Tracked Tarmo

Work In Progress (Edit 14Jul'23 - less WIP now - more Test the Current Iteration)

***Important notes at the bottom***

I want a tracked vehicle.  No idea why, but I still want it; I also have a budget, so I want to use the parts that I have on hand and seem to work - Tarmo5 parts!

That said, I did look to see of there was something I liked out on the interwebs…

I looked at the Fast Rc Tank by #Froy192, and while I love the design, I didn't want to shell out the $200CDN for the gearsets and motors.  

That track design though…  Hmmm…..

A chassis. I noted the mirrored 4WD body by #Willy.  With the 1 motor end from his WIP chopped up and swapped around to allow 1 motor to drive each track and keep the weight balanced L to R, then lengthened to accept a 5200mah 3s pack…  Hmmm  again….

Sadly, I recently gave up on my Tarmo4 (more shredded gearboxes than I care to count), so I now have a full ESC and motor set, along with the spares I always like to keep on hand.

So all that in conjunction with my desire for tracked goodness and………..

TRACKED TARMO!!

This might work.

(Edit 14Jul'23)

This is working!  With the PETG drive wheels it seems to drive well. I haven't broken anything yet, though the track has distorted a bit. The crimps are a bear to get right!  It sucks back power - good packs are a must and keep the remote set low!  I still haven't increased my power past 30% - it's still pretty quick for my tiny back yard.

BOM Printed:

Print off the plates in the material specified (PA is voluntary for those with enclosures and daring… PLA+ seems to work so far for me where the PA parts failed to print).  You'll need 2 track and wheel plates.

If you chose to print the parts individually, print in the number specified in the part name.

BOM NON Printed:

2x 6x 8mm hub – each set in the link has 4 amazon

4x 4.2mm ID x 8mm OD x 4mm standoff I used 2 only - you can also use 8mm standoffs if available - 1 per hub used to center the #4 bolt.

2x 3542 Turnigy brushless outrunner motors (same as Tarmo4 and Tarmo5)

2x Brushless ESC (I'm using 2 10BL120 Quickrun ESCs - spendy, but they work…)

Radio and receiver capable of TRACKED VEHICLE operation.  I am using a Radiolink RC6GS that works more or less…  YMMV and if you have a better (affordable!) option, let us know somehow.

38x48x138mm Lipo pack or smaller to fit the chassis.  I'm using a 5200mAh RoaringTop pack - so far (edit 20June2023) not so good…. Use a much higher C value - maybe 100c - my 50c packs can't keep the volts up when drawn down by both ESCs. (end edit)

HSP 08065 Tarmo4 hex motor adaptor x2 (1 purchased set usually has 4)

1/16" wire rope and crimps - amazon 

15x24x5 bearing x12 - the large Tarmo bearings

***BOLT LENGTHS ARE NOT ASSURED!***  

***I HAVEN'T MEASURED AGAIN AFTER THE PROTOTYPE BUILD!***

***CUT BOLTS DOWN AS REQUIRED AND TIGHTEN WITH CARE!!***

M4x30 hex head bolts x2 I cut mine down to size for the idler wheels.

M4 locknuts x2 for the idler wheels

M4x~32 Allen head bolts x2 for the drive wheels - cut to fit based on washers needed to secure the wheels to the axles. The relief behind the embedded nut inside “2x Drive_WheelSide_v2” is minimal to keep the part strength up, so don't tighten until the bolt has been measured and cut to length or the part will break.

M4 nuts x2 embedded in the drive side axle “2x Drive_WheelSide_v2”

M4x35 Allen head bolts x4 for the gearbox lid

M4x40 Allen head bolts x4 for the motor mount to gearboxes

M4x16 Allen head bolts x2 for the battery securing tabs.

M4x20 Allen head bolts x8 to secure the 2 bumpers to the gearbox covers.

M3x20 countersunk screws x8 to secure the hubs to the drive wheels.

M3 lock nuts x8 and washers x16 to secure the hubs to the drive wheels.

M3x12 Allen head or other x6 for the motor to motor mounts

M4x25 Allen head bolts x6 to secure the Main Gear Hub to the Main Gear

1 ¼" washers x4 - I had to stack up smaller washers with these to lock the wheels to the hubs.

3x M3 threaded rod 250mm min length.

M3 locknuts x6

M3, M4, M5 washers - a few of each depending on the build.

Hook and loop tape to secure the ESCs and such to the chassis.

3/8" to ½" #6 screws x144 for the tracks.  36 links per track seems to fit well.

***NOTES***

So far I have run this build through 2 battery charges without breaking it!  

It still tosses tracks a bit too easily, but nowhere near as badly as the 1st build (a couple battery charges and many broken parts).  Branches and mulch in the wheels caused the track loss this time rather than the sideways glance required to lose a track on build 1.

I can't add too much power too fast or shredded parts happen…                       

****I have my throttle and steering limited to 30% “EPA” on my remote.**** 

The steering is super sensitive, and adds power, so beware!!!

I really want to avoid metal drivetrain parts as that adds cost, but the torque required to move this thing may force me into metal hubs or more…  I hope not  :)

Good luck should you chose to accept this challenge!

Work In Progress

(hopefully this won't stall in its current form - work and life and finding a balance and all.  That said, it works and I'm having fun with it now, so…)

Edit 15June23

As for building the model, it's a Tarmo5 mostly. 

You can follow the chassis and gearbox assembly portions of the build with the exception that the gearbox parts with “captive” and “nut washer side” retain the 3 rods with nuts and washers to hold the model together similar to the T5 but without the nose part to give easy access to the tightening nuts.  You will have to thread M3 locknuts onto the rods and set them into the “captive” side of the gearboxes then fiddle/tighten nuts onto the “nut washer side” of the M3 threaded rods with needle nose pliers. It's a pain, but worked for me…

The track build is detailed in the Fast Tank build.  More or less set the track links into the jig, lay the wire over the links in the slots and screw down the wires.  Trim out 2 links per track to accommodate the crimps to close the wire loops.

The wheels are very tight on the hubs. You may want/need to increase the size of the negative volume for the axle by 1% or so to add clearance if required.  

If a build video is required, maybe.  My editing skills do not exist, and a single take build video seems optimistic… 

Edit 19June23

Edited the bumpers to allow you to remove the gearbox covers while leaving the bumper attached to the cover.

I have been driving this around a bit and found mostly the tracks come off when damaged or you get big crap caught in them - mulch or branches.   

Traction on wood is poor - perhaps 85A hardness track links, or go over to the questionable links ;) on the Fast Rc Tank…  (longer screws and a new finish on your wood and hard surfaces…)  

Be sure that the track cables are well crimped - this has proved to be the source of most of my thrown tracks.  A bad crimp allows the track to stretch at the crimp, or distorts the track, and it pops off the wheels.

(Edit 26Jun'23)

Added the hubs, standoffs and securing hardware to the BOM. 

I found the wheels slipping on the drive at the hex connection to the wheel.  Wallered out a couple wheels, but with the hubs the parts could be reused.

Use the standoffs to sleeve the M4 bolts inside the hubs and clamp the sleeves in place with the hub grub screws. Screw the hubs to the wheels using 4 M3x20 countersunk screws, 8 washers and 4 lock nuts per wheel with the nuts facing out as seen in one of the pics.

(Edit 11Jul,23)

Changed the wheels over to PETG - opened up the drive hex to ~12.14mm to slide over the wheel hub.  The rest of the build remains the same for now…  

We shall see what I break next! :D

(Edit 14Jul'23)

So far so good through 2 charges…

*Testing the Current Iteration*