Direct Drive to Diff E Revo Build

[MetalMan]

Originally Posted by sikeston34m

The MT2 looks like a pretty awesome truck. Are there aftermarket 1/8th diffs available for it also? I'm gonna check that one out a little more. Only weighs 5 pounds! I like that!

In considering other trucks for direct drive conversion, just remember what we've ran into on the cogging issue. I think that line that you can't cross is somewhere about 4 inches of roll out per turn of the motor. Vehicle weight affects this I'm sure.

But more so, I believe it also has to do mainly with the level of EMF pulses that the ESC MUST get from the motor to start properly. More on this later.

The MT2 is pure 1/10 scale, no optional 1/8 diffs. The diffs are actually a weak point on it, even with the optional hardened diffs on the 18SS kit (which are the ones I started with). However, aluminum diff housings have fixed that issue for me, in combination with the hardened diff gears.

My motor is a KMS 4120/06:
http://www.hobbypeople.net/gallery/108521.asp
I get these at a discount 'cuz I work there. It uses a 6mm shaft, so I have a 6mm steel rod that I will turn down to 5mm where the dogbone cups attach.

Only problem that I have found with the MT2 so far, is that the stock chassis is pretty narrow.

[sikeston34m]

Originally Posted by MetalMan

The MT2 is pure 1/10 scale, no optional 1/8 diffs. The diffs are actually a weak point on it, even with the optional hardened diffs on the 18SS kit (which are the ones I started with). However, aluminum diff housings have fixed that issue for me, in combination with the hardened diff gears.

My motor is a KMS 4120/06:
http://www.hobbypeople.net/gallery/108521.asp
I get these at a discount 'cuz I work there. It uses a 6mm shaft, so I have a 6mm steel rod that I will turn down to 5mm where the dogbone cups attach.

Only problem that I have found with the MT2 so far, is that the stock chassis is pretty narrow.

What's the diff gear ratio and the tire height on the MT2?

Hey, that looks VERY much like my motor. Let me give you a word of advice here. When you get the motor, remove the endbell. set it on a table and wick some RED locktight in around the stator and the bear holder. Let it sit for a day or two, then dry up what doesn't soak in. What does soak in, gets hard and creates a VERY secure bond in the absense of oxygen. Some outrunner manufacturers don't loctite both ends of the stator. This can spell for disaster if the stator breaks loose. Check it, it may already be done.

There are some outrunners that have a 5mm shaft that would be suitable, but it looks like you found a great one. I might have to give that one a try.

[Revracer]

im amazed. how about a video? this is amazing man. what speed and torque do you get with it? what run times and what is the over all price tag on the conversion?

[sikeston34m]

Originally Posted by Revracer

im amazed. how about a video? this is amazing man. what speed and torque do you get with it? what run times and what is the over all price tag on the conversion?

Thanks.

I'm gonna be posting video's with various battery setups.

I'm working on getting the diffs installed right now. I'll post data as soon as I get it, but it's gonna be good!

Oh, on the price tag thing, I'm not really sure I want to add that up!

[Revracer]

way too much for me then... can this motor be bolted on wit ha tekno kit? bolt in liek a standard motor?

[BL_RV0]

Originally Posted by Revracer

way too much for me then... can this motor be bolted on wit ha tekno kit? bolt in liek a standard motor?

no. it cant.

[MetalMan]

Originally Posted by sikeston34m

What's the diff gear ratio and the tire height on the MT2?

Hey, that looks VERY much like my motor. Let me give you a word of advice here. When you get the motor, remove the endbell. set it on a table and wick some RED locktight in around the stator and the bear holder. Let it sit for a day or two, then dry up what doesn't soak in. What does soak in, gets hard and creates a VERY secure bond in the absense of oxygen. Some outrunner manufacturers don't loctite both ends of the stator. This can spell for disaster if the stator breaks loose. Check it, it may already be done.

There are some outrunners that have a 5mm shaft that would be suitable, but it looks like you found a great one. I might have to give that one a try.

The diff ratio is 38/13 (2.923:1). For now, my tire height is 3.5" (Proline 2.2 Road Rages).

I haven't taken the motor apart yet since this brand uses snap wrings that are difficult to remove. But when I do, I'll put red loctite on it as you mentioned.

[sikeston34m]

Originally Posted by MetalMan

The diff ratio is 38/13 (2.923:1). For now, my tire height is 3.5" (Proline 2.2 Road Rages).

