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Time vs. mass
Posted: January 19th, 2019, 10:44 am
by sciencecat42
How does the time/speed of the car relate to its mass? My car is between 200-300g, and it doesn't seem to go that fast. What kind of mass would you need to get down to a 10 second run time?
Re: Time vs. mass
Posted: January 21st, 2019, 9:47 am
by dragonfruit35
The speed of the car doesn't depend solely upon its mass. How big are the wheels on your drive axle? Their size affects their circumference and thus how far they travel with every wind of string.
Re: Time vs. mass
Posted: January 21st, 2019, 10:30 am
by sciencecat42
dragonfruit35 wrote:The speed of the car doesn't depend solely upon its mass. How big are the wheels on your drive axle? Their size affects their circumference and thus how far they travel with every wind of string.
I have 3in wheels currently. How much does drive axle diameter matter? I was planning to switch to a smaller diameter and smaller wheels, but I'm not sure if that would increase speed.
Re: Time vs. mass
Posted: January 21st, 2019, 1:24 pm
by falcon1236912
sciencecat42 wrote:dragonfruit35 wrote:The speed of the car doesn't depend solely upon its mass. How big are the wheels on your drive axle? Their size affects their circumference and thus how far they travel with every wind of string.
I have 3in wheels currently. How much does drive axle diameter matter? I was planning to switch to a smaller diameter and smaller wheels, but I'm not sure if that would increase speed.
Smaller wheels, a shorter drive arm, and a larger diameter axel will increase speed.
Re: Time vs. mass
Posted: January 21st, 2019, 1:49 pm
by sciencecat42
falcon1236912 wrote:sciencecat42 wrote:dragonfruit35 wrote:The speed of the car doesn't depend solely upon its mass. How big are the wheels on your drive axle? Their size affects their circumference and thus how far they travel with every wind of string.
I have 3in wheels currently. How much does drive axle diameter matter? I was planning to switch to a smaller diameter and smaller wheels, but I'm not sure if that would increase speed.
Smaller wheels, a shorter drive arm, and a larger diameter axel will increase speed.
I get why smaller wheels help (less rotational inertia) and a shorter drive arm helps (less distance for more force) but what does a larger axle do? What if you decrease both wheel and axle size?
Re: Time vs. mass
Posted: January 21st, 2019, 5:15 pm
by falcon1236912
sciencecat42 wrote:falcon1236912 wrote:sciencecat42 wrote:
I have 3in wheels currently. How much does drive axle diameter matter? I was planning to switch to a smaller diameter and smaller wheels, but I'm not sure if that would increase speed.
Smaller wheels, a shorter drive arm, and a larger diameter axel will increase speed.
I get why smaller wheels help (less rotational inertia) and a shorter drive arm helps (less distance for more force) but what does a larger axle do? What if you decrease both wheel and axle size?
a larger axel provides more torque and will help increase speed. If you decrease both the wheel size and axel size, the speed would change relative to the new wheel to axel ratio.