New 700 DFC rocking spindle shaft play

[eightythree]

Thought it would be better to post in the E forum for more attention... My new Trex 700N DFC spindle has a rocking play when assembled. I can grab the grips and push/pull without any play. But the spindle rocks (blade move up/down) in the dampers. This concerns me as everything I read about DFC needs very TIGHT tolerances!

All searching comes up short... replace if worn. This is a new build, working out the quirks before maiden flight. So, shim the spindle to remove play?? Defective dampers?? If I were to shim the spindle, is there a readily available shim kit?

Thanks in advance

[Sirolf]

Get a set of KBDD lime dampers.
Use em in the DFC head for a well over a year now and still rock solid

[eightythree]

I may have a blue set in the parts bin. Maybe to soft, but could rule out fitment. Did yours have this end play? I took a closer look, its very minimal play, but if i move grips in teeter-totter fashion I hear a faint 'click'

Seems to need shimmed properly to get rid of the smallest play... my Oxy 3 build needed this.. Align needs to learn fine adjustments are needed!

[Dawiev]

Hi, I have a similar problem on a 600 DFC head.

Where would you put an extra shim ?

[eightythree]

Between the grip bearing and damper. Or find washers slightly thicker. Im not familiar with SAB Division, but do Goblins use shims to adjust? Possible there are sab shim kits that will work?

[dchekas]

A tiny piece of packing tape on the main rotor hub where the dampers go can be used to eliminate a tiny bit of play.

[eightythree]

Thanks for the tip, that area seems to have the play. A thought came to mind, ill admit to not disassembling the bearings in the grip when assembling, do these bearings need retainer glue to reduce play? Then it would be harder to remove for thrust bearing maintenance.

[Heli.Maniac]

On a 600 when I got a package of DFC dampeners (set of 4), I used the first pair and it was a nice and tight fit to the hub and spindle with 0 play. After I had used them for many flights I went on to use the second pair along with a new spindle and it had play between the damper and the spindle just if the damper was less than 1mm out of spec. Same with the old spindle. QC issue more than likely in my case and maybe that is the case for you.

If your dampener is loose between the hub then you can probably fill it with some thin one-sided tape but if it is loose between the spindle then there are not many choices because the spindle has to be able to rotate freely inside it.

I stopped putting retainer on the grip bearing that is towards the spindle bolt for easier maintenance. If the play was axial (as in you pull the grips and it feels like the bolt is loose) then maybe that would be your issue but you said that the grips have up and down play instead.

[eightythree]

No axial play, up/down play. It appears the solid dampers are to loose in the hub. I will disassemble and add tape to damper and inspect carefully. I will report back!

Thanks for the tips fellas

[Dawiev]

Hi, on the 600 head, Align uses a brass washer with a small OD between the head black and blade grip. I've replaced it with the same thickness washer (did not have side to side play), but with a bigger OD. It's from a Blade 550X. Not big enough to catch on the head block though.

By hand, it seems to have eliminated the up/down play. It obviously compresses more of the rubber into the recess. I'll be able to fly in a few days and will check after it has seated and stretched into place.

Not sure what is in the 700 head.

[Heli.Maniac]

That's interesting approach. I would imagine that the blade grip bearing that is towards the hub will start to bind up because the brass washer no longer rides exactly on the inner race. Are your grips smooth now? And also the OP has DFC dampeners which are solid plastic that is uncompressible unlike the normal rubber dampeners so that may not work as well in this case.

[Dawiev]

Hi, the "new" washer is stepped to push only against the inner race of the blade grip bearing - all is good in this regard.

The rubber (synthetic) material in the 600 head is also black and quite stiff, but the original washer has an OD of only 11 mm and doesn't push against the majority of the damper.

Will update once flown and the blades have pulled on the head to seat it all.

[eightythree]

I went over the head last night. I've narrowed the play down to bearing & damper fitment. The dampers were loose fit in the headblock, the outer blade grip bearing were a loose fit in the grips.

Adding 0.1mm shims to the spindle caused the grips to bind, so that wont work..

Trying the tape method, just didnt work for me.. Every attempt to add tape to damper or bearing race, the tape pushed out

I ended up using CA glue. A small layer around the damper, then a drop of accelerator to cure instantly. This provided a nice snug fit to the head block with minimal loss of dried glue. I also used the same method on the outer bearing of the blade grip, but more loss of glue when pressed in

I ended up with a much tighter head, but not completely solid. I may have to revisit after a flight or two, bite the bullet and glue the bearings with retainer glue. I dont get out much these days, but I will report back if I have any news! thanks HF

[dchekas]

If you choose to use tape, it should not be wrapped around the damper or around the hub. This will cause the tape to push out.

Packing tape would be the preferred type IMO.

A tiny ~1mmx1mm square placed at the 12 O'Clock or 6 O'Clock position in the main rotor hub will take out the tiny bit of play.

This has eliminated all slop in the dampers and has lasted quite a few flights on my models.

[eightythree]

CA glue worked excellent on the dampers. I will use tape next time around.
Are you using retaining glue on the grip bearings?

[dchekas]

Yes, I use Loctite 641 on the radial bearings in the main blade grips.

[eightythree]

Can you explain how you remove the bearings and clean the locktite when replacing? Im thinking I will disassemble again for retainer glue.
Thanks !

[Heli.Maniac]

I use a torch to heat up the grip a bit, that loosens up the retainer and it is easy to remove the bearing. Then with a q-tip dipped in alcohol I clean old residue. Use just a small drop of loctite so that it is not a pain to remove the bearing later in the future for maintenance, a very small drop that is then spread around the bearing is all that is needed to hold it in place

[eightythree]

Im very familar mounting bearings with retainer glue.. after all these years what am I afriad of ?! Lol

Just wanted to get a thread with soild info. On such a large heli these fine adjustments are crucial IMO

[dchekas]

I do exactly as above to remove it, although I prefer to heat mine in the oven versus a torch.

15-20 minutes at 350 usually does the trick.