What are the best non-digital servos for a big fun-fly such as Funtana 140 or 3W Xtra-Fun? I`m planning to use 5 cells (6V). Can I use 2 li-pol cells (7.2V)? I looked at the Hitec HS-645MG. They have about 10kg/cm at 6V. Is it enough?

those are to nice planes for cheap servos i wouldn't recommend any thing less than a hitec 5945 you can use a 2 cell lipo on a reg

The 645's would be fine for those planes. I use them on bigger planes with great success. They are good servos for the money. Have fun.

If the 645's are anything like the 605's (and I assume they are) they are junk. The 605 servos center lousy and have ZERO holding power. I don't care what the specs are, you can take a 3D arm on a 605 and EASILY push it to the side against the servo, and I run 6V.

If you want to go cheap get at LEAST the 5645's instead, they still don't hold or center great but are MUCH better than their non-digital counterparts.

The other servo mentioned would be better but at twice the price.

George you obviously have never used a new style 645. They hold fine and I have never noticed a centering problem. I have never heard of one failing either, but I can not say that for the 5645's or 5945s either for that matter. Use what you want, but don't knock a servo that you haven't even tried. I have 11 of these and really like them. I have had a couple of 605s that had centering issues but not a 645.

I didn't know the 645's were a different servo from the 605's. Usually companies just change the gear ratio and trade some speed for some torque. I wrongly assumed the 645's were just the same old lousy 605's geared differently.

I'll have to try a 645 and see for myself.


I still say 605's are about as bad as a servo can get [:'(]

From what I have learned, years ago the centering was not all that good on the 645s. They must have reworked it somehow because the newer ones are fine. You are right about Hitec using the same parts in different servos. The 5645 is just a digital version of the 645 using the same gear set. Same goes for the 5945 being a digital 945. Some folks are completly sold on digital servos. I am just not one of those people. I have 2- 33-35% planes ganging 2 645's per side on the ailerons. Never had a problem with fighting each other, battery drainage, excessive gear wear... nothing. Since I am always on a budget it is nice not having to buy matchboxes or a programmer. If I had more money to put into my projects I might use digitals, but I don't feel like I am giving up much by using analog. Whatever servo you use it all comes down to having a good time while flying. That is the main thing.

I just read they discontinued the 605's (good idea [:'(]) and came out with a 635 which has new circuitry and a smaller deadband of 4us (better centering). I wonder if the 625, 635 and 645 are all this same improved version of the 605??

I do have some 5645's in the ailerons of a QQ yak and they center well, have little slop but could hold a little better. If the 6xx series works as well as the 56xx I'd try some 635's for $30 each.

Thanks,

I think I will use Hitec HS 645MG/BB in 3w Xrta-Fun.
HS645 are much stronger than HS635.

HS635=6kg/cm (6V)
HS645=10fg/cm (6v)

Another question
I have got some HS-77 ang HS-225MG at home. Are they enought for alierons to 3w Xtra-fun?. Or 2xHS-77 for elevator?

Try Futaba 3305's. they are around $40 and have 130 oz on 6v.