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Talk Servo's!!!

PrimaRC

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Tekno RC's
  1. EB48
  2. ET48
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Basher
No issues at all. Im running via the XR8 Plus BEC output at 7.4v and its solid, no need to go to 8.4v at all. A beast of a servo! As soon as I installed I found no need to set end points etc at all - just seemed spot on. No servo whine etc whatsoever. Turns with authority at standstill on any type of surface (tested on grass too) - see no need to run at the higher voltage, it's more than enough - maybe even a little overpowered.
Bear in mind this was for my basher, I haven't a track near me to race, so not sure on longevity etc just yet, but so far its my new favourite (along with the SRT9032).
That's great news mate, I hope it stays as a favourite, they seem to be making some really great products.
 
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Tekno RC's
  1. EB48
  2. ET410
  3. SCT410
Driving Style
Basher
Age game: who remembers servo(s) included with the radio/receiver package?:p

The last radio package, that I can remember coming with servos, was my KO PROPO EX-5 (1990-ish?) with two PS-201S servos :LOL:. Check the servo's speed/torque specs out:
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Billl DeLong

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Austin, TX
Tekno RC's
  1. EB410
  2. EB48
  3. ET48
  4. ET410
  5. MT410
  6. SCT410
Driving Style
Racer
I think my Futaba Magnum Jr came with 2 servos as well when I bought it around 1986... I remember saving up all summer with my paper route money to build a Tamiya Hornet for my first RC car, ha!
 

RC_User

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Tekno RC's
  1. SCT410
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Hey Friends, bringing this back from the dead - I love talking about electronics!

I just picked up an ET410.2 kit to build over the winter and am considering servos.

Here are a few experiences i've had with servos recently...

I find in off road that a slower servo is totally fine. I bought a 2nd hand SCT that came with a Savox that was .15 seconds without problems, but I buy faster servos in case I re-use the servo in a different car and need more speed. You can always slow them down, but you can't speed them up.
As far as Torque, I agree 100% with what JennyC6 said - the "requirements" are way excessive. People are obsessed with numbers so it's turned into a marketing tool. I remember an older Associated 1/8 truggy I had, in the manual it recommended a servo which put out around 200 in/oz of torque and it did just fine. Ever try holding onto a wheel and turn it and see if you can stop it from turning? You can't even stop 200 in/oz by hand - how is turning a lightweight wheel that's rotating need even half that much power?! It doesn't.
But... I noticed nowadays most off road cars don't even have servo savers, so I believe the higher the torque of the servo means the less impact a hit puts on the (main) gears, as the tekno ET410.2 manual states recommending a 200oz/in minimum full size servo and says verbatim:
"Running less than our recommended rating will increase the chance of premature servo failure"

Budget: I don't buy the cheap servos but also don't spend $200 on a servo. My comfort zone is around $100. I'd consider close to $200 if it was the ultimate servo, but I don't see that happening, ever.

I currently have 3 Tekin servos which I bought 2nd hand but NIP for around $100 ea.
They seem to be a great value if you can get them for a deal. For example you can get the T300 from Tekin on "scratch and dent" sale currently for $110, which is $60 off. They have a unique feel in that you can turn them very easily when powered off, and 360 degrees... (which is programmable among lots of other things too)

Tekin T120 in my touring car. 0.05s at 7.4v. I never thought I'd need a servo that fast, but there was a certain track layout where I couldn't plan my turns well enough through some chicanes and my protek 140T servo at 0.08s was turning late (due to my lack of skills...) Well the faster T120 made up slightly through the tight curves and helped me get through quicker.
Tekin T180 on my 4wd buggy - it's a low profile middle of the road specs, 0.08 sec @ 7.4v i believe no issues so far but only a few runs on the car.
Tekin T250 on my 4wd SCT410.3 - no problems, interestingly, the tekno aluminum servo horn doesn't fit properly, the slight 'drop' on the horn rubs against the servo top case and actualy dinged up the aluminum, so I used the included Tekin horn which is similar offset just without the slight ~-.5mm "drop".
One thing I noticed with the Tekin servos and why I'm considering not buying another is that they seem to have a noticeable amount of backlash / slop in the gears. I don't think it has a real-world affect, but it bugs me how i can rock the servo horn back and forth and FEEL the slop and hear its "click". It's not much, just enough to trigger my OCD lol ... Honestly it's nitpicking - worn steering link/ball stud slop is more significant steering slop. I will likely pick up the mentioned T300 for $110 shortly - I don't think there is a servo with better specs for the price in a full metal case, especially with the amount of programming capability.

So the Tekin servos are programmable with the Hotwire. Since I already had a hotwire, win. I was excited to use the "Centering" option with the servo, which sets center instead of fumbling with trim. However, for some reason whenever I would set center, power the ESC off and on again, the servo would return to the factory default - it wouldn't save the setting for some reason, and this happened on two different servos. Not sure if I was doing something wrong or what, but I gave up on that feature.
They also have other settings such as slowing it down (alternate to speed setting on radio), a "torque" setting (Not totally sure what this does, perhaps limits the amount of torque it will put out before stopping the effort), amongst other things such as shut down temperature. Pretty slick, but I kind of feel like at the end of the day a servo just needs to turn reliably 99%, fancy features are needed 1%.

I also have had a few Savox servos - they are definitely a good value but never been a huge fan due to an experience in the past where one would brown out my ESC's BEC. It's funny how on amain's website, every savox description mentions that in some cases they can pull too many amps so they suggest using with an external BEC... Due to this I'm not really interested in a Savox servo for this kit, although I have used a couple others with no issues, they really are a great value and hence why they are so popular.

