Servo and shock information

Welcome to RCTalk

Come join other RC enthusiasts! You'll be able to discuss, share and private message with other members of our community.

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

volare

RC Newbie
Messages
1
Reaction score
1
RC Driving Style
Hey Everyone,

I'm trying to spread the word about a new resource I've built for RC enthusiasts called

Servo Database.

The goal of this project is to have detailed, organized information for every RC servo in existence. (Currently the database has 1,792 servos.) I've always had to spend a lot of time research servos when I build a new project, and I think the Servo Database will make this process much easier.

I've tried to make it easy to quickly view and compare different servos. Some other features of the database include:

  • Advanced search feature to find servos based on any criteria. For example, you could do a search to find all Futaba servos that are digital and have at least 250 oz/in of torque.
  • Ability to sort servos according to any attribute (e.g. fastest to slowest)
  • Servo reviews allow you to discuss and rate each servo.
Here are Hitec Servos. 122 of them!
 
Last edited by a moderator:
Sounds like a pretty helpful idea.
 
Smart idea

Sounds good,Great Idea keep it up
 
Shock Absorbers & Servos


Shock oil and spring rates

Waterproofing a servo

RC-Servo-nocover.jpg


futm0551-gears-2.jpg
 
Here is a link to Servo Database.com, they have most MFG's servo's listed, spec's, prices, and reviews from users.
It's great for comparing servo's spec's without having to jump all over the net to find them.
http://www.servodatabase.com/
 
For the total beginners out there just know that on a nitro rig you will need either 2 or 4 servos (1 throttle, 1 or 2 steering and 1 for reverse depending on the kit). For electrics you generally one need 1 or 2 for steering depending on the rig.

Your standard servo for a 1/10 or 1/8 scale RC will be approx. 40mm long x 20mm wide x 38mm tall. The length and the width may vary a couple mm but not much. The height how ever can very probably anywhere from approx 35 to 45mm. The height really doesn't matter as long as the kit that you're putting it into doesn't have a real confined space. The majority of the kits I've seen can accommodate a 45mm tall servo but measure it to make sure before you buy if it looks like there could potentially be an issue. Some kits it obvious that the height doesn't matter. Others not so much. i recommend Savox brand servos if you can get them. For the money their quality is hard to beat.

There are two other factors to take into consideration when buying a servo (for steering...I'll mention throttle servos separately at the bottom of this post). Torque and speed. torque is represented in oz-in here in the US or kg-cm for the non-oddball parts of the world. Speed is the time in a faction of a second for the servo horn to travel 60 degrees. A common servo for a light 2wd 1/10 scale RC might have specs that look something like whats below. This is the specs on a Savox SC-1258TG.

Dimensions(mm): 40.3x20.2x37.2
Weight(g): 52.4
Speed(@4.8V sec/60): .10
Torque(@4.8V oz-in): 133.3
Speed(@6.0V sec/60): .08
Torque(@6.0V oz-in): 166.6

Gear: Titanium & Aluminum
Bearing: 2BB
Case: Aluminum
25 Tooth Spline
Frequency: 250-333hz
Pulse Width Frequency: 1520

Servos will always have their specs listed at 2 different voltages. Normal servos will be a 4.8V and 6V for 4 or 5 cell NiMH battery packs respectively. High Voltage or HV servos will list 6V and 7.4 V. HV servos are designed to be used either with a 6V NiMH pack or a 2 cell LiPo (also seen written as 2S LiPo and LiPo stands for lithium polymer) which puts out 7.4V nominal voltage. HV servos are most commonly seen in electrics where the kit itself is already running on a 2S LiPo so you dont have to use a BEC (or Battery Elimination Circuit...a device that takes X volts and steps it down to Y volts...in this example 7.4V down to 6V) however some guys like powering their nitros with 2S LiPos for increased run times. Heres an example of some similar specs from a Hitec servo (Hitec is another highly trusted name brand for servos). This one in particular is from the HS-7985MG and it shows not only the oz-in rating but the kg-cm rating as well.

Motor Type: Coreless
Bearing Type: Dual Ball Bearing
Speed (4.8V/6.0V): 0.16 / 0.13
Torque oz./in. (4.8V/6.0V): 144 / 172
Torque kg./cm. (4.8V/6.0V): 10.4 / 12.4

Size in Inches: 1.57 x 0.78 x 1.45
Size in Millimeters: 39.88 x 19.81 x 36.83
Weight ounces: 2.18
Weight grams: 61.80

Probably the last thing you want to know is "How much torque/speed do I need?" Speed isnt all that important unless you are racing but generally the faster the better. The size of the kit will affect whether or not you think a servo is fast enough. This is gonna be a personal preference more than anything. For torque there is some personal preference that plays into it but the heavier the kit the more torque you will want. The problem is of course the more torque you want the more speed you have to give up. Dont get me wrong, you can find servos that are plenty fast in a given torque range (if you're willing to shell out the money for it) but generally as a servo gains torque it will loose speed. The chart below is a rough idea of about what torque range you should look at for each class of RC. This list is strictly my own personal opinion and others opinions may very but it will give you a place to start. Also remember that a good rule of thumb is that it never hurts to have as much torque as you can get as long as you get the speed you are looking for :)

