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HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › 8700G service / main gear question.
02-07-2006 12:41 AM  12 years agoPost 1
Yug

rrMaster

UK. Herts

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I've just stripped my tail servo for a regular inspection and clean.
Luckily, not too much oil present
I noticed the main output gear has a substantial amount of wear in its mid position. Just wondering if it is time to replace the gear;
It's had about 400 flights.
here's a couple of pics.....

It can be clearly seen that the teeth that have most use are warn.

Now then, it occurrs to me that if I were to cut off the anti-rotation pin, then I could reinstall the gear the other way round, and utilise the unused (new) teeth. OK in the event of a crash, the chances are that the servo pot will be nackered due to the lack of protection from the anti-rotation pin. But then thats the least of my worries.

Thoughts ?

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02-07-2006 01:07 AM  12 years agoPost 2
Yug

rrMaster

UK. Herts

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Naah bollocks, I think I've answered my own question. I'll drill out the other side and bung a new pin in. At least it will tighten up the slop that has developed. I've been doing loads of tweeks to the tail setup just lately. This is just another loop in the path to perfection.

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02-07-2006 10:47 AM  12 years agoPost 3
Yug

rrMaster

UK. Herts

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We'll the pin came out fine, so I drilled another hole in the other side. Then proceeded to drop the pin and can't find it. Instead, I epoxied a small screw and it works just fine.....

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02-07-2006 12:28 PM  12 years agoPost 4
nivlek

rrProfessor

Norfolk England

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Come on Guy , it's only £27.95 for a new gear .

At the end of the day , it gets dark .

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02-07-2006 12:49 PM  12 years agoPost 5
Yug

rrMaster

UK. Herts

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I know, I've already got spares. It seemed a shame that just a few teeth were being used. I now have a brand new set of teeth for nothing.
I'm also getting tired of the rip-off cost of heli parts, so if I can engineer my own fixes, then great. Bloody hell, £27 for a gear that costs pence to manufacture.

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02-07-2006 02:02 PM  12 years agoPost 6
reddragon

rrElite Veteran

Brooklyn, N.Y.

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Come on Lad. Just put the new gear in. It could save you hundreds of pounds in the long run!

Wayne - Fly it like you stole it! You're in good hands with Runryder!

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02-07-2006 02:08 PM  12 years agoPost 7
Yug

rrMaster

UK. Herts

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Too late. 'Tis all back together and runs as smooth as a babys bottom.

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02-07-2006 02:13 PM  12 years agoPost 8
reddragon

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Brooklyn, N.Y.

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Good Luck!!

Wayne - Fly it like you stole it! You're in good hands with Runryder!

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02-07-2006 02:29 PM  12 years agoPost 9
Yug

rrMaster

UK. Herts

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Actually something I just want to add, I was rather supprised how easily the old pin came out. I think it was firm enough to have been safe, but if it had come out, then it may well have jammed up the gears. My new pin is screwed and epoxyed in.

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02-07-2006 05:21 PM  12 years agoPost 10
Patriot

rrVeteran

Luton

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I can't see the problem with doing this mod, the pin does not come into play unless you move the servo from end stop to end stop by hand or have a sudden impact. Good job well done.

Just smile

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02-07-2006 09:00 PM  12 years agoPost 11
DOKEY

rrProfessor

Northamptonshire UK

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My 8700g gears were just like that, it's surprising how quick they do wear.
Quick 180 of the gear and all is well

Ryan.

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02-07-2006 09:39 PM  12 years agoPost 12
Yug

rrMaster

UK. Herts

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DOKEY - do you re-pin it ?

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02-08-2006 01:10 AM  12 years agoPost 13
Dr.Ben

rrMaster

Richmond, VA, USA

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Good idea on the gear turn around, but I'm thinking that a t/r servo with 400 flights on it might be up from a change out. That's a lot of time. A new servo would surely be cheaper than the crash it would cause when it dies.

Ben Minor

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02-08-2006 06:50 AM  12 years agoPost 14
Yug

rrMaster

UK. Herts

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How long do these servos normally last ?
Infact, I've never had a servo failure.

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02-08-2006 07:06 AM  12 years agoPost 15
DOKEY

rrProfessor

Northamptonshire UK

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TBH guy, this was like 3 - 4 seasons ago, and I do not remember seeing a pin. If I had seen a pin I doubt I would of messed around as I had a new set of gears there, but at the same time, I still have the new set of gears and I know I did not drill the gear.

So I think I will have to say that I installed the gear with no pin in the gear
(never paid attention at school, so paying attention to a servo maybe on the extreme side )

Ryan.

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02-08-2006 11:46 PM  12 years agoPost 16
Dr.Ben

rrMaster

Richmond, VA, USA

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Guy,

Part of the problem is that these servo DO last for so long, and it tempts you to run them until they drop. Then your model drops into the ground. I personally pull servos after 1.5-2 seasons of flight or about 50 gallons. Go price a set of cyclic servo plus the rudder and compare that to the cost of a WOT crash. It's just not worth the chance. Also, you don't realize the effect of gradually servo wear and tear on the way your model flies until you get the new servos in there and compare the difference. These points are especially true in lagre 60-91 sized models which are obviously more demanding of servos.

I've sent t/r servos with 25+ gallons in for service several times that appeared to be working fine. In a few cases they flunked the motor test that Hobbico uses that assesses torque and speed. What that told me was that servos can be going south long before they give up the ghost completely.

Ben Minor

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02-09-2006 12:01 AM  12 years agoPost 17
Yug

rrMaster

UK. Herts

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Dr.Ben - thanks for that, you've given me an idea. I have a nearly new 8700G on another heli so it will give me something to compare my well used one against. I suppose the right thing to do is design a servo tester to monitor speed, torque and gear slack. Should be pretty straight forward using a linear distance measuring transducer connected to a scope. Can hang weights on it to check torque performance as well. Thanks for the idea

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HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › 8700G service / main gear question.
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