Need help designing keyway in gear

[Max Lobovsky]

19 Nm was a typo, I used 13Nm (post edited). With the reduced length of key engagement, you are down to a safety factor of 1.53. That definitley sounds like its cutting it too close. A relatively simple solution that I know is pretty common is to use a double keyway, a key on opposite sides of the gear. It wouldn't be too hard to broach the gear like this (aligning the second cut may be difficult), but I don't think I have seen any stock shafts that come double keyed.

[sanddrag]

Originally Posted by Max Lobovsky

19 Nm was a typo, I used 13Nm (post edited). With the reduced length of key engagement, you are down to a safety factor of 1.53. That definitley sounds like its cutting it too close. A relatively simple solution that I know is pretty common is to use a double keyway, a key on opposite sides of the gear. It wouldn't be too hard to broach the gear like this (aligning the second cut may be difficult), but I don't think I have seen any stock shafts that come double keyed.

That is a really good idea. I know it is done in many real world commercial parts, but I hadn't even thought of that for this. However, like you said we may have trouble "timing" it to be exactly 180 degrees apart. In my current design, the hub of the gear is turned down so it has a very thin wall, and then 4 slits are cut in it at 90 degrees apart, and a split shaft collar is used to clamp the gear to the shaft to keep it from moving laterally because the gear is not "captured" on the shaft. There is a bearing a little ways away from the tooth side of the gear but there is only air on the hub side of the gear. The shaft ends right where the hub ends and the gear "hangs out." I may just redesign a couple things to leave the entire hub the way it comes, put a spacer between the tooth side of the gear and the bearing (making sure it is thin enough to ride only on the inner race), and then make the shaft longer and cut a groove to put an e-clip on the end so it doesn't fall off. I'm liking this idea better. One 3/32 keyway through the entire bore, and leave the hub the way it comes. Space it and clip it. Alittle less machining too.

Also, everyone you may consider the above picture a teaser. This gear appears in our HexaMax R2 system, and by the torques we discussed, you may be able to infer some other details.

[Max Lobovsky]

If you clamp the gear on like that (incidentally, www.sdp-si.com sells stock gears with that type of hub for clamping), that may very well transfer enough torque. It will definitley be pretty hard to analyze the amount of torque it should transfer (though I'm sure the clamp and they keyway would be plenty), so you may not feel comfortable with it, but its just another thing to consider.