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.

I have run that motor in a mostly scratch built truck for over a year now with fantastic results! I am running the 515 KV motor. It will run up to 10S of you feel the need. But, on 10S (heck even on 8S) it has enough torque to break the plastic shafts. You will probably find yourself going to CVDs in no time.

Oh, no cogging worries. That motor is a freakin torque machine!

Matt

Cool project.. and I do agree with you that less parts the merrier.... I was planning on doing something similar to my GST..

this outrunner... on 12S...
http://www.hobbycity.com/hobbycity/s...idProduct=5139
1.57KG
http://www.hobbycity.com/hobbycity/s.../C80-100-A.jpg
or this one, so I ordered both..
http://www.hobbycity.com/hobbycity/s...idProduct=5140
1.23KG
http://www.hobbycity.com/hobbycity/s...g/C80-85-A.jpg
that's an awesome project.. Keep us posted...

Got any pictures? What diff gear ratio? Tire size? More input please.

@Aqwut

I've been looking at both of those outrunners more thinking about an Electric Bicycle.....LOL

They are HUGE! How are you going to deal with the 12mm motor shaft or the 10mm motor shaft of the other one?

I'm sure either of those are power houses!

When you see the mounting tabs easily accept M5 or M6 screws...you know its a hell of a motor...

sikeston, looks great thus far. I'm very curious to see how it turns out (vids are a must!).

Wow! Nice work Sike indeed! Congrats on the project progress, I am planning a direct drive outrunner project myself with my other FLM maxx chassis. I was thinking of either a E-flite 'Power' outrunner, or one of the new Scorpian motors.

Aqwut.... OMG, and anything holy! I have never seen that motor before!
That thing must have a 10Kw rating, no doubt?!

It looks like the guy was trying to give it a test spin and broke his thumb! :lol:

I've been checking into the Scorpion outrunners too. The Axi 4130/20 has more torque than the Scorpion 4025 series. 1mm larger stator and the stator is 5mm longer.

However, there is talk about a 4035 series in the future for Scorpion. That would beat the Axi 4030's as long as it's about the same length.

It is a belt driven (or was untill I put a different power system in it) transfer case running TXT axles.

Matt

Nice Machine you have there. :yes:


What battery configuration and ESC were you running?

What kinda top speed were you looking at?

It's ok if it breaks the plastic shafts. Actually, that's a good sign. I want to run about 50mph top end, get there fast, and build it so it doesn't break parts.
I'll be looking at upgrading the diffs, and cvd's for sure.

Not sure of the top speed. It is not gear for top speed, though. As a straight axle truck, it does not handle speed well.

Here is alink to another thread with pics of the latest upgrade to it.

Enjoy! http://www.rc-monster.com/forum/show...8&goto=newpost

Matt

The old redcat is sitting on the shelf. I have the quark 65 in my ls10 running a hacker 13l at the moment on 5s lipo. Not too sure on the diff ratio, but it was 3:1 or 3.25:1, something like that. I ended up using the new traxxas bandit anacondas on hpi wheels to get the gearing right. It was driveable on 4s and ran nicely. I may get some sort of nitro shaft driven on road car and try it out with a mm on 4s. Not sure how the MM will do on an outrunner, but we will see. I may post a thread asking if anyone has a tc they want to let go cheap, maybe a ntc3 or some sort of flat chassis shaft drive vehicle.

Well that's the thing about gearing and cogging. If you pass that "sweet" spot on the way to higher gears, it will cog on start up and the motor will run hot.

The reason why I chose the 305kv motor is, I'm dealing with 2.85:1 diff gears at the moment. More Torque will be required to pull the higher gearing.

The truck will surpass 40 mph with the diff pinion spinning at 7500 rpm's.

It's gonna take 24 volts to do that. I plan on perfecting the setup with no cogging on 6S Lipo or less. The maybe bump it on up.

You have a VERY nice truck there Matt. Congratulations on all that custom work. :yes:

Sorry to pop your bubble Linc, but the MM does NOT like outrunners at all. It has something to do with their software OR their switching rate. You can try it, but it won't work. Cogging.........Cogging.......confusion..........C ogging........Thermal shut down was my experience.

It appears to me that the Kontronik line of controllers work well with the outrunners. Judging from what I've read and seen in the forums.

Isn't there some kind of rule-of-thumb that states the motor has to spin a certain minimum percentage of its kv rating for the ESC to get the proper back-EMF pulses? Don't know if the same rules apply to outrunners, but it may be something to think about as far as cogging is concerned.

And HOLY COW that's a big motor! You plan to sit on your vehicle while you drive it? :smile:

I think the MM will work with some, but not all outrunners. If I remember correctly, Serum posted a video of his G2R with a MM and outrunner and it didn't cog whatsoever.

You know, come to think of it, you could be onto something Brian.

JohnRobHolmes uses them with his outrunners and Rock Crawler setups. Way LOW gearing but they work for him.

Perhaps the Quark has a different "kick in the pants" startup routine. I'm not sure.

The Quark definitely has a different startup routine than a MM. Actually, I made a thread about that a while back noting the differences.

Also seems like the quark, when turned all the way up, can really provide some starting power. I had mine set for the outrunner in the redcat and then moved it into my ls10 with a feigao 12l on 5s lipo and it would lift the truck completely off the ground and flip it over. And that was with smooth throttle input, no stabs! I turned it down quickly, as I could see that I would be snapping some driveline components soon!

Yes, but the outrunners have higher potential back EMF than a inrunner for given rpm... right? :smile:

linc: The difference I noticed was with what happens if the motor doesn't get started (geared too high, too much load, etc). The MM progressively adds more and more power until it starts. While good to a degree, this could end up causing the ESC to go up in smoke if there is too much trouble getting that motor started since a motor can pull a LOT of current in its stalled state. The quark OTOH simply keeps trying to move the motor, but not with any more power than the "start power" setting. IMO, this is safer for the ESC.

ZPB: Yeah, that's why I wasn't sure if the same percentage applied to outrunners. I'm sure there is still some kind of value, just different. Makes sense that the motor would have to spin a certain speed to generate the needed EMF signals since a coil induces a voltage while in motion only.

I run a 14pole outrunner in my rock crawler on 3s Lipo using a Mamba 25. The motor's rated at 45amps continuous, and the little Mamba 25 runs it very well. Granted, the gearing is low, but I've run the truck geared for higher speeds as well. However, the Mamba 25 doesn't like that so much, and does sometimes have difficulty starting the motor. I blame that problem on the Mamba 25 being so small...

I can tell you that the HV110 has no cogging and runs phenominal with outrunners. Part of that is due to being designed for aircraft use (the brakes suck, though).

If you do not mind parting with some coin, the MGM Com Pro is the best running car ESC I have ever had. They have the best start up, are reverse capable, and run cool. But, they are super expensive and tough to get serviced if need be.

Matt

I find that outrunners don't cog too often, except when using some cheapo ebay ESCs.. Seen the size of that motor, had a lot of batteries coming.. and couldn't resist picking one up.. and as for the 10mm and 12mm shaft, I now have a taig lathe.. so I can do something with it....

Sikestorm, that truck you have is just beautiful man..

what are the maximum RPMS an outrunner can take?.... about 12000rpm?

I got lost when you guys started talking about EMF pulses....:intello::surprised:

It's more of a sine wave than a 'pulse', but while in operation, it is probably distorted somewhat... if it were running as a generator, then it would for surely be a sine wave.

You must be looking at Modman's truck Aqwut. I haven't shown my truck here yet. LOL

Yes, around 12,000 max. rpm's for this style outrunner. There are outrunners that are high speed though capable of 40,000rpms.