Modelling Wheels

Description

Wheels for working models are available commercially, often in wood or plastics or as found in Construction Kits, but they can readily be made from pre-cut discs of Card, Ply or MDF. Alternatively, 'found objects' such as Cotton Reels and CDs can be used.

If there is access to some workshop equipment, they can be cut out from Manufactured Board or Softwood for example. They can also be cut out by hand using a Coping Saw and finished to shape with a Bench Sander, if available - or even 'turned' on a Lathe!

Using Pre-cut Materials

Card and MDF Discs

Pre-cut discs of Card, Ply or MDF can be purchased and either used separately or glued together with PVA to make wheels in a range of diameters and widths. Note:The thin edge of a card disc results in very little Rolling Friction whereas doubling up MDF discs can make wider wheels which have more Traction. Which would be best for a balloon powered vehicle and which for those driven through the wheels by an electric motor for example?

Found Objects

CDs and Cotton Reels	CDs can be used but first need to have the large centre hole reduced to accept a Dowel Axle. Plastics centres are commercially available but a small diameter MDF disc can be used to solve the problem. Alternatively, a cotton reel can be used as shown. Note: Such large diameter wheels may take more effort to get them the moving but once started are likely to free-wheel for longer. Can you think why this should be so? (think about the CD radius being a Lever and its point of contact with the ground as the Fulcrum. You may also want to learn about Inertia and Momentum).
Soft Drinks Can	Empty soft drinks cans may be used to make roller-type wheels and Pulleys. Provision to locate the Dowel Axle needs to made in a similar way as for CDs. Such wide wheels can be seen as a combined wheel and pulley and may easier to locate the drive belt from an electric motor around. They are also useful if modelling a Conveyor Belt or the feed rollers used in automatic factories and at some supermarket checkouts for example.
Screwtop Jar Lids	Typically found as coffee jar lids, these have a deep and serrated rim which can provide good grip (or Traction) if needed. A small MDF or Ply disc glued in the centre will provide a better location for the axle than the thin plastics of the lid.
Note: If CDs, cotton reels, plastics lids or drinks cans are used, card or MDF discs would have to be glued to them using Double-Sided Tape, an Adhesive such as epoxy resin or Glue Gun since PVA would be ineffective.

Cutting Out Circles

Using a Holesaw	If there is access to some basic workshop equipment (e.g. a Drilling Machine in a neighbouring secondary school) wheels can be cut from a varety of materials using a Hole Saw. Alternatively, older students or adults could use this in a Power Drill providing the workpiece is securely clamped to the workbench. Whichever machine is chosen, it is easiest start with a strip of material just a little wider than the finished diameter. This allows the sawdust to clear quickly from the sides. Drill from one side until almost all the way through and then turn the strip around to complete. This minimises any chipping as the saw breaks through, and the cut disc is easier to release.
Adding a Tyre	Bicycle Inner Tubes can be used to model tyres - and actually provide extra grip. Choose a tube diameter a little less than the finished wheel size and cut into pieces about 2 or 3 times the wheel thickness long. With a little effort, these can be stretched over the wheel disc and they will snap into place around the side of the wheel to simulate tyres.
Using a Coping Saw	These have a replaceable fine tooth blade which can be adjusted to different angles using pegs and tensioned by tightening the handle. They are most easily used by gripping the handle with both hands and holding the work as shown. If used as shown the blade should face forwards and the work can be rotated as the cut is made around the drawn circle.

DT Online Buyers' Guide

Notes:

• MDF Discs which are pre-drilled are most useful if available, otherwise this might be done as preparation before using with younger children - alternatively a Hand Drill Stand could be used (if neccessary, adults or older children can cut them out of strips of MDF or Ply using a Holesaw).
• Dowels 4mm, 5mm, and 6mm are useful sizes for axles.
• Florist Wire is easily bent into shape whereas stiff wire, such as Brass Brazing Rod, is more suitable for connecting rods.

• See also Stripwood Components Buyers Guide and Stripwood Tools Buyers Guide

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MDF and ply discs	Wood Dowel Rod	Wooden Clothes Pegs	Wooden Matchsticks for Craft	Wooden Lolly Sticks for Craft	Wooden Cocktail Sticks and Skewers for Craft	Unpainted Wooden Beads	Polystyrene Balls	Florists Wire	Brazing Rod
Cotton Reels	Wooden Spools	Copper Foil Tape	PVC Tube	Assorted Cable Ties	Hook and Loop Stick On Tape	Coloured Card for Craft	Greyboard	Cotton String	Elastic Bands