If I were to build a new robot, what type of casters should I use?

Matt Gilliland · 2012-07-03 10:27

Casters?
Alternatives?
Pro's?
Con's?
Hit me with your best shot(s)...
-MattG

W9GFO · 2012-07-03 10:41

I don't know but I can tell you that the 70lb Eddie based robot I built required heavier duty casters. Harbor freight had some decent ones.

I would have liked to use omni wheels but I could not locate any on short notice that had soft rollers. The plastic rollers are a bit noisy on hard floors.

Martin_H · 2012-07-03 11:16

It depends upon the usage. If you don't care about odometry then a 4x4 bobcat style drive eliminates casters entirely and improves traction.

erco · 2012-07-03 11:27

Many times, a single central caster is best, to avoid unloading your drive wheels on uneven terrain. Obviously you want to keep most of your weight on your drive wheels.

Whit · 2012-07-03 12:50

Casters? Castor Oil, of course...

Alternatives? Alternative Rock

Pro's? Parallax

Con's? Andy and Red

Hit me with your best shot(s)...Pat Benatar

Sorry in advance...

Zoot · 2012-07-03 13:13

I use very heavy-duty industrial casters on my larger 'bots. While McMaster may sell these, I generally find that hitting a caster supply house locally is the best bet -- wide range of duty applications, tire/tread types, mounts, etc. (here we go to Albuquerque Caster which stocks 1000s of casters in every imaginable size/mount/tread/wheel configuration).

RobotWorkshop · 2012-07-03 15:36

Matt Gilliland wrote: »

Casters?
Alternatives?
Pro's?
Con's?
Hit me with your best shot(s)...
-MattG

I would use single wheels on the castors. For the wheels I would use Colson Castors for both the main drive wheels and the castors. The thin variety for the castors. Use non-marring grey.

They are some of the best wheels you can get for a robot. I have some that have been in use for over 25 years and still work well. Not going to get that kind of lifespan from an inflatable....

Robert

Phil Pilgrim (PhiPi) · 2012-07-03 19:34

'Depends on what you're casting and how much you want to spend. Zebco makes some entry-level stuff, but Shimano and Daiwa both offer some nice high-end alternatives.

-Phil

Ttailspin · 2012-07-03 20:49

Casters? Really?... With all the exciting modern alternatives available..

why bother with something so primitive? It's time to upgrade!

-Tommy

JLocke · 2012-07-04 00:00

Hey Matt, it's hard to get a straight answer from this group, eh?

Matt Gilliland · 2012-07-05 10:22

Hey Matt, it's hard to get a straight answer from this group, eh?

You are so right, JL. I expect it from the likes of Phil and erco - but Whit too? All is lost!

No! With guys like the Gentleman in a Tailspin, Zoot, and Mr. Robot(shop) - there is hope...We shall continue to vanquish the Clowns of these Hallowed Forums to create a future and a hope for all that is Robotic...

Rolling right along-
-MattG

Ttailspin · 2012-07-05 19:46

LOL, What did you expect? We all know mattG was just fishing...
He works for the company that makes the ultimate caster...:thumb::thumb:

-Tommy

mindrobots · 2012-07-05 20:55

How about a nice peg leg and an animatronic parrot with an emic-2 board all put together in time for Sept 19 and "Talk Like a Pirate Day" - now, that would be a robot!

Matt Gilliland · 2012-07-05 21:25

LOL, What did you expect? We all know mattG was just fishing...
He works for the company that makes the ultimate caster...

Why thank you TT...but I am serious :thumb:

We're thinking of a different platform/caster assembly concept right now, and I thought we should tap this "brain trust" (apologies to ProfBraino) for thoughts and suggestions.

I do wonder how well a nice, cherry or walnut caster would look.
Not

Well, Roll me up, and call me a hot-dog,
-MattG

Whit · 2012-07-06 07:47

Hey Matt - Okay - Serious answer...Other than the great tailwheel you guys make (like for eddie and madeusa - except maybe a super heavy duty version), or the omni type wheel ala Stingray, or the good old tail ball on the BoeBot - are there really really many other options?

I like what erco said about using a single tail wheel on rough terrain... There is also the steering tail wheel(s) option which is kinda fun and looks cool.

It depends too if you are going for zero turning radius or not. I would personally like to see Parrallax develope a multi-directional platform with 3 or 4 wheels.

erco · 2012-07-06 07:53

Enough with the casters. There is a glut of simple diffdrive platforms out there, the world is hardly clamoring for another. Time for Parallax to man up and make a Segway-style balancing robot. You'll sell a heap of those! Seriously, you already sell a quadrotor. A balancebot is significantly simpler. Why not?

mindrobots · 2012-07-06 08:11

OK, serious.