I haven't taken the motor apart yet since this brand uses snap wrings that are difficult to remove. But when I do, I'll put red loctite on it as you mentioned.

3.5 x 3.14 = 10.99 (Tire Radius)

10.99/2.92 = 3.76 inches of roll per motor revolution

This configuration should work! I'm sure you will be able to increase tire size somewhat since it's so lightweight.

The AXI uses those snap rings also. I use a pair of small screw drivers. First pry the ring apart, then starting on one side, pop it up out of the groove. Then using both screw drivers, work all the way around gently prying up until it's completely out of the groove.

I don't think I've ever seen a pair of snap ring pliers that small. I'm sure someone makes them though.

[Matthew_Armeni]

Originally Posted by sikeston34m

3.5 x 3.14 = 10.99 (Tire Radius)

I think you meant circumference

[sikeston34m]

Originally Posted by Matthew_Armeni

I think you meant circumference

You are correct!

Circumference........that's what I meant

Sorry about the Brainfart there. I have those sometimes.

It's been a long day already and I'm wrestling with this truck right now. lol

[Matthew_Armeni]

That's cool, you keep working, I can't wait to see this thing done!

[sikeston34m]

I've been told to "get-R-done!" So I got her done.

Last night, after installing the diffs, I tried it on 4S Lipo with the 4130. VERY smooth! The cogging is gone just like I hoped it would be. I mean don't get me wrong, this isn't a Rock Crawler.

I couldn't stab the throttle from a dead stop without it acting funny, but if it was rolling 2mph or more, any throttle setting was fine. WOT would top out VERY quickly. With the Phaltline tires, it's VERY quiet running.

The 4130 being 305kv, top end was still low, probably 30mph or so. This 4130 IMO is the ideal choice for a HV setup. I think performance would be amazing on 8S Lipo.

I ran it around for about 10 minutes, then came back inside to do the motor swap.

The motor change went well. I made another motor shaft for the 4120/14 (660kv). CVD spacing is easy to set on this. A test fit without the set screws in the endbell allowed me to perfectly center the dogbone spacing.

This morning I put on 2 Lipo packs that are 5000mah 7.4v 2S1P each. I started the stopwatch at the beginning of the run and had my temp gun in my pocket.

I ran it around in the yard, then up and down a long stretch of asphalt combined with some running in a grassy lot. The grass is about 4 inches tall there.

Top Speed is MUCH better. I don't have a speed gun, but it's doing 45mph+ I'm sure. This platform is very smooth, much more stable than the E maxx. The Phaltlines stick to concrete/Asphalt like glue. I spent alot of time doing high speed runs up and down the road, but jumping off in the grassy lot was fun too.

Acceleration is very good on 4S Lipo. I'm not seeing it flip over backwards from accleration like the E maxx will, but we are alot lower to the ground and a couple pounds heavier too. Brakes are good set to normal.

After several top speed runs, according to my laser temp gun, the ESC was 85 degrees. After checking several times, even after running in the grass, the hottest I seen the motor was 95 degrees. Ambient is 40 degrees outside this morning.

4S 5000mah lasted 32 minutes to the 3.0v per cell cutout.

Temps are very well in hand, I think we can crank it up. I see the 4120 handling 6S Lipo quite well. That's when we will see the torque/speed increase and it will become hard to control. I'm sure it will wheelie at speeds then.

I'm going to try a few other battery combinations. Then I will get some video with sound. It will show how quiet this thing runs. I like it, this is going to be alot of fun.

[johnrobholmes]

Sweeeeeet! Time to go buy some aluminum L for my 1/10th solid axle truck :D I have been using outrunners in cars for so long, seems that I should have tried this by now.

[DrKnow65]

Right on Sikes!

At some point after you've had the opportunity to play with it for a while :) would you mind giving an accurate list of parts (#'s and source) for this conversion? I almost bought a revo roller 3.3 off ebay for $285, but I had to get my 4wd Academy SB V2 Pro first. ($268 after shipping from amainhobbies with a coupon :)

I am going to sell off all my nitro stuff >done with nitro forever!!!< and start persuing the DDR, so any info is important.

Thanks for sharing the build with us all, guy's like you are what make this hobby a blast.

[suicideneil]

That is so very true. Sometimes we need to see other people try stuff out before we can decide whether its a good/viable idea or not. Sike is a trend setter; saddly the planks on noob central couldnt grasp the concept and would rather play with titans or cheapo 600 motors- their loss!