We have a need to make some changes in our rules about servos.The rule about servos with only 4 grommets and
40 oz,in.torque. We now can get Digital Micro with 2 grommets and 60 oz, in.torque If the Vendor thinks it is ok to make them with only 2 grommets, it must be ok for us to use them in our racers? Do you think we need to change the rules?

kevin

i am all for it, seems way over due, crazy as some seriously fast gliders use them without mishap.....

You can use them for v-tails and if you use two for aileron control, one for each aileron..

From the AMA rules, 8e:

e. Servos controlling the pitch and roll functions shall be of adequate strength for the weight and speed of the aircraft. Except in 1/2A, whenever a single servo is used to control one of these functions, it shall be designed and built to accommodate at least four mounting screws. When two or more servos are used together to control the same function, as in the case of dual aileron servos or the movable tail surfaces on a “V�-tailed aircraft, each of such servos may be of the two-screw variety.

For a conventional tail plane, with no redundancy in servos on a control surface, then 4 screws isn't such a bad idea, I think.

It must be..............but wait...............Hmmmmm............the Vendor?

Kurt

It is not an issue of servo torque, as you have pointed out 60 oz-in is plenty. Just the issue of a screw falling out of the grommet and the servo flopping around unable to push the surface. Last time I checked, gliders don't have much vibration. The rule as written was put into place about a decade ago due to the new two grommet servos that were becoming available then. A recent death of a courseworker was very much in our minds at the time, even though it was not an AMA rulebook event. The committee of 6 that did the rewrite had at least two engineers and one lawyer that thought it was a good idea. What do you think your chance of getting it overturned is?

Many guys these days have been installing the 3102 Futaba servos, they only have 2 lugs per servo. But what is smart, is they guys are using a block of wood (spacer) between the two servos... and some two-sided tape to make the two servos seem as one. I've only seen this on V-tails, but you could do the same in Q40 for rudder and elevator. I personally think that is plenty strong enough when install correctly.

That sounds like it would work well and meet the original intent for mounting.

If you were to look at the Hitec HS-85mg servo for instance, it only has lugs for 2 screws, but is supplied with a mount for each end that locates the lug, and this mount is secured to the airframe with 2 screws at each end, there for the servo is secured with 4 screws ........ Not suggesting using a HS-85 servo, but there may be a lesson of value here.