Chariot sells a cross country ski kit for their bicycle trailers. They're spendy - around $200. I decided to make my own. The kit you buy consists of two skis, their mounts and a harness to pull the rig. I decided to pretty much copy the commercially available unit.
A pair of skis
2' pvc pipe
foam floor padding thingy
1' wide nylon strap
nylon strap buckles
I don't exactly remember what all I used.
Skis: I found the skis I used at REI on closeout, clearance,we've got a bunch of these and NEED to get rid of them for a low, low price of $17. They are simply a pair of child's cross country skis. I think they are 110cm long. Had I not stumbled on that incredible deal, I'd have visited thrift stores, watched garbage piles and/or made my own from pvc maybe?
2' pvc pipe: Environmentalists relax, yes I know pvc is bad stuff. I found a piece of it in the rafters of my garage. It must have been leftover from a project performed by the previous owner.
electrical conduit: I bought mine at Home Depot. No real mystery here.
foam floor padding thingy: This was one of those puzzle piece square foam play mat things. I used a scrap I'd kept after cutting it to fit the floor in my basement so my little one would have something softer than concrete on which to play. Approximately 1/2 of a 2' x 2' square, so 1' x 2' was perfect.
old seatbelt: When I was in college I worked in a shop maintaining the college's fleet of vehicles. At some point we had a big 15 passenger van with only the front two seats. Strangely whoever removed the seats left the seat belts. We removed the seat belts and the guy in charge threw them in the trash. At the time, I didn't know what I'd use them for, but I knew I'd think of something eventually. I saved them. Now 10 years later, I've finally thought of something to use one of them.
nylon strap: More stuff I had on hand. Most of it came from an old mounts on the back of your car bike rack. I think one piece was something I picked up on the street and the final two were from a backpack maybe?
strap buckles: Surprisingly I had these on hand too. Maybe from that backpack or ???
Step 1: The Ski Plan
First thing to figure out was how to attach the skis to the trailer. The commercially available kit has two triangle shaped things attached to the skis and then an axle that plugs in where the wheels' axles are. I thought about doing similar, except the axles have a nice push button quick release feature. I didn't have any extra axles lying around. I decided what I'd do was build a 'socket' into which the existing wheel would fit. I liked this idea as it made the skis more compact for transport and storage. It also means that I can roll the trailer across parking lots, roads, sidewalks or other snow free spots. Simply remove the skis from the wheels, roll across the road, pop the skis back on and away we go!
Step 2: Implementing the Ski Plan
I made the wheel 'sockets' out of the 2" pvc pipe. I wanted to contour them into a \___/ shape so the tire would sit down inside it a little bit and not want to roll out. I decided to make a couple of bends in my pipe to achieve that shape. A little research here (instructables) and elsewhere taught me how. Most suggestions said to fill the pipe with sand and cap the ends. I didn't have any sand or caps. I did have duct tape and oil-dry (unused). I placed several layers of duct tape on one end, filled the pipe with oil-dry. I then tapped the pipe to get the oil-dry to settle. After I was satisfied that more tapping would not make more room for more oil-dry, I taped off the other end of the pipe.
Now I needed a jig to bend the pipe around. I happened to have some 3/4" plywood scraps and some scraps of 2X4. I screwed the 2X4 pieces to the plywood in what looked to be about the right arrangement.
Ready to bend! I used a heat gun (think turbocharged hair dryer) to heat the pipe where I wanted a bend. I heated it until I thought it would bend easily, making sure to rotate and heat evenly. I'm impatient. I probably should have heated it a bit more as the inside of the bends kinked when I put it in the jig. No big deal as those areas are going bye-bye anyway. So, lather, rinse, repeat until I've got two \___/ shapes out of pvc pipe.
Now to open those up so the wheel will nest in them. I used a hack saw to split the pipe along what was previously the length. My hacksaw has this nice feature where you can put the blade tilted 45 degrees relative to the frame. Saw, saw, saw. Done! now I just need to attach them to the skis.
Step 3: Attach Sockets to Skis
I agonized a bit about how I wanted to do this. Glue? Epoxy? In the end I settled on a couple of large (I think they are #14) screws per ski. I decided on this option over epoxy as in a few short years I hope that my kid will be skiing on his own rather than me pulling him. Hopefully at that time, I can remove the sockets from the skis, replace them with bindings and buy him a set of boots. The screws have to be SHORT so as not to go all the way through the ski. I think I ground the very tip off of mine just to make sure. I pre-drilled the holes for the screws and screwed the sockets on.
Now things are really taking shape. To attach the wheels to the ski sockets, I decided on a couple of small bungee cords per ski. I may decide this isn't firm enough later, but for now it seems to work well.
Step 4: Take a Summer Break!
At about this point in the project, the long Minnesota winter broke, the snow melted and spring arrived. As I no longer had a use for this project, it disappeared into the bowels of my garage. I've been enjoying my summer - using the bike trailer as a bike trailer and stroller a lot. As it is now September, I'm starting to see that the snow will fly again much sooner than the summer lovers would like. So time to finish up this project while the temperature in my garage is still above freezing!
Step 5: Back to Work
So I finished the ski portion of the project last winter/spring. Now I need a way to tow the rig. The commercially available kit connects via what appears similar to a backpacking hip belt and two long anodized aluminum tubes. Once again, I decided I could do something similar.
