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

Hey this is awsome!



Nice to see im not the only one who uses inventor for the design stages of modding

 

You Are A Genius.

 

This website is turning into monster garage looks awesome, I love it!

 

thanks a bunch for the info starman, I'd be glad to hear any other insight you have on the topic.

the person i was working on the electronics with also suggested FETs, I must look into that.

The problem we are having now is that the motors are not delivering up to spec, or there is something wrong with our driver that the scope isnt showing. We have a very clean block signal going to all the phases, but the motors promptly lose torque in proportion to how fast we can go.

I called the vendor and they speced the motors at 400RPM, 486 oz-in of torque up to that.

Right now we can't get it above 30rpm at no load. If we try going anything faster or too close to that, the motors just shudder. The car can't do anything but crawl right now because if it goes any faster there isnt enough torque.

This is unfortunate because I used stepper motors just to get away from the current and torque issues of normal DC motors, but controlling these stepper motors has turned into a nightmare. Anyone with insight on controlling stepper motors, or something i may have overlooked, please post!

The amount of torque these motors have at low speeds is incredible, and I can't wait until I can see this torque at faster speeds!

Also starman, we have considered putting in the velocity curve/acceleration smoothing once we start dealing with higher speeds, but for now that isn't an issue. I think the reason for that chip exploding is that it has been abused before, and the load for driving these needs to be spread out over some more chips in parallel. Thanks for the comments so far guys.

 

Why did'nt I think of that?!










ooh.. right.. I'm poor..

 

lol nice

 

schweet~ makes me want to build something similar~ you've done a great job so far, it looks like it needs camo imo, u could stealth a webcam into a turret, get a servo, and have it turn the turret to get a look around. Get more than one and enjoy 2 dimensions i'd like to see what all you do with it at this point, cause its totally cool~

 

I happen to know the owner of http://www.hobbycnc.com, so I will talk to him and see what he has to say! good luck and it looks great!

 

Awesome, anything you guys could possibly help me gain insight into would be amazing, because we are horribly stumped. Just some background on my neighbor: About 5 or 6 years ago he stopped working with my dad at Chevron-Texaco and started his own company building computer control and monitoring systems for oil refineries, water purification plants, and all other kinds of industrial environments. He is pretty familiar with stepper motors, but has no gone as far as to try and make his own driver, let alone integrate one with some computer control. He has enjoyed working on this with me, but as I said, we are both horribly down about this issue.

I am going to call the stepper motor vendor again and make sure that he had the right specs on this motor for me, if not I'm gonna make them exchange it for what I need because I have wasted so much time trying to figure out what is wrong with this

thanks guys, I'm glad this thread has finally gotten some more attention so that I can benefit from your advice

 

The next step:

Since I am currently dead in the water with the speed issue, I am going to work on some other stuff:

I ordered the Polycarbonate sheets from Mcmaster-Carr (www.mcmaster.com) and need to drill a lot of holes in those when the student shop opens back up after this break is officially over on campus. I'll have pics of my progress with them.

The other thing is the parallel port plug. Currently I use a modular plug type thing that sticks out almost 2" from the laptop. Since the laptop barely fits in the car, the plug sticks out into the middle of the tread, something that won't work out once the body is on. I have to reduce the depth of the plug to under half an inch.

What i'm thinking of doing is making my own parallel plug that only has the pins I need, to reduce the work i need to do. I am going to shape it out of a block of aluminum, 2 small pieces that fit together, and some little pins to center it properly on the parallel port on the laptop, basically a scrawny no-frills parallel port plug.

I was going to buy the aluminum block from mcmaster as well, but came across something at work during my break. I work at a place that makes theatrical lighting equipment, and in the metal dumpster I saw some scrap Pipe Clamps that were being discarded after being subtracted from inventory. After work I climbed in and grabbed 3 of them, as they are nice sized solid aluminum clamps, and each one has 4 or 5 places that I could mill the pieces out of on the vertical miller. I checked with the vice pres. to make sure this was ok with him, re-using their scrap material, and he gave me the OK after promising I won't use it as a pipe clamp, since it could hold them liable if it fails...

By the way, thanks to the machinists at L&E (the lighting company) for punching out those motor plates on the CNC Turret Punch, much appreciated. They were also kind enough to weld them on for me, TIG welding which can be rather pricey if I had to pay for it to be done somewhere else.

