Macanum ability to climb ramps

[Mr. Lim]

Originally Posted by dtengineering

It's not a 45 degree incline, by any means, but we got our mecanum to go up a ramp a couple years back. The first try didn't work, so we fixed up a few things (hence the clip of a student welding the frame) and then tried again.

The catch is keeping all four wheels in contact at the same time... but here's proof that a "standard" mecanum can climb at least a shallow incline. http://www.youtube.com/dtengineering...12/gyn9e0cT3-A

Jason

P.S. If you want omni directional drive ability, plus climbing... perhaps some form of crab drive is what you're looking for?

Thanks for the video Jason! Pretty neat stuff. I have to note that the ramp is not carpeted. It seems pretty promising, and if used in combination with a really simple suspension, we may have a winner!

[joeweber]

I want everybody to know that I am getting HECK!!!! from my team mates for posting our drive system. It was fine before this game.

[dtengineering]

Originally Posted by joeweber

I want everybody to know that I am getting HECK!!!! from my team mates for posting our drive system. It was fine before this game.

I hope, at the same time, they are feeling very pleased with the opportunity to put your off-season R&D to good work!

Anyone who tries to copy that drive system will be weeks behind where you guys are right now... and even if they do manage to copy it, I'm sure you'll be on to version 2 before they even get a test platform built.

<rambling>

But this thread has me thinking that maybe we do want to revist mecanums this year... not with an articulated system like that one, that's just a bit beyond our build capacity this year, even if we replaced the central clutch with an FP and gearbox to drive the omni wheel... but instead... maybe if the front wheels also ran a belt... that didn't connect to the rear wheels (or else the pulley just free-wheeled on the rear axle) so that when you get high-centred on the climb the belt does the driving. It would be a combination of mecanum and tank-tread drive....

Hmm... I'll be interested to see what the students say on Monday. This game does seem well-suited to an omni drive, but the extra degrees of freedom offered in their mobility come at the cost of build time, programming time, and driver practice time.

But if a team hasn't built a mecanum drive... and wants to give it a try... you've gotta do it! I think mecanums are the most beautiful drive system to watch, and just love having seasoned engineers come into our shop and have a Grade 10 show them a wheel that they never knew existed!

</rambling>

Jason

[Jared Russell]

FWIW, I recall a video on the Airtrax website a few years back that showed Mecanum wheels climbing stairs. The key is, as has already been pointed out, ensuring that you don't high center, and that your rollers have enough friction to make it up (where "enough" depends very much on the dimensions of your wheel base).

[maltz1881]

LOL All of us gave poor Joe an earful and grounded him from CD!!! J/K!! We still love him, he is our super hero around here!!!

[MrForbes]

In another thread someone posted a picture of the "hump" in the floor near the TOWER....looks like some type of suspension will be a big help for a Mecanum wheeled robot.

[EricH]

Originally Posted by maltz1881

LOL All of us gave poor Joe an earful and grounded him from CD!!! J/K!! We still love him, he is our super hero around here!!!

Just remember, you're already on Version 3 or so, and have the exact plans. We don't, therefore, we are at a significant disadvantage in terms of time to reverse engineer. Go win some awards with that drive!

[RLStaple]

According to my calculations, we should be able to climb ramp as long as coefficient of friction is greater than 0.4

[pfreivald]

Originally Posted by dtengineering

But this thread has me thinking that maybe we do want to revist mecanums this year... not with an articulated system like that one, that's just a bit beyond our build capacity this year, even if we replaced the central clutch with an FP and gearbox to drive the omni wheel... but instead... maybe if the front wheels also ran a belt... that didn't connect to the rear wheels (or else the pulley just free-wheeled on the rear axle) so that when you get high-centred on the climb the belt does the driving. It would be a combination of mecanum and tank-tread drive....

This is almost exactly what we are building right now. We want to mock one up and see just how well it does...

Patrick

[joeweber]

We did test our design and it jumped right up on the "bump" with no problem. ( I have video but my team won't let me post it here ) UT?

[ebarker]

Originally Posted by joeweber

I want everybody to know that I am getting HECK!!!! from my team mates for posting our drive system. It was fine before this game.

"Ideas are cheap,The combination of ideas and execution and excellence and the whole process is what really matters." Woodie Flowers

[McGurky]

Originally Posted by RLStaple

According to my calculations, we should be able to climb ramp as long as coefficient of friction is greater than 0.4

And according to AndyMark's website, The 8" Mecanum Wheels have the following coefficients of friction:

Radial Static: 0.7
Radial Dynamic: 0.6
Transverse Static: 0.7
Transverse Dynamic: 0.6

All of which are greater than 0.4, so in theory the 8" mecanum wheels from AndyMark should work. Although we have been hearing mixed results from various mecanum wheel tests, we are confident that we will be able to make it over the "humps"

Happy Prototyping!

-Mcgurky

[Chris is me]

Originally Posted by McGurky

All of which are greater than 0.4, so in theory the 8" mecanum wheels from AndyMark should work. Although we have been hearing mixed results from various mecanum wheel tests, we are confident that we will be able to make it over the "humps"

The reason mecanums wouldn't be able to climb the humps isn't that the wheels have low traction, it's that if you go any direction other than head-on, at least one of your wheel's rollers will free spin the robot down the ramp.

Up the ramp straight is certainly doable.

[kirtar]

That sounds reasonable (as long as you don't high center), as the rollers aren't exactly powered or anything. Especially don't try to do it going up on the diagonal of your robot.

[thefro526]

Originally Posted by Chris is me

The reason mecanums wouldn't be able to climb the humps isn't that the wheels have low traction, it's that if you go any direction other than head-on, at least one of your wheel's rollers will free spin the robot down the ramp.

Up the ramp straight is certainly doable.

That's a very good point.

I remember some teams talking about playing with how tight their rollers were back in the day. This makes it harder for the rollers to free spin, which increases traction when not going straight, but also will make it slightly harder to strafe. It's something worth playing with.