Re: How can we drive on this new floor?
 

I have one, the fan in the link draws 8a of current and the hardware we have can only take 3/4a. Also I am thinking that there is little way of creating enough force to hold the robot to the Crater. One of my team mates did the math and estimated that you will need to move over 900 cubic feet of air per minute :). It might very well be possible to use a fan to create more downforce, I know it has been done in racing, but the question is going to be one of how much weight can you spare to add it in, how much room do you have for it, and more importantly can you spare that mush energy from your system to power it and all the other essential items.

Re: How can we drive on this new floor?
 

The post was meant to point out to specific people. ;)

Nevertheless, touche.

Re: How can we drive on this new floor?
 

Eh, figure it's time to stick my nose in here.

Anyway, Titan's idea about augmenting the robot's downward force is an interesting one. Keep working on that, you really could have something there.

Folks, FIRST just took the box we've all been thinking in and ripped it to pieces. Even a kit chassis is stuck in the high traction environment we've had. It's time to shed all these ideas of how we used to move, and really DESIGN around CONSTRAINTS, much the way the real world works. What you're all seeing and experiencing is a valuable skill, so don't blow this one off.

That being said, I have absolutely NO idea what to advise my team to do... I've spent all of today doing different designs, all of which end halfway when I realize different factors.

Re: How can we drive on this new floor?
 

We bought two 4' x 8' sheets of that "ice" material ($30 per sheet) for the floor and did some testing. We compared traction on the "ice" the carpet and plain old tiled floor. The ice was the slickest. The carpet was slick but not as bad. The tile was surprisingly almost the same as the ice. So, to answer your question, if you cannot afford to buy some of the ice material, use a tiled floor as your best simulation.

Re: How can we drive on this new floor?
 

Many teams used 4 CIMS for their drivetrain in past competitions. It seems that 2 CIMS would be sufficient to drive the wheels this year. How much more traction would you get from 2 CIMS driving fans? what if the fans were used for purplusion instead? i.e. like an airboat.

Re: How can we drive on this new floor?
 

Did you collect and numbers to help us compare?
I was thinking that we might stretch a large sheet of plastic over a tile floor and tape down the edges. If the plastic is thick enough, hopefully the robot will not wrinkle and tear it long enough to practice.

Re: How can we drive on this new floor?
 

hahaha, I do love these propulsion ideas.

But i think that teams are making this much tougher for themselves by not looking at what by some people has been described and explained to me as simple physics. Why make it harder on yourself by making that hypothetical propulsion robot? Think of the new challenges you create for yourself. A part of engineering, as what I've been taught by my grandfather, is not only creating solutions, but moving closer to the obstacles at hand, and not creating new ones for yourself.

Sure propulsion would be innovative in an FRC robot, sure it'd be tons of fun, but look at the new challenges you're bringing up for your own team. How would this effect the physics of you carrying the trailer? When you turn, the inertia of that trailer will lead you into a corner with propulsion. A hybrid of propulsion and wheels is almost useless even if it is deemed allowed (which by the "no other traction on the field allowed" part of the rules can't be done anyway).

Ranting aside, my point is just for teams to think more clearly in their ideas. I'm not an engineer so I'm not saying you even have to listen to me or consider my advice, just don't create new obstacles for yourselves.

Yup Sean, it looks possible. I've gone over the CoF with a lot of people and depending on the orientation of your wheels, you could in theory do a Kiwi type holonomic drive. I'd rather test it out though.

Re: How can we drive on this new floor?
 

So does anyone want to chime in about using these wheels as omniwheels. Would it even be possible. I am feeling slightly lost since all of my preseason designs involved mega-traction and multi-speed high torque transmissions

Re: How can we drive on this new floor?
 

So Zyck_titan it seems you had the same idea I did... >.< and I thought I was original.

We did the math and with a 480 watt (the maximum wattage motor allowable) you could produce just under .2 psi. (allow variance for rotor blade type) Numbers for this were taken from a website publishing the Static Pressure capabilities of their 480 watt fans. (we then did conversions to psi)

Now you have to multiply by the square inches (maximum allowable 1064 = 28x38) and we get about 213 pounds of extra force.

So if you had a skirt around the entirety of your robot you could conservativly expect to roughly double the weight/normal force of your robot. (you'd lose a lot due to inefficiencies)

This means that when applied to F=MA in regards to your acceleration you can expect to take it from roughly .6 m/s (static friction with no fans) to 1.2-1.5 m/s (static friction with fans)

Now logistics might be a tad tough but hey if it gives you double your friction then it's worth it in my book. The real problem... ripping up the play area. If it isn't secured you would just vacuum it up and be completely stuck. This seems a real problem to me since when you look here ( http://thebluealliance.tumblr.com/po...field-elements ) at the end you can see the edge of the field which is merely secured with TAPE and now if this is a thin linoleum style roll you would just suck it right up and then... you wouldn't be able to move and might even get a penalty for destroying the field.

...after further research ( http://www.frpshop.com/pdf/installat...structions.pdf ) assuming FIRST followed these rules for the construction of a gasolenar frp floor it might not be too much of a problem...

Re: How can we drive on this new floor?
 

Omniwheels are specifically designed to have a lower coefficient of friction in the transverse direction than in the inline direction.

These wheels, according to the manual, have a transverse coefficient of friction that is about twice that of the inline direction. They are, by my reading... anti-omni wheels.

Jason

Re: How can we drive on this new floor?
 

I agree

Re: How can we drive on this new floor?
 

The coefficient of transverse static (or kinetic for that matter) friction is significantly higher than the Inline coefficients of friction. I can't help but imagine that some use could be had from the transverse friction.
The the higher friction could be used to create a centripetal force to assist in turning, which would require that the wheels rotate.
Or, a foot could be made from a perpendicularly positioned wheel, and use the transverse coefficient of friction to help stop the robot. Would that be legal?

Re: How can we drive on this new floor?
 

It doesn't make sense to me why one would be higher than the other the wheels are molded and don't have any sort of "stepping" that would cause this ... any idea as to why one would be greater than the other?

Re: How can we drive on this new floor?
 

Did you do any testing on terrazzo floors? (The stuff where a slurry is poured, and then polished after it hardens)

Re: How can we drive on this new floor?
 

Alot of people's response to this problem reminds me of an exercise we had to do at a workshop that work had us do to advocate thinking outside of the box. They had us put up our hand and the guy would push it. Of course out of reflex we would resist. And he asked us why we resisted? Because it our habit to do so. Sometimes instead of just resiting the forces that are working against you is to loosen your control and work with those forces and allow them to do the steering.
Seems to me what people have the biggest problem here with is being in complete control of their robot and are trying to come up with every possible solution to regain that control when maybe the best solution is to embrace the lack of control and use it to the advantage like the guys who suggest the drifting training. You could waste alot of time and energy otherwise.