[ChrisH]

While I defer to Al on matters electrical, I disagree with those posters who said "forget the analysis". Analysis is a tool. Like any other tool you need to figure out where and when to use it. That's the tricky part.

The first year we built a lift, I did a fair amount of analysis to ensure it wouldn't break. The next year, when we had to hang a robot from the bar I did more. The year after that I said "what we did last year worked and the loads are much lower this year" so I did no analysis but used the same sized elements. I chose, based on experience, not to use a tool that had been successful in the past because there was no need for it.

This year we will probably be radically changing our lift concept and the new concept will be more weight critical. That is weight in the wrong spot will have a greater adverse effect. So I will be analyzing our lift not to ensure that it doesn't break, but to ensure there is no excess weight. Though if I have to choose between weight and break I'll take weight anyday.

Engineering is an exercise in continuing judgement calls. You are constantly faced with "What's the best way to do this?".

If your problem is to figure out how to make a robot go fast, you could buy alot of gears, shafts and wheels, put them together and measure the resulting speed.

Or you could sit down and say "My motor has these characteristics, what gear ratio range will give me acceptable operation?" Figure that out and you have greatly reduced the number of combinations to try out. You might even save time doing it that way.

Like any other tool, using analysis requires time and thought. It is all a matter of balancing resources vs requirements. How long it will take to do the analysis and what effect it will have on the overall design are things you need to weigh. Don't spend days figuring out whether to use a 3/16 or 1/4 inch bolt, but it might be worth a few minutes to figure out whether or not 1x1 aluminum tube will support a 5 lb box cantilivered 5' out.