servo question

[ls1fst98]

So I have been looking around at all the different servos out there, low profile, standard, 1/4 scale, and I'm wondering what is the general rule of thumb as far as amount of torque that is needed. I know metal gear is pretty much a requirement. How important are other factors such as speed. Obviously you don't want a super slow servo but is there such a thing as too fast?*!**

I have talked about this at the local lake with gas guys and they all say a servo with at least 250-300oz/in of torque, but I have seen and own some fe twins that have less than that and one is a fairly large hull. The only servo I have that's even above 300 is a savox that I bought on a whim cus it was super cheap for what it is, and it's at 448oz/in.

[Make-a-Wake]

It depends on what size boat really. On my 35" and below I use the very affordable Traxxas high torque waterproof 2075, about 50% more torque than the standard 2056. The 2075 has been very dependable and more than ample. Torque also depends on how far out on the servo arm your steering rod is. You can move the rod in and use a higher endpoint setting on your Tx for higher torque. I personally don't see a need for high dollar servos in my mid to smaller size boats when the Traxxas ones have worked perfectly. Steven sells them here on OSE so I would imagine he sells quite a few of them.

[RaceMechaniX]

Speed is probably the least important factor. If the servo is faster than .20 seconds/60Deg you are fine. Unless you have a 8 second per lap boat that weighs 20+lbs you should be fine. The torque output will depend on the hull, linkage ratio and several other factors. In general I would recommend a metal gear servo from a reputable brand with 200oz or more.

TG

[tlandauer]

Low profile standard size or 1/4 low profile, just curious.

[kfxguy]

I like to use the 0231 savox waterproof servo. I use them in just about everything I build. 43 bux you can't beat them.

[ls1fst98]

Thanks for the replies. I have tried to search Google and here for anything as far as what may be a standard but just like most things I guess it comes down to a trial and error. I have had an issue on a large mono (47 pursuit with castle 2028 on a 457 prop) where it would not turn left to save it's life. I'm now upgrading it to a 1/4 scale with over 400ozin.

[ls1fst98]

I got the 1231sg for a killer deal on ebay, thought it was a miss price. Was under 40$ and came with an aluminum arm. It's a powerhouse at 400+ in a standard size. Now they are 80

[NativePaul]

It the size or more importantly torque of a servo depends largely on the size of boat it is for, I use >2kg/cm for 18" boats, >3kg/cm for 24", >5kg/cm for 30", >7.5kg for 36", and my sole big boat at 42" uses 12kg/cm. With that in mind there are a number of features and specs that I will list in order of importance (to me).



I always use digital servos, the holding torque is so much better that the price is WELL worth paying.

If there are several different gear ratios available I will go for the high torque version as long as it covers 60 degrees in under .2 of a second, more speed is good but if I would have to step up a size to get the same torque from the high speed version, I would rather save weight.

If I have different gear materials available in a servo that meets my needs above I will go for the plastic version, as the cheap metal used in most servos wears very quickly in comparison, and in boats I have replaced more metal gears that have become sloppy than plastic gears that have broken. My favourite gear material is Hitec's Karbonite, as I have had some pretty solid rudder hits without breaking any so they are strong enough for me and they don't wear quickly out like metal, unfortunately there are not many in the range and I think Hitec are the only ones using them. Titanium is the best being stronger than "metal gears" and not wearing out fast, but you have to pay a pretty penny for them.

I like ball bearings in servos and run them where possible.

Some servos are noisier than others in my experience Futaba are the quietest, then Hitec, then Savox/Spektrum the most chattery. As with most off brand Chinese stuff it seems to be a bit of a lucky dip, I have bought a few, broken or not been happy with slop or chatter in most, but am still using one after years and am still happy with it, and that one saved me enough over a name brand to pay for all the ones that didn't make the cut, but it was a PITA getting replacements and the bad ones put my boats at risk, so I will quit while I am not behind and stick to the name brands again.

It is great that there are waterproof servos coming out, and hopefully one day all servos will be waterproof, but there are not nearly enough yet so it severely limits your options if you stick to them, I ignore the fact that some are waterproof and just pick the one with the best specs for the job according to my above criteria, it is easy enough to waterproof a servo yourself.