Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

I've used these a few times as well. Some things I've learned about them from my experience: Use a larger outside diameter if possible. It will be able to take more severe loading and misalignment. Use Hytrel spiders/inserts as opposed to the Buna-N rubber. The rubber ones cannot take as much torque and can wear out. Rigidly mount whatever is on each side of the lfex coupling. Flexing of the mount can cause flex coupling failure.

Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Thank You guys very much i really appreciate it.

Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Don't forget about the Dewalt shifting drill gearboxes. They're a lot cheaper than the AM shifters, and you can get three gears instead of two or one.

They are however... a little more fragile...

Also, if you just want a 1 speed why not use modified banebots? Or whatever else they give us next year?

Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Here are some basic recommendations for designing and building your own gearbox for FIRST Robotics Applications:

1. Fabrication accuracy is key. No matter how good your design is, if your fabrication is not good, then headaches will persist for the entire season. Learn from experienced people (skilled trades folks, instructors, etc.) with regard to making precise features like bearing press fits, concentric keyed holes, and accurately placed bearing holes on a plate.

2. Use 20 dp (diametric pitch) gears. These are fairly abundant. Industry standard gears of this pitch can be purchased from McMaster-Carr, MSC, Martin, Berg, Boston Gear, Stock Drive Products, Rino Mechanical, and other vendors. They can be found with a pressure angle of 20 and 14.5 degrees. These don't mesh well together (they do, but things get really noisy). I think that the 14.5 degree version is a bit more abundant. Also, Misumi is probably be best resource for metric gears. I recommend module 1 for most FRC applications.

3. In gearbox design, add 0.003" to your center-to-center distance. This allows for a bit of eccentricity of your gears, and only adds a negligible bit of backlash.

4. Find a resource for 1/2" or 3/8" hex broaching, and then use 1/2" or 3/8" hex shafting instead of keyed shafts. However... I'll admit that keyed shaft gearboxes are getting easier these days since McMaster-Carr and other places will sell stock of pre-keyed steel and aluminum shafts.

5. I recommend steel gears to start out with. However, if you can justify using plastic, aluminum or brass gears, then those work also. These, of course, can withstand less force and gears will shear if the force on the gear is higher than the gear tooth's cross sectional area x the yield strength of the gear's material. I would also multiply in a safety factor of 2x.

6. When in doubt, increase your face width. Usually, 3/8" is a good face width, but for higher torque situations you may want to go to 1/2" or 5/8" wide gears.

7. Don't forget to lube. Lithium grease is always a good lubricant on a simple gearbox. If you want things to move back and forth on a shaft, like in a dog shifting gearbox, use a lighter lubricant such as an oil.

8. Buy the parts that are difficult to fabricate, and then make your own parts. Many people ask me "why do you sell spare parts for your shifters and gearboxes... do these parts wear down?" My answer to this is "no... they don't wear down, but we sell individual parts so teams can design and build their own gearboxes by using a few of our parts."

9. Get your design made and take pride in your gearbox.

Andy B.

Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Or you could design and build an awesome scoring mechanism and take pride in THAT, while you drive your robot with Andy's gearboxes.

Re: NEeD HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Some general advice from another team of PI-O-Neers:

I think 2-speed shifting gearboxes are cool, BUT unless there was a real need for them to excel at a particular game, I'd rather put my efforts and money into something else.

Resist the temptation to build a cool robot that doesn't do anything well.

Don

Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Bingo!

Building your own is a great idea but teams that do it successfully usually do a lot of development in the off-season. If you want to shift, buy a AM or use the dewalt and then develop your own this summer.

Re: NEeD HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

You have a really good point, i think were are going to go with a 1 speed gearbox from andymark as oppose to making one. Thank You very much PI-O-Neer.
P.S I didnt think there was another team named pioneers in FRC. This is going to be our 2nd season

Re: NED HELP ON BUILDING 1 OR 2 SPEED GEARBOX
 

Team 116 has posted designs of their 2002-2004 era 2-speed, crash shifter. While this specific design is now outdated (Bosch drill motor not included in 2005-2007 KoP), variants of this design are still used (379's 2007 shifter was based on this, as well as several other "descendants" of this transmission).
http://www.chiefdelphi.com/media/papers/1437
In 2007, Team 116 used the AndyMark gen.2 shifters.