Making the Sliding Barrel
Read up the first few paragraphs of the project for making the handcart, since the comments on engineering are the same, and the sledge uses the 'longer cylindrical' industrial drum referred to, which is the most common variety available. The details of drum suppliers and drum cleaning are also covered in the handcart article. This drum variety has a cap with a maximum 17 inch diameter, and the neck of the drum is about 15.5 inches across. The drum height is 39 inches with cap, or just under one meter. The long drum is used to make the sled as long as possible, the cylindrical form gives maximum strength, and the cap clamp joint is stronger also. A well-fitting cap and clamp are much easier to come across than with the smaller exotic variety used for the handcart. The wheels and supplier are the same as for the handcart, and in my case these hard-working wheels are unbolted from the handcart then bolted to the sledge. Both the sledge and handcart bodies when not in active use double as storage drums for holding the backpack and most of the camping gear. The wheels use a similar 'lucky fit' process to fasten to the sledge as the handcart employs, but again this is a heavier, stronger version.Precision bending, or indeed any bending of 45 mm diameter 3 mm thick aluminium tube cannot be done at home, and I spent some time with the Yellow Pages before finding the right people to do the job. This is a speciality of small companies who tailor-make bull-bars for large 4WDs and trucks to fend off kangaroos, moose, hikers etc. They normally carry stocks of the right tubing for their own use, and can also weld the 'feet' of the sledge where the runners clip on. Make sure you have located a good drum supplier, and the right tube bender before proceeding. Many tube benders from other fields wanted to do the work, but they had no idea on tubing, and the price was about ten times as high.
With your drum source and bender located, I suggest you get the runners made. Bends to this precision were only just possible using the gear my bender had, and if you look closely at the runners on my sledge, there are slight differences between the two which fortunately do not show up on the snow. There are three bends, and all are in the same plane so the runner remains straight from front to back when mounted on the sledge.
Runner bends
Allow extra length on each end of the runner, and hacksaw off the surplus later, when you have established the best match between the runners. The dimensions (without surplus) are:-
Straight tubing run beneath the sledge 1300 millimetres or 51 inches.
Tubing bends upwards just ahead of front sledge foot six and a half degrees to form the first bend.
Distance from first bend to second bend 8.5 inches or 215 millimetres.
Tubing bends upwards another six and a half degrees to form the second bend.
Distance from second bend to front bend 19.5 inches or 500 millimetres.
Tubing bends upwards another thirty five degrees to form the front bend.
Distance from the front bend to the front end of the runner is 7.5 inches or 190 millimetres.
The final front 'kick' and length is not critical, but this 35 degree angle rides over deep snow and fallen trees, as well as making comfortable handles when the sledge is running on wheels.
My bumper-bar maker was kind enough to let me be present at the bending. Gather up your pair of runners and head home, taking with you any offcuts from the process, which you will need to make the curved feet. Trim the runners down to the right length. You can hacksaw this size tube at a neat right angle by taping a piece of A4 paper round the tube so the edges meet correctly, aligning the edge of the paper with the location you want to cut, and carefully following this right-angle edge with the hacksaw. You cannot do it well enough by 'eye', or at least I can't.
It is time to jump to the first easy job, which is the front plywood rectangle, which is permanently screwed to the bottom of the drum, which ends up on the front of the sledge. I used rough half inch thick exterior grade ply, which was further waterproofed when the job was over with a few coats of varnish. I had some staining varnish handy hence the rich mahogany colour.
The ply is 360 millimetres or 14.15 inches high. This is the same size as the bottom width of the blue drum. Your drum should be the same but you can alter the dimension if it is not. All my blue cylindrical drums taper like this at the base. If yours does not, you are going to push snow!
