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• # Micro Car

Discussion in 'The main mechanical design forum' started by Katy, Apr 17, 2016.

1. ### KatyNew Member

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Apr 2016
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Hello!

I am currently constructing a micro-car that has to go through 4 continuous competitions: Speed Demon, Obstacle Course, 2m Ramp, Tug of War (where a micro car will try to pull another micro car). We are allowed to perform one mechanical change between 2 competitions.

Now, I want to use a 7:1 gear ratio, this way, the car's speed will be multiplied by 7 during the speed competition (gear ratio 1:7). Thing is, I'm a bit worried that the torque won't be enough since its being divided by 7 so any friction or back momentum would stop the movement of the wheel. Furthermore, we are provided with only one motor, so I can't put 2 motors to compensate , in addition to that I want to remove the some parts of the shaft that are not supporting anything so that the car becomes lighter. Basically, everything will increase the speed at the expense of the torque.
So, my question is: How do I get the minimum weight that the car should have so that it will be fine regarding the torque, and what do you think of the 1:7 gear ratio? How can I keep such a big ratio with minimum risks possible? In case you think it's better to go for a 5:1 ratio, I would like to hear about it too

Now, this way, after the Speed Demon competition, I would change the gears position, and put the big one (I'm gonna use an 84 tooth gear with a 12 tooth) on the motor and the smaller one on the shaft so that this time the torque would be multiplied by 7 while the speed would be divided by 7. This would be my mechanical change, and this would be great for the car to go through thee obstacle course safely and go up the 2 m ramp as well as have enough torque to pull the other micro-car.

Regarding the chassis, I'm using a 28 cm * 16 cm one.
Now, for the wheels, I'm planning to use a 5 inch diameter one, this way the car will go a longer distance per revolution

You read this long message, Congrats! Thank you so much!
Looking forward for some advice !

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