A zipline is a pulley device designed to ride a rope or wire using gravity as propulsion. There is usually 2 or more pully type wheels that sit atop the rope and guide the device along the wire. This instructable will show you how to construct one. Keep in mind this is an informational instruction and the author holds no responsibility for the use or outcome of your device. I can only show you what worked for me.

Matereals

1   16 - 20 ga sheet metal
2    1/4" x 4" steel pipe
1    1/4" pipe connector
2    Pulleys
2    Rollerblade/skate board bearings
2    3/4" rubber 'o' rings
2    3/16 x 1 1/4" bolts
4    3/16" nuts
2    3/16" lock washers
1    Tube of grease

Tools

Drill (1/4" drill bit*)
3/16 drill bit
Dremel (small sanding attachment)*
Crecent Wrench or Pliers
Metal shears/ Tin snips
Hack saw
Permanent marker
Ruler
* You will not need this if you have a 1/2 " drill bit, except for some fine tuning. This is just what I used.

Step 1: Preping Matereals

I used only 2 pullys since this is the minimum needed for stability of this device. You don't need the whole pulley, just the wheel, so you must remove this from the rest of the unit. This is a 1 1/4 inch wheel in the middle of the frame. I extracted this by putting the blade of the hack saw through the arch of the pulley, refastening it, and sawing off the pulley axel from the inside. Do this for. both pulleys, or however many you choose to use. The more pulley wheels you have on your device, the less friction there will be. In some cases this may not necessarily be a good thing, because less friction means more speed with the inablilty to brake.

Next you must outline your frame design onto a piece of sheet metal. I used a somewhat triangular pattern. Its important to have accurate measurements because balance is key for a device such as this. My measurements were 4.5" x 1.5 " x 2 1/4 x 1" x 2 1/4 x 1.5 . I did this for both pieces, and measured the spots where I would drill holes for the axels and handels to go. I placed my axel holes; down 3/4" from the top. From left to the center of the axel hole is 1 1/8 " and the space to the next axel hole is 2 3/8 inches which leaves you with 1 1/8" to the right side of the frame.

The hole for the handel I measured from the top which was 4.5" across. I marked my 2 1/4" point and drew a line down to the bottom area which crossed at 1/2". I measured 1/2 " up the line I had drawn and marked the center of where I would drill the hole for the handels. After you drill the 1/2" hole for the handel, you will have about 1/4" left between the bottom of the handel and the bottom of the frame.

Last thing you need to prep is the pulley wheels. All you need to do is add a generous amount of grease to the center. The grease will reduce the friction of the wheel rubbing against the threads of the bolt. I used white lithium grease on mine, and it seems to work well.

Step 2: Building the Unit

Frame

Now that you have all your measurements, you need to cut out the frame from the sheet metal. Use your metal shears and take it slow. After you cut both out, stack them together on a surface you wont mind drilling on.

Use your 3/16 drill bit to drill the holes for the axel. Drill both pieces of metal at the same time as they are stacked together. If you find it difficult to hold them even, you can clamp a piece of 2 x 4 to your work bench with a 'C' clamp. Place the top part of your frame, flush against the wood, and clamp the frame with a 'C' clamp as well.

If your using a 1/2 inch drill bit to drill the hole for your handels, then you can disregard this paragraph. If your using a smaller bit, and you have finished drilling the holes for your handels, but its too small, then you will need to get your dremel with small sanding bit. Use the sanding bit to grind out the hole you drilled, working in circular motions. Keep grinding until you can easily place the piece of steel pipe in the hole. Be careful not to make the hole too big. Its better to have a tight fit then a loose one, as this can cause instability to your unit.

Assembly

Everything from this point on is pretty much assembly. Place the 2, 3/16 bolts you have, through the top 2 holes in your frame, and lay it so they are facing up. Begin adding parts to the bolts starting with the 'O' rings. Next the bearings, then the pulley wheels. Add 2 of the 3/16 nuts to the end of the bolts, but do not tighten them completely. Tighten them only until the bolt feels stable. This will allow the wheel to move freely. Now place the other side of the frame on top, and add the lock washers and remaining nuts. Do not tighten these until you have placed the connector for the steel pipe in the center of the unit, flush with the holes for the handels.

To keep the pipe connector flush with the holes, screw one of the lengths of pipe into the connector. Then tighten the bolts with the wrench or pliers and screwdriver. Finally add the 2nd piece of steel pipe to the other side.

Congradulations, you now have a home made zipline pulley ready for many types of recreation. I hope you enjoyed this instructable, and feel free to leave comments. I have many more projects I am working on so stay tuned.