pic: Spectrum Fall 2013 Drive V2

[DampRobot]

Originally Posted by AllenGregoryIV

Interesting, we were planning to do a one piece bumper that drops over the top of the robot. In that configuration I don't see an easy way to limit to the vertical forces that will act on the latch during impact. We had issues with the double C design because they are weaker where the two C bumpers meet. Our frame bent in when we hit the pyramid once.

Put a small but long L bracket on each side of the bumper that keeps the bumper from getting pushed down. The latch should be more than enough to keep the bumper from going up. (I'd be surprised to see much up forces on a low-to-the-ground bumper in a match.) I believe 971 did their bumpers this way in 2012.

[AllenGregoryIV]

971 also used them in 2013 but they have 8 around the perimeter of their robot.

After doing more research I am looking into using twist latches that are used on road/flight cases. They're normally rated for a lot of force and you can get them for under $3 each.

I also think it might be possible to build the keeper directly into the frame, instead of having to rivet/bolt it on.

[kevincrispie]

Allen,

I'm not sure what your thoughts are at this point, but I can help to shed some light into how 971 did bumpers this past year. Below is a picture of our 2013 bumpers.



We actually did not have 8 latches all the way around, as you can see in the picture. Some of the latches intersected with some of the robot components, so we wouldn't have been able to access them. Also, the bumpers and latches don't always go together smoothly, and pieces can warp over time, so by the time we actually competed, only around 3-4 of the latches were actually hooked on. The rest were tied away so they wouldn't jostle around during the match.

We bought the latches from McMaster, but we ended up having the hooks made by a sheetmetal sponsor out of stainless steel, 0.090" thick iirc. We then riveted these onto the frame. We had issues with the hooks bending in 2012. The stainless steel hooks this year did not have the same problem.

This system held up reasonably well throughout the course of the season. Obviously we would have liked to attach the bumpers at more points, but it doesn't always end up that way. We ran into similar issues in 2012.

I hope this helps. If you have any questions don't hesitate to ask me or another 971 member.

Kevin

[Travis Covington]

Originally Posted by AllenGregoryIV

I'm also looking at bumper mounting systems. The latch systems used by 254, 971, and other seem really expensive at around $10 each. Has anyone had experience with McMaster quarter turn fasteners?

There are a bunch of options. Cheaper ones of the same thing are here: http://www.mcmaster.com/#1889a37/=omwtea

[Blackphantom91]

This cad model is great! I personally really like the Ethernet jack port in the side for easy quick disconnect. What type of design models did you base this off of it? seems very robust and nice. Keep up the good work!

[Pault]

Originally Posted by AllenGregoryIV

Interesting, we were planning to do a one piece bumper that drops over the top of the robot.

Have you ever tried that method before. Because my team tried that and 2012 and it was extremely difficult to slide it over the superstructure on the robot (of course you don't have any superstructure, but your robot next year probably will). Instead, we ended up having it come up from beneath the robot. (Yes, you have to lift the robot to do this. It takes us a long time to change bumpers). However, it is very difficult to do this with 4in wheels because of the minimum bumper height. The benefit to it is that a single piece bumper adds a ton of rigidity to the chassis (this year we were literally able to get away with a plywood board as a chassis and use the bumpers to reinforce it).

[AllenGregoryIV]

Thanks everyone for the tips about the bumpers. We're going to experiment with the twist latches and I'll let everyone know how it goes.

Originally Posted by Blackphantom91

This cad model is great! I personally really like the Ethernet jack port in the side for easy quick disconnect. What type of design models did you base this off of it? seems very robust and nice. Keep up the good work!

What do you mean by design models? Are you referring to the ethernet port specifically or robots that helped inspire this design? Also, thanks for the compliment.

Originally Posted by Pault

Have you ever tried that method before. Because my team tried that and 2012 and it was extremely difficult to slide it over the superstructure on the robot (of course you don't have any superstructure, but your robot next year probably will).

We haven't done it ourselves yet, but we have seen a ton of other robots that have. If everything goes to plan this robot will have a super structure. It's going to be the base for the prototype robot for our mock game we developed last spring, PIPEFALL.

