Best methods of bumper mounting?
 

See title for question.

I've struggled with bumper mounts due to wanting them to be very secure and easily removable. What have teams done in the past to accomadate these needs? Not looking for reversibl bumpers as a solution to the second part.

Re: Best methods of bumper mounting?
 

While a lot of teams use either quick release pins or over-center latches, we have always used rivnuts in the frame and 10/32 bolts to attach the bumper brackets to the frame.

Re: Best methods of bumper mounting?
 

Following what we saw on HOT's 2012 robot, we built our 2016 frame perimeter using 2x1 1/16th wall aluminum tube. Our one-piece bumper fits tightly (< 1/16th clearance) to the frame and is attached using aluminum angle. Vertical 1/4-20 bolts run through the angle and frame in four places, secured using nylon lock nuts. Takes a couple of minutes to remove the bolts and lift the bumper off.

Re: Best methods of bumper mounting?
 

1983 secured their one piece bumpers with toggle clamps and seemed to work well.

Re: Best methods of bumper mounting?
 

3928 has used Stainless Steel Snap latches (found on McMaster here) since 2013. At around $6.00 a piece, they aren't cheap, but make for very quick bumper attachment and removal. They are attached to the bumper by an L bracket. The latch slides over a spacer on a 10-32 bolt that is on the frame. This makes them fairly adjustable. Taking bumpers off or on takes less than 10 seconds for two people.

Re: Best methods of bumper mounting?
 

We had a 1x1x1/16 aluminum tube that went around our frame perimeter. The bumpers had 8 aluminum U extrusion pieces 2 inches long that were mounted inside pockets on our bumpers. This allowed us to get a tight fit between the U channel and the 1x1 tube. 1/4 inch holes in the 1x1 and the U brackets allowed for a quick release pin on each bracket http://www.mcmaster.com/#98470a135/=12cpcnp. To put the bumpers on or take them off was about 30 seconds.

My explanation might not be the greatest but once we get our crate back from fedex I can post some pictures.

Re: Best methods of bumper mounting?
 

How about a quick and dirty MS Paint diagram in the mean time?

Re: Best methods of bumper mounting?
 

For 2016, 2667 had a really nice connection-- basically two halves with bolts that were all facing the same direction (in from the left or right side), so that putting them on or taking them off was just a matter of four wing nuts per side. They held up extremely well for competition, and were so simple that even with extremely low resources (money, time, and experience). I'll see if I can find some pictures.

Re: Best methods of bumper mounting?
 

Here is a cross section of one of the mounting points. The bumper is on the left and the U Channel is recessed into a pocket on the wood of the bumper. This allows a tight fit between the outside of the frame and wood part of the bumper, the top of the 1x1 and the U, and the outside part of the 1x1 and the outside part of the U. The pin goes all the way through both sides of the U and the 1x1 with a .25" hole.

To take the bumpers off, slide the pins out and pull up vertically on the bumpers. To put them on push the bumpers down until the brackets sit flush on the 1x1 and push the pins in.

Re: Best methods of bumper mounting?
 

1678 has used the snap latches shown in bstew's post but we last used them in 2014 and had to replace them because they couldn't hold up to the huge impacts that year.

I very strongly suggest the rivnut + bolt + drill driver or the rivstud/PEM stud + nut + drill with nut driver methods. It is super fast and easy to swap bumpers that way. Over-center cam type latches are also great but can be harder to implement properly.

Re: Best methods of bumper mounting?
 

Team 330 used a similar mounting system this year. The only difference is that the "bottom" of the U channel is screwed into the wood, and the quick release pins are vertical.
The entire mounting system is rotated counter-clockwise in comparison to bcampbell's diagram.

It worked extremely well, and the wood screws only needed to tightened once or twice throughout the season. (primarily due to how our robot has to be lifted off of the tower after a scale)

Re: Best methods of bumper mounting?
 

Rivet nuts and screws are a quick easy way to do this.

GUS uses a tapped standoff on the chassis side with a hole through it for a cotter pin. An L bracket with a clearance hole for the standoff is mounted to the bumper. Just skip the bumpers on and then slide the cotter pin in. Very quick, very easy, no tools required.

Re: Best methods of bumper mounting?
 

As did 1197.

A word of caution on wood screws: you can never have too many in your bumpers, and keep 'em tight. Experience talking (thankfully not mine...this time).



If you gotta make a mistake, go with "more secure".

Re: Best methods of bumper mounting?
 

Add me in the Rivnut/PEM nut catagory.

Jay you know our bumpers weren't the quickest to get on/off this year but that was pretty much entirely the design of certain aspects that kept the access down to almost nothing. In the future it would have worked a lot better if we kept the space above open for tools like a ratchet or drill and could have considered wing nuts if we had more space. Keeping all the bumpers mounted on the top side of the robot would have helped too and with a one piece bumper it could have helped reduce the number of mounting points.

For reference we used Rivnuts with a 1/4-20 bolt coming up through the bottom and used non-locking nuts to hold the bumpers on. Often just hand tight due to access but a few received a ratchet.

