1 Steam Cars : Phorum
General Steam Car topics
Fuel jet size test
Posted by: Kobus van Jaarsveld (IP Logged)
Date: January 02, 2005 04:22PM
<HTML>I had to make a new vapouriser for the EX, the one with the three pipes brazed together and coming from the back straight through the burner to the jets and venturis in front. The old jets I had for the main fire were drilled with a 0.90 mm drill (roughly #65 drill) and seemed to work well. I then learnt that Stanley recommended the use of a #62 drill, ie 0.97 mm for the jets on 10hp cars using kerosene. My car uses gasoline only but I was curious to know how larger jets would work.
So I made two jets with 0.95 mm dia openings because I could not get 0.97mm dia drills. The car ran well on these, I could not really detect any difference between these and the 0,90 mm jets. The next step was to go bigger still, and I made two jets which I drilled to 1.0mm dia., this being only 0.03 mm bigger than the prescribed size, I thought these would be just the thing.
After installing them I opened the door on top of the boiler, lit the pilot and when all was warm enough opened the fuel valve to the main fire. I watched with satisfaction how initially two nice thick white jets of partly vapourised fuel were entering the venturis and became invisible, as it should, once the fire had heated up the vapouriser.
I then sat on the front seat and proceeded to operate the hand pump to maintain the fuel pressure and noted that the rate of pressure decline was faster than with the smaller jets. I also noted that there was no burner "howl" and altogether all was quieter than what I was accustomed to. Soon steam started to come out the open steam chest valve and I was happy to see the steam pressure rising towards 100 psi.
My motor home where the Stanleys and other cars are kept is a long internally open building without ceilings. We have open wooden rafters supporting a tile roof. While bissfully observing the rise in steam pressure and keeping an eye on the fuel pressure, there was a sudden almighty thunderous woosh whup sound and when I looked up I saw huge swirling red flames and black smoke reaching up all the way from the boiler into the rafters above. Instinctively I shut off both fuel valves, jumped out and grabbed the nearest fire extinguisher which was in the car's toolbox. I looked in total disbelief at how the huge flames spewed out of the smokebox and billowed from the open hood above into the rafters.
By the time I had drawn the locking pin from the fire extinguisher, the flames subsided and died in a matter of seconds. The Stanley stood there, serene asif nothing had happened, only the singed paint on the front of the hood and blackened rafters were reminders of what had just transpired.
On reflection it is clear how this scary event was born. The fuel/air mix was overly rich resulting in incomplete combustion in the burner. Unburnt fuel went up the fire tubes and accumulated in the smoke box and above the opening and this lot ignited.
Do I now know how to diagnose jets that are too big? You bet! The next thing on the path to knowledge is to find out what happens when the jets are too small...... Kobus</HTML>
So I made two jets with 0.95 mm dia openings because I could not get 0.97mm dia drills. The car ran well on these, I could not really detect any difference between these and the 0,90 mm jets. The next step was to go bigger still, and I made two jets which I drilled to 1.0mm dia., this being only 0.03 mm bigger than the prescribed size, I thought these would be just the thing.
After installing them I opened the door on top of the boiler, lit the pilot and when all was warm enough opened the fuel valve to the main fire. I watched with satisfaction how initially two nice thick white jets of partly vapourised fuel were entering the venturis and became invisible, as it should, once the fire had heated up the vapouriser.
I then sat on the front seat and proceeded to operate the hand pump to maintain the fuel pressure and noted that the rate of pressure decline was faster than with the smaller jets. I also noted that there was no burner "howl" and altogether all was quieter than what I was accustomed to. Soon steam started to come out the open steam chest valve and I was happy to see the steam pressure rising towards 100 psi.
My motor home where the Stanleys and other cars are kept is a long internally open building without ceilings. We have open wooden rafters supporting a tile roof. While bissfully observing the rise in steam pressure and keeping an eye on the fuel pressure, there was a sudden almighty thunderous woosh whup sound and when I looked up I saw huge swirling red flames and black smoke reaching up all the way from the boiler into the rafters above. Instinctively I shut off both fuel valves, jumped out and grabbed the nearest fire extinguisher which was in the car's toolbox. I looked in total disbelief at how the huge flames spewed out of the smokebox and billowed from the open hood above into the rafters.
By the time I had drawn the locking pin from the fire extinguisher, the flames subsided and died in a matter of seconds. The Stanley stood there, serene asif nothing had happened, only the singed paint on the front of the hood and blackened rafters were reminders of what had just transpired.
On reflection it is clear how this scary event was born. The fuel/air mix was overly rich resulting in incomplete combustion in the burner. Unburnt fuel went up the fire tubes and accumulated in the smoke box and above the opening and this lot ignited.
Do I now know how to diagnose jets that are too big? You bet! The next thing on the path to knowledge is to find out what happens when the jets are too small...... Kobus</HTML>
Re: Fuel jet size test
Posted by: SSsssteamer (IP Logged)
Date: January 03, 2005 01:07AM
<HTML>Kobus, As you discovered, you went too large on your last jet size. The howl is also a good indicator on how well that burner is firing. The loudest howl you can make is your hottest fire that you can make. If you can't stand the howl, then start dropping your jet sizes until you find your comfort level. Dropping fuel pressure will about accomplish the same thing. Tourig at higher elevations, like around 8,000 feet above sea level, one will find that his sea level jetting is much too big for his fuel needs. If you are burning kerosene, you can thin it with gasoline to run leaner. Or you can drop a jet size to keep from floodng your burner. Touring at higher elevations without addressing your fuel problems can be dangerous. Unburnt fuel can accumlate in your exhaust stack on noncondensing car and it will eventually catch on fire. The captured fuel source in the exhaust stack is very hard to put out with out a steam enema. I watched a model R climbing a mountain on a tour one year loose his exhaust stack one piece at a time. He had his exhaust stack assembled by soldering. As the exhaust stack fire burned away, it unsoldered one piece at a time, starting at the rear of the stack. He left a trail of parts. When I bought my 606 Stanley, a fuel line to my fuel pressure gauge had been overlapped and soldered together. I had a flare fitting get loose and it started a small flame under the soldered joint. When the soldered joint parted with 140 psi in it, I had flames 20 feet in the air. I was lucky I knew where the valve was to dump the fuel pressure in the system. Where there is heat invloved, I do not solder anything that I want to stay together.</HTML>
Re: Fuel jet size test
Posted by: Kobus van Jaarsveld (IP Logged)
Date: January 05, 2005 05:32PM
<HTML>Pat, Many rthanks for this information. I keep on learning.
Best regards, Kobus</HTML>
Best regards, Kobus</HTML>
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