pic: FRC558's modified VEXpro Drive in a Day

[JesseK]

Originally Posted by TD78

Anyone have thoughts on using 3/8" steel rod as dead axles? Tap both ends of the axle and it'd be close to using tube axle/bolt. I wouldn't think a 1/4"-20 bolt would work...not enough thickness left in the rod. Something smaller like a #10 or #8...at which point you would have to drill all 4 holes in the DIAD sideplate, rather than using the pre-punched 1/4" hole for the outer wheels (of the 8wd)...but it could work.

We had great success with 1/4" steel rod that was put through a die on either end with locknuts in 2007. 2011-2012 we moved to 3/8" steel rod that was supported similarly. It was quite easy to machine - stick the die into a vice, stick the rod in a cordless 18V drill, use lots of tap magic and BAM 30 seconds later you have an axle. Just make sure the mount hole hits the solid rod and not the threads.

As for maintaining proper wheel alignment & spacing - I'd recommend any solid non-deforming material for standoffs. The dark-grey plastic from Andymark works great (it's why it's in the KOP, or was last time I used a KOP).

I agree that the axle itself should NOT be used to stiffen a frame. The only load you want on a wheel axle is normal to the floor so it rides correctly on the balls inside the bearing.

[TD78]

Originally Posted by JesseK

We had great success with 1/4" steel rod that was put through a die on either end with locknuts in 2007. 2011-2012 we moved to 3/8" steel rod that was supported similarly. It was quite easy to machine - stick the die into a vice, stick the rod in a cordless 18V drill, use lots of tap magic and BAM 30 seconds later you have an axle. Just make sure the mount hole hits the solid rod and not the threads.

I should clarify. I was not looking to form 3/8"-16 threads (or similar) using a die...I was thinking about drilling and tapping the ends of the steel rod (using a drill and tap). The rod would become a stiffening dead axle.

[Ty Tremblay]

Originally Posted by TD78

I should clarify. I was not looking to form 3/8"-16 threads (or similar) using a die...I was thinking about drilling and tapping the ends of the steel rod (using a drill and tap). The rod would become a stiffening dead axle.

You could turn down the ends of the 3/8" rod and thread them for 1/4-20. The major downside of this being that you'd need to remove the outside of the drivetrain if you wanted to change a wheel.

[JesseK]

Originally Posted by TD78

I should clarify. I was not looking to form 3/8"-16 threads (or similar) using a die...I was thinking about drilling and tapping the ends of the steel rod (using a drill and tap). The rod would become a stiffening dead axle (although you don't advocate that practice).

Ah, I see. If you mount through the bolt rather than the axle (i.e. the mount hole is 1/4" rather than 3/8" and the 3/8" axle is the stiffening rod) then I don't know if there would be axial load on the bearings.

I would worry about the 1/4" bolt elongating the mount holes after a rare hit - like one that tips the bot up a bit, then the bot slams back to the floor, or like what happens when coming down off of a ramp/bump. We experienced some of this in 2007. When we went back to this style of dead axle in 2011, we used 3/8" rods and also used 1" angle brackets (1/8" thickness) to mount the wheels below the 1x1 frame. This gave us flexibility to change a mount out if we had problems. The "look" of the drive train where we mounted the wheels was similar to the old IFI KOP frame rails.