Also, bevel gears have the teeth on the back side in the project viewer (also in 3.002), and the teeth face down in the stl file.  Is this normal?

Kirk

I tried an XL gear, It looks like ratchet teeth here, on my XP machine.  When increasin g the # of teeth it gets really weird at 42T, kinda like a ball of yarn with inverted triangles sticking out.

Kirk

Greg - do you mean you're trying to get the center hub diameter larger - more material between the spoke cutouts and the shaft?  The rim ratio will also make the center hub bigger.

I've had trouble with spoked gears breaking at the hub because there just wasn't enough plywood between the spoke cutout and the shaft.

Kirk

Change the diametral pitch (the d-pitch box in the program).  The formula for outside diameter is (teeth+2)/diameter, which gives 5.875 for an outside diameter of 8.0".

You can google diametral pitch calculato r for a starting point.  I'm reading an out-of-copyright book online at http://www.archive.org/details/treatiseongearwh00granrich .  Or you can see if your local library has a copy of Machinery's Handbook and look at the gear, splines, and cams chapter.  It's been in print since 1914 (it's up to the 28th or 29th edition) and there's out-of-copyright editions online.

Good Luck!

Kirk

I hope it's OK to post this, no connectio n except being a customer.  I've had good luck with this source for 1/8" shank mini endmills; just placed an order today for plastic cutting bits.  Flat rate shipping (might need to ask for invoice).  Check out his bargain bin, bits for $1 apiece.

http://stores.ebay.com/CARBIDE-PLUS

Kirk

For the stl file, same steps through placing both gears from a clean program start.  180* this time.  No wire frame.

Click output manager, then select only 3D stl
Name project Bevel2, click OK
Thinks a bit, then back to project screen.
This time bevel2 has an stl file, 9.5 MB.

Weird.  I believe before I'd always selected both gcode and stl.

Deleted all the files from GearData\Bevel2

Back to still open GM, click output manager, select 2.5D gcode and .stl file, click create output, wait a bit.
This time has both tap and stl files.

I restarted GM and tried the 13T 1.5" gear with no stl file from last night (created from scratch, just the wheel added to the project), got an stl file this time.

Restartin g GM, then loading the project file from yesterday, then going to the output manager and selecting only .stl gives a 4.8M stl file.

The only differenc e from the last try was installin g W7 SP1.  I'll dig out the W7 notebook that I take to work and see if it'll make an stl without SP1.  You can disregard this one.  I'll try cutting the stl after I make another blank.

Kirk

Maybe it's just me...

On 32b W7Pro SP1,  amd 620 quad core, 4.0GB (2.87 usable<sigh>), 3.002 downloade d and updated early this morning, and licensed.  It's been updated regularly since I bought it.  Here's what I did:

Start GM
Click spur gears tab
Click Bevel, leave at straight and 90* shaft
Change DP to 10.0, wheel to 28t, pinion to 13 (trying to get 3.0 and 1.5" gear diameters).  Spokes at 4 straight, 33% leg and rim ratios (how it came up)
Click create wheel, then OK to create solid gear.  Gear appears in project screen
back to spur tab
click create pinion, OK to create gear, click on screen
place at 180* (whoops, missed, 177* this time)
Rotate.  Things move as expected (although the default is the teeth point away from the viewer in ISO mode)
Click solid/wire.  Gears switch to wireframe .
Click rotate.  Gears switch to both 13t, otherwise same position, and start turning.
Click solid, back to original size
Rotate, back to both 13t.

Solid/wire switches back to specified sizes, rotate on/off, ccw step, cw step back to 13t.

attached is a dir listing of c:\Gearotic Motion.  If you'd like I can email you all the files; (suspect you wouldn't like the license file posted), just in case it's an old file hanging around that the installer missed.  Let me know if you need a file listing from anyplace else.

I'll try creating a .stl file and post separatel y.

And, just so the gentle readers don't get the wrong idea, this is an obscure bug in a beta version of a great product that I'd buy again without hesitatio n.

Kirk

It's repeatabl e, and after a reboot.  This time it made two copies of the smaller pinion gear rather than the bigger wheel.  This machine is a single-core Intel Atom nettop with 2GB, and has been very stable.  Leaving it in wire frame will cause the same problem, and trying to save the project file will also crash GM.  It might be somehow related to demo mode.

I meant to try wire frame on my 32 bit W7Pro amd quad-core, but forgot.  This machine will not generate .stl files, either.  Generated 2.5D gcode will cut a regular spur gear, didn't really expect 3D bevel cutting, but was hopeful.  There were no error messages, just the spur gear gcode.  I cut the gear, 1.5" diameter, 10.0 DP, 14 (iirc) teeth, and a 1/16" endmill.  It looked fine on the viewer, and good on the router until it came lose from my improvise d fixture (darn) and got a bit chewed up.  Guess I need to figure out how to hold down a round hdpe disk while the edges are being cut.

