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MiniQuad ESC Prop Strikes

Snarls

Gravity Tester
Mentor
#1
Recently I have been noticing slices in the heat shrink around my ESCs, and it's not just one ESC, all of them seem to have been hit in some way. My ZMR250 has the ESCs mounted on the arms which is great for active cooling, but puts them in danger of prop strikes. I figure the problem is that when a prop breaks it either flies with it's momentum into the ESC, or the prop fractures half way through so that it's bent down enough to hit the ESC where it fully detaches itself. I know it can't be a full speed hit because the slices do no go all the way through the heat shrink.

I put it on the back of my mind to provide these ESCs some more protection, but today finally made me take action. I hit a tree going medium speed and fell down into some long grass. I was thinking a prop probably broke on the tree and hoping the grass saved the rest. I was right, there was only one broken prop, but there was also something worse. The power lead to one of my ESCs had completely sheared off. Back home doing some micro surgery I thankfully discovered that the pad was not ripped off and was able to solder the lead and capacitor back on. I could not reshrink that part of the ESC so I added some hot glue and used some new found Friction Tape to seal it off. While I was at it I decided to take some tape and use it to secure the ESCs to the arms instead of zip ties. The tape seems to hold up to prop strikes on my power leads so far so I will give it a shot at protecting the ESCs.

So basically this post is to ask you guys if you experience prop strikes with arm mounted ESCs, and what you do to avoid damaging them, or if that's just part of miniquad flying. Let me know. Thanks!



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Cutting some shrink away to reveal the ripped off lead.

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One of the other ESCs that have been hit.

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The power lead that has taken dozens of hits by rogue blades.

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ESCs after wrapping them to the arms with some friction tape.

Bonus: The crash could have ended much worse. Here is how the battery was positioned when I found it: https://instagram.com/p/5nRlifyu1g/
 

Julez

WOT and going nowhere
#2
Yeesh! Glad all your electronics are okay.

The thing that immediately comes to mind for me is to simply mount the ESC's under the arms. That way you don't have any danger of the prop slicing it.
 

PHugger

Church Meal Expert
#3
Personally I think the cable tie looks like pretty good reinforcement. That nylon is pretty tough and would probably offer some protection. Add another cable tie over the end where the shrink wrap is getting cut and maybe over the wires too. When a prop hits the nylon cable tie it will either break or slide over.



Best regards,
PCH
 

Snarls

Gravity Tester
Mentor
#4
The thing that immediately comes to mind for me is to simply mount the ESC's under the arms. That way you don't have any danger of the prop slicing it.
Good point did not think of that. I would try that if my wiring did not make it so hard to move the ESCs around, and also the fact that I fly without landing gear :/

Personally I think the cable tie looks like pretty good reinforcement. That nylon is pretty tough and would probably offer some protection. Add another cable tie over the end where the shrink wrap is getting cut and maybe over the wires too. When a prop hits the nylon cable tie it will either break or slide over.
Another good point that I did not realize. I think the zip ties I was using are way to narrow and may have stopped some props once or twice. The problem is the hits are happening all over the length of the ESC, from motor wires in the front to the cap in the back. If this friction tape proves to not work I will try some wider zip ties or those rap straps I see many mini fliers using.
 

Snarls

Gravity Tester
Mentor
#6
I like to put a rubber band around the power lead and one of the rear posts. This keeps it in place and away from the props.
Good tip, I've been meaning to secure it, but it is in the same back of my mind that the ESCs were. I guess I should do it now rather then later when the rogue prop finally achieves its kill mission...
 

jhitesma

Some guy in the desert
Mentor
#7
Have had it happen on all of my minis. Just part of crashing on something this small. I've actually cut through the ESC power wires more than once on my friends warp from it. Haven't managed that on any of my own just yet - came close on the twitchity 230 a few times but didn't get all the way through the wires :D

Best advice I can give is crash less - as if that's going to happen :D
 
#8
With the two ZMR's that I just finished building I have the ESC's on the arms of one, and inside the case on the other. with the scratch build the ESCs were on the inside of the arms so the props would have had a hard time hitting them, but they were also oddly exposed. I think the ziptie idea is a good one an I think I am going to do that right now before I forget!

