Big Rock Here we go! 😂

[kaladeth]

It’s not going to break any speed records for sure. But it works! Ran down a 6S pack. Will check how the gears are faring, and then do some jumps.

Not quite the sleeper I was shooting for - maybe when I stick in an 8S .

Sorry guys nothing exploded. Yet.

 

[Neelis]

Gear up! I want to see 100+ mph !

 

[NitroK]

That motor can crank a 30T pinion without breaking a sweat....

 

[kaladeth]

@Neelis you and me both!

@NitroK would depend on spur size but yeah it has some room to go. Which brings me to…

Road Block #3

Biggest pinion that fits the stock motor case and mount is 22t (mod 0.8). Also since the motor is not 100% flat the alignment is not ideal and will lead to eventual failure somewhere. Lastly there is so much vibration that the motor fins still groove the drive shaft. Not sustainable.

Plan is to design an open, custom motor mount, that will allow bigger pinions, at the correct angle for smooth alignment, and more distance between the motor and the drive shaft.

Any CAD experts out there willing to help design it?

 

[Neelis]

@Neelis you and me both!

@NitroK would depend on spur size but yeah it has some room to go. Which brings me to…

Road Block #3

Biggest pinion that fits the stock motor case and mount is 22t (mod 0.8). Also since the motor is not 100% flat the alignment is not ideal and will lead to eventual failure somewhere. Lastly there is so much vibration that the motor fins still groove the drive shaft. Not sustainable.

Plan is to design an open, custom motor mount, that will allow bigger pinions, at the correct angle for smooth alignment, and more distance between the motor and the drive shaft.

Any CAD experts out there willing to help design it?

I have Solidworks and Autocads skills and also the software available. How you want to approach this?

 

[kaladeth]

A few updates:

• The gears are totally fine after one pack of street bashing / speed running, and one pack of jumping.
• The slipper area gets really hot. It got so hot, it started melting the end of the center drive shaft. New shaft ordered.
• The maximum pinion that will fit with this stock mount is 25T. This is a snapshot with a 3d printed gear:

To hit the 100 mph target, I see two paths:

1. Redesign the mount case to allow a 33T pinion. 6S should get us there. (Thank you to Neelis for the assist!)
2. Upgrade the battery to 8S (and use a 25T pinion). Will be ordering the battery soon, just need to complete a size check.

Regardless of the approach, I think a fan is also required, so will have to see how it can fit. I don't think there is any more room!

 

[kaladeth]

Custom mount case mock up is looking good. Rotating the plate by 7.5 degrees has given 3.8 mm lift to the motor / motor drive shaft.

Next up:

• Design a matching back cover
• Install 25T pinion
• Sort out fitting the motor, the drive shaft, the center support, and the fans

 

[kaladeth]

Done! It sounds so good on the bench. Can’t wait to take it to the streets!

Any bets on how fast it’s going to go?

 

[King blitz]

Done! It sounds so good on the bench. Can’t wait to take it to the streets!

Any bets on how fast it’s going to go?

View attachment 359549

I say 83 mph before your diffs blow up unless you put in 4s diffs .I wish you the best of luck bud ..let's go

 

[J.Rambo]

Go get 'em bro!!

 

[King blitz]

We wanna see vid of this plz ..we take no excuses or it never happened..also we need a gps to confirm your speed

 

[kaladeth]

Guess what. It actually went slower. And this happened . Need to tighten up the slipper or spool it entirely. More to come!

 

[King blitz]

Guess what. It actually went slower. And this happened . Need to tighten up the slipper or spool it entirely. More to come!

View attachment 359647

Bro.. eliminate the slipper.no need for one for speed runs .make a spool for when u do passes and put back the slipper when u bash

 

[Garcbomber]

I'm sure the slipper loved battling the front toe!

 

[kaladeth]

Bro.. eliminate the slipper.no need for one for speed runs .make a spool for when u do passes and put back the slipper when u bash

Yup!

I'm sure the slipper loved battling the front toe!
View attachment 359649

I was wondering about that. For some reason under load the toe goes straight - will take a video and adjust as necessary.

I should probably switch to road tires too. And a bunch of other things. Too excited.

 

[kaladeth]

Switched out the slipper for a spool, and got this on the first pass or so:

Can you spot what kept me from going for more?

 

[kaladeth]

So! After a quick swap of the busted rear slider driveshaft (stock replacement), I managed to get in some decent runs before the sun went down.

68 mph!!!

I really can’t get any faster than that on this short stretch of road. Not safely anyway.

The truck is feeling really good. Very planted with the road tires. Hums like a kitten too! I am loving it.

The only final mod I would make is to install the cooling fans. It survived ten minutes of back to back runs and nothing melted . But the center shaft got up to around 140… something grinding maybe? Motor was at 110. Rest of drivetrain was fine.

Will update my Big Rock 3S build thread with all the parts used.

Oh and yeah, I did smash the front bumper when it cartwheeled on one of the runs. Other than that she is ready to keep going! Will take it to the skate park for some jumps one of these days.

With that I bring this particular experiment to a close.

That was FUN !

Thanks everyone! Hope you all enjoyed as much as I did. On to the next crazy project…