Derby Talk

You can get wall-wart style power supplies at Radio Shack that'll source more than 200mA easily. I got one a while back for a piece of hardware that needed 12V at 800mA. No problem.

It'll mean a requirement for 110VAC, but it won't run low in the middle of a competition, either.

Tom

A while back you could get one of those high precision analytical balances pretty cheaply. Mettler is one of the better manufacturers. I think they merged with Toledo a while ago, so if you run across a Toledo-Mettler, that's the same folks. I used to build indoor duration flyers, though I was never...

This is also similar to the clock arbor and pivot. Clock gears (wheels) ride on arbors that usually have a highly cylindrical axle fitting into a bell-mouthed hole. That is the hole is drilled, then reamed from each end with a tapered reamer. This leaves a very small contact area, and nice geometry ...

I'd be curious to read what the surface preparation requirements are from a graphite/moly manufacturer. Every time I've had a friction/lubrication problem at work, I've had great luck calling the manufacturer. I'd be willing to bet there's something in their datasheet for a plastic/steel interface. ...

Interesting!! I hadn't actually run the numbers, so that was good to see. Thanks! For what it's worth, getting a coefficient of drag significantly under 1.0 is a tough challenge. A well-designed subsonic rocket can often get down in the mid-0.8 range. The act of adding fins typically bumps the coeff...

That makes sense. Ok, this is going to sound like a goofy question, but bear with me: On a sailing ship, getting your hull smooth is a big concern. But when you get to the actual surface finish, mirror smooth is too smooth. It actually increases drag. A 600 grit wet/dry paper, used wet, with the str...

Kinda what I was wondering. You need pretty significant speeds to make aerodynamics a big factor in air. PWD, this is probably old-hat, but it might be useful for track testing: A few years ago a fellow by the name of Dean Wheeler wrote up a neat article for using a normal video camera for getting l...

Pinewood Daddy's observations on steel are well worth reading. You could likely use something like Kasenit to get a good case hardening on an axle, but it'd be a heckuvalot of effort. A nickel plate would be a lot easier to do. More important, almost any hardening process is going to give the steel ...

What kind of data would you want out of a wind tunnel? The place I went to high school had a wind tunnel. It was a pretty straightforward affair, and wouldn't be too hard to build. I think it was mostly PVC and air duct construction with a squirrel cage blower to move the air. Airspeed was regulated...

I'd also be interested in your Solidworks drawing of the stock BSA wheel, if that's ok.

Thanks,

Twitch