|What To Do When You Ditch
Your Bike (and
you'd like it back)
A Simple Pulley Retrieval System
by Martin Hackworth
Photos: Martin Hackworth, JR Hackworth, Larry Day
A problem commonly encountered by offroad riders
technical terrain, is recovering a bike that's been launched off a
steep sidehill. With enough riders around, it's possible to simply
muscle even a very heavy bike back up to where it needs to be (though
I've seen it take as many as seven stout individuals to get this done).
For solo riders, however, throwing more than one back at the problem is
not an option. Soloists need to tap into the evolutionary advantages
of brain asymmetry and opposable thumbs to solve the same
problem, sans brute force.
Soloists need to use tools. We are here to help.
What follows is a short, illustrated treatise on how to source, assemble and use a reasonably compact, lightweight and inexpensive pulley system to help you retrieve a dirt bike, by yourself. All of the parts that you'll need may be purchased for around $100. We sourced everything from Cascade Rescue Company and recommend that you do the same. Dana Jordan, the owner, rides. He's a really good guy, and as good of a source for supplies and supplemental information as you'd ever want.
The system we are describing here includes 75' of 1/4" (6mm) prusik cord, a SMC single pulley, a SMC double pulley, a few carabiners, and some 1" tubular webbing (or slings). Because pulley systems that employ a mechanical advantage involve lower forces at most points in the system, smaller, lighter hardware and cordage may be used.
We chose our pulleys for their weight and performance to price ratio. Wherever you go looking, you'll probably want climbing or whitewater rescue pulleys. Stay away from hardware store pulleys that rely on heft for strength.
You don't need expensive cordage for this particular application. You are not trying to rescue yourself from a crevasse, or retrieve a jeep from the Grand Canyon. Levering your bike out of a gully doesn't require really high tensile strength cordage (in the thousands of pounds). Unless you've managed to ride a Harley bagger off a single-track trail, virtually any synthetic braided accessory cord will do. Most 1/4" or 6 mm cord is rated at around 1000 lbs., which is more than sufficient. I generally carry some 1" tubular webbing for use as slings and anchors. Sometimes a hank of webbing is all that you need to wrestle your bike a short distance back up a hill. Don't leave home without it.
Finally, any lightweight climbing carabiners will work just fine. There are even some micro-carabiners out there that are plenty sufficient. Locking carabiners are shown in all of the accompanying photos, but they are not at all necessary for this application.
| Before we begin in earnest,
a caveat. Years
of bitter experience have taught us that there is absolutely no dearth
people hovering around the edges of adrenaline sports
like climbing (some SAR types) and dirt bike riding
(ADVRiders), and on the fringe of science (Wikipedia
editors) who get spun right off their gyroscopes about things like
attachment points, angles, uber-safety, dot products and the
Look-at-me's and wannabe safety wardens are the bane of existence in
our line of work. We kid you not.
There are, for instance, those who will read this piece and howl in derision that our figure-8 knot is not backed up with a half-hitch, that my son is holding the cord with with bare hands, that we used a prusik-minding pulley instead of a double-naught quantum-z model that cranks itself, that we don't use a prusik safety, that we failed to define work as a scalar product, that we used an empty can of race gas as a prop. We feel you. Just like hemorrhoids.
So, before you fire up your monochrome monitor to flame us, you should be aware that the principal author of this piece, a physicist and motorcycle racer (albeit over the hill on item #2), paid for his college tuition with by way of money earned as a climbing guide and author. The odds that you have struggled with as many heavy haul bags on big walls, worked as many mechanical advantage problems out on a blackboard in a classroom full of students, and hauled as many motorcycles up steep sidehills as he, are a bit remote. If you have, you are probably not a wanker, and no doubt understand that good enough for the job is just fine.
The system described here has been employed successfully a number of times on the Tour of Idaho. Success is a powerful innoculant, and that being the case, we care not one bit about your opinion of how neatly our figure-8 knots are tied. What we do think, is that posers and hyperventilators who get wound up about things like this should just hold their breath until they pass out. We are really ornery about being lit up by safety and/or science dorks who don't spend a lot of time riding. I'd give us a very wide berth.
