Greenpower

Gearing calculator

Wheel dia inches			10 (Over inflated tyre)
Speed	Ratio		Drive	Driven	Drive	Driven	Drive	Driven	Drive	Driven
mph			Teeth	Teeth	Teeth	Teeth	Teeth	Teeth	Teeth	Teeth
15	3.97		11	44	12	48	13	52	14	56
20	2.98		11	33	12	36	13	39	14	42
25	2.38		11	26	12	29	13	31	14	33
28	2.13		11	23	12	26	13	28	14	30
30	1.98		11	22	12	24	13	26	14	28
35	1.70		11	19	12	20	13	22	14	24
40	1.49		11	16	12	18	13	19	14	21
Wheel dia		12
15	4.76		11	52	12	57	13	62	14	67
20	3.57		11	39	12	43	13	46	14	50
25	2.86		11	31	12	34	13	37	14	40
28	2.55		11	28	12	31	13	33	14	36
30	2.38		11	26	12	29	13	31	14	33
35	2.04		11	22	12	24	13	27	14	29
40	1.79		11	20	12	21	13	23	14	25
Wheel dia		16
15	6.35		11	70	12	76	13	83	14	89
20	4.76		11	52	12	57	13	62	14	67
25	3.81		11	42	12	46	13	50	14	53
28	3.40		11	37	12	41	13	44	14	48
30	3.17		11	35	12	38	13	41	14	44
35	2.72		11	30	12	33	13	35	14	38
40	2.38		11	26	12	29	13	31	14	33
Wheel dia		20
15	7.93		11	87	12	95	13	103	14	111
20	5.95		11	65	12	71	13	77	14	83
25	4.76		11	52	12	57	13	62	14	67
28	4.25		11	47	12	51	13	55	14	60
30	3.97		11	44	12	48	13	52	14	56
35	3.40		11	37	12	41	13	44	14	48
40	2.98		11	33	12	36	13	39	14	42

Explanation

Greenpower 'Ready Reckoner' for Gearing.
(Motor Speed of 2000rpm)
25mph is our recommended initial design speed.

These ratios can be used for chain drive, toothed belt drive or simple pulley arrangements. We have shown a recommended starting design point. The 'drive' gear details are typical and do not preclude the using of other sized cogs. It is up to the individual teams to work around this to see what speed the car performs best at. Remember that it is imperative that the motor rotates as near to 2000 rpm as possible for maximum battery and motor life. Do not over stress the motor by trying to go too fast as it will expire!