Performance servos for 1/8th scale.
 

I have a few questions for the hardcore 1/8th scale racing crowd.

What do YOU use for performance servos? And specifically how much torque do you feel is the minimum requirement for a racing buggy/truggy(even racing MT)for both steering and throttle/brake where the specs become literally a non issue issue?

Also for servo transit speed, what do you feel is the bare minimum requirement for transit speed on steering and throttle/brake servo arrangement where again speed/response is not the limiting factor?

Currently for my racing LST XXL I use 3 Tower TS-170's(Rebadged Hitec 7955's)which give me claimed specs of .15 transit speed and 333oz. of torque per servo(666oz. of torque for steering). I assume these have more than enough torque for steering and throttle/brake duties, but for my SC8 and RC8T Im curious if the transit time is going to be quick enough or if I should look to something faster?

ANy opinions or thoughts appreciated! :nod:

I mainly use the 7955's (on 7.4v Lipo) for throttle and steering on my buggy and truggy

I have used 7955's in the past, very solid but WAY overkill for my buggy and they are somewhat slow.....JMO

this season in buggy I am trying a pair of Savox 1258TG's

i really like my Futaba servos, i have tried hitec 7955s, JR 9100T & S, airtronics, savox,and now futaba. the hitec 7955 is next to indestructible, ran them for 2 years. i have the Futaba BLS351 for throttle/brake and the S9157 for steering. they are extremely smooth and they feel a good bit faster and stronger than they say.

BLS351 - Torque: 217 oz-in @ 6V
Speed: 0.13 sec @ 6V

S9157 - Torque: 425oz-in (30.6kg/cm) @ 6V
Speed: 0.14 @ 6V

Buggy: Futaba BLS351 for steering (enough torque and quite fast), Futaba BLS451 for brake/throttle (very fast and enough torqe)

These are brushless and can be run from 2S LiFe straight. Then they have even more power than stated.

So in your guys opinion a transit speed of .15 is too slow for steering and throttle? If so what speed should I look for where the servo does not become the limiting factor?

.15 would be the slowest i would go IMO, it just so happens we are running less than .15 ... .15 is fine for both servos but IMHO its a little slow for throttle but it is still fine... like the guy before your post said, a 2s LiFe battery will make them faster and stronger and you can run them unregulated ... i dont trust LiPo and these LiFe packs are awesome and well worth the money.

From what I understand Hitec 7955's can run "unofficially" at 7.4 volts and have a slightly faster transit time of around .12 and torque of around 400oz.

I myself use 1700mah LiFe reciever packs which run at 6.6volts and are supposed to be "safe" for normal 6volt operating servos. I use Spektrum recievers so I can run anywhere from 4.8volts up to over 7.4 volts anyway.........

It's personal preference really.....I race 1/10 electric offroad quite often so I like a faster reacting servo to input. I am running these on steering and t/b in a HB D8 car.....I would'nt recommend this servo for a arena truck application but for buggy it should be dialed and plenty!

these are the specs on the Savox 1258TG, I will be running a standard ni-mh hump pack.


Speed @ 6.0V: 0.08 sec
Torque @ 6.0V: 166 oz-in

posted in electric off-road forum....hope this helps clarify!



Originally Posted by Email from Hitec
ORIGINAL: tohm

We have tested the HS-7955 with 7.4V lipo packs and have not had any adverse problems. Many of our team drivers/pilots have been doing this for some time now. The spec sheets will probably not change, as they were written in 2007, way before we did actual testing with the higher voltages.

At 7.4V, the torque is 387oz/in and the speed is .13sec.

Tony Ohm
Hitec/Multiplex USA

So for throttle what do you feel should be the minimal transit time for fast snappy response from the engine? .12? .10? Faster?

Since Im switching from 6volt nimh packs to 6.6volt LiFe packs Im wondering how much speed Ill pick up from the TS 170 servos.........

The Servos Im looking into picking up are the Savox 1267 and 1268MG's or the Hitec 7940TH or 7945TH servo and pick up the Hitec programmer with it........choices, choices.......

it's personal prefernce, there are no magic stats that work for someone, find a combo you like and stick with it...

IMO 200 oz for a buggy and 250 for a truggy is the min for steering, but servos these days blow that out of the water. My fav servos are the KO RSX power servos 436oz @ .11 sec. Way overkill but by far the smoothest servo I have ever seen. For throttle I like somewhere around 180oz or higher I have used less but I think they struggle with the brakes. The Savox 1268 are a descent choice too great price and good #'s 361oz @ .11 sec. I am using these in a MBX6T on both steering and throttle and they are good so far. Also you cant go wrong with Hitec's personally I would use 7950 or 7955 and I would stay away from the 7940's I dont think they are quite up to the task of 1/8 scale long term.