Having said all that, we are always delighted to hear from those who have actually wrestled motorcycles out of creeks and gullys, by themselves. If you have a better idea about how to do this, please let us know. When it comes to recovering a bike, less effort is clearly better than more effort. We are down with any improvement on our modest proposal.
So, down to business. The
first thing that you need to comprehend about the use of pulleys for
recovery is the concept of mechanical
advantage is most easily understood by considering the operation of a
simple lever. A lever amplifies a small applied force by pairing a
small movement with a big force, at one end, with a larger movement
with a smaller force at the other. When you use a long pipe on
end of a lug nut wrench, you don't supply as
much force as you would without the lever, but you end up moving the
end of the lever a greater distance.
Both sides of any system that employs a mechanical advantage do the same amount of work. Work, in physics, is the product of force and distance. Systems that employ a mechanical advantage, such as levers, ramps, screws and hydraulics, trade force for distance.
In order for a pulley system to create a mechanical advantage, it must somehow trade force for distance. Consider the pulley system shown in the first photo, labeled 1:1. All this pulley does is redirect the force applied at the end of the rope. Every foot of rope that is pulled through the pulley moves the load a foot. This rigging produces no mechanical advantage. It may make things biomechanically easier, by allowing one to pull down instead of up, but that's the full extent of any advantage to such a rigging.
Now consider the next photo, labeled 2:1. It looks like the previous rigging, but upside down. The important difference here is that the pulley is attached to the load instead of the fixed anchor. To move the pulley and load up a foot, two feet of rope must pass through the pulley. This produces a 2:1 mechanical advantage. You are moving the load twice as far with half the force. You can balance a load with a force equal to half it's weight in a 2:1 system, and move it with just a little more. This rigging illustrates the greatest mechanical advantage one may achieve with a single pulley and straight pulls.
The next photo, also labeled 2:1, shows how to achieve the same mechanical advantage by pulling down instead of up. Pulling down has a couple of advantages. The first is that you have the option of being closer to the bike, which aids in clearing brush, rocks and other obstacles. The second is that it is biomechanically more efficient to pull down than to pull up. That means less tiring. Less tiring is good.
The next photo, labeled 3:1, shows a system that employs even a greater mechanical advantage. This is the rigging that provides the greatest straightforward mechanical advantage that may be achieved with two single pulleys. The trade off is that you are now moving a lot more rope through the system for each foot the load moves. The greater the mechanical advantage, the more rope that moves through the system to move the load a small distance.
photo, also labeled
3:1, shows a
rigging that achieves the same
3:1 mechanical advantage, but with a down pull instead of up. This
rigging requires that one of the pulleys be a double. This is the
system that we generally use. It's straightforward, easy to understand
and provides a reasonable mechanical advantage without any
rigging. It's a good compromise between force amplification
amount of rope required to move a bike any distance more than a few
The final photo, labeled 4:1, shows the greatest (straightforward, anyway) mechanical advantage that may be achieved with two pulleys. We rarely use this, as the amount of rope required to move the bike more than a few feet, is a lot.
We use the nearest sturdy tree or large rock for the fixed anchor, hopefully right above the trail. The anchor and the load are the two places in the system that experience the full magnitude of the actual forces involved, so the attachment at these points in the system is important. In a pinch, we've used a rock to pound a sharpened tree limb into the ground (it worked). We've even wrapped webbing around a row of bushes for an anchor. Necessity really is the mother of invention. It's all easier than trying to carry a 250 lb motorcycle back up a steep sidehill on your back.
We wrap the free end of the rope around a sturdy stick or shovel handle to help pull. Just make sure that whatever you use is sturdy enough to pull on without breaking. A nice, green tree limb works best.
It is not, in our opinion anyway, not generally necessary to employ a prusik safety for bike recovery. Unless, that is, you plan on winching your motorcycle up an overhanging cliff. In our experience, motorcycles don't really want to move either way from the place they landed after you launched them. You will generally not have to worry too much about the bike slipping back down the hill that you are trying to pull it up while you pause to clear the way, or to rest.
Our final bit of advice is that we cannot possibly recommend highly enough that you obtain some practice with a system like this before you have to deploy it, in earnest, the first time. You will learn a lot the first time that you practice - even on a roadside ditch. Better there and then than way out in the boondocks.
The author, at work.
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