Servo rating info

[AdMiller86]

Needing to replace the servo on my Axial Ryft. Went to Amazon to get an idea of the cost for a new replacement. It came with a spektrum s614s, there are several different spektrum servos on there and many other brands and I’m seeing a lot of “kg” ratings. What exactly the kg rating mean? Thanks for the helpful info.

 

[DavidB1126]

Kg is short for kilograms. It's used to determine how much torque the servo can produce.
I use this servo in my 1/10 bashers. pretty nice servo. Not sure if it would be fast enough for a rock bouncer.
https://www.rcmart.com/omg-high-vol...vo-for-1-10-rc-buggy-omg-st-20dm-pro-00111582
torque can also be calculated with oz-in (ounce inches)
https://www.rccarstars.com/rc-maint...ce specification is,force the servo can exert.

 

[AdMiller86]

Kg is short for kilograms. It's used to determine how much torque the servo can produce.
I use this servo in my 1/10 bashers. pretty nice servo. Not sure if it would be fast enough for a rock bouncer.
https://www.rcmart.com/omg-high-vol...vo-for-1-10-rc-buggy-omg-st-20dm-pro-00111582
torque can also be calculated with oz-in (ounce inches)
https://www.rccarstars.com/rc-maintenance-blog/understanding-rc-servo-torque-ratings#:~:text=This torque force specification is,force the servo can exert.

Thanks for the info

 

[bill_delong]

Torque ratings advertised on servos are about as reliable as the C ratings advertised for batteries.

It pretty much takes trial and error and word of mouth for people to locate decent servos for the price where generally you "get what you pay for".

The lowest price servo I would recommend is this one here with the understanding that the gears will need to be replaced about once a year:
https://www.amazon.com/PDI-HV7232MG-Coreless-Aluminium-Standard-Helicopter/dp/B08R9FL5DP/

more background on JX servos here: https://www.rctech.net/forum/showpost.php?p=15403144&postcount=6

The following are far higher quality servos that I have never had to replace any gears and have lasted many years so far:

• https://shopjtp.com/products/ct2-servo
• https://www.teamtrinity.com/high-torque-digital-servo-.html

I've ran close to a dozen different brands of servos, many of them name brands where all of them have disappointed me except for these 3 brands I've listed here. I need to disclose that I am sponsored with Trinity, but I wouldn't support a brand that didn't work well for me

 

[tntpoof]

I've never had issues with quality servo kg rates or speed and certainly not sweep.cheap china brands sure

 

[bill_delong]

Main problem with the torque ratings is that many are reporting the "stall" rating which is useless, you want a rating that can actually lift the load, here's an example of some testing I did with "Cheap China Brands", though these tests are only good for short term, none of these servos will stand the test of time:

 

[tntpoof]

dint I say cheap china brands .YES I did

 

[bill_delong]

dint I say cheap china brands .YES I did

SAVOX is not considered a cheap china brand in fact they are 3 times the price but definitely didn't last as long as the cheap china brands I tested.

JX will tend to go through gears which cost about $10 to replace once a year, SAVOX would tend to blow a circuit board after 2 years making it far more expensive in the long run to maintain

JX gets my vote for a compromise between cost/durability and longevity, they are a cheap china brand that I would recommend

 

[bill_delong]

Here's a rep from AMR servos corroborating my statement above on false torque ratings:
https://www.rctech.net/forum/showpost.php?p=16010012&postcount=445

Regardless where it's made we've tested servos from Taiwan that were advertised as 47kg at 7.4v, and only tested at 28kg. Most servos sold online like Amazon, etc..that are 25kg coming from either market is rarely going to test at 35kg or 45kg that they advertise. We tested 1 brand of servos 25kg, 35kg, and 45kg, and the 35kg, and 45kg tested the same as the 25kg at 7.4v. You will find good ones in Taiwan, and China, but also really bad ones. It's just really going to come down to the integrity of the factory producing servos, as well as the 3rd parties purchasing from them. Just cause someone notices a difference between one servo from another, and the difference is positive does not mean what they actually purchased is performing as advertised. It's good to have an opinion that your experience with whatever brand you purchased is positive, but in the end it's like a car doing a butt dyno test, it's just an opinion..without a dyno it's just a feeling.

 

[Greywolf74]

JX are decent for the price but Savox perform better, even if they are more expensive in the long run. The majority of servos I run are Savox. I've had very few problems out of my Savoxs. Granted I'm sure I dont put the run time on my RCs that you do and I almost always go somewhat overkill on what I need on a servo so it doesn't have to work as hard. Just my .02

 

[bill_delong]

JX are decent for the price but Savox perform better, even if they are more expensive in the long run.

You can't compare an entire brand because I proved in the following video that JX was able to perform better and for less than half the price of SAVOX where JX would prove to be quieter, more efficient with lower temps under load and faster on HV with more torque:

To be fair, a better comparison would be with a SAVOX 2290 instead of a SAVOX 1258 but I just wanted to give an example where a blanket statement that an entire brand of servos isn't going to be better than another brand of servos.

When I first got into racing, I used to believe other racers in that SAVOX was "the best brand of servo to race with" but over time I've been burned enough times by SAVOX to change my views and I now stay away from SAVOX because they are overpriced and over rated

If I'm gonna spend top dollar then I would buy Trinity or NitroPro servos today, check out the warranty on NitroPro here:
https://www.nitroproracing.com/customer-service-1

There's no BS with NitroPro, they stand by their products unlike SAVOX who has ripped me off when I tried to make a warranty claim with too many exclusions in their "fine print":
https://www.savoxusa.com/pages/warranty-information

 

[Greywolf74]

Fair enough. I made my statement based on my own personal anecdotal evidence because I own both brands. I havent done any actual testing just personal observation so you could be right.

I've never heard of NitroPro and I've never used Trinity servos. How do those compare to Hitec? Hitec is generally what I buy if I want something better quality than Savox.

 

[bill_delong]

Honestly, I haven't "bench tested" NitroPro or Trinity to verify stated specs, but I have been running them for many years in my 1/8 cars to have extremely high confidence in both brands.

I haven't published videos on my YouTube channel for many years either, I lost interest... plus I've been super busy traveling and recently doing a major home renovation project.

I never owned a HiTEC servo, but never heard anyone complain about them either

 

[ahr43]

Needing to replace the servo on my Axial Ryft. Went to Amazon to get an idea of the cost for a new replacement. It came with a spektrum s614s, there are several different spektrum servos on there and many other brands and I’m seeing a lot of “kg” ratings. What exactly the kg rating mean? Thanks for the helpful info.

Hey AdMil, welcome to the forum.

That S614 comes in at a rated 201.4 oz-in. torque at 6.0V. 14.5kg-cm torque equivalent in metric measure. I'd use that as a starting point for a comparison purchase. The S614 has a 23T (23 tooth) spline. Important to know when considering a purchase.

Standard servo my RCs use is the ProTek RC 100T. Rating is advertised as 216oz-in 6v and 173oz-in 4.8v. However, it has an industry standard 25T spline shaft for the servo horn. So, without changing your servo horn will not work for your application. Only using it as an example in selecting a servo. What I generally do is take the average torque values between 4.8v and 6.0v. In this case, 194.5oz-in. I feel that better represents what the servo will actually deliver in useable torque.

Hope this helps. Good luck. Cheers. 'AC'