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Model Rectifier Corp . PowerHelis . JR-Spektrum

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Radio - JR & Spektrum DSM > 8717 temps?
 
 
creightoncarr
Veteran
Location: Missouri City, Texas - USA

For those running the 8717's at 8v what temps are you seeing after hard flights. I never really paid attention today but after a couple of flights I measured the temp on the heat sink at around 120 degrees F. Not so hot you can't keep your finger on them indefinitely, but pretty warm. Is that pretty typical?
06-16-2008 04:33 AM
 
 
Slartybartfast
Senior Heliman
Location: Somewhere in England

Seeing as they were designed for 4.8V, what do you expect them to do if you run on 8V ?
06-16-2008 09:09 PM
 
 
creightoncarr
Veteran
Location: Missouri City, Texas - USA

Thanks genius - if I knew do you think I'd ask?

BTW, they are also rated to run off 6v packs, which when fully charged put out 7.5v, not that far off from the 8.4v of a fully charged 2S lipo.
06-16-2008 09:58 PM
 
 
Chris Lupa
Key Veteran
Location: Sonning, Reading UK

Quote 
Seeing as they were designed for 4.8V, what do you expect them to do if you run on 8V ?
They are rated at 6V aswell as 4.8v and, to be honest, were designed to handle even higher voltages. A lot of the top dogs are running them at 8V with, what seems to have, no bad tendancies. I can't be sure exactly but I remember talking to a buddy of mine and he said he was running 100F+ on his 8717s and, as far as I know, hasn't had a problem since. Remember they have a great big metal heat sink case for this sorta thing

Sponsored by CSM and QuickUK
06-16-2008 10:06 PM
HOMEPAGE  
 
 
creightoncarr
Veteran
Location: Missouri City, Texas - USA

Thanks, I've been running them at 8v for awhile now with now problems. I hadn't really paid attention to the servo temps though. Just wondering if what I was seeing is in line with others who are running them this way.
06-16-2008 10:08 PM
 
 
Chris Lupa
Key Veteran
Location: Sonning, Reading UK

I think it's always good to check and make sure you aren’t damaging your equipment. I run the 8717s at a regulated 6.8v so can't comment from personal experience but, from what I've heard, they can get pretty hot running at 8v with minimal problems. Obviously with a voltage as high as 8 will drive the servo a little harder and cause it to heat more but my guess is that's OK with the 8717s – it seems to have been for most others. Hope it all goes well

Sponsored by CSM and QuickUK
06-16-2008 10:15 PM
HOMEPAGE  
 
 
Slartybartfast
Senior Heliman
Location: Somewhere in England

Well now, oddly enough the manufacturer doesn't rate them at 8V. Wonder why that is ?

Just in case, the manufacturer is JR Propo of Japan. And they (JR) emailed the UK importers and the following statement was released...


Quote 
Using DS8915 servos without a voltage regulator
The latest trend in 3D heli flying is to run digital servos via receivers being powered direct from two cell lithium packs. Fresh from charge, this can mean voltages in excess of 8 Volts. In the USA some of the top 3D guys are running DS8717 servos in this manner and appear to get away with it for a short while, although service life is sure to be reduced.
JR have confirmed that the DS8717 is exactly the same servo as the DS8915, re-badged for the US market. However we would strongly recommend NOT running DS8915 servos in this manner as they will not be covered by our warranty. This is also true of other current JR servos, which should also not be run direct from a 2 cell lithium pack. If you wish to use lithium batteries to power your R/C system then please use a good quality regulator at the recommended voltages for the JR servos and gyro being used.
JR were concerned enough about this to issue a short statement, which is reproduced below
“Although JR does not guarantee the DS8915 servo to work at 8.0V, this servo does seem to be workable with 8.0V. But if you use the DS8915 with 8.0V then this will be at your own risk. JR regret that we cannot give our approval for such use.”
Please also note that we will be unable to repair any burnt out DS8717 servos. We will be advising service customers with such servos that they have been sold grey imports and to return them to their supplier for a full refund.

http://www.macgregor.co.uk/Homepage/0608news_6.htm
06-16-2008 11:09 PM
 
 
creightoncarr
Veteran
Location: Missouri City, Texas - USA

That's great, but really, if you want to argue against running the servos at 8v why don't you start your own thread? I understand I am running them at a voltage higher than recommended by the manufacturer. I wasn't asking for approval. I wanted to know what temperatures others living dangerously, like I must be, are seeing.
06-16-2008 11:56 PM
 
 
turboomni
Elite Veteran
Location: 63 Rambler Down By The Dumpster

Then ask JR what temps are good,,, Then you maybe happy

Setup is everything, All my heli's can fly better than I can pilot them
06-17-2008 05:10 AM
 
 
Slartybartfast
Senior Heliman
Location: Somewhere in England

Well, there is hot, damned hot and OH SH!T, I've just burnt the bugger out !

06-17-2008 07:37 PM
 
 
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Radio - JR & Spektrum DSM > 8717 temps?
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