The Handful of Buggy 4x 5292

[AndyCW]

Hello All,

It has been ages since I shared something on here, even though I visit daily to see everyone else's builds.  However, 'recent events' have given me more time to build.

I haven't been idle these last couple of years, but nothing I made rose to the level of sharing.

The following buggy has four unrestricted 5292 motors, at 12.6 volts, going to the rear wheels and only weighs 1400 g.  This makes it hard to handle for the inexperienced driver.

The rubber bands on the rear control arms keep the ball sockets from coming apart. 

The lower arms are different from the upper ones due to the change in position of the joints on the swing arm through the suspension cycle.  This also creates a rather nice camber curve.

I also discovered a weakness in the stiff springs.  The upper mount will shear off of the side of the shock body if it is used.  Many of my shocks have stress fractures there.

I've got to clean the thing up now, it is covered in mud.  I wonder who did that.

Question, concerns, comments, or relevant war stories?

 

v/r

Andy

 

Edited March 26, 2020 by AndyCW

[BusterHaus]

This is a beast. You can try extending the wheelbase to make it a bit easier to control. By the way I also have a long yellow shock absorber that has a crack in the upper mount. I get the feeling it's a weak point in this part. 

[AndyCW]

During one of the test runs, before we got out the camera, the front right hand shock mount sheared right off the spring body.  This is why the springs are mounted by the vertical central cross axle hole.  Looking closely, in some of the pictures, the damage to that spring is visible.  I didn't have another spring easily available to replace. 

I think my next creation is going to be another rock bouncer with the same power, but less weight.

[TimberBrick]

How do you control the buggy motors?  I find that with SBRICK they limit out (cause the H-bridge driver to derate) especially above 8 volts.

[AndyCW]

I'm using a non-lego solution.

https://www.dimensionengineering.com/products/sabertooth2x12rc

It is inside of the orange 3d printed box in the center of the chassis.  It is in turn connected to a 2 channel 2.4ghz radio controller.

 

[TechnicRCRacer]

3 hours ago, AndyCW said:

The upper mount will shear off of the side of the shock body if it is used

I found that out the hard way, I dropped my copy of 9398.

 

This car is super fast, I love it!

[Touc4nx]

Wow, so fast, it's hard to believe that you used the new planetary gear and still achieved such a consequent speed. 

[kbalage]

Very impressive, especially if you can drive the buggy motors with 12V without the protection kicking in. Can you please give us some details about the "unrestricted" motors, did you modify them in any way?

[AndyCW]

'Unrestricted' may have been hyperbole.  The motors have not been altered.  The motor controller can sustain 12 amps indefinitely and can burst to 24 amps.  I have not had any problems with the controller thermally limiting the motors or the motors thermally limiting themselves.  

Some potential explanations for why the motors are not thermally limiting themselves:

• motors exposed to airflow, not buried inside of the MOC
• ambient temperatures low
• 1.8 gear ratio off of slow output
• low weight
• lack of traction