3D Printed MatTracks for RC Car in 1/10 Scale

Earlier this fall, I was in the hobby shop to pick up some parts for my Sawback Gmade GM52000 and saw a set of what looked like tiny MatTracks to install on it. Not wanting to spend the $250 the hobby shop wanted for the used set, i thought to myself, "hey! I can make these!" So I decided to 3d print my own custom RC car tracks.

Since then, I've been through several dozen revisions, getting the fit and look just right, and trying to find all the necessary hardware, along with setting up my printer to handle the rubber material needed to print the tracks and other rubber parts from.

My original design used my own shape of frame, which improved upon other available designs by offering a longer ground contact patch and slightly higher axle lift, while still maintaining clearances to prevent rubbing. My latest design is actually a direct copy of the MatTracks used on Ken Block's F150 Raptor, "RaptorTrax". I searched the internet for a clear picture, and using measurements from the photo and specs from the Mattracks website, came up with this design, which looks surprisingly realistic.

Finally, the color was chosen to match the color of raptortrax as closely as possible, but a bright yellow could be used to match the more common MatTracks color, or you could use any color that you think is cool.

This is my first Instructable, and I'm writing it because I think everyone should have access to their own 3d printed custom rc car tracks! If I win I'll use the printer to make more printed RC car parts, of course :)

Before you start printing your snow tracks, you'll need some hardware.

This project uses mostly 3mm hardware, but also a bit of 4mm hardware.

I've put this step right at the beginning, because it's probably the part that takes the most waiting time. at least for me, since I'm in Alaska, shipping always takes a week or more, and I hate waiting. So order this stuff before you start printing your tracks.

Here is the parts list for a full set of printed rc car tracks. I've found it's easiest to order all of these from ebay, hardware shouldn't cost more than about $25, depending on which places you order everything from and if you choose to use bearings or not.

m3x10 screws, quantity 8

m3x12 screws, quantity 20

m3x30 screws, quantity 4

m3x35 screws, quantity 24

m3 nuts, quantity 28

m4x25 capscrews, quantity 4

m4 nylock nuts, quantity 4

28 threaded inserts (see the updates, section 17)

3x7x3 ball bearings, quantity 40 (optional, but MUCH smoother)

4x8x3 ball bearings, quantity 8 (also optional, but makes them much nicer)

You will also need locktite, i like the blue because it can be removed without too much trouble.

If you are on a tight budget, you can replace the m3x10 screws with m3x12 (or vice-versa) so you only have to order one size.

You can also replace the m3x30 with m3x35, they'll just stick out more than necessary.

Finally, I've included a set of files that don't use any bearings, because the bearings are the most expensive part of this build. It will work without them, but it will probably wear out pretty fast.

In addition to hardware, you will need material to print your tracks out of! Uses approximately 500 grams of PLA, and about 100 grams of ninja-flex.

I order most of my filament from Matterhackers, partly because they always honor their free shipping policy, and partly because I know I can trust their filament. However, it's a bit more expensive. The light blue color used in this build is their pro-series PLA, in the color "light blue".

For the tracks, I've been printing in ninja-flex, but if your printer won't handle it, you could probably get away with one of the other flexible filaments, such as TPE or soft-pla. I haven't used these before though so i can't guarantee they will work, but they should. All of these are available from Matterhackers, but again you can order from anywhere you like.

You may also want some Sugru, if you want to use these tracks on a truck that doesn't use axial scx-10 axles, and you aren't comfortable (or don't want to bother with) designing your own parts.

Here are all the files you will need for this build. These are specific to the Axial SCX-10 axles, but if you want to fit them to another truck the only piece that needs modified are the anti-flip bushings (there's a front and a rear.) These parts wrap around the axle and prevent the whole assembly from flipping upside down.

I've printed all parts in .15mm layer heights, but the drive cogs, hubs, and frames also print well in .2mm layer heights. you may be able to print even thicker, but i haven't tested other layer heights.