I found that 1" EMT conduit fit the sockets in the trailer quite nicely.
I bent two pieces of conduit into shape ( a right and a left) and connected them together in the middle. The connection would be right behind the skier. To connect them, I took a 3 inch scrap of tubing and split it open lengthwise. I then rolled it tighter using pliers until it would just fit inside the conduit. I stuck it in one piece about half way and then into the other piece. I then secured each half with two sheet metal screws each.
To keep the tubes in the trailer, I drilled some slightly oversize 1/4 holes through the tube. The sockets on the trailer already had 1/4 inch holes. A couple of pins down through the holes completes the connection.
Now all I need is a hip belt.
Step 6: The Hip Belt
I probably could have found an old backpack hip belt, but I decided to make one. I had an old seatbelt for the belt part. I had a piece of foam play mat for padding.
The piece of padding was about 12 inches wide and 24 inches long. I needed a piece about half as wide and twice as long. Using an electric carving knife I split the foam into two 6 inch by 24 inch pieces. Incidentally, this is the only time I've ever seen that electric carving knife used. It is probably as old as I am. I got it from my mother. I don't recall ever seeing her use it. It worked beautifully. Next, I scarfed the two pieces together. I used the carving knife to taper each piece and glued them together using Weldwood contact cement. It is stinky stuff, use it outside. I now have the 6 x 40 piece of foam I need. "Wait" you say, "I thought the short pieces were 6 x 24, shouldn't you have a 6 x 48 piece?" No, the scarf joint eats up some of the length.
Ok, now how to attach the seatbelt to the foam so the padding stays under the belt? I decided to cut some slots in the foam and I'd insert the 1" wide nylon strap through the slots and buckle it around the seatbelt. This would allow the seatbelt to slide in relation to the foam so when it is adjusted for different waists the buckle will still be in front and the padding can still be centered. I cut the 1" straps to length (leaving plenty) and sewed them onto the buckles in the appropriate places. I just did a straight stitch across these as they won't really be holding much.
I also needed to make the seatbelt into one piece as currently it was two pieces. I cut it to length, overlapped the ends a couple of inches and sewed them together using the X pattern you see on strappy things. I figure there's a reason why they sew that X pattern, it must be strong. The thread tension on the machine was a bit off for that thick seatbelt. I should've done a test piece and gotten it right. I didn't. My stitches are kinda ugly on one side of the belt. I also made sure I used a hefty needle (designed for jeans) and hefty thread (also designed for jeans) for this.
Step 7: Attach Hip Belt to Tubes
Now all that was left was to attach the hip belt to the tubes. I realized I could just run a couple of the 1" straps around the tube as well as the seatbelt. I did one on each side. That didn't work so well. In testing by dragging it about my yard (on the wheels), I couldn't turn and if I fell down, I might overturn the trailer. My kid probably wouldn't like that. So, I simply strapped it using one of the 1" straps right in the middle. This of course means I'm pulling on the joint between the two tubes. Hopefully it holds!
Step 8: Performance Update!
A recent comment reminded me I need to give an update. Unfortunately I've not found as much time to go skiing this winter as I had hoped. I've really only had this out once. So here's what that one time taught me.
1) It'll push/knock you down quite quickly when trying to go down hills. Be careful! Going up hills other than the very smallest, very gradual incline is nearly impossible (not surprisingly). Knowing that, I'll have to plan the locations where I ski accordingly.
2) When skiing/walking the trailer bounces forward and backward. This is due to the single connection point on the belt. The belt flexes into a V shape behind you when you pull forward. To fix this, I inserted a piece of 1/4 inch plywood between the seat belt and the 1" nylon straps (outside side of the seat belt). This prevents the formation of the V. I should add a picture detailing this.
3) The bungee cords used to attach the skis are adequate, but I'd like to try Velcro straps as I think they'll be easier to install/remove.
4) The seat belt is hard to get as tight as I'd like (loose = more bouncing). This is because pulling on the 'tail' to tighten it tends to simply rotate the belt around one's waist. Looking at backpacks, a lot of them have a 'tail' on each side to pull to prevent this. That setup also keeps the buckle centered in front of you.
5) Even though I haven't been skiing much, the skis for this project have been useful. My wife and I do typically have the time and the energy to go for a walk in the evening. Around my house, the roads often aren't plowed quickly so there is a layer of packed snow in some places, loose snow in others and sometimes bare pavement (the more traveled roads). I started taking just the skis along on our walks. On the bare and packed snow areas, the wheels roll with little resistance. On the loose snow, it can be a challenge to push the trailer/stroller. When I hit the packed/loose snow, I simply slip the 'socket' of each ski over each tire. I don't bungee the skis on, they stay put just fine. Even if one were to slip off, I'd notice it immediately and putting it back in its place would be quick and easy. It is much, much easier to push on the skis. When I reach a clear area of road, off come the skis in an instant!
6) Overall, I have been very happy with the outcome of this project. Over this past winter I also built a "jogging wheel" for the front. I need to instructablize that project. I also need to build a ski for that front wheel to use when walking like I described in the previous paragraph. No doubt I will continue to refine and improve on my Chariot trailer/stroller - well, at least until my son grows out of it. I'll endevour to instructablize and update as I do. I'll also update if/when I get to do more skiing.