Advanced gear gadget

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Advanced gear gadget

Postby FixitMike » Sat Dec 12, 2015 9:21 pm

I would like to see a gear gadget with the following features:

1. The ability to draw gears with a full radius root. The existing gadget draws the space between the teeth with sharp corners. I don't believe there are any router bits that can produce a sharp inside corner. A full radius root maximizes the bit diameter that can be used.
2. The ability to specify the addendum, dedendum, pressure angle, and backlash. These are all parameters that are useful for designing gears.
3. A help document with information about each parameter to help novices.
4. The ability to draw a rack with a specified number of teeth. (With a full radius root, of course.)

My gear construction method at viewtopic.php?t=21084 can show some of what I mean. I don't know how to program gadgets, but would be willing to help anyone who is wants to tackle the project.
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Re: Advanced gear gadget

Postby PaulRowntree » Sun Dec 13, 2015 4:02 am

Interesting Mike. I've never cut a gear, nor used the gadget, so be patient .... If the full root radius is the important improvement, would it be easier to just add some short radius cuts from the bottom of the gadget's valley in towards the centre, by one tool radius? Is there no BL allowance on the gadget's vectors? Could this be done by offseting the vectors inward by a fraction of BLA ?
Cheers!
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Re: Advanced gear gadget

Postby George B. » Sun Dec 13, 2015 5:37 am

There is site that sells a homemade gear software for $26
http://woodgears.ca/
At web site go to "gear template generator (new version); then page down to "gear generator program".
I brought the software and have attached a gear that I exported the dxf file from and opened it in aspire. This maybe something you are looking for.
gear12-12-15.crv3d
(235.5 KiB) Downloaded 185 times

This is my first forum post.
This web site also has very enjoyable videos on many things including woodworking although he is kind of against CNCs. Great inventor.
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Re: Advanced gear gadget

Postby FixitMike » Sun Dec 13, 2015 8:30 am

PaulRowntree wrote:Interesting Mike. I've never cut a gear, nor used the gadget, so be patient .... If the full root radius is the important improvement, would it be easier to just add some short radius cuts from the bottom of the gadget's valley in towards the centre, by one tool radius? Is there no BL allowance on the gadget's vectors? Could this be done by offseting the vectors inward by a fraction of BLA ?
Cheers!

The gear gadget appears to draw the lower part of the dedendum part of the tooth outline as a straight radial line. The involute curve needs to be continued down to the dedendum to be accurate. As drawn, the straight lines may result in tip interference when the gear is running with another gear. One could draw a half circle between the ends of the dedendum lines for a full radius root, but it would not be particularly accurate. Drawing short radius cuts by one tool radius means you have to know the tool radius before you calculate the gear.

The backlash allowance can be added by offsetting the vectors inward, but you loose some of the outside diameter of the gear by doing so.

My thread for constructing a gear includes a file that shows my method of construction. It meets all of the objections I have about the Gear gadget and can be modified for changes in the gear parameters. I just don't have the knowledge to put it into a Gadget.

The attached file and picture show two 4" pitch diameter gears drawn by the gear maker gadget, on 4" centers. If you look closely at where they mate, you can see that there is interference between some of the teeth. They will not run smoothly.
gear example.crv
(131.5 KiB) Downloaded 125 times
gear mesh.JPG
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Re: Advanced gear gadget

Postby FixitMike » Sun Dec 13, 2015 8:47 am

George B. wrote:There is site that sells a homemade gear software for $26
http://woodgears.ca/
At web site go to "gear template generator (new version); then page down to "gear generator program".
I brought the software and have attached a gear that I exported the dxf file from and opened it in aspire. This maybe something you are looking for.


That is a useful site. However, if you look closely at the gear template, you will see that the gear has sharp inside corners which cannot be cut on a CNC router. There is no provision for backlash. Also note that in the example picture, the ends of the teeth touch the bottom of the space between the teeth of the mating gear. The will prevent smooth operation.
Gear Capture.JPG

I noticed in his section on plywood gears, he drills a hole at the root of each tooth before sawing. This way the profile ends up with a full radius, even though the template wasn't drawn that way.
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Re: Advanced gear gadget

Postby PaulRowntree » Sun Dec 13, 2015 6:24 pm

Mike, I have been looking at your Word description, thanks again, it is very clear, and could be easily coded.

1) The point 'A' : is it co-incidentally landing on the inner circle in the example ? EDIT : must be a coincidence, because inner circle radius is variable with RRD.
2) Is the tooth design exactly correct as described, or is it as close as you can get with the Vectric drawing tools? Once it is being coded up, it could follow the exact shape required.
3) To make a rack, would you just replace the three radial lines that meet the pitch diameter (Step 2) with three parallel and vertical lines, descending from the pitch 'height'?

Last question : why are so many people wanting to make DIY gears? They can't all be clock designers.

Cheers!
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Re: Advanced gear gadget

Postby FixitMike » Sun Dec 13, 2015 7:10 pm

1) The location of point A is strictly a coincidence.
2) The tooth contour in my method is drawn as an arc, whereas to be exact it should be an involute, which is much more complicated to draw. I don't feel the difference is significant for wood gears.
3) For a rack drawing, see my post at viewtopic.php?f=48&t=20899&p=148038&hilit=rack#p148041

Last Answer: I don't think that the problem is how many clock makers there are, the problem is the lack of gear drawing instructions suitable for cutting on a CNC router. I'm using my method to draw the gears for the Frankenswitch. viewtopic.php?f=5&t=23837
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Re: Advanced gear gadget

Postby GeneMpls » Sun Dec 13, 2015 7:39 pm

PaulRowntree wrote:M
Last question : why are so many people wanting to make DIY gears? They can't all be clock designers.

Cheers!


Clearly the Steampunk movement is an element?
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Re: Advanced gear gadget

Postby graffix11 » Sun Dec 27, 2015 10:26 pm

Also a internal gear option for making planetary gears would be great.
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