Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Tri-Track dual servo robot tank chassis

by Ktronics, published

Tri-Track dual servo robot tank chassis by Ktronics Dec 14, 2011

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Tri-Track robot chassis is based on Sublime 100mm wheel base track system. This design incorporates dual servo motors that are mounted above the chassis. This design allows for mounting a robot body or arm between the tracks. The battery pack and electronics will be moved as the design progresses.
Frame has been significantly strengthened to accommodate for the added stresses and to increase weight capacity.


Added platform base for mounting robot body or arm.

12/21-11 Added additional files

Rendered BaseLeft and BaseRight in two pieces, this enables them to be printed on a MakerBot. The two piece files are: BaseleftP1, BaseleftP2, BaserightP1, BaserightP2

There are errors in the Tri-Track Frame file. This fils is still printable. We are working on correcting errors.

Redesigned and added New Tri-Track Frame for Solid Axle construction. File Name: Tri-Track Frame For Solid Axle v1

Short video of Tri-Track in motion:


My plan is to build a two armed robot around this motorized platform.


Original Track design by Olalla
See http://www.thingiverse.com/thing:8559

Servo Mount is by Hoeken. http://www.thingiverse.com/thing:5165 This is printed horizontally for strength.


Instructions and files will be added as the build progresses.

1 - Tri-Track Frame for Solid Axle
44 - Track Sections
2 - sprockets
4 - 608 sprockets
4 - 608 Bearings
2 - Servo Mounts
1 - Base Left
1 - Base Right

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Do the files include the platform on top of the chassis, where there are springs? Also, what are the dimensions?

Hey Ktronics

What kind/ which servos did you use that have continus turning?

Thank you!

These are 360 degree servos. Part # STD-S04NF

What did you design this with? Any chance of getting the solidworks files?

I'd like to double the size...

scale everything up in the slicing program?

hey what pins are you guys useing to attach the track parts?

I used 3mm abs filament and melted the ends. This eliminates the weight and cost of using hardware.

There aren't any models labeled 608 bearing. Are they included in another file?

608 bearing is a ballbearing that you need to buy

What did you use to pin the tracks together. I'm working on a TOM, and the hardware seems a bit much. Building an FPV bot with my 7 year old daughter, lightening the hardware is her idea...

Cool Project!

Hi. i just tried to start printing but whether skeinforge nor the newest slic3r will slice the Tri-Track Frame.stl - both throw some errors, slic3r doesn't even render anything.

Does anyone else have other experiences with the actual files?

Yeah. Johnny5 rulz!

The frame is too large for the ABP. I used openSCAD to clip the ends of the solid axle model, which had enough room and is still stable. For openSCAD users:

cube([96,115,115], center = true);

F6 to compile and render. Then export as stl.

We've enjoyed making this design, thanks!

I own a MakerBot but I print most of my parts on a Mendel Prusa. As I have time I will split large parts into two pieces so that they can be printed on all printers. I am currently designing parts for a robot that mounts on top of this track frame. Thank you for your interest in my project.

Thanks for the multiple parts for the base left and right.

I'm not sure if the tri-track frame will fit the TOM platform. Maybe it too needs to be split into parts.

I tried to "Save Target as.." to the new "Tri-Track Frame for Solid Axle V1.stl" but it keeps downloading as an HTML document. THis is driving me nut. What am I doing wrong? All the other files download properly.

This may be a bug with the New Thnigiverse website. This is the first file I have uploaded to the updated site.

Thanks Ktronics, I thought it was me. It has been driving me nuts! :'(

Firstly... Love your work! It looks fantastic!

Question for you... In Netfabb basic, I'm trying to do a 'duplicate' of the tracks and then save them as one bigger STL, however, Netfabb won't let me save them all as one, even if I have them all selected. I've even tried putting them into a group (on the right) but to no evail.

how can I save them all to one STL?

