I'll add my little input to what carrellh posted.

All manufacturers have torque and other ratings with the servos that they sell. usually, if you are going to build something that is basic, that is, not 3D or puts heavy demands on the elevator, rudder, or ailerons, the servo you choose won't make any difference except on your pocketbook.

Normally, typical applications for 40, 50, 60, 70, and up to about 90 size models will work just fine with the basic, standard servo. You can increase torque, for example, using a step higher servo, and that can be noted by the specs showing a higher oz-in (ounce inch) or kg-cm (kilogram centimeter) rating. Also, you can increase torque and speed by using a 5 cell (6 volt nominal) battery pack over a 4 cell (4.8 volt nominal) battery pack. Before you do this, though, make sure the specs say that it will work with a 6 volt pack.

Ball Bearing servos will most likely last longer than a bushing type servo, however, that difference in time may be insignificant compared to the use it will get. For instance, a bushing type servo might hava an average life expectancy of 1000 hour life span where a ball bearing servo may have a 2000 hour life. That's a lot of flying even for the standard bushing servo. If it is worth the difference in price to you, then knock yourself out. If it becomes a matter of cost, then the standard servo may be right for you.

I have a mixed bag of servos. Some hitec micro servos, some Airtronics basic, some ball bearing, and some ball bearing coreless servos. I also have a few Futaba basic servos, as well as the JR/Spektrum servos that came with the radio, they call them hi-torque digital, but the cost per servo, if bought separately, is around 30 bucks each, so the digital part is probably a bit of a stretch as compared to the real digital servos that go for over a hundred bucks each.

In addition to your tower hobbies link, take a look at Horizon Hobby at www.horizonhobby.com and take a look at their servo selection. There are other sites that have real good deals on servos. Someone posted a site that has the Airtronics 94102Z servo on sale for something like $9.99 each. And that is a fine servo (I have about 12 of them).

CGr.


CGr.