E-Revo to E-Slayer conversion Project

[lincpimp]

Originally Posted by TruckBasher

Cant wait to put all this things together.....

Linc...+1 on the ofna 17mm I have them on my maxx (after a not so good experience with 23mm adapters)...They are easier to use and enough to handle large wheels.... I bet there are perfect on buggy size wheels/tires....

Yet, they fit fine, and with std buggy wheels it appears to have almost the same track width as a stock slayer. Funny thing is my buggy badlands seem to be made of a much harder compound than the ones on the revo... They will actually make screeching tire noises on concrete, kinda funny!

[TruckBasher]

Sounds a killer.....cant wait for you to upload your video on that thread

I have the stock tires so maybe Ill just run them first for testing....but I want to run moab tires instead not sure how they fair cause I mostly see guys using badlands....

[sikeston34m]

OMG guys! How could I have missed this? Please, PM me if I miss a build like this! LOL

This is looking GREAT!

You're going to be pleased with this setup you are doing.

Metalman, feel like doing an E Revo Chassis Conversion for me too? LOL

[TruckBasher]

Hehe Sikes, IIRC you were the first one I asked about this conversion, I PMed you about it ..this was inspired from your Direct Drive to Diff

well you havent missed it....we are still in the middle of the build...most of the parts are in just having issue with the bottom support....

[sikeston34m]

Hey Truck,

Thanks. Mind if I join in on this conversation? I'll tell you about what I learned concerning various componants with this setup.

It's looking GREAT so far.

I see you chose the 4120/18. Great motor! I was running the 4120/14 using the 4.3:1 truggy gears along with the 5.75 Revo tires. I seen this setup running 60 - 65mph on 6S Lipo 10C! I know the batteries were being pushed over their limits. They got very warm.

This is where I ran into a problem. When you blow the inboard rear diff bearing on the pinion, go with the 3.3:1 buggy gears. They are MUCH tougher. I know, I know. It's a taller gear ratio. But the pinion does NOT have spiral cut teeth. The spiral cut pinion side loads the pinion bearing. It's not a thrust bearing, so it just doesn't hold up.

I blew mine on the 2nd run. I replaced the bearings with Ceramic Nitride versions. Same result. It punches the center bearing race right out. Then you have balls everywhere. LOL

It was at this point, I decided to do a custom Wye wind on a 4130 motor. 7 strands of 22 awg for 4 turns IIRC.

I felt like I had to do something because with the 5.75" Revo tires, the gearing was too high for the 4120/14.

Using 5.75" tires.

4.3:1 gears equals 4.2" of rollout per motor revolution.
3.3:1 gears equals 5.5" of rollout per motor revolution.

HUGE gearing change! So I decided I needed the added torque of the custom wind along with the longer stator.

The end result was incredible. BUT.........there's always a but. LOL

The starting amperage of the new combination was so high, during the last half of the charge, it was lazy out of the hole and the batteries were getting really warm. This time I had 5000mah 20C and they should be good for 100 amps continous with 125 amp Bursts. I'm not sure if this was to blame on my custom wind or not.

With the 4.3:1 gears it worked perfect with the 4120/14.

Traxxas has came out with the Slash! I've been looking at those tires. They are EXACTLY what this setup needs. Now let's plug some numbers.

Using 4.3" tires.

3.3:1 gears equals 4.1" of rollout per motor revolution!

Even better than the 4.3:1 gears using the 5.75" tires.

I'm Glad I didn't sell my converted Revo stuff after getting disappointed and sidetracked. I will revisit this project. All I need are some good Slash Tires/Wheels.

[MetalMan]

sike, you are the leader of the Revo "direct drive to diff" conversions . So of course your input is appreciated.

That bottom brace will be looked into further today. I have about 4 hours between classes .

[TruckBasher]

Well Sikes, if there is one thing I remember what you told me its about the diff ratio...thats why I have both HB diffs (4.3:1) and ofna buggy diff(3.3:1) but not sure yet about the rest and the motor..good thin is that I have a LHS that carry them here so it easy to get them....like what Travis said...you are the master in this setup so I try to keep as much as I can learn...your input is always appreciated..

Travis, I hope this this doesn't mess with your schedule, school is always the priority

[sikeston34m]

What Battery Combination are you planning on running with this?

Any updates as of late?

[TruckBasher]

I will try 4S2P A123 for starters...maybe up a bit to 4S Lipo 6000 PQ (havent bought them yet)......

