Broken Props

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Mitglied
Registriert seit: Jun 2009
Beiträge: 13
Hallo,

I have had 3 broken propellers in the last 10 flights, is that normal? :(

Does anyone know good carbon fiber props I can use?

Thanks!
Mitglied
Registriert seit: Feb 2009
Beiträge: 153
Hello!
The props broke in flight? :?
IQA
Registriert seit: Jun 2007
Beiträge: 5129
Ort: 53809 Winterscheid
hey, great quota! I whish I was that good!

Seriously, that is quite normal.
The usual glass or carbon props tend to be too heavy (remember that the motor needs to change his torque constantly).
There is a carbon set available for Quadrocopters, but is quite expensive (I believe 100€ per set of 4).

Also consider that if the propeller does not break on impact, something else might do so instead. This is why I live with cheap props that break and the expensive stuff says in one piece.
Mitglied
Registriert seit: Nov 2007
Beiträge: 10
Hi Thomas!
I finally went to APC 10x4.7's as the current EPP1045's will break in-flight far too frequently without cause sooner or later whether new or used for a bit, with quads weighing over 1kg which is what most of us who do AVP fly at. I also carefully balance my motors and props and do not over-tighten them. There is a very small trade off in performance for AVP type of flying where mainly you hover around. Still a 65cm motor-to-motor quad performs quite well with them. MaxPro EPP1045 folks say they will change their formula to make them stronger, but they say they were never intended to be used the way we fly them on our heavier quads. So if you can't stand the constant worry of an EPP1045 prop breaking with an expensive camera on-board, I recommend you switch to APC's. The EPP1245's break even easier and I would never use them! Use APC 12x3.8's if you have a large and heavy quad. Arthur P. uses them successfully. I also use motors that are not expensive, usually under $20 each, so I'd rather replace them than a camera...;)
Typical EPP1045 prop breaks: http://www.rcgroups.com/forums/showthread.php?p=10416681#post10416681 and http://www.rcgroups.com/forums/showthread.php?p=10407427&highlight=broken+props#post10407427 and http://www.rcgroups.com/forums/showthread.php?p=11683301#post11683301 and http://www.rcgroups.com/forums/showthread.php?p=11228696&highlight=broken+EPP1045#post11228696
Some things to do to mitigate the breaks are to properly balance the props and motors: http://www.rcgroups.com/forums/showthread.php?p=12832508#post12832508 and to use washers that are larger than the hubs on the top and bottom if you use nuts. Problem is that eventually even with all precautions, the EPP props tend to fail. This is a no-go for my quads with expensive cameras on board. It might be a calculated risk you would want if you are just flying for sport and fun. Also bad batches of props have been reported with bubbles showing up in the break areas near the hub.

externer Link:
User image

This pile of broken EPP1045 props has more than doubled since this photo was taken...
My estimate is that 20% fail in-flight at either 1-5 flights or above 50 flights without any other previous damaging strikes. The others were embarassingly my faults, but a 20% chance of a prop breaking in-flight is too much when carrying expensive equipment.
Cheers,
Jim
« Bearbeitet von jesolins am 01.09.2009 00:19. »
Mitglied
Registriert seit: May 2009
Beiträge: 660
Ort: Wien
Bogomir67 meinte
Seriously, that is quite normal.


Sorry but I have to disagree strongly on this part! Currently I have around 100 flights on my
MK with the default EPP1245 (L3-ME Set) and I lost not a single one.

I would not say that it is normal that they break that frequently!
Have you checked on vibrations? Maybe your motors are not running smoothly.

Overall setup (weight and so on) for sure is also something that has to be considered.
MK-Betatester
Registriert seit: Jan 2009
Beiträge: 3093
I have in the last 2 months, roundabout 60 flights (lipo's) and three epp1045 halved in the air, luckily only about 2 meters in height, could be at half the prop still fast emergency landing.
all these were already about 3-4 months old and ~ 80 flights on it.
MK-Betatester
Registriert seit: Jan 2008
Beiträge: 1360
Ort: Helmstedt
EPP1045 will break often.
EPP1245 are much stronger, but they bend instead of breaking.
Mitglied
Registriert seit: Mar 2008
Beiträge: 554
Ort: Bracknell UK
Zitat
Does anyone know good carbon fiber props I can use?


