Table of Contents
ADVANCED: DOWN-WIND FASTER THAN THE WIND:
Students learn:
| Curriculum | Learning Activities |
|---|---|
| SCIENCE | Real world experimental design and data collection |
| TECHNOLOGY | Use technology for diagnosis and/or analysis of materials |
| ART | Record, document and publish a multi-media history of the project |
| ENGINEERING | How to design and build a wind powered vehicle |
| MATHEMATICS | Methods of evaluation and prototyping using authentic data |
An advanced STEAM activity where students investigate advanced engineering concepts using sailing technology as a method of illustrating the application of those concepts. Inspired by Stanford University
Directly Downwind Faster Than The Wind (DDWFTTW):
In the early 1990s a page was published describing a wind-driven boat, little more than a toy, that could progress directly into the wind that powered it.
There was considerable interest in this and after experimentation this updated version called Windspinner.
Source -Wingsail & Rotary Sailing
Is it possible to travel directly down-wind faster than the wind, powered only by the wind?
Background Links:
- Mythbusters challenge - Can a wind-driven car travel downwind faster than wind: https://www.youtube.com/watch?v=xHsXcHoJu-A
- Cart moves faster than paper: https://www.youtube.com/watch?v=E7vcQcIaWSQ * The machine that moves faster than the ruler: https://www.youtube.com/watch?v=k-trDF8Yldc
- Relative points of vjew https://www.youtube.com/watch?v=9Yt4zxYuPzI
Videos:
- DFTTW (DDWFTTW) - Part 1/3: https://www.youtube.com/watch?v=T-ArigMKhi4
- DDWFTTW - Part 2/3: https://www.youtube.com/watch?v=p0rhgop5wEM
- DDWFTTW - Part 3/3: https://www.youtube.com/watch?v=gSHNqrF93MU
- Scaled-up: https://www.youtube.com/watch?v=5CcgmpBGSCI
Source: http://www.rtfa.net/2008/12/02/downwind-faster-than-the-wind-dwfttw-parts-list One 1metre x 5mm thin wall carbon tube and acessories same or example equivalent to these:
DDFTTW Test Vehicle Parts List:
| US$ Cost | Item/Description |
|---|---|
| 2.00 | 3/8″ soft aluminIum tube (24″) from plumbing dept at OSH |
| 1.00 | Nuts and bolts to hold aluminum tube to gearbox |
| 1.00 | HDPE Bearing block to support rear prop-shaft bearing (Tap Plastics) |
| 2.00 | 5x13x4 - 5mm Inner x 13mm Outer x 4mm Wide - 2 front prop shaft bearings (Avid 695-RSZ) |
| 3.00 | 5x11x4 - 2 axle bearings & 1 rear prop-shaft bearing (Avid MR115-RSZZ) AU EBay Example $12 |
| 7.00 | 1x3mm + 1x4mm + 1x5mm x 1metre Carbon tube for prop shaft and axleAU (AeroMicro) |
| 1.75 | GWS 3.00″ Wheels - 2 at $1.75) (Tower LXHHZ8) AU $5.99 2.5in NZ $4 |
| 4.15 | Century Hawk Tail Gear Set AU Plastic $5 (Tower LXMJX7) |
| 6.95 | Century Hawk Pro Tail Gearbox - AU $17.35 (Tower LXLKD0) |
| 9.99 | 0.08″ Music/Piano wire - 2 pieces at 2″ used for axle step down @ 9.99 for 15 pieces at 36″ each (Tower LXWV01) |
| 9.69 | 1.25″ of 0.063″ Music/Piano wire for rear axle @ 9.69 for 15 pieces at 36″ ea (Tower LXWV00) |
| 2.99 | Dubro 2″ Micro Lite wheels; 2 for $2.99 (Tower: LXAZC6) |
| 21.00 | Prop GWS 15×7.5 Propeller (6 for $21.00)AU14x7 $4.52 ea $5.48 (4pk) (Tower LXHHZ1) |
| $79.72 | Total: $79.72 Plus Tax & shipping** (includes lots of leftovers) |
Suppliers:
- OSH: Orchard Supply Hardware
Additional sundries:
- super glue (use 'foam safe' type super glue that does not melt plastic!)
- sand-paper
- 5mm drill bit and some standard sized bits
- exacto knife
- Metric allen wrenches
Build Hints:
The finished version should look something like this:
The most important thing is to get absolutely minimal friction and the correct advance ratio.
This means you should definitely start with exactly the prop, gears, and wheels specified. There is a big gear and a little gear. The little gear goes on the axle and the big gear goes on the prop shaft. I sand the shoulder off the back of each gear to give a very loose gear mesh.
Make sure the prop spins clockwise from behind when the cart is pushed forward.
Use rubber bands on wheels for better traction – when needed (e.g. wheels may work fine on treadmill without).
To help steer straight, bend the aluminium tube very slightly to turn the rear wheel until it doesn’t veer off either side of a treadmill (done during setup).
Mythbuster Challenge (on youtube): https://www.youtube.com/watch?v=xHsXcHoJu-A