Slipperntial my way. Maybe.

[Hickoryhead]

OK for all you technical genesis’s out there I have been having some thoughts that I need verified. As most of you know I have a machine shop at my disposal. I have been thinking of making my own version of a slipperential. Something I am trying to work out in mind brain needs some help verifying details with gearing. Theoretically when dealing with gears, for every gear you add into a serious of gears you lose elements such as power and\or torque. It may not be a lot. Maybe as small as 5% or maybe greater depending on the material the gear is made from. I am thinking the lost elements are caused by flex or other factors. Is my thinking off? I know that the number of teeth on each gear matters but put that aside for this.

The reasoning behind my thinking is why can't you mount a gear say the size of a spur gear right onto a driveline. Then add an additional gear with a slipper kit right onto the motor shaft? This is doable. Take an Emaxx transmission for example. You have 5 gears from the pinion to the driveshaft. If you can take out 3 of the 5 gears theoretically there will be a gain in power and\or torque. But is the gain worth it? More power and torque equals more broken parts. What are some of your thoughts?

The loss is from friction in both the bearings and gears. Then the energy need to spin up the extra mass.

If keeping the overall drive ratio the same. The main thing I see you gaining is some lightness (which is always good) and a slight increase in acceleration because it will spin up a little faster.

Is it worth it... That depends on the rest of the truck. There are other areas I would look at to gain some speed. If there are other reasons behind the build like you want a clean look, adding lightness, or just like to have a unique truck then go for it. I have more fun building so, I would do it just because I could.

[zeropointbug]

Basically, how many gear 'meshings' you have, the gear width, and the mass of these gears is what determines the losses. The smaller in diameter you make these gears, even with the same weight gear, the 'momentum' will be less and therefore less energy wasted. You simply what to keep a transmission as simple as possible, and as small as possible, while maintaining a healthy 'durability' factor.

But, I seem to be bouncing around on the topic, so I will stop now.

[Hickoryhead]

Maybe I missed something. Why did Mike build a V1 slipperntial?

[zeropointbug]

The V1 Slip.? He designed and built that for racers... It almost prevents wheelies, and you will get very high planted acceleration.

[Finnster]

Basically truggies/buggies to have their spur gears mounted directly to the center driveline (ie the centerdiff in their case) eliminating the transmission. You only really need a tranny if you wish to have more than 1 gear, otherwise you aer just stacking on gears (and increasing CG) for no good reason.

The sliperential basically eliminates the tranny and gives a MT (this case the Gmaxx or G2R) a buggy/truggy like drivetrain. Also, nitros have a clutch, so having a direct drive isn't that much of an issue, but given the solid pinion and huge TQ of a BL motor @ 0 rpm, its very helpful to have some sort of slip to not kill the driveline (esp as hardened pinions are rare, so plastic spurs are needed) and wheelie everywhere.

As an aside (I'm not trying to bust balls any ) but I've noticed you often spell "series" as "serious". First noticed it in a battery post. Just makes for a funny reading. Like "these gears are not screwing around, they are in serious.."

[Patrick]

I'd say they used idler gears in the e-maxx transmission, because if they didn't then the input shaft would sit about 20mm lower. Good for center of gravity, but the 66t spur gear would be hitting the chassis and probably drive shaft. The motors might also sit too close to the batteries, making them too hard to get in and out.

You could put make a mount for a center diff and put that in the maxx, but the problem is that the motor will probably be sitting so low (this if if you put the motor in the center, above the diff with the pinion going straight onto the spur) that it could hit the chassis. Depending on what chassis you have you might be able to make it work, but could be hard.
Do you want it to have a center diff or constant 4 wheel drive like the maxx transmission.

[squeeforever]

Originally Posted by Patrick

I'd say they used idler gears in the e-maxx transmission, because if they didn't then the input shaft would sit about 20mm lower. Good for center of gravity, but the 66t spur gear would be hitting the chassis and probably drive shaft. The motors might also sit too close to the batteries, making them too hard to get in and out.

You have to take into account the fact that without the idler gears, the ratios would be different. So it might not be a 66T spur. Also have to think about the fact that the upper shaft gear size would probably be different.

[lincpimp]

The idler gear has no effect on the ratio in the tranny. Emaxx 2nd gear has an 18t top gear and a 31t bottom gear. The ratio is 1.7222222 = 31/18. Because both gears engage the idler it spins at the same rpm. This is true of any 3 gear tranny. The idler is only used to space out the two gears for packaging reasons.

[Finnster]

Originally Posted by lincpimp

The idler gear has no effect on the ratio in the tranny. Emaxx 2nd gear has an 18t top gear and a 31t bottom gear. The ratio is 1.7222222 = 31/18. Because both gears engage the idler it spins at the same rpm. This is true of any 3 gear tranny. The idler is only used to space out the two gears for packaging reasons.

Its true it has no effect on ratio, as both gears are directly tied to the idler, but nearly every tranny I've seen has an idler, so was wondering if there is some engineering purpose other than a spacer. They do reverse the direction of rotation as well. Many brushed motor have timing in the end bells, so perhaps its there to make sure that the rotation is the same direction as travel, instead of requiring an unconventionally built brushed motor. Obviously w/ BL or 0* this is not needed.

[zeropointbug]

I agree, it's just used as a spacer in almost all applications. I don't think it has anything to do with the brushed motor direction in direct drive apps, because you COULD switch the motor around to the other side of the tranny... simple design change.

[squeeforever]

Learn something new every day...

[lincpimp]

Yeah, I figured out the idler thing when I first tried to figure gear ratios. Had some very strange numbers before I realized the idlers purpose!!

[squeeforever]

Running a 1920 isn't that unheard off. Sjcrss was running a 1920 in his VERY heft Maxx monster he use to have.