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Old 01-04-2013, 05:25 AM   #1
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Default Servos for 1/10th on-road

Just want to query about Servos for 1/10th on-road as im lookin for High voltage sanwa. One for the steering and throttle.
My querys are:

- Is speed affected by the rate of angle that the servo produces for example
(7.4v servo can produce 0.06 @ 60 degree) if this is correct
is 40 degree faster than 60 degree?

- And is the amount of torque produced from a steering servo can suit varying types of tracks with low to high levels of traction. For example ( 20kg steering servo would be great at high traction track but is not good a low traction track)

Because I myself have not put decent servos in car. As i have come to realise at our last nationals that I was suffering insufficent grip and i couldnt find out why. Till the end of the meet is came down to servos.
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Old 01-04-2013, 06:25 AM   #2
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No, the torque of a servo has nothing to do with the grip. The speed of the servo can be a factor, slow servo's need to be activated before the corner so the steer on time. Once I had driven slow servo's too and I could make good fast laps, going to faster servo's I noticed it was much easier to place the car at any line of the track.

My advise of the specs of the servo's are at least:
- 8kg force
- 0.1 sec speed @ 60 degrees
- metal gear.

60 degrees is a larger distance than 40 degrees so 60 is faster.

I also noticed a transmitter with a high framerate like the Futaba HRS systems and the DX3R with higher framerates does do something as well in the reaction time.

You can calculate some things. The slowest reaction:
speed servo + framerate + latency (delay time)

With the older Spektrum DX3 set and a standard servo:
140ms + 20ms + 11ms - 171ms

With a fast framerate a fast servo and the latest latency
60ms + 5ms + 3ms = 68ms

You think the framerate and latency is not much but with the 20mS difference a 0.08 sec servo on a good transmitter can be as fast as a 0.06 sec servo at a bad transmitter

Again, faster servo's will give a directer steer but it will not change the grip.
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Old 01-04-2013, 02:39 PM   #3
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Quote:
Originally Posted by Roelof View Post
No, the torque of a servo has nothing to do with the grip. The speed of the servo can be a factor, slow servo's need to be activated before the corner so the steer on time. Once I had driven slow servo's too and I could make good fast laps, going to faster servo's I noticed it was much easier to place the car at any line of the track.

My advise of the specs of the servo's are at least:
- 8kg force
- 0.1 sec speed @ 60 degrees
- metal gear.

60 degrees is a larger distance than 40 degrees so 60 is faster.

I also noticed a transmitter with a high framerate like the Futaba HRS systems and the DX3R with higher framerates does do something as well in the reaction time.

You can calculate some things. The slowest reaction:
speed servo + framerate + latency (delay time)

With the older Spektrum DX3 set and a standard servo:
140ms + 20ms + 11ms - 171ms

With a fast framerate a fast servo and the latest latency
60ms + 5ms + 3ms = 68ms

You think the framerate and latency is not much but with the 20mS difference a 0.08 sec servo on a good transmitter can be as fast as a 0.06 sec servo at a bad transmitter

Again, faster servo's will give a directer steer but it will not change the grip.
Thanks for your help Roelof but what im trying to say that in high conditions a steering servo that has low torque specs cannot hold the load
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Old 01-04-2013, 04:19 PM   #4
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Be aware that digital servo's can create more force to hold position than equal analog servo's. And forgot to mention that high framerate systems can only work with digital servo's.

For a few years I am running Savox SC-1257TG servo's on my Mugen MRX4X, the [email protected] and 10kg force are enough. Before that I had KO wit 0.08sec and 8kg, both good servo's, if they work for 1/8 then the will do for sure 1/10.

Cheap high torque servo's are most of the times slow, that can give problems with taking corners. A populair servo amoung starters is the MG995 servo, stay away from it. Although it seems to be a good servo regarding the specs it is not precise and can have some difficulties finding position what will give a strange feeling to drive with.
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