Hitec servos: 645 vs. 5645 vs. 705

[gobucks]

Hitec servos: 645 vs. 5645 vs. 705

I have basically narrowed down the choice for a servo for my Twin Force. Keep in mind that I will eventually go with rear steer and probably buy an identical servo to match. I do not want to run a receiver pack and will be running a 6-cell pack; opinions on the list of servos please. If there are better choices with simular specs and would be easy with customer service for warranty work, please list also.

[thefordmccord]

I run a pair of 5645 servos on my TLT at 7.2 volt with no problems at all. They have been on the truck for about 8 months and have been run pretty hard. I don't run servo savers on them either...

[JamisonWorkshop]

CS-80 Hobbico.
It is the same thing as the HS805. and if you were thinking 705 1/4 scale, myswell step up for cheaper and never look back. Get the Novak 6v regulator from tower to tp it off. Good to go.

[gobucks]

Eventually having two CS-80's would be hard on run time with a single 6 cell pack? Or will the 1/4 scale servos have the same draw as two digital standard size servos?

[JamisonWorkshop]

it was kind of a pain at first, but I was running one right off of the battery. burnt it up, put the regulator in helped. (less draw). then I put the lathe motor in and that made it much better. I ran for an hour with only front steer. Rear would hurt a little, but I am only running a 2400 pack too. The size, and force is well worth it over the runtime. and they are cheaper than most. gear set is only 5 bucks too.
I would rather not break. I have 7 batteries anyway so I dont mind swapping them out.

[gobucks]

Basically the reason for this thread is to determine which servo is going to hold up best. I hate to break also, the reason for my heavily modded T-Maxx. I beat the crap out of it and I do not break. I run a Hitec 5645 on my Maxx with the Proline steering/ servo saver kit and this servo just keeps on trucking. It was even submerged in a creek last year, dried it out and no problems. I have just read that digital may not be the way to go for crawling? But the power draw for 1/4 is a hold back for me.

Setup: Twin Force with GD-600, Integy 55T motor, single GP 3300 6 cell pack, eventually 40 series Moabs. Two CS-80's would give approximately what run times? And add a 6 volt Novak regulator to boot?

Thanks a ton.

[JamisonWorkshop]

With only moderate use of full throttle and rear steer. I would think 30-45 minutes. I will be able to let you know more after this weekend when I really take it out with the proper setup.

but I was getting 25 minutes with 2400's no regulator, heavy throttle and rear steer. and no lathe motor. (stock).

[nd4spdbh]

Well with my 30 dollar Trinity 3600mah pack a 55t integy 2 645mgs and 2 of my regulators... HOW to make a 6 volt voltage regulator! ... i get 1hr 30min + of runtime ... i am runnin an Lrp runner and a tq3 with masher 2ks alll of this runnin on a TLT.

[JamisonWorkshop]

Yes I am hoping for about 45 minutes with my 2400. With the 3600 you are probably right there, and smaller servos.

With run times like that There is no way I would be worrying about losing a little because of servos. My rustler is lucky to get 20 minutes. So anything more in the crawler is fine with me.

[mike]

What about the HS-945MG?

[nd4spdbh]

a 945 isnt really worth it for the extra amp draw u really only get 20oz/in of torque... if its for a TLT go with 645mg's ... i have been very happy with the preformance of these servos at 6 volts i have 3 of these servos 2 for tlt and one for a savage and i have never broke one!

[gobucks]

Is it necessary to have one voltage regulator per servo?

[nd4spdbh]

well it depends on the regulator... the little regulators that i build only handle up to 1 amp so a 645 pulling like .5amp per regulator keeps them nice and cool. but if you had a 3 amp reg u would be fine.. even a 2

[JamisonWorkshop]

yup and on the 1/4 scale the super rooster can handle one and with the regulator I have with another 3amp output it handles the other.

but on the 645's the Rooster can handle both no problem with no regulator.

[gobucks]

What specs determine the type of regulator to use with a certain speed control and servo/ servos?

[JamisonWorkshop]

I am sure nd4spdbh knows plenty more than me. I just go by the BEC rating which is 3 amps on most. Which is what you want to look for how many amps the esc or regulator can supply. and then how many amps each servo can draw.

If you go here. They tell you some of the specs of each.
servo hut

like the 5645 has a no load of 500ma, the 805 1/4 scale is 850ma no load.
That can go up considerably once you put a load on it. Would like to do a load test some time.

But the bottom line is servos (should) only be ran at 6v. so that is the max there. the amount of amps they can put out the more the better. It wont hurt anything.
but 3 amps is fine for small stuff and 6 amps is fine for large stuff. maybe even 4.

[gobucks]

O.K. I am trying to understand the theory. Take for instance, the Super Rooster has a BEC of 6V and 3A, then you should not need a regulator even for two 5645 servos? The servos are protected by the speedo from pulling more than 6V and the servos can't ever draw more than 3A from the speedo even at worse case?

[JamisonWorkshop]

you got it. but when the servo tries to draw more that is when you start to get glitches. but with 2 standard servos you should not have a problem. If it starts to glitch and there are no other causes THEN you need a regulator from the battery to power one of the servos to take the load off of the ESC.

[gobucks]

Thanks JamisonWorkshop. Great info and help.

[chafey]

one difference between the 645/5645 and the 945 is the thickness of the output gears. the 945's are twice as thick and they take a beating.