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Ground Propulsion
The wheel has been around since the dawn of recorded history. The skid goes back even further. So long as there have been people who build things, people have built things that make moving other things easier.
To determine how large a motive drive-train you need, you must first decide how fast you want your vehicle to be. Choose a top speed in kilometers per hour. To find the power required for your desired speed, multiply the speed by itself, and then by the mass of your vehicle (in tonnes). Then divide by the suspension factor (SF) for your motive drive-train, as found on the table below.
| TR | Type | SF | Mass (kg) | Cost (₠) |
|---|---|---|---|---|
| -5 | Skids | 90 | † | † |
| -4 | Wheels | 160 | 1.8 × Power + 36 | Mass × 5 |
| -2 | Wheels | 360 | 1.8 × Power + 36 | Mass × 5 |
| -1 | Wheels | 650 | 0.9 × Power + 18 | Mass × 5 |
| 0 | Wheels | 650 | 0.45 × Power + 9 | Mass × 5 |
| -1 | Tracks | 250 | 2.5 × Power + 60 | Mass × 10 |
| 0 | Tracks | 360 | 1.5 × Power + 30 | Mass × 10 |
| 0 | Legs | ‡ | 2.7 × Power + 120 | Mass × 25 |
| +1 | Legs | ‡ | 1.35 × Power + 60 | Mass × 25 |
| +2 | Legs | ‡ | 0.5 × Power + 30 | Mass × 25 |
†Skis cannot be powered, but are included here for their Suspension Factor.
‡Regardless of TR, suspension factor is 160 for two legs, 250 for three legs or 360 for four or more legs.
To determine the volume of any drive-train, divide its Mass, in kilograms, by 150. This will give its volume in cubic meters. For a Legs drive-train, this volume must be split equally between all legs.
Power Requirements
Most of the above drive-trains require a powerplant to operate. As long as your powerplant can deliver the required power, you're good to go.
But what if you don't feel like using a direct powerplant? Maybe you're building a land-sailer, or a jet-propelled car. Maybe you need to know how fast your airplane can taxi, in order to make sure it can reach take-off speed.
You can use the Power formula backward, in order to find your land speed based on power delivered. However, you only receive full power for direct drive of your ground drive-train, or for animals towing your vehicle. For every other source of power, divide the delivered power by four.
To determine your land speed, multiply the power by your Suspension Factor, then divide by your vehicle's mass. Find the square root of this value. Drop fractions.