Drawing Gears in SW 2005

I'm modeling a clock in Solidworks 2005. I don't need a stinkin' CAD program to design the clock, but talking to the waterjet at work might not work as well as feeding it DXF files...

So how do you guys draw simple involute profile gears in Solidworks? I've already read Machinery's Handbook, searched online, and searched this forum. At one point I got pissed, sat down with my calculator, and manually drew an involute curve using a bunch of "for construction" centerlines and the spline tool to interpolate the curve betweent he laid out points. That worked, but it wasn't exactly an ANSI standard tooth profile, and I don't have the patience to do that for multiple gears.

Is it possible to take a gear someone else made and mess with the equation set to change the parameters? hell, I don't even know how to input equations.

Can't help with SW, sorry, but if you go here:-

http://www.hobbing.com/

You can download the accurate shape of virtually any gear and import it.

John S.

Halcohead:
Why are you using involute gears? Clocks and watches traditionally use the cycloidal form of gearing. Cycloidal gearing is a lot easier to lay out. A book that would show you how to do it is Wheel and Pinion Cutting in Horology by Malcolm Wild (ISBN 1 86126 245 0)

John, that's a great link, thanks!

cheers,
Michael

I'm using involute gears because thats a gear form that comes up more often in machine design. This clock is partly for fun, and partly to actually teach myself some CAD proficiency. I have yet to see anything other than a bike and a clock that use cycloidal gearing.

Ironically, I'm actually familiar with the math that describes both involute and cycloidal gearing, so I know how to lay them out by hand, just not in a computer.

John, does that program need autoCAD to run? I downloaded four different programs, and for some reason all of them unexpectedly quit before I even got the opportunity to input parameters for the gear.

I cheat and download them from Rush Gear.
http://www.rushgear.com/

Halcohead,

make your blank sketch, extrude to thickness,
select end face, sketch in tooth space, extrude cut.


add an axis, select tooth space, copy number of times, select the axis, high lights, looks ok, zap!


Tarahhh! hope thats enough data as you know how to calculate points, I do mine with Quattro pro spread sheet.

Gearshaft:


another:


Cheers Les H.

Les, that is helpful, but the way I'm laying out points is completely different (and far inferior) to yours. The way I laid out the curve way by first sketching a bunch of radial "for construction" lines that stopped at the base circle. These lines were laid out every two degrees. I think I did ten. Then I used my calculator to calculate how long each line coming off of these had to be (pretty simple, if a bit repetitive). Then I used the spline tool to interpolate a curve between the ends of the second set of lines. I did end up with a good approximation of an involute tooth profile, but setting tooth thickness, addendum, and dedendum was rather arbitrary.

Do you think you could explain how you figured out the tooth point layout? I'm decent at working inside the solidworks program, but I still don't know how to do things like import spreadsheets or even lay out a series of points calculated on a spreadsheet. Heck, calculating the points in the spreadsheet isn't immediately obvious, simply because I have an equation that willt ell me what they are.

Halcohead

I have a lot of gear books,was at it from feb 1958 thru sept 1993. The book that turned on the lights of the Involute was:


All functions of Involutometry & Trigonometry are displayed accross two pages and are listed for every one hundreth of a degree.This is in fact a co-ordinate chart for an involute of unit one!
If You come across one recomend you get it, no Idea why it's not republished. Undercut teeth all explained!




During my Geargrinding years in the job shop environment, inexpensive short cuts, lead to a radius dresser that approximated the involute within say 60% of the involute tolerance band of the gear to be ground.
So, if points at the base dia or root dia, pitch dia, and outside dia are calculated and a three point arc is swung through them, involute is zero at those points, between the base or root dia and the pitch dia, the radius is too large, flattening it out or minus on the curve, between the pitch dia and the Outside dia the radius is too small, plus stock on, this gives an elongated "S" shape to the involute chart when inspected, if its within tolerance of the class of gear run, Your home free.

With the advent of caculators and PC computers, n/c machining, mills and wire edm; with five points, a three point arc thru 1,2,&3; then a second arc thru 3, 4, & 5, the error on say 35 teeth and up is hard to chart within a tenth, on lower numbers the error increases, so more points, 123, 345, 567, 789, a template style dresser on a $20,000 surface grinder, beats out the BIG BOYS with their $330,000 CNC gear grinder.

So I use one three point arc for 35 and up, less teeth additional arcs it comes out more accurate than a series of flats, you are useing the Radius, Vector approach, I use x,y points, 3 point arc thru them, low number of teeth two sets does most gears.

On Low numbers of teeth, the root dia will be below the Base dia, [1] extend the arc to the root dia & fillet with a .30/diametral pitch radius, or [2] a straight line tan to last point on base dia to 0,0 center of gear, trim with fillet rad as above.

Spread sheets, I do Quatro Pro, early days, less keystrokes, also it would read any format, The old Supercalc, lotus 123, excell, and I did not have to put my discs in everytime I wanted to run, treated me as a customer not a criminal, Lotus 123 cost me a bunch, and demanded i put in my disc each time, Quatro $79.00 first time out, ate lotus and excell for lunch.





tooth thining or thickening a backlash value is put in, to thicken enlarged pinnions a negative value is put in.

More later,
Les H.

