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HomeAircraftHelicopterRobbe Cuatro - Millennium - Nova - Dyna-X › CF frames and tail rotor pinion
07-18-2002 03:46 AM  16 years agoPost 1
freestyle

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Redmond WA USA

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I just installed a set of CF sideframes in my Futura, and the crown gear <-> tail rotor pinion gear mesh is nowhere near tight enough. When the pinion bearing block is all the way down in it's slotted holes, there's still a couple millimeters of vertical play in the main gear / crown gear assembly.

Far as I can tell, I need a 2mm thick washer under the main gear, or I need to extend the slots for the bolts that hold the pinion bearing block. Has anyone else run into this? How did you get around this problem?

Thanks.

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07-18-2002 04:17 AM  16 years agoPost 2
freestyle

rrVeteran

Redmond WA USA

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just for completeness...
I should point out that I'm using a split collar to hold the mainshaft in place, instead of the mainshaft sleeve. The collar isn't tightened yet, hence the free play. Of course, if I DID tighten the collar, there would still be about 2mm of slop between the pinion and the crown gear. That's the problem.

The collar (like the sleeve) only stops the main shaft from sliding up. The problem is that the main shaft sits too low - or maybe it's the pinion block slots that are too high.

Either the pinion needs to get lower (read: extend the slots for the bolts that hold pinion bearing block), or the main gear needs to be held higher (read: put washers under the main gear).

This was not a problem with the stock sideframes. Are the new frames bad, or am I overlooking something?

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07-18-2002 10:14 AM  16 years agoPost 3
helicrasher

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Belgium

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Had the same problem with the carbon frame (original from ROBBE)
"extend the slots for the bolts that hold pinion bearing block"
That's what I did and used some washers.
One year later, NO problem.
futura contest
mille II
raptor 60

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07-18-2002 01:43 PM  16 years agoPost 4
Rchover

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Nate,

IMO I would extend the slotted holes down alittle, I have done this myself in the past, ez to do.

I would NOT shim the main gear , that would add height the main shaft and all its related, parts, links etc.

Jeremy

Jeremy

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07-18-2002 05:51 PM  16 years agoPost 5
freestyle

rrVeteran

Redmond WA USA

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Thanks guys.

Shimming the main shaft and adjusting the bellcrank-to-swash links should be a pretty quick operation, so I'm going to do that.

I wish I'd seen this coming - I would have sent the sideframes back for a set with the holes in the right places. This is not the level of quality Robbe is famous for.

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07-18-2002 09:37 PM  16 years agoPost 6
bob00

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Toronto, ON

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Nate,

Sorry to hear about the mis-fit. We have 2 SE's at our club with CF frames from Bob J. and they were spot on.

Your plan to shim the mainshaft will not be that easy because unless the SE kit has been changed the bellcrank to swashplate links are 1-pc molded links - not adjustable. Shimming will also result in the maingear/pinion alignment being displaced by the same amount.

Extending the slots in the frames may sound like a mess, but a 3mm round fill will make short work of those CF frames (we slot our Mille frames to take YS80's) - less than 1 minute per hole.

Good luck whichever way you go.
- Robert

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07-20-2002 03:27 AM  16 years agoPost 7
whrlybrd

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Little Rock, AR

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Had a similar problem with slightly tight tail drive pinion and CF frames. Small file and a short time later it was a fit..

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07-20-2002 03:41 AM  16 years agoPost 8
z11355

rrMaster

New England

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I tossed those stupid molded one-piece double
links and used real rods and links. There was
no way to get the full 3D geometry correct
using them.

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08-21-2002 06:33 AM  16 years agoPost 9
freestyle

rrVeteran

Redmond WA USA

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Epilogue
I shimmed the main shaft 2-3mm, adjusted the bellcrank-to-swash links to compensate, and put in a few flights that way.

Then I had the auto clutch problems I wrote about in another thread here, and the shims made it a pain in the butt to remove/replace the main gear. So, out came the file, and after a few minutes of work and another tweak on those links, everything fits together nicely again.

Shimming the main shaft took less time, but it made maintenance take more time and wasn't worth the trouble.

Also, from all the asking around I did, I get the impression that Robbe CF frames had this problem about a year ago (which is when I got mine (yes, they are genuine Robbe parts)), but that problem has been fixed and new frame sets line up perfectly all the way around. So, if you're buying new frames, you probably don't have to worry about this... but if you get some old stock, filing is the better way to fix the problem.

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