Extremely hot rear centre shaft
 

There seems to be a common tread with all the DEX410's down the club where the rear centre shaft is too hot to touch after a 5 minute race on wood floor.

Motors range from 6.5 (in mine) to 8.5s in other cars.

This isn't really a problem, but it's puzzling us as to why more than anything. I forgot to check if it happens outdoors :(

Friction in the joint, friction in the slipper, heat build up in the (more heavily loaded) rear diff. Lack of cooling flow round the back of the shell.
Wood floor might make a difference as the diff will be spinning up (and down) more often as the rear wheels slip. If you have lots of carpet/wood changes, the slipper may also be working hard.

D-Joint should make a difference. Or running the slipper (far) tighter.

I doubt its hot enough to cause a problem with anything, except maybe the thread lock and/or lubrication in the rear joint.

the thing is though my car has D-joints fitted. none of the others do and I run my slipper pretty tight anyway.

I think we should just put it down to the lack of proper outdoor air moving through the cars. most of our laps are spend accelerating out of tight corners with only really a 10m straight to move the air.

rear shaft is the highest furthest thing back in the body, so any ambiant heat could be absorbed by it, in theory it is doing the same work as the front shaft as no matter how many times the spur gear rotates both shafts do exactly the same

I found that my output shafts on the V3 are now getting hot. I find the most important thing is to make sure all of the bearings move really free especially in the hubs as as soon as there is any resistance build up there the output shafts, motor and battery temperatures start to rise. I usually use SMD bearings which have one metal shield and one rubber shield as these have less resistance on them than the dual rubber shielded bearings. In fact you could run a fully metal shielded bearing on the inside of the gearboxes for the output shaft for least resistance. The other thing to pay attention to is the gap between the bearings on the output shaft as if the gap is too small it can cause friction on the bearings and if the gap is too big then the pinion can move inside the plastic gearbox case. I also build up the areas of the plastic gearbox case where the bearings fit otherwise the pinion can move around a lot causing heat and damage to the ring gear. I also make sure that the ball joint and ring gear are lubricated with teflon grease and that helps to keep the temperature down. As soon as I feel the temperatures rise I know that it is time for a strip down and clean to make sure everything is spot on.

Nah, as soon as you unweight the front wheels the load in the front shaft will drop to near enough zero, or at least, not very much, whilst at the same time you are loading the rear axle and the prop (and twisting it) its this twisting and untwisting that generates the heat. (much simplified, obv.). So unless you brake and accelerate to exactly the same amount, one prop will always get hotter than the other. The fact that its spinning at the same rate doesn't actually mean its doing the same work. Just that its spinning at the same speed.

Wonder how the DESC410 shafts behave with the extra diff in the system.

Would be interesting (but very dull) to pop some strain gauges onto front and rear props to see what the loads actually are........

I'm going to run a race without a shell on and see what happens. At least this will rule out the ambient heat theory.

410's do appear to have a lot of drive coming from that back end :woot:

It's just friction in the rear joint, the rear joint is at a bigger angle than the front and under more load so will always get hotter than the front.
Fitting a new pin and bushing helps a lot as does a little bit of black grease.

Hi
Check oil levels in diff! If they are low have found this can build uP heat
Also you are running on a wooden floor. This will cause more wheel spin and wrk the drivetrain harder causing heat.
Oli