well yes, but i can see the city getting a *lot* more excited about harness climbing a tree to put up a line than a short ladder and a span set.

it's also a lot more of a PITA to clear if something jams at oh, say 20' up in the air and we have to strike the thing to clear it.

keeping the max height at say 20' means that a decent extension ladder can clear it, and it can start a foot off the ground.

i'd say we have 4 power categories; mechanical, electrical, internal combustion and external combustion.

so you dont' have the steam going head to head with the rubber band, but you could have an overall winner on top of the category.

we should have a weight categories, i.e. light, medium and heavy. say under 8 oz, 8-24 oz, 24-5lbs.

+1

overall efficiency per category and overall style too maybe?

say we do consumed fuel to weight to speed ratio (so something that's all fuel and consumes itself is less efficient than something that's heavy but uses the same amount of fuel...

Four power categories and 3 weight categories is 12 categories. Do we think there is going to be enough interest to have an actual competition in all of them (ie, more than one entry per category)? Might it be better to pick 3 or 4 combinations of power and weight to concentrate the entrants efforts and have a better field of entries in each power+weight combination?

I'd definitely enter at least 2 categories depending on how much time I had to build them

I thought I would give this a bump and make a suggestion.

Perhaps it would be fun if I just did a non competitive rocket based demo for this.

Is there a weight handicap of some sort, otherwise I could probably just do something with little 1/8A MicroMaxx (6mm Dia x 26mm Len) motors designed to direct exhaust away from the wire.

That would be great! AFAIK we haven't considered a weight handicap, but obviously the vehicle ought not to put so much stress on our wire that the wire apparatus gets deformed for other participants.

I'm looking forward to seeing a demo at our potluck!

[EDIT: OH! Remember, we had considered a requirement that the race vehicles would have to turn around and come back after reaching the end of the wire. Maybe you can work on a way to achieve that as well.]

2 directions would be a fun challenge, I'm not sure if I can get my shite together by the 1st.

I've been in a general slump lately.

Will entries be able to use a guide that fully surrounds the zipline (i.e. a tube)? It would require access to the end of the cable to thread it on, so based on that it seems like it might not be an option.

Yes, you could use a guide that fully surrounds the zipline, as long as it would not leave a residue on the line, such as grease or oil. The end of the line, I suppose, would be a post or tree and the line would not double back to provide a continuous path. So the vehicle would have to somehow sense the end of the line by contact or other means and swivel or reverse propel itself from there.