The afterthought bridge manipulator

[Superllama12]

We were using a piston to push down the bridge, but it ended up not working because we did not have enough weight for a compressor. It definitely would have helped us at regionals, and ended up being even more important than we had expected (and we had thought it would be a very big deciding factor). We had planned for going over the bump with an eight-wheel drive system, but we kept getting caught on the frame when trying to. Maybe it was just our regional, but I never really saw anyone with a strategy that hinged on getting over the bump, except for occasionally dodging people playing defense on their side of the ramp. During the offseason, though, we will be working on the bridge mechanism.

[Sean Raia]

I want to thank everyone who contributed to this thread. Due to the suggestions given, we were able to construct a working bridge manipulator quite quickly.

Chief Delphi has come through for a team yet again!

[DavidGitz]

Originally Posted by SenorZ

Our regional is next week. After watching weeks 1 & 2 we're scrambling to make a bridge manipulator:
Andymark gearmotor (KOP) on a length of c-channel with a small wheel on the end.
This is untested and will not get a chance until Thursday.
Fingers crossed!

Or use 2 andymark motors.

[Wetzel]

We made a simple static manipulator that was originally designed to only LIFT the bridge, but it turned out we were able to knock it down and get on as well. Works well enough we were picked by the 2nd seed in DC and were able to win the regional. 4.5 lbs.

I don't have a picture with me, but come find us in St Louis and I can show you in person.

Wetzel

[JewishDan18]

Team 20 had the same issue; our first design pushed down with 1 pound of force *facepalm*. It took 5 iterations, but our current design pushes down with over 140 pounds, weighs 3.5 pounds, and allows us to ram the bridge to lower it

[gracie.]

this weekend we're at the queen city regional. thanks to the amazing mechanical team we've just installed a new "ramp smacker" to lower the bridge after practice matches today. we're using a window motor and are hoping that a big gear ratio and some braces will give us the power and stability we need to push down the ramp. I'm putting on limit switches tomorrow morning and we should be fully functional!!! i've heard of all sorts of problems with the window motors, and we've had some of our own, but i'm thinking this could be a final solution.

[JohnSchneider]

Youd be surprised at the power of a winch...

I will say 100lbs of force more than brings down the bridge.

[Borobo]

what I would do is pair your window motors in a winch and pull down the arm via cable. that's what we're doing and it works great. I spend the first day of our regional perfecting the 3d 4 bar inverted ramp we had designed, only to run into problems. Instead I put together the winch arm design in a total of half an hour. It is super reliable and we can easily crush balls caught under the bridge.

[philso]

We had our winch driven arm tested in our garage last night. Today, it ended up with the motor wired up to the Spike in the wrong direction. The resultant 400 ftlb of torque turned both of the two #10 stainless steel screws pinning the home-made hubs on the pulley and the arm to the shaft into "subtle s-shapes" that had to be drilled out to get it all apart to be repaired. The other team members were amazed that the 3mm diameter Dyneema cord held up to this abuse. Its breaking strength is rated at something like 1950 pounds. We will rebuild it tomorrow with bigger bolts and a better hub design, if possible.

[JohnSchneider]

Originally Posted by Borobo

what I would do is pair your window motors in a winch and pull down the arm via cable. that's what we're doing and it works great. I spend the first day of our regional perfecting the 3d 4 bar inverted ramp we had designed, only to run into problems. Instead I put together the winch arm design in a total of half an hour. It is super reliable and we can easily crush balls caught under the bridge.

Were just using a single window motor. It all depends on your pulley size...but the force you can get from one of them is plenty. We probably have had one of the most consistent bridge pull downs at each of our regionals. Sometimes people dont think simply enough

Our coach and several members on our team were watching Week 1 matches when we started to realize just how important the bridge was. A bridge could determine who was the winner and who was ranked higher.

Our team ended up adding an "arm" after trying to balance on the bridge we made. It was originally simple with some 80-20 and a doorstop to act as a kind of brake. By the time our design team came up with the idea all the electronics had been placed and we spent some time having to rearrange when everything went since the arm would come down on the power distribution board. This was a few days before bag n tag.

It worked out well at competition and we were satisfied with how the arm worked, but a few students on our team came up with an attachment on the arm (pneumatic) to help us triple balance better (we had five pounds of weight to play with). The idea was good, but when we tried to practice balancing with it it wasn't very effective. I think our drive team used it at competitions, but not as much as we expected.

Overall, I'm glad we made the changes we did, otherwise we probably wouldn't be as successful.