Team 254 Presents: Deadlift Technical Binder 2015
 

Team 254 Presents: Deadlift Technical Binder. The binder can be found here. If you have any questions or want more specifications, feel free to ask!

Re: Team 254 Deadlift Technical Binder 2015
 

Finally! Is code next?

Re: Team 254 Deadlift Technical Binder 2015
 

Code will be coming out soon!

Re: Team 254 Deadlift Technical Binder 2015
 

1.How are the carriages driven up and down? They appear to be attached to timing belts through some type of clip?

2. What type of bearings did you use for your elevator?

3. What types of belt did you use in your elevator?

4. How did you install your chain in the tubing?

5. Are you using the talon srx or victor SP?

Re: Team 254 Deadlift Technical Binder 2015
 

*effect

:-\

Re: Team 254 Deadlift Technical Binder 2015
 

This is a great resource! Thank you for releasing it.

Re: Team 254 Deadlift Technical Binder 2015
 

As always, the design binder is amazing.
I've got a few questions about the design process and the robot itself.

From what I can see, you guys have almost all of the robot in CAD before you start making parts for systems other than drive. At what point in the season do you finish drivebase CAD and the rest of the CAD? How many people do you have on your CAD team, and how long do they work to get it done?

Finally, does your team use any type of version control for SolidWorks, either EPDM or workgroup? If so, what type of server/computer does it run on?

It looks like you had no way to adjust chain tension this year. Would you recommend running a chain in tube drive system with no tensioners in a more aggressive game, or would you probably switch back to an adjustable and accessible design?

I've also seen your team run 3mm pitch pulleys off the output shaft of the RS-775 motors many times. Are these pulleys you make yourselves with a press fit for the motor shaft, or are they something else?

What material was used for the friction brakes?

Re: Team 254 Deadlift Technical Binder 2015
 

When you release the code will the simulator also be released? I'd love to see it.

Re: Team 254 Deadlift Technical Binder 2015
 

Thank You Team 254! Simple and effective process.

Re: Team 254 Deadlift Technical Binder 2015
 

Is it just me, or did one of 254's mentors post a reply, only for it to disappear? :ahh:

Re: Team 254 Deadlift Technical Binder 2015
 

If you guys are willing, I'd love a more in depth overview of the brake system used.

Re: Team 254 Deadlift Technical Binder 2015
 

I did. Alex will add to what I had. He had some additional insight specific to the assembly and maintenance.

Re: Team 254 Deadlift Technical Binder 2015
 

If I recall correctly from my visit to their pit in St. Louis, it's dead simple. Literally just metal on metal contact when the piston is engaged. The pressure and friction are enough to stop the elevator.

Re: Team 254 Deadlift Technical Binder 2015
 

When I looked at it, it looked like there was an odd rough brown material, not something like aluminum on aluminum.

Re: Team 254 Deadlift Technical Binder 2015
 

We used 410 Stainless Steel to make a "disc" that pushed against a High Friction Molded Brake & Clutch Lining Sheet. It works just like a disc brake, except the forces are applied axially about the point of rotation.

As you can see, the disc spins and slides on a 3/8" hex shaft. This allowed us to install the disc brake outside of the gearbox. It was the smallest solution we could come up with.

See below:

Re: Team 254 Deadlift Technical Binder 2015
 

1. Via HTD timing belts (endless) joined with a custom timing belt clamp that was integrated into the carriage bearing block assemblies.

2. Standard R3 and R4 equiv bearings.

3. 5mm Pitch HTD x 9MM wide

4. We held the chassis vertically and lowered the loop of chain down the end of the tube with the sprockets already on it and slid the shafts through the bearing blocks.

5. Victor SP

Drive CAD is done early by a group of a few students and a few mentors. It ideally is complete in the first 4-6 days. The rest of the CAD can linger for many more weeks as prototyping continues. Deadlift wasn’t even completed in CAD until the last minute with some parts were designed days before stop build.

We use PDM workgroup to manage SolidWorks files.

Undecided on the chain in tube. An adjustable and accessible design has worked well for us in the past. We didn't like that the chain rattled inside the tube, but otherwise we didn't have any issues with it. Assembly was not difficult and once it was installed we never had an issue.

