View Full Version : jr servos at 8v-caution
mk1spitfire
07-02-2008, 06:49 PM
http://www.macgregor.co.uk/Homepage/0608news_6.htm
tcast305
07-02-2008, 07:02 PM
I've read what you linked above. However, you have to wonder why JR/Spekturm would release a RX (AR7100 and AR7100r) that uses 2s lipo directly and lists the JR 8717 in the manual as a sample setup in a heli.
Also, I've haven't personally heard reports of 8717's failing at 8v. Maybe support is different from JR in USA vs elsewhere?
Thanks.
Bobbyk
07-02-2008, 07:15 PM
Do you think we are about to see servos rated at 8.0v hit the market soon. The first company to do it and stand by them will make a killing, until others follow suit.
I was not around when the move came from 4.8v to 6v, but I'm sure it was similar.
Robert
Finless
07-02-2008, 09:12 PM
Do you think we are about to see servos rated at 8.0v hit the market soon. The first company to do it and stand by them will make a killing, until others follow suit.
I was not around when the move came from 4.8v to 6v, but I'm sure it was similar.
Robert
YEP... NEW standard trust me.....
Bob
4cyclic
07-02-2008, 09:40 PM
new standard of 8v for tail servos too is needed.
dont worry, Mcgregor say anything about a 4.8v NiCD or NiMH cell will kill ALL JR servos. they write dire life threatening notes on all 8717 (or in the UK, 8715 or 8915) servos not to run anything else but 4.8v
jeznewsome
07-03-2008, 07:16 AM
I started a similar thread in the JR and Spektrum radio section
http://www.helifreak.com/showthread.php?t=80020
I have the 8717 servos and 7100R waiting for the arrival of my 700 kit but have similar reservations about the long term reliability of the servos on 2S Lipo followinf reading the MacGreggor bulletin. In 10 days there has only been a single response, which quite sensibly suggests using a 2S A123 Rx battery (i.e. not requiring a regulator but providing a lower voltage than a Lipo direct from the battery). This would be ideal though my field charger is not LiFE capable and I would worry about getting the LiPo and LiFE mixed up!
Whilst I accept that the norm will hopefully become true 8v capable servos is there evidence from flying fields of any failures of the 8717 on 2S LiPo.
Should I just stop worrying and JFDI?
gadawg58
07-03-2008, 09:11 PM
I started a similar thread in the JR and Spektrum radio section
http://www.helifreak.com/showthread.php?t=80020
I have the 8717 servos and 7100R waiting for the arrival of my 700 kit but have similar reservations about the long term reliability of the servos on 2S Lipo followinf reading the MacGreggor bulletin. In 10 days there has only been a single response, which quite sensibly suggests using a 2S A123 Rx battery (i.e. not requiring a regulator but providing a lower voltage than a Lipo direct from the battery). This would be ideal though my field charger is not LiFE capable and I would worry about getting the LiPo and LiFE mixed up!
Whilst I accept that the norm will hopefully become true 8v capable servos is there evidence from flying fields of any failures of the 8717 on 2S LiPo.
Should I just stop worrying and JFDI?
JFDI! I have 40+ flights on my 8v setup now with 8717's and they are going strong on my Raptor 90se! So Far ..... :)
CatchmyCorsair
07-04-2008, 02:46 PM
Has anyone temp'd the heatsinks on 8V? If they are hot, damage is possible. If not I wouldn't worry. I'll be running 8V. If they get hot I'm going to run 6V from the Spektrum 10A regulator.
jeznewsome
07-04-2008, 05:00 PM
Heat dissipation is an interesting point that got me thinking this morning. The T700 design mounting for the elevator servo sheilds the aluminium heatsink on the 8717 servos withing a servo box/cradle. If there is going to be a heat problem with running at 8V I assume it'll be more likey to affect this 'elevator' servo than the others.
As noted by CatchMyCorsair below it would be interesting to see the relative temps across the swash servos on an 8V system
creightoncarr
07-04-2008, 05:34 PM
They'll get warm if you run them at 8V and fly hard. Every heli I own is set up with 8717's on 8V. Mine come in at about 120 degrees F on the heatsink after each flight. My 600N has well over 150 flights this way and the servos are still running strong.
RE: the AR7100R receiver, I'm not going to repost everything here, but I would suggest reading these threads on the otheRR forum:
http://www.runryder.com/helicopter/t440566p1/
http://www.runryder.com/helicopter/t443309p1/
http://www.runryder.com/helicopter/t439198p1/
sonofcar
07-04-2008, 05:37 PM
I am flying again later on and will give you the temps that mine are.
jeznewsome
07-04-2008, 05:59 PM
Looking forward to further information on temperatures and thanks for the heads up on the AR7100R. Looks like I'll need to get the glue gun out!
CatchmyCorsair
07-04-2008, 06:25 PM
I won't be able to sleep at night after reading those 3 links. :arggg:
I will definitely be adding some glue, thanks. Maybe you should try wrapping it in some thick vibration foam.
