Mostro Main Blade Grip Bearing Size?

[byter182]

Hey Guys,

After breaking down, cleaning, re-greasing and putting back together my main blade grips, I found them to be tight and notchy. Reassembled per Mostro instruction manual. Not so bad if I loosely tighten the spindle bolts but don't want to do that.

Thinking the main shaft bearings need replacing. Anyone know the size of the main blade grip bearings?

Want to replace w/sealed Boca Bearings or similar. Plan on using blade grips this way until I get a new set of bearings so don't want to crack the thread lock just to measure until the new set arrives.


Byter182

[eddiscus]

I have found the Mostro head to run tight on initial assembly. Would like it to be a little smoother.
The best I can come up with in their parts breakdown is it seems the AV000616 10x19x5 should be the radial bearings for the grips. I am about 95% sure as I do not have a bearing on hand to measure.

[vburge]

See the unofficial parts pdf on this thread:
https://www.helifreak.com/showthread...hlight=bearing

[byter182]

Originally Posted by eddiscus

I have found the Mostro head to run tight on initial assembly. Would like it to be a little smoother.
The best I can come up with in their parts breakdown is it seems the AV000616 10x19x5 should be the radial bearings for the grips. I am about 95% sure as I do not have a bearing on hand to measure.

Thank you. It's the same size as the part # in vburge's pdf manual. Two members agreeing w/this size for the bearing is good enough for me.

Originally Posted by vburge

See the unofficial parts pdf on this thread:
https://www.helifreak.com/showthread...hlight=bearing

Thank you Vburge for taking the time to look up and adding bearing part #'s to the Mostro pdf manual. It's very useful for me and I'm sure other members as well. Perhaps on the next Avant Mostro manual update they will include a parts list.

[byter182]

Do you guys think any of these bearings will work?

http://www.amain.com/rc-cars/thunder...trpd1969/p2651

http://www.ebay.com/itm/MR6800-2RSC-...ht_2832wt_1034

[byter182]

No matter what I do as soon as I tighten up the spindle bolts, the grips become very tight. I've changed the bearings several times and greased and re-greased the thrust bearings w/tri-flow. All to no avail.

If I loosen up one of the spindle bolts approximately a 1/4 to 1/2 a turn, the grips loosen up to acceptably. I think if I use thinner bolt washers it may resolve the problem. Anyone know of a link where I can find thinner bolt washers? Or perhaps the other option is to use lots of threadlock and just tighten the bolt then back off about 1/2 turn.

Any thoughts?

[tony stevens]

Have you tried taking out the o ring that sits in the face of the dampner?, they are only there to preload the grips and are not needed I believe.
I wouldn't recommend either of your other suggestions tbh. Thinner washers could bend during use and backing off the spindle bolt coud result in you loosing your grips during flight.
Failing that I wouldn't be surprised if you have some machining problems with your grips as many others will tell you.

[Pitch-Itch]

Originally Posted by tony stevens

Have you tried taking out the o ring that sits in the face of the dampner?, they are only there to preload the grips and are not needed I believe.
I wouldn't recommend either of your other suggestions tbh. Thinner washers could bend during use and backing off the spindle bolt coud result in you loosing your grips during flight.
Failing that I wouldn't be surprised if you have some machining problems with your grips as many others will tell you.

This is correct, the orings are not needed. I talked with Augusto extensively on the head, and he gave me two methods of fixing the stiff head. He uses both of these methods on his own helis:


- You can remove the pre load oring. Given the exact dimensions of your head/dampers, this can make the head too loose. If it's too loose, then put the oring back on and use method 2.


- Method 2: Sand the flats on the dampers just a touch. Get a flat piece of glass, lay some 1k grit sandpaper on the glass and start removing material on the FLAT part of the damper. Just a couple thou on each damper is usually enough.


I went with method #2.




**** Before trying either thing, make sure to compress the dampers into the head as hard as you can. I used an arbor press from Harbor Freight. Sometimes just mashing them in there with some good force was enough to permanently compress the orings enough to make the head smooth. Just a thought if you had a press.

[Pitch-Itch]

Originally Posted by byter182

No matter what I do as soon as I tighten up the spindle bolts, the grips become very tight. I've changed the bearings several times and greased and re-greased the thrust bearings w/tri-flow. All to no avail.

If I loosen up one of the spindle bolts approximately a 1/4 to 1/2 a turn, the grips loosen up to acceptably. I think if I use thinner bolt washers it may resolve the problem. Anyone know of a link where I can find thinner bolt washers? Or perhaps the other option is to use lots of threadlock and just tighten the bolt then back off about 1/2 turn.

Any thoughts?

See my post above this one. Those 2 methods are the ONLY 2 things that Avant recommends. Anything else has the potential of being dangerous. Hope this helps.




As an aside, I built a total of 6 Mostro heads while I owned one. Literally each head had this issue, save for one that Avant sent me that was pre built. If you'd like, you could send the head to me and I'd build it out and send it back.

I really do think you can get it working nicely on your own, as it's easy, but the offer stands.

[eddiscus]

Byter 182

Would have thought that had corrected this by now. See older threads.

https://www.helifreak.com/showthread...ght=head+grips

https://www.helifreak.com/showthread...ght=head+grips

[byter182]

Thank you all for the intuitive suggestions. I will initially try the easiest route of removing the inner o-ring that's closest to the main shaft. Hopefully that will work. If not, I'll try method #2. Sanding the dampeners down some. If all fails, then I may just take you up on that offer Pitch-Itch and send the rotor head over to you.

[byter182]

Removed one of the O rings on the dampers and it worked like a charm. Grips are perfect now.


Thanks All,
Byter182

[Hawk404]

I was one the guys with the fixed pitch head. If I'm remembering correctly it was a known machining issue.

I was warned off the various fixes as if it started off bad enough that the grips locked up solid you had ruined the bearings when you tightened down the head assembly.

But that was back when replacements were easy to get.

I would guess if you only got them "notchy" as opposed to "locked up" you're probably good. My first one was quite literally fixed pitch - the grips wouldn't budge by hand.