The age old question - bumper mounting
 

Hey all.

We've suffered from difficult-to-mount bumpers for the past two years and wanted some input.

How does your team do it? Are there great ways to do it?

ALSO, what's the best way of making bumpers - IE, make each side a separate piece? Make the whole thing somehow 1 unit? Make a U-shape that's 3 sides to slide on, and then finish off by mounting the last side? What has the best balance of aesthetic appeal and ease-of-mounting?

As for mounting, I keep seeing something like a shallow aluminum c shape onto which bumpers slide onto, which I can't for the life of me understand!

Thanks.

Re: The age old question - bumper mounting
 

What we've done the past few years is bolted some small pieces of c-channel with a hole onto the back of our bumpers, and then put the small pieces of c-channel on top of our frame, line up the c-channel holes with holes on our frame, and put a pin through them. As for amount of sides with separate bumpers, two years ago we used one for each for each side, and this year we made one set to fit on all sides. There really wasn't too much of a noticeable difference between the two, other than it took more time to make the singular bumper than the separate ones.

Re: The age old question - bumper mounting
 

Though I haven't seen how one works, bumpers with a quick release seem quite nice because changing bumpers can be done with no or less tools!

MAKE SURE THE BUMPERS DONT FALL OFF IN THE MIDDLE OF A MATCH!!!

Re: The age old question - bumper mounting
 

We take our bumpers off and bolt them on once per competition for inspection. After that we use reverseable bumpers that many do with Velcro, but this year we sewed in a bungee cord to allow us to flip quickly without having to secure anything.

Our mounting is simply a piece of 20ga aluminum sheet that is bent at 90 degrees and screwed to the bumper with 1/2" wood screws. We then drill holes in the aluminum and run bolts through every 8" or as rules require to attach to our frame. Bolts may not be quick, but we've never had loose bumpers and since we rarely remove them we could care less about speed.

Re: The age old question - bumper mounting
 

We usually have bolts sticking up from the frame of the robot and then holes in the bumper mounts so we basically just drop the bumpers down over the robot and secure it with wingnuts. Combined with the reversible fabric colors, it takes about 30 seconds to switch/take-off the bumpers.

It also takes no tools at all to remove or put on.

Re: The age old question - bumper mounting
 

We always mount our bumpers on 90º angle brackets directly to the top of the c-channel using quick release pins. When we use this system, we can change bumpers in around thirty seconds by simply pulling the pins out, kicking the robot to make the bumpers fall off, line up the other set, and slide the pins back in. The pins are strong enough to keep the bumpers on the robot even when it's upside down (we use the variety with a ball bearing at the bottom of the pin), but easy enough to remove that they're not too much of a hassle for us to hate changing them.

EDIT: These are the pins we use.

Re: The age old question - bumper mounting
 

For this year's game, our original plan was to have 1 wrap-around bumper fall into place and snap on, making a secure fit. However, the quick release system didn't end up working as the pins we ordered at the time were too short.

For simplicity's sake, we decided to use just add two pieces of L-angle aluminum to the back of the bumper, mounted such that when the bumper came down on the robot, the bumper would be resting on top of the drivetrain rails. We then used wing screws and some 8020 drop-in nuts to secure the bumper in place.

Re: The age old question - bumper mounting
 

We've used a 2-pin quick release system for the last 2 years as per the pictures in this post:

http://www.chiefdelphi.com/forums/sh...4&postcount=87

Re: The age old question - bumper mounting
 

For the last few seasons 1983 has recessed our bumper backing into the frame and then pop riveted through the top and bottom to secure it. We think that the end result is not only aesthetically clean, but it adds to the structure of the frame. The recess is created by extending the upper and lower sheer panels past the vertical walls of the frame. If you look closely you can see the thru holes for the rivets in the attached picture.

http://team1983.files.wordpress.com/.../wp_001144.jpg

Re: The age old question - bumper mounting
 

80/20 angle brackets (the small type) attached directly to the frame have always been the standard method on 449, with the bumpers mounting directly through them via. wing nuts. Easy to set up, and it works well.

Last year, 4464 mounted our bumpers through holes in the c-base using washers and wing nuts, but this was a pain and I hope we don't do it again.

Both teams used separate bumpers for each straight run on the frame perimeter, and that's worked well enough that I don't see any reason why we'd change it. Corner bumpers just seem harder to make.

I am proud to report that I have never, ever seen a bumper on one of our robots fall off during a match.

Re: The age old question - bumper mounting
 

I still like the added structure of having a solid full wrap bumper with no gaps. Here is our take on the quick change color set up. Just sew a loop in and fish 8 feet of elastic through, a few hog rings later and never look back.

