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E-flite . Next D . Fast Lad Performance

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Radio - Servo - Gyro - Gov - Batt > JR 8900G Tail servo
 
 
AlanR8
Key Veteran
Location: Saddleworth near Manchester (UK)

Failed!

This was a brand new servo at the beginning of the year when I converted my R90 to a V-Max. Because of the weather and commitments I doubt it had more than 20 flights on it!

Its controlled by a CSM 720 and powered by a regulated Duralite at 5.1 volts. Yesterday, the first flight in about 6 weeks, I took off into a hover and noticed the tail was twitching to the right. That was not present the last time I flew. I decided to just do some hovering manoeuvres to get back into the swing of things finishing off with a pirouette at about 20 feet. I noticed the stop was very sloppy so decided to bring it back for examination.

On the way down it yawed massively to the left but I managed to correct it just before landing. Unfortunately, in my haste to get the heli down I clipped the tail rotor on the ground and watched the blades explode nicely in front of me! (Stripped the tail rotor gear box in the process)!

On examination, it looks like the gears stripped in the servo because I can turn the servo wheel with no resistance. But, when I power up the servo there's resistance but the action is very jerky.

Has anyone else had a similar experience?

Alan
http://heliweb.co.uk
Raptor 90, YS 91 ST4, MP2. What a blast!
07-28-2008 02:13 PM
HOMEPAGE  
 
 
AlanR8
Key Veteran
Location: Saddleworth near Manchester (UK)

Update

Wow! I'm impressed with MacGregor Industries (UK JR distributors). I sent the servo back in the first class post Monday and it came back to me today, Wednesday! Yes they found a stripped gear and fixed it without charge.

How good is that!

Also went over to Fast Lads new shop in Barnsley to pick up a few bits and pieces yesterday. Very impressed. Well laid out and well stocked.

Alan
http://heliweb.co.uk
Raptor 90, YS 91 ST4, MP2. What a blast!
07-30-2008 12:24 PM
HOMEPAGE  
 
 
9387ASH
Elite Veteran
Location: UK

Glad to see that MacG's are keeping up the good work !!

07-31-2008 06:53 PM
 
 
AlanR8
Key Veteran
Location: Saddleworth near Manchester (UK)

Hmm......

A similar time scale since the last flight.

I reassembled the VMax and today went through the CSM set up procedure. (I had flown the VMax for about 30 seconds some six weeks ago and noticed a looseness again in the tail so had stopped).

Time marches on, until today. Thorough pre-flight checks and the YS 91 fired first time. (Just love that engine).

Into a hover and again the looseness was there in the tail. Next I knew I had no tail control and before I could react the VMax was eating dirt! Fortunately I hit throttle hold before it hit the deck so the impact was softer than it could have been.

Main blades, boom, feathering spindle, probably main shaft and the Quick UK battery holder.

I've lost TOTAL confidence in the JR 8900G servo and CSM 720 gyro so they're being taken off and I'll revert back to my previous Futaba set up.

Issue is that this weekend the weather is GREAT here in Manchester, UK, and apart from the TRex 450 I've nothing to fly!

Bug*er

Alan
http://heliweb.co.uk
Raptor 90, YS 91 ST4, MP2. What a blast!
09-20-2008 07:35 PM
HOMEPAGE  
 
 
Sky Dancer
Heliman
Location: San Antonio, Texas USA

Sorry to hear about your accidents. Does your servo (JR8900G) still work since the accident? It sounds suspiciously like something besides your servo may be causing the problem.

Keep your rotor speed up!
09-20-2008 10:35 PM
 
 
AlanR8
Key Veteran
Location: Saddleworth near Manchester (UK)

That's debatable Sky Dancer.

We linked the servo directly to the RX and couldn't get a response at the field so I suspect the main culprit is again the servo.

JR "fixed" the stripped gear but we suspect the "pot" needs replacing as well.

No way I'm flying that servo gyro combo again....

Alan
http://heliweb.co.uk
Raptor 90, YS 91 ST4, MP2. What a blast!
09-20-2008 11:39 PM
HOMEPAGE  
 
 
Sam2b
Key Veteran
Location: Seattle, WA - USA

Quote 
On examination, it looks like the gears stripped in the servo because I can turn the servo wheel with no resistance. But, when I power up the servo there's resistance but the action is very jerky.
Has anyone else had a similar experience?

Yes, I noticed this servo normally has no resistance without power applied. That is just the gear ratio inside, and not an issue. I like to test servos (especially after a crash) by using my finger to apply moderate resistance on the servo while moving it slowly with the transmitter. If there is clicking or a jerky experience, then some gear teeth may be damaged, or the servo pot is damaged.

_Sam B_
09-21-2008 01:18 AM
HOMEPAGE  
 
 
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Ace Hobby . Esprit Model . Thunder Power RC

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Radio - Servo - Gyro - Gov - Batt > JR 8900G Tail servo
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