View Full Version : why arent the spur and pinion gears switched?

06-08-2002, 03:53 PM
if some one switched the spur and pinion gears, i rotation of the motor would mean 5 or 6 rotations of the wheels. that means that if a motor turned at 20,000 rpm, it would turn at about 100,000 rpm. wouldnt this be faster?

06-08-2002, 04:03 PM
The motor simply would not spin, or if it did it would cause such a high current draw it would melt the shielding on the motor wires and fry the ESC. Electric motors usually do not have enough torque to spin the wheels 5 times for every 1 rotation or similar.

06-08-2002, 04:12 PM
If you have a multi-gear bicycle, shift into the biggest cog up front and the smallest gear in back. Then try pedaling from a standing start. Now imagine how hard it would be if the gear ratio was even lower! The low gear ratio makes it much harder to turn. If you started a manual transmission car in top gear from a standing start, it would stall because it does not develop enough torque to push that low of a gear ratio from a standing start; same with an electric motor. You need more torque to push (or pull or twist, whatever you want to call it) a lower gear ratio.

06-08-2002, 07:08 PM
if u just switched the pinion and the spur wouldn't the ratio stay the same though?

06-08-2002, 07:12 PM
no, it would be 1:5 instead of 5:1, for example

06-08-2002, 07:22 PM

06-08-2002, 07:26 PM
if you don't get that, here's another way

normally it might be 5:1, or 25:5. Reversed, it would be 1:5, or 25 times harder for the motor.

06-09-2002, 12:01 AM
let me say this.

The bigger the clutch bell the more speed you will get. and the smaller the spurr the faster you will go.

So if you were to switch a 14T clutch with a 60T spurr your engine would feel the full weight of the vehicle and then some. If by some weird chance of fate you are able to get a 5 speed tranny (you would need that to get that kind of gearing) your vehicle would be gone out of site st that gearing (I would say 200+MPH)

06-09-2002, 09:17 PM
5 speed tranny! 200 MPH! LOL. By the time it got to full speed it would be out of radio range, visual range and would go careening into a solid object into oblivion! The possibilities, lol.

06-09-2002, 09:43 PM
You have to understand something about electric motors: They do not have much power, but are able to turn very fast. Having a small pinion gear and a large spur gear takes advantage of this fact to power the car. Even if the ratio was 1:1, the motor would have a very hard time moving the car. Now if you gave it a little push start...

06-10-2002, 12:50 AM
I am no physics genius, or a mechanical engineer, but the problem of reversing the pinion/spur seems obvious.
An electric motor powers an RC car using rotational force. Rotational force is known as TORQUE.
Torque does not and cannot remain constant after passing through any type of transmission, even a simple pinion/spur mesh.
You can increase or decrease torque with gear ratios. Torque is not impacted by time, such as HORSEPOWER, whereby a certain amount of work must be done in a certain amount of time.
If you gear your car super insane high, such as reversing the pinion/spur, then you will have so little torque that you will not even be able to overcome rolling resistance, let alone air resistance. The vehicle would barely move, if move at all.
Then you must factor in the operational conditions of the motor itself. They cannot operate at 100% power for more than short bursts without self destructing (overheating, melting, smoking, etc). If the motor could not reach operating RPM within a few seconds, you will have a wasted motor.

06-11-2002, 06:40 AM
you are wicked smart dude.

06-11-2002, 12:21 PM
By the time it got to full speed it would be out of radio range, visual range and would go careening into a solid object into oblivion! The possibilities, lol.Attach a wireless mini-camera and use a Airplane controller. :cool:

06-11-2002, 12:34 PM
Wide open area+chase car (uhh, formula 1?)

06-11-2002, 12:36 PM
LOL. Jus' get in a Chopper and follow the damn thing. :D

06-11-2002, 01:55 PM
I still wanna make a car that goes that fast and run it on a highway while following behind it in a car...watch the drivers look on in confusion as a little 18" long car buzzes past at 150MPH :D

06-12-2002, 01:44 AM
Originally posted by bakerman
you are wicked smart dude. Nah, I am just a bakerman like you.

06-12-2002, 10:40 AM