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Why Race Cars & RC Cars Use Different Axles

curv lab

532,890 views

Race cars, road cars, and RC cars all send power to the wheels, but each uses a completely different type of axle. I went to Laguna Seca, and started noticing axle designs on race cars, got obsessed, and built the test rigs to figure out what to use on the printable WR1 Chassis.

In this episode I break down dog bones, Cardan joints, and Rzeppa CV joints from first principles, prove why a Cardan joint makes the output speed pulsate, then use it all to design a fully 3D printable 1/8 scale axle for the Curv Lab WR1.

Get the print files: https://www.curvlab.com/
Download the WR1 chassis: https://www.curvlab.com/products/wr1-...

CHAPTERS
0:00 The Printable RC Car Dream
0:52 Inspiration From Monterey Car Week
1:49 Why Do Cars Even Have Axles?
2:20 The Basic Anatomy of a Driveline
3:25 The U-Joint Explained
4:26 The Dog Bone Joint on RC Cars
5:42 Laguna Seca: Race Car Axles and Splines
7:11 Why Race Cars Use Roller Bearings
7:53 Designing a Cardan Joint in SolidWorks
10:20 Testing the Cardan Axle (and Why It Pulsates)
12:50 The Solution: Rzeppa CV Joints
15:03 Why the Rzeppa Design Is So Genius
15:39 Testing the Rzeppa CV Axle
16:28 The Downside: Grease and Boots
17:06 Fixing Cardan Speed With Phasing
18:16 100,000 Subscribers!
18:33 Why I Chose Cardan for the WR1
19:12 CAD: Designing the 1/8 Scale Printable Axle
22:12 Slicing, Printing, and Assembly
25:39 Final Road Test

Everything was printed on a Bambu Lab H2S
https://tidd.ly/4gIds9I

Subscribe if you want more mechanisms explained by building them.

20 Comments

@CURV-LAB Creator 3 days ago Pinned

What should I build next? I read every comment.

1. WR1 upgrades (better diff, new suspension, more power)
2. A 4x4 printable chassis
3. Something totally different (buggy, drift car, crawler, rally car)
4. Another deep dive like this one on a different mechanism?

Reply with your vote or tell me what you want to see.

@m.b.82 3 days ago

Having a uni at both ends of the shaft or axle cancels out the pulsation, as long as they are both always at the same angle as each other and in phase, not 90° out.

@tomyum-p5p 2 days ago

This feels more like hobby engineering rather than hobby rc car-ing. Love it

@briguy3418 3 days ago

Love the format. I really like how you make a lot of the engineering concepts more approachable for everyday people

@tiger3dprinting 3 days ago

I yearn for your ability to sketch your design ideas

@JJRossi 3 days ago

I sure hope ur subscription count quickly catches up with the quality of your videos! Super underrated channel! Been watchin for some time now, keep up the great work!

@BPBomber 3 days ago

You may not be Alfred H but I now understand CV axles. Thank you for the excellent explainer

@jakebrakebill 3 days ago

editing the video had to be as hard as the build, nice job

@rcbigtirepilot 3 days ago (edited)

26:06 Looks like you could do a video like this on sway bars next 👀

@Technical_Failure 3 days ago

Dude you're truly a genius with those explanations holy

@JustinBMcBride 2 days ago

Found you today from your Reddit post of your sketches on the industrial design subreddit. As an architectural designer who has decided to return to school for a Mechanical Engineering degree, I have to say, I loved every second of this. Thank you.

@sspence65 3 days ago

You can put a double cardan on one end to cut the angle in half. So instead of a 20-degree angle through one joint, a double has 10 degrees through both. Neat trick with lifted vehicles ....

@TJPDmember 3 days ago

To remove the slop from the bearing you don't necessarily need a bigger bearing, what you want is two bearing like a car does with a nut to tighten those bearings. Most cars work that way.

Also, if you run the upper control arm level to the ground at ride height and the lower control arm slightly at a downward angle towards the wheel hub, you'll gain negative camber on the outside wheel when suspension is loaded, this will help tremendously with handling.

@nikiin22 2 days ago

this is incredible content, thank you so much

@nutsandy7183 3 days ago

great stuff. I knew a lot of this one but you are genius on how you break it down for people. Using the card to hear the speedup / slowdown was something i would never have thought of!