I'm finishing up my Spacewalker build and am installing the servos. I'm running a Hitec HS-5625MG on each elevator half, a 5625MG on each aileron and a 5645MG on the rudder. I'm wondering if I need to bother with supplying the servos with power directly as opposed to just running them through the bus in the receiver, a Spektrum AR-7000. As near as I can figure from using a servo torque calculator the rudder servo load will only be about 2/3 of the rating of the servo (143 oz.) and the aileron and elevator servos will be slightly less than their rating (110 oz.). I'm thinking it should be OK. Thoughts?




Mike

I have a Ryan STA with the same servos, except for one on elevator, and it does fine with a Futaba receiver. Just be sure you have enough battery power for the digital servos.

I used those servos directly from a reciever for the Cermark 25percent Yak review and flew it for months that way, you won't have any problems. The loads on that thing were a lot higher than you'll see on a spacewalker.

Good luck, sounds like a fun project.

Thanks, that's what I figured but this is my first model of this size. The biggest so far was an 80" 13 lb. Ultra Sport 1000 with standard servos. As far as battery I'm using a 2400 mah sub C Nicad pack and a 1400 mah Nicad pack on the ignition. I should be doing the maiden on it next week some time.




Mike

I agree, you'll have no issues. Now I'll toss out another suggestion. If you use A123, there is no way you would be able to outdraw those batteries. One thing you have to be careful is not letting the battery voltage drop at anytime below the voltage required for the reciever, especially 2.4. If it does the reciever will either reboot or go into a brownout which you will have a momentary lockout. High torque servos can spike enough to draw a 6 volts battery way down for a split second but that is all that is needed to cause the reboot or brownout

Again, let me be clear, with what you are planning on using you will be fine, but if you really want to make sure, the A123's are the way to go and BTW, no regulators needed but you will need a charger that can handle A123 cells plus you will be a little lighter. You may have to charge a bit more but with a good charger, you are looking at 15minutes to do 2000Mah versus several hours on Sub C cells of the NIckel Metal or Nickel Candium types. Also, you cannot load test A123 batteries, so it's important to know how many MaH you use per flight on average

I use A123 2300Mah packs on both my 40% planes with 10 to 12 servos, mainly 8611a's and 8711. I use 2 on the receiver (both Spektrum 9100'S) and one for the ignition (DA170's on both), I can go 7 flights then recharge the receiver batts on average about 1900MaH per battery. The iginition can easily go to 20 flights

On my 35% I can go 10 flights and still only do 1500, same amount as the 40% for the ignition (Da100)

On both that is typical IMAc style flying, hard 3D will use more MaH per flight

Why would you say several hours to charge? Any decent sub C NiCd can be charged at 2-3C. Even with sub C NiMH and taking it easy on them, it wouldn't take more than an hour.





Mike