View Full Version : Tighten that head up

06-05-2006, 06:18 AM
I posted this some time back over on the dark side:

The issue is the aluminum upper mixing arms loosen up around one of the bearings and get wobbly. When this happens--and it will happen--the blade pitch changes quasi-randomly by as much as 1 degree. Such play makes for a sloppy flying heli.

To solve this problem, I realized I needed a way to compress the outside of the bearing tube. I further realized, the way to do that was to put a steel ring around the outside of the tube. The posting below shows how I did this and where I got the needed steel rings...

First, go to Tower Hobbies (or elsewhere) and order these (http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXLBM2): http://www.rohland.us/images/EEgor/hmxe7630.jpg

What you really need are the bearings on the end of those Collective Pitch Levers. Do not remove the bearings at this time. If you can find the right size bearings elsewhere, that might be cheaper.

With the bearing in hand, knock the inner race out but, be careful you don't break the outer race. That is why I suggested you leave the bearing in the Collective Pitch Levers since that will help protect the outer race when you destroy the bearing.

Now, break the Collective Pitch Levers with pliers to get to those precious outer races.

With your aluminum upper mixing arms handy: http://www.rohland.us/images/EEgor/hmxe8821.jpg
Press those outer races into the end of the mixing arm bearing tubes. See the 2 pictures below:

http://www.rohland.us/images/EEgor/2006-05-05_img_0001.jpg http://www.rohland.us/images/EEgor/2006-05-05_img_0002.jpg

With those bearing races squeezing the mixing arm bearing tube, press the bearing into the mixing arm. Put the mixing arms back onto the seesaw and go fly.

This mod will help keep the upper mixing arms from getting sloppy. That will greatly tighten up the X400 head.

I hope this mod helps you get a better flying hei. It did for me.

06-05-2006, 06:34 AM
Thanks! I think this is good to remember with all helicopter. I went though my Predator the other day after a "hard" auto and found some things had loosened up.

06-05-2006, 07:48 AM
thanks for that info. i am having that same exact problem with my 400.

07-11-2006, 02:18 AM
A varry thinline of locktite on the outside of the outer race (becarfull not to get it in the race and use a varry small amount) will help hold it in place on the alumis abd same with ca for plastic. But use varry little so it wont run out and get into the bearing. Also keep on eye on the screw that keep the seesaw in the head as they get loose too.