# I need help in figuring out the ratio on motor speed versus gear ratio versus tire size

Discussion in 'Science and Technology' started by Daryl Hunt, Mar 17, 2018.

1. Online

### Daryl HuntGold Member

Joined:
Oct 22, 2014
Messages:
5,823
317
Trophy Points:
140
Ratings:
+1,578
I am working on a new project. I have been using in hub motors. I want to use a chain driven motor instead. Here is the problem.

The speed of the external motors are 4800 rpm
The available motor drive gears are from 9 to 13 teeth
The available shaft drive gears are from 32 to 89 teeth
The size of the Wheel (OD) is about 20 inch.

I am trying to keep the road speed down to no more than 37 mph. Is this possible in this range? Or am I going to blow well past that no matter what ratio I choose. My math isn't that good anymore.

2. Offline

### RambunctiousGold Member

Joined:
Jan 19, 2010
Messages:
19,728
3,611
Trophy Points:
280
Ratings:
+20,344
Sprocket Ratio Calculations

3. Offline

### tyroneweaverGold Member

Joined:
Mar 3, 2012
Messages:
16,747
2,504
Trophy Points:
280
Location:
Burley, Idaho
Ratings:
+11,665
Well. If a car has 4800 rpm and has 4:11 differential, what would be the road speed? 60??? Go from there.

4. Offline

### BULLDOGDiamond Member

Joined:
Jun 3, 2014
Messages:
49,072
5,770
Trophy Points:
1,830
Ratings:
+31,962
Try this.

a= motor RPM
b= drive gear teeth
c= driven gear teeth
d= wheel diameter

MPH= (a(b/c) * (3.14*(d/2)*(d/2)))/ 60/5280

5. Online

### Daryl HuntGold Member

Joined:
Oct 22, 2014
Messages:
5,823
317
Trophy Points:
140
Ratings:
+1,578
I came up with a motor sprocket of 8 teeth with an axle socket of 54 on a 20 in wheel at 4800 rpm at 35 mph. Please check my figure.

Title
Replies Views
Last Message

Replies:
730
Views:
7,136

Replies:
2
Views:
3

Replies:
88
Views:
272

Replies:
12,962
Views:
156,168

Replies:
45
Views:
59