DB
 
#9
Sounds like the same thing mentioned, but props should flex the other way in propulsion, but may likely still spin and be bent in upon crash impact. I hate stuff like this and, though not as much a problem till pre-designed minis... still remains, yet another continuing zen puzzle of getting all assembly and design better perfected. Hope that makes sense as, I say superfluously, a far from perfect response.

I'm all.. 'glass half empty' and 'half full' at the same time.
 

cranialrectosis

Faster than a speeding faceplant!
Mentor
#11
I hit my ESCs when I crash upside down on copters using short motors all the time. I started noticing this when I went to 2204 'pan' type motors.

2204 (the 04 part) motors are the culprit. The motors aren't tall enough to put the prop above the boom far enough to prevent whacks when the prop gets bent by a crash.

I never had an issue with 1510s or 2212s. Even 1806's don't do this often with HQ props (more common with plastic gemfans).
 

Cyberdactyl

Misfit Multirotor Monkey
#12
Yea, let's say you're flying with 2300kv motors using 4S.

That's 2300rpm x 16v = 36,800rpm. We all know it's no where near that, so let's be very conservative and use 40% of 36,800 for full throttle or 14,720rpm. Remember, this is conservative. . .

Using a 5" prop x 3.141592 = 15.7"

14,720rpm x 60 min. = 883,200 (for an hour)

883,200 x 15.7" = 13,866,240 inches per hour

13,866,240 / 12in = 1,155,520 feet per hour

1,155,520 / 5280 (ft in a mile) = 219 miles per hour

So I can easily see having a piece of the prop break off and hit something on your quad at well over 220mph is going to do some damage.
 
Last edited:

jhitesma

Some guy in the desert
Mentor
#13
]
I never had an issue with 1510s or 2212s. Even 1806's don't do this often with HQ props (more common with plastic gemfans).
You're just not crashing hard enough Cranial ;)

On my knuckle I've had props hit the booms before. Haven't hit the ESC's because they're mounted inside the frame on that build - but even with 2212 motors with collets so the props are pretty high above the booms I've managed to get prop strikes on the frame in crashes.

I've yet to take out an ESC from a prop strike even if I have cut the wires to them from them.

On the other hand I've also killed an ESC just by crashing hard. The oscilators are fairly fragile - which is why I now mount my larger ESC's with some 1/4" foam under them. Which also makes me nervous about putting ESC's under an arm since they're more exposed to damage from landing or flying over things there.

On my emax 250 I have them mounted inside the frame - I was worried about heat when I did it but so far haven't had any issues with heat thankfully. I did run the wires under the arms on that build to protect them from prop strikes...but as I feared I've damaged them in crashes since the bottom of the arms are more exposed.

So I'm back to my original conclusion that the only real solution is to not crash :D
 

Snarls

Gravity Tester
Mentor
#14
Thanks for all the insight guys. I thought I couldn't be the only one who had this issue and looks like I'm right, but it's just part of the miniquad experience for now. Definitely some food for thought when I choose my next frame or if I design one of my own.

2204 (the 04 part) motors are the culprit. The motors aren't tall enough to put the prop above the boom far enough to prevent whacks when the prop gets bent by a crash.
Looks like the only solution is to add some taller motors! Yeah that's the excuse I'll use.

So I can easily see having a piece of the prop break off and hit something on your quad at well over 220mph is going to do some damage.
Wow, thanks for doing the calculations. Good to know an approximate number for the speeds these blades are traveling at. Also really supports how dangerous these blades are when spinning.
 
#15
Frequency probably due to more frames, more speed, more often, etc.

Prop clearance reduction, rpms, etc too.

Maybe an excuse for angled motor spacers... (?) (ah huh, yeah... )

... and less pineapple up-side-down express crashes... (where's the nodding smiley face ?)
 
#16
I dont know if its been mentioned, i skimmed haha. but stiffer props wouldnt do that as much. depending on the brand, length, and material (or price) you could get better results. Ive never sliced an ESC on my mini, unlike some of you guys here, and obviously yes ive had crashes hard enough to separate all the pieces of my blackout in a nice little hole in the ground :) never sliced an esc, im using 6x4.5 gemfans. Does motor can depth vary much from motor to motor? Im using EMAX MT2206's, and theres maybe about 8-10mm space between the smallest gap between prop and ESC/wires. Though yes, i do use zipties. *thick* ones. maybe thats attributing to the success haha.
if its a serious problem, maybe get some spacers to actually raise your motors off the arms by like 3-5mm? That little extra space might do more than you think!