MR60

Thanks "3DR propeller's mounting system" for a... CRASH

Hello,


I was doing my first flights today. And guess what... I crashed !

The crash did happen because the quad flipped (fortunately I was landing and thus almost on the ground) at the same time that one propeller collet came loose off the motor's shaft.

I want to express here some real frustration toward 3DR because of a fault by design in their kit. I had indeed an issue with fixing tight this collet since the 3DR kit was delivered. Although 3DR reads and cannot ignore the massive amount of people loosing props with these stupid collet systems, I wonder why 3DR continues to deliver them. There exist much better propeller's mounts that can be screwed on the motor and that makes it impossible to loose it !

Since I already lost this collet off the motor's shaft during some previous bench testing, I paid extra attention and efforts to fixing it correctly before external flights: i used blue loctite, i made sure I screwed the collet tight enough, etc.

That this is really a mount's design issue : such a system cannot ensure with enough certainty, even if you fix it right, that you will not loose a collet.

Anyway, as a result I broke two propellers, I damaged the protective acrylic arch (glad I had it!) and the responsible collet is of course unusable. (I guess I can be happy it is not overall too much damage)

I would really like 3DR to take lessons of this and change their propeller's mounting systems in their future kits.

Do you imagine what would have happened if I had lost this collet higher in the air ? This is serious.

 

Hugues

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Replies

  • Reason # 47 why collet prop adaptors suck.

    Spend hours diagnosing why quad keeps flipping.  

    Discover one of the set screws holding the shaft into the endbell is loose.  Just enough to stop the propeller from turning at full power. The shaft is spinning in the end-bell.  Try to re-tighten said set screw.  Discover it's soft, strip the socket.  Destroy end bell trying to get it out for replacement.

  • Huges: I replaced the stock prop adapters that come with 3DR/RCtimer motors with these ones from HK -> http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=19586

    Much better.

    I find many parts of the 3DR kits quite well thought out and well documented, but overall I much prefer a platform like the Flamewheel for a lightweight quad and for an AP / Gimbal platform either Rusy's UAP1or2 frame or Quadframe's SIXCopter. The 19mm arms of the 3DR frames are just far too weak and not cost effective to keep replacing everytime you have a "hard landing" or just breath on it funny.

  • For a long, I'm using the 650 v4 engines XAircraft, recommend them because they are extremely reliable and excellent quality.
    the only problem is the selection of propellers 10x4.5 I can only use plastic or carbon
    dji are also those are very good.

    Xaircraft 2212 950kv motor
    weight: 57.4g
    3692638555?profile=original
    2212 MOTOR, 980KV dji motors
    3692638398?profile=original
    engines and accessories, plastic and carbon fiber are very well balanced, and accessories also excellent.
    3692638576?profile=original
    3692638669?profile=original
    3692638590?profile=original

    actually I stay with this because my octoquad up to 2.5 kilograms
    sufficient for canon camera and an excellent performance

    http://www.foxtechfpv.com/

  • Ouch.  Yesterday I was flying and a prop flew off.  The quad tumbled into the ground for its second crash.  I was aware of the prop issue and had those suckers on tight but had not checked them during the last few flights.  Bummer.  My message is only to confirm that this problem is indeed real.  It appears that roughing up the motor shafts with sandpaper is in order.

    Mike

  • Hi!

    I use Hacker prop mounts, Graupner should also be good.

  • MR60
    @norman,
    Does rc timer has the same mount system for the 3dr 880kv?
  • sorry about your accident, I recommend rc timer motors
    http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=... =

    3692635839?profile=original
    3dr are the same I have eight and got some perfect for 2 years.

    3692635850?profile=original

    this place

    http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=....

    3692635989?profile=original
    Bearing only recommend change for a better quality oil or grease with automotive grade 20 w50.

    http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=549&productname=
  • Sorry to here of your problems with the collets. I have a large plastic bag full of these collets which have developed issues after a few flights. I have not had one come loose and like any flying platform they are on my pre and post flight check list. The main problem is you have a mix of the wrong metals. Hardened chrome shaft and poor grade aluminium. The aluminium shaft centre goes out of tolerance and the more you tigthen it up over time the centre shaft hole gets bigger. They also are a major source of vibration. I suspect the motors and these collets are same supplier Jdrones and 3DR use. My advice is get yourself a different set of motors which uses precision prop holder that screws to the top of the motor. With the code now moving to use xyz inertial correction vibration is a bigger issue. The 3DR / Jdrones motors combuned with the collet system have too much variability in this area. They are good for general purpose applcations though. I personally am now looking for a precision motor set and simple direct bolt prop system having gone through a dozen of more motors just for one quad. Another good thing with the drrect prop mounts is the material is usually a harder steel and machined finished,
  • I've used the collets alot and even with a bad crash I never had problems. You have to make sure that the collet 'takes' when you tighten them. I always check with a magnifier to see that the collet is fully compressed around the engine shaft and I usually check tightness before flying. I've re-tightened mine several times and they haven't failed yet.

  • Shaft Length:

    Yes, the shafts are much longer than they need to be.  I cut mine down.  I put the motor in a bag, and pushed just the shaft through.  Then used a dremel wheel to cut the shaft.  The bag serves an important role of keeping the filings out of the motor!

    I don't think multicopters have "special needs".  In a hover, they are making about the same thrust as they would on an airplane.  I think the only difference, really, is that these collets were invented as the cheapest possible way to attach a propeller onto an RC Car electric motor from WAY back in the day when electric flight got started.  And it's just stuck.  It continues to be a really poor solution, but the airplane guys live with it because of "inertia".  It works well enough, and "why fix what's not broken?"  I mean, it IS broken, but for an airplane guy, the loss of a prop means they have a dead-stick landing, go find their prop, and laugh about it as they stick it back on and go for another flight.

    The only thing special about a MR is that the prop loss means you crash.

    And you don't have to buy new motors to use the screw on adaptors.  I bought some Turnigy NTM adaptors to put on mine.  They won't quite fit because the counter-bore is too small.  I can fix that on my lathe, most can't, but I think with some shopping around we can find some adaptors that fit.  They're only a couple of bucks.

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