pic: Team 148 - 2011 - Raptor

If you can’t appreciate cool mechanisms like this, you probably can’t appreciate anything!!

I especially like the use of sheet metal for everything, including the stacked plates to create the gear teeth on the smaller arm driven by the gearbox.

Thanks for sharing JVN.


The shoulder joint is driven by (1) Banebots 775 motor, and (12) bands of surgical tubing.
You can see the 775 in this pic:


You guys obviously rivet a lot, I assume you have a pneumatic rivet gun.

Any recommendations on one that is pretty reliable?


We buy the crappy ones from Harbor Freight – they last about a season before they break. We replace them every year. Students are hard on riveters.


This robot is amazing.

I would think that the double fourbar linkage would actually simplify the arm’s joint design (at least in my mind it seems so much easier to deal with weight and taking loads) in that you would have to worry less about powering the pivoting point (gearboxes and chain) and instead focus on the making the actual joint stronger and more stable. I also could see it as isolating the motors and gearboxes from the abuse (as in side loads) the arm could take in a match, which I see as beneficial seeing how much defense this robot will likely have to put up with. Those are some of many potential benefits that I thought of when I first saw it.

After receiving a number of requests in response to this post, I decided to highlight some of the subtle parts of this year’s design on my blog as part of an “Inside Raptor” series.

Here is a glimpse at one of the SIMPLE subtle features that I think makes Raptor special… press-on CIM pinions:


Wow, that’s a really good idea. I can’t tell from the picture, but does the pinion have the Key Shape cut into it, or do you just rely on the press fit to transfer the torque?

Wow. The press on pinions are very elegant. Did you guys do any slip calcs or tests?

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Hell. Yeah.

Awesome idea Greg. Kudos to team 20 for producing the parts.


That’s a cool idea! I wish we had the resources to try cool things like that.

What’s the easiest way for Low Resource Team to get press on CIM pinions?

Well it works for dewalt pinions, why not elsewhere, great idea

If you had the right size reamer, you could do it that way…

Press fits are a reliable way of holding gears onto shafts. Getting the fit right is sort of critical, but even if you can get it within a thousandth of an inch or so you should be ok, if it’s a tight enough fit.

Drills don’t work too well for this.

Also the dewalt gear is IMHO too small to fit reliably on the CIM shaft, there just isn’t enough meat there. Others will disagree…

We rely on just the press fit to transfer the torque. It works fine – no problems after hours of aggressive use.

Bring the idea to Andy Baker’s attention? :slight_smile:

Identify potential sponsors in your area who have EDM capability, and ask nicely.

…or reach out to a team in your region who already has an EDM-capable sponsor, then see if you can barter with them. We’ll machine X parts for you if you give us Y extra parts or machine Z for us in return. Bartering is fun around these here parts. Our NEOFRA teams trade materials and sponsor services all the time. Example: I submitted some lexan from 379 to our waterjet sponsor along with all our parts; in return, the RoboCats gave me their unused KOP accumulator.

Huh, what, did someone mention me in the same thread as this beautiful and effective robot?

I will be sure to bug John and Greg about this in San Antonio next week.


Hmmm, I really, really hope this makes it into the AM Product line. Now that I think about it, Press Fit Pinions would make transmission assembly way easier.

And pinion/motor disassembly more difficult.

Not that WE’ve ever lost a gear due to lack of lubrication…just sayin…but I suppose having a couple extra motors with gears pressed on would be a reasonable thing to do.

One of those d’oh! moments… We’ve been wire EDM’ing all gears for our gearboxes since 2007 and that stupidly simple idea never occurred to me! In 2012 we won’t be fighting with keyways, let me tell you that!

The easy answer is find someone with a wire edm to make them for you. You can do pressfits with a reamer on a lathe, but the issue with these is that every gear that I found that was off the shelf 11tooth already had a bore which was over the pressfit size. So you would need to find a source for some gear stock (if you find it let me know I couldn’t find any. )

You can get 12T 20DP gearstock. Obviously not quite what you have, but if a team were to be satisfied with a 12T already and just wanted to press it on, that would be a solution.