T rex 450 help

[james 1989]

Just rebuilt my 450 after a crash in which it had a new boom etc but when i spin it up all it wants to do is spin? Any pointers

Thanks
James

[Biffa]

If you have just replaced the boom and no electrics, chances are you have the belt twisted in the wrong direction.

[james 1989]

Thanks for the replys ill check all that. Electrics seem fine and no settings have been changed on tx. It could be tail servo linkage too long? Or belt twisted wrong way. How would those two things have any effect though( still new to this so pardon the silly questions)

Thanks
James

[Biffa]

The belts have a 90 degree twist to the left which rotates the tail the right way. Easy way to check is to look at the heli side on (tail to the left and nose right) and as you rotate the head the tail blades should turn anti clockwise up into the rotor down wash.

[cjcj1949]

I remember those days. Everything has to go back right. There are more ways to rebuild a heli than you realize when you are taking it apart. Most of them are worng. This is the way most people learn. Take some closeup photos when you have it all working. The belt twist is easy to get wrong and you can get too many twists in it as well. I've only just thought of a way to figure it out. If you look from above at the belt the drive pully nearest the head goes round anticlockwise. The pully at the tail end needs to go anticlock wise so the top of that pully must come from the center of the heli. Looking at the other pully the left hand side of that belt is moving towards the tail. So the belt at the tail must be twisted clockwise so that the left from the top goes over the top at the tail. I will edit this if its worng.

[james 1989]

Just had a quick look this morning and the tail is going clockwise side on so looks like i have got the belt twist wrong.

Thanks guys thats something new ive learned.

James

[james 1989]

sorted twisted the belt the oppposite way tail rotor s going right way now and spun it up and solid as a rock no spinning.
thanks

james

[Biffa]

sorted twisted the belt the oppposite way tail rotor s going right way now and spun it up and solid as a rock no spinning.
thanks

james

Good stuff.

It's a very easy mistake to make, I still have to check several times before I screw everything together.