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View Full Version : Bottoming out on ramps?


flamefixed
01-20-2007, 10:35 PM
Apparently ramps are going to be very common this year. With this said, what are your ideas on how to prevent your alliance robot from catching their chassis on the corner of the ramp (the transition from sloping ramp to platform parallel to the ground). Our robot may have a simple middle wheel on each side raised sightly above the drive wheels which will work on any degree ramp (as long as the front wheel can get to it). Though, not all teams may incorporate something to get similar results. I was thinking a roller at the transition, but this isnt as simple as one can say. So your ideas??

Thanks....
Steve

JamesByrne
01-20-2007, 10:37 PM
ours is going to be high enough off the ground to make it up a ramp. As long as it is not extremely steep, i am not sure of the exact degree.

flamefixed
01-20-2007, 10:41 PM
16 degrees, give a take a degree.
I've just been reading how some are designing with a mere 2-3 inch ground clearance with a max climb angle of 14 or so.
Just want to make the bot is as universally adaptable and acceptable for everyones needs, 'cause you never really know what your going to get until your there.

Tom Bottiglieri
01-20-2007, 10:43 PM
We designed for a 30 degree ramp.

Ericgehrken
01-20-2007, 10:45 PM
Isn't that going to be very difficult for teams with compromised traction such as teams with omni wheels or swerve drives?
It shouldn't be a problem for teams with six wheel tank drives or tracks.

flamefixed
01-20-2007, 10:54 PM
Exactly. It will be hard, but ive worked up a pretty much slip resistant design for the ramps, its just that transition which we are all pretty stumped on

Scott358
01-20-2007, 11:09 PM
This is a very intersting point, especially as it relates to climbing 12" high ramps.

We're designing with 4" ground cleareance (in the center), which allows for a ramp as steep and high as last year (which happened to be 12" high). I forget the angle, but I believe it's a bit more than 30 degrees.

In the end, regardless of how you do it (ground clearance, skid pad, 6 wheel drive, etc...), you definately want to keep ramp climbing in mind (assuming you're not the ramp!).

MrForbes
01-20-2007, 11:19 PM
Exactly. It will be hard, but ive worked up a pretty much slip resistant design for the ramps, its just that transition which we are all pretty stumped on

There are some things you can do...the ramp can have a rounded or multi-angle transistion. Part of the platform could sit higher than 12", to make it easier to get on, and still keep the angled part of the ramp kind of short. Some commercially available motorcycle ramps (http://images.google.com/images?hl=en&q=motorcycle+ramps&btnG=Search+Images&nojs=1) are rounded near the top to ease the transition, see if you could copy the design.

K.Porter
01-20-2007, 11:22 PM
We've designed a 4 wheel drive system which is very much centered at the front of the robot, with the back being supported by casters. That way, even if we do bottom out we will be able to drag ourselves up a ramp with the front wheel drive.

As for our ramp, we have allowed for a shallower angle than last year's playing field, and we hope to round the top corner.

rocknthehawk
01-21-2007, 10:22 AM
Right now, our ramp is just under 17 degrees. Our 2005 bot had 2 inches of ground clearance and it seems to be able to climb it fine. We may change the design, so the angle will be closer to 13 or 14.

MrForbes
01-21-2007, 10:25 AM
we did a quick angle calculation last night, 11.5 degrees, but that is caused by some interesting geometry considerations in our tenative design.

T3_1565
01-21-2007, 10:45 AM
our robot is fairly low clearance, probably not enough you climb a ramp, but like perviously said we should be able to drag ourselves up with our front wheel drive, we are going to be lifting most of the time anyways, so maybe we wont have to

DDAwg3
01-21-2007, 11:46 AM
This reply is for rockahawk. If you were here, you would know that we have a1 1/2 clearance to the frame and the ramp is 17.13 deg. Whick is not less than 17. Knucklehead. :eek:

PVCMike
01-21-2007, 12:18 PM
Our ramp(s) wont have a "peak" or transition to go over....think about that!
:D

Dan Zollman
01-21-2007, 01:45 PM
Our ramp(s) wont have a "peak" or transition to go over....think about that!
:D

That's what I was thinking...
Why not use a curved ramp? A transitional ramp with an intermediate slope between the ramp and platform? Both would reduce the corner and make the transition easier.

MrForbes
01-21-2007, 01:55 PM
There are other things you can do, one is to make a ramp that is angled all the way up, with no horizontal part, although you might need some type of brake to keep the robot from rolling back down when power goes off at the buzzer. Or make a teeter-totter ramp, that is angled all the way up and when the robot gets past the tip point, it falls back level.

flamefixed
01-21-2007, 04:58 PM
Thanks for all the advice! Any other ideas out there? (Just trying to get a good, well-rounded consensus)

Brian C
01-22-2007, 12:30 AM
Don't forget the fact that some teams will be using bumpers and some teams will not.

All else being equal those that eschew bumpers (us included) will have less issues with ramp bottoming than those that use bumpers. There were quite a few teams last year that discovered late in the build that the bumper added a whole new wrinkle when it came to maneuvering up the 30 degree incline.

MrForbes
01-22-2007, 12:38 AM
OT:

ok, why is it that when we're talking about ramps, bottoming out, and bumpers, there are two guys with hot rods in their avatars in the discussion?

