My car is not moving forward. Can someone help me with the error I might have made. I am using a 100ml pet bottle, DC motor, 9 V battery and a fan . The steps GIVEN  are very clear yet thr is something I missed. Pls help

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The problem is the battery - it is too weak for a normal motor.
Either get extra heavy duty batteries and hope or select a motor with far less current draw.

Going by eye, that motor looks like the ones we use in lessons. They're 3V, and that's a 9V battery.

I know that the size and shape of a water-propeller needs to be matched carefully to the rotational speed of the drive shaft (spinning faster does not always mean travelling faster), maybe the same is true of air-screws? Could it be spinning fast enough that turbulence behind each blade robs the next of thrust?

MonaG5 (author)  Downunder35m1 year ago

Thank you so much. I would change the battery and try. This is my son's first project, he will be overwhelmed if this works. Grateful to you.

If you have some old cell phones with no use try to rebuild using the tiny vibration motor inside.
With a downscaled model and two AA batteries it should run for hours.

Judging by looking at the propeller it looks as though the car's propeller can only force air in one direction. That direction looks as though it can only push the car in the direction of the propeller. I would try reversing the the propellers rotation to try getting better results. To get the motor to move the other direction I would not know how to do that. I unfortunately only know how to control a dc motor with a driver not a battery alone. Good Luck!!!

You can not judge that by the image as you don't know which the motor rotates when connected to power.
And as reversing the polarity changes the rotational direction of the motor.....

Look I am guessing that the propeller can only force air in one direction because of the curvature of the blade. It looks like it can only move air one way. Also I don't know what direction the motor is rotating I am just saying that that could be an issue. I do not know if that is actually the problem. I am sorry if I didn't make that clear enough.

Kiteman1 year ago

If the propeller is spinning properly, the axles may be too stiff - make sure they turn freely.

MonaG5 (author)  Kiteman1 year ago
Thank you for this. I checked , the axles are not stiff. But it doesn't run. Your suggestion is appreciated
gmoon1 year ago

Did it test-spin? Hope it's not a 1.5 or 3V motor...