Hi Dogbert,

Thank you for the kind words. I am not familiar with Netfab, but with other Cad software I use the Import function to add STL files. I uploaded a new STL file called Track Plate, this plate has 4 track segments and will fit on a MakerBot platform. If you or anyone else wants a larger plate let me know and I will build one. I wish I did this when I printed my track segments.

Skeinforge and Slic3r both have options called multiply that create plates in gcode only.

Am I correct in saying that the tri-track frame, baseleft and baseright will not fit on the TOM platform? :'(

Rendered BaseLeft and BaseRight in two pieces, you should be able to print these on your MakerBot. The two piece files are: BaseleftP1, BaseleftP2, BaserightP1, BaserightP2

Thank you for bringing this to my attention. The Base Right and the Base Left parts are 82mm x 138mm. I may be able to add a lap joint at the top portion of the parts. This will allow the parts to be printed in two pieces for smaller build platforms. If possible I will release large parts with two versions a one piece and two piece.

When are we allowed to have the chassis! I really want one. :)

I am working on releasing the chassis. I hope to have this released soon, sorry for the wait. My prototype chassis did not have the screw holes for mounting the servos. I have just completed the platform to mount a body or arm.

Thank you for your interest in my project

This is really cool!!

I love seeing that my original tracks are adapted to other people's designs :)

’re original track design is inspiring new designs :)

Looks great! Have you managed to get a feel for the kind of traction these treads have?

This travels very well on smooth surfaces and carpet. With this being a skid steer design it seems to prefer a smooth surface. I am considering adding some kind of grip tape or dip the outer track in a liquid rubber. This should allow the Tri-Track design to really climb.

I was considering using "rubberized rocker guard" for cars. It comes in a spray can and you can apply an even, thin, flexible rubber coating to almost anything with it.

I used plastic dip. Its for dipping your tools in so they have rubbery surfaces. its sold at home depot, and its more rubbery than the rocker guard.

Im still trying to figure our electronics.

are there any more videos of this in action?


I just uploaded a picture of my first track. I'm very impressed on how well it flexes.

Do you plan on sharing the chassis, bearings, axels, electronics and servo mounts?

Thank you.

For using another sizes for the tracks, you can go to http://www.thingiverse.com/thing:8559http://www.thingiverse.com/thi..., which is from where Sublime derivated its wheel-track system.

There you have the scad files which are parametrized.

Caterpillator v1.1
by Olalla


You can thank Sublime for the nice track segments. I will be sharing two chassis designs; one will have the original 606 bearings on the chassis and the sprockets, the other will use a solid design with only the 608 bearings on the outer sprockets. All electronics and mounts will also be provided. I am currently designing a platform that will attach to the chassis to support the body of a robot or arm.

Your copy looks great, as a finishing touch to my pins I used a micro torch to heat up one side of a slotted screwdriver. With about 2mm of filament exposed on each side I pressed the opposite side of the screwdriver to the filament to melt it to form a flat edge similar to a nail or rivet.

As I said on my thing. I DO NOT USE OPENSCAD so there are no openSCAD files used since Olalla created the originals. If you insist on having a SCAD file for it may I suggest you do it yourself instead of just complaining. That is why I gave the size changes on my original so if someone wanted to recreate it they could do so easily.

Not complaining, just saying that if we want Open Source to work, licenses should be respected. But I did not want to bother anyone. I apologize for the comment if you consider it inappropriate.

I played around with different servo mountings. It came down to personal preference and looks.

If you mount the servos the other way up you wont need so much extra track. You could also lie them sideways for lower centre of gravity.

Will you be using the sprockets from the 100mm design?

Yes, this design uses (4) 608 sprockets on the axles and (2) solid sprockets on the drive servos. At this time I left the axles at the original design, but I did not want the tracks to drive the axle through to the opposite side.

This design just says to me "Johnny5 is alive!" like nothing else.


Thank you, this was Johnny 5 inspired

Your mother was a snowblower!