Replies to This Discussion

Permalink Reply by Jack de Valpine on August 26, 2012 at 10:05am

Here is an image that shows the slack with a stock prop.

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3D RoboticsPermalink Reply by Chris Anderson on August 26, 2012 at 10:58am

Hmm. The props I got were black and they fit perfectly. It looks like you got APC props, which are better (less flexible) but it does look like APC doesn't include a wide-enough range of rings. I'd suggest you do what Robert did and put in the smaller ring and drill it out a bit. I'll talk to the team about checking on that. 

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Permalink Reply by Jack de Valpine on August 27, 2012 at 5:48am

It looks like the current kit gives options for two APC (grey) prop sets depending on the motor selection. Does this same issue occur with the smaller motor/prop combo?

I guess I will try drilling, although I am a bit concerned about precision as I only have a cordless drill and not a full drill press setup.

Thanks for all your follow-up on this. I appreciate the information!

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3D RoboticsPermalink Reply by Chris Anderson on August 27, 2012 at 8:07am

Jack. The issue with APM props is only with the 11" props on the 880 motors. The 10" props on the 850 motors, which is what most people choose, are fine. 

DeveloperPermalink Reply by R_Lefebvre on August 27, 2012 at 3:37pm

I just had a look at my setup.  For reference, I have the small 850kV motors.  The shafts are 4.58mm.  The APC props that it came with have adaptors at 4.72mm.  So .14mm gap.  Not too bad.

However, I broke one, and had to buy an all new set from Canada Drones, black ones, and the nearest prop adaptor is 5.2!  Not good at all.

Now, trying to understand the situation...  where do these numbers come from?  Well, I checked my old-school prop reamer and the first size is 4.75mm.  It's actually 0.1875", or 3/16".  So that's the old prop shaft size.  I bet if I dig out my old OS FP .15 motor, that's the size.

So even if I ream out the undersized adaptor, I'll end up with a hole that is too big.  Why is the shaft adaptor the size that it is (4.58mm?).

None of this is 3DR's fault.  It's an industry problem.  I think with all these slow flier airplanes and electric motors, people have gotten sloppy.  And these are the parts we're buying.

And then let's not even get into the fact that the props only have a prop ring at the bottom, not the top.  So the angle of the prop must be set by the top and bottom clamping surfaces.  But the bottom collett is adjustable for angle, it's just sitting on the cone of the shaft adaptor!  So the only thing setting the angle is really the top nut, which is only having it's angle set by the thread on the shaft adaptor, which is mere sitting on the shaft! What a disaster.

Permalink Reply by Brad Pittevski on August 27, 2012 at 5:35am

yes, it is the APC props for me here too. I ended up using drills in steps on the rings once they were mounted: 6.1mm, 6.2mm and 6.3mm one after another to keep it centered as good as possible.

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Permalink Reply by Jack de Valpine on September 1, 2012 at 11:05am

Hi All,

 

Thanks to everyone for input on the prop washers for the APC 11x4.7 props. I bought a 6.3mm drill bit from McMaster Carr and that seems to have done the trick. Now on to the next issue.

I was just mounting the props to see what it all looks like (I will remove for testing, etc) and noted some issues with the aluminum prop adapters that came with the 880 motors I purchased with my kit. For a part that is so important to the safety and function of this machine, the dimensions for the prop adapter seem to be pretty much all over the place. Initially I noticed this by the varying way in which the collar fits on the axle adapter (please see the photo for my terminology as well as the elements I am measuring). Here is what I came up with taking some quick measurements:

AXLE ADAPTER

	A	B	C	D
diameter at base	8.55	8.52	8.72	8.48
interior height	10.12	10.5	10.5	10.6

COLLAR

	A	B	C	D
inner diameter at base	8.23	7.92	7.7	7.76
height	8.28	7.36	8.24	8.26

So one concern is making sure the collar is able to exert enough force on the axle adapter when tightened down so as to be safe (skipping applications of locktite for the moment). I can mix and match the collars with the adapters based on the diameters and can I think achieve reasonable results.

The other concern that I have is that for axle adapter (A) the interior height is significantly different and in addition the interior diameter along this height is tight compared to the others. Thus any prop mounted with this adapter will sit higher than its mates and there is uncertainty resulting from the difficult of getting the adapter to snug down on the motor shaft.

Comments, thoughts or suggestions? Should I request another adapter kit from 3DR?

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Permalink Reply by Mark Lewus on September 3, 2012 at 12:00am

Any tolerance in prop height is not a problem because the largest contributor to any prop's height relative to the others is the build tolerance of the frame and flex in the frame tubes and the prop itself due to flight loads and differential thrust. The adapter height tolerances you mentioned add up to maybe 1-2mm (0.040"-0.080"). The ends of the frame tubes and props will flex far more than that. 

I have never known retention to be a problem with these. It takes very little difference in diameter and clamping force to hold the adapter tightly to the motor shaft under these sorts of loads. The collar very firmly compresses the bottom of the axle shaft. So the only risk is if the adapter is still loose on the shaft with the collar almost at the bottom of its travel. I have never found this to happen and it's easy enough to eyeball when you assemble everything.

My biggest problem with these adapters has not been that they are too loose, but too tight. I have, several times, over-tightened the spinner nut, which stretched the soft shaft alloy past its elastic limit and caused the shaft to snap. Once it happened in flight and caused me to lose an airplane prop. This would be catastrophic on a quad.

Now I usually use drilled grub screw adapters. They are far stronger than collet adapters since there is no neck, and if you get ones of decent quality, runout is not a problem. But to guarantee retention, you really do need to use Loctite or grind a small indent on the shaft for the grub screws to grab.

I think the adapters you have will work fine. Good luck with your quad!

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Permalink Reply by mP1 on February 10, 2013 at 6:12pm

Could you provide a link to the ones you use. Im not a fan of collets and would like try other adapters.

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Permalink Reply by mP1 on February 10, 2013 at 7:01pm

How does one remove a collet and prop assembly that is stuck ?

In  my case the easy bit was sliding the collet off the motor shaft with a screwdriver, and this only required a small bump. However the collet is stuck. I loosen the bullet nut, as all turns simply spin the entire assembly. The four gaps in the base of the collet are very narrow and past experience tells me attempting to force something in them to get a grip damages them permanently.

Any tips ?

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Permalink Reply by Bill Bonney on February 11, 2013 at 12:27am

Use a prop puller http://www.rcdude.com/servlet/the-765/Hyperion-Collet-Puller-for/De...

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