Not a very simple part to make. 5/8 hex, to 5/8 round, to 1/2 hex, to 1/2 round, to 7/16 hex. Thank you to 968 for the design and photo inspiration.
Are those Pneumatic cylinders or shafts or what?
They look like a shaft of some sorts? And that is some intricate machining on the parts.
They are shafts for Transmissions. The slot towards the rear is to accommodated the dog gear to allow shifting.
I take it these are your transmission axles, and the step hexing allows for round bearings everywhere while using COTS sprockets.
Impressive work - how was it made?
So there could be two gears or more spun by the motor, and there could also be some free-spinning gears in the middle, as well.
We actually make our sprockets as well, from 7075 bar stock, but they’re basically a copy of the AndyMark or VexPro ones. We do use all round bearings in the drive system. That’s the benefit of going down to 7/16" hex at the wheels and front and back sprockets. Also, we have no keys anywhere in the robot other than the 2mm key on the CIM motors, but we do use hex bearings (unfortunately) on the choo-ch…uhh, other gearbox for a few reasons we couldn’t easily avoid.
Machining this was a bit of a pain, primarily due to the length of the shaft and number of setups required. The machine shop that did these for us tells me that it was two CNC lathe and two CNC mill setups, with a 4th axis in a vertical machining center. The chatter marks on the 7/16" hex are because they didn’t have a tailstock for their 4th axis, so it was sticking way out there.
The right way to do this would be with a live tooled Y axis lathe, or even better, a swiss screw machine. But, we don’t (yet) have a sponsor with these types of machines.
They are shifting drive shafts, very similar to what 254 and 968 use. The 5/8 round are for the dog gears. The 5/8 Hex is for the shifting dog. Then the 1/2 Hex is for the Drive sprockets. The 1/2 Round then goes through the frame using standard 1/2 inch round bearings instead of Hex. Then the wheel attaches to the 7/16 Hex.
Yep, that’s what we were going for. Our photography student went from almost zero experience with camera settings, to the photo I posted, in just a couple weeks time. The 968 one still is my favorite though, but we’re getting better.
Its funny how you thank 968.
Being that you were part of that team, arent you thanking yourself?
My goodness. I do not envy the machinist who had to make those. Though I envy their capability to do so.
Manual mill and lathe can make these parts without an insane amount of time.
You would need some sort of clever jig for machining the hexes on a manual mill though.
You could use a 5c indexer or a 5c collet block.
Put round shaft on mill, flatten one side, turn 120 degrees, repeat.
Yeah, making a 120 degree turn without aforementioned “clever jig” isn’t exactly easy to do precisely? You need the 5C collet to do it right.
The part is definitely possible with a manual mill and lathe. It would just take some time, a decent machine, and someone who knows what they’re doing.