Side Projects - Robot Tank

[pRoFiT]

Hey guys. Sorry i'm not on here much right now. Just had a grandson and that took up a lot of my free time. He's 10 months now!

Garage is full o crap right now. Hard to work out there. Need to do some spring cleaning before i get back in there and building

Right now i'm working on a Robot Tank project. To small to ride so i cant enter the 2019 build off.

Here is link to my build on hackaday.io

https://hackaday.io/project/166238-robot-tank-w-jetson-nano

go follow, comment if you want.

I attached a quick photo of the track printed. It's getting large. About 17" long so far.

I picked up an Ender 3, 3D Printer. And have been having fun printing things.

With the grandson i'm sure I will be back in a couple years building things for him. Wife just got him a lambo with remote control! and 3mph is not fast enough i think.

Like this one
https://www.youtube.com/watch?v=xgwuop1-INI

I see 12volt mods. so that may be in the near future.

Time to start sourcing parts. low profile go kart wheels, suspension, large electric motor, roll cage?

 

[JTSpeedDemon]

This'll be interesting.
Good luck!
Congrats on the grandson! I am currently holding my 5 mo. baby sister, Mary.

3 mph is too slow. But hey, it might lead to go karts, and it's a Lambo!

 

[pRoFiT]

yah i've been looking for a used corvette power wheel that i could make into a fast gokart....still looking Not sure if i will be allowed to touch the lambo

 

[Hellion]

Loooks like a great project pRoFiT. Good to see you back at it.

What are the dimensions on your tank? How big is it gonna be?
I love tanks or tracked vehicles in general.

 

[landuse]

Welcome back!! I look forward to seeing the progress on this one

 

[itsid]

Nicel looking tank treads!

but if large equals to heavy...
the driver wheels doesn't look like it's going to last for too long I'm afraid;
those teeth might be chewed off in a matter of a few minutes of rough ride;
and the idlers might not be up to carry much weight either.
And since we're looking at what 60-70 hrs of printing time there,
It's a good idea to load test the print before you print the other track

You might want to check IvanMiranda's youtube channel.. a nice spanish guy
in constant failure mode printing cool stuff incl several iterations of various tanks
and perfecting the treads for reliability (Hence I mention him here)

'sid

 

[pRoFiT]

thanks sid. yah i've seen his videos before.

for printing time so far.... 4 days at 4-5 hours to print the tread. the rollers about 4-5 hours to print 3 plus holders.... several prints on the drive wheel. i need to print one more design change to it. and 4-5 hours to print the lower brackets with the free wheel.

so ~35 hours in so far. for one side.

i've made a couple changes in there so add another 12 hours failed parts.

so far im still on my first role of PLA @ ~$25 and i purchased another one so im ready when i run out. plus i have a roll of TPU which is the flexible plastic. not tried yet. but want to use it for something.

The PLA is really strong. I have ran the track for 30+ minutes so far. the drive wheel catches a little so i need to make it a smidge larger.

the overall length is 15.5 inches right now. and the track width is 2.5 inch.

This is a small robot and wont be going really fast. The steppers i have are 0.9 degree at 1000 steps a second at the fastest. probably run around 300-700 steps a second. with a possibly a 3:1 ratio i think. i may swap the steppers for a normal 1.8 degree step to get faster speed. i have a couple laying around i can try but they are twice as long.

spacing is about 0.55 inch between treads. with a ~2.5 inch drive wheel.

frame is 1/4 inch aluminum

So far i can pull real hard on the track without anything breaking....but yah once i get the other side and some more weight on it maybe i will have issues. can always drive slower

i put springs in the lower ride wheels so i have some good give on them.

I could always redesign the tread to have 3 points of contact with the drive wheel spend another 60 hours printing...

it's a learning experience.

p.s. for inside use robotics platform. Not intended for outside speed racing but maybe?

---------- Post added at 11:55 PM ---------- Previous post was at 11:33 PM ----------

Okay i tried running some numbers.

Max speed ~0.446MPH (3 inch wheel total (track and wheel), 150 RPM, 3:1 ratio) But i could be wrong on the RPM of the stepper. trying to figure that one out.

So about ~41 Feet in a minute. that's ~0.68 feet in a second. and ~8 inches a second.

all approximate numbers.

i need to figure out RPM on stepper next. to be more sure on these numbers. some searching say steppers can be driven up to 1200 rpm? if enough power and the right circuits.

but then some say 600RPM . if thats so mine is 0.9 degree so probably 300 RPM? that would double all my numbers in speed. 1MPH! super fast

---------- Post added 07-03-2019 at 12:08 AM ---------- Previous post was 07-02-2019 at 11:55 PM ----------

Oh sid perfect guy to help me figure this out.

I have 6 6V SLA batteries that i was thinking i could use. also 2 12V SLA batteries i think 4AH

Thinking about putting the 6V ones in series parralel to get 12V at 12AH? 2x3. Whats a good way to balance charge them? or should i charge 6V one at a time? would like to build/buy a charge and put into robot if possible... or an external connection that can charge them all at once.

Any ides?

or i use the 2 12v SLA and have 8AH. Not sure what my overall power consumption will be. Steppers pull 0.4A at 12V when idle. and way less then running. like 0.2A and i have two of them so Max 1Amp draw at 12volts. plus i have other components that may need another amp or 2.

Hoping to get a couple hours out of it..may need more batteries or switch to lithium pack.

 

[pRoFiT]

Well some updated robot tank pics.

I received some laser cut parts from a friend. So tracks are together and base plate is assembled. slowly moving on this one.

For size ref. I think the steppers are NEMA 23

Overall width/length is about 15"x15"

I have 2 12vdc 4mAh SLA batteries im planning on starting with. Maybe get a 20MAH li-ion battery to run it all. not sure yet.