Direct Drive to Diff E Revo Build
 

I'm trying something different here. I thought I would share this with you guys. I'm sure I'll be learning alot through out this build. With the success I've had with outrunners and the E maxx, I couldn't resist doing this.

I found the weakest link in the E maxx to be the transmission, even with upgraded parts just short of aluminum case and all steel gears. SO........let's eliminate the transmission altogether and go with the Revo. Less parts to break, we've saved some weight, and hopefully this will be tough!

The Motor I've chosen is the AXI 4130/20. It's stator is 41mm in diameter and is 30mm long. It is a hoss of a motor. In Airplane use, it can swing a 20" prop directly and fly an airplane that weighs 15.4 pounds! Let's see how well it can "fly" a 9 or 10 pound Revo. :yes:

The Motor weighs 409 grams. It is 50mm in diameter and 65mm long. It can be fed with up to 8 Series Lipo. It can handle 40amps continously at around 30 volts, and 55 amp bursts for up to 60 seconds(almost 1900 watts!). The 4130/20 wind is 305kv. Axi also has a 4130/16 that is 385kv. I chose the lower kv for the starting torque. I fear cogging on startup, this will help. If cogging isn't an issue, I can step up to the 385kv version.

To help with heat issues, a cooling fin assembly has been added to the endbell. In testing on 4S Lipo, It really moves a good amount of air.

I'm going to go with the stock diff ratio for starters. If cogging is a problem, I will order the RCM buggy gears. They are offered in 4:1 and 4.3:1 ratios. The 4.3:1 ratio is VERY close to the E maxx in 2nd gear. This would require spinning the drive shaft much faster to get the same top speeds though.

The motor shaft is a STOCK Revo tranny output shaft. I simply removed the steel hump from the middle to create a smooth 6mm shaft that is ready to accept the Revo driveshafts. The length worked out perfect with 1 or 2 mm to spare.

I'm not done with it yet, but I will update as the build progresses. Let me know your thoughts.

Here's a few pictures of the Motor mount/lower skid plate.
http://i160.photobucket.com/albums/t...m/DSC06629.jpg
http://i160.photobucket.com/albums/t...m/DSC06631.jpg

that looks like an awsome projecT!

what are you going to do to keep rocks out of the motor? or sand or something?

Others have done this for 1/10 4wd truck conversions, but I haven't seen it attempted for a MT. As long as the motor can hold up to the extreme abuse, I think it's awesome!

It should have more than enough potential, i am curious if the fan is needed or not.

I love it when you have got a little luck in converting stuff, like the shaft being a 1:1 fit with a little modification. That's awesome.

cool..

http://www.modelmotors.cz/en/img/konverze.jpg

are these high-end outrunners?

My original plans were to seal the leading edge of the motor mount to the under side of the frame. Then put twin 40mm fans on the top side of the chassis. Positive Air pressure and the air intake being on the top of the chassis would insure that the cleanest air possible would go through the motor.

Once I started building the motor mount, the challenge of just making it fit kinda put all that in the background for now. I might go back and rebuild the mount and use the old one as a template. but for starters, I'll go this way.

Yes, these are high end outrunners. Construction is VERY good. Neo magnets, and twin locking set screws stand out. Triple bearings too.

and made in Europe, which should be easy to lay hands on here..
testing testing 1 2..

how much do those outrunners go for?

Is that fan aluminum or plastic?

i've seen them for 130 bucks on the net.

http://modelmotors.cz/ is the manufacturers website. They are around $130 on the net.

The fan is aluminum, much to my surprise. When I ordered it, I was expecting plastic. Cool3 is the manufacturers part #.

Price is definitely not bad. Would make a nice drop-in for a emaxx. Hmmmm. :)

I considered this setup for an E maxx.

I can't speak for all the aftermarket chassis's out there, but the ones that use frame rails similiar to the stock configuration won't work. The frame rails are 50mm apart from each other. That's the same as the diameter of this motor.

Also, the E maxx tranny output shaft is 6mm in diameter, but it's only 68mm in length. It's too short.

The Revo output shaft could be used with the E maxx, but only with the stock center driveshafts slid almost all the way in. I don't think the stockers would hold up to this. I question weither or not the beefier Revo shafts will hold up.

But in the Revo, we have retained stock lengths so MUCH tougher CVD's can be installed. I'll see how well the stock ones hold up first though.

Good luck sike, I had good success with my POS redcat that I had the outrunner in, I chose the motor so that I could use the stock drive cups from the original trans, not much thought was given to kv, thus the need for tiny tires, LOL.

What esc will you be using? Quark for the timebeing, or something that can handle 8s lipo? Startup adjustability is the key with these outrunners. The quark on its highest settings work well, but it would have been nice to have and adjustable throttle curve like the MM. I found that very small throttle inputs caused cogging, but a little more throttle at startup solved that and it would roll very smoothly after that. Ramping up the throttle curve for the first few increments would ave solved that issue. Maybe I was using too small of a motor and too high kv. A 650kv would have worked better than the 833 and maybe a larger diameter would have helped startup.

Good luck and keep posting, I have another revo that may get something like this!!!!:wink:

Whatever happened to that Redcat anyways? Do you know what diff gear ratio that it had?

I'm going to start out with a Quark 80amp. To run 40+mph with this setup, I need to spin the motor at 7500rpm. That's going to require 6 Series Lipo. I'll try it on different battery setups. I see myself probably settling on 6S2P A123 packs, but I have alot of other Battery possibilites.

The battery trays that I'm building are rather large to give me plenty of room for ample batteries. The Battery "Area's" will be about 2 1/4" x 2" tall x 7" long. I can easily fit 10S1P A123 in there or a number of other Lipo configurations. I'm looking at other ESC options now though. I want a high voltage car controller that gets along with outrunner motors.