Wednesday, 20 March 2013

Cheapness and paintball

I have a Spyder Victor paintball marker, and it is not a bad gun really, it was pretty cheap, and it gets me out on the field. I love my spyder, but I used to wish I had a longer barrel, the stock one was just not cutting it. I am a bit poor right now, and I balked at the ~$40 price tag of a nice barrel. Having just built a paintball cannon for my friend, I knew that 1/2" class 200 (thin walled) pipe fit .68 cal paintballs just fine, I also have acess to a lathe, so I figured, what the heck, I will give it a try. I measured my stock barrel's diamiter, and the legnth of the part that screws into the gun, chucked up some pipe in the lathe, and here is what I got:
admittedly, the white plastic looks a bit cheesy, but I can paint it later if I really feel like it, and the price is right ( you can get 20' of pipe (yes feet not inches) from any self-respecting hardware store for less than $5) the barrel might be a little long, but I can always cut it down later if I need to. I fired a few test shots, and it seems to work fine, no chopping, and better accuaricy.
You might have also noticed that in the pic I have a HPA tank screwed onto my gun. Also in the persuit of money-saving, I purchased it and the fill station you can also see in the pic, tank was ~$40 and the fill station was ~$20 from and ebay respectively. The fill station screws onto a scuba tank, and lets you fill your paintball tank anywhere you can lug a scuba tank. I borrowed a scuba tank from a friend, and since I can get it filled for free, I will have paid for my purchases in 6 fills, not bad considering I plan to go more than 6 times in the future, and my a few of my friends who do not want to shell out for all the new stuff said they would buy HPA tanks and buy fills from me for ~$2-$3. Doing more with less FTW!

Friday, 15 March 2013

Rambling #2 (Thoughts on Bots)

What do you get when you cross this Gripper

 and a quadroped like this?

Well, I don't know, you could get a number of things, but, I propose that you could have the makings of a pretty sweet wall climbing robot. Just get 4 of those grippers, mount them on the feet of your quadroped, and alternate "ungriping" one foot while the other 3 are stuck, moving it forward a bit, planting it firmly on the surface, sucking all the air out agin and repeating for each leg. It would not work on smooth surfaces like glass, but deffenately on brick/concrete walls, and maybe even on drywall.

Rambling #1 (Thoughts on Bots)

I have been interested in mini-sumo for a while, and I was thinking about how I could make an (almost) unbeatible robot. I have come to the conclusion that competeveness comes down to a cupple important things: traction, low profile fronts (traction does no good if the other guy gets under you and ruins it all.) quick response time while searching, and just enough power to push the other guy out. Ideally, tank treads covering the whole (or almost anyway) with a scoop that deploys down would be the best (have a look at "the beast") However, building something like that is out of the question for most hobbiests, so I have come up with what I think would be almost as good, namely a walker. Now before you call me crazy have a look at this pic, and see that the walker I propose is not your average biped.
As you can see, the walker has a shell that moves around a round inner piece in a oval fassion. To see a more detailed discription of how this works, have a look at this link. This bot was not built by me, but it explains the walking method rather well. Anyway, the two pieces (circle and shell) need to have the same area, so it has equal traction when it is up as down (the importantce of this is evedent if you have ever seen two of these things push each other around (I built a similer bot using the lego mindstorms NXT system a while ago to vs against my friend in sumo, his robot had rubber on the shell, but not in the middle, and he lost ground every time his shell lifted in the air.)) So a little math (and help from a math teacher) later, and I figured out the required diamiter of the circle, and drew a scale drawing:

The bot will have almost ( the walking method requires some blank space, as evedenced by the drawing ) half of the possible area on the ground at any time, and sometimes all of it, which, if covered with an approate high-traction material will give a ridculas amount of grip.
The centre circle will be driven by a gearmotor in order to turn the bot, it does not need to be overly powerful, but fast enough to spin the bot at a good enough rate to not let it get ambushed from behind. The walking mechanisim will be driven by a cam system much the same as "clunkers" but with a much smaller cam, the bot does not need to take big steps, nor go fast when pushing, and will be able to get by with a less torquey motor.
At the begining of the match, the front plate will fold down giving the bot a nice low profile wedge front, and will also be hinged as in the picture so that if a robot hits the side of my bot instead of dead on the walker will still possibly be able to get under by continuing to rotate. As for opponent detection, just about any method will work, be it mechanical, optical, or sonic.
I know, crazy, but I think it might work.....

Thursday, 14 March 2013

HOG getting closer...

I worked on the hog drive again last night, I made a gimbal bracket out of lego, hot glue and a servo. Ultra high quality I know, but 1, good enough for a prototype, 2, I was going to use aluminum, but lego is better for rapid prototyping (that, and my hacksaw does not have a blade right now...) 3, lego is still pretty sturdy, and 4, the rest of the frame is going to be lego anyway, so the bracket and base should fit together fine.