I'll give it a try under XP mode and see if that makes any differenc e with the stl files - W7Pro's XP mode is a licensed copy of XP in a virtual machine, not just a compatibi lity mode and should give the same results as XP on the same hardware.   I'll also try wire/solid and see if it's strange there.

Kirk

I did some experimen ting, this time under WinXP, creating a pair of bevel gears, 10DP, 28t wheel, 14t pinion, 90* shaft angle, then added both to the project.  If the solid/wire button is clicked, then clicked again, then rotate turned on, the pinion becomes the same size as the wheel.  The shaft position remains the same, and the gears no longer meet.  Click solid/wire twice they'll come back to normal, then the pinion expands again if rotate is clicked.   Texturing is turned off.

I didn't install the key file on this machine, so I can't tell if stl file output works (got the error message).  When I tried to close the output window GM hung, then crashed.

I hope to try to make a bevel gear on my "official" cnc PC (W7Pro) tonight - I got a box of 1 to 3 inch round HDPE and delrin cutoffs off ebay, made a couple blanks with the Unimat, and will see if I can turn them into a gear or two.  Just have to finish the tool position laser installat ion (thanks Tweakie!) first. 

Kirk

Works OK for me on a W7 (upgraded from Vista) notebook and 3.002.  Makes a 29K line gcode file, but no way to view or test at work.  No .stl file, but that might not be working yet.

If I remember I'll try on W7 Pro about Wednesday when I get back home.

Kirk

You can read it online, too.  It's got a great quote:

"It is not necessary that the student, especiall y if he is a workman, should
learn all that is taught in this book, for it contains much that is not only difficult
but also of minor practical importanc e."

Kirk

If you don't want the dead tree version there's downloads in multiple formats (it's legal, the book is out of copyright) at:

http://www.archive.org/details/treatiseongearwh00granrich

While ebooks aren't as nice as the real thing they take up less room on the overfull shelves and make the spouse happier - and there's more room to display gear projects.

I really like my Kindle. 

Kirk

This is on a slow Atom nettop with XP, in demo mode.

On elliptica l gears the only spokes are very narrow.  Leg ratio doesn't work, rim ratio doesn't initially . After switching from straight to curved to straight rim ratio started working, leg ratio didn't.  They work in curved.  When restartin g the program spokes defaulted to curved, when switching to straight rim and leg ratios worked.  Interesti ngly, after the restart Spur gears defaulted to curved, elliptica l's to straight, the leg ratio problem still existed.  Spur gears spoking options seem to work OK both straight and curved.

IMHO, the separate spoke panel (not part of the gear design screen) seems awkward.  It disappear s after turning spokes on or off and when switching from straight to curved, and the tab has to be selected again.  Hitting enter does the same.  Ratios higher than 100 work, but only after pressing enter and losing the tab.

Kirk

Thanks to all; many possibili ties.  The 90 degree gear motors look ideal, maybe with some extra gearing to slow them down a bit, tableboar d with slots to adjust center distances, maybe a magnetic friction clutch...

The controlle r and USB to servo stuff from Pololu is pretty fascinati ng - and cheap.  The stepper and servo controlle rs might work well with the stack of $4.30 microcont rollers I got from TI (like a gear mill angle adjuster), if only there was something left in the spare time bin.  Kid in a toy store syndrome<sigh>.

Seems like just yesterday that going to 1K bit ram chips was a big deal, 24" square boards for a whopping 64K bytes, don't slam the door or the loose pins are a bear to find.  Now the $1 microcont rollers way outdo our then jaw dropping performan ce communica tions minicompu ters, and gigabyte ram costs less than $10.  Moore's Law at work.

Dan:  Thanks!  Never thought of Micromark - it's not the 7x16 minilathe I want, but it's an excuse to order something from them.  I dug some more with google (toy gear motors) and found some at http://www.solarbotics.com/motors_accessories/gear_motors/ .  Keep the micromark for myself, and use the solarboti cs ones for give-aways, maybe.  How noisy are the micromark motors?

Tweakie:  Will the result include a laser   You got me started looking at small lasers, like the 1 watters from Turkey - there's too much old farm equipment here that need gaskets made, and lasers would be a lot more fun than hammer-on-them gasket cutters.   My xacto knife skills aren't as good as they should be, although the last thing I need is yet another project.  Even laserless I'll be looking forwards to the result.