I use 2 shells and 33% hex infill, which works pretty well and results in a strong enough part. If you are worried about strength, the frame can be printed with higher infill, but the other parts don't need it since they are under very low stresses.

The only parts that need support are the frame and the anti-flip bracket. i like to lay them flat on the bed as this results in the strongest parts with the tightest dimensions (just the way they are shown in the photos.)

The parts you will need to print are:

2 copies of Frame (with or without bearings, i suggest bearings because they make it much nicer, but cost a bit more. If you are going to use any bearings, this is the place to use them.)

2 copies of Frame(mirrored)

2 copies of anti-flip bracket

2 copies of anti-flip bracket (mirrored)

2 copies of rear_axle_anti_rotation (if using scx-10 axles)

4 copies of hub

4 copies of drive cog

32 copies of idler hanger (these print well at .15 layer height)

40 copies of idler wheel (with or without bearings, if you are trying to save money these will work without bearings, they'll just need drilled out to 3mm so they spin freely after printing)

The track is a special part, and can take a long time to print if you've never done anything with ninja-flex before. The first thing to do is make sure the filament is supported between the drive cog and the hot end, as much as possible. I always use a temp of 230 to print ninja-flex, but you might try 240 as well. Lower temperatures didn't want to work with my printer. I also have a feeling that 3mm filament is a better option here, as it's a bit stiffer, and less likely to bind up in the drive wheel.

There's a very good walkthrough on how to get your printer set up for ninja-flex, on WordPress

Optimal settings specific to the track:

1 shell (or loop, or perimeter, whatever your slicer calls it)

skin thickness = 0

infill= hollow

I use a layer height of .15 and extrusion width of .4

Settings specific to kisslicer (may also apply to other slicers)
disable crowning by setting a negative value

maximum flow rate of .9mm^3/sec

I set the jitter to 20 degrees, this makes sure that the seam doesn't line up creating a weak spot, but also doesn't jump completely across the part to begin the next layer.

These settings should ensure that the print head moves cleanly around the track twice for each layer, without ever having to make small movements to fill in small spaces. With a .3mm nozzle, I can print a single track in about 7 and a half hours. A .4mm nozzle on my printer will do the same track in less than 6 hours, and if I had a .5 nozzle to play with I could probably do a single track in maybe 3 hours. The lesson i learned here is "use the biggest nozzle you've got for printing the tracks."

I've included the files needed to create the bushings that keep the track assemblies from flipping around the axles.

I like to print these out of ninja-flex, with a skin thickness of 1mm, and a hex infill of 20%. this gives them some flexibility and allows the tracks to move, without stressing the axles. However they would work just fine printed out of PLA or abs, they would just be a lot more rigid.

A third (untested) option is to mold them out of Sugru. All they do is conform to the inside of the anti flip bracket, and the outside of the axle. When you assemble them you'll see where the bracket rotates around the axle, and how it should be fixed in place. If you use Sugru I would lightly oil the parts first so you can get them apart later.

Here's a link for Sugru from Amazon, you'll probably need one packet per corner

Install the m4x25 cap screw (which should be a cap screw instead of another type of head, due to fitment) into the hub piece as shown in the picture. It should be a tight fit, with no wobble. Make sure it is flush with the back of the hub, and not protruding. I usually tap the bolt in with a hammer to make sure it goes all the way in. Support the part using a vice, but don't close the jaws all the way onto the bolt or you'll damage the threads. Leave the jaws loose so the bolt can slide through while you tap it.

If you are printing the version with bearings, you'll want to add them now. These are the bigger bearings, 4mm inside, 8mm outside, and 3mm thick. You should be able to get them started by hand, and then seat them all the way with either light taps from a hammer, or with a vice or pair of pliers. Try to get them in straight, so the tracks will roll as smooth as possible.

Don't make this too tight! it's very important that it be able to spin freely, and it's better to have it a little bit loose than too tight. Your bolt won't protrude as far as this one does, this is what happens if you use a 35mm long bolt instead of the correct 25mm bolt. You'll note that without the nut tightened at all, the hub should spin extremely easily in the bearings. Tighten the nut up until it gets just a bit harder to spin, and then back the nut off so there's a little bit of end-to-end play.