Travis will be updating this tonight, he might still be at work

[MetalMan]

I did have to work the closing shift, and I know it's not night anymore, but here are the pics as promised:










And a sample of one of the standoffs I made, which is a 4x20mm set screw epoxied into a custom tapped aluminum tube:


This is the second set of parts, the first set of parts is equally as finished . Now all that's left is the bottom/lower skidplate (will be made from 1/16" thick delrin and will span the entire width and a good portion of the length of the chassis).

[TruckBasher]

OMG, that support at the rear end will make this more sturdy...

WOW Travis...thats all I can say.....

[MetalMan]

It's definitely not the prettiest, as the aluminum still needs to have its surface sanded, and the polycarbonate pieces (rear motor support and rear chassis/bulkhead brace) still have the protective white film on them. I'll leave it up to TruckBasher to remove that protective film, and then take pictures to show off that polycarbonate.

The rear bulkhead/chassis brace will probably need to be separated into two pieces. The center-rear driveshaft goes through where the brace sits, and I haven't been able to come up with a solution to connecting the two sides of the brace together that won't interfere with the driveshaft.

And one last comment - at the front of the main motor mount the hole the driveshaft yoke sticks out of is a whopping 3/4" (19mm) in diameter! That is one gnarly drill bit I had to buy; I never anticipated dropping $23 on an individual one! Not to mention the torque that thing put out made drilling way more difficult than anything I had drilled before... Definitely a good learning experience.

[sikeston34m]

Excellant Work! I may wind up doing this with a spare E Revo Chassis that I have here.

You're not going to be satisfied with the top speed of the 4s2p A123 cells using the 4.3:1 gearing.

I plugged your values into Brian's Estimator. Here's how it looks.

Differential Ratio: 4.3
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 13.2
Motor KV: 515
Tire Diameter (inches): 4.3
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 4.3 : 1
Tire Circumference (inches): 13.51 inches (343.12 mm)
Total Motor Speed: 6798 RPM
Vehicle Speed: 20.22 mph (32.49 km/h)
Estimated Adjusted Speed: 20 mph (32 km/h) - 2% loss
Effective KV Value: 515

This setup will not cog at all. Expect everything to run VERY cool. It will top out instantly and you're gonna be surprised how quiet it runs.

Here's yet another setup. Using the 3.3:1 gearing and 6S Lipo. Your motor will handle 6S. If you notice, now things are getting quite speedy. This will be ALOT harder on the drive train and alot harder to control. I'm not sure if those stock center drives will hold up to this, but here goes.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 22.2
Motor KV: 515
Tire Diameter (inches): 4.3
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 13.51 inches (343.12 mm)
Total Motor Speed: 11433 RPM
Vehicle Speed: 44.22 mph (71.03 km/h)
Estimated Adjusted Speed: 42 mph (67 km/h) - 6% loss
Effective KV Value: 515

Here's the all out setup that I will be doing. Let's swap motors now. This is running the 4120/14. How about the V3 Mamba Monster to power this? We can program it to be easier on the drive train. But here it is, the all out setup IMO.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 22.2
Motor KV: 660
Tire Diameter (inches): 4.3
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 1 : 1
Total Ratio: 3.30769 : 1
Tire Circumference (inches): 13.51 inches (343.12 mm)
Total Motor Speed: 14652 RPM
Vehicle Speed: 56.67 mph (91.03 km/h)
Estimated Adjusted Speed: 52 mph (84 km/h) - 8% loss
Effective KV Value: 660

Top Speed seems faster. Using the 4.3:1 gearing on 6S, I was almost keeping up with interstate traffic (sideroad) with 5.75 tall tires. The Phaltline tires.

On 6S, we should keep on eye on temps until we get a feel for what it's gonna do.


I'm curious as to what your vehicle weight will be? I think my Revo Conversion is a little heavy.

[TruckBasher]

Nice numbers Sikes, I actually computed this with 4S lipo in mind but I want to try first with my 5S2P A123. However, i dont think my previous mod on the chassis to fit the 5S would be ideal (might weakened the chassis too much) so i chopped of 1 of the battery on top to fit 4S...i might put that cell on top if i can find a way to mount it.....

For the ESC, I initially wanted an HV110 for the soft start but breaking will be a problem and its hard to get pistix now. I will transfer my MMMV2 from the EMAXX to this conversion..EMAXX will get MGM 16025....

I think your conversion will be fast no doubt about it...but my conversion was not intended for speed but just bashing... for me 30-40mph will be the top speed I can control...im not too good

Travis, I think it should be ok to cut them off...no choice but if you have a spare alu as thick as the motor brace, inch high and wide as the screw on this mount I might be able to make an arc to join the 2 piece...maybe you can give me some

[TruckBasher]

I just remembered I built the hybrid diffs and I've used Ofna buggy diffs so I am using 1:3.31 after all