Anyway, I'll have some CAD of my idea for the port as soon as I get some free time. Below is a picture (click to enlarge of course), of these pipe clamps that I will be using as raw aluminum for the parts for this little parallel port thing.

Now I just have to figure out how to electrically isolate the pins from the aluminum body easily. Maybe I'll just make the plug out of some scrap polycarbonate now that i think of it... heh.


Just to give you an idea of size, it is 1.00" thick
More info to come once the mail room and shop open and I can get the poly carb and start working on it

 

K, this is whats known as a semi-update.

New pictures:





Polycarbonate body panels (with that white stuff stuck on the outside to protect them):


I GOT MY DREMEL!!
I have wanted one for quite some time, and it finally arrived today. First thing I did was grind down the welds on the motor plates to allow the body panels to sit perfectly flush on the frame, here is a picture just because I'm proud. (I also bought myself a digital caliper )

 

hehe thats tight

 

Man thats so cool, i remember seeing this but i forgot to suscribe, i love to see PC's implemented with Radio Control stuff, makes it a lot more interesting, and more fun to play with. Good work so far! Keep it up !

 

This is definately a great mod! Custom RC PCs are one thing, but a fully fabricated, home made TANK PC is awsome!

I hope you get the motors working properly, I'm not at all good with programming, but have you double checked your variables and decimal places? sometimes small tings like that can affect the larger parts.

Do you plan to make the exterior of the Tank itself look very similar to an actual tank? or is it just going to be a platform for the Lappy?

Also, I noticed that the chain sags a lot along the top of the rotation, does this affect your (limited) mobility? I think that maybe some pully wheels, that the chains can rest on, and spin over might help, as well as make the overall appearnce moce "Tank Like". You could also add some pully wheels to the lower tread area for looks too. Just a suggestion Maybe something for the final touches of the exterior, once you get the motors working to thier full potential.

Bravo

 

Really nice... Keep going.

How big is that going to be, btw?

 

The motor issues are not from the programming, we have also tested the elctronics with an electronic timer stepping in for the laptop (timer emulated using a basica stamp II), and we had the same problems. The driver circuit has something wrong with it, and we're trolling for ideas right now as to what to try.

As for appearance, the laptop and everything will be inside the body, I just had it resting on top for testing purposes so that I could see the output of the program. In that picture the USB joystick was attached directly to the laptop, but that is also for testing purposes, my desktop wasn't working so I tested it directly rather than over the network.

There are no tensioner pulleys because this sag in the chain you see leave the perfect amount of tension in the chain. I can always adjust the tension by loosening the bolt in the rear corner, and slide that forward/backward to loosen/tighten the chain if i need to. It also allows me to take the chains off very easily.

For now I am just going to have the polycarbonate body, but maybe I will add something more creative later on, or on the next one of these that I build (yes, I plan to make another one, to use what I have learned from this one), but that won't be for a while. I'm currently more interested in getting this one fully functional and self contained. I think eventually I am going to use the idea of stealthing a camera into a functionally rotating turret, but that will also come later.

As for size, the frame is 5.5" tall, but it stands just under 7" from the ground to the top. The frame is 11.5" wide, but with the treads it is closer to 15 or 16" wide, and the tank is 18" long.

 

Looks cool, reminds me of this one





http://www.fordie.se/jesper/Andras/badgerpackaging/

Edit: Sever down at the moment

 

thats a little bit crazy ...
also, I'm thinking about etching something into the top panel of polycarb... is this a reasonable thing to do with the dremel? I also need ideas of what would be appropriate to put on there

 

nice, thay have something like that at my college except theirs has a web cam on it and they drive it all over campus and stuff. they have another one that is automated and learns the terrain via sonic sensors. maybe you should ad a web cam to this bad boy and drive it around a mall or something. that would rock!!

 

This week's lesson learned:
Always have extra dremel cutoff disks handy. I was using my last one to work on the body panels for the NetCar when I managed to.... step on it.

I also learned not to mix up the battery leads.... managed to kill a couple more chips.

Lesson learned: keep spares

two extra sets on standby in case I manage to blow something up again

Recent NetCar pic, just gives an idea of how panels might look on it.


other pictures out of boredom:
I've, uhm.... bought a bunch of stuff, both tools and materials/consumables for this project: