planetary gear design

[Mark Rogerson]

Well it took me all weekend, but I've got the preliminary solid models and movies completed. Attached are: 

MATLAB code to find design parameters

movies of climbing mode normal wheeling mode

solidworks files 

 I found the parameters for the gears by assuming:  

a pitch angle of 20 degrees (which is common in the industry)

pitch circle of interior gear is 6" (based on size restriction which needs to be compact)

I also wrote a matlab code which spits out all needed design parameters (and then some) based on the two above assumptions. This way if one of our needs changes we can easily get parameters we need. I think down the line we may come across some sort of speed ratio design constraint and if so I'll rewrite the code as necessary and recreate the solid model. 

The next step for this is to create the crank which will be attached to the wheels.

[Mark Rogerson]

Here is the final Gear parameters

Diametrical Pitch for all gears = 20in^-1

Planetary Gear Parameters:

N_sun = N1 = 24

d_sun = d1 = 1.2"

N_planet = N3 = 48

d_planet = d3 = 2.4"

N_ring_gear = N4 = 120

d_ring_gear = d4 = 6"

C13 = 1.8"

C34 = 1.8"

Spiral Bevel Gear Parameters:

N_bevel_pinion = 30 (left handed)

d_bevel_pinion = 1.5"

N_bevel_gear = 30 (right handed)

d_bevel_gear = 1.5"

[Mark Rogerson]

here is the updated assembly and part files. the motor is running at 10RPM and its motion can be seen in the movie called "torque to wheels" and in motion study two of the assembly - (I hope it uploads this time)

[Mark Rogerson]

[Mark Rogerson]

Here is the scaled wheel carrier and assembly.This is just to make sure the carrier is the right size. I still haven't added the holders for the bevel gears. Let's just make sure the dimensions work first then I can add the rest of the features.

[Mark Rogerson]

This is the latest iteration of the CAD model. The difference the wheel carrier has been scaled down to climb one stair at a time. The length of the shaft which connects the bevel gears has been shortened to accompany the wheel carrier's smaller size. The ring gear was very close to the stairs, so the wheels were made to have a 10 inch diameter instead of 8". The next iteration will be to account for all the necessary ball or thrust bearings needed so we can start to manufacture! 

If you'd like to play with the wheel diameter to see how it works with the stairs:

1. first open the part called "wheel"

2. adjust the sketch called "diameter"

3. Open the folder labeled "assembly with scaled wheel carrier"

4. Adjust the mates labeled "WHEEL MATE1" "WHEEL MATE2" and "WHEEL MATE3" to the new radius of the wheel

 

[Mark Rogerson]

Hey guys,

Add this file to the folder to open the assembly. I had to work late, sorry I couldn't post it sooner! Also I think the stairs may be hidden, so in the design tree just right click on "stairs" and click "show components"