Zip Line Pulleys

Project:
Upgrading the zip line trolley to aluminum pulleys

Difficulty Level (Easy, Medium, Hard, Insane):
Medium

Process:
Version 1: store bought bushing-based pulleys
Version 2: castors turned on the lathe with ball bearings
Version 3: custom cast aluminum pulleys with ball bearings

The first version just wasn't rolling fast enough and since the kids wanted an awesome ride I had to do something about that. I figured if I used the vulcanized rubber castors and turned them in the Gingery Lathe it would be a bit quieter and give a nicer, smoother ride. It actually worked out quite well until last night when I decided to go down the zip line one last time before going in and I just destroyed the rear pulley.

I have gone on the zip line numerous times (and so have 5 neighbor parents) and I knew that it would eventually have to be replaced because the kids were wearing it down so when it finally died last night I figured I might as well get going.

The process was fairly straight forward but it was rather time consuming:

1. Create the wood pattern
2. Cast the parts in aluminum
3. Machine them on the lathe
4. Install
5. Enjoy

Videos:

Once they were installed:

Our neighbor came over with his GoPro so here are some more videos:

Zip Line à la GoPro

Pictures:

The arrangement of pulleys and guide rollers

The finished (version 2) trolley

After installing the (version 2) pulleys

The pattern for the pulley. Note the thin rod is to make an imprint for the core, the larger knob on the left was only so that I could mount it on the lathe and the right, big part, was for the actual pulley

Another angle

The freshly made core

I found that making 1/2" cores was really difficult because they kept breaking. The way to make it almost 100% successful is by putting a rolled up piece of paper between the core and the core box.

The pattern in the sand mold

The furnace going and the 3 mold boxes in the back

Taking out one of the casts

After it was cleaned up but still with the risers and runner attached

Another angle. You can see the raw cast of the pulley at the left

The last cast before shaking it out

The pile of reclaimed green sand before stowing it away

The raw cast mounted on the lathe

Another angle

After cleaning it up it turned out quite nicely

Almost done with the groove of the pulley

Parting off the pulley

I made 3 casts, two are clean-turned, the third one is done

Close-up of the finished pulley

Another view

The second pulley before cutting off the collar

The drilled out pulley before reaming it

The third pulley

This is the second pulley that snapped when I tried to install the bearings with the vise. Note to self: Make sure you ream the hole big enough!!!

Tools:
Ange grinder
Measuring tape
Pencil
Bench grinder
Drill press
Gingery Lathe
Bi-metal hole saw kit
Reamers
Vise
Socket set
Adjustable wrench
MIG welder
Home Foundry
Hack saw
Tap & Die set
Alan keys
Clamps
Broom

Materials:
3/16" metal for trolley sides
2 casters
12 washers
Nuts & bolts
Hook
Aluminum
Four 1.25" bearings

Cost:
About $20.00

Time:
15hrs

Savings:
$80.00

Conclusion:
The 3rd version pulleys are INCREDIBLY fast! The kids (and I) LOVE it!