Hauling Ass

Last updated: Fri, 28 Mar 2008 15:16:00 GMT

Now with rope!

As I was nursing my bike back home after the excitement of a couple of weeks ago, I was wondering to myself what I could do to help myself next time. Four-wheel-drivers often carrying winches, I figured, but was there some sort of lightweight alternative that I could rig up to haul my bike out of trouble?

Climbers have to do this sort of thing -- man-hauling loads, lifting themselves or fellow climbers -- and they don't want to be carrying too much weight to do the job, either. I did a little research, asked a few folk, and was pointed at the Z-pulley. Most implementations of the Z-pulley seem to use at least one ascender and at least one pulley. Both are fairly specialist bits of kit, and the only cheap ones I've seen weren't worth carrying. Finally, a friend of a friend pointed me to an implementation of 3:1 Z-pulley using just four carabiners.

I scoured TradeMe for a week, (New Zealand doesn't heart eBay,) and finally scored 50m of fuzzy 9mm dynamic rope and 12 carabiners for $100. I'm hoping to sell six or eight of the carabiners on for half of that, so this should come out at a cost of $50.

Only the ends of the rope were fuzzy, the middle section was in good condition, so I cut the rope. Tightly tape the point you're going to cut, make the cut with a very hot knife for a reasonably neat finish. I was left with two 12 metre lengths of fuzzy rope and a 26 metre length in good nick. Three metres from one end, make small loop with an alpine butterfly. The loop only needs to be big enough to slip onto a carabiner. At the end, tie a bowline, secured with a stopper knot. Again, the loop only needs to be big enough to slip over a carabiner. Slip them both over one carabiner. Now repeat at the other end. Let's call these the "first" carabiners, one end will be the "anchor" end, the other the "load" end. The loops we've isolated with these knots can be thrown around the bike's forks or grab-handles, or a tree, a rock, whatever. Wrap the whole loop around and clip it back into the first carabiner. For now, we'll just clip the "second" carabiners into each first carbiner. That's your kit.

To test, I took my bike into the garden and laid it on the ground. I can barely move it by hand. I wrapped the rope-loop -- we'll call this the load end -- around the forks, between the triple-clamps. keeping the rope tight, run it back to the anchor end and clip the rope through the first carabiner. Now run the rope back to the load end and slip the rope through the second carabiner at the load end. Still keeping the rope tight, run it back and clip it through the second carabiner and the anchor end. This is a Z-pulley. Now pull, and revel in the victory of brain over brawn.

Well, that's the theory. Not so good in practice. If I were using static rope and real pulleys, this would probably work a treat. I'd be able to walk back to the bike and stand next to it as I haul it, with a 3:1 leverage. Unfortunately, the spring in 20-odd metres of dynamic rope combined with the friction of three 180 degree turns around the carabiners means that I'm losing all of that 3:1 advantage. It's no easier to move than hauling on a single rope.

So, a modification is in order. If I move around and pull at 90 degrees to the the direction of travel, the reduced friction on the second anchor carabiner is enough that hauling is noticeably easier. But still not easy. I unclipped the rope from the second anchor carabiner, effectively changing the system to a 2:1 pulley. I had to stand in front of the bike, facing it, but pulling from that angle helped reduce friction on the second load pulley, too. I'd reduced the pulley system's friction by 33% overall and reduced the spring in the rope by almost the same. Pulling from here is significantly easier. Much easier than pulling the bike unassisted.

I'm going to keep my eyes open for static rope, and for second-hand pulleys. I think both might make the 3:1 system feasible. But, even without that, the 2:1 system make a big difference. It's a little bulky, at least 2l in volume, and weighs in at 1.6kg, but there's plenty of room in my backpack. Hauling the bike with this system is much, much easier than without. Not so easy that my kid could do it, but easy enough that I'll suffer that 1.6kg load "just in case."

So, now I get to feel like a paranoid freak again!