How to fix your broken BR head the messy way.

[nihil]

Title says it all, heres the broken head:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-004.jpg

Sand/cut the little ring from around the center hole:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-005.jpg

Roughen the surface, making sure to break off one of the arms in the process. 17mmx17mm CF sheet will serve to strengthen. If you have glossy on both sides, roughen up the side that will be glued:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-006.jpg

Glue things back in place:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-007.jpg
http://nihil.rchomepage.com/br/brheadfix/brheadfix-009.jpg

I added some baking soda+CA around the arms for added strength:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-011.jpg

Now, no matter how much fun it may seem, or how badly you want to, gluing yourself to the workpiece will result in broken pieces and a considerable amount of "foul" language. I rushed through the second one, and here is the difference:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-012.jpg

A surprisingly fixed head:
http://nihil.rchomepage.com/br/brheadfix/brheadfix-015.jpg

No idea how much weight was added.

[AustinTatious]

Hey, dont use Baking soda!

use some Micro Balloons. Even a small amount of baking soda is surprisingly heavy.

[nihil]

Hey, dont use Baking soda!

use some Micro Balloons. Even a small amount of baking soda is surprisingly heavy.

Never actually seen microballoons before, heard about them though. What do they do?

[KeithK]

Baking Soda acts as a kicker for CA. Do micro-balloons? I thought they were made of a foam-like substance and would melt with CA. Have I learned something new?

[Aggressor]

microblaoons are very very fine particals of Glass

we use it to mix with expoy resion for glassing a plane and or doing detailed work ie: wing fillets,gun ports etc....


and yes baking soda its a really good accelertaor for ca

[AustinTatious]

Yes, the microballoons act as an accelerator as well... You get the same effect as with baking soda, but at 1/1000 the weight. Its like concrete yet not tooo hard to sand. They cost a bitmore than baking soda yes, but a bottle last a long time... Just abotu every hobby shop sells them. They come if a few different forms, i prefer the white dry ones.

[Aggressor]

wow ill have to go any try that new i did not think micro baloons would have that kind of KICK

as far a a small bottle i have a 1gal jug full of micro blaoons from a local fiberglass store

i spent 10 dollars for it
and its just the same as a tiny little bottle of it for 15 dollars

:D

i have used only 1 gal of this stuff in the past 5 years now i am on my second gal

i have been bulding for the past 25 years free flight up to giant scale,cl

[rebuildit]

microballoons can weaken a joint, so use as little has possible,

[nihil]

Finally got a new scale, and AUW with one rotor reinforced on both plates, is 46g

[NormL]

Nihil,

This is exactly the failure I have repaired (and re-repaired :rolleyes: ) on my BR.

How did you get the plates apart? Pull a pin out? Flex a part?

I tried tugging on a pin with some pliers but it was pretty solidly in, so I did not want to risk breaking it.

It would obviously be much easier to work on if I could get it apart as you have.

Thx.

- Norm.

[nihil]

I was able to yank one pin out with pliers by grabbing and twisting. The other had a pin short enough to bend the arm out and off of it without breaking.

[NormL]

Well, this hub break is starting to look like a fairly common failure mode.

I went to the local Radio Shack, which the web showed to have 1 BR in stock. My thinking was that the manager couldn't resist playing with it, and may have crashed it. Then I could make an offer on it for parts.

Well, turns he didn't resist playing with it, but he already spare rotors on hand to make the repair. The broken rotor had snapped at the hub much like in nihil's photos, and since I had already made this repair on mine, I offered to buy his broken rotors. In the end, he sold them for $1. :cool: A nice guy, eh?

Well, my euphoria wore off some when I realized that under the tape he had used to try and repair the rotor was a flood of CA glue, which had also seized the critical hinge joint. So I spent several hours trying to avoid the acetone fumes as I worked the glue down, disassembled the hub, and rebuilt it. I tried sliding the pivots off the pins, but was left with a stress fracture under one, and the other broke right off. (Maybe nihil's sanding wasn't the real cause of his dropping off...maybe it had a stress fracture too.) The other rotor also needed some work, but in the end, they fly real nice.

Having a spare set of rotors will maybe let me entertain the idea of letting someone else (the kids?) try flying it. :D

- Norm.

[Kwok_Yu]

NormL,
My friend also broke his BR rotor. The cf rod broke at the hub. Does acetone affect the hub plastic at all? Can you soak it completely in acetone, to desolve the CA, without damaging the plastic?

-Kwok

[NormL]

NormL,
Does acetone affect the hub plastic at all? Can you soak it completely in acetone, to desolve the CA, without damaging the plastic?

-Kwok

Kwok,

Yes, the hub plastic seems quite impervious to acetone, thankfully. I had to soak mine a lot, perhaps a total of several minutes (but not all at once) since there was so much glue (from a bad repair, not the factory), and the acetone only softens the outside of the glue. (Spillage on the rotor blades had no effect either, nor on the CF rod, of course.)

Worse, the acetone evaporates so quickly that it is hard to keep the area wet. Perhaps the additives in nail polish remover help solve this? In my case, I cut a film can down to make a little tub of acetone so I could soak the corner of the hub while all the rotors were still attached, and only use a small volume of acetone.

And, it should go without saying, use acetone only in a well-ventilated area. Nasty stuff. :(

- Norm.

[Kwok_Yu]

NormL,
Thanks for the info. Yes, acetone is nasty stuff. I used it alot at school for cleaning parts and got a buzz on more than one occasion. Always opted for alcohol when there was a choice.

-Kwok