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Paramotors and "crumple zone"


ptwizz
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Apologies in advance for the rant; I was recently exposed to the online outpourings of an individual who I understand is notorious in the paramotoring community. As a result, I was prompted to do a little investigation into one of his more outrageous claims.

As most of us are probably aware, there is at least one paramotor sales person who makes great issue of their products alleged "crumple zone".

Working as an automotive design engineer, I have some insight into what is required of a crumple zone.

The purpose is to absorb impact energy in a manner which minimises peak forces experienced by the occupant.

This means a structure which will collapse with a force which varies as little as possible through the duration of the impact event. By manintaining an even force, the peak force values (those which cause injury) are reduced to a minimum for a given acceleration and displacement.

Tubular space frames do not exhibit this kind of collapse. Tubes fail in compression and bending by buckling. When a tube is loaded either in compression or bending, load can be increased until the tube reaches it's buckling point, at which the tube collapses very suddenly. This produces a very high peak force just before the collapse and very little energy absorbtion through most of the displacement.

A well designed crumple zone usually incorporates design elements which cause the material to fail in a series of bends. A crash beam for a passenger car will often have a series of notches pressed into it. Each notch will allow a partial collpse to initiate without the large force peak which is seen in buckling events. The design will also have to constrain the crash beam so that it is forced to collapse in the required manner and not simply bend away to one side or seperate from it's mountings.

It is possible to make a tubular crumple zone, but to do so requires a complex lattice of small tubes which is not practical for paramotor manufacture.

In short, I have yet to see a paramotor frame which has anything that might reasonably be referred to as a crumple zone.

Individual anecdotes along the lines of "paramotor crumple zone saved my life.." are without value. Unless one managed to crash while fully instrumented, an individual crash cannot be reliably repeated under test conditions.

Given that the mathematical evidence shows that tubular paramotor frames are not effective at absorbing energy in a crash, and that no data exists to back up individual claims, I suggest it is reasonable to conclude that the paramotor crumple zone is at best a myth and at worst an irresponsible lie intended to increase sales.

Unless anyone can tell me otherwise.

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You'd be amazed at some of the supposed professional individuals who propose similar concepts.

I recently saw a vehicle design which was claimed to dissipate frontal crash energy by the deformation of structure at the rear which supported powertrain mass. Of course, all this energy had to pass through the front structure (i.e. occupant space) first.

Unless the paramotor engine is mounted between the occupant and the point of impact or its' load path passes through the occupant (!), allowing it to move is of no benefit.

Am I the only one who feels the need to write a paramotor crash model now?

:explode:

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Hi del,

Could you explain how aluminium tubes can possibly form a crumple zone on a Paramotor ?

Cheers

Colin

Dear colin

Aluminum is actually the best material for a crumple zone as it crushes extremely well to absorb impact. The gas tank just moves up out of the way. Look at the picture on U-Turn USA and you can see a Flat Top that I stalled into the ground on a 19sm uncertified acro glider. I used the entire crumple zone and walked away without a scratch. The gas tank was completely unharmed as well which you can see clearly in the picture. The Flat Top saves lives. Tons of them. We all crash at some point if you fly long enough. Without that crumple zone I would be dead 10 times over.

- superdell

Enough of this nay-saying about crumple zones. Be gone with your technical babble. Dell says they are ok :-)

Sent from my iPhone using PMC Forum mobile app

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Oh man that is funny! Almost dropped my coffee.....

"Dear colin

Aluminum is actually the best material for a crumple zone as it crushes extremely well to absorb impact. The gas tank just moves up out of the way. Look at the picture on U-Turn USA and you can see a Flat Top that I stalled into the ground on a 19sm uncertified acro glider. I used the entire crumple zone and walked away without a scratch. The gas tank was completely unharmed as well which you can see clearly in the picture. The Flat Top saves lives. Tons of them. We all crash at some point if you fly long enough. Without that crumple zone I would be dead 10 times over. "

The best part is "The gas tank just moves up out of the way" magic.... PTwizz your trying to apply logic and math you crazy bastard. Its not needed "It just moves out of the way"

What do they say..... Ignorance is bliss? He lives in his own self made little planet where he is Albert.

Wow how is it people like this are allowed to roam free and multiply lol

cheers

T

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Hi ,you guys completely wrong understand ,dell must make mistake in writing -mean to be "creampie zone" not "crumple zone" ,but how this deviant doing this with aluminium pipes ,that is different story. :mrgreen::P

"We all crash at some point if you fly long enough. Without that creampie zone I would be dead 10 times over. " -this everything explain :D:D:D

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"We all crash at some point if you fly long enough. Without that crumple zone I would be dead 10 times over."

Only if we push beyond the limits of our skill and equipment.

During my conversation with Dell, I mentioned that I had been riding motorcycles for 30 years without incident and that I was capable of doing so despite the fact that I don't pull wheelies, powerslides etc.

Dell's response was that I clearly ride like a sissy and don't have control of my bike, and that he wouldn't let his daughter ride pillion on a bike that didn't have the tyre tread worn away to the sidewall. :shock:

I believe that most of us are happy to fly well within the limits of man and machine, fully intending to never crash.

Some like to explore the boundaries to advance their skills either for competition or personal satisfaction. That is fine so long as they are aware of the risk and plan accordingly.

Dell likes to push the boundaries of physics, law, and common sense with no regard to anyone else.

Some years ago, I saw a bumper sticker on a vehicle with US plates. The sticker read

"If you're not like me, I hate you"

I believe that describes the section of society which includes Dell.

P.S. Don't google "creampie zone" at work. :o

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I did read this article.

I have to admit the man fascinates me. It’s as if he has created his own alternative reality. In this reality things like:

1. Standard aluminum tubing crates a “crumple zone” when connected in anyway shape or form.

2. He is a good PPG teacher

3. Computer warranty issues can solved by pointing your 35 at them

At the same time it scares me that people like dell don’t need a license to reproduce. The government should be controlling this type of nuisance.

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