Go Kart Drive System Enigma: Tire Size Versus Sprocket Size: What Is The Best Combination?

Query: “I’ve this go kart and I need to make the rear tires greater. If I alter the diameter of rear sprocket in order that it will increase correspondingly with the rear tire, will the efficiency of the go kart undergo? In different phrases will the go kart go slower than earlier than and can the go kart have actually poor off the road acceleration?”

Good query, I’ve typically considered that myself. I’ve typically stated that the rule of thumb for a go kart to have optimum efficiency is to have the rear sprocket be almost 85% of the rear wheel diameter. The query is, does that apply only for 12 inch diameter wheels or does it apply to 16 inch rear wheels too?

The reply to that query might shock you. It stunned me. After I ran by means of the calculations a humorous sample emerged:

– A 12 inch diameter tire with a 12 inch diameter rear sprocket yielded a pace of 22 miles per hour at 7.three toes per second squared of acceleration.

– A 16 inch diameter tire with a 16 inch diameter rear sprocket yielded a pace of 22 miles per hour at 7.three toes per second squared of acceleration.

I believed that was misguided so I ran an entire slew of tires sizes with corresponding sprocket sizes and nonetheless got here up with the identical numbers.

So the reply isn’t any. No, your efficiency is not going to undergo when you enhance your sprocket dimension correspondingly with the wheel dimension.

What is going to occur if you don’t enhance your sprocket dimension is that the clutch will turn out to be over loaded and smoke. The go kart would require pushing to begin and could have horrible low finish efficiency.

However when you enhance the diameter of the sprocket in order that it’s 85% of the rear tires diameter, the efficiency ought to keep almost fixed.

That’s an surprising end result, however one you possibly can rely on in case you are designing a go kart from scratch. The rule of thumb stands: “The rear sprocket ought to be almost 85% of the rear tire dimension for optimum acceleration and pace efficiency.”

The belt drive system for instance is sort of depending on this relationship. The reason being that the drive pulley for a belt drive might be fairly giant, 1.75 inches in diameter, and requires that the rear pulley be as giant as potential.

Within the case of the wooden go kart that I designed, as a way to hold the ratio a easy one to 1 system (versus including a jack-shaft) the rear pulley needed to be the identical dimension because the rear tire. I used to be in a position to get by means of this drawback by making a wooden pulley which was sturdy sufficient to deal with highway circumstances, low-cost sufficient to make myself and better of all gave the efficiency that was wanted for good acceleration and total pace efficiency.