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Old 05-19-2011, 03:42 PM   #1 (permalink)
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Join Date: Jan 2011
Default To much headspeed

I have a problem and am hoping for some suggestions fixing it (Kinda stumped myself)

Logo 400 with a Scorp 1400KV motor, 13 tooth Mod 7 pinon and Kontronic 80LV ESC with heatsink and a Black V-Bar.

The bearings wore out in the Scorp motor this past weekend and I have just now gotten around to changing them out. The bottom bearing had actually come apart (When I broke the motor down little balls eventually fell out of it

Got everything back together (Replaced the bearings with Boca and replaced the motor shaft) but once it was spooled up for the first time after replacement it didn't seem to arrive at a constant headspeed just kept spooling up (Until we got scared and cut the throttle on it)

Reprogramed the ESC twice and it's still doing it (The person who helped me knows how to program the Jive since he has done many of them. In fact he set up the Helicopter in the first place and it was working fine)

Set a throttle curve at a flat 25% and tached it (Since it didn't sound like a runaway jet engine at 25%) and it was taching at 2500RPM. (Normally this would be around 70% throttle)

The radio is a DX8

Everything was fine before the motor went out (It did get hot when the bearing gave way) but the inside of the motor seems fine and moves freely

Any ideas would be greatly appreciated

Thanks!!
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Logo XXtreme, Kosmik, Pyro 800-48L Futaba 157s/256. Henseleit TDR, Pyro 700-52, 120 Jive, V-Bar 5.3, BLS253/251. Logo 600SE, Scorp 5020-450KV, 120 Helijive, Futaba 451s/251. Logo 400, Align 510MGs, JR 8900G, Kontronik Jive 80+ LV,Mini Pyro 400-14,
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Old 05-19-2011, 04:06 PM   #2 (permalink)
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Two things,

When you tached it at 25% throttle--what was the pitch? Obviously if it was near zero, you would get a higher rpm than if you were at 6 degrees.

Secondly, I am wondering if the jet engine is just the sound of one of the new bearings being bad. Sound can be a scary thing, but not necessarily a good predictor of rpm.

I'm just asking because there is only one reason that the true rpm could be too high, but I don't think it is likely. That reason is that the motor was overheated during the last bearing failure, and the magnets got slightly demagnetized. That would increase the kV, and potentially give you a higher rpm. However if you were running a governor, it is only looking at the commutations, and so the rpm wouldn't change. Also the Scorpion magnets are rated for a quite high temperature before they would experience any de-magnetization. And finally you didn't indicate any excessive issues when the bearing failed--like the motor was "smokin' ".

So a little bit of a puzzle. My guess is the new bearing is making the noise, maybe rotating in the housing???
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Old 05-19-2011, 04:31 PM   #3 (permalink)
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Quote:
Originally Posted by ahahn View Post
Two things,

When you tached it at 25% throttle--what was the pitch? Obviously if it was near zero, you would get a higher rpm than if you were at 6 degrees.

Secondly, I am wondering if the jet engine is just the sound of one of the new bearings being bad. Sound can be a scary thing, but not necessarily a good predictor of rpm.

I'm just asking because there is only one reason that the true rpm could be too high, but I don't think it is likely. That reason is that the motor was overheated during the last bearing failure, and the magnets got slightly demagnetized. That would increase the kV, and potentially give you a higher rpm. However if you were running a governor, it is only looking at the commutations, and so the rpm wouldn't change. Also the Scorpion magnets are rated for a quite high temperature before they would experience any de-magnetization. And finally you didn't indicate any excessive issues when the bearing failed--like the motor was "smokin' ".

So a little bit of a puzzle. My guess is the new bearing is making the noise, maybe rotating in the housing???
The motor did get heated up (No smoking or anything like that but the temp probe 2" away from the motor read 139F degrees. It's always been governed though (With the Jive Govenor). It sounds and flies normally at the 25% throttle curve and when it spools up it sounds normall all the way past where it usually levels out but just keeps spooling up faster and faster. The bearing was preatty much toast though.

Thanks for your help!!
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Logo XXtreme, Kosmik, Pyro 800-48L Futaba 157s/256. Henseleit TDR, Pyro 700-52, 120 Jive, V-Bar 5.3, BLS253/251. Logo 600SE, Scorp 5020-450KV, 120 Helijive, Futaba 451s/251. Logo 400, Align 510MGs, JR 8900G, Kontronik Jive 80+ LV,Mini Pyro 400-14,
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