fndcz Posted November 18, 2015 Posted November 18, 2015 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 Quote
A Gallifreyan Cat Posted November 18, 2015 Posted November 18, 2015 Are these the universal joints that you put in the ball joint piece or somewhere else? Quote
MaxSupercars Posted November 18, 2015 Posted November 18, 2015 (edited) 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 Quote
AndyCW Posted November 18, 2015 Posted November 18, 2015 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 Quote
miguev Posted November 18, 2015 Posted November 18, 2015 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. Quote
nerdsforprez Posted November 18, 2015 Posted November 18, 2015 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 Quote
fndcz Posted November 19, 2015 Author Posted November 19, 2015 On 11/18/2015 at 4:46 PM, A Gallifreyan Cat said: 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' Quote
RohanBeckett Posted November 19, 2015 Posted November 19, 2015 (edited) 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 Quote
fndcz Posted November 19, 2015 Author Posted November 19, 2015 On 11/18/2015 at 5:18 PM, MaxSupercars said: 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 On 11/18/2015 at 5:19 PM, AndyCW said: 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. :) Quote
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