Ramp Angle Survey

[GaryVoshol]

Originally Posted by Dan Swando

It's reasonable to assume that most robots this year with have a higher CG than last year.

How do you figger, Dan? This year's robots won't have a heavy shooter up on top. (OK, some robots had their shooter mounted low, but most were high.) I presume whatever ring-handling mechanism you have will be less massive than a shooter, could be folded up into its starting configuration when going up a ramp.

I'm not saying it's a trivial matter. I just think it will be easier this year, as long as you plan ahead. There's heavy stuff you need (battery, drivetrain, [optional] pneumatics) that you can put in your base which can counterbalance your vertical mechanism.

If you're going for a fixed 6-foot design, you would have more tipping issues.

The original poster is correct in considering the approach angle problem (and don't forget the trailing angle as well). Bumpers hang out significantly from your wheelbase - don't forget them in your calculations. I certainly hope we don't see any of the leading-angle-trimmed-off bumpers that some competitions allowed last year. That's not fair to those teams that follow the rules.

[DjAlamose]

If you have a robot with 4wd tank steering and a 30" wheel base, the maximum ramp angle you can achieve before you bottom out (with 2" ground clearance) is only a 7 degree ramp! (This is looking at when the robot gets to the top of the ramp and is going over that corner).

This is obviously a round about number and i didn't do any special calculations for it, but still it gets the point across.

So, you would need a ground clearance of about 4.3" if the ramp was 16 degrees (the angle I have been looking at for a ramp design). Again this is 30' wheel base and 4wd.

To make getting up a ramp easy, just make your robot 6wd and you should have no problems.

By the way, does anyone know the angle of the ramp 111 (wildstang) used in their 2001 robot?


Edit:

Oh, and if your robot's CG is 48 inches above the ground and in the middle of your robot (with your robot orientated so it drives where the short side is the front), you would tip over if you attempted a ramp of 18 degrees or more. I highly doubt that any robot will have a CG at 48 inches but I always look at worst case cenario.

P.S.
Please correct me if im wrong. I did these calculations in about 10 seconds using simple triangles.

[Ianworld]

The real issue with getting up ramps is as the above posters have pointed out is getting hung up as you go up over the top. The best solution for this is really just making a 6 wheel robot. There are very, very few situations where a 6 wheel robot going pretty straight up a ramp can get stuck. The reason is that the center of gravity or balance point of the robot is over a wheel. If the robot is caught on one of the points between the wheels it will usually tip to one of its wheels and maintain traction.

[Brandon Holley]

If your going to have a ramp, it is quite feasable to build one with a small degree....you have 4 feet of height to work with (in the highest weight class)

[DjAlamose]

asin(12/48)=14.47751218592992 deg
This is the smallest angle that you can acheive without doing any extentions.
Also, this really isn't feasable because you wont be able to get that 48" long piece, you would need some ground clearance.

So what I've been using:

asin(13/45)=16.79144711458869 deg

13 because I want to make sure that we get that 30 and not 15 for being 11.8" above the ground, and 45 because it gives a 3" ground clearance.

[Brandon Holley]

hmmm...i was thinking more along the lines of not one solid piece of metal, maybe your ramp has a joint????

[Ericgehrken]

How about a ramp on a 20 degree angle. If you want your robot to be lifted then please be able to drive up an incline of at least 20 degrees.

[DjAlamose]

Originally Posted by MORT~11

hmmm...i was thinking more along the lines of not one solid piece of metal, maybe your ramp has a joint????

Nope, one solid piece. Of corse this is still in design and we aren't even sure this is the route we want to take.

Oh, and by the way, a sheet of aluminum diamond plate 24x48x(1/16) weighs only 7.056 lbs (yeah thats alot of weight, but holes can be drilled....Lots of holes....)

[WeldedHarlequin]

Originally Posted by DjAlamose

Nope, one solid piece. Of corse this is still in design and we aren't even sure this is the route we want to take.