Re: The age old question - bumper mounting
 

We usually have had a C-Channel chassis so we mount vertical 80/20 channel pieces periodically around the perimeter. These pieces are only several inches high and have a thumb screw with the part you would grasp facing the inside of the robot. The bumpers have 14-20 buttonhead bolts screwed into them that stick out just enough to drop them into the 80/20 sections. Usually works pretty well, sometimes we have to use a hammer to give the bumper a little motivation.

As for our actual bumpers, we usually make 2 sets of 2 bumpers. Usually right/left or front/back depending on our robot dimensions or if we have to have a gap in our bumpers that year.

Re: The age old question - bumper mounting
 

We drilled holes through the backing plywood and glued pins in to it. The pins line up with holes in the robot chassis and are fastened with small wire pins.
Our only problem was reaching the pins in the middle on our shooter side. It's super quick but only if you can reach your hand in the right spaces.

Re: The age old question - bumper mounting
 

This was an awesome way to mount our four corner bumpers to the c-frame base. We were able to change bumpers in about 45 seconds.


Mount pieces of oversize c-channel to the back of the bumper, lined up with the holes on the robot chassis

http://www.chiefdelphi.com/media/photos/39229?


Use long bolts with spacers (made from air hose) as mounting pins. You can use wing nuts to secure them, but we had no problems just inserting the pins.

http://www.chiefdelphi.com/media/photos/39230?

Re: The age old question - bumper mounting
 

We generally use a 1x1 square tube (with radiused edges) to rim the chassis and provide bumper support. The kit channel nests very nicely over the square tube. We fab/weld support clips from 2 short pieces of the kit channel and use a quick release pin at each mounting point. Making the bumpers in L-shaped sections will make them even more secure when mounted. See a model in this thread:


http://www.chiefdelphi.com/forums/sh...d.php?t=111344

Having said all this, post #11 clearly takes the cake, and we'll definitely look into this approach this coming year. :D

Re: The age old question - bumper mounting
 

Team 3574 designs their bumpers so there is no "Changing bumpers" during a competition. The bumpers are created so there is a "Flap" with Velcro so you just pull them down or up depending on the color you want.

The bumpers themselves are mounted to the frame with hitch pins for easy removal if we have to work on something in the heat of the competition.

Here is a link to what they look like. http://first3574.org/images/gallery/4.JPG

Re: The age old question - bumper mounting
 

Email us at waialuateam359@yahoo.com and I can show you a pic of our quick release one.
We even had one of NASA's Team 118's engineer complement us on ours, as it sat in their shop for a couple of days this past summer.:D

Re: The age old question - bumper mounting
 

Here is a concept drive base/ bumper mount system that I designed a few months ago. It uses two plates, one on top, one on the bottom, and the bumpers are attached by a piece of 2x1 box tubing which is bolted between the plates. This probably isn't practical without significant prototyping, but I will put it out there anyway.
https://drive.google.com/folderview?id=0BxrM5TU8rVcOYnVNaEZYczlCcjQ&usp=sha ring

Re: The age old question - bumper mounting
 

I like the idea, but isn't 2x1 for the attachment a bit overkill? I think it'd be easier just to use some corner brackets.

Re: The age old question - bumper mounting
 

In that design, I was using the bumper attachment brackets as a structrual element, and I was trying to make the bumpers work with my chain tensioning system. 2x1 is probably a bit overkill, but it's part of the bumpers, so it doesn't matter a tremendous amount.

Re: The age old question - bumper mounting
 

Has anyone tried a clevis/cotter pin attachment for bumpers?

Re: The age old question - bumper mounting
 

Team 3467 used angle brackets, with holes on both sides, bolted onto the robot frame with T-nuts pressed into our wood bumper backing. We attached the bumpers by running bolts through the holes in the angle brackets and bolted through the T-nuts into the wood. This idea was great besides the fact the T-nuts would come out of the wood at competition.

We also had one solid bumper on the robot. No individual pieces. This idea was great in theory but after our two regionals, the seams between the sides began to tear.

Re: The age old question - bumper mounting
 

Dave, this looks like a very slick way to attach bumpers, but my initial reaction is that it would be in violation of R21-F (must attach to the FRAME PERIMETER of the ROBOT ...) and/or R26 (BUMPERS must be supported by the structure/frame of the ROBOT (see Figure 4-10). To be considered supported, a minimum of ½ in. at each end of the BUMPER must be backed by the FRAME PERIMETER...)

Since your FRAME PERIMETER (definition copied below for reference) is the top/bottom horizontal plate, it seems your BUMPERS are backed by an interior part of the robot, not the FRAME PERIMETER. Alternately, if you intend to define your FRAME PERIMETER as the vertical face which backs the bumpers, then the robot is in violation of the STARTING CONFIGURATION requirement.