MKS: i have an MKS low pro in my other touring car. Bought it 2nd hand and should have returned it to the owner. never seen a servo jitter so much in my life. I should have known by the suspiciously low price he sold it for. I would have never sold a servo in that condition, however it still seems to work well enough and it's on a super cheap chassis and made it through one winter season so i've left it on to see if it survives another. The MKS servo specs are impressive and the servo footprint is the smallest/shallowest low pro i've ever seen. However, due to its epic jittering I am not sure I'd buy that brand again, I'd rather do something different. I realize every brand has failures and MKS gets great reviews.

FUTABA - Possibly my favorite Servo (that I foolishly sold) was a higher end Futaba, it was just so quiet and fast and powerful... hard to explain but sometimes you just fall in love with the total package even though it isn't any more special on paper than brand B. I may be a bit biased because i've always been a big Futaba fan. Interesting is that their high end servos like the CB700 that @EvilT uses specifically states that they are not supposed to be used with a BEC and are designed to be powered directly from a battery. This makes me think that they likely pull a lot of amps that some BECs can't handle. One other interesting thing about Futaba is the dimensions of their high end servos are a hair larger than a standard 20x40 - usually like 20.5 x 41mm. doesn't seem like much but guess what - it won't fit in a SCT410.3 servo tray (that's why I ended up selling mine and now a Tekin servo sits there)

And that's the next topic ... amp draw... with more torque probably comes more potential amp draw.
One nice thing about Savox servos is that they actually list the stall amperage! How many people even have a clue what this is... I'd say less than 1% because nearly no servo manufacturers publish it. In theory if the servo binds and pulls potentially 5 amps before it stalls, and your ESC's BEC only has a rating of 3 amps, what happens? Your BEC may "brown out" and cause the ESC to shut off and on again. Yes it's a long shot that it would ever happen, usually a servo pulls 1-2 amps under normal circumstances turning light weight racing wheels, so a BEC doesn't usually need to be very beefy. Most are rated 3-4 amp continuous...

Having RC OCD, I had to know what these Tekin Servos stalled at, so I emailed Tekin asking for the stall amperage on the 3 models I owned. They replied verbatim:
Our servos are intelligent and self-limit when they can't reach the target position and will only draw about 4.5A completely stalled out, at which point the bind relief will kick in and reduce power even more.
Pretty cool feature to prevent damaging the servo under unfortunately circumstances I suppose, if it actually works. I have not tested that feature but it would be very interesting to do so. With the hotwire you can program how much it reduces the torque if the servo binds for 2 seconds. I'd vote for 100% reduction lol - If it can't get to target position in 2 seconds something is seriously wrong.
Cool feature nonetheless to prevent damaging the servo.

I would love to know the stall amps ratings on some of the Futaba and Protek servos, as those are the top potential buys for me.
I emailed amain on the Protek 160TBL servo that I was considering last year and this was the response:
Here is the info we have on the 160TBL servo. You can find whatever specs we have at the bottom of the servo page. Below is a pic of what we have. I did find a nice page explaining how to measure the stall current based on input voltage. Here is the link to that. I hope this helps as I haven't dealt with that aspect of power rating before.

...In other words they have no idea, but go figure it out yourself. I realize Amain doesn't actually MAKE anything - that their servos and everything else they sell that has "Protek" on it like batteries and chargers are made by some factory overseas and they slap their label on it, so I'm not totally surprised that they don't have this info in front of them, but they sell thousands of these servos so I would expect them to be able to get the info without too much trouble. I haven't tried to reach out on the Futaba because I never decided which one I was seriously interested in.
 
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Tekno RC's
  1. EB48
  2. ET410
  3. SCT410
Driving Style
Basher

RC-User, some of the Protek servos are just rebranded Power HD versions. A lot of rebranding goes on in the servo market. The same with some line of chargers. One popular Protek charger is an EV-Peak model. I can't keep track of everything.

As far as the ET410.2 goes, it would depend on track surface I was running the RC on as to what amount of servo "power" I think would be needed. For me, I've used an "old school" 200 oz-in servo for the past couple of years in my ET410 that gets ran on outside dirt track with 3 1/2' no downside jump landings. If I was running on hard surfaces I certainly would consider more torque for those one front tire landings on high traction tracks.
 
Messages
212
Reaction score
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Tekno RC's
  1. EB48
  2. ET410
  3. SCT410
Driving Style
Basher
Interesting is that their high end servos like the CB700 that @EvilT uses specifically states that they are not supposed to be used with a BEC and are designed to be powered directly from a battery. This makes me think that they likely pull a lot of amps that some BECs can't handle.
I currently have a servo, in a monster truggy, that stated not to be used with BEC. I had to test the waters with Hobbywing's MAX6 "6amp" output to see results for myself on a 5.5A stalled servo. So far, so good.
 

Dirt Booger

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I have run lots of HiTec (high voltage and standard), Ko Propo, Savox, ProTek brushless and a smattering of cheap varieties over the past 20 years.

Best servos I have found hands down are from Holmes Hobbies. Mostly run in the crawler crowd, but he is a good guy who make top notch electronics.

I have been steadily replacing every servo with a HH brushless version that runs straight off of the lipo, no need for a strong BEC and never a chance of a brown out. I recently put this one in a truggy and it is insane, you really don't know how well an powerful steering servo works until you have one...

https://holmeshobbies.com/electronics-and-wiring/servos/shv800-v2-servo.html
 

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