Monday, May 31, 2010

Pulk v4.0

I'm adding this as an update. I think that I'm going to use a shock cord lashing system to secure the load into my pulk. It took nearly 35 feet of shock cord to "lace up" my pulk and the way I secured the ends was to use a super sized cord lock. Now the cord locks that are available for purchase are way too small! The 3/32" shock cord would never fit so I decided to make my own. I cut a one inch piece of pvc pipe to 4 inches. I then sanded down a wooden dowel to just fit in side the pipe. A 3/8 inch hole was drilled in through both. A very stiff 2" spring was sent down the pipe from the end that didn't have the dowel sticking out. To cap off the end I used a 1/2inch piece of pvc pipe. It just happens to fit very snug inside the 1 inch pipe. This plug was driven in with a mallet until the desired tension was reached. Now I am able to pull the shock cord tight and secure it with the cord lock.

Super sized cord lock

This may seem like a strange time of year to be thinking about winter pursuits but my studies have me too busy to even day dream about grand adventures let alone work on equipment. This past weekend I completed another pulk. This is the fourth version that I've made, the first was made of a 3 foot toboggan. It had molded in runners which was nice for anyone that was skiing behind me because the runners were spaced far enough apart to set a fairly decent track. The problem with it was that it was too small and I had to wear a 30 L backpack in order to bring enough gear. My second version was a 5 foot toboggan which proved to be wide enough to keep from tipping over but still not enough space. The third version was the same 5 foot sled with another attached to the top which opened like a clam shell. I had just enough room to fit gear and food for a weekend trip but anything longer than a couple of nights and I wouldn't have space and would have to resort to using a backpack again. All four pulks use a ridged pole system that is made of metal electrical conduit with swiveling brackets at the pulk end and a clasp that attached to my harness. My goal is to eventually go on extended winter camping trips that are two or three weeks in length. A friend and fellow winter camper, Bryan Saurer, even suggested a fly in trip. In order to bring enough gear for an extended trip I will need a bigger pulk which is why I build a fourth. This one measures 16" X 8' and has a 7" up-turn on the front end and weighs 21 lbs (which is more than I'd like but the supper slippery sliding surface will make up for it, at least that's what I tell myself). The sliding surface is a piece of UHMW polyethylene plastic, 1/4" thick. This material is nearly friction free on snow. In February, on a snowshoe trip to Nistowiak Falls, Bryan and I traded pulks for a while, I pulled his 10' sled which was loaded with 140 lbs of gear and he pulled my 5 foot pulk loaded with only 50 lbs. Bryan's pulled better, even with nearly three times as much weight! I was convinced at that point that I had to build a new a better pulk of my own.

The frame pieces laid out on the shop floor

Showing the rise in the front end, frame weighs 6 lbs

UHMW polyethylene plastic before being cut to length

UHMW clamped and ready to be screwed in place

Caster bracket for an attachment point for the poles

My snow shovel. Emergency ropes extend from holes in the top board in case the poles fail.

5 comments:

Pawistik said...

Hi Mark,
If I were you, I'd change the way the rope zig zags through the sled running through those smallish holes (as shown in the last photo). How would feeding an ice-encrusted rope through the holes at -35°C with mitts on work? Instead, I would use eye bolts or loops of rope (preferred) permanently attached to the rails. They would be something much larger to thread a rope through, and can accommodate multiple ropes if and when necessary. I'd also make sure I have lots of tie-down options so that I can add a rope in just the right spot to stabilize a shifting load. Likely this is less important with your rigid pulk than my flexible snake-like toboggan.

One note though: do a better job of tying those rope loops than I did on mine. Some of my figure eight knots worked loose on the Nistowiak trip. I need to figure out the proper knot to use for that situation (my ropework is not up to snuff).

Cheers,
Bryan

Wildpaddler said...

I do intend on doing something different with the tie-down system. The zig-zag line is actually a 1/4" shock cord. I just laced it up quickly for the photo. At any rate I am considering adding the little loops of rope and getting more shock cord so they criss-cross along the entire length of the sled. Using shock cord will save me from the exact situation that you describe with the ice encrusted, -35 rope. The shock cord will allow me to stretch it in any direction needed in order to get the load in place but I do agree that more tie down locations would be better. There are many small modification that I will likely make on a continual basis.

Mark

Pawistik said...

I guess I should hurry up with those pulk poles, eh? The snow could be falling at any minute. I'll be doing some running around tomorrow (I wanted to head to Lee Valley anyway) so will go to Peavey Mart & pick up a couple of fibreglass poles.

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