pic: 254/968 Gearbox - Destructive Testing Results

[MrForbes]

Interesing points about the reduced costs with very large production runs.

Many teams rely on others to shoulder the "up front" cost of buying/leasing CNC equipment, and end up buying parts that available off the shelf ....it's neat that you had the opportunity to design and make these transmissions!

[JesseK]

Any chance you'll do endurance (constant fluctuations in fatigue) testing with this transmission? Granted these things are built for (at most) 3 competitions and a bit of practice (about 120 minutes of run time if you make the finals at competitions) but what would happen if you tried to put the robot under its stresses for say, twice that amount of time in a competition-style environment?

My Material's Science intro class went over a bit of sheer stress analysis but the details escape me at the moment. Is there a way to get a product lifetime estimate from the tests done already?

Excellent opportunity you have to be able to do such a disciplined and detailed analysis.

[Travis Covington]

Funny you ask. We did do long term accelerated wear and fatigue testing.

We built a total of 16 gearboxes. 4 of them went on competition robots. 254's comp bot saw ~8 hours total run time including practice at 4 events. 968's comp bot saw only ~4 hours run time including practice at 2 events.

However, there were another 4 gearboxes built and used on two practice robots which each saw ~100 hours of driving. After these 100 hours of aggressive use, we saw little to no difference between the practice robot gearboxes and the competition gearboxes with less than 10% of the runtime the practice ones saw. It was determined that the anodize wears initially after 2 or so hours of use and remains at that worn, broken in point for the remaining time.

In addition to those 8, we used 2 more gearboxes on an accelerated wear test platform. We mounted the gearboxes onto a mock side rail and programmed a continuous loop program to cycle the motors and actuate the shifting cylinder: full forward, shift, full reverse, shift, for another 100 hours under load.

Here is a picture of that test platform after the 100 hours of testing. You can see the anodize wear, but after measurement, the involute tooth profile is intact. We also disassembled the gearboxes and checked for any fatigue issues and further damage or wear... while we didn’t have the ability to do a thorough lab test, our brief visual inspection showed no damage or signs for concern.





Also, here is a video showing the test platform with a wheel mounted for later use as a demonstration unit. As shown in the video and pictures, there is no load on the output shaft. This video is strictly to show the cycling procedure used. We may bring this to IRI if people want to see it?

http://sivart.org/misc/Demo%20Gearbox.avi

Lastly, here are the components removed from the test platform after ~100 hours of continuous use. Some wear is noticible, other portions are just dirty from the anodize wear.

[Andy Baker]

Originally Posted by Travis Covington

Funny you ask. We did do long term accelerated wear and fatigue testing.

These are amazing results. Even better, Travis has done a great job explaining this testing and failure modes.

It is one thing to be a great designer, it is another thing to be able to explain what you did, how things work, and why things happen.

Personally, I appreicate this work. Needless to say, FIRST will see better designs from many people because of this effort. This design has indeed "raised the bar" in FIRST.

Most respectfully,
Andy Baker

[robostangs548]

Very nice, very strong, looks like a great piece of equipment.

[AdamHeard]

Travis,
Great work guys. I have been fascinated by these transmissions ever since the first pic shown and have spent a good amount of time at LA, SD and champs admiring them. The amount of work put in is really shown in every part and detail. Also, the fact that you are going to such great lengths to publish your results (I know you did the test anyway for the senior project) is much appreciated. I am already inspired and thinking of what I can do for my Senior Project at San Luis Obispo and I haven't even finished my senior year of high school yet.

Originally Posted by Andy Baker

Personally, I appreciate this work. Needless to say, FIRST will see better designs from many people because of this effort. This design has indeed "raised the bar" in FIRST.

Most respectfully,
Andy Baker

Sorry, couldn't resist, but does AndyMark have any improvements planned to the your shifters?

[Andy Baker]

Originally Posted by AdamHeard

Sorry, couldn't resist, but does AndyMark have any improvements planned to the your shifters?

Yes, there will be a new version of our shifter available this fall, but I don't want to take the focus off of what 968 and 254 have done here. There will be enough information about that later.

I am looking forward to IRI for many reasons, and one of them is to talk with Travis and get a tour of this gearbox.

Andy

[M. Mellott]

Wow! A very impressive effort both in the design and the quality of testing. Really nice work, guys!

[Ryan Dognaux]

I checked these out in Atlanta and they're the real deal. Quite possibly the most amazing transmissions I've seen to date in terms of simplicity, quality, and resilience. The coolest part is just picking it up, like a mechanical feather or something...

I'm anxious to see what other ideas come as a result from these gearboxes. Great job guys.