Bumper Attachment for Rapid Removal

[Dale]

I know the rules could change for the 2010 game but I'd be interested in what systems teams have used to facilitate rapid attachment and removal of bumpers.

We've always put threaded inserts inside the bumper and then bolted them onto brackets on the frame. This seems simple enough but given the cramped quarters inside the robot and subtle alignment issues it can be a tedious 30 minute job to take the bumpers on and off for weighing.

There has to be a better way? Care to share pictures or descriptions?

[MrForbes]

We had a nice setup in 2008 using fanged elevator bolts (from McMaster Carr) in the bumpers, and coupling nuts to hold them on. And we even made the bumpers well enough that we can use either side bumper on either side, and either end bumper on either end. Too bad we couldn't make it work so well on the 2009 robot. And too bad I didn't get good pictures of it.

[Ryan Foley]

Dale,

Here is what FRC1995 used last year. There were two of these mechanisms at the top of each bumper. There was also another piece of aluminum-angle mounted on the bottom of the bumper. This lower piece has holes at either end, which would slip over fixed-mounted bolts on the lower side of the drive frame.

The upper mechanisms were activated by hand. By pushing down (1st picture) the white block with bolts would lower, leaving room for the bumper's aluminum angle to be inserted so it is just below the upper lip of the drive frame. By releasing the mechanism, the spring will push the assembly up, inserting the two locking bolts through the bumper aluminum angle and through holes in the drive frame. This locks the bumper in place. You can see the mechanism closed in the 2nd picture. Sorry, I don't have a good closeup of the lower aluminum angle.

These mechanisms worked fairly well for us in the 2009 season. Unfortunately we were behind schedule, so the mechanisms, while planned from mid-season, were built last minute. Better fabrication would help these perform better.

[jamie_1930]

Originally Posted by Ryan Foley

Dale,

Here is what FRC1995 used last year. There were two of these mechanisms at the top of each bumper. There was also another piece of aluminum-angle mounted on the bottom of the bumper. This lower piece has holes at either end, which would slip over fixed-mounted bolts on the lower side of the drive frame.

The upper mechanisms were activated by hand. By pushing down (1st picture) the white block with bolts would lower, leaving room for the bumper's aluminum angle to be inserted so it is just below the upper lip of the drive frame. By releasing the mechanism, the spring will push the assembly up, inserting the two locking bolts through the bumper aluminum angle and through holes in the drive frame. This locks the bumper in place. You can see the mechanism closed in the 2nd picture. Sorry, I don't have a good closeup of the lower aluminum angle.

These mechanisms worked fairly well for us in the 2009 season. Unfortunately we were behind schedule, so the mechanisms, while planned from mid-season, were built last minute. Better fabrication would help these perform better.

Ok I think I'll say it first, is it ok with you guys if every single team in FRC takes this idea?

[Trent B]

RC gave me this idea.

this is your frame []

This is your bumper |[ with the [ being two pieces of aluminum angle spaced as far apart as your frame is tall.

You line it up like this |[[]

The aluminum angle slides over the frame.

Drill holes in both at regular intervals and tap the holes in the frame, should make it easy enough to attach with a screwdriver.

[Tom Line]

Originally Posted by Trent B

RC gave me this idea.

this is your frame []

This is your bumper |[ with the [ being two pieces of aluminum angle spaced as far apart as your frame is tall.

You line it up like this |[[]

The aluminum angle slides over the frame.

Drill holes in both at regular intervals and tap the holes in the frame, should make it easy enough to attach with a screwdriver.

This is what we did - purchased steel U channel that fit over our frame (perfectly). Then we drilled holes vertically with the bumpers on and dropped 3/16" quick pins in (bolts work fine - no need to thread or put a nut on, friction will keep them in just fine). This got us our "backing member", and got us within a 1/2 pound of max bumper weight which is where we wanted to be.

[R.C.]

Originally Posted by Trent B

RC gave me this idea.

this is your frame []

This is your bumper |[ with the [ being two pieces of aluminum angle spaced as far apart as your frame is tall.

You line it up like this |[[]

The aluminum angle slides over the frame.

Drill holes in both at regular intervals and tap the holes in the frame, should make it easy enough to attach with a screwdriver.

Thanks Trent,

Here's an image that shows the holes made out, the piece of aluminum angle sits on top and you can either bolt or rivet

http://picasaweb.google.com/rcthekid...26173247025970

-RC

[Jared Russell]

We usually build our chassis with Bosch-Rexroth aluminum extrusion (20mm profile in recent years), so we outfit our bumpers to take advantage of the T slots in the extrusion.

