pic: FRC488 Octocanum.

[Madison]

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[LLogan]

I have been waiting for somebody to create this.

Looks like you have the best of both worlds. Where are you going to place the piston? I'm having a hard time visualizing where you'll be mounting it.

What configurations are you going to have your wheels in? I.e. four traction only, four mecanum only, 4 traction + 4 mecanum, etc.

[xSAWxBLADEx]

Originally Posted by LLogan

Looks like you have the best of both worlds. Where are you going to place the piston? I'm having a hard time visualizing where you'll be mounting it.

maybe where the ziptie is?

[Nikhil Bajaj]

Originally Posted by LLogan

I have been waiting for somebody to create this.

Looks like you have the best of both worlds. Where are you going to place the piston? I'm having a hard time visualizing where you'll be mounting it.

What configurations are you going to have your wheels in? I.e. four traction only, four mecanum only, 4 traction + 4 mecanum, etc.

The 488 version looks awesome. 461 prototyped this drivetrain over the last year and a half and summer, here is a link to that thread.

http://www.chiefdelphi.com/forums/sh...ad.php?t=86171

Hope that helps you see how this sort of system works.

[s1900ahon]

Nice.

You should loop the Jaguar's PWM cable under the front tab on the Jaguar.

[Katie_UPS]

We were joking about making that this year! I'm glad to see that someone did!

[Madison]

Originally Posted by LLogan

I have been waiting for somebody to create this.

Looks like you have the best of both worlds. Where are you going to place the piston? I'm having a hard time visualizing where you'll be mounting it.

What configurations are you going to have your wheels in? I.e. four traction only, four mecanum only, 4 traction + 4 mecanum, etc.

The wheels are going to be actuated by two pistons -- one along each side of the robot. It's hard to visualize because all of the hardware associated with that system is still missing. We'll add a vertically mounted arm to each wheel pod that the piston will push or pull upon. This creates a four-bar linkage where none of the links are grounded. The 1x1 cross piece that the pods are currently zip-tied to will act as a stop for the pod rotation and, effectively, ground one link of the four bar.

In retrospect, it would've made more sense to actuate each wheel pod individually, but the system we're implementing is a bit lighter. As a result, we can only run on all mecanums or all traction wheels.

Originally Posted by AdamHeard

I like it, what is the speed difference?

There is an additional 22:32 reduction between mecanum and traction right now, in addition to the difference in wheel size -- 4" vs. 6". We may experiment with this some more.

Originally Posted by spiffyspleen

That looks amazing,are you guys going to be at the Portland Regional this year?

Yep!

Originally Posted by Joyride_67_1902

I like it!

However a few questions

Why did you chain all the drive wheels, instead of power one of the directly and derive power off that wheel?

How much does it weigh? (without a super structure)

Where does the piston mount?

I tried to make direct drive of the mecanum wheel a reality, but AM's "long" output shafts were not quite long enough to make it plausible. It would've simplified a lot of things, certainly.

I am not certain of its weight. We'll try to weight it today, but I'd guess it's around 50/55 lbs.

Originally Posted by Bjenks548

That is going to be a very fun drive train to watch, just like 217 and 148 last year. How much does it weigh? and Why did you put the mecanum wheels on the outside?

Mecanum wheels are outside because they're geared faster than the traction wheels and we wanted the widest wheelbase possible to accommodate rapid changes in direction. Putting the traction wheels on the inside also makes it easier for the robot to turn while they're in place.


Here's some brief video of the first test of the mecanum wheel set. It's nothing too earth-shattering, but I understand that, by the time they left last night, our programming group has field-oriented drive running well.
http://www.youtube.com/watch?v=RA-jd48tPFM

[Ether]

Originally Posted by Madison

Mecanum wheels are outside because they're geared faster than the traction wheels and we wanted the widest wheelbase possible to accommodate rapid changes in direction.

Could you elaborate a bit on that please.. How does making the wheelbase longer accommodate rapid changes in direction?

[Vikesrock]

Originally Posted by Ether

Could you elaborate a bit on that please.. How does making the wheelbase longer accommodate rapid changes in direction?

Rapid direction changes + Short wheel base + tall manipulators = Tipping

The longer the wheel base, the less likely you are to tip when accelerating hard or coming to a hard stop.

[Andrew Schreiber]

Originally Posted by Vikesrock

Rapid direction changes + Short wheel base + tall manipulators = Tipping

The longer the wheel base, the less likely you are to tip when accelerating hard or coming to a hard stop.

However, mecanum is not at all like full blown swerve. The bot tends to drift a little bit as the rollers spin which should help remove some of the problems typically associated with rapid direction changes and tall manipulators. That being said, I still would not change direction at full speed (or even drop those traction wheels) if I had any sort of large mass up top. But knowing what I know about 488 they will have thought that out already (this ain't their first rodeo with mecanums).

Cool system, glad to see someone went with it, hopefully the ability to strafe will be beneficial.

[BJC]

I'm very curious as too why you put the traction wheels on the inside as to opposed to the outside. As of now it appears that you are not really taking full advantage of switching wheel base sizes. Why not put the traction wheels in the longer wheel base configuration to make it that much more difficult to turn as opposed to the mecanum wheels which could be made to preform equally well on the shorter (inner) wheel base?

Otherwise, really cool.

[Dad1279]

We prefer to call them über-mecanums.....

[dmaldonado]

Well team 1708 did a very simalar design

http://www.chiefdelphi.com/media/photos/34890

[Racer26]

I like the idea. If the execution can be made perfectly reliable, it should be a formidable drivetrain. The trick comes in ensuring theres no problems with throwing chains etc.

[Madison]

Originally Posted by BJC

I'm very curious as too why you put the traction wheels on the inside as to opposed to the outside. As of now it appears that you are not really taking full advantage of switching wheel base sizes. Why not put the traction wheels in the longer wheel base configuration to make it that much more difficult to turn as opposed to the mecanum wheels which could be made to preform equally well on the shorter (inner) wheel base?

Otherwise, really cool.

We anticipate using the mecanum wheel set most of the time, so we wanted that to be our most stable configuration. The traction wheels are not really intended to prevent others from turning us in place, but to kindly remove defense from our path when the mecanum wheels can't get us around it.