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HelicopterMain Discussion › 8700 with PPM RX
04-23-2002 10:32 PM  15 years agoPost 1
slammers

rrApprentice

Delta, BC

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The box for my JR 8700G servo indicates it must be used with a PCM receiver. I am assuming this is due to interference problems caused by the servo.

Has anyone tried or currently is using this servo with a PPM RX? I am curious if anyone has experienced problems with this combination.

Thanks

Shawn

Free Flight Log Software
www.lammers.ca/FlightLog

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04-28-2002 05:54 PM  15 years agoPost 2
slammers

rrApprentice

Delta, BC

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Anyone???

Free Flight Log Software
www.lammers.ca/FlightLog

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05-02-2002 06:25 AM  15 years agoPost 3
Safe_Cracker

rrKey Veteran

Chicago, IL

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Yes!!!

Finally someone else with the same problem but not remembering a note saying pcm only.It is awefull.All of my servos glitch because of the 8700g coupled with my CSM (ICG540)hh gyro.I'm working on a way to kill the feedback with some type of filter.By the way my receiver is a jr 549 9ch fm receiver.What is your combo?

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05-02-2002 01:52 PM  15 years agoPost 4
Michigan PI

rrApprentice

St Clair Shores, MI

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Way back when...
When the 8700g was released to John Q. Public, there was no sticker on the case. After many people complained about the glitching when using PPM, JR looked into it and promptly resolved the issue by applying the PCM USE ONLY sticker. You can however use the servo in PPM mode IF it is directly plugged into the reciever and not down-line from a gyro.
It is a great servo, super precise and fast. You must remove all forms of binding and/or resistance in your tail linkage or it will fry in short order. Also, I would not reccommend running it with a boom mount and unsupported carbon rod for a couple reasons.

1) Boom mounting (or rear mounting on an aftermarket plate) places the servo in an environment of MUCH higher vibration than the stock forward mounting. The MA rear mount kit for the Xcell is a little better with the damper rubbers but IMO is still a higher vibe environment than up front.

2) An unsupported carbon pushrod, although free of any resistance, is not free of resonance and vibration. These vibes will wear out the servo MUCH faster than a supported linkage. MA has a nice pushrod kit with supports that minimize the resonance but can be just as much a P.I.T.A. to set up smooth as a stock linkage wire.

3) It's a dirty environment back there with the exhaust flowing everywhere.

4) In many instances, a servo extension must be used to connect the servo to the amp. I like the K.I.S.S. method and believe that the more connections you have, the more chances of failure you have.

I used to throw a rear servo on everything I owned. I noticed that I was experiencing servo failures and excessive gear wear. When I would change the gears on my Futaba 9203 and 9205 servos (@$60 a pop) I would find them dirty and oily inside. I have yet to have a tr servo failure or have had to replace the gears on a forward mounted tr servo.
Also, Panos and I spoke with CY last year at Toledo. Panos asked why he (CY) was not running a boom ounted servo and CY's reply was close to what I just mentioned above. Very sound advice from someone who has forgotten more about helicopters than most of us will ever learn.

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05-02-2002 02:17 PM  15 years agoPost 5
Michigan PI

rrApprentice

St Clair Shores, MI

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Hi Dave,
If I remember right, weren't you one of the first to also have PPM problems with the 8700g? Kind of an 8700g pioneer!

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05-02-2002 02:44 PM  15 years agoPost 6
slammers

rrApprentice

Delta, BC

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I have been using this servo with a Arcamax Gyro and a Futaba PPM receiver. It is a new machine and have only been hovering it so far to break in the engine. I have not had one single glitch yet.

I have not had the heli very far away so this may be why I have had some success with this combo. Perhaps I will heed your warnings and swap it with one of my 2700s that is in a PCM machine.

Thanks

Shawn

Free Flight Log Software
www.lammers.ca/FlightLog

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05-02-2002 02:52 PM  15 years agoPost 7
sebastianforbes

rrApprentice

the wallops, hampshire, england

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jeff dickison

hi there,

are you saying that if i was to get a super servo like jr ds810g(with my csm 400), then i should do a straight swop in the raptor 30 and keep the stock tail linkage to the front ?

by the way, what sort of flight times should i get on my o.s. 32 - at the moment i get just over 10-12 mins in the hover. is this running too rich ?

keep up the good work and

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05-02-2002 02:57 PM  15 years agoPost 8
Michigan PI

rrApprentice

St Clair Shores, MI

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Yes, I suggest keeping it up front. With minimal work, the linkage can be made exceptionally smooth and slop free.
Your flight times may seem a little short but it depends on the fuel, exhaust, and type of flying you are doing.
If you were running 5% or 10% nitro and a tuned pipe running at 1600rpm, doing just sport flying with no aerobatics, I would be looking more toward the 20 min mark.

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05-03-2002 05:38 AM  15 years agoPost 9
Safe_Cracker

rrKey Veteran

Chicago, IL

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Thanks.

Thanks for the tips guys.Oh one other thing, It still glitches even if I change the servo.There has to be a cure WITHOUT changing rx's.It has to do with the frame rate of the ICG 540 causing some type of feedback or em field.I do like the idea of keeping the servo off the tail, it makes sense.I was just about to purchase the Quick tail servo mount now I will reconsider.

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HelicopterMain Discussion › 8700 with PPM RX
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