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1  General Category / 3d Printers Discussion / Hackaday Contest on: January 16, 2019, 03:26:59 PM
For those of you who haven't seen it:

https://hackaday.com/2019/01/16/new-contest-3d-printed-gears-pulleys-and-cams/

2  General Category / Gear Discussions / Re: Irregular Gears for Keplerian Motion on: January 15, 2019, 10:09:16 AM
...
I've also considere d some other ideas, like having a set of circular gears driven by the same input, connected to the output by a pre-tensioned drive shaft that would be able to cope with the varying position of the output gear but would keep enough tension to have it chase the input gear when it's at risk of coming unmeshed; the big problem with that is that it's pre-tensioned, so will only drive the gear in one direction, and will tend to pull the gears free if it's run back.
...

Any other thoughts or suggestio ns?  Problems with the solutions suggested?  Obvious solutions I've missed?  Other things that would make this kind of gear untenable?

You could look into a toothed belt-and-pulley system instead of gears.

Using helical or herring-bone gears may help with meshing issues and is pretty easy to do when you're 3D printing the gears.  You can also do more sophistic ated things to mess with the tooth form, though I'm not sure how much that can help in practice.

It seems like making a linkage that handles the orbits crossing each other is going to be a challenge .

3  General Category / Gear Discussions / Re: Gear tooth as a height map? on: April 19, 2018, 10:10:05 AM
It's occurred to me I've been accidenta lly cryptic in all of this -- what I'm trying (again, foolishly) to do is develop a way to create a crown gear or rack gear using an engraving laser.
...

The original post had me wondering whether you wanted a "polar" height map or "rectiline ar" height map.   This makes a lot more sense.
4  General Category / 3d Printers Discussion / Re: Which extruder head to buy? on: January 22, 2018, 12:03:29 PM
I am looking for some idea of which 3D print head to buy or build.
Drawings of a proven design would be awesome since I have the machines to make one from scratch.
If not drawings then a link to a head that works well and is durable would be appreciat ed.

I have a Prusa I3 Mk2 which works pretty well.

Here's an assembly drawing from Prusa:

http://manual.prusa3d.com/Guide/5.+Extruder+Assembly/114

Here's someone building & documenti ng a clone:

https://toms3d.org/2017/02/23/building-cheapest-possible-prusa-i3-mk2/

Depending on your applicati on this may not be appropria te, so YMMV and all that.
5  General Category / Gear Discussions / Re: Is There a Fundamental Difference Between Hypoid Gears and Worm Gears on: May 12, 2017, 10:30:06 PM
I'd like to see that printed.  Ever try shapeways .com?


... only took me 2 years to get around to it. :/
6  General Category / Gear Discussions / Re: Just fell over an interesting gear simulation maybe of interest to others. on: March 10, 2017, 10:16:48 AM
My first thoughts on this are to calculate based on pitch diameters (equivalen t to using un-toothed, smooth wheels) then look for a common factor for all the circumfer ences to decide on a tooth size. Iterate until the size/number of teeth is within machineab le limits.

You can get approxima te solutions that way.   For mathemati cally exact solutions you'd need to ensure that the tooth phase is rational, and that's not going to be possible with a numerical method like the one you describe.
7  General Category / Gear Discussions / Re: Just fell over an interesting gear simulation maybe of interest to others. on: March 08, 2017, 08:39:38 AM
So who won the $5  ...

Dunno.  You probably got your money's worth if you hadn't seen Oskar's channel before.

I'm still chewing on the math problem.
8  General Category / Gear Discussions / Re: Just fell over an interesting gear simulation maybe of interest to others. on: March 07, 2017, 12:33:45 AM
This video has more 'practical sense' to it.

https://www.youtube.com/watch?v=M_BUn4TDns8
9  General Category / Laser Stories / Re: New Notre Dame south facing stain glass window clock on: March 06, 2017, 11:13:04 AM
Art;

 Waterjet appears way too messy? 

They seem pretty OK on the mess side, but are more expensive to run than lasers.
10  General Category / Gear Discussions / Re: Just fell over an interesting gear simulation maybe of interest to others. on: March 06, 2017, 09:41:46 AM
...

By exact, I mean the pitch circles of the four gears are tangent and not slipping.
By non-trivial, I mean the four gears have four different radii, and the number of teeth is not zero or infinity.

https://www.youtube.com/watch?v=3iyO-OvIS_k

It's pretty easy to find exact solutions with 4 different sized planets.

It's not hard to work out that the centres of the planet gears are on an ellipse whose foci are the centres of the sun gear and the ring gear.   Working out the gear sizes can then be thought of as equivalen t to finding a particula r trig equation with enough 'co-rational' solutions, but I wasn't able to crack the 8 gear problem that way.    I'm not sure whether Oskar's friends have a different approach, or are just more sophistic ated than me in their knowledge of trig functions .
11  General Category / C Scripting - 101 / Re: G02,G03 convert to G01 on: February 24, 2017, 12:23:10 PM
If you're already parsing the G code and doing some kind of compensat ion on G01, it seems like it easiest way would be to also compensat e on the G02 and G03 calls as necessary .

12  General Category / Gear Discussions / Re: I would like to make a planetary gear with inner gears and center gear on: December 09, 2016, 03:59:59 PM
Yeah, that sort of thing inspired me, but I didn't get very far.

http://www.thingiverse.com/thing:88501/#comments
13  General Category / Gear Discussions / Re: Mating functional gears to circular gears on: October 28, 2016, 10:08:30 AM
...
Is there a way to calculate the pressure angle between circular and non-circular gears?

Let's assume that the teeth are very small, so that we can ignore the effect of the path of contact.

Let's also assume that the tooth meshing is as with involute gears with pressure angle phi.

Let r(theta) be a polar formula for the non-circular gear's pitch profile, centred on the axle for that gear.

Then the pressure angle (as Art would think of it) is going to be equal to:

arctan( dr/dtheta / r ) +/- phi

Where dr/dtheta is the derivativ e with respect to angle.
14  General Category / Gear Discussions / Re: Mating functional gears to circular gears on: October 27, 2016, 04:11:04 PM
...
Another way to ask about the pressure angle is how do I ensure the pressure angle will be less than 50 when mating circular and non-circular gears?

Can you make a drawing of what you mean  by pressure angle?  The notion is a little ambiguous when dealing with non-circular gears.

As far as I'm concerned, all the `rolling gears` in the attached pdf have the same pressure angle.
15  General Category / Gear Discussions / Re: Mating functional gears to circular gears on: October 27, 2016, 01:45:27 PM
Here's a video of a triangula r gear running: http://smg.photobucket.com/user/etfrench/media/Rose%20Engine/TriangleGear_001.mp4.html

...

Is there a way to calculate the pressure angle between circular and non-circular gears?

The video didn't work for me, but based on 'rose engine' it seems like you're looking for some kind of 'spirograp h lathe' thing.   Maybe something like the one at the start of this video:

https://www.youtube.com/watch?v=4XDIonkwTRo&t=30s

...

It seems like you're not that familiar with gear terminolo gy or theory.  The pressure angle is something that has to do with the shape and meshing propertie s of individua l teeth, and is not necessari ly determine d by the shape of the gear.  It can be a little tricky to measure.  Depending on your situation and applicati on it may be easier to make a complete set of gears than to measure the pressure angle of one.  Alternati vely, might also get satisfact ory results simply by getting close.


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