3mm pulleys are available from WCP. http://www.wcproducts.net/gt2-timing-pulleys

Friction material was from McMaster: High Friction Molded Brake & Clutch Lining Sheet.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Thank you for sharing! I find this really helpful :)

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

I'm curious, what's the point of dropping the center 0.100 when you have omni wheels in the corners? Just a failsafe if you decide to go all traction later on?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

IIRC, their original release photos had all colson wheels...

http://team254.com/first/2015frc/

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

You guys had an absolutely fantastic robot; thank you very much for sharing through this resource!

The 254-style of very elegant, clean, box-oriented mechanical design makes your robots look deceptively simple... but let no one confuse elegant either for 'easy,' for not being full of design time/thought, or for not having complicated components.

I am intrigued as to what motivated you to use your particular elevator drive setup... I can see why a setup with 2 RS775's geared very fast with a pneumatic brake for holding is more 'mechanically ideal', but it seems like similar performance could be attained with a CIM (or two) at higher reliability and with less complexity. Was the elevator speed needed with the weight/CG of the RS775 solution? It doesn't seem like the power draw of a non-braking solution would've been too bad. Am I just standing on the other side of the 'elite powerhouse' line where the difference between an elevator at 5.85fps and one at 3fps is highly significant?

Also, am I correctly understanding the design that the elevator carriages were driven from only the right or left side (i.e., only from the right for the RC-carriage and only from the left side for the tote-carriage)? I see 4 long, vertical belts on each side which would make me think otherwise, but I don't see how the power for each carriage is transmitted to both right and left on the elevator gearbox.

Fabulous design and execution! Tough ending at CMP, but everyone obviously still has the utmost regard for Deadlift!

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Great read! Every year these are released, I learn a little more each time. I can't wait for the software release, because the whole simulator concept sounds really neat!

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

We originally designed the drive without the intention of using omni-wheels. However we decided to replace the outer colsons with omni-wheels after we found out that the robot turned much better with them.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Ah, that makes sense now. Thanks.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

FWIW, we seriously contemplated adding a third RS775 to the bottom carriage after SVR to improve loaded speed when carrying several totes.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

The goal was to have an elevator fast enough and powerful enough such that we were never waiting on the elevator while stacking. Two RS775s have a greater power to weight ratio even with the additional half pound from the pneumatic brake assembly than one CIM.

The gearbox transmits power to all four corners of each carriage. Its hard to tell from the render but each pair of motors drive two sets of pulleys which transmit power to the left and right side of the elevator.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

The whole robot package of robot software (Robot code + robot sim code + sim lib) should be out soon, but for now feel free to look through the WPI shim we wrote to get our robot code to run on x86.

https://github.com/tombot/FakeWPILib

On the other side of this, we had a simulated robot which could monitor PWM motor output values and set sensor values based on physics simulations. We used the debugger/monitoring/logging mechanisms built in to our main robot code to get everything working before it hit the real hardware.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Seriously impressive stuff. Thank you for sharing this.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Getting good simulation is the next big thing I think for FRC robots. Its hard to build a general sim for everyone, but even just having a simple backend that's extendable is a great start, especially since most FRC robots can be simulated with fairly basic physics. An elevator can be simulated without any calculus as long as you have a brake, or you lift counterbalance well. And even the calculus to simulate gravity is not very difficult. I really like how the Python port did this, and I wish someday that could be ported to the official languages as well. But without dynamic typing, it becomes a lot harder to do the way they did it.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Did you do any current monitoring of the intakes to prevent the totes from jamming?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Fair enough. :-)

Sounds like a worthy and intuitive goal... necessary for the ~8s 6-tote stack from RAMPage (which is just absolutely fabulous!). Having thought about the pneumatic brake aspect a little more, it really isn't that much complexity/risk... not any worse than (and very similar to) a pneumatic shifter. Had you guys used one before, or was it essentially all-new?