Although these are expensive they are very good. Christian makes them up in his workshop at

http://www.lcc-shop.de/index.htm

I have used these and never had any break in flight. (Many have broken in crashes :oops: )

If you have got past the bad flying / crashing stage then I would recommend these.

Steve
Mitglied
Registriert seit: Oct 2008
Beiträge: 2761
Ort: Wien
Graupner GFK Prop cannot break, too! 5€...
Mitglied
Registriert seit: Jan 2009
Beiträge: 956
Ort: Zürich
Hi,

If you have many "unintentional ground contacts", consider a bigger, stronger landing gear .. that will help protect the props better. You can always return to something elegant when your flying gets better :)
I have probably broken the first 20 or so 1045s since February.

Regards
Soren
Mitglied
Registriert seit: Mar 2008
Beiträge: 554
Ort: Bracknell UK
Another way of avoiding the props hitting the ground is to make up a CFK ring that goes round the whole MK. Should the MK rock over during landing the ring keeps the props from touching the ground. 8)

Steve
IQA
Registriert seit: Jun 2007
Beiträge: 5129
Ort: 53809 Winterscheid
Jim, good to hear from you again!

Maybe there is a missunderstanding on my part (most likely).
The EPPs are OK to break in crashes and when in contact with obstacles etc. That I consider as normal, for they are quite brittle and thin as well. I do prefer this over a severe cut on any of my limbs, and also over a bend motor shaft.

It is however not normal for them to break during normal flight (even with radical torque changes). Therefore, in PieterA's case, I would suggest to check the mountings. It may be that there is some mechanical reason, like an uneven force from the screw or nut holding the prop, or something like that.

As for the APC props - I tested them on my UAVP. I only see one major disadvantage, which is the mass. One would need strong motors (rather: motors capable of high torque) and also a controller that allows active breaking in order to make good use of them.

Graupner just marketed some opposite pairs, in 9" and 11", both at 5" pitch. I am going to test these on my Y6 (EPP1045 on top and 9x5" on the bottom motors). In terms of mass and durability they seem to be in the middle between EPP and APC.
Mitglied
Registriert seit: Jun 2009
Beiträge: 13
papaxiclas, yes the props broke in flight, at 200meters up resulting in a waterlanding.... :-(

I will check the mounting on the motors but don't think that is the problem. My mikrokopter is one with full option and therefore havy, I think the props break when I am decending from around 300 meters up to 100 meters and them give full trottle to stop the decending..... but a prop has also broking when I was just flying normal.


I think I will try the Graupner 9" and 11", both at 5" pitch also
« Bearbeitet von PieterA am 19.08.2009 14:50. »
IQA
Registriert seit: Jun 2007
Beiträge: 5129
Ort: 53809 Winterscheid
PieterA meinte
I think the props break when I am decending from around 300 meters up to 100 meters and them give full trottle


That should indeed not break the props. Maybe one already cracked - OK. But not in the numbers you are reporting. I have flown Copters with those props from 500g to well over 1400g - and also did the "flare" maneuvers - to the effect that watchers were already flinching before I eased off the throttle. No boasting - this is quite a standard thing.

But all of my broken props had some kind of contact with the ground or other things that should not have been there where I was flying... I do know of reports from EPPs breaking during flight but on all occasions it was related to and later related to misaligned prop mounts, washers askew or things like that. Also tightening the screws/nuts sould be done with care.

I don't thnk you had a bad batch. Possible, but unlikely.
« Bearbeitet von Bogomir67 am 19.08.2009 15:38. »
Mitglied
Registriert seit: Dec 2008
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LegoM meinte
Graupner GFK Prop cannot break, too! 5€...


where i can order this props ?
Mitglied
Registriert seit: Nov 2008
Beiträge: 56
Ort: Lancaster, England
I still have the EPP props which came when I bought my MK, never a broken one...They have never had contact with anything but air though.

Must have done hundreds of flights over the months, mainly for the purpose of easy sport flying & video/photo.

When I first got it there were 2 times when I lost props due to a loose nut. Since then I have 2 nuts on each, tightened very carefully so as not to be too tight.

The thought of them breaking in flight horrifies me, but then so does the cost of CF ones!

I really think then they should not break though if they do not hit anything.

