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Gazzalene

Steering servo spec?

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On a XV01 chassis what should I be looking at for servo spec?

Standard size?  what sort of speed and torque?

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To suggest a servo, it might be helpful to know the intended use. Is the car intended to be a fun basher? A rally car? A serious racer? The more demanding the application, the better the servo specs should be.

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The old standard that had been used since the late 90's was Futaba S3003.  

Speed: 0.23 sec/60° @ 4.8V
0.19 sec/60° @ 6V
Torque: 44 oz-in (3.2 kg-cm) @ 4.8V
57 oz-in (4.1 kg-cm) @ 6V
Dimensions: 1.6 x 0.8 x 1.4" (1-9/16 x 13/16 x 1-7/16")
(40 x 20 x 36mm) 

Even a $3 servo from Hobbyking does 0.21 second and 3.8kg-cm at 4.8v.  $7 Hobbyking servo does 0.2 second and 8kg.  $10 one does 12kg, but a bit slower at 0.26 second.  Whenever I buy from Hobbyking, I stock up on those servos. For bashers, those are good enough for me.  For a serious racer, you can spend as much as $200.  

 

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I aim for around 7kg torque and higher, and as close to .1 sec or faster as I can.  Basically, faster and stronger is better (but not necessary).  I also prefer low profile as they take up less space, although they are a bit more expensive than standard size for the same spec.

The cost range from US13 to US60 (although I have some of those crazy US200 jobs in my 8th buggy).  You get what you pay for, and what I find is the cheaper they are the less believable their claims are.  So far I haven't had any fail either, but the Savox have done 3 seasons of offroad racing and I bought those secondhand, so they are very reliable. 

Look at Savox 1258TG, Savox 1251MG, (US50+ and most places have Savox) Trackstar TS-D99X (US25 and Hobbyking sell them) and JX PDI-4409MG (US13 and Banggood stock them) if you were after some recommendations.

Really the bang for buck best is Savox 1258TG as it is fast and strong and the same price as the slower and weaker 1251MG.  The only thing is the input is 6V and now you can get BEC with 7.4v output, and rx that handle a 2S lipo no problem (so the servo gets 7.4v nominal which is really 8.4v on a full charged lipo), so it depends on the application.  Check the BEC of your ESC as you may need a HV servo.

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Sorry, i forgot the intended use. Just for fun really but would like to put something in that will perform good.

Did not want to get a slow servo and think that is the norm. I think the speed is the thing I was more unsure about.

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1 hour ago, Jonathon Gillham said:

JX PDI-4409MG

Thank you for the info!  I just ordered 2 of them!! 

(Just so you know, I wasn't the guy who needed a servo, but why not? I can't refuse a good servo--especially if it's cheap, fast and strong)  

 

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3 minutes ago, Juggular said:

Thank you for the info!  I just ordered 2 of them!! 

(Just so you know, I wasn't the guy who needed a servo, but why not? I can't refuse a good servo--especially if it's cheap, fast and strong)  

 

Hopefully you won't be disappointed!  The quality appears very good, much better than the cheap MG995 and some of the random S3003 equivalent's I've seen in the past.  I suspect they are actually the same servo as the Trackstar TS-D99X just with a slightly different case but haven't opened them up to compare (and won't, since then I'd have to take the Trackstar servo out of a car and that just seems all too hard)

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I have owned both JX PDI-4409MG and Trackstar TS-D99X. Not even remotely the same.

4409MG doesn't meet it's specs. It is slow as a wet week and has a big deadband (8-10us not 2us as claimed). It is however reasonably strong. All the JX servos are much slower than their spec from what I have seen. If you want an OK servo for cheap I guess they are alright. The build quality seems to be there, the performance specs are just blantently made up.

8-10us deadband starts becoming unacceptable for racing or on road speedruns. When you steer left and back to center, the car is still steering noticably left, and when steering right and then back to center, it's still steering slightly right. The smaller the dead band, the better it recenters.

D99X meets its specs - fast and with negligible deadband (<3us), small enough in fact that it occasionally 'hunts' (buzzing sound as it rapidly alternates back and forth between two increments). Mine did develop a problem with a bad solder joint or some such. When the rear cover was squeezed the servo would rotate all the way to one side. In trying to troubleshoot it with the covers loose I managed to snap the plastic end stop off the front cover. Couldn't work out what the problem was, ended up binning it. I'd happily buy another at the price I paid (AUD$28), but would think twice at their current pricing ($40). The only servo I have that performed as well as that one is a Savox 1252MG but that set me back $80.

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I'm stuck on low-profile servos for most builds. The Savox 1251 is more than sufficient for just about anything, although there are plenty of spendier servos out there. I use some brushless aluminum cased Turnigy low profile, mounted vertically, in my XV01. I got it for a song, and it's been exceptional.

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