Trajectory B/C

[zyzzyva980]

Yeah, I just checked and realized that too. My bad, everyone.

[Draylon Fogg]

OK so why would you waste the time to set up a mechanical release and face the possibility of a screwed up launch when you can pull a string and launch every time???

[zyzzyva980]

That can fail too, you know. Each kind of launch has its merits, as well as drawbacks. One drawback for string-powered launch type that we use is that sometimes it can launch when you don't want it to, and sometimes you want to launch but you aren't able to with moving the machine. You don't have to worry about causing your machine to jump with a mechanical release, such as the battery-powered mentioned above, and if you do, it is normally about the same type of movement each time.

[andrewwski]

I'm a bit confused with your terminology - pulling a string would be a mechanical release, would it not?

[Balsa Man]

Re: trigger reliability and potential for "screwing up":
There is some potential for problems with either an electrical way to activate, or a, let me call it "human-powered" way. There are ways to minimize - and effectively eliminate that potential either way. Key issue is the mechanics of the point/mechanism where there's pressure that's released. With enough pressure and friction, whatever is pulling/pushing to release it can bind, moving the device if its a string being pulled, or not releasing if its electrically driven.

Regardless of design, that points to metal-to-metal at the "friction point"; lower friction than wood-to-metal or wood-to-wood, and essentially no potential for wear to degrade the mecjanics of the trigger.

With pulled string activation, failure modes to control are string breaking (use strong string), knots coming loose (glue after tying), and moving the device (put weight(s) on it, minimize release friction. Control these factors and you have a VERY reliable trigger.

With battery/electrical, failure modes to control are dead battery (use fresh-or freshly re-charged, tested battery), or broken connection (check with LED or meter, firmly soldered connection and wires glued to something on both the device and trigger switch/button after the soldered connection), or switch failure (check just before setting up).

I'd mentioned using a solenoid as a reliable way to electrically move/release a trigger. With the trigger unit our guys are using, the pull strength of the solenoid is many, many times the force needed to move the trigger lever (BIG safety factor). In a rolling block trigger, the friction is very low, and the solenoid works.....every time.
The only other ways to do electrical activation I can think of off hand would be a motor with gears pulling (winding) a string, which could certainly be engineered to high reliability, and an electromagnet holding, then releasing, like a gate-latch (issues = battery drain, magnet heating, and unintentional release if circuit broken = too many ways to go wrong). Anybody figured out any other ways?

[zyzzyva980]

andrewwski, by mechanical release I mean battery-powered, etc. Sorry for the confusion. Balsa Man, for some machines you need an extraordinary amount of weight to negate the effect of the pull on the machine. We use rope instead of string, and that's one way to counter breaking the string. Basically, there's always a chance that something could happen, but some machines are better than others. I'd probably trust Balsa Man before I'd trust me, I haven't really been focusing recently. I need to get myself together before regionals.

[C++]

Are calculators allowed? I think that it is easier to use a calculator to store data than to use about 20 pages of numbers.

[scifipi]

Well, it doesn't say that calculators aren't allowed...

[scifipi]

andrewwski, by mechanical release I mean battery-powered, etc. Sorry for the confusion. Balsa Man, for some machines you need an extraordinary amount of weight to negate the effect of the pull on the machine. We use rope instead of string, and that's one way to counter breaking the string. Basically, there's always a chance that something could happen, but some machines are better than others. I'd probably trust Balsa Man before I'd trust me, I haven't really been focusing recently. I need to get myself together before regionals.

What kind of rope? The thin or the thick kind? At sports stores, sometimes there are very thin but strong climbing ropes that you can use.

[andrewwski]

If you're going to use a calculator, make sure that you impound it as it would qualify under "other materials the team will use" in line 2b.