Jet Luge Update

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larry cottrill
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Location: Mingo, Iowa USA

Re: re: Jet Luge Update

Post by larry cottrill » Mon Aug 14, 2006 3:24 pm

Lugebob wrote:The key to a street luge being stable and fast is the low mass and low and very centered center of gravity. Putting anything on the back starts to upset the formula, so the mass/ size of the power unit had to be small. This also includes the fuel source. I have had this idea for over 10 years, but there were no power sources available to meet the requirements until 2 years ago.
Everyone seems to want to mount pulsejets high and to the rear. Both are counterproductive, in most cases. The reason I suggested twin engines is that they can be mounted low and at the sides. As long as you get the tail end of the engines aft of averything else, the exhaust flame is no problem. Very thin aluminum sheet makes perfect heat shielding wherever needed.
I am running just over 50lbs of thrust on a 70 degree F day and my total weight is 205lbs to include the luge, fuel, me and my safetygear. The total weight of the power unit.(box in the back). turbine, starter system, fuel, tank,batteries, soleniods, computers, sensors and the mounting hardware are right at 6.8lbs
That is 50oz of fuel and it will give me 2minutes and 20 seconds at full throttle. I will never be on the throttle for 2 minutes... 30 seconds takes me to 100mph on flat roadway.
Well, that's impressive performance, in a couple of ways. You're getting an engine thrust-to-weight ratio of better than 8.0, and what's most amazing, your Thrust Specific Fuel Consumption is a mere 0.514 lb/lbF/hr, if I've worked it out correctly. The best value I've heard for any pulsejet so far has been around 0.9 or a little lower, and that's a VERY well-tuned pulsejet indeed. I have no doubt that an all-stainless valveless pulsejet could be built to a T/W ratio of something close to what you have, though. They are, after all, almost "pressureless" engines, and can be made of VERY thin material.
Another problem with pulsejet is the WOW and Scare factor..... I am already finding it hard to convince people to let me run this setup... even on a track with concrete jersey walls to protect the crowd.
This is where the pulsejet is actually better - there is absolutely NO chance for engine destruction, shrapnel, etc. And, it's the perfect crowd pleaser for an audience that accepts or desires loud noise, anyway. One important consideration is vibration, but that can be mostly taken up in the engine mountings.
If you make that thing I want to try it... we can trade rides for a day.
I'll let you know ... but my feeling right now is that I wouldn't get on anything like what you've got, with the engine running, if you held a gun to my head ;-)

L Cottrill

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