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Exploding propellers

#1
I have some problems with exploding propellers on my home built quadcopter.

I use the following propellers: http://www.hobbyking.com/hobbyking/...tandard_Rotation_2_pc_RH_Rotation_Black_.html

My quad weighs about 1.7 kilos. I use the DT750 motors. I have flown it probably 3-4 hours totally and a have crashed it two timed do to propellers braking in mid air. I balance my propellers fairly well, therefore I do not have a lot of vibrations.

Are those propellers to weak for my quad? Or are they just bad quality? What propellers do you recommend for a quadcopter of this size?

900_DSC1666.jpg
 

zev

lumpy member
#2
those props are too weak for a quad that heavy. try going to 11x4.7/4.5, or go carbon fiber. maybe even wood.
 

xuzme720

Dedicated foam bender
Mentor
#3
I used to use those same props and while I never had one break for no reason, I was still getting vibration even with balancing, and occasionally seeing stress marks near the hubs. This was on a hex of around the same weight as your's so I wasn't putting quite the stress you are on them.
I ended up switching to APC and I get much less vibration due to prop flex and have not seen any stress marking on the props at all.

That's a cool looking quad! I know you said homebuilt but is it a scratch build?
 

xuzme720

Dedicated foam bender
Mentor
#6
No need to be sorry. I guess I should have been clearer, sometimes people say homebuilt but they built from someone else's plans or a kit. That was what I was asking.
I'll definitely check out the article! Thanks!
 

xuzme720

Dedicated foam bender
Mentor
#7
Which propellers are best?

Those: http://www.hobbyking.com/hobbyking/..._Propellers_L_H_and_R_H_Rotation_1_pair_.html

Ore Those: http://www.hobbyking.com/hobbyking/..._Propellers_L_H_and_R_H_Rotation_1_pair_.html

The first ones look similar to the plastic ones that I currently have, maybe they are to weak to?
I just ordered some like the first ones. I read they have a little flex but since they are CF, I imagine they will be much stronger than the plastic. I don't have them yet, should be here in the next few days. I can give you an update then...
 
#8
It would be very nice if you could write a little about what you think about them then they arrive. I will probably wait a few days before ordering anyway.
 

xuzme720

Dedicated foam bender
Mentor
#9
No problem, I'd be happy to. I already have some APC and some of the slo-fly plastic in the same size/pitch so I should be able to do a direct comparison as far as flex and performance.
 

Cyberdactyl

Misfit Multirotor Monkey
#10
Now that you have been flying awhile, I would recommend going to carbon fiber from RcTimer. You can buy 11 x 4.7s in bundles of 4 pairs and get them for just under $5 a prop. NOW. . I understand that's around 3-4X more expensive than cheap plastic, but I believe you will be SO much more happy with them.

They basically are vibration free, in that they don't flex from hard pitching and rolling. The worry about in-flight breaking is also basically non-existent. However, they are MUCH more dangerous in that they will slice you terrible vs a minor slash from a plastic prop. But I was having a horrible time with jello and vibration from the cheapo HK props. They come very close to perfectly balanced. I had to tweak the balance ever-so-slightly, the hub mostly, and now wouldn't go back to plastic. The relief of knowing they won't break in mid air was enough for me. The fact that they don't vibrate during hard maneuvering is just gravy.
 

xuzme720

Dedicated foam bender
Mentor
#11
I had the same experience going from plastic to the APC reinforced type. I expect the same type of performance jump going form APC to CF as I had going from plastic to APC, rough estimate...an order of magnitude! :)
 

xuzme720

Dedicated foam bender
Mentor
#15
I had the same experience going from plastic to the APC reinforced type. I expect the same type of performance jump going form APC to CF as I had going from plastic to APC, rough estimate...an order of magnitude! :)
I just got the CF props in and they are STIFF! I haven't had a chance to run them on anything yet but stiffness alone they should rock! Updates as I get them...