[Hughes500E]

Hi guys,
Will be setting up the Goldberg Sukhoi this winter (kit built 2nd edition). Planning on using a HS-645MG on both rudder and elevator, setup as pull pull.
Anything I need to know about the 645MG's? Positive or negative comments welcome

Thanks

[craigk]

I have the same aircraft CG Sukhoi, Saito 150
hitec 635 for rudder mounted in tail - short solid pushrod to rudder
hitec 5645 for ailerons -
hitec 5645 for elevator in fuse - two pushrods, one for each elevator half, tied together near the servo -

no issues with the servos
I am having a heluva time with tight outside manoeuvers though - it wants to roll out - inside manoeuvres are better
and down elevator is a pull action - so flex of the pushrods isn't it.

any way hitec 645s are just the non-digital version of the 5645 right?
sholuld be fine

[Kevin McGrath]

Ummmmmmmmmm......nope Craig the 645 and 5645 do not appear to be the same except for the digital feature.
The 5645 develops 143oz/in torque @ 4.8 volts speed .23 seconds

The 645 is 107oz/in torque @ 4.8 volts speed .24 seconds.....

There is a price differential of about 30% too.......

The metal gear trains are probably bullet proof in either servo and either one would do the job in the application you fellows are using them for IMO.

[Guest]

Originally Posted by Kevin McGrath

Ummmmmmmmmm......nope Craig the 645 and 5645 do not appear to be the same except for the digital feature.
The 5645 develops 143oz/in torque @ 4.8 volts speed .23 seconds

The 645 is 107oz/in torque @ 4.8 volts speed .24 seconds.....

There is a price differential of about 30% too.......

The metal gear trains are probably bullet proof in either servo and either one would do the job in the application you fellows are using them for IMO.

Very slow for rudder and elevator, and not enough torque for large rudders being used for aerobatic purposes. They will work but are not optimum

For my pattern stuff (which is similar size to the Goldberg Suhkoi), I put at least 100 in-oz/0.14-0.16 on elevator, and I was using 132 in-oz/.18 and felt it was lacking so I tried a new servo which is ~190 in-oz/.14 and wont be going back.

I speaking all digi's, non-digi's should be faster and have more torque output to get a similar feeling.

Craig.....

Sounds like your lateral balance is out. Fly upright trim for perfect level, fly inverted and hold only elevator to hold the altitude....watch for a roll. If it rolls your lateral balance is shot and thats likely causing your problem.

[Hughes500E]

Thanks guys,
Glad that I have not heard issues with them yet
Chad, I won't be competing against you anytime soon

Is there any maintenance associated with the metal gear train at all?


Thanks again!

[SJrcflyer]

If you can run 6V into those 645's you will be happier. More torque and more speed.

[Kevin McGrath]

Metal gears will wear faster than nylon and I would not touch the Karbonite gears.If the servo ever gets sloppy enough to worry about your need of accuracy for your flying (as opposed to competition lets say) just replace the gear train .I would make a point of making sure there is enough grease on the gears but its easy to overdo this kind of maintainance.
Its true 6 volts will give you faster speed and more torque at the cost of higher current draw and there may be other minuses to this........there is no free lunch........

[SJrcflyer]

As long as you run a decent size pack you'll be fine on 6V. A 1500 or around their, 5 cell NiMh would be your best bet. I'm running 5 625's and a standard on a 2100 5cell Nimh and will give me quite a few flights without haveing to worry about a thing. Overkill yes but I got a good deal on the packs.