Monday, November 14, 2011

Screenshot Assault

So I've been working on two designs simultaneously. I'm trying to finalize both of them so that I can then decide which one to actually follow through with bringing to life, since I'm too poor to do both right now. I have two options: improve an existing design, or do something no one has ever done before (I think).

Option #1:

New suction carrrr!

You may notice that for the time being, I've named it Parkour, because I can't think of anything else and Parkour is a lot better than "suction...vehicle...thing". If anyone thinks of any better names then there's a comments section. Anyways, here's a better idea of what Parkour looks like:

Ohhhh yeah, going for two fans this time. It's still going to be powered by Pololu's micro metal gearmotors, since they've proven they're worth their weight in gold, and will grip everything via Pololu's awesome wheel/tire sets.

So this thing is very very wide because when a vehicle is turning like a tank, it simply performs better the wider it is relative to it's length. As far as the huge 90mm tires are concerned...well, this screenshot says it all.

Parkour is designed to be able to go around the outside edge of corners. The huge tires and substantial ground clearance will also aid it in conquering just about everything else too, of course, from deep grooves in the sides of buildings to interior 90 degree transitions, which suction car v1.0 needed a couple extra angles to conquer.

Besides opening the doors to pretty much any terrain, I'm also working to improve upon all of the other minor little issues with suction car v1.0 that bugged me. To start off, Parkour operates off of one battery.

One. Battery.

Instead of, you know, three. I plan to use one of these. This will give me the same 4S power and twice the capacity, which will be awesome since I'm shooting for at least a 10 minute run-time this time around. Further improvements include actually having enough chassis space for all of the components, and using hacked servo boards to control the drive motors, instead of shitty R/C airplane controllers that decide to stop working sometimes, and won't reverse. So now, besides being able to reverse out of bad situations, I'll be able to actually turn in place, with the outside tires moving forward and the inside tires moving backward, instead of just having the outside tires moving forward and the inside tires doing nothing. Maneuverability was always a bit of an issue with SCv1.0.

Oh, everyone stop for a second and look at how much effort I put into modeling the Pololu 90mm tires/wheels for this project. I don't know how many grooves there are around the real tires, but mine have 210 little grooves all the way around. I feel like a god, knowing my creation so well.


Option #2:

Yes, it's a gun. No, it's not designed to kill people.

...and yes, I have contemplated mounting it on Parkour and calling it one project.

It's basically a baseball pitching machine, except scaled way down and designed to shoot elongated projectiles through a barrel, hopefully at a much higher speed and accuracy. I've actually been toying with this idea for a very very long, years.

Everything's pretty compact in this design and therefore hard to see but I'll try to explain as best I can.

The projectiles are going to be made out of something cheap, readily available, easy to work with, and 1/4" in diameter. Sounds like wooden dowels to me. Here's a screenshot showing the loading device. There's just a tall gravity-fed ammo rack that holds the wooden dowel segments, and at the bottom a servo will work an arm (not in the drawing...yet) that pushes the lowest dowel into the giant spinning wheel which then propels it to deadly high speeds out of the barrel.

Maybe that's a better view. Here you can also see the second standard size servo I have mounted underneath the entire assembly, which will be used for the tilting portion of the pan/tilt mount that I want this gun to be mounted upon.

The reason the projectiles are going to be so long (two inches, actually) is pretty simple. The giant rubber tire that will be propelling them is going to be spinning at somewhere around 40,000rpm as fast as I can get it to go, and no matter how grippy the silicone tire is, it's going to slip. Also, no matter how powerful the motor driving the tire is, it will bog down when it suddenly comes in contact with a projectile that is stationary (being reasonable here...if I drive the wheel with a turbocharged V8 engine, it's pretty safe to say that there will be no bogging, I know). The longer the projectile is, the more time the giant rubber wheel will have time to get a grip on it and accelerate it to an even higher speed. It's kind of the same idea as having a longer barrel on a real gun to allow the explosion going off behind the bullet more time to accelerate that bullet.

That being said, the barrel on this thing actually needs to be the opposite of a real gun...very short; just long enough to make sure the projectile is moving straight. After the wheel is no longer accelerating the dowel segment, the only thing that projectile is doing is slowing down, and will do so at a higher rate if it's traveling through a barrel with friction.

So why'd I only go with one tire to accelerate the projectiles, and not two? Well...I didn't find it necessary for one, since the projectiles are elongated and won't start spinning like a ball would if spun by a single giant tire. Baseball pitching machines need two wheels to be any good because they're pitching...balls. Also I went with one tire for the sake of being compact.

Oh yeah:

On the other side of the giant wheel are ball bearings, so that eliminates the huge amount of friction that would have been present if the projectile was being pressed against the other side of the barrel as the drive-wheel propels it.

I guess that's pretty much it for the wheel gun. When I first began designing it, I had a second drive motor at the end of the barrel that was angled ever so slightly, to put a spin on the projectile, but that turned out to be too much of a pain in the ass. Also, right now it's semi-automatic. I really want it to be fully automatic because that would be awesome but I'm still working on figuring out the best way to make that dream come true.

So...both are still only about 90% finished, but...Parkour, or wheel gun? I can't decide.


  1. I think the gun would be a "better" project but parkour is a "cooler" project. A problem that will probably occur with the gun is that since your projectiles have a uniform density throughout their length, they will tumble when they leave the barrel, regardless of how long the barrel is... I have found two solutions to this. The first one you touched on with the slightly angled wheel to give a "rifle" effect but since that wheel will only be in contact for a short amount of time, you will get a wobble effect when the projectile leaves the barrel. It wont tumble as easily but it will most likely revolve a round an axis "closer" to straight. The second and and in my research much easier and more effective solution is to add a dense "tip" to your projectiles. Like an arrow. Even just a small wood screw in the tip of the dowel projectiles will greatly improve flight patterns.

  2. Yeah I actually considered weighting the tips of the projectiles. The only problem with that is that I just want them to be very...disposable. I want to be able to shoot as many off as I want and not care at all.

  3. Maybe some sort of little mold can be made and a small amount of lead could be melted into the tips relatively easily.

  4. I will cast one vote for CornerShot Parkour.

  5. Nice information dear. Thanks for sharing it. Jarvis Caster & Rubber Wheel