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# Large scale sit-n-spin

Remember the fun spinning toy from the 70s and 80s? We're building one that adults can enjoy.

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We (Jake, J., Sophi, and Dan) decided to make a playground toy for adults. A sit n spin that displays patterns and messages on the outer ring as it spins.

This project has some good challenges:

The spinner needs to be able to fit 2 people at once and be able to support the unexpected person that jumps on top of it.

We're building the spinner itself from wood, and we think the bearings need to support 1000 lbs.

It would be really fun to have a POV display on the outer rim and we want it to be independently powered. We're researching powering it by dynamo.

### spinner_v2 v4.f3d

f3d - 714.74 kB - 06/10/2018 at 20:48

• ### Design progress so far

Sophi Kravitz07/04/2018 at 20:36 0 comments

This is the innermost part of the inner bearing.

• ### Mechanical Design

The spinner will hold two people sitting on its platform, and be able to support two more people climbing on top of them. So 4 people * 250 lbs = 1,000 lbs.

We also need to know the dynamic and thrust loads in order to source the bearings that will take the force of all of these people pulling on the shaft.

Dynamic load refers to a force on a system because it is accelerating an object in a given direction. So that's the people sitting on the platform, and it is not moving in the vertical direction.

However, there are dynamic forces in the horizontal directions. The horizontal dynamic load is a wheel turning at 60 mph (that would be crazy, but it's a high estimate) and going from 0 to 60 in 20 seconds.

Rate of acceleration: 60 mph = 88 ft/sec, divided by 20 sec = yielding 4.4 ft/sec^2.

Force = mass * 4.4 = (200lbs (platform) +1000 (people)) * 4.4 = 5280 lbs.

These are ridiculously high estimates. I think spinning at 60 mph might make people puke.

Thrust load runs parallel to the axis of rotation.

• ### The dynamo

There will be LEDs because everything is better with blinky!

Dynamo notes:

Brightness is commonly described in two different units of measure: lumens and lux. While battery-powered lights are commonly rated in lumens, dynamo lights are more often rated in lux. Whereas lumens are a measure of the total amount of visible light emitted from a source, lux is a measure of the intensity of light in the usable portion of its beam pattern. This means that two lights with identical lumen ratings can have very different lux measurements, depending on how the light is focused.

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