Ranges are approx...
1/10 scale light 2WD: 133oz-in/9.5kg-cm to 180oz-in/14.5kg-cm
1/10 scale heavy 2WD: 166oz-in/13kg-cm to 220oz-in/15.8kg-cm
1/10 scale light 4WD: 166oz-in/13kg-cm to 220oz-in/15.8kg-cm
1/10 scale heavy 4WD: 180oz-in/14.5kg-cm to 300oz-in/21.6 kg-cm

1/8 scale light 2WD: 166oz-in/13kg-cm to 220oz-in/15.8kg-cm
1/8 scale heavy 2WD: 180oz-in/14.5kg-cm to 280oz-in/20.1 kg-cm
1/8 scale light 4WD: 180oz-in/14.5kg-cm to 300oz-in/21.6 kg-cm
1/8 Scale heavy 4WD 300oz-in/21.6kg-cm to 500+oz-in/36+kg-cm

These are just rough guidelines. The weight of a kit can vary a fair amount in each of these categories and again personal preference will play a part in your future decisions but these are probably good ranges to look at. There are a handful of kits that will not fit into the above categories. On-road and crawlers come to mind. On-road will probably fit into the 1/10 scale light 2WD category regardless of what it is just because on road has less resistance than off road and therefore wont need as much torque. Crawlers will fall into the 1/8 scale heavy 4WD category regardless of what they are because of the demand that rock crawling puts on a servo.

Throttle servos dont need to be very beefy in any rig. Anything in the 60-133oz-in/4.3-9.5kg-cm range is fine. i look for speed more than torque for my throttle servos but again if you arent racing speeds not all that important.

Trusted commonly used servo brand names to look for:
Savox
Hitec
Futaba
JR
Airtronics

One last segment of servo info. Spline count. The spline is the part that has teeth on it that the servo horn attaches to.
metal_gear_hitec_standard_spline1-jpg.jpg

Spline count is the number of teeth that the spline has on it. You need to know the spline count for whatever servo you have if you plan on using a servo horn other than the ones that came with the servo. The horn will need to have the same spline count as the servo.

23 splines: KO, Airtronics/Sanwa, JR, ACOMS, Solar, EXI.

24 splines: HiTec, RCD, Apollo (plus some Tower/Hobbico as HiTec makes them)

25 splines: Futaba (newer), Savox, (plus some Tower/Hobbico as Futaba makes them), traxxas 2075 digital waterproof servo, HPI, HobbyKing-BlueBird, some TowerPro [mg995 & mg996r], RC4WD

Additional info on spline counts for Hitec and Futaba.
Futaba Servo Splines
Hitec Servo Splines

Even more servo info :)

The difference between digital and analog servos.
(The difference between digital and analog isnt really
that important and analog servos arent even used that
much these days but I thought Id throw it in for
completeness.)


I hope this gives you some insight into servos. :)

P.S. If any one has any other servo info they would like to add to this please let me know and I'll be happy to add it to the post. trying to make it as comprehensive as possible. Also if anyone disagrees or thinks my torque ranges for various kits needs to be tweaked please let me know and I'll try to tweak them into something that is commonly accepted by everyone.
 
Last edited:
Also if you guys know the spline count of any servos not listed here post them and I'll add them to the list.
 
Last edited:
Thanks for the great info. I was wanting to upgrade the steering servo in my t maxx. I did some pokin around and found that traxxas 2075 was the most tourque I could get from trx. Yet it is rated at 125 oz well below the 180- 300 that you recomended above. So what I hear you saying is I am gonna have to climb out of the traxxas box I'm in if I want to have the desired performance I desire..
 
Id look at Savox Servos. If a 45mm tall servo will fit in the tmaxx they have one that is 500oz/in for something like $75-$80. If you need more of a standard height servo (38ish mm) then they have a few different possibilities, you'll just have to look around and see what works for ya :)
 
Id look at Savox Servos. If a 45mm tall servo will fit in the tmaxx they have one that is 500oz/in for something like $75-$80. If you need more of a standard height servo (38ish mm) then they have a few different possibilities, you'll just have to look around and see what works for ya :)
Thanks for the info!
 
idk how developed the site was like 4 years ago but anyone have any input as to how accurate this site is and whether its been updated?
 
Looks like it's up to date to me.
 
Looks like it's up to date to me.
thanks i was just curious because I'm trying to do some research but wanted to at least make sure i wasn't working backwards with misleading info... but right on thts good to know!
 
@Rolex Up at the top of my stickied thread about servos I said that
"For the total beginners out there just know that on a nitro rig you will need either 2 or 3 servos (1 throttle and 1 or 2 steering depending on the kit)."

It actually should probably read 2-4 servos because I forgot about the possibility of a reverse servo. I dont have the option to edit the thread myself so could you please just add that in there and just mention that almost any lightweight servo is fine for that purpose? Thanks.
 
It looks like someone already changed that for you but you'll still have to pay for my time as a consultant.
I'll have MY people get in touch with YOUR people.
 
servocity .used to have the same specs but changed the way they list servo I think it was about 6 years ago the changed formats. nice site non the less
 
Back
Top