Which Servos?
 

I'm trying to decide on the elevator servos for my Westbury Hunter. I was planning on installing a JR DS3421 servo (65 oz.in. torque) in each tailplane, but I have discovered that the servo is about 1/8th inch thicker than the tailplane.

My alternatives are either the JR DS168 (47 oz.in.) or the JR DS368 (53 oz.in.). I have some DS3301 Wing Servos (56 oz.in.) but these are the same thickness as the 3421.

I could always make up a servo cover with a bulge in it, but that is my last resort.

Will the 53 oz.in. DS368 be adequate to drive each individual elevator half. Each elevator is no bigger than 2in x 10in. I will be using a JetCat P80 for power and the kit is predicted to weigh about 20lb when complete.

The torque figures quoted are at 4.8V. I guess I could run 6v and get a 10-15% torque increase, that would make the 368 output about 60 oz.in.

Thanks for any info.

Paul

RE: Which Servos?
 

Apparently JR servos do not like 6v (5 cell packs)! IIRC, the last lot I bought had some warning on the package. I think it is to do with the fact that a fully charged 5cell pack could initially read over 7v

RE: Which Servos?
 

The only JR servo that specifically cannot be run on 6v is the 341 if I remember correctly. I run everything I own on 6v without issue.

JSF-TC - How long is the control horn going to be on the elevator itself? Here's some info you might find useful.

This is based upon a 2" chord, 10" span control surface @ 200mph with the control horn 1" from the hinge line (not the surface of the elevator).
1/2" servo arm, 1" control horn - Servo travel of 45 degrees gives 20 degrees of surface movement and require 25oz" of torque.
3/4" servo arm, 1" control horn - Servo travel of 45 degrees gives 31 degrees of surface movement but now requires almost 60oz" of torque.

So any of your servo choice SHOULD work ok. Of the 3 servos you mention, I'd prefer the DS368 due to the metal gears.

RE: Which Servos?
 

I am not sure, but I thought the JR 331 or 241 was the one restricted to 4.8 volts. I was under the impression that the 341/351/368 were the basically the same except the 351 has metal gears and the 368 is a digital with metal gears.

RE: Which Servos?
 

I checked with Horizon and the ONLY servos restricted from using 6v are the 321 and 331 Micros.