Gear Generator | Hacker News Reader

Gear Generator

geargenerator.com

150 pointsdanshapiro31 comments

I've created a lot of 3D printed gears over the last few years and one of the best tools I've found is from Rainer Hessmer.

http://hessmer.org/gears/InvoluteSpurGearBuilder.html

It allows you to specify additional parameters like backlash, clearance, and profile shift. It also allows you to output in DXF which tends to be more of a standard in the engineering world.

Looks fantastic, and was seriously fun to fiddle a bit with.

One bug though: you can't back out from the site, the history is flooded with geargenerator.com addresses. Had to close the tab (Firefox 40.0.3 on Windows).

> the history is flooded with geargenerator.com addresses

I'm seeing this a lot in apps these days. In many places I think it is intentional: where the entire state of the current view can be encoded in the URL it effectively gives you a "free" undo feature and can be quite useful (like when I'm playing with potential new running routes in Google maps).

Yes, and that can be useful. However, if you use the back button to return to a previous URL it doesn't appear to update the settings from the URL. This means you can't use the back button as an Undo button.

Agree - I'd much prefer an "undo/redo" button inside the app, instead of flooding my history state. They can change the URL all they want (for linkability) but leave my damn history alone!

The best part of this is that you can output the gears as SVGs. For example, gear + Glowforge = http://community.glowforge.com/t/gears/143/4

Wow, okay... that just happened. Instead of wanting a 3D printer, I now want one of these 3D laser printers.

Tested video gives a good overview... youtu.be/0R3mMUsHFvU

Need to see more reviews showing negative aspects. There's always negatives.

Edit: found a negative: shipping price. To Australia it's US$1380 for the model with air filter. That's crazy. Almost 2 grand Australian dollars for shipping.

Founder/CEO here (the guy in the Tested video). Happy to answer any questions! Shipping stinks - we don't make a penny on it; it's just expensive to send big boxes around the world.

Ok thanks. This thread was about the gear generator so I won't ask anything here. I'll go to glowforge.com if I need to know more.

This is majestic.

I've been battling with making my own gears in Modo for a while (the inbuilt primitive scales the teeth size as well as number of teeth)

However this allows me to create ratios AND test them at the same time. This is invaluable.

When I get time I shall be using this for my laser cuttings.

One thing I'm wondering about: do opposing gears always need to have the same form for the teeth? Also, what are the constraints that lead to the form of the teeth? I can imagine that one constraint is that the teeth must "roll" onto each other. But are there more constraints?

Opposing gears don't have the same form unless they have the same number of teeth. This isn't obvious when you look at the first gear pair, but look at the pair doing the 10:1 reduction. The teeth of the small gear are undercut quite a bit while the teeth on the big gear aren't undercut at all.

The only real constraint is that the teeth must roll into one another as you concluded.

The constraint is that the gears don't speed up and slow down (the gear ratio is constant). Also that the contact forces lie on a line.

There's a good animation on wikipedia:

https://en.wikipedia.org/wiki/Involute_gear

Involute gears are the only shape that satisfy those constraints.

Take a look at the "Ikona" non-involute gear form. The contact forces form a curve instead of a line, with zero backlash, and multiple tooth contacts before/after top dead center. Amazing:

http://www.ikona.ca/technologies_tooth.shtml

And the patents are about to expire...

EDIT: An application of the Ikona gear tooth form, implementing a CVT with no clutch plate or other frictional components:

http://www.powertransmission.com/issues/1008/ikona.pdf

There are other tooth forms that also satisfy the fundamental law of gearing (constant ratio of angular velocity). E.g. cycloid gearing used typically in mechanical clocks. The involute is popular because its easy to manufacture. It can be auto-generated on a gear hobbing machine- probably less important now with CNC machines, but very important in a pre-digital machine era. The involute is also less sensitive to gear center to center spacing.

Typically most real world gears vary in teeth shape. I mean among the gear pairs. Some are more pointy and some more round. What we see here is probably optimum teeth form.

I have done some calculations about them. But the manual I used was so vague about everything that I can't honestly say why and how for certain. My current understanding is that first you select gear ratio, then you get somewhat good nominal distance for the axels, and then you adjust teeth shape to accommodate all that.

The "rounded" design allows constant contact to be maintained between two gears. If they were of the simpler design with flat faces on the teeth, they would simply wear to this shape anyway, but in the process they would also end up with slack between them. A helical twist is also usually employed which improves the transition between adjacent teeth, and consequently reduces noise. Ever hear a transmission with a loud whine in reverse gear? IIRC, it's because they didn't use the helical twist trick on the reverse gear. I have no idea why they wouldn't though. If we're lucky, an ME will be along in a bit and explain all of this for us much better.

Yep. Straight cut gears are cheaper to make. Since people don't do as much reversing as going forward, it's probably a good compromise on cost vs comfort.

Makes sense to me.

This is probably THE best page explaining "rolling" of gear teeth: http://www-mdp.eng.cam.ac.uk/web/library/enginfo/textbooks_d...

Here s a referral link you can use to get 100$ off, im super stoked on this!! :) http://glowforge.com/referred/?kid=kmrbvD

Is that correct? The tip of the gear tooth seems to rub up against the other as it approaches. Shouldn't there be a small clearance there? or is there?

Also, is there a way to export to a format that can be loaded into SolveSpace?

Any clearance there would result in backlash. I suppose you need some to allow for manufacturing tolerance though.

That's fine, but when I first looked at it, it seemed like they were sliding. Now I see that it may be rolling as desired.

Sweet. Do you have an example of a planetary gear reduction?

Funny you should ask - I made a friend a laser cut model of his Prius transmission for his birthday.

Cutting it (on a pre-Glowforge laser): https://goo.gl/photos/pxJKDipWPtj6RXvZ7

Results: https://goo.gl/photos/NUivutAWsQe3GHfW8

Nice!

Neat. Now I want to be able to give the gears mass, and configure the "engine's" power output; and or maybe helical gear teeth.

This is amazing! Well done and thank you!

Very nice.

Very cool! The guys at http://romaxtech.com should take a look at this...

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