What Whit and erco say make lots of sense. Parallax has the 3 wheel scene pretty well covered with a number of options from starters to big GUYS. A good 4 wheel platform would be nice, multi-directional wheels would be a great option and a balancer would be AWESOME. The processing power and peripheral sensors are all available. Providing a good experimenters platform in any of these configurations will be welcome.

Even a hexapod or some multi-legged walking configuration would be more interesting than another 3 wheeler.

...now, back to the peg leg and the emic-2 parrot.......

tobdec · 2012-07-06 08:58

A parallax hexapod would would be bought by this guy the day its available!

Matt Gilliland · 2012-07-06 14:12

are there really really many other options?

Exactly my question, and that's why I'm asking you'all - if there's any other options out there that I don't know about, I turn to you to fill in my blanks.
Besides, isn't two wheel balancing kinda obsolete anyway?

Eagerly awaiting the brain-power of this collective...
-MattG

Phil Pilgrim (PhiPi) · 2012-07-06 14:19

Okay, how about a hovercraft-type "caster"? A small fan might be all you need for it if the weight on the caster low enough, and it would have almost zero friction in any direction. 'Wouldn't work very well on rough terrain, though.

-Phil

W9GFO · 2012-07-06 14:42

I'd like to see Parallax make some 5" or larger mecanum wheels. Just like the Vex ones but larger - and not green.

erco · 2012-07-06 20:24

At $60, those (green!) Vex mecanum wheels are one of the best deals around. I kinda doubt if Parallax could come anywhere close in price. Although they would be gorgeous CNC'ed aluminum...

Ttailspin · 2012-07-06 21:03

You already have several Wheeled Machines, and a Flying machine.
Maybe it's time Parallax ruled the waters...

By Land, Sea, or Air, Parallax will allways be there... <<(i just made that up, You can use it if you want...:thumb:)

-Tommy

Ken Gracey · 2012-07-06 21:18

Ttailspin wrote: »

You already have several Wheeled Machines, and a Flying machine.
Maybe it's time Parallax ruled the waters...

By Land, Sea, or Air, Parallax will allways be there... <<(i just made that up, You can use it if you want...:thumb:)

-Tommy

I also think that surface water robotics is an interesting field.

- Ken

Ttailspin · 2012-07-06 21:46

Those two pontoons in the drawing are scaled to 1 Liter plastic soda bottles, and will carry a surprising amount of weight.

The available Propulsion options for a water platform are staggering,
Anything from Propellers, to high power water pumps, and everything in between.
I have been leaning toward servo powered paddle wheels, as I have a small pond, and seems least likely to bother the fish..

-Tommy

GordonMcComb · 2012-07-08 09:04

As others have pointed out, the choice of caster depends on the specifics of the base. Comments on using one caster (with a two-wheeled bot when the wheels are center-lined) are spot-on, but don't forget that for a heavier bot you must have two for balance safety, and "teeter-tot" on one caster or the other. This can readily be done by adjusting the height of the casters relative to the drive wheels.

The (true) omnidirectional casters used in heavy furniture is an option. These have *rubber* wheels and were made for fine furniture. These were available from Italy in the early- to mid-2000s, but the company that patented and made them apparently went out of business. I notice someone in the UK has picked them up again, or at least something that looks very much like the Italian casters of yore:

http://www.omnitrack.co.uk/OB-m.php

The OC50, 55 and 100 are probably the ones you might want to sample. The ones I used were the OC55 and OC100. The latter were popular among R2-D2 builders, and were very rugged. All of these were made for ball-down use, and turn a true holonomic 360 without points of friction when changing direction.

Note about price: In low quantity, wholesale the OC55 was about $15, and the OC100 was around $25 or so. Probably more now, but that gives you an idea of how these will impact your retail price. They aren't cheap, but they won't require custom machining like the Madeusa/Eddie casters now do (which, BTW, are excellent).

-- Gordon

mindrobots · 2012-07-08 09:54

GordonMcComb wrote: »

...ball-down use, and turn a true holonomic 360 ...
-- Gordon

You truly have to admire a writer that can work those words into one sentence!! :thumb:

jdolecki · 2012-07-18 21:04

Round ones.

Thanks you I'll be here all week.

erco · 2012-07-18 22:27

W9GFO wrote: »

I'd like to see Parallax make some 5" or larger mecanum wheels. Just like the Vex ones but larger - and not green.

Larger and not green! http://www.andymark.com/Mecanum-s/53.htm

W9GFO · 2012-07-18 23:54

The standard 8" AndyMark mecanums are very noisy and are a bit "rough" in fit and finish. These add some outer rollers which is nice but I seriously doubt that they will match the ride quality, smoothness and noise level of the Vex mecanums. And wow, look at the price! They don't even have bearings!

erco · 2012-07-19 09:12

Check this old pic currently on Ebay of the mecanum wheel inventor with another of his award-winning inventions. Rubber Baby Buggy Bogies! A baby carriage with bogies for going up/down stairs!