| The main obstacle to driving a go kart is getting that | | | | Increasing the radius allowed you to use the same |
| spinning motion of the engine into useful spinning motion | | | | amount of force you were using before, but now all of |
| of the wheels. | | | | a sudden the bolt came free. This is expressed in the |
| There are a couple of things to keep in mind when | | | | following equations, torque 1 being the small handled |
| dealing with this transfer of motion though: | | | | wrench, and torque 2 the long handled wrench. |
| -Engines run continuously: go karts do not | | | | Torque 1 = Radius Short (6 inches) x 10 pounds = 60 |
| -Engines cannot have a load suddenly dropped on | | | | in-lb |
| them, they need a gradual engagement | | | | Torque 2 = Radius Long (12 inches) x 10 pounds = 120 |
| -Engines do not have enough torque by themselves to | | | | in-lb |
| just drive a wheel, a ratio reduction is required to get | | | | As you can see the torque level increase by 2 times. |
| the torque level at the wheels so it is manageable by | | | | (Torque is expressed in terms of "inch-pounds" or |
| the engine. | | | | abbreviated as "in-lbs." |
| -The go kart must stop, while the engine is still running | | | | Go Kart Drive Line |
| To get the power from the engine to the wheels a | | | | Similarly when you look at a sprocket chain connection |
| connection is required. This connection can come in a | | | | you see that the chain is grabbing on to the teeth of |
| whole wide variety of forms: | | | | the sprocket. This grabbing spot is located a certain |
| -Belts | | | | distance from the center of the sprocket. Say around |
| -Chains | | | | 4 inches radially. |
| -Belt and Chain Combinations | | | | The sprocket for the clutch typically is very small, and |
| -Drive shaft | | | | has a diameter of typically around 1 inch. |
| The most common drive system is the centrifugal | | | | The chain is grabbed by the clutch sprocket tooth and |
| clutch-chain-main drive sprocket layout. | | | | then transfers this grabbing motion as tension into the |
| This in and of itself is a form of transmission. Typically | | | | back sprocket, or the larger drive sprocket on the |
| the ratios range from 7:1 to 10:1. (This may be all Greek | | | | gokart axel. |
| to you so lets back up the truck.) | | | | The ratio between the small sprocket and the larger |
| Torque | | | | sprocket is related to the torque arms. The ratio is |
| When an engine spins it develops a twisting force | | | | basically the large torque arm divided by the small |
| called torque. You have probably seen that a weed | | | | torque arm: |
| whacker will quickly succumb or bog down in high | | | | Ratio = Large Sprocket (4 inches)/Small Sprocket (.5 |
| weeds, whereas in light grass it will easily cut the | | | | inches) |
| grass. | | | | Ratio = 8:1 |
| The way a weedwhacker works is to use the string | | | | This ratio is used in a couple of ways. |
| to slice through the grass. The slicing action requires a | | | | - First it is used to calculate the power required from |
| force or a pushing of the string through the grass | | | | the engine to the rear wheels. |
| blades. This slicing force is related to the length of the | | | | - Secondly it determines how fast the go kart will go. |
| string. In fact if you have a long string the motor bogs | | | | Translation: |
| down and the weed whacker will not slice through the | | | | - The amount of torque required at the rear wheels is |
| grass as well. | | | | 8 times what the engine can put out. |
| A prompt reduction of the string length will make the | | | | - Secondly the engine spins 8 times as fast as the |
| motor spin faster and the string to work more | | | | rear wheels. |
| effectively. | | | | Typically a go kart weighing about 100 pounds with a |
| The reason for this is as was stated before: "slicing | | | | 150 pounds person will scoot along pretty good on |
| force is related to string length." The longer the string | | | | level ground. |
| length the more force is required. | | | | When the go kart tries to go up hills that can be too |
| In mathematical terms this is expressed as a | | | | much for the go kart, and will cause the engine to stall |
| combination of force and length. And is described as | | | | or make the clutch slip. |
| Torque. | | | | To get past this a system of changing ratios is |
| Torque = Force x Radius | | | | needed. That is called a transmission. |
| Another way you will recognize torque is when you | | | | There are various ways to address this changing |
| are trying to loosen a very tight bolt. | | | | ratios, with belt drives, transmissions or variable |
| When you put a long bar on the handle of the wrench | | | | clutches. |
| all of sudden the bolt is a lot easier to remove. The | | | | To keep the go kart simple though (low cost) the most |
| amount of twisting force did not change, but the | | | | common system is the centrifugal clutch or one ratio |
| mechanical advantage did increase. The lever arm got | | | | system. |
| larger, but the force remained the same. | | | | |