ArtF wrote:
there are a few rules to that... I used to build them by feel , but heres the rules.. Ill be adding a module eventually to
do this for you.
Art, if you ever get a chance to revisit this can you consider adding appropriate backing plates for the various combinations of stationary elements and make them 3D printable?
Art,
I used your formula which worked well for four planets but I cant get it to work with six.
Is there an update coming that calculates planetary gears?
I have an excel file with the formulas but I dont think i can upload it.
jbc
I got waylaid for a module for planetaries, but its still on my list. Cant say it will be soon, but lets
see if we can figure it out. Ill try here to do a 6 wheel and see how it goes..This will show the way
I think about the problem as I try to solve it..
Lets try an example..using some intuition ( guessing :) ) on the numbers
First, (Za + Zc)/6 must be an integer. SO lets find some that fit
Lets pick a ZC + Za thats arbitrarily a multiple of number 6.. lets say 60 times just to be symetrical.
so Za + Zc will be 60 * 6.. 360; sounds round..
So this follows the rule#2, Za + Zc / 6 = integer.. 360 / 6 = 60;
So lets check rule #1 to figure out Zb, just to go backwards. Would be Zc = Za + 2ZB , Za must be less than Zc, far less, so lets pick 300 and 60 and try that..
Lets check
Rule #3 = (Za + Zc * AD )/ 180 must be an integer.. so 300 + 60 * 30 / 180 = 60..good so far.
So we have Zc = 300; Za = 60, and 300 = 60 + 2*zb .. Zb = 120.. seems good so far.
Lets try that one..
( Pause while I run Gearotic.. )
Nope, wont work. The Zb's are too large to fit 6 of them.. we seem to be missing a rule
on a ratio of Zb to Zc.. but the rules were kinda general. Knowing the Zb is too large though
from a trial we can try to shrink Zb while increasing Za.. this makes intuitive sense, since the Zb's were
too large, lets shrink them,, implying then we increase Za..
so..from the first try..
Zc + Za = 360; we had 300 and 60, lets drop that to a tighter ratio, the closer Za is to Zc, the more planetaries would fit logically.. so lets see if we can find a better combination..
how about 240 and 120, much closer and still seems 6ish.. ( When trying to place 6 gears, think 6ish, if 8 think 8ish..)
Zc ( 240) = Za(120) + 2Zb == Zb = 60; ( note is all 6ish in multiples..)
So Zc = 240, Zb = 60 and Zc = 120;
Rule#3 (( Za + Zc ) * 30) / 180 = 60..so we're ok there too..
So lets try building that one just to check it..
(Pause while I run Gearotic again.. :) )
Ahh, there we go. Here is the project with this gear count.. 6 planets in the ring..
Hope it helps, its just how I tend to face this type of multiple unknowns problem..
I want to make a planetary gear with 16 teeth sun gear and 72 teeth internal ring gear, 0.5 module.
This gives me the diameters that I need.
How do I work out the diameter of the planet gears ?
Would you make a simple You-tube video showing how to place the gears into the project screen
and how to find the centre measurement of the shafts ?
Thanks Art.
That helped.....so simple once you've done it once.
Making the Ring and Sun gear divisible by six worked like a champ, which with your equations made the pinion for me.
After I made the excel file I saw you placed a zip file on the post lol.
Thanks again.
When you get to the planetary module I'd like to add something to the wish list;
Planetary gears with herringbone and/or helical teeth options.
Davarch,
If you sketch out your gears, you'll see that the diameter of the planetary gear is equal to the radius (half the diameter) of the ring gear minus the radius (half the diameter) of the sun gear:
P = R/2 - S/2
Since the number of teeth around the circumference of gears with the same module is proportional to the diameters of those gears, you can use the tooth count to get the size of your planetary gear:
P = 72/2 - 16/2 = 28
It's nice that you wound up with a whole number of teeth -- You must have a plan!
I'm no expert at Gearotic, but I attached a gth...
--Justin
Attachments
[The extension has been deactivated and can no longer be displayed.]
Art.
I found a guy who made an app that lets you make a customized planetary 3D file for 3D printing.
Take a look at his code. Could make your job easier....or not.
Hope it does;
I hadn't seen that one...WOW.
BUT, if you look below the picture of the thing, there is an 'App' button that will take you to the app that creates the planetary gear set which lets you customize it.
I found the gears I made with it were touching. I didn't read ALL of the instructions so will need to go back and see what rule I missed. But I spent a day on that rabbit hole and had to move on.
I will be back tho ;D
Here's another, more elaborate, one. I might just try to print one. Might even try both...
You can also (with a desktop browser) use "Open in Customizer" over on the right side of the page, under "Thing Apps Enabled". I prefer not creating a public object since they make TV even harder to search
JustinO wrote:
Davarch,
If you sketch out your gears, you'll see that the diameter of the planetary gear is equal to the radius (half the diameter) of the ring gear minus the radius (half the diameter) of the sun gear:
P = R/2 - S/2
Since the number of teeth around the circumference of gears with the same module is proportional to the diameters of those gears, you can use the tooth count to get the size of your planetary gear:
P = 72/2 - 16/2 = 28
It's nice that you wound up with a whole number of teeth -- You must have a plan!
I'm no expert at Gearotic, but I attached a gth...
--Justin
=======================
Thanks for your reply Justin !
I cannot open your .gth file, whatever that is, but I finally sussed out how to drag the planet gear
to the correct position in the Project window, positioning it between the ring gear and the sun gear.
This fitted correctly, and showed me that the planet gear is the same size and number of teeth as the sun gear.
I have 3D printed them and they all run together well, after a little bit of size tweaking.
