Originally Posted by
heretic
What saddens me a bit is to think that several people with actual engineering degrees will read this thread and not even take five minutes to weigh in, for or against (not that things have to be black or white of course.)
Well guys I have an engineering degree and it really isn't worth that much in this conversation, especially if you want an actual answer, but I will tell what I know.
The Short Version:
At the RPM and loads we place on RC cars, and the fact that the driveline of an RC car must be massively overbuilt relative to its operating load to survive crashing it into things like solid barriers, the advantage of shaft drive over belt or vice-versa is very small, if it exists at all.
The Long Version:
We use toothed belts at low tension and low load in RC. While these are the most efficient belt type these belts operate well below their max strength, which is actually bad for efficiency as belts reach max efficiency at near 100% rated load capacity, but not so much as to be a real driver of meaningful power loss. I personally think that belt drive car manufacturers need to run the internal ratio of the car closer to 1:1 as larger pulleys at the spur gear will be slightly more efficient (they learned this in bicycles), but that is getting into splitting hairs.
In the Awesomatix, the shaft drive in-line with the motor is the most efficient means of getting power to both ends of the car. It has very low inertia to get started and little loss at speed, but at both ends of the car there is a 90 degree power transfer from the longitudinal shaft drive to the axles using straight-cut bevel gears, which again is the most efficient way possible but is not perfect. Whenever this happens there is going to be a loss in power, in the usual places like in the metal-on-metal slide at the gear face and possibly in other areas like vibration from the gears or even a slightly out-of-balance driveshaft which just doesn't occur in a belt drive. Also, in the Awesomatix there is an internal gear reduction of about 2:1, most likely for chassis twist reasons and that is also not optimal, as bevel gears are most efficient at 1:1.
In the end, all else being equal, both methods of power transfer are over 95% efficient in operation. Any inherent chassis advantage the Awesomatix has is in its engineering, suspension, exceptional construction, and the exceptional drivers who wheel it... not an inherent advantage of shaft-drive. Really, if shaft drive was all it took, why would anybody make a belt drive car anymore?