pic: 2996 Octocanum Prototype

[Liquid_Science]

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[AdamHeard]

I'd be concerned about the slender shafts that front and rear of the cylinders attach to. They might not have enough stiffness.

[thedude019]

This looks great! Is the weight an issue? Ive seen some really heavy octocanum drives before.

[JoshWilson]

Originally Posted by Liquid_Science

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looks pretty cool, but I'm not exactly sure how that type of drive train is beneficial, could you explain? I've never seen or heard of it before, so I don't know anything about them.

[Ari423]

Originally Posted by JoshWilson

looks pretty cool, but I'm not exactly sure how that type of drive train is beneficial, could you explain? I've never seen or heard of it before, so I don't know anything about them.

The idea is that you get the best of both worlds: mecanum wheels for maneuverability and traction wheels for pushing. The main downsides are weight and complexity.

[jnicho15]

What was your reason for putting the traction wheels on the pivot? In my team's design, we placed the mecanums on the pivot because then, when you retract the traction wheels, you don't need as much cylinder force to hold them off the ground. For traction mode, the mecanums barely need to be off the ground or can be slightly touching- the cylinders don't need to support nearly as much weight. In your design, the cylinders need to hold the whole weight of the robot up off the ground so only the mecanums are touching.

[Liquid_Science]

Originally Posted by thedude019

This looks great! Is the weight an issue? Ive seen some really heavy octocanum drives before.

We managed to get the weight right around 54 pounds with everything needed to run the bot (electronics, pnematics, ect.)

[Liquid_Science]

Originally Posted by jnicho15

What was your reason for putting the traction wheels on the pivot?

The biggest reason is we wanted to use 4in casters and 6in Mecanums. The cylinders we used should be plenty enough to lift even a fully weighted robot, since the boar on each is 1.5" with a 1" stroke, and there are 4 of them. Aslo, we wanted the casters to be the default wheel if something failed. The two wheels can easily be switched around, if we wanted to run 6in casters and 4in mecanums; depends on the game really.

[JoshWilson]

Originally Posted by Ari423

The idea is that you get the best of both worlds: mecanum wheels for maneuverability and traction wheels for pushing. The main downsides are weight and complexity.

Ok, that makes a lot of sense. Thanks for the explanation!

[aldaeron]

Have you thought of doing a single larger cylinder between the two modules a la Blue Cheese. Might be less parts and less weight.

What is your gearing for each wheel shaft in the pods from the CIM?

Are you concerned about deflection when the mecanums are down? Seems like a much longer moment arm around the rotation axle. I have wondered this for all the octocanum designs I have seen on CD. It seems like you would want to support the end of the axle that the pod rotates around with a bearing and have an external frame rail running the length. Perhaps the plate between the two pods is enough. Have you tried stacking weight on it to get the bot to 150 pounds?

Love the FIRST logo in the frame =)

-matto-

[Chris is me]

Originally Posted by jnicho15

What was your reason for putting the traction wheels on the pivot? In my team's design, we placed the mecanums on the pivot because then, when you retract the traction wheels, you don't need as much cylinder force to hold them off the ground.

Two great reasons to pivot about the traction wheels. First is that traction wheels will see a lot more force in all directions than the mecanums will, especially when being pushed from the side. Pivoting about the traction wheels means these wheels are more rigidly supported by the whole frame. Additionally, mecanum wheels seem to behave better when on a suspension, and the cylinders will serve as a form of a suspension, helping to ensure all of the wheels are touching the ground. The amount of cylinder force for holding one wheel off of the ground instead of the other really shouldn't change in either case.

[JesseK]

How does this drive train plan to handle bumpers?

[T3_1565]

I really enjoy looking at these types of drive trains. Back in my days these types of drives were never heard of. I made something to try and accomplish what this does.

These are cooler to see people make for sure.

[JesseK]

Originally Posted by T3_1565

I really enjoy looking at these types of drive trains. Back in my days these types of drives were never heard of. I made something to try and accomplish what this does.

These are cooler to see people make for sure.

You should provide a link. That type of drive train hasn't been seen since. It was really cool for its time, IMO.

[nuclearnerd]

Wow, pretty!

I would really recommend extending the outer plates that join your pivot points all the way out to the front and back plates if you can. I'd be worried about cantilevering those huge assemblies off the side of a pair of bearings that are only < 1" apart! Doing so would also let you support your side bumpers for more of their length (the 2014 rules required support every 8").