I still don't see how the antenna can break off. I'm voting for some thicker wires on the large Rx's. The weight isn't an issue.
creightoncarr
07-04-2008, 06:58 PM
I'm throwing in the towel on the 7100's and going back to the R921's. I've never had an antenna break off from a 2.4GHz receiver until these. And to have it happen on all three of them. Just not worth it in my opinion. Wrapping in foam is sure to help, but personally I would still be worried. Someone at Spektrum needs to go back to Soldering 101.
sonofcar
07-04-2008, 07:19 PM
I'm throwing in the towel on the 7100's and going back to the R921's. I've never had an antenna break off from a 2.4GHz receiver until these. And to have it happen on all three of them. Just not worth it in my opinion. Wrapping in foam is sure to help, but personally I would still be worried. Someone at Spektrum needs to go back to Soldering 101.
Is it on the satilite rec or the main rec or both? this is not good, i'll have to think up a new set up for my 700:dontknowI wonder if bert kammerer has have problems with his. He has been posting on another tread in the 700 page. hope he see's this and gives us info. :confused:
creightoncarr
07-04-2008, 10:42 PM
Just the main receiver. I was told the other day that Marcus Kim determined his crash in Vegas was caused by an antenna coming off his receiver as well. I wasn't there though, so I don't have first hand knowledge of that. Just passing along what I was told.
CatchmyCorsair
07-05-2008, 12:32 AM
Does anyone think thick CA/epoxy around the solder joint and hot glue over that might work better than only hot glue? The hardened CA/epoxy might act like a plastic shield making sure it doesn't vibrate at the joint.
sonofcar
07-05-2008, 10:49 AM
(I haven't had those problems with the antenna or haven't heard of anyone that I fly with having the problem. However, I can see how the antenna would break off if there is too much vibration. Simply keep an eye on the antenna, I'll past that info along to JR, but they're probably aware of it.)bert kammerer
This is what bert kammerer answerd back about this topic. Maybe it was a bad batch. Anyways i save the rec for last on my build, and see what happeneds in the next couple weeks, then decide.
Finless
07-05-2008, 12:14 PM
Mine did come off and I resoldered them myself properly. I think there maybe a few out there that the wire did not get solder flowed in the wire properly when it was attached to the board. I looked at a friend of mines and his is soldered properly. e.g. you can see that solder FLOWED into the wire and the wire is firmly attached.
I would inspect yours for sure!
Also just my thoughts on this and just my opinion..... but the middle board is supported between the top and bottom board by 2 foam pads. This allows the middle board to move a little if you have some vibration. After I soldered mine I then applied hot glue around the antenna AND put some between the middle board and BOTH the top and bottom board at the corner. This should keep that middle board from moving at the antenna in relation to the other 2 boards....
I am going to continue to fly mine now that I know the solder job is correct and we shall see if there are still issues with it breaking off.... I doubt it.
In the end if you inspect yours and find the wire flexes RIGHT at the solder blob on the board, I would send it in. If you can clearly see that the wire has solder that flowed up in it a little, your probably OK.... FYI fixing it yourself probably voids the warranty AND trust me you need a VERY fine soldering iron made for Surface Mount board work!
Bob
chosen69
07-05-2008, 04:31 PM
If it's a bad soldering job putting glue on there is not gonna help in any way, on the other hand if the soldering has been done right you could probably hang your car on it and it wouldn't come off... So just inspect it and as Bob said send it in if there's any doubt in your mind...
CatchmyCorsair
07-05-2008, 06:03 PM
I looked over mine and it's really hard to tell if it's a bad joint or not. They put this tan goop over the joint. I dunno what I'll do. If I send it into Horizon I'll probably get the same thing back.
mk1spitfire
07-05-2008, 06:09 PM
I had issue with a ar7000 reciever aerial, namely that the wire can be exposed once the insulation breaks at the point of entry to the plastic body.
It appears that the aerial insulation will not tolerate much bending or movement.
By applying heat shrink this weekness can be overcome.
Very alarming to read that the aerial can vibrate ittself loose. At least there are 3 more. maybe the heatshrink can aid the problem too.
CatchmyCorsair
07-05-2008, 06:15 PM
I had issue with a ar7000 reciever aerial, namely that the wire can be exposed once the insulation breaks at the point of entry to the plastic body.
It appears that the aerial insulation will not tolerate much bending or movement.
By applying heat shrink this weekness can be overcome.
Very alarming to read that the aerial can vibrate ittself loose. At least there are 3 more. maybe the heatshrink can aid the problem too.
But it looks like they broke right where the insulation stopped, so I don't see that helping at all. :dontknow
mk1spitfire
07-05-2008, 06:24 PM
yer, if it brakes inside the reciever at the soldered joint because of poor soldering there is not much you can do but check. Either open the case, a little gentle tug to give you piece of mind.
However the added insulation will prevent the exposing of the wire by the insulation breaking at the point of entry to the case by means of bending and it will stiffen up the overall joint suley.?