Project: NetTank -->Page 3 05-20-2005

I already subscribed to this, mainly because it looks like an awesome project, and I love this kind of thing, as I'm on a robotics team at my school. So far it looks promising, and my only suggestion is to find belts of some sort...number one, because they have greater traction, and number two because they are less apt to fall of in the course of while driving the thing (trust me on this, I have experience with both chains and belts as drive mechanisms). Otherwise, looks great!




EDIT: HEY! I started the 3rd page!! pnwed!

 

The car is so heavy that traction is far from a problem, and these chains will never come off, i can promise you both of those

 

Been a while since I had an update. I finished the body panels, procedure consisted of:

1) using the dremel to cut out each panel
2) scribing a centerline on the frame
3) drawing evenly spaced hash marks on the frame
4) peeling the white stuff off the polycarb panels (the cut ones)
5) clamping the cut panels in place on the frame
6) center punching the polycarb right above the marks on the aluminum
7) drilling through both in all appropriate places
8) removing the polycarb
9) etching into the end of the polycarb the orientation it should lie in
10) drilling the holes in the polycarb out slightly larger
11) tapping out far too many holes in the frame (#10-32)
12) putting it all together

The side panels took a bunch of work, because I had to cut out slots for the tensioners/slides, as well as for the bolts and washers that hold on the bottom cogs.

Far too much work to be doing in a univ. dorm room, but at least my roomate goes home on the weekends and I can spread out as best as possible.

I ordered two stepper motors controllers to finish the project off, at least until I can design and build a better custom circuit. http://www.quasarelectronics.com/3179.htm

as always, here is an abundance of pics.





















next week I will receive the controllers and alter the programming to work. Once it is all worked out, I will definately borrow someone's digital video cam and post high-res vids of this thing tearing around my dorm, campus, and where ever else I can capture.

So close to done!

EDIT: Forgot to mention, the car will weigh 70lbs, +/- 3lbs

It will be able to carry at least a 150lb load and go about 5mph before I mod it to go faster

 

wow this is great. I like the idea of a robotic car, but i dont think that the chains were meant to be a driving surface, nor will thye give good traction on say a tile floor? If you had wanted to build a nice tank drive, you should have considered belts.
How much clearance off the ground does the bot have?
With a little modification, you might be able to climb stairs, depending on the traction of the chains.

BTW: i too am on a robotics team linky

 

it is so heavy that traction isnt a problem. I probably wont be on any good tile floors, but i dont think traction will be a huge issue... the 4 chains provide pretty good traction on any surface. Belts would be hard to attach and hard to keep on IMO.

this isnt for a team, i just got bored and started designing this last summer.

I have plans for another one after this, very similar, just with no corners on the bottom of the frame, as the box nature of this one keeps it from any extreme terrain. I also want to make some changes to the size of the frame etc. Once I have this one finished and working in perfect harmony, then work begins on the next one

 

right, i wasnt saying thsi was for a team, i was kinda hinting that im not a random dumass, and that some of what i say is informative.
And IMHO belts arent that hard to use. you jsut need the right kind, and the right set up.
If you want to see some cool robots, head on over to cheif delphi and browse around a bit

 

the other thing is that since this is a skid-steer type of setup, i cant have so much traction on any surface where the motors would have to work their ass off to turn quickly

 

If you can find a way to machine them, using an offset hub (as seen on the HMMWV/Hummer) will give you extra chassis clearance without widening the body or using larger 'road wheels' or bogeys. I'm not sure where to find a decent picture as google image search isn't turning anything up. If you're not familiar with it, the drive shaft enters the hub rotating opposite the direction of wheel rotation. The hub contains two gears: one on the drive shaft, one on the wheel assembly.

wait a tick, why monkey with that? I guess there really is a reason that the drive sprockets on a tank are at the top of the tread! nevermind. I think using a torsion bar setup for the road wheels would give you a fair ammount of chassis clearance and suspension if built properly. Just a thought for future designs.

Other than that it looks like a fun mod!

