Flip-out Holonomic drive

I’ve looked at a few robots where they’re a holonomic drive with the two front wheels flipping out, so there is more room. Can someone explain how to make this, or can they make a CAD model. Thank You.

Why not design it yourself and optimize it for your needs?

Do you plan on Mecanum Wheels or X-Drive or something else?:confused:

If you need help, Green Egg Robotics, team 44 did an amazing job with their Clean Sweep World Finalist robot, Fred III.

Here’s a good picture of it: http://0.static.wix.com/media/e94efcbcbf4ad3d362b8c2c522c7156d.wix_mp_1024

Here’s a video: http://youtu.be/WJVWUTbrChw
Specifically in that video, here’s a good clip of the mechanism you’re describing: [http://youtu.be/WJVWUTbrChw?t=1m41s

~Jordan](http://youtu.be/WJVWUTbrChw?t=1m41s)

I saw another good one. It was with WASABI 1492a.

http://www.youtube.com/watch?v=ef1Z7Ob1pi4

It seems as though they use pneumatics.

You have a point. I’ve been trying to do that, but I’m confused how they can flip out but still be rigid.

Green Eggs used hinges for the folding action. Their use of a quarter of a gear and the hinge locked it in place both in the counterclockwise and clockwise direction, since an axle dropped behind the gear’s edge locking it in place and the hinge prevents you from going the last 90 degrees.

Wasabi seemed to have just used a hinge with elastic, as you can see it jerking around before and after hard turns.

Oh My… I never realized that GER flip omni wasn’t powered by rubber bands its actually the wheels that drive them out to the final position! :open_mouth:

@A Rare Flightless Rock - you have a fantastic username.

  • Andrew

It makes so much sense now!

wasabis also drives out. That was perhaps GERs big secret with their robot. I’ve been looking at this drive also. But its quite difficult to get a good view of 44’s.

I understand how GER’s design worked, but what I cant wrap my head around is what the stand-off’s were for.

The stand offs were to protect the wheels and so people wouldn’t drive into them.

1492A’s flip out holonomic was inspired by GER. It took us awhile to figure out how their Clean Sweep robot achieved it, but after reviewing the videos that have already been posted in this thread, we saw that the flipout came not from some external source, but from the wheels simply driving outwards, pulling the hinge and eventually having the axle slide in and lock.

Andrew’s description has all the keywords in it. 1492A’s wheels drive themselves out as well, but the locking mechanism is an elastic powered slide rail that shoots out after the wheels turn past a certain point, preventing the wheel from coming back. No pneumatics or extra motors are used.

I do still have pictures of the whole mechanism in its design phase, you can pm me if you want to discuss more :slight_smile:

How did your’s (1492A) drive out? It looked to me as though your wheels started almost straight (like a regular chassis) whereas 44’s are always at an angle

They actually start looking holonomic, angled inwards. The whole wheel module drives itself out and then locks. I’m pretty sure the flipout motion looks very similar to GER’s, the lock mechanism is just different.

From what I can tell (correct me if I’m wrong) 1492a’s starts like an x holonomic and green egg’s starts with a u shape in the back but the front wheels are parallel to the rear ones which wouldn’t work as a normal holonomic but puts the front wheels in a good position to drive out. It seems to me that if the 1492a version dove out, it would just act as a normal holonomic, and not flip out. Can you explain how it works because I do like this design, I just don’t quite understand how it deploys.

when 1492 expands, the rear wheels arent moving, which makes the front wheels movement cause rotation around the hinge, rather than pull the robot forwards, which causes them to rotate outwards. After they rotated all the way, the locking mechanism kicks in and holds them in place.

For the hinges, are you just using an axle or this?

http://www.vexrobotics.com/catalogsearch/result/?q=hinge

Also how did you get the angle perfect.

We used VEX hinges, the angle worked closely enough to 45 degrees when the motor stopped on the metal that we left it as is. If it wasn’t perfect we would have added metal stoppers to put it at the angle we wanted.

I can imagine with a flip-out holonomic drive you will have even harder time to go straight because your wheels might not be locked-in well.