The bumpers have bolts put into them (head side out). We usually mill out the sides of the channel at the top of vertical members (in the corners of the chassis) so that there's a place to insert and remove the bolt heads. All you have to do to add or remove a bumper is to put the bolt heads through the hole and slide them down into place.

[sanddrag]

We took some 3/8" 7075 aluminum rod and drilled and tapped one end. Then we put a chamfer on the other end and drilled a transverse through hole. These became our "bumper pins" these were screwed to a 1/8" metal plate, abut 1/2" wide and 2" long with three holes, one for the pin, and two to screw it to the wood in the bumper. We 4 of these sticking out of the bumpers on either side of the robot. They would go through 7/16" holes in the frame, and then hitch pin clips were placed through the transverse holes to secure it. Then we used a tee nut in each end bumper piece (the small front and back bumpers) with a 3/8-16 knob bolt to secure it. The end bumper pieces were attatched internally to the sides, with aluminum angle.

[skimoose]

Team 228 turned aluminum pins which were inserted into holes in the frame and held to the frame with hairpin cotter pins from McMaster. The bumpers were held onto the pins with larger hairpin cotter pins as can be seen in this photo:



The bumper brackets were 0.125" aluminum angle bored to the OD of the pins on one flange and bored for deckmate screws into the bumper plywood. This system only required the pulling of 14 cotter pins to remove the bumpers and reinstall. We averaged under 5 minutes to remove/install all the bumpers.

We were fairly happy with this first generation design and had no failures in any component. We will probably change the design slightly so that instead of holding the pins to the frame with cotter pins, the base of the pins will be bored and tapped and bolted to the frame. This will remove the play that can be seen in the photo. We will also design a new bumper bracket to hopefully be produced in CNC sheet metal, like our frame, improving tolerances. These brackets will also hopefully incorporate wrapping the corners of the plywood with aluminum angle.

[Karibou]

Originally Posted by skimoose

Team 228 turned aluminum pins which were inserted into holes in the frame and held to the frame with hairpin cotter pins from McMaster. The bumpers were held onto the pins with larger hairpin cotter pins as can be seen in this photo:

The bumper brackets were 0.125" aluminum angle bored to the OD of the pins on one flange and bored for deckmate screws into the bumper plywood. This system only required the pulling of 14 cotter pins to remove the bumpers and reinstall. We averaged under 5 minutes to remove/install all the bumpers.

This is very similar to what we did for 2009, and it worked fairly well for us. The bracket may have been the AM one, but I didn't make the bumpers, so I'm not sure. However, we had some issues with getting a few of the pins in - issues with lining up the brackets with the frame exactly, and a few of the pins had to be pushed in at EXACTLY the right angle...while using a hammer. If the pins had gone in a bit more smoothly, we would have had a much easier time. I have the feeling that we'll also be modifying our system this year (game pending), but the pins are much easier than what we've used in the past, so we might just stick with them.

[Trent B]

I have a feeling our team will use Pins this year if we can, getting bolts out of a cramped robot to release the bumpers is not a fun experience, the first year was awful, last year was mildly better.

[Rion Atkinson]

I know that last year sense our robot was made with 80/20 And we had vertical piece of it on each corner we found bolts that fit into the slots and Just mounted the bolts into the bumper back. This allowed us to just slide the bumpers on and off.

-Rion

[kevinhorn]

Here is a vid from a proof of concept that we did in 2008.
Our 2009 robot used a shoulder-bolt form a lawnmower axel with the hex ground down. This proved quick and simple.

[Otaku]

There's two good ways to do this that I can think of.

The first is if you have a reasonably solid frame, 1/4in thick or more, solid bar chassis (like 675 uses... a lot...). You could have matching holes in the frame and bumpers, tap the holes in the frame (or maybe weld on matching-thread nuts to the inside of the frame, assuming you're using weldable materials). Then what you do is get bolts that are just longer than the combined thickness of the frame member, nut if applicable, and bumper, and use that. Installation/removal is quick and easy, especially if you've got a socket driver on a power drill.

The second option should work for pretty much any frame. Pins. Do the same thing as above; holes in both the bumpers and frame members in matching place, or you could press or bolt in the male pin to the bumper. You can use either bolts or machined pins. Bolts will be cheaper but harder to drill a hole through. I really suggest using a drill press and a vice for this. Trying to drill something small while holding both things in your hand... bad idea.

Anywho, so what you do is once you've got your holes drilled and your pin ready, you mock it up on the chassis, and mark where to drill your hole. pull it apart, drill the hole, and put it back together with a cotter pin through the hole. For extra strength, put an appropriately sized washer in between the cotter pin and the frame member.

I can't guarantee either of those will conform to FIRST rules (depends on how you design them, honestly), but that's on you. Option #2 will be quicker to get on or off. Both are pretty quick though.