Makes sense... I was having a hard time imagining how it could work without something like what you mention. I think I can see a bit of the 'hidden' pulleys now that you note them.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Is there any footage of 254 using their can-burglars in autonomous? It doesn't have to be in a match, I am just curious to see how fast they are. They look similar in design to 3339's with piston placement and whatnot.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

The pneumatic ones are very slow compared to top can grabbers. The geared ones (never made it onto our robot in competition) are extremely fast. Likely within the margin of error of the fastest ones out there.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Can confirm, very fast.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Are there any videos of this?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Fast Geared Version - Green light on = robot enabled

https://www.youtube.com/watch?v=gPsM...ature=youtu.be

Slower pneumatic version

https://www.youtube.com/watch?v=gfht...ature=youtu.be

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Whoa. That geared version...I'm a little scared of it.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Why didn't that geared version make it onto the final robot?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Cheesecake! Yummmm

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

They put a pair on some wood poverty robot that went 2 for 2 with can grabs.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

LOL, poverty robot...

These probably won't be seeing use with the lack of bin wars at Chezy champs, right?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Yeah, a pretty dang good 'wood poverty' robot.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

The pneumatic one worked fine for quals - where we used it to grab another can off the step with the lasso method seen at SVR. The geared version was shorter and not really designed for the same purpose. We also always hoped we wouldn't need to put the fast grabber on, as we could cheesecake two robots and could continue with our 20 pt autonomous, which also had us starting the match with a can in our grabber.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Would there be a build blog?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

It is unlikely.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Anyway, thanks for posting these. It's way more than what most teams share and super interesting.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

How do you compensate for the big loss of strength in the HAZs of the 6061? How do you recommend other welded-chassis teams do it? Just blow up the thicknesses and section heights? I assume you don't do any detailed FEA or any post-weld heat treatment.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Don't quote me on this, but I think the mechanical fasteners and gussets that help to fixture the weldments also make up for some of the strength lost to the welding process.

I haven't played with a model of a welded FRC robot in a long time, but as along as the welds aren't in a really high stress area, I can't see them failing under most FRC conditions unless the wall thickness is really thin, or you're beating the heck out of whatever it is. (See 67's 2012 bridge arm for more insight)

Re: Team 254 Deadlift Technical Binder 2015
 

I'm not entirely following why the disc rotates. Is it rotating in an attempt to grab onto a specific part of the gear? Also, is there a wall of some sort behind that it presses the gear agaibst?
Thanks for the help.

Re: Team 254 Deadlift Technical Binder 2015
 

The disk is hex broached, and will always rotate with the rest of the gearbox.

The piston pushes it into the brake pad, which is mounted rigidly to the rest of the robot. There's not mechanical features like a dog gear or anything -- it's just pure friction.

Here's a picture I got of it in St. Louis in the context of the gearbox, which may help some. The silvery part is the disk, the off-black part with a fiber texture is the stationary pad.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Are the splicers for your timing belts just two pieces of metal bolted together? Thanks.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Sort of. It has a milled belt profile to distribute the load properly. See below.

These carriage bearing blocks were quite intricate, but essentially became the entire structure of the carriage. The carriages themselves were quite weak and not very stiff. The belt and carriage blocks in the corners made the thing extremely rigid.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Is there any footage/more documentation/images of Skystalker 0.2 available?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

How many individual structural parts are in this carriage bearing block, not including actual screws and bearings?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

5 (the two arms left and right, the base piece they mount to, the belt clamp backing piece, and the belt clamp itself). There are also 2 alignment pins to clock the left and right bearing arms with respect to the main body.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Would pat fairbank release a photo album for this year's build?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

I didn't take many photos this year during build, sorry.

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

There wasn't much to take pictures of...

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

Great insight into one of the best teams in FRC (if not the best). I'd like to know a little bit more about your target build schedule if you're willing to share. How much time is spent on prototyping? Building a driveable prototype robot? This is something very few teams do, does this give great insight into how the game will play? When do you start work on the practice bot? comp bot? When do the programmers get it?

Re: Team 254 Presents: Deadlift Technical Binder 2015
 

If you haven't read them already I highly suggest going through 254s 2013 or 2014 Build Blogs. A bit long but very well worth it and it covers your questions.