Jet???

ElJay

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Sep 12, 2004
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Big Spring, TX
EEEuuuuuuwweee!
Have a friend on the web that I've been emailing with lately, and haven't heard from him in a few days. I get an email from him today telling me he's just got back with a basket full of bensen. I'm thinking cool, picked some parts/partials or whatever...
Turns out he's got his self a (probably by the look of the pix) finished ready to go JET powered bensen!
No tail of course (suppose its "directed thrusters"?) and it just looks like it wants to scream!

I'll ask if its ok to link to his pictures to post here if anybody's interested....
just too cool!

LJ
 

CLS447

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Well...... let's see it!
 

GyroRon

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ALOT
Some of us already have seen it, when it was on Ebay a few weeks ago. It was pretty much accepted by everyone that the jet engine was not large enough to fly that machine. Also a rudder would still be needed.
 

C. Beaty

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T'aint a pulse jet, Al; it's a Gluharef (?) pressure jet. Craig Wall showed up at Bensen Days with one mounted on the rear of his clapped out Japanese pickup truck several years ago. Wouldn't propel the truck but would have made tailgaters keep their distance if he had ever decided to light it off while underway; especially at night.

Liquid propane is superheated by a heat exchanger (coiled up stainless tubing) mounted in the tailpipe. Allowed to expand through a nozzle, the high velocity propane vapor blows through a series of venturi sections and serves as a dynamic compressor. Steam jet ejectors probably date back to James Watt.

Dynamic compressors have a thermal efficiency of only a few percent and the possible compression ratio isn't very high. Gluharef apparently used resonances in the various venturi sections to improve efficiency somewhat.

These pressure jets are throttleable down to 20% or 30% or somewhere in that range.

I think the largest size had about 50 lb. of thrust. Probably had a BSFC of a couple of pounds of fuel per lb/thrust/hr.

Only the ignorant would attempt to propel tug boats with pure jet engines; a gas turbine running a water screw, maybe.
 

C. Beaty

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The gas turbine isn't all that difficult using automotive turbochargers; some Japanese turbos use ceramic turbines that will stand up to the high temperatures necessary.

The problem arises with gear reduction. How does one reduce turbine wheel speeds from ~200,0000 rpm to 2500 rpm propeller speeds?

The gears one can buy from Boston Gear or the like simply won't work.

Gear reduction requires very high precision gears (expensive!) and oil mist lubrication.

It could be done but the bean counters (accountants if you're not familiar with US slang) would look at return on investment possibilities and pull the plug.
 

Victor Duarte

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right, gears are the problem. did you see ROTREX superchargers ? 12000 max rpm at entry, 200000 inside, they have a good gear system working apprently only by the oil viscosity... check www.rotrex.com , 12000 are not impossible to lower to 2500
anyway there are a lot of APU, even "old" that could fit, i remember the helico "predator" had one, the cost is comparable to a 914 or a lyco , turbomeca also has small APU, i think the really problem is repair, costy, while piston engines can be maintained and quite repaired by any good amateur.
and thanks for teatching to me a little slang words ;) i promise to do some homework :D
regards
 
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Al_Hammer

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C. Beaty said:
T'aint a pulse jet, Al; it's a Gluharef (?) pressure jet.

Yes, Chuck, I see it now. Going back to the ebay listing, it says the jet produces 130 lbs of thrust.
This just happens to be the same thrust as this Gluhareff engine which can be built from plans: http://www.unitednuclear.com/jetplans.htm
Probably the same engine.
 
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