The support legs are made from 40 millimetre square aluminium extrusion with a thickness of 3 millimetres. They are secured to the ply with three big setscrews per side, the heads of the setscrews being recessed inside the legs. Big washers and wingnuts are used to tighten the setscrews. These do not loosen in sevice, but the wingnuts are provided so the legs can be removed if materials to improvise are needed in dire circumstances. The support leg is flush with the top of the ply, and extends 80 millimetres below it, measured before the curve is filed in the bottom of the leg to take the concave support foot. Longer leg extensions improve low density snow towing, but raise the centre of gravity. The present height is optimum for Australian snow.
You should see something rather like this inside the drum.
The other plywood end fits on the cap, and is more complex. The handcart uses a similar plywood base, and securing it to the handcart cap is done in the same way with hidden aluminium spacer pieces. Read up the relevant section of the handcart for more on the technique.
The two support legs are mounted to the ply using setscrews, washers and wingnuts just like the front pair. Measured the same way as the front, the support legs extend 43 millimetres below the lower edge of the ply. If you have lengthened the front support legs, remember to do the same for the back ones. Unless you are doing away with the wheels, the support leg tops are not flush with the ply edge, but protrude 45 millimetres beyond it.
Make the aluminium spacer pieces as per handcart, but with a larger diameter for the bigger cap. Perform the near-impossible drilling job before screwing the spacers to the ply rectangle, and the cap to the spacers. You can use a few less screws than the photo shows. Varnish the front and back ply rectangles before assembly if you are feeling confident.
You should now have the drum with the front ply panel mounted, and the correct length front legs mounted on the panel. The back panel is securely mounted to the cap, and the back legs of the right length and tested with the wheels are mounted on the back panel. Confirm with the aid of the cap clamp that there has been no cap distortion due to bad assembly, and that the cap still drops onto the drum perfectly and the clamp ring holds it rigidly and hermetically in place without excessive effort to close the clamp handle. The exacting work is over.
Loosen the cap clamp, and rotate the cap until you can sight along from a back leg, and see a front leg precisely parallel to it. Each time you reassemble the sledge in the snow, you will be doing this. Note when you tighten the clamp ring the parallel is undisturbed. Both the front and back 'foot' ends should be on the same side of the drum! If you now stand the proto-sledge on its four feet on a flat floor, all four feet should be in contact with the floor. Mine were, first time. If they are not, check your dimensions, the cap alignment, and the flatness of the floor. Like the Software manuals, we will assume success.
Take your offcuts of runner tube, and cut 80 millimetre lengths of tube, before halving each 80 mm length to make two 80 mm half-tubes. Bash or squeeze these half-tubes in the vice until the curvature has opened up enough so they fit nicely over the original runner tube. If these concave sections are significantly wider than your support legs, hacksaw them to fit, leaving the 80 mm length undisturbed. You can now use a coping saw and/or a coarse half-round file to cut corresponding concavities in the ends of the four support legs. You will need to fine-down the support leg walls parallel to the feet to make a good fit. Once the feet fit nicely onto the legs, carry the whole caboodle, drum, runners, the lot back to your bender/welder who knows all about flat floors. Assemble the sledge so it rests on all four feet on the concave sections which in turn rest on the straight part of the runners. Your welder can then tack the feet on the bottom of the legs in just the right position before carrying the legs away to his vice to finish the weld.
Clean up the welds, round the sharp corners of the feet and buy some stainless hose clips. Some modern types have the edges of the steel band turned up so they cut less into rubber hoses. Unscrew the clips so the band lies flat on a steel surface and beat the edges flat with a hammer, which only takes a few minutes. I even bother to use a sharp file and taper the edges the other way to cut down on snow resistance. The runners can now be dropped on to the body. You will find support feet in the air is much easier. The runner tips are set vertical by 'eye', the clips are tightened with gross excess length cut off if need be, and suddenly you have a sledge.
Drill an eight millimetre hole just back from the top tip of the front of each runner, and smooth it well both inside and out. Quarter inch or 6.5 millimetre nylon braid will do for towing, and details of use are in the other sledge section.