Standard Motor Sizes and Impulses.
The numbers on a motor, eg C or K, equate to a certain 'class' of total impulse. The larger the letter, the larger the impulse or thrust.
| Total Impulse (Ns) |
Equivalent Motor Class |
| 0.00 - 1.25 |
½A ¼A |
| 1.26 - 2.50 |
A |
| 2.51 - 5.00 |
B |
| 5.01 - 10.00 |
C |
| 10.01 - 20.00 |
D |
| 20.01 - 40.00 |
E |
| 40.01 - 80.00 |
F |
| 80.01 - 160.00 |
G |
| 160.01 - 320.00 |
H |
| 320.01 - 640.00 |
I |
| 640.01 - 1280.00 |
J |
| 1,280.01 - 2,560.00 |
K |
| 2,560.01 - 5,120.00 |
L |
| 5,120.01 - 10,240.00 |
M |
| 10,240.01 - 20,480.00 |
N |
| 20,480.01 - 40,960.00 |
O |
There are a number of standard motor diameters, detailed below.
- 13mm
- 'Micro' Motors - mainly 1/2A
- 18mm
- The standard model size, catering for A, B and C motors, also some D class AP motors
- 24mm
- The larger model size, featuring C, D and E motors
- 29mm
- The transition size from model to HPR, featuring F, G, H motors. Also a common hybrid rocket motor diameter
- 38mm
- The most common mid/high power diameter, catering all the way from G to J
- 54mm
- The start of the larger HPR sizes, featuring J to L/M.
- 64mm
- An uncommon diameter, mainly occupied by hybrids.
- 75mm
- The large and expensive HPR solids and hybrids. K - N
- 98mm
- The most common size for large (>L) HPR motors.
- 150mm
- The realm of Cesaroni O class goodness