Brian C
01-23-2007, 10:15 AM
HA!

That's 'cause all us hot rod guys like working with mechanical things and robots fill that void during the cold months. I just wish the deuce was really mine........

Seriously, bumpers are sometimes a second thought with teams. The 30 dedgree ramp last year stumped quite a few people. We striving for 20 degrees or less to accomodate the majority.

rocknthehawk
01-23-2007, 02:34 PM
OT: I'm going to WyoTech in June for STREET ROD FAB. sweeeet....

Eric Scheuing
01-23-2007, 03:12 PM
If you had no problems last year ramping, why not just design a similar drive train?

Curt Henderson
01-26-2007, 12:36 PM
We've designed a 4 wheel drive system which is very much centered at the front of the robot, with the back being supported by casters. That way, even if we do bottom out we will be able to drag ourselves up a ramp with the front wheel drive.

As for our ramp, we have allowed for a shallower angle than last year's playing field, and we hope to round the top corner.

If I understand your idea correctly, it should work if the center of gravity of your robot is balanced over your drive wheels to maintain contact with the top ramp surface. Otherwise you may find yourselves grounded on the ramp with your drive wheels in the air as the CG of your robots shifts to the back wheels when you go up the ramp.

Should this happen, you can always go up the ramp in reverse.

Good Luck!

Martinez
01-26-2007, 01:16 PM
This is the number one reason I think ramps are a bad idea. There will be plenty of teams who won't or can't climb a ramp. Its a great thing for most alliances but this really is something you have to design around. I feel that if you are going to come up with a way to lift robots: than it should be universally compatable for as close to everyone as you can, not the other way around. Aside from that, 2" or 15 degress seems rather popular.

cgredalertcc
01-26-2007, 01:44 PM
people building ramps need to take into account that other teams aren't building their robots to accomodate ramps. This is the reason 1741 chose to go with a lifting system. My recomendation is if your ramp is greater than 2 inches tall it better have a slope less than 20 degrees, or else no one is getting on.

DKolberg
01-26-2007, 03:16 PM
Our ramp will be about 8.5 degrees so everyone should be able to go up it with very little trouble. Robots wider than 40" need not apply.:D See you at the tournaments.

Dave

Elpants
01-27-2007, 03:12 AM
Our bot completely folds up to 13" tall 26" wide and 37" long arm and all enclosed.

With the smaller wheels this year most teams I suspect will have a lower ground clearence. I was playing around on a white board with scale drawings to see the best kind of angle our ramp should be. As it is right now our own bot (with a ground clearence of 2 3/8" cannot even make it up our own ramp that I have drawn up for inventor with-out high centering on the corner..

Our deadline for a working chassis with arm is to be finished tomorrow, all our programming was getting finished up last night. So I need a general average of ground clearence so I can design our to accomidate the average team. (That, or I hope a lot of teams have 6wd/treads :yikes: )

1768
01-27-2007, 09:56 AM
In the end, regardless of how you do it (ground clearance, skid pad, 6 wheel drive, etc...), you definately want to keep ramp climbing in mind (assuming you're not the ramp!).

Given the abundance of ramps, keep ramp climbing in mind even if you ARE the ramp. e expect to be on at least one team where the entire team is ramp-bots, so we are designing to climb a ramp and be a ramp low-clearance bots can climb.

MrForbes
01-27-2007, 10:07 AM
Our bot completely folds up to 13" tall 26" wide and 37" long arm and all enclosed.

Have you considered the implications of rule <G29> on the starting configuration of this design?

Elpants
01-27-2007, 12:00 PM
Have you considered the implications of rule <G29> on the starting configuration of this design?


I guess I should be more specific, this is w/o a ramp and all electronics and drivetrain within these dimentions, just stating that with a plateform height of 13" its getting hard to create a ramp that is under 4' tall and wont have a problem for our own bot to get up w/o getting a running start.

our height changes, at the end of the game, the robot is 13"tall.

MrForbes
01-27-2007, 12:03 PM
Thanks for the clarification. Yes, it is a tough design problem, I hope you can find a way to solve it.

Jared Russell
01-28-2007, 08:30 PM
Last year's ramp was at 30 degrees, and covered with diamond plate (one of the worst traction surfaces for most robot wheels). Still, most teams could make it up.

This year, I've not heard of a ramp that is more than 30 degrees, and I'm sure that ramp bots will use something a little more tacky for the driving surface. So I wouldn't be overly concerned.

Plus, if you drive fast enough, you WILL get up anything :D

cgredalertcc
01-28-2007, 09:03 PM
Plus, if you drive fast enough, you WILL get up anything :D

wow can you say robot parts everywhere....

The GarbageMan
01-28-2007, 10:46 PM
Our robot will have a 20 dregree (from horizontal) ramp. That means any robot with a 2" or more ground clearace will not bottom out on the ramp.

Trample-Bot
01-29-2007, 11:50 AM
we plan to have our wheels almost sticking outside of our chassis, so we should be able to handle any degree, and hopefully not bog out

nukemknight
01-29-2007, 11:57 AM
Our ramp will be about 8.5 degrees so everyone should be able to go up it with very little trouble. Robots wider than 40" need not apply.:D See you at the tournaments.

Dave

This is the smallest degree posted on this thread so far. Has anyone figured out a way to get any lower?