Halcohead,
SW GEARS round two:
x-y points are in columns K & L.



I do half space at 90deg, [12 o'clock] then mirror, extend curve past outside dia of blank, close up in order to extrude cut.


as posted before,






Cheers Les H.

Les- thanks for the detail- I have been "cheating by using a single radius tangent to the base circle and through the pitch diameter. It's interesting that your 3 point arc method comes out so accurate when you check the involute. How did you make your templates for the profile dresser?
I recall in an old post of yours that you make reference to Cima Hobbers- I have two in our shop-
both P5- wish I could find another one!

Thanks,Dan

Dan from Oakland

(How did you make your templates for the profile dresser?).

Initially CNC Mill, plotting points into Generic Cadd. By late 80’s gave drawing and detail dimensions & sent out to wire EDM, following the purchase of GARNER Universal wheel dresser, they supplied the first template to my dimensions.

On Lower numbers of teeth, today I would use two or three arcs as opposed to a spline, which are I believe come out as a series of flats; the involute is an ever increasing radial arc, and so a series of arcs gives a better approximation.
As each point is calculated to be on the involute, when charted the portion in between each point will appear as an elongated “S” , plus at the top, minus below.
So for two arcs you would get a chart of;

“S”
“S”
the bottom of the upper “S” being the same point as top of the lower “S”. The magnitude of error on the "S" a tenth or less.





Internal gears ground with wheel dressed with Garner Template dresser.


A surface grinder modified for Gear grinding.


CHEEMA (CIMA) P5's, damn fine machine, (You want a 43 tooth Worm gear to fit a 1920's Ice Machine?)
No Problemo, fly cutter in hob spindle, tangental feed, takes a while, but then you don't have to wait for a worm hob, Was 13 weeks, what do they run these days? Also How much?

Cheers Les H.

Les - how on earth do you grind the inside of a gear that small? Do you have a photo of the spindle and wheel setup?

For a company to release a diagram with the word "meonite" is really embarrassing...

Such a fine product, but such a poor proofreader.

Three point arcs thru involute points, templates con’t, & Garner Dresser.
Internal grinding attachments.


QUOTES:

Les- thanks for the detail- I have been "cheating by using a single radius tangent to the base circle and through the pitch diameter. It's interesting that your 3 point arc method comes out so accurate when you check the involute. How did you make your templates for the profile dresser?
I recall in an old post of yours that you make reference to Cima Hobbers- I have two in our shop-
both P5- wish I could find another one!

Thanks, Dan

Mudflap:

Les - how on earth do you grind the inside of a gear that small? Do you have a photo of the spindle and wheel setup?

DAN:

Found some charts in my notes. When setting up on a form grinder don’t grind all the teeth, clean one up see what’s what, leaving it on the grind arbor, correction, grind another tooth space, closer, correct and. YES THAT IS A TEN MILLIONTHS CHART ON THE END. The gear is within fifty millionths. Note the “s” between points.There were seven control Dia's and a controlled tip break, 32T,16DP,20deg PA, 3 point arcs between 123, 345, 567, and a calculated fudge for the tip.


NEW TEMPLATE, for the second or third machine that was built, note roughness on form from wire EDM, then after Hard "ARKANSAS STONE" stoning of the form. This is a standard 0.0002" ITW Chart.As you can see it is well within .0002" form. 28Tooth,9 DP, 25deg PA.


Mudflap:
Sorry was so busy back then Never took pictures of #2 & #3 machines, browsed my notes and found this stuff:

I didn’t know any better! Actually new wheel was 2 ¾” dia, had them made.The internal gear is a 28Tooth,9 DP, 25deg PA.

Initial concept:


Wheel spindle concept:


Needed lots of bearings, they will & did wear out in a month, Two shifts.

Attachment driven from main spindle. Spindle adapter, early version, finished up with two 3/16” wide Kevlar toothed belts.


THIS DROVE IT ALL!


For The Hobby Guy’s, single tooth cutter, need a good swinging radius attachment, that can set the radius within half a thou or even the nearest thou.
Mounted in a boring head .060” offset, better yet make an eccentric holder for the cutter, It will not move around as much.


Cheers All, Les H.

failsafe7
303 Stainless
Member # 8843

posted July 13, 2007 03:18 PM
--------------------------------------------------------------------------------
For a company to release a diagram with the word "meonite" is really embarrassing...

Such a fine product, but such a poor proofreader.

OOPS! Never noticed that one.



Cheers,
Les H.

No need to apologize... Not your mistake, was it?

Sorry to be such a turd. I was just making obtuse observations.

I recall in an old post of yours that you make reference to Cima Hobbers- I have two in our shop-
both P5- wish I could find another one!

Thanks,Dan

Click to expand...

Came across this on another thread today.

CIMA P5 A01

http://cgi.ebay.com/Cima-P5-Machine-Set-Gears-Arbors-Good-Condition_W0QQitemZ200128633041QQihZ010QQcategoryZ92083QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Cheers, Les H.

Thanks for the pics Les, nice solution.

So how do you guys draw simple involute profile gears in Solidworks?

Click to expand...

GearTrax.

Download a 10-trial here for free if you're a registered SW user:

http://www.camnetics.com/gtsw.htm