What is the max tolerance of the 3L Joint part?

[fndcz]

I just got this part damaged when driving my MOC. Anyone knows what is the max tolerance for this Joint part? I use 2 Large motors for driving and the gear ratio is 12:20=>1:1=>12:20 (where the part connected to)=>20:28=>12:20 = 1:6.485

[A Gallifreyan Cat]

Are these the universal joints that you put in the ball joint piece or somewhere else?

[MaxSupercars]

The max tolerance depends also from angle... when they are straight the probability of breakage is lower... but when the angle is near 45° the probability is high... based on your pictures it was the second case...

Max...

Edited November 18, 2015 by MaxSupercars

[AndyCW]

Ahhh.... the joy of breaking u-joints with rc lego vehicles.

Their strength with depend greatly on how they are implemented.

• Place them inside of the 'ball joint' and they are pretty strong.
  
• Keep the angle of them to a minimum and they are stronger.
  
• Try to place them upstream of the most forces in the drive train.
  
• Mount them securely.
  
• Lastly; avoid shock loads.
  

Congrats on finding a weakness in your design. It means that you have more fun ahead of you correcting it.

v/r

Andy

[miguev]

Looking at your photos in the other thread, it looks like have a 12:20 reduction twice before and once after the U-joints, and you're already using the ball joints and portal hubs.

So I'd try using a 8:24 reduction in the portal hubs, which is as much as you can get "after" the U-joints, so that they have to cope with less torque.

To keep a similar overall reduction in your drivetrain, you can use 14:20 once instead of your current double 12:20, or maybe just leave a single 12:20.

[nerdsforprez]

I have a project I am currently working on, likely be posting soon, where I busted a u joint with nearly no angle to it. XL motors are pretty strong. If they can twist axles only 5 studs in length they can bust u joints, angle or no angle no problem with the right gearing

[fndcz]

Are these the universal joints that you put in the ball joint piece or somewhere else?

Yes I placed them inside of the 'ball joint'

[RohanBeckett]

although you can't use this technique within the ball joint, check out this method of reinforcing the U-joint's end (where you had a split)

Edited November 19, 2015 by RohanBeckett

[fndcz]

The max tolerance depends also from angle... when they are straight the probability of breakage is lower... but when the angle is near 45° the probability is high... based on your pictures it was the second case...

Max...

The angle... I think you are right. Thx

Ahhh.... the joy of breaking u-joints with rc lego vehicles.

Their strength with depend greatly on how they are implemented.

• Place them inside of the 'ball joint' and they are pretty strong.
  
• Keep the angle of them to a minimum and they are stronger.
  
• Try to place them upstream of the most forces in the drive train.
  
• Mount them securely.
  
• Lastly; avoid shock loads.
  

Congrats on finding a weakness in your design. It means that you have more fun ahead of you correcting it.

v/r

Andy

I put them in the Ball Joint, I believe the reason is the angle. Thanks for you detailed explanation, looks like I have more work to do. :)