Easier to have you run a little test than for me to explain.
Rotate the right tire so the CVD drive pin and outdrive slot are vertical. Move the control arm up and down and note to yourself how much pressure it takes - you'll feel the spring's resistance and that's about it. Now hold the wheel still, and put one finger on the spur gear and rotate it a bit so there is tension in the driveline, especially between the outdrive and CVD. Try moving the control arm up and down again -- it should take much more force.
The bones have friction when they move in and out of the outdrives. The real concern here, however, is not so much how the friction affects the car in stasis, but rather the control the friction gives the driver on the track. When on power this friction adds traction and stiffens up the rear suspension. Off power the car will be softer.
Seems obvious; however the degree to which a driver can make use of this around the track really helps lap times. IMHO, Ryan Cavalieri is best in the world at landing jumps. Watch his control as the car approaches the ground. He uses the throttle to get the exact amount of stiffness and forward drive he wants for the landing.
As the outdrive wears, the friction changes, so the car performs differently from one race to the next and you are wondering why. When you see them start to wear, it's time to replace, usually two or three race weekends with the AE steel ones. And, about every other outdrive replacement, be sure to replace at least the pin in the bone, if not the whole bone. The pin is replaceable easily if you have a small press, not so easy with a hammer. Paul buys hardened rods from a hardware supplier and cuts off pieces to fit. The bones are available separately from the whole CVD kit.
Losi's old outdrives (the big ones used on all their cars up to the 22) are a slightly different story. Those outdrives/drive pins are big enough that Losi spent a lot of time trying to reduce the friction there, as too much can make the car 'catch' over bumps. The Losi plastic outdrives obviously have less friction than the steel, and the ultimate reduction of friction was the 'BK Bone', which used small ball bearings over the drive pin to reduce nearly all this friction. With the smaller outdrives/drive pins on the 22, I think Losi has quietly admitted that AE's design is superior in this regard.
|