Saturday, February 28, 2004

Project Update 02-28-04

Last update I mentioned the little electronic BB gun that I got. I took the gun apart, figured out how it worked and then decided on a way for my SV203 board to fire it directly and bypass the trigger.

Here is an image of the gun itself.


I took it apart and here is what it looks like on the inside.


Basically, the trigger pushed an on/off switch for the little motor that was geared way down. The final gear had only about 80% of its teeth. It pulled back a piston of sort. Just as the piston got to its rear position a BB falls into the chamber and the gear runs out of teeth and allows the piston to fly forward and spit the BB out.
All I have to do is bypass the trigger and connect directly to the motor itself with power. The SV203 can act as an on/off switch but it wont push enough amps to make the motor turn. I plugged it directly into my 800milliamp power supply with no luck. Next I tried the 5V contacts on a PC power supply and that worked like a charm. So I'll have to hook up some kind of power transistor to allow the SV203 to turn on the high power needed from another source.

The whole firing mech is a bit more than I thought it would be and I cant rip it out and still have it work unless I make my own housing. The current housing is going to be a pain to mount to some kind of servo aiming system.

More Chassis Planning

Ever since I got the wheels and understood a little better about how I would mount the axles etc. Before I was unsure exactly what parts would all go well together etc. Finally, after seeing the wheels I decided on having a live axle. That is, the axle would not sit still with the tire spinning around it, it would actually drive the wheel.
The Motor spins the sprocket, the sprocket drive the chain, the chain spins the sprocket on the axle the axle spins the hub with the tire on it...

I found some pillow blocks and flange bearings that I liked at the roboto marketplace and I modeled them in 3DS Max and added them to my current chassis models.


Here is my first chassis design and my current favorite with the new bearing mounts modeled.


I've pretty much decided that the center motor design is going to be the one I go with. I also wanted to see if I could get the width of the vehile down by offsetting the motors so that they could overlap in the center. I made the following design. Its pretty drastic but it shows how the idea would work. I'm not really sure how big/small I need the whole thing to be but this 3D model is probably smaller than it will have to be in real life. Hopefully soon I will be able to make a final decision on the dimensions and then I'll just make sure I can fit everything in. There has to be room for batteries and the computer, and whatever goodies I need



If you have any suggestions or advice now is the time to give it. I'm pretty much set on the above design, all thats left is the actual distances between the tires and motors etc.

Wednesday, February 25, 2004

Project Update 02-25-04

I got this little guy in the mail this week. It was only $33 bucks after a carton of 2000 BB's and shipping. The gun itself was only $12 or so. I picked it up from http://www.airsoftatlanta.com/electric.htm.
I was going to rig it up to my servo playground but ummm it shoots really hard and fast and I'm afraid someone will shoot my eye out and make a mess of my office. We shall see though.










I got these this weekend off of an old go cart that my dad had gotten for me and my friends and his grandkids a long time ago.
They are 14-15 inch or so, a little bigger than what I was originally looking for but they will do fine for my robot. I was really pleased when I saw them because I was afraid that the tires would be two sizes, smaller in the front and larger in the back. All together these things will probably save me about $120 in new tires and rims etc. I may have to replace some of the tubes though and they are rusted up pretty bad. Also, the hubs are not made for a live axle as my current design will use. So I'll have to replace them or modify them. I may just make my own.
The go-cart was driven by a single chain and the tire that it was attached to was pretty bald compared to the others, I may replace it later but its not so bad that it wont work at all.





Here are some sprockets I picked up as well to fit on my motors.
I showed my brother, Lee, my two current ideas for the chassis etc. He suggested I go with the version with the motors in the center of the two side wheels instead of directly connected to one of the wheels. This would allow us to gear up/down the system. I decided on #35 chain and got some advice on how to mount the axles etc.
Armed with this new info I made a few new designs and modified my old ones etc.
I'll get into that with the next update as well as some modifications I made to the little BB gun.