Review - Heim Joint's "Tennis Racket Effect" mod for helis

[kdsguy1]

i am very interested in getting theses on both my 550e, and 450 pro v2!!!, please pm me or send me a link on both the 550e i have the new desighn tail v2 silver

[FDflier]

Are they available for Raptor 50 Titan?

Jeff

[neverland]

sorry to butt in, but i don't understand the logic of why making the grips heavier would make it easier for the slider to move under load. as the weight is the same each side, wouldn't any positive or negative effect be exactly counteracted? i've searched around the net but can't find any theory. and why is it called 'the tennis racquet effect'? its puzzled me for a while.

[Helico-pteron]

Originally Posted by neverland

sorry to butt in, but i don't understand the logic of why making the grips heavier would make it easier for the slider to move under load. as the weight is the same each side, wouldn't any positive or negative effect be exactly counteracted? i've searched around the net but can't find any theory. and why is it called 'the tennis racquet effect'? its puzzled me for a while.

As you can see by the age of the thread that it never caught on. It's just something that doesn't exist in reality. It's like the magnetic bracelet for rc helicopters.

[neverland]

well i did the mod on my 450 anyway, but couldnt tell any difference tbh. saying that, its not any worse!

[neverland]

i had a 'lightbulb' moment. the weights are to counteract the control arm sticking out from the blade holder, which, due to centrifugal force, 'prefers' to be in line with the blade holder when the blades are spinning, so forcing the tail slider into the '0' degree position where it likes to stay. if the projecting 'chinese weights' are the same weight as the control arm, and at 90 degrees to it, the forces should be balanced out. ie the position of the blade axis wont be forced into any particular position. with the result that the tail slider should move along the shaft with little resistance. dead simple when you think about it

[SysCrusher]

Originally Posted by neverland

i had a 'lightbulb' moment. the weights are to counteract the control arm sticking out from the blade holder, which, due to centrifugal force, 'prefers' to be in line with the blade holder when the blades are spinning, so forcing the tail slider into the '0' degree position where it likes to stay. if the projecting 'chinese weights' are the same weight as the control arm, and at 90 degrees to it, the forces should be balanced out. ie the position of the blade axis wont be forced into any particular position. with the result that the tail slider should move along the shaft with little resistance. dead simple when you think about it

I think you pretty much nailed it with one exception. Even with the counter weights on ether side, it still will not counter the force of that control arm wanting to in center very well since the weight still will be mostly on one side. What would be better, is if we could add equal weight directly opposite of that control arm. Short of having custom grips molded like that, it's not easy DIY task. I have resorted to flipping my grips so that those control arms are in line with the centrifugal forces. Trailing edge instead of leading edge. Seems the tail is well behaved that way for me.

[HEIM JOINT]

I posted a graphical explanation here in post #1 https://www.helifreak.com/showthread.php?t=516097
The weights do not have to be equal on both sides, just the sum of the torques they produce needs to equal and opposite to the tennis raquet torque of the original tail system.

[SysCrusher]

Originally Posted by HEIM JOINT

I posted a graphical explanation here in post #1 https://www.helifreak.com/showthread.php?t=516097
The weights do not have to be equal on both sides, just the sum of the torques they produce needs to equal and opposite to the tennis raquet torque of the original tail system.

Thanks, I totally forgot about the blades.


Ok, now that I got a chance to sit down and read it thoroughly, it makes sense now.

[RotorFloater]

Originally Posted by Helico-pteron

As you can see by the age of the thread that it never caught on. It's just something that doesn't exist in reality. It's like the magnetic bracelet for rc helicopters.

This is adapted from real helicopters...sooo, its not a "magic bracelet" really... just saying.

[RotorFloater]

Make these for a Goblin 700? I got some from you a year or more ago for my old, now long gone trex 450 and 600's in the past.

[HEIM JOINT]

Originally Posted by Helico-pteron

As you can see by the age of the thread that it never caught on. It's just something that doesn't exist in reality. It's like the magnetic bracelet for rc helicopters.

I would advise not saying that out loud amongst knowledgeable helicopter people, you will be demonstrating your ignorance. My videos on this prove the affect of the weights and many experts on this forum have proven the effect also. Full scale helis also use them so this is not snake oil. If you care to understand the physics that cause it you can look at my pdf here post #1 https://www.helifreak.com/showthread.php?t=516097

HJ

[StatiC]

It would be neat if the tail holder arms were designed so that if the tail control become detached in some way (ball, arm, etc) the blades would naturally (tennis racket effect) go to a near 3 or 4 degree pitch so that the heli would not piro very fast which would make it easier to control instead of going to zero degree pitch which is where most would go.

[HEIM JOINT]

That could be done but the pushrod force would have to be substantial again to do it.

[StatiC]

At least the tennis racket effect could be listed as a feature by the designers then .