3D Printing Drivetrain Spacers?

Hello CD,

My team needs spacers of a weird length for our drivetrain axle and I was wondering if 3D printing them would be a viable option (we can print TPU and PLA). Would they be strong enough / last long? If not, whats another way to make custom length spacers that could be done with commonly available tools?

Thanks,

18sampson

How weird are we talking, and on what kind of shaft? VexPro spacers can get you to within the nearest 1/32’’ on most shafts (their smallest spacer is 1/16’’).

If 1/32’’ accuracy won’t cut it, I’d first suggest considering a less-demanding drive design (having to space things on your wheel shafts to better than 1/32’’ tolerance is not going to be fun and possibly indicates some deeper design problems). If you’re absolutely certain this is the best way to go, then spacer stock and a lathe are probably the best solution.

We don’t have a lathe, so I guess we’ll just have to deal with nearest 1/16". That should be fine for a standard tank drive wheel, right?

Yes, we’ve used the VexPro spacers on our tank drive shafts every year and never had a problem with them. They’re plenty capable of locating drive wheels and pulleys to within the tolerances required of most FRC drives.

(It’s also worth noting that a 1/16’’ spacer actually gets you to within the nearest 1/32’’ - I have corrected my first post to reflect this).

Edit: Also, consider purchasing a lathe. A small hobby lathe is a pretty cheap tool that you’ll get a lot of mileage out of.

As oblarg alluded to having 1/16" spacers will get you within 1/32".
The farthest off you will be with 1/16" spacers is half of a spacer width-1/32.

To answer your question, yes 1/32" is plenty for any common belt/chain setup

–Got sniped

We’ve been using them for the past two years with only minor issues (a pulley came loose on the X-axis of our main printer). They’re not being loaded perpendicular to the layers, so you should be fine with PLA. We used PETG, but only because that was available at the time.

Our team (With my printer at home) prints all our spacers for everything. We just use regular old PLA and make them same specs as the Acetyl spacer, 0.5 hex - 0.75" OD, and they work fine, we use them on our climber shaft to space the drum, DT, and anything else, its super fast, cheap, and accurate, and usually there isnt much side to side load on shafts so it works great!

This may depend on your application, but another thing to consider is the following: you don’t always need everything to line up perfectly. While 1/32 of an inch may matter a lot in CAD because trying to mate two surfaces that aren’t touching will cause a conflict, in real life this isn’t the case. If I have a wheel on a shaft and it has 1-32" of play, it won’t really make a difference in the big scheme of things. While this definitely isn’t a good practice, sometimes letting small things slip through is okay so that you can focus on larger issues.

In CAD, it shouldn’t matter either. Last time I was working with CAD I used an offset mate an awful lot… (Mate the surface, but set a distance of X>0 to move the parts apart.)

I would say having a tiny bit of play in your drive shafts is a *very *good practice. It prevents things from binding. It is probably inadvisable to have a drive shaft that is sufficiently constrained that you can’t afford 1/32’’ of play unless you really know what you’re doing, for precisely this reason.

We made custom 3D Printed spacers this year that mate with the VersaHub pattern on our VexPro traction wheels (to prevent them from falling off if you have to remove a wheel or replace a shaft) and they worked quite well and have negligible wear on them after 2 events.

We did have to file a few of them down a bit, but I think this was more due to inconsistencies in other parts of the frame or the way the wheels were assembled which was causing the fit to be too snug.

tl;dr - Though I was initially skeptical, I would definitely recommend it if you need custom spacers.

We print all our spacers. Worked nicely on our swerve this year.

We used PLA, 100% infill.

Our team has previously used 3D printed spacers well, but if you’re in a pinch (or don’t want to deal with 3D printing), we’ve found that PVC pipe works well too.

3D printing spacers works great. 1678 uses them a lot in drivetrains and other gearboxes with no issues. Typically we use PLA with about 30% infill with no problems. We also oversize the hex so they slide on the shafts easily.

Back in 2016, I made spacers out of PLA that were about .236" in width for hex shafts on a track-style drive system.

We only had problems with losing the tiny things, but then again, we could print new ones in about 8 minutes.

We 3d print most of our spacers. They work great. Remember, it’s a spacer so you can scale it up a bit to get a loose fit around a shaft… unless there is some reason you need it to be tight. The spacing is the critical dimension, not the size around the shaft.

Other old trick is PVC pipe and a decent pipe cutter. Cheap but not near as accurate… though it works in a pinch.

Most of our spacers are PVC pipe, cut on our lathe. Without a lathe, you can cut them on a bandsaw, but your accuracy isn’t going to be as good - so cut it a little long, then bring it to the length you need with a sander. Pretty easy and straightforward!

We have 3D printed some in the past, but honestly… it takes too long. I can make a spacer out of PVC pipe on the lathe in under a minute, while the same spacer 3D printed could take an hour. In most applications for FRC, there’s no functional differences - either solution will get you within the tolerance needed for what you’re doing.

Our team has printed hubs for our wheels two years in a row now. 3D printed spacers are fine.

We’ve used the vex spacers, 3D printed spacers, and PVC on a lathe. They all work fine.

The PVC in a lathe is really quick to cut a bunch of identical spacers. You can use the set distance caliber extension to quickly position the cutoff blade to the PVC end; repeatably making a whole bunch of exact sized spacers.

We have been printing spacers for the past several years. We sometimes opt for Nylon for durability but PLA or ABS work find.
I published an OpenSCAD model that lets you customize the spacer, choose the axle type and size. You can find that model on Thingiverse.