After doing something similar in 2014 I think it is a good balance of low effort and strong connection between the frame bumpers and frame.

Re: Best methods of bumper mounting?
 

These automotive panel nuts work the same as rivet nuts, bit they're cheaper, and easier to install as long as you have an edge close to your frame rail. They fit the Andymark kit chassis perfectly! We used them to hold our bumpers (and our manipulator) to the frame this year: http://m.lowes.com/pl/Standard-sae-u...eners-Hardware

Re: Best methods of bumper mounting?
 

CIS 4607 had a two piece bumper that were reversible. These mounted to the 1X2 welded aluminum frame with 1' angle mounted to the bumpers and four 1/4 - 20 bolts.
This year we were a very physical robot that focused on defense. We both delivered and took a beating every single match and the bumpers held up very nice.

Re: Best methods of bumper mounting?
 

From a robot inspector who has seen thousands of attachments, a mount that is attached to the bumpers that fits into/over/on the frame and has hardware/pins/latches that are installed from the top of the robot are the best. Screws/bolts that need to be driven in from the interior of the robot frame are OK but you will eventually drop that hardware in the robot and it will take special tools to install or remove the bumper system. This year had some defense but not as much as I expected. Bumpers are meant to take the full punishment another robot can inflict. Make them secure and easy to remove.

Re: Best methods of bumper mounting?
 

There have been many different excellent attachment methods mentioned in this thread. The most important thing to do is to pick one and design it in along with the rest of the robot rather than leave it as an afterthought. Otherwise that xxx-latch that worked so well for another team won't work so well when there is no room to install it, it can only be installed in a hard to reach place or there is nothing strong enough to attach it to.


Some (many?) of you may have had wood screws strip out. If so, remove the screw and drip some thin (not gel) cyanoacrylate (super) glue into the hole and wait for it to set. It soaks into the wood and makes the wood swell a little so the screws have something to grab. The CA will make soft wood as hard as maple or oak so the screws won't strip out again.

Re: Best methods of bumper mounting?
 

Forgot about that trick--it's great for a quick hardening of wood when you're building a model airplane. (Actually, add a little when the screw is in there--that'll really make it hard to get the screw out.) Just don't stick your fingers together, it hurts.

Re: Best methods of bumper mounting?
 

Our team had a reversible bumper that wrapped around the robot, and it was secured with aluminum bumper mounts and rivnuts, which made it very easy to remove.

Re: Best methods of bumper mounting?
 

We used clips very similar to the belt clips found on the back of tape measures. At first, we had some issues (Finger Lakes Regional Q15 our bumpers fell off), but then we secured the bumpers even more and haven't had an issue since. Takes a few minutes and a screwdriver (to pry off clips) to change the bumpers.

Re: Best methods of bumper mounting?
 

I'm a little concerned about rule R21-G with some of the things mentioned in this thread. Perhaps I'm misinterpreting the rule. The picture seems to paint a pretty clear limitation of a 1" limit on hard parts. The 1" limit in the picture is placed over the inside and outside surfaces of the bumper plywood. Many great attachment methods need more than the remaining 1/4" inside the plywood after using 3/4" plywood, thereby seemingly exceeding this 1" hard parts limit.

What am I missing here?

Is there not actually any limit to how far the "hard parts" can stick inside your robot? Can someone point me to some rule or clarification that indicates this?

Re: Best methods of bumper mounting?
 

emphasis mine.
Seems pretty clear to me. The 1" is counted from the frame perimeter.

I guess bumper attachment system can be ridiculously huge then, but at some point the bumpers will hit the 15lb limit.

Re: Best methods of bumper mounting?
 

The limit applies outwards away from the Frame Perimeter.

Question 744 is a relevant clarification.
https://frc-qa.firstinspires.org/Que...taching-a-1-x1

Re: Best methods of bumper mounting?
 

Clevis and reusable cotter pins. Cheap, easy, quick.

Re: Best methods of bumper mounting?
 

The obvious response to this is to use the right bumper as the attachment mechanism for the left bumper.

Re: Best methods of bumper mounting?
 

We used Rivnuts this year. In 55 matches and approximately 60 bumper swaps (including practice/etc), we stripped 3 of the Rivnuts. The last time one stripped, removal of the rivnut caused a bigger hole in the frame which then wouldn't accept a new rivnut. So we had to drill through and put in a through-bolt.

Next year, we may go to what 2363 had - see attached.

Re: Best methods of bumper mounting?
 

Steel or aluminum rivnuts?

Re: Best methods of bumper mounting?
 

Not sure. Steel bolts though.

Re: Best methods of bumper mounting?
 

We had 1" steel angle (hey, heavy bumpers are allowed) around most of our bumper perimeter. We had holes in the front and slots in the back to allow for a 1/4"-20 bolt to pass through. The bolts were put through the middle our bumper mount rail (1x1 aluminum) and a nut was installed on the inside of the aluminum to lock the bolt in place. So there are four 1/4-20 bolts sticking up in the corners. The bumpers were a single piece, so it slipped on over the robot, then we tightened them down with wing nuts. It was a pretty good system, and I think we'll probably end up doing it again. The only issues we had were inconsistency in the fabrication of the bumpers, so one of them fit a bit tighter than the other (but I think that can happen with a lot of bumper designs).

