Pump Track
Pump tracks are loops where the bumps are designed such that you can ride around on them (generally on a bike) without pedaling; you can simply raise and lower your body weight to generate forward movement. I don't live close enough to one, so I figured I'd spend some time collecting pallets and stick 'em together to make a pump track in my backyard.
Started with some pallet collection while I designed the track. They're everywhere! I got really good at breaking up a pallet without destroying too many of the planks, snapping the nail heads off, or hurting myself.
The first requirement was no glue. I wanted this thing to stay together when it rained. So that meant only nails, and only solid wood (no plywood, particle board, etc). The second requirement was to fit into my backyard. After some measurements I decided I could squeeze a 20x40 ft oval in there, so I went and sketched something up in OnShape following the advice from Lee in Welcome to Pump Track Nation v2. Well worth the $10! The overall turn radius and ratio of height-to-length of the straight sections stemmed from the book.
I played around with different sized turns, and landed on something that was still plenty steep to keep your speed up, but not so huge that it'd take forever to build. Also I wanted to keep plank lengths down since most of my pallet wood was <48".
Once I had a huge (huge) pile of pallets broken down, I began by nailing the planks into boards, then after generating a sinusoidal curve by spreadsheeting some lengths and extrapolating using a pencil and my eyeballs I cut the boards into the two sides of the track sections. Those got some cross braces to form the frame.
First section assembled! This was fun to ride on without any turns, so I got some motivation to keep going.
Using member lengths from CAD I assembled each 45° section of the curve by creating the 5 frames, placing them on a chalk curve on the floor, then just placing stringers on top and doing whatever I could to nail them together. This was almost completely done with scrap, including nails, so I had my work cut out for me actually getting the connections solid. Lots and lots of blocking, strange angles, and more blocking.
First of four built!
Second section. You get the idea. The third and 4th were mirrors of one and two.
Finished! Well ok not finished. I ran out of time to get it done in time for a party we had, so I just got a big U done instead of the entire oval. Hard to show the whole thing since we put up pallets as barriers to keep partygoers from walking through the track. But rest assured it is a ton of fun. We had it up for about 8 months before repurposing the backyard.
This was done after the kids went to bed over the course of a few weeks. I learned a lot about how complex such a curvy project is to hammer out with straight members.
2022