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Unread 01-10-2018, 09:39 AM
AMDcats AMDcats is offline
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How to design a rampbot

I am a rookie and my team was thinking of designing a ramp bot. However at a 15 degree slope then each ramp would be 7 feet long. I was going with 15 since that is the angle of the ramp up to the platform and I know that robots can get on it. However, this would be incredibly heavy due to the length. I was wondering if anybody knows what the highest slope that almost all robots can drive up. In 2007 there were robots seeming to go up 45 degree slopes, but I do not want to rely on that height.
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Unread 01-10-2018, 09:48 AM
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Re: How to design a rampbot

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Originally Posted by AMDcats View Post
I am a rookie and my team was thinking of designing a ramp bot. However at a 15 degree slope then each ramp would be 7 feet long. I was going with 15 since that is the angle of the ramp up to the platform and I know that robots can get on it. However, this would be incredibly heavy due to the length. I was wondering if anybody knows what the highest slope that almost all robots can drive up. In 2007 there were robots seeming to go up 45 degree slopes, but I do not want to rely on that height.
Id check your math again. 7ft doesn't seem right to me......Im getting something closer to 45 inches of horizontal.... 12/tan(15)......
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Unread 01-10-2018, 09:49 AM
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In 2007 a lot of teams built their robots while keeping in mind having to drive up other peoples ramps. This year, the story may be different. While trying to make ramps this year, our team realized that the packaging for ramps for two robots that are max size was gong to be difficult. Instead, we are attempting to make a flat platform that drops down over the bumpers and lifts the other robot while we climb like a forklift. This way, the system is light, simple, and allows us more room for our arm.


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Unread 01-10-2018, 09:50 AM
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Re: How to design a rampbot

Keep in mind that no matter how big you make your ramp, it needs to be entirely supported by the Scale. With a 7 foot long structure, any flex in your materials will likely bend down and touch the carpet... Just a thought.

Also, as a rookie take the best advice I ever got:
1. RTFM
2. You know that clever thing? Don't do that. It's ok to take risks if you think everything through, but if your CAD looks like an Inspector Gadget cartoon, its time to slow down...
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Unread 01-10-2018, 09:50 AM
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Re: How to design a rampbot

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Originally Posted by AMDcats View Post
I was wondering if anybody knows what the highest slope that almost all robots can drive up.
No. No one knows the highest slope that almost all robots can drive up.

However:
Most robots will be designed to drive on carpet.
Some robots will have a long drive base, some robots will have a wide drive base.
Some robots won't be able to drive up even the ramps on the field.
Some robots will be fully loaded (120 lbs + battery + bumpers + game piece).

Hope this helps.
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Unread 01-10-2018, 09:51 AM
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Re: How to design a rampbot

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Originally Posted by pKlopp View Post
In 2007 a lot of teams built their robots while keeping in mind having to drive up other peoples ramps. This year, the story may be different. While trying to make ramps this year, our team realized that the packaging for ramps for two robots that are max size was gong to be difficult. Instead, we are attempting to make a flat platform that drops down over the bumpers and lifts the other robot while we climb like a forklift. This way, the system is light, simple, and allows us more room for our arm.


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So your robot will be climbing from the rung and lifting them with? Or will have forklift mechanisms on each side to lift them while you stay on the platform?
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Unread 01-10-2018, 09:51 AM
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Re: How to design a rampbot

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Originally Posted by AMDcats View Post
I am a rookie and my team was thinking of designing a ramp bot. However at a 15 degree slope then each ramp would be 7 feet long. I was going with 15 since that is the angle of the ramp up to the platform and I know that robots can get on it. However, this would be incredibly heavy due to the length. I was wondering if anybody knows what the highest slope that almost all robots can drive up. In 2007 there were robots seeming to go up 45 degree slopes, but I do not want to rely on that height.
The way it seems, everybody and their brother will have a Ramp Bot this year... I highly recommend, being that you're a rookie team, to ask yourself if you can still have an effective Switch manipulator if you have Ramp Bot capabilities. If the answer is yes, awesome! If the answer is no, or you think your Switch capabilities will be reduced/diminished, then I would say to focus on building a robot that can successfully accomplish scoring in the Switch at a high level.

Regardless of the above answer, I would suggest that you build a robot that is capable of driving onto a Ramp Bot. Tippy robot is bad. Low clearance robot is bad.
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Unread 01-10-2018, 09:55 AM
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Re: How to design a rampbot

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Originally Posted by AMDcats View Post
I was wondering if anybody knows what the highest slope that almost all robots can drive up. In 2007 there were robots seeming to go up 45 degree slopes, but I do not want to rely on that height.
No, slope would depend on many factors, some are weight, wheel choice, and center of gravity.
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Unread 01-10-2018, 10:19 AM
AMDcats AMDcats is offline
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Re: How to design a rampbot

Would it be a better idea to use a forklift and then gear the drivetrain motors so that they disengage and raise two robots, one on either side?
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Unread 01-10-2018, 10:22 AM
efoote868 efoote868 is offline
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Re: How to design a rampbot

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Originally Posted by AMDcats View Post
Would it be a better idea to use a forklift and then gear the drivetrain motors so that they disengage and raise two robots, one on either side?
Not every robot will use the same number / size wheels. Some robots will have 4 wheels, some will have 6, some will have 8. There may be a robot or two with more than that, or less!

Some robots will be wide, some will be long. Some robots will have lots of ground clearance. Some robots won't have much ground clearance at all.

Some robots may have frame cutouts that you won't be able to lift.

...

There are pros and cons to every design choice. Keep thinking about it!


EDIT:
Here's some inspiration for you. Maybe do a combination, like Team 1501 from 2007.
http://huntingtonrobotics.org/wp-con...2007-robot.jpg
https://www.youtube.com/watch?v=RHx9IC1W9wQ

Last edited by efoote868 : 01-10-2018 at 10:25 AM.
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Unread 01-10-2018, 12:17 PM
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Re: How to design a rampbot

Like some others have said make sure you can do switch and be effective at that before trying to take on a ramp. In theory ramp seams easy and simple but, it has lots of factor's. A ramp will be the hardest for robots to drive up on. my team is considering making an elevator for the other two teams or having a ramp another team can drive on then we lift up the two of us
in the air and use levitate on the third.
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Unread 01-10-2018, 12:53 PM
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Re: How to design a rampbot

There are many factors that play into exactly how steep of a ramp a given robot can climb. The coeffecient of friction between the ramp and the robots wheels is a factor as well as the weight distribution of said robot will determine the greatest angle that it will climb. However the robot has to get its wheels on the ramp first for that to matter. So the real question is what are the approach, departure and break over angles of the robot that is doing the climbing.

So yesterday we did some testing with last year's robot and a sheet of plywood blocked up at different angles.

Our robot is an AM14U3 in the "square" configuration wheel base and the bumpers were set so that they had about 1/2" of ground clearance. We were able to get up a ~22.5 degree ramp like that. Then we removed the bumpers and tried again with a nominal 2 1/4" ground clearance. With that configuration the lower approach angle allowed us to climb a ~33 degree ramp.

We then did a check on the break over angle and with our configuration you needed much more than that ~147 degree angle to cause it to high center and in fact the belt was the first thing that would touch so it would actually still provide at least some motive power.

Unfortunately we only have that one robot to test and all of the following factors will affect the approach/departure angles. Wheel base, overhang (the distance between the point where the wheel touches the ground and the effective end of the robot), and ground clearance at the front and rear, the maximum of which is determined by the bumper rules this year. Break over angle will be determined by the distance between the sets of wheels and the ground clearance between each of those sets of wheels.
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