I hear you on using adhesive to secure the adaptor. Wish it wasn't necessary but my own experience is pointing in the same direction as what you are already doing. Gotta bite that bullet it seems.

tn

Originally Posted by PAPE

This makes total sense, I have seen it happen on other fans, and this is why I mount all my adapters the following way. I don't like flat spots on motor shafts and if there is one I usually fill is with jb weld. When I mount an adapter I drop 3 or 4 drops of red loctite in the adapter hole. Then I press it against shaft until it bottoms out and quickly start going at the grub screws to get the best run out, then let it dry 24hrs.

This way my adapters never shift, but if it has to be removed it will have to be heated.

I'm thinking maybe I don't understand your question, Michael.

I haven't found the need to grind flats - especially with 4 grub screws. I am sure of this since when I disassembled the failed unit there was no evidence whatsoever of the grub screws having slipped rotationally.

Now you are possibly thinking that for the runout to change mid flight something has to move. But the slip is not rotational in nature ... I'd have seen evidence of it on the shaft. The slip must be along the axis of the shaft, and it must be ever ever so miniscule. I truly don't see how flats could prevent this kind of movement.

One last thing. Depending on the tightening sequence and torque used with the grub screws, you can alter the runout of these adaptors. Zero runout is obviously the target, and so we make a reasonable number of trial & error attempts so as to end up with (1) equally TIGHT grub screws and (2) next-to-zero runout. Having or not having flats would neither help nor hinder this process.

Or am I completely missing the gist of your question??

tn

Originally Posted by Michael Paxton

Why aren't you guys just using a dremel cutoff wheel to make a flat on one of the grub screw marks when you are adjust the adapter for run out?

OH. I thought your adapter was spinning. Nevermind.
When I was balancing mine (before I gave up until you guys figure out a solution) I could put pressure on any one of the blades after balancing and it would throw the fan out of balance.
It would essentially move that one blade around in it's spot enough to throw balance off.

Originally Posted by Thomas Nelson

I'm thinking maybe I don't understand your question, Michael.

I haven't found the need to grind flats - especially with 4 grub screws. I am sure of this since when I disassembled the failed unit there was no evidence whatsoever of the grub screws having slipped rotationally.

Now you are possibly thinking that for the runout to change mid flight something has to move. But the slip is not rotational in nature ... I'd have seen evidence of it on the shaft. The slip must be along the axis of the shaft, and it must be ever ever so miniscule. I truly don't see how flats could prevent this kind of movement.

One last thing. Depending on the tightening sequence and torque used with the grub screws, you can alter the runout of these adaptors. Zero runout is obviously the target, and so we make a reasonable number of trial & error attempts so as to end up with (1) equally TIGHT grub screws and (2) next-to-zero runout. Having or not having flats would neither help nor hinder this process.

Or am I completely missing the gist of your question??

tn

completely agree with your assement TN
I think if I had this problem I might try using hysol and try to get 3 or 4 drops at the bottom of the hole so that the waxed up motor shaft is in the glue, like a 1/4in of the end of the motor shaft. then install/tune the adapter to the motor and set aside in the proper orientation so as the glue levels out evenly and let cure......I think that might work.
just a thought

You need one flat spot to keep the rotor from changing position on the motor shaft. If you have a perfectly dynamically balanced rotor and it twists just a few degrees it will be out of balance, sometimes quite a bit. As I have stated before, try the adapter in all 4 possible positions on the one flat spot to find the straightest position. If the adapter has any play then epoxy is needed to steady it in one position.
TN I think your adapter may have twisted on the motor shaft causing the imbalance that made the blades rub.
Cheers

Gentlemen,
As more I read in this topic, as less zest I will have to build in these badly fan unit in my plane. It's for experts only.
I will go back to my time-proven WeMo.

Thanks for your experience.

Regards
Viper

Hello,
Extreme RC sells a 90mm w/o lip for about $70. Has anyone used this on an MB339 flyfly? I am looking to do an 8mm setup with HET 700-68-1400kv 8s 5000. I don't want to have to cut up the plane. I originally bought some cs12s from x-flight; they recently sent me new blades for all of the fans I've ordered - they came out to about 4.5grams each. Thanks for any insite.

You don't have to "cut up the plane". Simply cut the aft part of the shroud to the same length as the opening. A hacksaw goes through like butter, then sand flat with a sheet of sandpaper on a flat surface.

Originally Posted by ViperVJG73

Gentlemen,
As more I read in this topic, as less zest I will have to build in these badly fan unit in my plane. It's for experts only.
I will go back to my time-proven WeMo.

Thanks for your experience.

Regards
Viper

Have you watched the video I posted and heard what a properly balanced CS fan sounds like? How can you go back to the "dentist drill" sound a wemo makes?

Originally Posted by 4stripes

have you watched the video i posted and heard what a properly balanced cs fan sounds like? How can you go back to the "dentist drill" sound a wemo makes?

+1....

+1 on that. Ya it can be a lil work some have been lucky to say they don't need balancing lol, but it's well worth the time. I to can not have any other fan in a 90mm plane.

Hey 4stripes, thanks again for your posts

Yeah I agree that a rotor slipping a few degrees would kill the best balancing job, and could definitely lead to disaster. But mine didn't slip. You can see where the grub screws had bit into the shaft and there is no rotational movement. In fact I'd go so far as to say that it looks like no movement whatsoever, but for the vibes to appear mid-flight suggests something moved, right?

I've got yet another fan coming, this time from X-Flight. I'll wax, then align and glue the adaptor to the shaft, glue the blades & then balance it 'til I'm cross-eyed.

Then fly it like I stole it.

BTW, I 100% agree with you on the sound. It is the ONLY reason why I'm still fighting with this unit. Well, that plus the fact that others have clearly got past the problems I'm still fighting with. Without the success stories of others I'd have sadly gone back to fans with poorer acoustics and/or higher price tags. The Jetfan certainly has my attention - especially with ExtremeRC's aluminum (aluminium ) shroud, but all y'all's success stories with this unit keeps me coming back for more!

tn
(hopelessly addicted non-anonymous cross-eyed member of the "CS12 anonymous" club)

Originally Posted by 4stripes

You need one flat spot to keep the rotor from changing position on the motor shaft. If you have a perfectly dynamically balanced rotor and it twists just a few degrees it will be out of balance, sometimes quite a bit. As I have stated before, try the adapter in all 4 possible positions on the one flat spot to find the straightest position. If the adapter has any play then epoxy is needed to steady it in one position.
TN I think your adapter may have twisted on the motor shaft causing the imbalance that made the blades rub.
Cheers

It has been a bit of a learning curve for me with this fan but the results speak for themselves.
Since your fan didn't shift in rotation TN it can only be the slop allowing the fan to wobble sideways, which will throw the balance off as well.
Your next fan will be perfect!
Cheers Eric

a loose sloppy shaft adapter spells disaster no matter what fan your using, this is why this fan's success rate is all over the place. diff motor mnfg shaft sizes vary even though they all say 5mm some are slightly oversize and some undersized so depending on which motor you choose could be the diff between success and failure with this fan. a good running smooth setup starts with the motor and shaft adapter that runs true, if you can achieve that then you might have a chance with hours of balancing

I've never spent hours of balancing and have had more assemblies than I can count for me and others using different motors and shafts.

The good thing is the fan is going to get better throughout time...

addicting more too it

I got to fly me ARC F18E with the CS fan in front of a couple of full size F18 pilots on Saturday. It was hoot hearing the comments about the sound

With a couple of throttle tricks (don't spool all the way down, use slow spool up during taxi) you get the "it sounds real" comments all the time.