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Is there room for a new gear tooth standard?

TomD.inPDX
17-Peridot

Is there room for a new gear tooth standard?

I am posting this in the FIRST section only because I am proposing a simplification for FIRST teams to develop gears that are highly functional and super easy to define.  By no means am I proposing to replace established gear manufacturing methods.  I specifically propose this variation due to the advent of rapid prototyping technology where tooling and conventional manufacturing methods require no consideration.

There are few advantages to the proposed Round Tooth^tm method.

  1. The tooth is inherently stronger since they have no undercut requirements.
  2. Manual meshing of teeth is nearly foolproof.
  3. Common conventions can be used for defining tooth profiles.
  4. Parametric relations can generate any spur/ pinion/ring gear and spline pair with ease.
  5. Spline drives also have a great strength advantage.
  6. Internal tooth profiles are easily compensated.
  7. RoundTooth^tm can also be adapted for bevel gears.

...and I am sure I've overlooked several more.

The only downside I can see is that this there is some inherent backlash during the cycling of each tooth. 

This is more prevalent with low tooth count pinions, similar to inherent undercut issues with small tooth count pinions in conventional gearing.

Another finding is that convention does not yield simple C-C distances as metric module systems does.  However, with the inherent lack of accuracy in rapid prototyping systems, I have added a simple compensation factor to allow characterization of the RP tools available to the users and teams.

If a discussion of Round Tooth^tm gear development is of interest, I would be happy to continue posting findings, examples and solutions.

Considering I do not have rapid prototyping capabilities (as yet), I would really appreciate feedback from those who are will to try this system.

For your consideration...

FIRST_technology_Round_Tooth-tm.PNG

History: I am not one to simply download files and parts from the web.  I need to test each system to know exactly what I am receiving.  The technology for gears is well developed from a manufacturing perspective which is not easily translated back into CAD.  This method has been under development for over a year.  The pure simplicity to implement in CAD is just too attractive not to share.

Challenge: The engineering behind this proposal is not well developed although it could be if someone had the interest to share stress analysis and other empirical findings.  The idea that this is a more robust design for use in rapid prototyping is that RP materials are inherently weaker than their molded or machined counterparts.  My hope is to even the odds even if it is only marginal.

With this simplified RoundTooth^tm system, my hope is to let ideas flow more easily from your CAD development effort while providing workable solutions for your prototyping efforts.

4 REPLIES 4

Interesting concept.  I'd like to suggest that FIRST is also a great forum to post this due to the fact that you're likely to hit a few future PHD candidates that could really take this and run with it.

The primary place to use gears in FRC is the transmission.  I can't see using RP gears for this except for maybe an encoder.  Other use-cases may be Pan/Tilt camera drives or other low-load, low criticality applications.

I'm definitely interested in hearing more about round-toothed gears and applications.  I do have access to a low-end 3D printer and perhaps some higher-end printers soon.

I'm a bit late to the party, but I wanted to mention that I might talk to some of my FTC teams about using this type of gear on their robots-- we have a couple in-house 3D printers and I think they could definitely benefit from experinmenting with creating their own gears. Plus FTC versus FRC mitigates most of the problems Joshua mentioned. I'll let you know here if anything comes to fruition there.

Does this work properly as a gear in theory? Just looks to me like you are going to get large surfaces rubbing against each other constantly. Although it could be the inaccuracy of a RP gear means this is comparable to involute gear forms.  

This is certainly not a normal gear and by no means would I consider this as a generic replacements.

As for contact surfaces, true, they are similar to a chain link, which is quite efficient.

The problem I ran into was internal teeth.  It stops following the "rules" when you invert the curvature.

For 3D printing mechanisms... this is a quick gear to design on the fly and it has greater strength to its counterpart.

I've gone through the geometry of making true involute gears.  I have a fairly robust model to use generically.  It is something that a lot of us end up dealing with at some point.  I just wanted to offer a simpler alternative in Creo.