hi all. this is my first post so apologies if its in the wrong category. any advice for making a neo shaft connect to longer hex shaft? all the adapters are really short and we need to drive a longer axle. the best option ive found is to move the motor further away from the mount and use the vex hex coupler. any thoughts?
If you have a lathe and the shaft won’t be under a large load, we’ve bored out a churro to 8mm, put two grub screws on the side and sent that. (You could even do the boring operation with a drill press, even a 5/16" bit and a little bit of wobbling or an “O” letter drill will work.)
If it’s going to be under a larger load, you could do the same and then broach in a keyway (it’s metric, and I think is 2mm) and use that to couple the torque better.
3494 has made short hex shaft adapters by drilling hex shaft or churro to 8mm and then using this keyway broach and the matching bushing and shim. Using a broach like this in a shaft 6 inches long would be tricky. You’d probably need a custom, extra-long bushing and shim, and you would either have to push the broach all the way through the entire shaft (which would require some sort of drift to push the 5-inch-long broach out when it’s completely buried inside the 6-inch-long shaft), or you would have to insert the broach until the last tooth has gone as deep as you need the keyway to go and then pull it back out. These styles of broaches are not designed to broach very long holes.
Blondihacks has a video showing an alternate technique which is more ammenable to making partial-depth keyways. It’d be pretty fiddly to grind the custom tool for such a small keyway and bore, but in principle could work alright.
Honestly, the set screw idea is a pretty good one. You can do it in full hex shaft (it doesn’t have to be churro), and if you don’t care about marring up the Neo’s keyway and can get multiple set screws exactly lined up, you can drive the set screws into the keyway itself.
If your team has somebody with decent machining skills, you could take a hex shaft with no hole, drill a small, partial-depth, off-center hole for a makeshift keyway, and then bore the 8mm hole down the center.
If you don’t care about really messing up the Neo’s shaft, you could cross-drill the hex shaft and the Neo shaft, and press a pin through them both.
Without any regard for the rest of the mechanism this is going into, the easiest way to connect a Neo to a long shaft is with a shaft coupler. You could create a makeshift one by bolting an 8mm hub to a 1/2" hex hub. (You would just have to be careful to either get them very well aligned, or leave the bolts slightly loose to allow for some misalignment.)
You could certainly bore a 8mm hole in a hex shaft and use set screws, cross pins or keyways to hold the torque, but please, please, don’t use churros as shafts, particularly not drilled out to an 8mm ID. Churro is extremely weak compared to 7075 aluminum hex shafts most suppliers sell, they are made from very soft aluminum and have a much weaker cross section.
Oooh; that’s a great idea for this case!
Look at 3D printer parts which will be a ready source of shaft couplers that can even take a bit of mis-alignment.
Hard coupler (Amazon gets it here tomorrow).
Flexible coupler (many other sizes as well, depending on how you want to turn down the hex shaft to fit)
Drill the shaft to 8mm, saw a split, and clamp it onto the motor with a hex shaft collar.
Crazy way (which I, um. Might have done…) is to drill a 2mm hole with the centerline at a 4mm radiusfrom the shaft center, drill and bore to 8mm, and then use a 2mm bar as a key.
Crazy #2 is to bore the shaft to 8mm, use a slitting saw to cut a 2mm slot into a face, and them make a custom extra-tall key to fit… done that one too…
Don’t try to broach a 6" long part; you will jam up the gullets on the broach and get it stuck!
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we unfortunately do not have a lathe nor easy access to one, but thank you anyways 
seems like set screws might be the way to go. ill have to check with our mentors if we care about messing up our neos. the only thing im worried about is trying to tap our hex shaft stock since we only have steel stock and not aluminum stock
Mild steel taps just fine as well.
If you end up entirely stuck but can CAD up the part and send the CAD to me today/tomorrow, I could go into our lab on Wednesday, make the part, and drop it in the mail to you and you’d probably get it Monday (or Friday if I overnighted it). I doubt that this is the best plan for you, but as a third backup worst-case plan, 97’s happy to help. (9101 might be a close enough drive for you to ask them for help)
What is supporting the Neo?
I’d just get a Maxplanetary gearbox with no slices. You would have to put some washers or other spacers between the neo and the gearbox (we discovered a few years ago that the Neo shaft is a bit too long for the gearbox.) Alternatively, get a Spark Vortex with the Spark Flex – it spins a 1/2 inch shaft natively.
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the neo is suspended from a sheet of polycarb with the shaft facing up. ive considered a maxplanetary, but the shaft isnt long enough… turns out its closer to a 10" shaft. a spark vortex would be awesome for our team in the future but we dont have the money right now.
i think ill go with this idea–the vex shaft coupler looks like a quick and dirty solution, which we need in order to get this ready for our next competition. solution found, thanks yall
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If you want a really quick and dirty solution, drill out the hole to 8mm, cut a slit vertically in the hex, then put a hex shaft collar around the whole thing.
Be sure to have some other support on the shaft someplace else – it doesn’t matter how you’re physically making the connection; any sort of radial loading over 10" is going to screw up the connection between your hex and the neo shaft.
You can use your own shaft outputting from the max planetary- just make sure to tap it to 10-32 to retain it inside the gearbox.