Can you (or any experienced inspectors) help me understand how this attachment method is legal?


FRAME PERIMETER: the polygon defined by the outer-most set of exterior vertices on the ROBOT (without the BUMPERS attached) that are within the BUMPER ZONE. To determine the FRAME PERIMETER, wrap a piece of string around the ROBOT at the level of the BUMPER ZONE - the string describes this polygon.

Re: The age old question - bumper mounting
 

We just attach them in some solid yet semi-removable way. We dont actually ever take them off in competition because we just use reversible fabric on the bumpers. SOOOO much easier to just pull some velcro and flip the fabric instead of taking the whole thing off. We actually just did it in que.

Re: The age old question - bumper mounting
 

Design your bumpers so that each segment is removable by one person in less than 10 s, yet won't shift or fall off during a match. This is easy using a locking pin system (if you pay close attention to hole tolerances and alignment), but a bit harder if using threaded fasteners (try wing screws and threaded inserts for woodworking).

For bonus points, consider using the bumpers as robot structure (plywood can be quite strong). In that circumstance, a little extra effort to remove the bumpers (like 60 s per segment) is perhaps justifiable.

Re: The age old question - bumper mounting
 

For mounting the bumpers, 1712 has essentially used the same method for a while. We have 2-3 pieces of aluminum angle per side of the robot, with a slightly oversized 1/4" hole in them. Through these, we secure the bumpers with 1/4"-20 threaded knobs that thread into threaded inserts in the plywood of the bumper. It's not quite as fast as some of the pinned-removal systems, but it's easy and secure.

For the past few years and this year, we've had 100% bumper coverage of the frame, with one segment for each of our four sides. Prior to 2013, the bumpers were red and we had one blue removable "skirt" that we fitted around all four bumpers for when we were on the blue alliance. The skirt was secured with hook & loop straps. In 2013, two adjacent bumpers were red and the other two adjacent bumpers were blue. We then had a reversable "skirt" that could be fitted over either two segments of bumper to complete the color we needed for that match.

C channel, ball-lock pins, and a "halo" of frame perimeter.

Makes for easy on/off, lightweight, and doesn't leave any weird hardware showing when we demo our bot for sponsors, without bumpers.

Re: The age old question - bumper mounting
 

Yes, the picture Dave attached doesn't really tell the whole story. I didn't understand how it was legal until I saw it with half the bumpers mounted. Look at the attached cross section and it'll make a lot more sense.

Re: The age old question - bumper mounting
 

Thanks for the clarification, Nuttyman54. It still seems to me like this doesn't meet the intent of "backed by the FRAME PERIMETER..." as my definition of "backed" would be surface to surface (or perhaps surface to edge). In this arrangement, there is still no part of the bumper wood directly touching the outside edge that defines the frame perimeter (or within 1/4"). Yes, there are bolts/rivets just interior to the frame perimeter holding a bracket in shear, but in my mind that's not the same thing. If the C of the frame was less than 5" tall, such that the wood directly contacted the outside edge which forms the frame perimeter, that would be more obvious to me that it meets R26. (Or even if the C was just a little bit shorter, and the brackets went to the outside rather than the inside, assuming the brackets are less than 1/4" thick).

If I were to speculate on the intent of R26, it would be that if the robot was hit hard in the bumper zone, the bumper would be prevented from moving relative to the robot (or at worst, would only move 1/4") by the wood surface compressing to the frame perimeter. In this example, the wood is prevented from moving inward by the shear strength of the bolts/rivets, not by the rigid frame perimeter. It is perhaps further prevented from moving by the length of the brackets which closely match the depth of the "C", but you could easily have shorter brackets or a deeper "C" and lose that feature. If I was inspecting this design, I would challenge that it meets the intent of the rules.

Thanks for sharing this example of a different form of implementation and rules interpretation. As a robot inspector, I'm interested in making sure I understand how the rules are and should be interpreted prior to the events. I would be interested in any LRIs' thoughts on this.

Katie

Re: The age old question - bumper mounting
 

I believe the wood is actually backed the frame perimeter flanges, but that's not captured in my very un-precise powerpoint sketch. Both the frame and angle are made from 1/16" 6061 aluminum.

1983 has run this setup since at least 2011 at regionals and champs and never had an issue with inspections. I believe it also most definitely meets the intent of the rule, which is to provide a robust mounting system for the bumpers to attach to the frame perimeter of the robot and protect our robot, other robots and people from damage. It's one of the most secure bumper attachments I have ever seen.

EDIT: After looking at the robot last night, the top piece of AL angle goes on top of the chassis C, not nested inside, so the angle itself is backed by the frame perimeter. That should clear up any confusion about how it complies the rules.