Re: Best methods of bumper mounting?
 

Previously the pins were vertically mounted, but I was much more pleased with the horizontal mount this year. Much sturdier.

Re: Best methods of bumper mounting?
 

This isn't correct - the 1" limit is from the frame perimeter outward (away from the robot), there's no limit on how far inside the frame perimeter you can go.

Re: Best methods of bumper mounting?
 

THIS is the most important advice. Assuming your latches/pins are strong enough, a well-integrated design will have a much bigger impact on reliability and ease of use than which particular pin you buy.

If your frame tweaks and you end up needing a hammer to get your bumpers on and off, all of a sudden you won't care that you can remove your latches in 1 second instead of 2 seconds. Be sure your frame is strong and won't permanently parallelogram or deform when you get hit. A bellypan, be it plywood, polycarbonate, or laser-cut aluminum helps a lot with this. It doesn't have to be sophisticated.

Mount bumpers such that impacts get distributed along the length of horizontal member, rather than being concentrated at attachment points. If you're running WCD, you may need to design an additional rail above your wheels to accomplish this.

Re: Best methods of bumper mounting?
 

Our team tried out these snap slide latches for the 2016 game and had a good amount of success with them.
http://www.mcmaster.com/#standard-draw-latches/=12g6itm
You bolt the pin to the top of your drive base frame and mount a piece of angle aluminum to the inside surface of your bumpers to mount the latch.
No tools necessary to take on or off the bumpers, no nuts, bolts, pins etc. to drop. Mounts and unmounts bumpers in a matter of seconds.

Re: Best methods of bumper mounting?
 

Which item specifically? You linked to the general McMaster page for draw latches.

Re: Best methods of bumper mounting?
 

Even if you use the same attachment system that worked well for another team but left the bumper design as an afterthought, it is likely that attachment system will not work as well for you.

The ones we used this year were part of the CAD and untrained students could get a set on or off within two minutes on the first try.

The rest of Evoluti1's advice is also really good, especially when there is a lot of defense to be played.

Re: Best methods of bumper mounting?
 

I think 2471's bumpers this year should be contenders for "best bumpers" and "best bumper mounting method." Here are some pictures of the mounting system and the bumpers themselves after several intense competitions:
https://scontent.fsnc1-1.fna.fbcdn.n...4f&oe=579B762B
https://scontent.fsnc1-1.fna.fbcdn.n...0a&oe=57E0D1C9
https://scontent.fsnc1-1.fna.fbcdn.n...4e&oe=579F2BAC

The bumpers slid on from the top. Quarter inch bolts fit into slots in the drive plates and plastic latches clicked around the front and back frame rails. A couple of people could remove or attach a set of bumpers in less than ten seconds.

Also, a set of these bumpers was stronger than most robots' frames!

Re: Best methods of bumper mounting?
 

Whoops! This link should be more specific:
http://www.mcmaster.com/#1872a72/=12gougp

Re: Best methods of bumper mounting?
 

We used cleco clamps. Do not use clecos for a game as violent as Stronghold. Actually, we probably won't use them even if there's not a lot of contact in any future game. Our bumpers fell off.

Re: Best methods of bumper mounting?
 

About that.... 2502's bumpers in 2014 were very interesting. Our electronics, drive modules, and just about everything else were super compact in the robot. The original plan was just to put bolts in the bumper, put the other side of those bolts through the frame, and then put nuts on the back to hold the bumpers on. Except that we couldn't reach the bolts to put nuts on the back. So instead, we used the bolts merely as a locators and strapped the bumpers to each other. So we ran webbing through our robot and tensioned it so the bumpers couldn't pull away from each other. Needless to say, the inspectors didn't like us very much.

TO CLARIFY: I DO NOT RECOMMEND THIS SYSTEM OF ATTACHMENT! It took upwards of 10 minutes to put the bumpers on and the only reason it didn't screw us over, especially in elimination matches, was because we had reversible bumpers. It was just a little bit hilarious so I thought I'd share.

This year, we had pieces of angle with holes drilled in them attached to the bumpers. Our frame was 1x2 tubing. We put pins through the holes in the angle and through the frame. It worked well, but they could have been a little more secure. Definitely paying attention to this thread to find ideas for next year!

Re: Best methods of bumper mounting?
 

How did these even pass inspection? You seem to indicate they took more than twice the guideline time to remove. According to the 2014 game manual:

Re: Best methods of bumper mounting?
 

It's a loose rule. We could also get them off very quickly, it just took a long time to put them on. The rule is phrased as "removable by two people in fewer than five minutes." We could remove them in about 45 seconds. It was a nitpicky way to get around the rules to be sure, but we really didn't even get questioned on it. They were secure, that's the important thing to most inspectors.