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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › 8717HV vs regular voltage 8717 servos
12-15-2013 02:56 AM  5 years ago
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Scott1115

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Greenwich, CT

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8717HV vs regular voltage 8717 servos
When JR offers two versions of the same servo (HV and non-HV), what is the difference? What is different that one can handle more voltage than the other?

I know many have run the standard 8717's under HV circumstances without ill-effects. Sooner or later I imagine that this will cause a failure but I do not know what, inside the servo will fail.
Compass 7HV, Trex 550E
RCRCC
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12-15-2013 03:30 AM  5 years ago
rpat

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Weirton, W. Va.

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I am running my 8717's with a life pack and have been running them for about 4 years this way with no ill effect. I don't know how they would hold up with a 2 cell lipo?trex 700fbl cal30,minititan,, trx600fbl,trex250,logo 500,Velocity N2
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12-15-2013 12:35 PM  5 years ago
Jeff polisena

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westpalmbeachflorida usa

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I've ran all my 8717s on 2S and never lost one to voltage . Binding ,crashing or wrong mechanical setup will burn them out . Heat dissipation is the difference .I stole it ,flew it and gave it back ;)
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12-15-2013 04:05 PM  5 years ago
Ronald Thomas

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Gainesville, Fl, USA

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I have run 8717s at 8v (direct 2s) as well with no issues.Team MikadoUSA 480XXTreme, 550SX, 600SX, 700XXTreme, 800XXTreme!!
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12-15-2013 05:03 PM  5 years ago
VinceY

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Newnan GA

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I've been doing the same for years. I'm still curious about what the OP asked. What is different about the servos beside the price?Team Synergy/ Rail Blades
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12-15-2013 05:40 PM  5 years ago
gbeeu

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BC, Canada

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In all my helis except for the one Align 500 I once had, I have used JR 8717 servos in regular voltage applications and JR 8917 for HV applications. I am building a LOGO SX and will use the 8917s in it. I guess it is the factory voltage ratings and staying within them for piece of mind that drives me to do that.

If you look at the specs below there is not much different in the three with the Torque being the biggest change. The 8917s bought in a bundle are a few bucks more than the 8717s but is worth it to me for the piece of mind I get.

8717 Specs

Application: Cyclic for 600 size and larger electric and glow
Bearing: Dual
Bushing Or Bearing: Bearing
Gear Type: Metal
Height: 1.57 in
Length: 1.59 in
Servo Type: Digital
Servo Voltage: 4.8 - 6.0V
Size Category: Standard
Speed: .09 sec/60° @ 4.8V; .07 sec/60° @ 6V
Speed (at 4.8V): .05 - .09 sec
Torque: 160 oz-in @ 4.8V; 196 oz-in @ 6V
Torque (at 4.8V): 100 - 199 oz-in
Weight: 2.36 oz
Width: 0.83 in

8717 HV Specs

Application: 50-size and larger helis cyclic
Bearing: Dual
Bushing Or Bearing: Bearing
Deadband: Less than .001ms
Gear Material: SuperSteel™
Gear Type: Metal
Height: 1.57 in
Length: 1.58 in
Motor Type: Coreless
Servo Type: Digital
Servo Voltage: 6.0 - 7.4V (High Voltage)
Size Category: Standard
Speed: .06 sec/60° @ 7.4V
Speed (at 4.8V): .05 - .09 sec
Torque: 230 oz-in (16.5 kg-cm) @ 7.4V
Torque (at 4.8V): 200 + oz-in
Weight: 2.6 oz
Width: 0.82 in

8917 High Voltage Specs

Application: 50-size and larger helis cyclic
Bearing: Dual
Bushing Or Bearing: Bearing
Deadband: Less than .001ms
Gear Material: SuperSteel™
Gear Type: Metal
Height: 1.56 in
Length: 1.58 in
Motor Type: Coreless
Servo Type: Digital
Servo Voltage: 6.0 - 7.4V (High Voltage)
Size Category: Standard
Speed: .06 sec° @ 7.4V
Speed (at 4.8V): .05 - .09 sec
Torque: 220 oz-in @ 7.4V
Torque (at 4.8V): 200 + oz-in
Weight: 2.5 oz
Width: 0.82 in
Logo 690 SX, Logo 600, Titan 50SE Astar
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12-15-2013 10:39 PM  5 years ago
ticedoff8

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Morgan Hill, CA. USA

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Anyone who uses 6v rated servos (like the JR DS8717) on straight LiPo is looking for a "Remember Roman" moment.

That is why they are now designing servos to run on straight LiPo voltages and giving them the designation "HV"

Servos running at the wrong voltages don't always fail at power up. They can fail at any time and any second. Then, you kill someone.
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12-16-2013 08:51 AM  5 years ago
Jeff polisena

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westpalmbeachflorida usa

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But yet it's ok to put crappy quality helis ,parts ,not have a clue how to build or fly in the air . I think you take a chance no matter what you do or use .

I've never had a servo failure come close to hurting someone but have seen many pilots flying careless in scary situations .
I stole it ,flew it and gave it back ;)
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12-16-2013 01:58 PM  5 years ago
VinceY

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Newnan GA

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ticedoff, thanks for the editorial That added absolutely nothing to this thread.Team Synergy/ Rail Blades
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12-16-2013 02:45 PM  5 years ago
Richardmid1

rrProfessor

Leeds, England

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A 6v rated servo will be fine all day long at a regulated 7.4v as this is not far off what a 6v NiMh pack would be fully charged.

A dedicated HV servo can run direct off 2s Li-po which can be upto 8.4v when fully charged and can run no problem regulated to 9v (see the Scott Grey Reactor HVX regulators).

So can a 6v rated servo run off straight li-po voltage (upto 8.4v)? I say yes but with reduced service life and generally a servo will show signs of failing before it stops altogether and its upto the user to check the servos on pre-flight and post-flight checks.
60% of the time, it works every time!
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12-16-2013 04:12 PM  5 years ago
ticedoff8

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Morgan Hill, CA. USA

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ticedoff, thanks for the editorial That added absolutely nothing to this thread.
Thanks Vince.
Its what I do.
Similar to your comment.
We must be from the same mold.
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12-16-2013 05:01 PM  5 years ago
VinceY

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Newnan GA

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Whatever. If anyone can tell us about the components of these servos and how they might differ, I'd love to learn about it.Team Synergy/ Rail Blades
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12-16-2013 05:06 PM  5 years ago
VinceY

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Newnan GA

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And to the others that posted on this thread, I apologize for letting a troll bait me into a response. I usually ignore that kind of crap, but it seemed especially inflammatory.Team Synergy/ Rail Blades
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12-17-2013 01:01 AM  5 years ago
rpat

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Weirton, W. Va.

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yea , I was just about to get out the old pop corn maker, but it sounds like you two kissed and made up.trex 700fbl cal30,minititan,, trx600fbl,trex250,logo 500,Velocity N2
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12-17-2013 03:19 AM  5 years ago
LaDon

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Fort Dodge .Ia

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We are using the 8717hv in one rush heli and have 8717 non hv in the other rush. We notice no difference in the way the heli flies. We are using bec pros in both helis and have one set up on 7.4 volts and the other set up on 6 volts. Like I say no difference in how the helis fly. Basically it boils down to if you are going to use a 2s lipo direct or a bec. If you use the bec then the regular ones will work great and will save you a bunch of money. If money is not an object then get the 8717hv servos. Basically it boils down to what you want to spend.
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