Robonauts CAD

[ajlapp]

Maybe I'm missing something, but how did you get your chain in there?

You drop the chain and sprockets straight into the tube from one end. Then, while the sprockets are approximately in position, you slip your shaft into place and put the backside bearing in.

We ran this setup all year without maintenance.

221 Robotic Systems is launching a production version based on this design for 2014. Personally I loved the space we gained back by moving the chains inside and the weight saved by removing the tensioning device.

[Chris is me]

Wow, I did not think internal chain like that without tensioner a was even possible. I can't believe the chain never stretched or loosened. The space savings over internal timing belt (not to mention cost) means my team will have to seriously consider this as an option for 2014.

[ajlapp]

I can't believe the chain never stretched or loosened.

I'm sure it did loosen over time...likely due to sprocket wear. However, it can't go anywhere. It would have to eat away the tubing to jump off.

FYI...I'm quite sure FRC233 has been doing this for a while. There may be others too.

[smistthegreat]

Originally Posted by ajlapp

I'm sure it did loosen over time...likely due to sprocket wear. However, it can't go anywhere. It would have to eat away the tubing to jump off.

FYI...I'm quite sure FRC233 has been doing this for a while. There may be others too.

340 has been doing it for the past couple of years too.

[Akash Rastogi]

Originally Posted by Chris is me

Wow, I did not think internal chain like that without tensioner a was even possible. I can't believe the chain never stretched or loosened. The space savings over internal timing belt (not to mention cost) means my team will have to seriously consider this as an option for 2014.

It was definitely cool to see at IRI, and just made quite a lot of sense. I was surprised to have not thought of it before.

PS - I always tell this to people who ask me about 118, but Anthony gives THE BEST robot tours. I look forward to it each time I see them.

Thanks for the CAD!

[mman1506]

Originally Posted by ajlapp

I'm sure it did loosen over time...likely due to sprocket wear. However, it can't go anywhere. It would have to eat away the tubing to jump off.

FYI...I'm quite sure FRC233 has been doing this for a while. There may be others too.

In the unlikely event of a chain breakage, how long would it take to replace the chain?

[ajlapp]

In the unlikely event of a chain breakage, how long would it take to replace the chain?

Theoretically it should be impossible to generate enough traction at the wheel to overcome the tensile strength of the chain.

That said, it didn't look plausible to us to replace a chain in the heat of battle.

So, to give ourselves comfort we built a complete chassis in the pre-season to test the setup. This included stress testing the chains by continuously going between max forward and reverse torque. We survived this testing without incident.

Both the practice bot and comp bot went the whole season without a blown chain. Once I recall we had a chain jump the sprocket and jam...this was determined to be cause by a rivet body that had made its way under the chain and sprocket....it was resolved without removing any parts.

[craigboez]

Does anyone sell that double sprocket as an off the shelf item or is that custom?

[BurkeHalderman]

Originally Posted by craigboez

Does anyone sell that double sprocket as an off the shelf item or is that custom?

It is custom, but I believe 221 Robotics Systems will be offering it separately with a keyed bore.

[ajlapp]

Soon.

SimpleTube Chassis System

[Akash Rastogi]

Originally Posted by ajlapp

Soon.

SimpleTube Chassis System

Any idea when the sprockets will be available?

[ajlapp]

The whole chassis system and it's accessories are scheduled for kickoff weekend.

The current plan is to offer all of our popular transmission options, 6wd, 8wd and several size options.

[scottandme]

Looks like the 2013 robot and the SimpleTube chassis don't have the center pair of wheels dropped - how are you avoiding wheel scrub during turns? Looks like all of the 118 wheels are the same dia - do the custom wheels have a low lateral CoF?

[ajlapp]

Looks like the 2013 robot and the SimpleTube chassis don't have the center pair of wheels dropped - how are you avoiding wheel scrub during turns? Looks like all of the 118 wheels are the same dia - do the custom wheels have a low lateral CoF?

The Robonaut wheels were not the same diameter. The outer wheels were approximately 1/2" smaller in diameter. The CAD may not reflect this.

The internal geometry of the double sprocket does not allow for any drop.

SimpleTube will use this same arrangement of different sized wheels.

[Answer42]

Does that difference in wheel size cause faster wear on the wheels because of difference in speed? I ask because I noticed 118 had a lot chunks taken out of their wheels at SVR before they replaced them.