Speed tests crash

[Stolla]

My condolences Marcos, it hurts !, what does your kosmik log say, immediate rpm drop must be something slipping or stripping, if belt stripped you will see drop in headspeed but increase in motor rpm, look for that.
Then the pitch down may be similar what happened to tdr at speedcup.

[marcosp]

That's the weird part, you see the fall in main rotor rpm, a strange jump in Watts or Amps as low as 1000W and back to 6500W for the last 5 seconds, and no loss or rise of motor rpm at all. When I saw the log I suspected the motor. Then I thought it was the belt breaking, when it slips A go down, when it bites again back up. The sound was not intermittent however, constant lower rpm.

Could the Kosmik have had commutation problems? Motor was spinning at 26K rpm since I was governing too high without knowing. Could a commutation problem happen only under load and not when hovering?

[marcosp]

Mark, the normal 3D belt is recommended to be changed every 100 flights. If you see wear sooner. The heavy duty belt I really haven't heard. You have to look at it also to know when it is starting to wear.

[marcosp]

There's a video about belt tension in Banshee forum. It's pretty tight, no more than 5mm movement when pressing the belt between pinion and gear.

[Gerd]

Marcos, if you send the model back to Germany you should add the Kosmik for inspection by Kontronik (that they can forward it to them). Some weeks before IRCHA we had a similar crash with a Diabolo and some SMD parts on one PCB board in the Kosmik became loose from the impact. The Kosmik was declared as totally defective from Kontronik and we got a new one (paying for that in the usual way).

[Stolla]

Marcos please send me your log i will pm you my personal email adress, if you saw drop in blade rpm but not in motor something in powertrain between motor and blades failed or malfunctioned, it can be stripped belt slipping pulley one way, etc but kosmik kept motor rpm steady, fact your amp dropped meant no resistance or very little on motor, typical of any of the abovementioned

[swalko]

Originally Posted by marcosp

Upon investigation of he motor pics and logs it seems 99.999999% impossible that the magnets came loose in flight. It should have caused havoc inside the motor which it clearly hasn't. The glue used is extremely strong to forces and heat but is like crystal, very sensitive to strong shocks like this crash.

Marcos, i once had an accident where the motor magnets released due to commutation failure. Every part of motor remained as new, including magnets. Kontronik service replaced motor bell.

[Karl57]

Very sorry to see this Marcos.
I really hope you get her back in the air soon mate

[marcosp]

Originally Posted by Gerd

Marcos, if you send the model back to Germany you should add the Kosmik for inspection by Kontronik (that they can forward it to them). Some weeks before IRCHA we had a similar crash with a Diabolo and some SMD parts on one PCB board in the Kosmik became loose from the impact. The Kosmik was declared as totally defective from Kontronik and we got a new one (paying for that in the usual way).

Yes, definitely sending it!! Thanks Gerd!

[marcosp]

Originally Posted by swalko

Marcos, i once had an accident where the motor magnets released due to commutation failure. Every part of motor remained as new, including magnets. Kontronik service replaced motor bell.

You mean the commutation failiure caused the magnets to break loose? I am starting to adhere to this theory.

[smsodhi]

Originally Posted by marcosp

You mean the commutation failiure caused the magnets to break loose? I am starting to adhere to this theory.

Good to see you can see some humor in this!!

[abanihani]

Marcos, contact Gmauro and see if that is a possibilty.

[swalko]

Originally Posted by marcosp

You mean the commutation failiure caused the magnets to break loose? I am starting to adhere to this theory.

In my case yes. But in your case i think that magnets released first. I just wanted to say that the engine may not be damaged when magnets become loose.

[swalko]

Originally Posted by smsodhi

Good to see you can see some humor in this!!

So you can try it ... Helijive mode8, VStabi governor. Switch to idle, switch to bailout, fast switch back to idle while motor is still spinning and propably you will see a magic .

[smsodhi]

Originally Posted by swalko

So you can try it ... Helijive mode8, VStabi governor. Switch to idle, switch to bailout, fast switch back to idle while motor is still spinning and propably you will see a magic .

Been there......, done it........, with a P800. Did a bailout on the bench and WHAM.

[mkovalcson]

Originally Posted by smsodhi

Been there......, done it........, with a P800. Did a bailout on the bench and WHAM.

Are you saying that you destroyed a motor by doing that?

[smsodhi]

Yes, but to qualify this, it was an early P800 which had an issue with the glue used to adhere the magnets, and the magnets came lose while doing some bench tests, involving bailouts.

[mkovalcson]

Originally Posted by smsodhi

Yes, but to qualify this, it was an early P800 which had an issue with the glue used to adhere the magnets, and the magnets came lose while doing some bench tests, involving bailouts.

In that case MUCH better to do that on the bench than in the air!

[marcosp]

Originally Posted by abanihani

Marcos, contact Gmauro and see if that is a possibilty.

I've been speaking with Mauro since 10 mins after the crash since we've been working elbow to elbow on this last testing period.

[marcosp]

The GM-4330 magnets are glued in such a way that they can not be broken off applying all your weight on a screwdriver after heating the can to 150ºC. Only way to break them is with a hard shock.