I ran the intake pipe right to the bottom of the tank  unlike Jans that only went to the surtace of the fuel.


 
The problem with that is that you may get a facefull of fuel if the check valve fails and compression or power blows back through the fuel tank.  From a performance standpoint, it doesn't make any difference whether the pipe goes below the surface or above...

Chuck


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## AussieJimG (Sep 13, 2012)

I used on on my Bonzer Hit & Miss engine and it worked fine for quite a while and then stopped working for reasons that I don't understand. I had to build a venturi carb for it in the end.

I also used it on my version of Jan's Debbie 2 stroke. It worked but I made a few changes that might have been detrimental. The carb is very sensitive to fuel level and requires constant adjustment to keep the engine running. Clearly it needs more work.

I used Shellite (Coleman fuel) to avoid the problems of vaporising the highly volatile fractions of petrol (gasoline) leaving the waxy gunk behind.

I like the concept of the vapour carb and have also played with Chuck Fellow's Pimento Jar version.

Jim


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## Brian Rupnow (Sep 13, 2012)

How many of you guys have been concerned that a backfire on attempted start up may shoot a tongue of flame back the intake pipe into the vapour tank and causing a fiery explosion? Jan Ridders seems very concerned about it and supplys the plans for a ball check valve free with his vapour tank plans. This scared me enough that I built the ball check valve, but I don't know how realistic it is that could happen.---Brian


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## cfellows (Sep 13, 2012)

Brian Rupnow said:


> How many of you guys have been concerned that a backfire on attempted start up may shoot a tongue of flame back the intake pipe into the vapour tank and causing a fiery explosion? Jan Ridders seems very concerned about it and supplys the plans for a ball check valve free with his vapour tank plans. This scared me enough that I built the ball check valve, but I don't know how realistic it is that could happen.---Brian



I don't have a check valve on any of mine.  I just depend on the spring loaded intake valve to hold it.  I have had a failure on one or two occasions, but it didn't explode or catch fire, it just blew a little fuel out of the intake pipe on the fuel tank.  It would have blown a lot more fuel out if I had had the intake pipe submersed in the fuel.

It seems to me, and this is just my opinion, if you are going to have a leak around the intake valve, it will occur during the compression stroke, not the power stroke.  In a normal 4 stroke engine, a backfire occurs while the intake valve is being held open by the camshaft.  In an atmospheric or vacuum operated valve, I don't believe a backfire, as such, is likely to happen.

*On the other hand, if you are using a vapor carburetor with a cam operated intake valve, I would definitely use a check valve for added safety!*

Chuck


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## AussieJimG (Sep 13, 2012)

I don't have a check valve on the four stroke Bonzer, I just rely on the automatic intake valve. But I have noticed small spurts like a submerged whale which (I think) occur while the intake valve is closing but not quite sealed. I have not been able to determine whether or not this back and forth motion of the vapour in the intake system causes any of the problems I have had with the engine.

It is difficult to investigate because a ball check valve would have inertia similar to that of the intake valve and thus would not stop the back flow.

Of course, all of his is happening at the beginning of the compression stroke and is not really relevant to the subject of backfiring.

As a further observation on the use of vapour carburettors, I have tried putting a tube into the intake of the fuel tank and varying the depth of the end of the tube in relation to the surface of the fuel - from way above to fully submerged. And, as Chuck says, it makes no difference. So I still don't know why the fuel level has an effect on engine performance.

Jim


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## cfellows (Sep 13, 2012)

AussieJimG said:


> I don't have a check valve on the four stroke Bonzer, I just rely on the automatic intake valve. But I have noticed small spurts like a submerged whale which (I think) occur while the intake valve is closing but not quite sealed. I have not been able to determine whether or not this back and forth motion of the vapour in the intake system causes any of the problems I have had with the engine.
> 
> It is difficult to investigate because a ball check valve would have inertia similar to that of the intake valve and thus would not stop the back flow.
> 
> ...


 
I've thought about this in the past and I think the reason the fuel level affects the way it runs is because of the surface area.  Most of the fuel tanks are cylindrical, so as the level of the fuel drops, the surface area of the fuel also decreases.  I expect if the tank was square or rectangular, the level of the fuel wouldn't make any difference.

Chuck


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## EMARCH55 (Sep 14, 2012)

Maybe a small brass screen in intake pipe would stop explosions.



Earl


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## AussieJimG (Sep 14, 2012)

Interesting thought Chuck, and of course this would not be the case with your Pimento jar because the axis of the cylinder is vertical so the surface area is constant. Am I right in assuming that the Pimento jar is not sensitive to fuel level?

Earl - what a brilliant suggestion. And bloody obvious when you think about it. 

Jim


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## lee9966 (Sep 17, 2012)

I have built and used a couple of these.  My feeling is the same as one of the earlier posters, the lighter parts of the fuel come out first.  After awhile, well before using all the fue, in the tank, it stops running no matter how the mix is adjusted.  Just empty the tank and refill and all is well again.

On one larger engine the evaporation would cool the tank until it was very cold and that effected operation also.  Letting the tank, and thereby the fuel, warm up again would let the engine start and run.

I usually use a vapor carb when an engine is finished to see if it will run.  For that it seems less finicky than tying to get compression, valve timing and ignition issues sorted out at the same time as wondering if your carb is anything like correct.

Lee


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## AussieJimG (Sep 18, 2012)

Hi Lee,

I switched to Shellite (Coleman fuel) to avoid the problem with the volatile fractions in petrol (gasoline). The same thing happens with my old motorcycles - the fuel tank sits over the engine which is still hot when I stop. This evaporates the volatile fractions and makes it hard to start next time.

Yes, I noticed the cooling of the tank as well and it does make a bit of difference. Holding in your hand helps until your hand gets cold. Then comes the hot air gun.

Like you, I use it first up because it is simple and usually works enough to check the rest of the engine. A whiff of  propane is also useful, as is Aerostart (marketed in Oz as "Start Ya Bastard"

Jim


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## feuered (Sep 20, 2012)

Built 3 versions, using Coleman fuel. First worked well, second had rotary valve, and was difficult to find good settings, third (latest?)has external air screw adjust and works fine on all three of my engines.


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