Differences in Servos

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WideOpen

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What is the difference between a throttle servo and a steering servo?
  • My throttle servo is a AVOX SC-0352
  • My steering servo is a AVOX SC-0254
 
Throttle is high torque and steering is high speed usually.
 
I didn't know you could rebuild them.
I think these are what you have, give or take the Metal Gears. With that said, if it is right, take the specs and find one similar or better.
I understand "better" but I don't understand what makes one better or worse?
 
Servos all have different specs, like speed and torque. Faster and stronger are typically better.
 
I didn't know you could rebuild them.

I understand "better" but I don't understand what makes one better or worse?
The servos are all completely different.. you want a high tourqe high speed for steering and a high tourqe for throotle.. the tourqe is measured with IN/OZ and the speed is with .17sec .15sec .13sec.
Digital is better then analog. The higher the tourqe and speed makes it better. Metal gears as well makes it better.. bearings makes it better..
 
What is the difference between a throttle servo and a steering servo?
  • My throttle servo is a AVOX SC-0352
  • My steering servo is a AVOX SC-0254
The difference between throttle servos and steering servos is you need a much higher torque (more powerful) servo to turn your wheels than you need for a throttle/brake. (The throttle servo also usually does braking too.) A throttle servo should have at least 100 oz/in or torque but probably doesn't need more than 150oz/in. That being said it coulod have 500 oz/in and would still work just be a waste since a 500oz/in would be a much better steering servo. imo. A steering servo will have a minimum torque rating youll want for steering depending on the scale and the weight of the kit but there is no real maximum. The higher torque and the faster the better for steering.

If you're asking about the difference between those two specific servos here are the specs.

Savox SC-0352
Specifications:

  • Torque @ 4.8v - 4.2kg/58.3oz-in
  • Torque @ 6v - 6.5kg/90.3oz-in
  • Speed @ 4.8v - 0.14 sec/60 deg
  • Speed @ 6v - 0.11 sec/60 deg
  • Dimensions L x W x H (mm): 40.7 x 20.0 x 39.4
  • Weight: 42.0g
Savox SC-0254MG
Specifications:

  • Torque @ 4.8v - 6.9kg/86.1oz-in
  • Torque @ 6v - 7.2kg/100.0oz-in
  • Speed @ 4.8v - 0.19 sec/60 deg
  • Speed @ 6v - 0.14 sec/60 deg
  • Dimensions L x W x H (mm): 40.7 x 19.6 x 39.4
  • Weight: 49.0g
Now if you dont understand what specs I can break it down for you. Servos have two main specs Torque (power) and speed. A Servos torque and speed are affected by how much voltage they are given. Both of these servos are rated for 4.8v-6v. You really always want to run a servo at the highest V it will take if possible for best performance.

So lets break down torque. if you look at the SC-0245MG You can see @6V it will put out 7.2kg-cm or 100.0oz-in or torque. @4.8v this servo only puts out 6.9kg-cm or 86.1oz/in. kg-cm is the metric measurement and oz-in is the imperial measurement. So 7.2kg-cm is the same as 100oz-in. Kinda like how 1kg is the same as 2.2lbs.

The speed rating works the same in terms of it will be faster the more voltage its given. So @6v the SC-0245MG's speed is 0.14 sec/60 deg which means @6V the output shaft on top will turn 60 degrees in 0.14 seconds. The lower the number the faster the servo. Faster is better.

The only other difference between those two specific servo is the SC-0245MG has metal gears (thats what the MG stands for in the name) and the other servo has plastic gears.

I didn't know you could rebuild them.
Quality servo manufacturers will generally sell rebuild kits for their servos incase the gears/bearings get damaged so you can replace them. You wont generally find rebuild kits for cheap ebay/amazon servos.

I understand "better" but I don't understand what makes one better or worse?
Other than torque/speed there are other factors that can be considered but are often less important for example Analog vs Digital, metal gear vs plastic gear, brushed vs brushless motors inside the servos, and cored vs coreless. Torque and speed are the main concerns, plastic/metal gears is probably second followed closely by analog vs digital. I wouldnt worry about brushed/brushless or cored/coreless. Its nice to have a brushless/coreless servo but as long as it has the specs you want these two dont matter for general bashing purposes.

So basically when I go looking for a servo I generally buy the fastest most powerful servo I can that is metal geared that fits my budget. Digital is a big plus but I think most servos are digital these days. If it happens to be brushless or coreless thats great too but not a concern. Again throttle servos dont have to be super beefy just get one between 100-150oz/in thats metal geared and you'll be fine.

Lemme know if you have any other questions.
 
One thing to note, the "cheap" servos also have a tendency to overshoot and don't center well. This makes them not as precise as a similar spec'd "more expensive" servo.

By overshoot, I mean, you turn your steering wheel full lock really quick, the servo goes to where the radio tells it and beyond a little bit, then goes back a little.

Not centering well means when you turn the wheel, then let go, the servo goes back to home, but a cheap servo tends to either overshoot home or come up short, so your truck doesn't follow a straight line as you would expect.

For bashing, these things don't matter a lot (unless the servo is particularly bad), but for track use, it would make it more frustrating to be competitive.
 
One thing to note, the "cheap" servos also have a tendency to overshoot and don't center well. This makes them not as precise as a similar spec'd "more expensive" servo.

By overshoot, I mean, you turn your steering wheel full lock really quick, the servo goes to where the radio tells it and beyond a little bit, then goes back a little.

Not centering well means when you turn the wheel, then let go, the servo goes back to home, but a cheap servo tends to either overshoot home or come up short, so your truck doesn't follow a straight line as you would expect.

For bashing, these things don't matter a lot (unless the servo is particularly bad), but for track use, it would make it more frustrating to be competitive.
About where is that price break from cheap to good?
 
About where is that price break from cheap to good?
Personally Id say anything that is not a known good brand is generally considered cheap. Hard to say from a "price" stand point. Some manufacturers are worse than others plus the price point is going to change with scale and specs. etc. In Olds's case though I think cheap is more like technically acceptable vs known proven performer.
 
About where is that price break from cheap to good?
The <$50 25KG/35KG ones on amazon come to mind. Some are hit and miss as to accuracy, durability and longevity. The same can be said for any savox/hitec/JR/futaba servo, but the frequency of failure tends to be much less.

I recently got a really nice servo for <$100. A promodeler. They seem to be top notch in quality and performance. I put their ds505blhv in my maxx4s.
2021-1022-promodeler-Servo-DS505BLHV.jpg
 
I know since I came back to the hobby this last time I've been using a lot of high end Savox, Hitec, and Protek servos. They arent cheap by any means but theres definitely a noticeable difference and performance. I'm sure these will last a long time too. I'm still running the same Hitec servo in my OFNA MBX 9.5 that I put in it a dozen years ago or so. Its still running strong.
 

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