3 ms·

A better option would be to use aircraft or marine grade plywood—somethings that’s guaranteed not to have voids. It’ll be a lot stronger than making the teeth i

by crgwbr 7y ago

A better option would be to use aircraft or marine grade plywood—somethings that’s guaranteed not to have voids. It’ll be a lot stronger than making the teeth individually and attaching them to a round core.

bacon_waffle 7y ago
The strength of wood is quite directional; since the plys in plywood are not in the same orientation, it's almost by definition less strong than a solid piece of the same type of properly oriented wood.
- theothermkn 7y ago
  A lot of people believe this, but it is incorrect. In plywood, the glue transfers the load across the faces of each ply from strand to neighboring strand through the adjacent plies. This can result in a stronger bond between neighboring strands than if no cross-plies were present. This amounts to more than just splitting resistance. As a parallel case, consider multi-ply composite construction, where sheets of fabric, sometimes of sheets with a single fiber orientation, are laid at angles to each other to spread the loads in exactly this way. They both better approximate an isotropic material, and are stronger than an equivalent thickness of singly-oriented plies all in the same orientation.
  - abakker 7y ago
    Can validate. Using Plywood, especially marine plywood is the right choice. It is much stronger.
  - bacon_waffle 7y ago
    Sorry, I think you're misunderstanding my argument. I agree that wood reinforced glue is stronger than wood, but it's not really speaking to improving a wooden gear as above. Gears are subject to predictable stresses, and so being able to orient a material to best handle those stresses will make a stronger gear. Plywood, like anything else, is a compromise that, as you say, has a more isotropic character. Obviously, there is a wide range of strength in wood, and so plywood. I think it's reasonable to say that one could construct a stronger gear using teeth from readily available solid wood, then readily available plywood. Good luck finding hickory plywood :). To your first sentence though, if you take the same size and quality solid board and piece of plywood at your local hardware store (making a reasonable attempt at an apples-to-apples comparison), the board will be almost certainly be stiffer and stronger with the grain, than the plywood will: https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_12.pdf https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_...

by crgwbr 7y ago

bacon_waffle 7y ago

The strength of wood is quite directional; since the plys in plywood are not in the same orientation, it's almost by definition less strong than a solid piece of the same type of properly oriented wood.

theothermkn 7y ago
A lot of people believe this, but it is incorrect. In plywood, the glue transfers the load across the faces of each ply from strand to neighboring strand through the adjacent plies. This can result in a stronger bond between neighboring strands than if no cross-plies were present. This amounts to more than just splitting resistance. As a parallel case, consider multi-ply composite construction, where sheets of fabric, sometimes of sheets with a single fiber orientation, are laid at angles to each other to spread the loads in exactly this way. They both better approximate an isotropic material, and are stronger than an equivalent thickness of singly-oriented plies all in the same orientation.
- abakker 7y ago
  Can validate. Using Plywood, especially marine plywood is the right choice. It is much stronger.
- bacon_waffle 7y ago
  Sorry, I think you're misunderstanding my argument. I agree that wood reinforced glue is stronger than wood, but it's not really speaking to improving a wooden gear as above. Gears are subject to predictable stresses, and so being able to orient a material to best handle those stresses will make a stronger gear. Plywood, like anything else, is a compromise that, as you say, has a more isotropic character. Obviously, there is a wide range of strength in wood, and so plywood. I think it's reasonable to say that one could construct a stronger gear using teeth from readily available solid wood, then readily available plywood. Good luck finding hickory plywood :). To your first sentence though, if you take the same size and quality solid board and piece of plywood at your local hardware store (making a reasonable attempt at an apples-to-apples comparison), the board will be almost certainly be stiffer and stronger with the grain, than the plywood will: https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_12.pdf https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_...