My team is planning to purchase a set of SDS MK4 swerve modules (the NEO version). I was reading through the product page, and noticed something about how we’d have to either cut the motor shafts shorter or purchase an additional part (their motor spacers) because the motor shafts are too long. Is this only for the Falcon500 version, or would we have to do this with the NEO version as well? I’m under the impression that the NEO motor shaft is shorter than the Falcon500 shaft but maybe I’m wrong about that? Please let me know if we’d have to cut the NEO shafts shorter, or if that’s only a thing for the falcon version.
For reference, this is the part of their website which says that: " The MK4 module design requires the length of both motor shafts to be reduced by about 0.25in. Alternatively, motor spacers can be used to eliminate the need to cut the motor shafts" Are there any teams here who have used the NEO version of the MK4s? Did you need to buy the additional motor spacers?
We started off cutting shafts but that took more time than expected and, while it worked, machining results for us were not outstanding and the whole process was more difficult than planned. While it was a good learning experience in various machining techniques, we wound up ordering spacers and found them well worth it.
Spacers vs. cutting shafts applies to both NEOs and Falcons. We started with NEOs for a test chassis and then went with Falcons on our comp bot so have experience with both.
Cutting the Falcon shafts meant doing extra work to get the spline to fit the pinion gears and at least one of the shafts we tried was not threaded down as far as we thought so we had to find a shorter machine screw to avoid bottoming out. Perhaps we cut that one down a bit too far. So it goes with young machinists trying to learn things for the first time.
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Darn, okay, thanks. It seems odd that the spacers wouldn’t just come with the modules then, maybe they were trying to lower costs? We’ll look into ordering them so that we don’t have to cut the motor shafts shorter
how did you cut them? we just took them to the bandsaw and it took less than a minute
On my old team, when we needed a CIM class motor’s shaft cut down, we’d toss the motor in the chuck of a lathe, spin up the motor under it’s own power and turn down the shaft with the lathe. Worked great for us 
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Although if I recall, a NEO’s casing is slightly tapered which would make things slightly more challenging with this method.
We tried a lathe and a hacksaw but that went slowly and we feared spinning long and fast enough to damage the motor. Don’t know whether that can happen but heard about a team burning up Falcons pushing their robot fast down a long hallway. We also tried running the motor with a SparkMax and holding the hacksaw to it but it took a long time and it was challenging to hold the saw in the right position.
Also tried hacksaw with shaft in a vice which worked - took some time and elbow grease but wasn’t the straightest cut.
Also used a dremel (with mini grinding wheel) which was the fastest cut we made but it generated a lot of sparks (face shields, gloves, earplugs, etc. worn) and took a steady hand (tended to catch or slip at times which made it move fast away from the shaft and we felt not the safest method).
We do not have a bandsaw capable of cutting hardened shaft steel… (small team only a few years old so our tooling is quite limited - metal chop saw, drill press, dremel, hand drills is pretty much what we have).
The NEOs we did cut worked great, but we had some trouble getting the Falcon shafts right with the first couple (including the shorter inner thread depth after the cut) so we shifted to using the spacers so that we would be simply assembling rather than machining. As we grow, hopefully our machining tools and skills will to the point where cutting shafts right will be less of a battle. We initially thought it would be easy and save us the cost and 0.25" of the spacers but in the end the time savings was worth it for the team to just go with the spacers.
Do you have a bandsaw that you might recommend? Sounds like it may be a good idea for us.
well unfortunately the bandsaw we have is a dinosaur from the 70s so you cant really buy them anymore but if you’re looking to buy a bandsaw i would make a new thread cause I cant really recommend something I haven’t used. as for when we cut we just had a pair of pluers holding the shaft still and just sent it through the saw.
@afk7890 A related question, do you know why the NEO shafts have to be cut? Looking at the CAD, there seems to be plenty of space (0.53 inches when cut, so 0.28 inches when not cut) between the tip of the motor shaft and the next surface. So why do they need to be cut shorter?
(The picture above is when the shafts are cut, but there is 0.53 inches of space so it seems like it should be fine without cutting the shafts?)
We looked as well after finding shaft cutting more of an exercise than we anticipated. It looks like the CAD you are showing has the 9mm steering belt while the more recent MK4 modules have a 15mm belt. Ours are the more recent, so that costs 6mm or maybe a bit more off of the 0.53" so you are getting down to needing to get the extra 0.25" out for clearance.
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Ah, okay, that makes sense. Thanks for the quick response!
FWIW, when cutting steel, you probably want to lean toward some type of cold saw. You can get good results different ways, but work hardening can be a thing.
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