Chris
IQA
Registriert seit: Jun 2007
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Try the nuts with the nylon ring built-in. I use them with great results. Or use a drop of loctite or nail polish on the threads above the nut. It will not prevent it from loosening ¼turn, but it won't fall off.
Mitglied
Registriert seit: Nov 2008
Beiträge: 56
Ort: Lancaster, England
Thanks Thomas,

being a "belt & braces" sort of man, I would incline towards a nut, then a locknut & some Loctite!

best wishes,
Chris
Mitglied
Registriert seit: Mar 2008
Beiträge: 554
Ort: Bracknell UK
Just before I took my MK out to fly it today I touched one of the props and it broke!!!!! :shock:

Here are the photos of the break point
User image
User image

What is interesting is that the prop has a weak spot that has produced stress marks radiating from the stress point (the indentation at the top of the prop). The fracture is clearly the white section at the bottom of the prop. If the stress were caused by flying then the fracture would be at the top of the prop with the stress crack at the bottom.

The stress point looks as if it is part of the mould and since Jim (jesolins) has a whole pile of props all with the brake point at the same place, it would be safe to assume that the fault lay in the manufacture??????

Maybe it would be prudent to check the moulds to see if the mould is creating the weak point.

Any thoughts?????

Steve
IQA
Registriert seit: Jun 2007
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Ort: 53809 Winterscheid
Indeed, all my broken ones broke in the same spot (but due to the lawn jumping up to my copter...).
I guess there is a weak spot - but if it wasn't there, the prop would simply breake elswhere.

Again, I never hat a "good" propeller break in mid-flight. I am not saying that I am totally fond of the EPPs but so far, they served me well enough.
Mitglied
Registriert seit: Jun 2008
Beiträge: 405
if you don´t want always to invest to new camera, just because of crashed MK, simply switch to MK8!!! And braking props will not bother you any more. If you already ahve quadro MK, then just prebuy 4 Ctrls and 4 motors and you will get this :-)

http://www.vimeo.com/6751549

with doubled payload!!!

...even with cheep china motors I have 100% sure safe landing.

Stanley
Mitglied
Registriert seit: Sep 2008
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Ort: Petershagen / Weser
Hallo ,

look at this

http://forum.mikrokopter.de/topic-12119.html
« Bearbeitet von Spider Mike am 15.10.2009 08:05. »
Mitglied
Registriert seit: Mar 2008
Beiträge: 554
Ort: Bracknell UK
Zitat
look at this

http://forum.mikrokopter.de/topic-12119.html


I assume that what the topic is saying is that the props can be strengthened to prevent breakage. ?????

What I am concerned is that the props clearly have a fault and the fault should be rectified at source of the problem. Which I think is with one of the moulds.

Since the MK's have no flying surfaces to 'fall back on" so that they may glide or auto-gyrate to the ground the props are the only means of keeping the MK in the air. I appreciate that the MK can fly on half a prop but it is not advisable!

It seems to me to be counter productive to the project as a whole to dismiss this problem when clearly these some of these props are 'not fit for purpose'.

Steve
Mitglied
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SteveG meinte
What I am concerned is that the props clearly have a fault and the fault should be rectified at source of the problem. Which I think is with one of the moulds.

Steve


In my opinion, there can be 2 reasons for the problem.

1) There is a mechanical or electrical problem with the MK itself. I am not sure about this but i think i've seen a few entries in the german part of this forum suggesting that there can be problems with the brushless controllers.

2) Since most people here don't seem to have problems with these propellers (at least not such a massive one) it could be a bad batch of propellers. From my experience with injection moulding i know that there can be weak spots for various reasons and it is hard to find them just with measuring and optical checks. I don't really think that a big number of really weak propellers could sneak through the QC. But who said that these propellers are actually being tested with the same forces we produce with our MKs? I am just guessing here but i think that we are actually using these propellers "outside the parameters" but the company would never consider these propellers as not usable.

I would try 2 things:

get some other propellers (same propellers from a different shop, the Graupner gfk props etc) and do more testing. It's quite possible that it was just a bad batch.

If it is always the same motor, change the motors. If the problem stays at the same spot with another motor then change the motor controller from one axle to the other. Then you will see if it is a problem with a motor or a motor controller.

Good luck, i hope you'll find the problem soon

Stefan
IQA
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Well, there are alternatives popping up here and there, like the Graupner Props (whoever makes them - here they are only sold by Graupner and Resellers), and the tests with wooden props from XOAR look promising as well.

Remember that the EPPs where made for some slow-fly or shock-fly birds - not much load there, and they do glide back to earth if anything breaks.

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