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Prop Design (designed in safety)


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All,

I was thinking......

Do you think that it would be worth a go at making a paramotor prop which is hinged at the hub so that (IF) it makes contact with something while spinning it folds back.

EG, The Walkera RC Helicoptors main rotor.

The Centrifugal force is used to keep the props open fully.

A couple of bearings.... and its job done as far as I can tell.

SW :D

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I like the idea but the prop spins so quickly and would have so much inertia at part to full throttle that I'm not sure how effective it would be.

If you got a body part in the prop disc it would still do massive damage.

Also if the prop hit the cage or another object then the inertia coupled with the fragility of the prop would probably still lead to the prop being destroyed.

Hope I'm wrong and if you've got time on your hands then it can't hurt to give it a go though!!??

Ian.

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Not what I was thinking at all to be honest...

Cant find a vid of the heli either....

so instead of folding (backwards to reduce drag) as per your vid...

The heli ones remain in axis but pivot on a bearing at the hub, so when they hit something the blades fold out of the way then as soon as the object has gone (lets say a shoulder for example) it opens back out due to the centrifugal force.

I will try and find a vid somewhere.

SW :D

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IRM...

The only force on any impact would be the weight of the prop it's self and any friction in the bearing at the hub (rather than 22HP spinning that same fixed weight)

You can put your hand in the way of an RC heli with this fitted ( I recon even a banana would survive it ) Its very surprising.

SW :D

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I Know what you mean Simon as I used to fly RC Helicopters, I often wonder why this type of prop set up hasn't been adapted to Paramotors.

Mmmmm maybe I should invent one and call it the X-Prop, shouldn't be that hard to do! :)

That would be X as in my name which you once got wrong (I never have forgotten) :D

Richard X

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I just thought you were leaving a kiss after your name each time you posted! :lol:

I have all of the required bits to make one. I am working on something a little more exciting than that at the moment though so I have to finish this project first.

SW :D

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Sorry Simon.... Hinged blades will make no difference to 500 gramme blades, the tips of which could be doing over 300 mph.

A better idea would be to mount a good strong frame, strung with netting or line that wont stretch or flex back into the prop. And set well infront of the prop so as to be well away from a finger tip IF you should be tempted to poke it through. An added bonus of this type of system, is many less broken props, as they are less likely ever to make contact with the cage

Dave

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Nope disagree...

A stimmer chord is 'designed to flex' out of the way and repeatedly strike the same place. Also, what heppens when you hit a solid enough object that it cant move out of the way fast enough... like a big stone for example.. It WILL snap.

I will tell you my thoughts....

If I took a lump of 4x2 and hit you on the head with it as hard as I could, you would likely go Ooch.

It I took the same bit of 4x2 with a bearing at the bottom and hit you on the head with it, I agree that you would still say Ooch but I fail to believe for a second that it would make NO difference.

SW :D

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Another one would be to mount the same bit of 4x2 into a vice and run into it has hard as you can...

Mount the same bit of wood on a bearing in a vice and run in to it as fast as you can...

Let me know how you get on :-)

And so on.

SW :D

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Or LOLOL

Try it with an RC heli, one without the pivoting point and one with.

I almost guarantee the non pivoting one will slice into your leg...

I have flewn my walkera into my leg, back, arm, and loads of other solid objects all that was left with little bruises.

SW :D

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Sorry Simon, I'm still more than sceptical about this one.

I can see the theory but a lot of the differences come down to mass, speed and therefore inertia.

I agree that if you walked into a bit of of 4x2 which was fixed into a vice at one end it would hurt more than if you walked into a bit of 4x2 which was loose at one end. But if you took either piece of 4x2 and span it so that it was rotating at 3000 rpm and the end was doing near to the speed of sound I imagine both would bloody hurt if you made contact with them!

The hindged blades on little electric helis weigh next to nothing and I'm sure that is the main reason why they don't hurt (or break!) when you stick your hand in the rotor disc.

Good luck trying though! Would be interested to hear about your other project.

Regards,

Ian.

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Ian

I have seen the damage those 'little electric helicopter' blades can do if it flies into you and it is not a pretty sight!

I agree that the physics dictate that the rotor blades on a '600' petrol helcoptor could be capable of very serious damage, even with hinged pivot points.

I certainly wouldn't stick my hands in the rotors!

Eddie

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I thought it was Banana......

The Idea that is......Ive got to side with the flat top on this one.....Ive got a strimmer with little plastic blades on 3 of them hinged from a small plastic disc

Should have seen what my girlfriends toe looked like last year after she went cutting the grass with her flip flops on....... (I have to use that dangerous machine now ) the grass is 2ft high this year.... :lol:

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