Apr 20, 2015

CPW Swingset

Sandbox backhoes weren't the only building project happening during CPW. Jennie and I also decided to teach prefrosh how to build a swingset: we would cut the wood beforehand, and prefrosh would drill holes and attach pieces.

For a few prefrosh, this was their first time using a drill
We were originally going to stake down the base frames, but it turns out that the courtyard dirt is ridiculously packed for wooden stakes. We searched for metal stakes, but ended up building pontoon-style stabilizers instead. Since the ground was also slightly uneven, one frame still ended up rocking a bit if two people were on the swing at the same time.

Blueprint given to prefrosh. They rolled with it
The double 2x8 crossbeam turned out to be a good decision. Even though it was firmly seated on the A-frames by bolted supports and screwed directly to the 4x4 frame, the crossbeam still visibly twisted when two riders were out of sync. I doubt a thinner crossbeam would have sustained our abuse as well.

We had to replace our swing ropes every day since the wooden beams would fray the ropes and the ropes would wear grooves into the crossbeam, even with protective t-shirt padding. In the future we will replace the ropes with something like a webbing-light chain system that rubs less.

In the meantime, we enjoyed our functional swingset and the lovely weather of CPW.

CPW chairs being small children


Apr 19, 2015

Do you want to build a backhoe?

Welcome to CPW: Campus Preview Weekend, when we all pretend schoolwork doesn't exist and celebrate our prospective freshmen! The theme this year is "Kindergarten," which is a funny contrast to spring break's unofficial theme "Is College; No Parents"

I wanted to make a sandbox digger in the style of this instructable, out of dimensional lumber and prefrosh labor. The goal was to make a design on which prefrosh could learn how to use powertools (high error tolerance), but also have a fun, functional machine at the end of CPW.

Jennie and I sent in a design and safety proposal to our CPW chairs and to MIT's office of Environment, Health, and Safety. (EHS) Our proposed design looked like this:

EHS got back to us with various safety questions, and also requested extremely detailed drawings of our design and assembly process. I was going to make these anyway, since the plan was for prefrosh to do nearly all the construction (minus cutting wood). We sent in six pages of drawings in the style of LEGO blueprints.

Somewhere between making plans and starting construction, we decided to switch out bolts for 1/4" and 3/8" threaded rod, courtesy of MITERS.

Construction and assembly happened on the Saturday of CPW. Prefrosh learned the wonders of double-nut threading.

final product!
We discovered that 3/8" OSB (original plans called for 5/8") was not nearly structural enough to support our lazy susan turntable bearing, so we last-minute swapped them for 2x8 squares. We also ended up with creative supports for the 4x4 -> base connection.

But at the end of CPW, we had a working backhoe! Prefrosh built, Upperclassman tested.