As I say in the main text I came across this idea on Youtube, the whole project employs the gear program again and has turned out to be a well rounded little project. Oh Dear More Puns......

At keystage three I would use this project to display how an involute toothed gear is designed to mesh together very accurately and how at all times the two gears are in constant contact. I would explain how if gears don't mesh well they become noisy and inefficient.

We perhaps don't realise how noisy early gearboxes were until involute profile gears were mass produced. Even into the late seventies a car in reverse howled like a banshee.

At keystage 4 I would show this as an example of a project that fulfills all the criteria for a GCSE project.

It employs a mechanism with limited movement which I would point out in an exam would be detailed at length in a students portfolio.

It also uses multiple materials and jointing techniques. All of which are hoops that a moderator would like to see navigated as part of a good project. I would place this as a High B through to an A, depending on the finish.

Wood Gear Program

Future Design

Making Organically Shaped Gears

Mechani cards

More Wooden Gears

The Over Engineered Iphone Holder

I came across this projects as an idea on Youtube, it had not been made using CAD/CAM and was by its nature crude.

I decided that the addition of CAD / CAM would radically improve the look and end up making a relatively deep school project.

Some of the teaching aspects include; Full involute profile gears, Limited movement mechanism, Interference fits, Dowel pinning for location, Gear Ratios, Finishing techniques, Low friction material usage.

The project was cut from 12mm Plywood but this could be replaced by almost any other material, a 4mm router cutter was used and this was sufficiently small enough to keep the profile.

Gears

The Gears.

Many of us have tried to draw gears in 2D Draw and if there is an easy way it certainly isn't apparent to me.

The first variation of this project had a straight toothed gear that I guess worked using pure judgment only and I must say that it worked reasonably well.

However I have wanted a simple solution for schools for a long time, for many years I used the MIT University Excel spreadsheet involute tool calculation system that would produce a DXF output, this was the software used in the laser gears projects right back in the early days.

Although this will produce gears of any size any modulus and any centres it was very hard to use as it is designed to be of research and industrial quality. It did not work well with students.

So I have recently acquired the Gear Template Generator Program from http://woodgears.ca/gear/index.html It costs 26 dollars and can be bought with credit cards or paypal.

It will export to DXF, HPGL, CSV, and Sketchup.

I imported the DXF into 2D Draw and edited the line to stop the gear movement when the phone was at the extremes of 90 degrees.

Gears

2D Draw File - Download

To add more depth as at a GCSE level the handle was made from aluminium.

Handle

The profile file for the lathe is designed to show machining to include the use of the right hand turning tool.

Handle

Boxford Lathe File - Download

The legs were made using a size for size hole

Foot

The hole is 12mm wide (The thickness of the material as measured) and the height of the mortice is the same as the hole.

The natural spring of the wood when machining means that when the two pieces are hammered together with glue, no cramps are needed to hold the parts together while the glue dries.

This means that all the students can manufacture together without a shortage of resources.

The two gears are held on by the use of a turned shaft, a turned washer and an R clip.

This adds the use of knock down fastenings to the project and the use of washers to spread load, without the washer it would be possible for the R clip to scratch the back of the board as the gears turn.

Back

The R clips.

R Clip

A hole must be drilled across the pin to allow the R clip to be inserted.

On the Front it was decided that some form of lubricant / shield was necessary to stop the gears movement rubbing on the wood backing plate. In addition the painted versions would start to trade paint as the unit was operated.

One solution would be the use of Beeswax however it was decided that cutting large washers out of Overhead Projector plastic sheets would make a very low friction washer that would be able to protect the whole of the back of both gears without adding to much depth.

Washers

Two thicknesses were used on a basis that it gave more sliding surfaces.

It also stops painted versions scoring the paint as they move.

Complete set of CAd/CAm Files - In WinRAR compression

Complete set of CAd/CAm Files - In WinZIP compression