If you opted for the no-bearings approach, you'll want to drill out this hole to 4mm, so that the bolt and hub can spin easily, and maybe even use some oil or grease. If you print in PLA and don't use a bearing, this part is likely to melt without some grease on it, due to friction.

If you are using the idler wheels with bearings, it's time to install the bearings. If you are doing this as cheaply as possible, this is probably the best place to save a few bucks, by skipping these bearings, because there's 40 of them. It will result in your truck not rolling as easily, however.

I like to install them with a pair of pliers or the vice, but a hammer will work just as well. just don't hit them too hard and mess up the bearing or break the plastic wheel.

These use the m3x30 bolts, with nuts, and definitely use locktite (or longer bolts with nylocks, but I like the shorter bolts because they don't stick out any extra.)

These need the m3x35 screws, again with locktite

I find it's easiest to bolt the hangers on first, and then run a screw all the way through and catch both idler wheels at the same time. I like the look with the nuts on the inside, but either way will work. Notice how the bolts go all the way through to limit how far the hangers can pivot, this gives it some suspension but keeps its form.

You'll need to remove the wheels from your truck first, and then slide the rubber bushings onto the axle. Here I'm installing the track on the front driver's side corner of a Gmade GM52000 but the process is exactly the same for any other truck.

The bushing slides over the axle, and then the bracket slides over the bushing. these work together to keep the track from rotating around the axle.

If you are building these on an scx10, I've included a file for a part that slides over the rear axle and makes it much easier to build a bushing around. I don't have pictures of this part since i don't have any of them built right now, and I don't have my own Axial truck to photograph :(

The file I've included for the drive cog uses a 12mm hex, which seems to be the most common among RC cars. if your car doesn't use a hex, you can certainly print your own hex adapter. Just make it deep enough so the end of the axle sits flush with the inner surface of the drive cog, as shown in the first photo in this step.

Here I've used some brass threaded inserts, placed in oversize holes, but since I've only been able to buy them in packs of 100 from mcmaster-Carr, and they cost about $25 for a pack, I omitted them for this Instructables. The screws will thread just fine into plastic and will be more than strong enough. You can see i'm only using three screws instead of all five and I've never had an issue.

Using your m3x12 screws, attach the hub to the drive cog. I'm sure m3x10 screws will work just as well, they just won't go in as deep but should be plenty strong.

In the second picture, I'm using m3x10 screws to hold the bracket to the frame. This keeps the frame nice and solid.

You're almost done!

All you gotta do now is add the tracks, and you'll be ready to rock and roll! Try not to stretch the tracks farther than necessary when installing them, they have quite a bit of stretch to them but they will end up a little loose if you really yank on them.

Tread direction isn't important, but the "proper" direction is as shown in the photo.

Check out my YouTube Channel for more videos of these tracks in action, Including a set mounted on a 2wd Duratrax truck.

If you'd like to stay up to date on my development of a set of tracks for 1/24 scale micro crawlers, you can check it out over at RCcrawler.

Hopefully you had as much building these tracks as I did designing them and playing with them. If you liked them and think this is a cool project, please vote for my Instructables in the 3d-printing contest so I can try to win another printer and design more cool RC stuff.

For anyone wanting to make this that doesn't have access to a printer capable of ninja-flex for the tracks, here is a link to my: 3dhub

9/29/15:

I realized that the drive cogs still have the holes in them for threaded inserts, so here is a link to the threaded inserts i used (opens in new tab):McMaster threaded inserts

Here is another link to some on ebay that i haven't tested, but should work just as well. You will need 3 of these (28 used, total, including 2 in each frame. Opens in new tab): Ebay Threaded Inserts

Additionally, at the request of KentH5, I've added step files for the anti flip brackets and bushings. This should be helpful for modifying the tracks to fit your particular vehicle. These will need mirrored to fit the other side.