Cat5 Bumper Mounts

[HumblePie]

Originally Posted by Al Skierkiewicz

Doug,
From what I can tell from the picture, this is very good way to attach bumpers. Simple, easy for one person to remove and if the design is as it appears, legal. If you are sure that the bumpers cannot be dislodged or change attitude with aggressive play, then I can say "nice design".

Al,

Thanks for the input. The bumper backing board is only the clip thickness (1/8") from the support structure of the robot, and nowhere is there a span over 7" that is unsupported, so based on the most recent rules, I believe it to be legal. We used a similar system last year at 2 regionals with no security issues (and, sad to say we were flipped over more than once). I do think that constructing the bumper sections in an "L" configuration helps with security, since the bumper mounting points are no longer in a straight line.

[cbale2000]

Not gonna lie, when I read the name of this thread, I thought someone had used Cat5 (ethernet) connectors as bumper mounts...

[apalrd]

Originally Posted by cbale2000

Not gonna lie, when I read the name of this thread, I thought someone had used Cat5 (ethernet) connectors as bumper mounts...

Cat5 is a category rating for twisted pair phone/network cable. Cat5/5e is required for 100mbit Ethernet, Cat6 for 1000mbit, etc - I guess it's not required, but it is not guaranteed to work to specifications.

I was wondering how they used wire in their bumper mounts.

[ttldomination]

Do these pins hold the bumpers "tight"? With wingnuts you can tighten the bumpers to the frame. I'd suspect there would be some wiggle/play with the bumpers due to the wiggle/play in the pin inserts?

I don't have experience with this, and as much as I like to see rookies "descend" on the robot, I hate to see members struggle to mount bumpers as we are walking to queue.

- Sunny G.

[HumblePie]

Originally Posted by ttldomination

Do these pins hold the bumpers "tight"? With wingnuts you can tighten the bumpers to the frame. I'd suspect there would be some wiggle/play with the bumpers due to the wiggle/play in the pin inserts?

I don't have experience with this, and as much as I like to see rookies "descend" on the robot, I hate to see members struggle to mount bumpers as we are walking to queue.

- Sunny G.

The nesting of the kit channel clip over the 1' square tube takes care of the vertical movement (haven't measured the exact clearance, but it's pretty close) and the ball lock pin takes care of the horizontal plane. If you drill a 1/4" hole through the square tube, the clearance is just that of the 1/4 inch ball lock pin and the 0.257" hole in the kit channel. Connecting 2 bumper backings together at a 90 degree angle (with wood screws and/or glue) makes any wiggle almost negligible. The issue we saw with wingnuts our rookie year is that not every student can get them really tight, and some loosening was possible during the match.

[ttldomination]

Originally Posted by HumblePie

The nesting of the kit channel clip over the 1' square tube takes care of the vertical movement (haven't measured the exact clearance, but it's pretty close) and the ball lock pin takes care of the horizontal plane. If you drill a 1/4" hole through the square tube, the clearance is just that of the 1/4 inch ball lock pin and the 0.257" hole in the kit channel. Connecting 2 bumper backings together at a 90 degree angle (with wood screws and/or glue) makes any wiggle almost negligible. The issue we saw with wingnuts our rookie year is that not every student can get them really tight, and some loosening was possible during the match.

Oh yes, I was advocating the pin/lock mechanism and not the wingnuts. We've had many a times when we were in a rush and we realize that we have the wrong bumpers on.

- Sunny G.

[Phyrxes]

We have used a similar method before, once you find the correct length ball lock pin (from Mcmaster for us) everything goes together nicely. While we have never tethered the pins we trained the students to leave the pins in the robot frame when the bumpers were not on it.

[Jon Stratis]

We've been talking about switching to a pin like that... I really hope we finally do it this year.

Can you expand on the light green bumper mounts? Is it a piece of C channel with an additional L bracket on top? Was this primarily for additional support vertically, as the bumpers are really only supported along the bottom edge by the frame?

We always try to keep our frame in the center of the bumpers, which has allowed us to use some C-channel sized to fit snugly over the kit frame, without any additional supports. Of course, we've always used nuts and bolts, so it's been a pain to take the bumpers on and off. Fortunately, we've used reversible bumpers the past two years, so that hasn't been a problem!

Bonus points: attach the pins to the bumpers through a small cord (many of those quick release pins have holes pre-drilled specifically for this!) so you don't lose a pin!

[HumblePie]

Originally Posted by Jon Stratis

We've been talking about switching to a pin like that... I really hope we finally do it this year.

Can you expand on the light green bumper mounts? Is it a piece of C channel with an additional L bracket on top? Was this primarily for additional support vertically, as the bumpers are really only supported along the bottom edge by the frame?

We always try to keep our frame in the center of the bumpers, which has allowed us to use some C-channel sized to fit snugly over the kit frame, without any additional supports. Of course, we've always used nuts and bolts, so it's been a pain to take the bumpers on and off. Fortunately, we've used reversible bumpers the past two years, so that hasn't been a problem!

Bonus points: attach the pins to the bumpers through a small cord (many of those quick release pins have holes pre-drilled specifically for this!) so you don't lose a pin!

I'll attach a closeup for clarity.

The 2 clip pieces are made from the kit channel (the lower one is just cut to length) and the 2 are welded together. This allows for the bumper backing to be fixtured at the desired height and attached to the bumper clip (in place) via wood screws. Depending on bumper height, the clips could also be mounted "upside down" as shown in second illustration. Connecting 2 perpendicular sections of bumper handles the bending moment so that the clips do not have to be centered on the bumper backing (helps save weight by not having structure dedicated to bumper support). And, yes we are considering tethers (non-conductive for sure!).

[Jon Stratis]

Very nice, thanks for the additional clarity! Depending on robot design, you may find your frame naturally in the middle (ish) of the bumpers instead of along one edge. This year, our frame was in the bottom third of our bumpers, but we had a little weight to spare, and put some vertical frame members in the corner as well. This gave us some additional support AND allowed us to build in handles to carry it with

Again, very nice design, thanks for sharing!

[HumblePie]

Originally Posted by Jon Stratis

Very nice, thanks for the additional clarity! Depending on robot design, you may find your frame naturally in the middle (ish) of the bumpers instead of along one edge. This year, our frame was in the bottom third of our bumpers, but we had a little weight to spare, and put some vertical frame members in the corner as well. This gave us some additional support AND allowed us to build in handles to carry it with

Again, very nice design, thanks for sharing!

I'd be curious to see your 'handle" arrangement. Care to share?

[Jon Stratis]

Originally Posted by HumblePie

I'd be curious to see your 'handle" arrangement. Care to share?

I can't find any good pictures, unfortunately. In the back, we simply ran crossbars (1 inch square stock) over to the main frame of our elevator, several inches above the bumpers, and duct taped half a pool noodle on the bottom for cushion. In the front, we had a similar crossbar setup, but bolted a heavy duty handle to the top. This let use pick up the robot pretty easily form the side.