Direct Drive to Diff E Revo Build - Page 20 - RC-Monster Forums

sikeston34m · **True Direct Drive -** 12.14.2007, 11:43 PM

Now here's a project that's going to take some Engineering.

All I need is 3 more motors and figure out how to attach them to the A Arms.

This is a regular E maxx tire that is 5.75" tall.

BL_RV0 · 12.15.2007, 12:48 AM

THAT IS SO EFFIN COOL!!!!!!! steering will be an issue tho....

aqwut · 12:56 AM

LOL, is that the same motor I have Sikes?..... LOL... too bad it wouldn't work in reality.... but man.. it would be Real awesome..
you really gotta test the torque of that motor... it's cray powerful...

Matthew_Armeni · 12.15.2007, 01:18 AM

How about 2 motors, sideways between the bulkheads? Then you could attach the driveshafts to the motors. It would cause a lot less headaches design wise I think. With 4 motors being in the tires you have to worry about durability, mad unsprung weight, gyro effect, much too difficult. Maybe for a large scale onroad though.

sikeston34m · 12.15.2007, 01:18 AM

Quote:

Originally Posted by aqwut

LOL, is that the same motor I have Sikes?..... LOL... too bad it wouldn't work in reality.... but man.. it would be Real awesome..
you really gotta test the torque of that motor... it's cray powerful...

Yes I believe it is the same one you have. I had to get me one too.

I'm not so sure this wouldn't work. It would be a very heavy and expensive setup though. Not to mention that it would use 14 pounds of motors.

But a cumulative Wattage output of 28,000 watts should be enough to justify some of that weight. LMAO

I have test ran it in my hand on 4S Lipo. It was all I could do just to hang onto it, and that's spinning it really slow.

What have you tried it on so far? I'm thinking an Electric Bicycle that will carry me around.

ilpufxit · **Two words -** 12.15.2007, 10:18 AM

Unsprung weight.

aqwut · 12.15.2007, 11:20 AM

have one in my BlackJack 55" Cat boat (Currently Being Re-Painted)... planning to put another one on another GST 7.7 Roller... I almost have enough parts to build 2 more GST Rollers... but I'll need to get my hands on another 40.160WK.. I'd rather wait until Lutach over there get's that Custom HV ESC made...

sikeston34m · 12.15.2007, 12:38 PM

Quote:

Originally Posted by aqwut

have one in my BlackJack 55" Cat boat (Currently Being Re-Painted)... planning to put another one on another GST 7.7 Roller... I almost have enough parts to build 2 more GST Rollers... but I'll need to get my hands on another 40.160WK.. I'd rather wait until Lutach over there get's that Custom HV ESC made...

I have a feeling what you will run into on the GST conversion is issues with building diffs that will hold up to that kind of power.

Get us some vids of the boat and the GST if you can. Can you actually get a prop for the boat large enough to make use of the torque this thing can make?

Unsprung weight. Let's talk about that. A Motor in each wheel setup would have a center of gravity that would be unbeatable. The bearings in this motor are HUGE and appear to be up to a good amount of abuse. Not only that, the power isn't even being transferred through the output shaft anymore. The output shafts new job would be to just hold everything and keep it spinning true. It's now an "axle shaft" more or less.

With advanced Electronics and programming, we will have independant traction control. A slipperential would be a matter of programming. So would "diff slip".

Diff slip would be a matter of limiting amp draw based on steering angle. An ESC controlling this would become more of a PLC.

I really look for this to become a reality with full scale on road Electric Cars in the future.

The drive motors will be sensor based to smooth things out and completely eliminate cogging and erratic behavior.

No drive train! Can there be a more efficient way? How about one that's going to hold up longer? About the only "wear item" in this is the bearings in the motor.

ilpufxit · **Unsprung weight -** 12.15.2007, 12:51 PM

For a crawler, you're absolutely right, keep the cg low. For speed though, your suspension can't keep that much weight on the ground going over bumps, too much momentum. Could work well on a totally smooth surface.

