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Mythbusters Jet Pack
Simon - 1/1/06 at 12:53 AM

Anyone watch this - I've seen it twice and think they could've tried harder.

Anyone know how to calculate the amount of air moved to provide thrust/lift - I understand the principle of prop pitch, but want to know volumes etc. May make a model of the Solotrek.

ATB

Simon


steve_gus - 1/1/06 at 01:07 AM

Havnt seen the program - was it air only, or combustion like a rocket motor?

I have seen a movie called October Sky (and read the book called Rocket boys). Its about a bunch of kids in the late fifties (one of whom goes on to work for NASA) and their exploits in making rockets.

There are some complex calculations in determining rocket thrust. (Guess thats why rocket science is held up to be dififcult ) The shape and geomety of the nozzle from the engine is VITAL to get the maximum thrust from the motor....... dunno if this is the same for compressed or blown air.

atb

steve

[Edited on 1/1/06 by steve_gus]


Simon - 1/1/06 at 01:24 AM

Steve,

It's air - two fans above head, left and right, powered by petrol engine (central prop and belt drive to fans)

Like this:

http://www.solotrek.com/devhistory.html

just on a smaller budget - they had $2000 and bought plans off the internet

"Build Yourself a Deathtrap for as alittle as etc etc etc"

ATB

Simon


JoelP - 1/1/06 at 02:05 AM

i saw the 3000bhp rocket car experiment, which was fun


paulf - 1/1/06 at 12:00 PM

I saw that and was also a bit dissapointed with how they did it.
The belt drive looked a bit slack and I suspect a lot of power was lost in it slipping, I would have used toothed belts if i was going to attempt it .
The engine must have made anple power if it was correctly transmitted.
Paul.


Simon - 1/1/06 at 07:50 PM

Paul, I think smooth belts are ok - I believe they are used in the Robinson R22. I suspect that they needed reduced gearing on the fans to speed them up, maybe even increase pitch/diameter.

ATB

Simon


paulf - 1/1/06 at 08:33 PM

I think your correct about the robinson helicopter but i remeber it as having a multiple belt set up and also a rigid framework to allow correct tensioning.There device was to flimsy to allow the belts to be kept under tension plus as you say the pulley dias were to small to allow them to transmit the power.It was a pity as i think it could really be possible to make a working unit , however my wife wont let me

quote:
Originally posted by Simon
Paul, I think smooth belts are ok - I believe they are used in the Robinson R22. I suspect that they needed reduced gearing on the fans to speed them up, maybe even increase pitch/diameter.

ATB

Simon
:


Cita - 1/1/06 at 11:57 PM

The Solotrek was a big joke!!!!
A lot of tax money wasted for a wrong concept.
To "calculate" thrust,you need to transport a mass of air greater than your take-off weigth every second.In other words if your craft fully loaded weighs 500 lbs than your rotor(s) must be able to transport 500 lbs of air every second,from above the rotordisc to below the rotordisc.
If you understand pitch of a rotor or wing than this is easy.
It's obvious that rotor RPM plays a major role in this.

Cheers Cita


Simon - 2/1/06 at 12:01 AM

Cita,

Solotrek funding was cancelled at the time the most progress was being made - ie right at the time of the first test flights. This was due to (private) investors setting immoveable time frames to certain progress goals that weren't met.

That was the "joke"

ATB

Simon


Cita - 2/1/06 at 12:09 AM

I think the concept was a joke to Simon
Every helicopter has a dead men's curve and that curve for the Solotrek was, to say the least not very attractive.
Being unable to autorotate, the parachute recovery system needs height to fully do it's job.
After spending what....a few million dollars,two feet in the air is not much for all the technology-time and money invested!
No wonder the private investors where a bit worried

Cheers Cita


Simon - 2/1/06 at 12:25 AM

Well Paul Moller has spent upwards of $200m and he's managed the same.

I suppose you're of the thinking that perhaps Henry Ford shouldn't have been lent a few hundred bucks so he could start a car production facility or Frank Whittle should have kept his dream in his head.

Simon


Cita - 2/1/06 at 10:36 AM

It's not because P. Moller has spend more than 200 million$ of other people's money on a never ending story that it justify the Solotrek concept.
If you compare Sir Frank Whittle's work with the Solotrek than it's obvious that you have no clue about the value of rotorcraft like the Solotrek!
The Solotrek cannot autorotate so either you fly it slowly very close to the ground,a few feet at the max,or fly it way up high so that the recovery system can bring you safely back to earth.
The question is what about the period when you try to reach that safe altitude and you have an engine failure?

I'm all in favour of supporting new idea's especially in the aircraft scenery Simon but some things are simply not worth the attention and the money inspite of the sometimes immaculate hype that's builded around some projects.
A long time ago I posted a picture of an Austrian guy who builded himself a small co-axial helicopter.He has been flying this thing many times at altitudes and speeds never achieved by the Solotrek yet, he spended less money than the Solotrek staff has spended on coffee!!!
If you see with what means this guy has builded his little flying machine than it makes me angry Simon that millions of (often) taxpayers money are spend on projects that are deemed to fail simply due to concept mistakes,which everyone can spot.
Believe me,the Solotrek is one of them and I'm sure that several people on this forum could build a similar craft like the Solotrek for far less money and probably outperform the Solotrek.


Cheers Cita