[BBray_T1296]

Our team uses flip-switch bumpers. While we usually (and unfortunately) seem to always make our bumpers a right pain in the neck to attach and remove, We only have to do so once during inspection. Basically, our bumpers are two sided, and we can literally change colors in <5 seconds with a simple flip. If I knew how o post a picture of this, I would

[AllenGregoryIV]

Originally Posted by BBray_T1296

Our team uses flip-switch bumpers. While we usually (and unfortunately) seem to always make our bumpers a right pain in the neck to attach and remove, We only have to do so once during inspection. Basically, our bumpers are two sided, and we can literally change colors in <5 seconds with a simple flip. If I knew how o post a picture of this, I would

I have experience with reversible bumpers and I wasn't a big fan. I was with the Discobots in 2011 when we did flip bumpers. They were great for week 1 but by the middle of our second event they started fraying, the velcro started breaking away from its stitching, and they just looked awful. Maybe the parent we had do the stitching didn't do it right or something but I've been hesitant ever sense. I'm also not really a fan of the seam running down the middle of the bumpers. If our design ever required us to leave our bumpers on, it's something I would consider. I also liked 33's skirt system this year but that would require a pretty good seamstress as well.

For completeness to this thread anyone looking to do reversible bumpers. This is the whitepaper by 2809 that is most often linked as instructions.

[Blackphantom91]

Originally Posted by AllenGregoryIV

Thanks everyone for the tips about the bumpers. We're going to experiment with the twist latches and I'll let everyone know how it goes.


What do you mean by design models? Are you referring to the ethernet port specifically or robots that helped inspire this design? Also, thanks for the compliment.PIPEFALL.

well main part is the ethernet port as an IT brain I think it is ingenious. Also yes what had inspired to you make a drive train like this. I saw v1 also and was curious.

[AllenGregoryIV]

Originally Posted by Blackphantom91

well main part is the ethernet port as an IT brain I think it is ingenious. Also yes what had inspired to you make a drive train like this. I saw v1 also and was curious.

Directly it was all from Madison and the people that posted in these threads.
FRC488 -- Fall Project
FRC488 - Fall Project, Rev. A

I've liked the idea of a gear drive, ever since looking at 25's robots from the behind the design books from 06 and 07. The bellypan setup is inspired by 968, 1538, and the other west coast teams that have been doing it for years. 971 and 148/JVN/VEX both contributed to the sheet metal inspiration.

We also talked as a team about the things we liked and didn't like in our chassis from last year.

[Blackphantom91]

Nice! I really like it keep up the good work.

[AllenGregoryIV]

We worked on the twist latch system today at our meeting. The basic prototype worked way better than I ever expected. You can see the pictures below.

Twist Latch Bumper Prototype

We made a very simple mock board to act as the bumper and didn't modify the VEXpro chassis in any way (The 2013 KOP frame would need slots cut into it). I'm pretty sure this is a setup that most teams could use.

We will probably modify our 2013 robot to use this system for our last off season in November. That we can test it against other robots and make sure it can stand up to abuse.

These are the latches I purchased for $2.45 each.

[AustinSchuh]

Not a bad start.

I keep seeing people here make the same mistake, and it bothers me enough that I'm going to say something.

Think of sheet metal like paper. Go ahead and grab a sheet and play with it. Bends add lots of strength. Wherever you break the bend, you make the part significantly weaker.

The first thing that I see when I see the side rail parts is that you broke the bend both around the transmission and on the outer edge all over the place. This significantly weakens the frame. I'm going to make a wild guess and say over 2x weaker when in compression. (Props for anyone who does FEA to get a better estimate.) Do yourself a favor and figure out how to not brake the bend. Space the wheels in away from the edge, or whatever it takes to make that happen. That will take your frame to the next level and make it bullet proof and incredibly stiff, which is exactly what you want.

If you don't believe me, print your robot out on paper at partial scale, cut it out, and assemble it. Try twisting and bending it, and see what happens.

[T^2]

Originally Posted by AustinSchuh

Think of sheet metal like paper.

Weird, people keep telling me to think of paper as sheet metal.