 

there are a bunch of shops on campus here( www.rpi.edu ), and i can machine just about anything I want. I also am on good terms with all the people I work with at home ( www.le-us.com ) and can get just about anything made on the CNC turret punch and mill at no cost. I hope to learn a lot from this project and create a 10x better version next.

if anyone would like to post some sketches of feasible frame designs, by all means please do ... as well as your comments on the project at hand

 

Nice mod! Maybe you could contact a notebook manufacture, so you can drive around showing it! Would be nice, a notebook driving around cebit.

 

That's a NetTank (not a NetCar etc. which are in the topic)

However VERY NICE job!
Looking forward this one

 

ooooh nice man looks terrible! nice dude go on and let him roll

 

Can't wait to see it completed, righteous

 

Now we only need more people to start making these, then program them to fight, build arena and make like RobotWars competition only the bots would use PC's inside of them to fight, not controlled by inferior human race.

Anyways really nice job

 

alright, the netcar is all done but i have yet to put it together and test it (just moved home from college, no room or time to do it yet)

so, here is what i've done recently:

I received the two PCB boards to control the motors. As soon as I got home I started cutting out the small pieces of polycarbonate to mount them, as well as hold the terminals for the +/- connections to both of the batteries, see pics:

the two batteries are connected via 12AWG wire to a copper connector at the bottom of the terminal posts. I made these copper conectors out of an old copper heatsink. I used a dremel to cut off some fins, then folded the ends onto the wires i wanted to attach. I then soldered them in, and drilled a hole in the middle so that it could be attached to the bottom of the terminal post. Works very, very well

top view down on the mounted PCBs


another view:


yet another:


overview of the whole thing except the laptop:


frame, motors, wires, PCBs,


top view of it with the batteries


this is the parallel port plug that i made from scratch. A normal one would not fit inside the frame of the car. I took two pieces of polycarbonate, used the dremel to cut slots for the wires, then drilled small (i think 1/16") holes for the 20 guage wire to fit through. I stripped about 1/2" at the end of the wire, put it through the hole, sat it in the channel (did this with all 6 wires that i need contact with), then put on some contact glue, and clamped the other piece of polycarb onto it and let it cure. I then drilled two holes for the 4-40 screws, countersunk them, and tried it out on my laptop (see below).

It looks perfect and fits inside the frame just as i need it to. I couldn't find anywhere to buy a low-profile parallel port plug, so this seemed like the best option. the whole plug stands less than 1/4" out from the back of the laptop (again, see below).






assembled with the laptop:


view into the front of the frame when assembled:


view into the side:


closer view into the side:



thats all for now, ill add more when I have it, and soon hopefully a video of it driving around (rather slowly though :-/)

I might also add a sketch of how the PCBs are mounted since it is kinda hard to see all the clear polycarb.


high res pics at http://ww2.u13.net/netcar/new051805/high-res/

browse the medium res pics at http://ww2.u13.net/netcar/new051805/
- the pics starting with m are the medium res, ~1300w. the pics starting with s are the thumbnails, 400px wide

 

If anyone has ideas for a better-shaped frame, please share I plan on making another one of these in the near future, and I want to improve as much as possible

 

Inverse trapezium to follow the shape of the tracks?

 

I thought about that a while ago, it is probably the best idea, except where would i place the motor? if the frame is shaped like


____________________
\x_________________x/
_\_________________/

where would i be able to place the motors? they wouldnt fit squarely in the upper corner like they do now(the Xs are where the motors should be). They really need to be in the corners to get the most contact with the chain. I don't really want to put them on the bottom (say, in place of a roller) because I don't want the chance of the motors being subjected to impact across their shafts, it just cant be good for the motors

 

Well you could bring the motors closer to the centre of the top, and then run a small chain loop from the motor to the 'x' on the inside. This would then power the outside chain loop!

 

Probably a little too in-depth, but why don't you think about working with gear reduction, machining some gears and stuff to make a transmission? We did that on this year's robot, and they actually helped a lot:

I'm not sure if you're planning on driving the NetTank up stairs or anything, but if you are, a low gear option would be much more beneficial than a direct-drive system, plus, you are going to be putting a lot less stress on your chains (though your chains look pretty beefy to me). God, there are so many things that would be fun to do with this thing (gyros, transmissions, pneumatics, etc). Let me know if you need any more in-depth ideas about stuff to do.