I like the idea of motors where the diffs go, 2 motors opens up a whole range of control options.

sikeston34m · 12.15.2007, 12:59 PM

Quote:

Originally Posted by ilpufxit

For a crawler, you're absolutely right, keep the cg low. For speed though, your suspension can't keep that much weight on the ground going over bumps, too much momentum. Could work well on a totally smooth surface.

I like the idea of motors where the diffs go, 2 motors opens up a whole range of control options.

Aaaah, I see your point. On road would be alot different and would work much better.

I like the idea of putting motors where the diffs go also. Aside from redesigning the bulks to hold them, this is going to be like running locked diffs in the front and rear.

How do we use front and rear motors, and retain our diff slip?

We've talked about an inline with the shaft slipper clutch here several times. How about instead have a centrifigal clutch in the wheel hub? The hub would have to spin up some before it would gradually apply torque to the wheel rim. Let's make this run on a large one-way bearing so when we put on the brakes, it will stop.

This setup would only "cushion" in forward, but who runs races in reverse?

ilpufxit · **Diffs -** 12.15.2007, 04:32 PM

Locked diffs would be a problem for sure. The whole concept of direct drive really gave my little brain a stretching but now that I've thought it through, I'm thinking maybe two outrunners back to back in the same center diff location could use a fully electronic system for optimal everything, ie traction control, stability, ABS, the works. It could be a quantum leap in controllability. Is there a software engineer in the house?

DrKnow65 · 12.15.2007, 04:42 PM

servo mixing could be used to drive the front motor harder when turning as the front wheels spin more rpm in a turn. Assuming a 3 channel remote is used. ch1=steering, ch2= rear esc, ch3= front esc.

sikeston34m · 12.15.2007, 06:43 PM

I'm finding the limitations of the bearings in the truggy diffs.

With the spiral cut gears of the 4.3:1 ratio, the pinion not only side loads the bearing, but it also pushes or pulls against the bearings.

I've been using steel ball bearings and they aren't holding up to the increased torque levels of my setup.

I could hear the diff Pop occasionally in the rear under hard acceleration. I took the diff back apart, and found alot of slop in the bearing closest to the pinion. I swapped positions with the two bearings, reshimmed to take all the play out and it worked perfect.

Now about 4 runs later, it's doing it again. On 6S, it will do 60mph+ and top out very quickly. With NO slipper, the setup is able to transfer all the torque that the motor will make. Which is alot!

A needle bearing with thrust bearing type qualities would be ideal, but I can't find any in this size. 8x14x4mm.

Is Ceramic Nitride the toughest out there in a ball bearing? like this one:
http://www3.towerhobbies.com/cgi-bin...?&I=LXPVB1&P=7

I've heard they are.

@Lincpimp - You need to consider this on the setup you're looking at. Tough Diffs are a must.

zeropointbug · 12.15.2007, 07:03 PM

Wow, that is deadly looking! Use that with a speed record! I have mentioned the wheel motor idea a few times on this forum, but yeah it won't really work with these monster trucks. MAYBE, smaller on road cars... but they would need a very high power density to keep the weight down in the wheels, like someone said "unsprung weight" is a killer.

A few companies are doing wheel motor for full scale cars however, with GREAT results, works much better than motor/tranny/driveshafts.

About the diffs Sike.... I think all pinions have thrust on them when loaded, these spiral cut gears may just have more pressure is all. I don't really know what the best bearing are in these sizes? Sorry.

sikeston34m · 12.15.2007, 07:20 PM

Quote:

Originally Posted by zeropointbug

Wow, that is deadly looking! Use that with a speed record! I have mentioned the wheel motor idea a few times on this forum, but yeah it won't really work with these monster trucks. MAYBE, smaller on road cars... but they would need a very high power density to keep the weight down in the wheels, like someone said "unsprung weight" is a killer.

A few companies are doing wheel motor for full scale cars however, with GREAT results, works much better than motor/tranny/driveshafts.

About the diffs Sike.... I think all pinions have thrust on them when loaded, these spiral cut gears may just have more pressure is all. I don't really know what the best bearing are in these sizes? Sorry.

What diffs are you running in your 7S1P A123 setup? Ever had problems?

I know that truck really runs!