softbear

A lot of companies selling the tuning to reduce rotating mass: ligten diffs, CVDs etc. If I buy all of this I will save nearly 20g of weight. Not to much.

But what if I simply make center driveshaft (and diff) rotate slover? Say I have 46/16 spur/pinion (2.875 ratio) and cone gears 43/13 (3.3 ratio) drivetrain with total ratio 9.5.

What if I reduce rotation speed of center drive shaft twice? It will reduce kinetic energy of rotating center diff and shaft 4 times! It like make it 4 times lighter! But I will have to make ratio of spur/pinion 5.7 and cone gears 1.66 preserving final ratio 9.5. Lets imagine I can.

So the main question is: If there is such way reducing inertia of center diff and shaft, why don't manufacturers of RC models use it? Is there any drawbacks?

DsWright

iTrader: (5)

Is it worth it though? cars these days have so much more power than needed, especially in 1/8th, that would lowering the rotating mass improve laptimes? Im not thinking it would. There is no "stock" 1/8th class that i am aware of.

Want to lower rotating mass? look at your tires. Some manufacturers and compounds tires are MUCH heavier than others.

you could save much more at the tire than in the rest of the drivetrain imo.

But would you also need to beef up your center shafts? they would be subjected to much higher torque forces and i think cvd's or bones would be subject to greater wear even though they spin less.

Davidka

iTrader: (86)

There's not much real gain in the small diameter parts (cvd's, out drives). If you could identify lighter wheels and tires that would make a much more meaningful difference.

I saw a guy achieve what you're going for by using a pair of out runner motors and eliminating the center diff and gear reduction there all together. He "diff'd" it by using dual linked sped controls and their torque/amp limiters somehow. It ran really well but it was made with airplane parts that didn't do so well with dirt and impact.