JR8717 servo on tail?

[Chigoe]

Would a JR8717 servo work on the tail 700e DFC? I see it says cyclic but.........any guinea pigs gone first?


JR - JRPS8717 - DS8717 Ultra Speed Cyclic Servo

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

[K2Freak]

It will work, but it isn't the best choice.

Tail rotor servos are all about quick response. While the 8717 is in general an excellent combination of power and speed (and was at the top of the heap for cyclic servos in it's day), it is not a special purpose tail rotor servo and is slower than even a mid-range tail servo of the current generation. It's also 3-4 times as strong - power that is not required to move a tail rotor pitch slider and hence useless and wasted.

Not that you shouldn't try it out - it's not going to hurt anything (if you set the FBL correctly for it!) - but I suspect that your FBL controller may not operate up to it's potential. Servos that are 760us and .04/60 or faster work better...

[DCflyer]

Originally Posted by K2Freak

It will work, but it isn't the best choice.

Tail rotor servos are all about quick response. While the 8717 is in general an excellent combination of power and speed (and was at the top of the heap for cyclic servos in it's day), it is not a special purpose tail rotor servo and is slower than even a mid-range tail servo of the current generation. It's also 3-4 times as strong - power that is not required to move a tail rotor pitch slider and hence useless and wasted.

Not that you shouldn't try it out - it's not going to hurt anything (if you set the FBL correctly for it!) - but I suspect that your FBL controller may not operate up to it's potential. Servos that are 760us and .04/60 or faster work better...

Dead on. You could sport fly with it and do basic moves, but if its really windy or you're throwing it around, you will likely get tail blowouts because the slower speed of a cyclic servo will not be able to keep up. I'd also go with a dedicated tail servo.

[Ah Clem]

I agree with those above who stated that the 8717 is a less than ideal choice for a tail servo.

The JR 8900G works very well on rudder for 500 through 700 sized machines.

I have started to use the new SPG01, which is even better:

Dimensions: 27 x 21 x 41 (1.06x.82x1.61 in)
Weight: 53g (1.86oz)
Torque (kg/cm): 4.8V/41
Speed (sec/60°): 0.05
Torque (kg/cm): 7.4V/63
Speed (sec/60°): 0.03

[el guapo]

I don't think the spg01 will fit on the trex700e. That qrs plug is in the way. The tail servo has to fit in that bracket. I got a set of the JR cyclic servos sls01. And I test fit it in that bracket and it's going to need a lot of dremel work to fit it. that plug is becoming a big challenge.

[ticedoff8]

I agree with the comments from DCflyer and K2Freak.

Take a look at the BK Servo DS-7005HV - I use these on my 700N and 600E tails.
It is a mini servo with standard sized mounting lugs. It fits in a standard servo's opening.

BK Servo Multi Size Digital Tail Servo Model 7005HV
Operation Voltage: 6V – 8.4V
Weight: 50g (1.7 Oz)
Torque:
8.4 kg/cm (116.7 oz/in) @ 6V | 9.6 kg/cm (133.3 oz/in) @ 7.4V | 10.6 kg/cm (147.2 oz/in) @ 8.4V
Speed:
0.035 sec/60 @ 6V | 0.032 sec/60 @ 7.4V | 0.03 sec/60 @ 8.4V
Dimensions: 15x36x35.5 mm
Frequency: 760us/333 hz
Gear Type: Metal
Motor Type: Coreless MAP Price: $90.00 USD | 88 EUR

[haha]

I've never used the 8717 but I've used the 8717HV on the tail of my trex 700 nitro before. I was using the jr8900 to hold the 800 boom on a 700 nitro swinging 710 and 110mm but the jr8900 couldnt do the job so I replaced it a jr8717HV. Needless to say, the jr 8717HV was holding really well so if you want to use the jr8717 for the tail? I say go for it.