P4: Gravity-powered record player #

Build a gravity-powered record player. You can do this on your own or with a partner, if you feel like you’ll learn more working in a team. It should be able to play a 7" diameter record for 4.5 minutes at 45 RPM. If you decide you need a horn to amplify the sound, do not 3D print one. Instead, use paper, folded sheet metal, or the like. You might make a trigger mechanism that would start the record playing.

You will be given: #

1 vinyl record
4 or 5 steel needles
As many bricks as you request, within reason

Please set your learning goals for the project on Canvas as soon as you have time.

A few pieces of advice #

As you think about your learning goals, it would be pretty safe to assume that all of you will be able to make a record spin. Sure, you might have a last-minute failure where some pulley comes loose on a shaft, but generally, you’ll get it.

You will probably also find that the sound of the needle is surprisingly audible, even with a hastily constructed paper horn for amplification.

For most of you, the major challenge of the project will be figuring out how to control the speed of the record so that it spins at a constant rate. If you have no method of speed control, your record player will start slow, then spin really fast for a few seconds, and then tail off dreadfully when the weight bottoms out. Having a low-friction system is also pretty important– it’s difficult to control speed if the thing is really difficult to spin in the first place. Actually playing for 4.5 minutes is a pretty ambitious goal, but can be done with a low-friction system. We’ll talk about modeling this in class.

P4 proto-design: Thursday, March 12, at the start of class. The record should spin under gravity power by this date. Please submit some calculations on Canvas that suggest your record player could plausibly play for 4.5 minutes.

P4 final: Thursday, March 26, at the start of class.

P3: Make a puzzle ball #

In a team of 3, design and fabricate a spherical puzzle similar to the Perplexus. Your puzzle should contain a total of at least 15 puzzle stages. Each team member should fabricate at least 5 stages; each person’s stages don’t have to be contiguous. So that every person has to interface with two other people, the start and end stages must be made by the same person.

You will be given:

2 steel balls, 9 mm in diameter: McMaster 9292K44
1 transparent plastic ball, approximate inner diameter 195 mm

Restrictions:

Do not alter the big plastic balls. Do not drill holes in them or glue things to them. (This is for two reasons: I want to reuse them next year, but also, if you glue stuff in, you will very, very likely regret it. You need to be able to assemble, test, and then iterate. Adhesives do not iterate.)

Prototype due: Tuesday, February 24, at the start of class. Bring something that we can at least try to test out. It’s okay if it’s not perfect, but it should be a legit attempt.

Project due: Thursday, February 26, at the start of class.

P2: Build a sturdy wooden chair #

Build a chair out of wood. If you prefer, you can use a different material or build a different piece of furniture that holds up a person’s weight.

You will be given: #

1 square of plywood, 15.5 inches on a side
2 2x4’s, each 8 feet long
1 1x4, 8 feet long

You can use any other wood you can find or buy, but don’t go buy a bunch of fancy wood. The idea here is not to make an heirloom, but to make a structurally sound chair with basic materials.

A few guidelines to help your learning:

If you feel compelled to stain or paint your chair, please wait until after the due date and don’t do it in Nolop. (You should probably do it outside, but it’s probably too cold for that, which is why I’m trying to convince you not to do it.)
Think about the loads that your chair will experience when you lean back in it or tip in any direction. Try to reinforce the legs and back so that they won’t break.
Glue joint strength is proportional to surface area.
In general, fasteners shouldn’t take load directly– they should hold load-bearing parts in place.
If you feel the need to cut a 2x4 the long way, just use a 2x2 instead. We have a pile of those.
We also have a pile of 2x6’s that are fair game.

P2 due dates #

P2 learning goals: Tuesday, February 3, 11:59 PM on Canvas.

P2 due: Tuesday, February 10, at the start of class.

P2 learning results: Tuesday, February 10, 11:59 PM on Canvas.

P1: Build a mechanical car launcher #

Design, prototype, and refine a mechanism that can reliably hold and release a toy car with enough force to launch a toy car through a hoop.

The goal here is threefold:

design a means to control a large force from a rubber band with a small force from your finger
validate your design with mathematical estimates
practice building a smooth mechanism

You will be given: #

1 ball bearing, 8 mm OD, 3 mm ID, 4 mm width, part number 693ZZ
1 piece of steel rod, 3 mm in diameter
A pile of rubber bands, size 64
1 toy car for propulsion

You will need to obtain: #

Probably some cardboard for prototyping
Probably some plywood from the Nolop store for laser cutting

Deliverables #

For the second class, you should bring three things:

A design for your car launcher in the form of a detailed drawing or CAD model
Some mathematical calculations that suggest that your car launcher will propel the car to the right height
Some kind of physical validation that suggests you are on the right track, like a prototype or test mechanism

For the final due date, bring your car launcher to class, and we’ll test them out. There will be cheers and groans.

By midnight on the due date, submit some documentation: a screenshot of CAD model or a picture of your drawings, a PDF of your calculations, and a picture of what you built. If you are proud of what you built, make sure that the picture makes it look good.

P1 due dates #

P1 design, calculations, some design validation: Tuesday, January 20, in class.

P1 project due: Tuesday, January 27, at the start of class.

P1 documentation: Tuesday, January 27, 11:59 PM on Canvas.