How much pressure to lower ramp?

FIRST General Forum
1

Hello,

We’re a rookie team. It might be out there, but we can’t find the info for how much pressure it takes lower the ramp. Obviously, when lowering, it is w/out another robot on the ramp. The ramp, as we understand, is approx. 10.5 inches high.

All suggestions welcome.

2

idk where you got 10.5 inches…

2.2.5
Each Bridge is 48 in. wide, 88 in. long (outside dimensions), and sits with the top platform 12 in. high off the ground when level.

suggestion:
Read the manual.

3

First, a correction. According to section 2.2.5 of the Game Manual ("The Arena chapter), the bridges, when level, are 12 inches off the ground, not 10.5.

As for force, check out the video FIRST posted about the bridges here: www.youtube.com/watch?v=-AMaqqmoLgQ&feature=related

The use standard FRC batteries in a great demonstration of the tipping point, and you should be able to use that to figure out how much you need to push on it with your manipulator to get it to go down.

4

As started above the ramp is about 12inchs off the ground.
There is already a thread going on about this, search is your friend :wink:
But it takes about 16-18lbs of force to lower it from one edge with nothing on it.

5

900 inch pounds of torque is a reasonably close number and easy to remember.

2 * 15 lbs (batteries * 30 inches* off center = 900 inch lbs.

Some more quick math revels that 900/44 inches from center of bridge is about 20.5 lbs straight down on the bridge. Just remember to round up to be safe.

6

are you referring to the batteries as 15 lbs? because that is a little heavy :confused:

7

Easy to remember numbers and safe assumptions. :wink:

EDIT: im aware that the batteries are lighter, as well as their center of mass is closer to the 27.5 inch mark on the bridge.

8

I prefer accurate > easy

9

If you want a more accurate number, start with a better estimate of the batteries’ weight and location of their center of mass, and remember that the pivot point of the bridge is about 3.5 inches closer to its downward than the actual center.

10

if you look at the videos they talk about the force to balance the ramp. It takes about 760 in-lbs based on the two batteries used. If you work that out for the 44 inches to the end of the ramp that is about 17 lbs.