Some pics of the bracket:

And a frame around it:
The gimbal that you see is for driving, and can move 180 degrees left and right. To steer, it will rase and lower it's rear wheels in tandem, causing a tilt of the whole bot to a "nose up or nose down" attitude. I sort of struggled on how to make the whole bot run, I have seen both a straight up 2 axis gimbal, and one bot that independantly rased or lowered each wheel to drive and steer.  I chose the hybrid method because I wanted to have maximum travel latterally so that the whole hemisphere could be used for driving, and max top speed could be reached, and to do this with a regular gimbal would have been tough. I will not get max travel for steering, but really, I do not need to turn at 150 km/h, that is just a bit excessive... We will see how this system works for a first prototype.

Tuesday, 12 March 2013

Physics FTW!

This guy's whole channel is awesome...

Minigun complete, now 20,000% better!

Yesterday I finished up my friend's paintball minigun. It now has a continous sparker system, chamber fan, 3-1 chamber  to barrel volume ratio, is very well ballenced, and has the ridculas amount of power I have come to expect from any projectile-hurling device I build.

Chamber fan:
Battery pack:
COMPLETE! shown with end cap, paintballs, and starting fluid.


 As to that 20,000% better remark, it was not just idle speculation/exaggeration, before the chamber fan was installed, sometimes the paintballs would only shoot a foot or two, due to incomplete combustion resulting from a less than ideal fuel/air mixture. With normal potato cannons, this is not such a big deal, because the potato generates friction, which keeps it in the barrel long enough for all of the fuel to burn, and thus develop more pressure, enough to hurl it a long way. Paintballs do not have as much friction, so the inital burn will propell them right out of the barrel, with really crappy force. The chamber fan ensures a full burn almost instantaniously, and thus all of the force is developed within a small fraction of a second, resulting with WAY more force. Now those 7-35 paintballs go over 200 feet, thus, 20,000% better.

Monday, 11 March 2013

Progress on the HOG drive

I have been working on the HOG drive a bit recently, I went to the local dollar store and found a few hemispheres that I thought might work:
A rubber ball that could be cut in half, a plastic wind up toy, and a rubber "popper" also shown are the bell from the motor I am using, and an epoxy putty stick from harbour freight tools.

Eventually I settled on using the smiley face popper, because it was already a half-sphere, it was rubberey (good traction) and it had a nice center hole right in the middle. I kneeded up some epoxy putty (REALLY nasty smell...) stuffed it into the popper, and pressed it onto the face of my motor (I had cut down the shaft erlier, and thredded two nuts for more surface area for the putty to grab on.), made sure it was centred, and let it cure for 24 hours, here is the result:

From just eyeballing it, the hemisphere is perfectly centered, and spins fine and true at 8000 RPM. The putty ensures that the ball will not deform at high speeds, and has had no problem holding together at those ridiculesly high speeds. Speaking of high speed, I did some calculations, and the theretical top speed of this thing is going to be somewhere over 150 Km/h, not bad for something so small....

Wednesday, 6 March 2013


I woke up this morning, and found sitting on the dinner table my prizes from the LMR tic tac toe challenge Naughts and Crosses. I decided I would get a lot more use from a micro magician than I would out of a mini driver, so even tho I came in third, I paid the difference, and got a micro magician. Oddbot (the guy running the challenge) also threw in a pack of female and male jumper wires. When I get some time, I am going to have some fun with my prizes.

On another note, I recently made a paintball cannon for my friend, 4 in ABS combustion chamber, with SEVEN 1/2 in barrels coming out the front, looks like a minigun, mwhahahahah. Anyway, it is not working REALLY well right now, needs a chamber fan, which I have. I cut down a 120mm computer fan untill it had just a bit of clearence between the inside of the chamber, and the tips of the fan blades, that was kinda finincky, spent a while with a calliper and some side cutters to get that working. Now I just need to stop by radio shack and buy a 12v AA battery pack, and it should be complete. These Pictures were taken when I was using a Piezo sparker taken from an old barbecue laying in the dump, it turned out to be unreliable, so I swaped it with an electroninc continous sparking battery opperated sparker.

I also got to go to Spokane WA. on Sunday and pick up some robot building parts, 4 6in lawn mower wheels. The holes in the middle are a bit big to mount directly on chopped up cordless drills, but that will soon be remedied with some metal bushings I will fabricate on the high school's lathe, a cupple of mid size castors, a few small ball castors and a big hunk of epoxy putty (for making a hemisphere for the HOG drive I will make eventually) rounded out the purchase.I love Harbour Freight Tools :)