Oh, and by the way, a sheet of aluminum diamond plate 24x48x(1/16) weighs only 7.056 lbs (yeah thats alot of weight, but holes can be drilled....Lots of holes....)

Do you know how many quarter-inch holes you would have to drill in a sheet of diamond-plate to significantly reduce the weight?

Lots and Lots.

Keep in mind that all those holes will reduce the structural strength as well. I'm sure nobody wants to see their robot fall through a ramp...

[GaryVoshol]

Originally Posted by DjAlamose

... 13 because I want to make sure that we get that 30 and not 15 for being 11.8" above the ground, and 45 because it gives a 3" ground clearance.

What about bumper clearance?

[DjAlamose]

Originally Posted by GaryV1188

What about bumper clearance?

Rule R37 comes into play.

STANDARD BUMPERS must remain within the BUMPER ZONE when the ROBOT is resting on the floor in PLAYING CONFIGURATION. They can not be articulated or moved outside of the BUMPER ZONE. The one exception to this is STANDARD BUMPERS may be within or below the BUMPER ZONE during the END GAME if the ROBOT is in its HOME ZONE (see Figure 8-3).

So durring end game, they just fold down and out of the way.

[Assassin Shadow]

Forgive me if I'm wrong, but does it really matter whether the robot is up past the ramp. It doesn't have to be past the corner at the top of the ramp to earn points, it just has to be at least 4 inches up the ramp. So in a worst case scenario, just make it so that your robot can make it that far up a ramp and then turn a little sideways so that they don't roll back down. Viola!

[KTorak]

Originally Posted by Assassin Shadow

Forgive me if I'm wrong, but does it really matter whether the robot is up past the ramp. It doesn't have to be past the corner at the top of the ramp to earn points, it just has to be at least 4 inches up the ramp. So in a worst case scenario, just make it so that your robot can make it that far up a ramp and then turn a little sideways so that they don't roll back down. Viola!

However, as seen last year, your robot must be able to sustain its final position for up to 30 seconds or more while scoring takes place. Therefore, if you are not over the apex of the ramp, you will fall off and you most likely will not receive the points. But, this is probably Q&A material.

[DonRotolo]

Originally Posted by Assassin Shadow

Forgive me if I'm wrong, but does it really matter whether the robot is up past the ramp. It doesn't have to be past the corner at the top of the ramp to earn points, it just has to be at least 4 inches up the ramp. So in a worst case scenario, just make it so that your robot can make it that far up a ramp and then turn a little sideways so that they don't roll back down. Viola!

4" up the ramp is NOT the same as 4" from the floor.
Many robots will roll when powered down. You'd have to turn sideways to be sure you don't roll. Do you want another robot turning atop yours? I don't


We are thinking of an 8" tall robot with a 36" long ramp, Sin (8/36) = ~13 degrees.

Don

[Bongle]

Originally Posted by Don Rotolo

Do you want another robot turning atop yours? I don't

That's really a moot point. From driving previous robots, I've noticed that motor stall and joystick sensitivity at low speeds is a BIG issue. Since I imagine you don't want robots climbing at high speeds, then you're going to be dealing with robots turning on your robot no matter what.

I think it a plausible sequence would be like this:
-Team is driving very slowly up skinny ramp
-Team stops to make sure orientation is good
-Team attempts to continue at low speeds, but one side un-stalls first, causing the robot to rotate. They now either have to deliberately rotate, drive off and try again, or just give up and hope they reached 4".

Which makes me realize that painted-on markings for vertical displacement of 4" and 12" on any given ramp would be a very good idea. Also, having your ramp removeable between matches would be good. Who wants a 4ft ramp above their heads if they know before their match that they'll be climbing an partner's ramp?

Keep in mind that all those holes will reduce the structural strength as well. I'm sure nobody wants to see their robot fall through a ramp...

Your ramp certainly doesn't have to be a flat piece of metal. You could probably get away with a honeycomb-like bit of metal supported by some posts, with thin carpet on top.