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

TOM Tri-Track dual servo robot tank chassis

by krux Mar 17, 2012
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Could you tell me the servo model that you have used? ty

what is the angle between the two parallax sensor ?

not sure. it was an arbitrary angle I chose because I thought it looked good. nothing scientific about it. ideally you would match it to the pick up area angle, so you didn't have a blind spot immediately in front of the robot.

I've got this basically built, THANKS!

Only thing is, how did you connect the servo's to the drive sprocket?

I used the servo horns that came with the servos. You should be able to screw them into the drive sprockets.

i am building this one for myself on an uno. great design. however, i need a way for it to keep track of its path, can you suggest anything?

I'm just getting started with 3D printing and I've been looking for a software that would allow me to place the boards I plan to use (given that they're popular enough), kind of similar to Fritzing but for 3D modelling.

One of the images you included has two boards at the bottom and the servos, and the boards have some of the components on them - I'm wondering if you manually modeled them or if you used this magic software that I hope exists...

Manually modeled in Sketchup. There is software available for Eagle CAM which will render boards, but I never installed it, since you still need to create models of all your parts. For as often as I need that, it's easier to spend some time with some digital calipers and draw it out myself.

So far so good with my build. Thanks for this. I'm building it with my 7 year old daughter. We have an uno, a due, and a mega. It looks like the uno should work. I can't see what shield you have stacked on there. Can you point me in the right direction?


Yea, I'm using an Arduino UNO. Though anything would work. As for the shield, It's just a basic prototyping shield I used for mounting the servo headers, and the I2C switch I needed (which knowing what I know now, I would have just did better research on which sensors I was using to make sure you could change their I2C address so you could run more than one) Then the top most is just some protoboard I made into a shield to mount the PING sensors, since I didn't like the idea of having a third servo to be able to sweep a single sensor back and forth.

SparkFun has one here: https://www.sparkfun.com/products/7914
Adafruit also carries a prototyping shield: http://www.adafruit.com/products/2077

Of course both places also have things like GPS shields, etc.. You don't really need a motor shield, since to drive a servo, you really just need a three pin header. I modified my servos for continuous rotation, but you can also buy them that way from sites like HobyKing which have a good servo collection.

Another question , could you mention in the BOM for hardware where some bolts and screws are ment for? Are the bolts included for mounting the drive train to the servo, how many 2 or 4? I got a 3kg /cm and 60 degrees in 0.16 is that fast enough? They are continuous rotating.

Does somebody have an arduino sketch for getting this thing alive?

I uploaded the sketch I used. It's only reading values from two PING sensors at this point, and does obstacle avoidance.

Thank you! I see you use normal ping sensors with 3 pins . I got the hcrs04 (4pins) sonar sensor which can make use of the Newping library. So i should adjust some of the program.

Hi friend what sensors brand type are you using there below.

The sensors on top are Parallax PING sensor. They work great.

The sensors on the bottom are the Adafruit VCNL4000 Proximity IR sensors. Unfortunately, I would avoid using these at all cost. What they didn't make clear is that you can't change the I2C address of these, which means you can only normally run one sensor. Since I have more than one sensor, I had to try and hack it together using an I2C bus switch which lets you run multiple I2C buses. I then got busy, and haven't had a chance to write the code for them, so at the moment my rover is just using the PING ultrasonic sensors.

Ok thank you, i think i get some QTR's Pololu like

FYI, I updated to the latest version of the sketchup file for the robot. There is a sensor mount that I added as well.

oh wow, 1/2 thought printing this bad bay, very awesome, thank you krux!!!

any idea where I can fine some of the needed sockets/bolts/nuts? I don't think HomeDepot will cut it this time...

oh, and why have triangular track profile as opposing to having a flat robot? is it because of the way servos are mounted ? or is there some other advantage in elevating the driving gears?

McMaster-Carr is a good resource for hardware.

Great design! I'm about 30 minutes into my first print of it now on my Replicator 2 :) Printing everything but the track parts in one run. I'll let you know how it goes.

Great, it fits the Hitec HS-303 Servos too

You track plates seem to be broken - whether skeinforge nor slic3r does render them correctly. They have open surfaces.

Thanks for pointing that out. That was likely in the original. However I did remake the tracks, as track.skp file is a remake of the track from scratch in google sketchup, so that exported to stl should be fine. I just had not exported the single track to a stl, since when you need 42 of them it was best to print multiples.