Posted by: lumpidydumpy ® 03/24/2008, 17:29:12 Author Profile eMail author Edit

Hello All, I am trying to switch a simple spur gear from steel to polymer. It's mate is itself in a timing application. I have some prototypes, and I have a few tests that I would like to put this gear through. Everyone here is worried about switching to "PLASTIC" so i need to look at testing this thing extensively. Here are the tests I am going to put it through at this point. Torque Required to break/Shear Teeth 100 hr test at published speed 100 hr test at 125% published speed 100 hr test at 200% published speed 100 hr test at 300% published speed Impulse loading for tooth shear For all of these tests, I will be using one polymer gear and one steel gear so all effects will hopefully be shown on the polymer gear. If you have any other Ideas, they would be greatly appreciated. Thanks, Adam

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: Metal to Polymer Gear Fatigue Testing
: Metal to Polymer Gear Fatigue Testing -- lumpidydumpy	Post Reply	Top of thread	Forum

Posted by: randykimball ® 03/24/2008, 18:47:18 Author Profile eMail author Edit

I'd sure consider using two "plastic" gears if you plan to use two in the real world. BTW... they are even used as cam drive gears in engines. The lowered mass can improve moving mass effeciency. OR... if space and testing equipment run both a metal to polymer and a polymer to polymer. Is your application protected from contaminates? If not be sure to introduce realistic contaminates. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

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: : Metal to Polymer Gear Fatigue Testing
: : Metal to Polymer Gear Fatigue Testing -- randykimball	Post Reply	Top of thread	Forum

Posted by: addwind ® 03/27/2008, 13:59:42 Author Profile eMail author Edit

Randykimball is right. If your application is meshing 2 plastic gears, I'd test them that way. Another immportant thing that may not show up in your test is the effects of creep. I would think that this is important since it is a timing application. You may also want to measure backlash before and after each of your tests. The correct lubrication is also important. If you are only replacing 1 gear to "plastic", the lubrication requirements may be different than if you chose to replace both gears to "plastic"; and this of course will likely be different from both being steel gears. You intend to do 100 hr tests on the gears. However, you did not indicate what the design life of this product is. I would not be concerned if the design life was 75 hours or less, but if the design life was say, 5,000 hours, I'd be concerned about the wear characteristics of the "plastic" gears too. Again, backlash is the keyword here. Good luck.

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