I have been real happy running a hitec7955 in buggy. speed is good enough on LiFe batteries.

I would use your existing servos for steering and get something like the hitec 7940 for throttle.

transit time ratings can be suspect as well. I've seen two different branded servos, both .15 transit time, react a lot differently.

My personal choice would be savox.

Most people seem to think that running LIFE will give them a full 10% advantage in speed and torque. This is not true. A good NiMH pack when fully charged will be ~6,5 volts under load and will slowly go back to 6 volts. When it gets lower then 6 volts its as good as empty and will drop to 5 volts pretty quick and then collapse. A LIFE battery starts at 6.6 volts under load and will slowly go back to 6 volts aswell, under 6 volts its pretty much empty and will loose power quickly aswell. Only difference i can see with LIFE is that it will stay at round about 6.6 volts for longer so the average voltage will be higher over its discharge (but not very much).
Ofcourse its much lighter which is the biggest advantage of LIFE imo.

.13 or faster for throttle... IMO i would get the savox 1256TG for steering and 1258TG for throttle servos with LiFe pack is the best cheapest combo out... personally i wasnt a big fan of Savox but they are good for the price, thats for sure

not true... first off my LiFe starts at 6.8V or 6.9V (so my charger says) and then after a few tanks of practice, three 5 min quals with 2-3min warmups and a 30 min main, my LiFe pack still has 6.45V in it (checked with voltage meter).... the servos stay stronger and faster longer instead of a constant drop off like with NiMh... i believe life drops the speed by .01 and probably adds about 15oz/in of torque or more. LiPo does put out more, but ive seen to many of them swell up and burn and seen a few cars whole electronic system burn up due to LiPo...

On the flip side, futaba servos are good, just not good for the price. A servo doesn't have to cost over $100 to be good. :)

True, LIFE will stay at ~6.5-6.6 v longer but thats not my point. Im saying it doesn't boost performance by 10% compared to NIHM as NIMH will start at 6.5v and stays above 6v aswell untill empty... (measured under load)

Btw, the LIFE packs i have here start off at 6.6 volt - measured under load

For me LIFE in the first place is weight saving and secondly more consistent servo operation, not so much about extra performance.

Servos
 

The 7955 is the best steering servo even though it's a bit slower, it won't get messed up nearly as easily as other brands....

For the throttle I like the Futaba bls451 because it's really smooth and fast, and won't get damaged from vibration....

I'm thinking about the Hitec 7950 for ST and the 7954 for TH in a truggy. Has anyone used a 7954?

That is 100% exactly the setup I run and will continue to run...that BLS 451 is such a sweet servo for throttle !

The 7954 is basically the official "high voltage" version of the 7955. .15 transit/333oz torque at 6v, but at 7.4 the speed and torque go up about 20%.

Yup 7955 steering BLS throttle awesome setup many years never had one issue. Last month took some hard front hits on the steering bent two ALU horns one broke in half. Same servo running perfectly, center every time without issue. That's crazy will always run the 7955 period they are ROCK SOLID NO QUESTION.

Cool
 

Yeah, the 7955 is the monster give me all you got steering servo, and the bls451 is the smooth fast and precise throttle servo....

OK, well I bit the bullit and went with a Hitec 7940 HV servo for the throttle (.07 transit time with 180oz torque at 6volt/.06 and 220 at 7.4volt)and a Hitec 7950 HV for the steering (.15 transit time and 403oz torque at 6 volt/ .13 and 486 at 7.4)along with the Hitec programmer. Got 2 pairs of each, sure wasnt cheap. :lol:

Considering how strong these servos are and the assumption that they draw ALOT of current, I hope a 1300mah LiFe pack gives me decent run time. Im eventually going to grab a few 1700mah Reedy Life packs when they become available.

i personally use Savox SC-1258TG -throttle, very quick, very-good torq.
Savox SC-1256TG - steering, just a tad slower but a fair bit more torq.

i currently run a Savox SC-1256TG for steering and an ace ds1313 for throttle in my buggy. i used to use ds1313 for both steering and throttle(.13 @ 173oz). after using one for steering after 2 years, .13 started to seem to slow so i bought the Savox SC-1256TG and i love it.