95 Hard at work

[JamesCH95]

Originally Posted by Answer42

First of all, gorgeous and highly effective looking robot you have there. I have no doubt this will be a great season for you. And pneumatic brakes will definitely be an advantage to shooting this year. But, on the same subject even if your robot is not entirely off the ground, the pads will still be making solid contact with the ground. Meaning that when someone hits you with your brakes down, the robot will attempt to go in that direction and your main resisting force will be the rigidity of the (what looks like) 1/4 inch steel shaft. Even a quarter inch of movement of the whole robot would be devastating to the straightness of that shaft, particularly if the brake pads digs into the carpet and starts to twist from the horizontal. I would recommend some form of linear bearings to prevent this from happening. However to be clear, I'm no expert and this is just my 2 cents based on what I've seen from using brakes on robots.

We are a little nervous about this too. We plan on thoroughly testing the brakes to ensure that they will be durable enough to survive competition.

A quick analysis suggests that we have a moderate margin of safety if all 4 brakes somewhat evenly distribute the braking loads, but we don't know if the system will behave that nicely...

The (more complicated) contingency plan is to hinge brake mechanisms from the chassis side plate or the belly pan.

[JamesCH95]

Bumpers routed out in the wee hours this morning.

Details:
3/4in hardwood plywood
1/4in 2-flute up-cut carbide router bit
24k rpm spindle
180ipm feed
0.19in DOC

The simpler panels on the left took about 3min of cutting time, the more complicated parts on the right took about 14min of cutting time. Plunge speed is the main limiting factor it seems, and that will be my next set of experiments.

[JamesCH95]

Answer42 - We decided to get a little proactive and will be looking at installing linear bearings and/or some feature to support the brake cylinder shafts.

More to follow on that.

[JamesCH95]

Decent progress over the last two nights.

A nice little light bracket, plasma cut and then bent on a finger brake.



Pneumatic plumbing started.



Using these neat clamping hinges for our access panels, which are made out of PET-G instead of polycarbonate. Much cheaper and almost as strong. PET-G panels were routed out.



Got some LED light strips this year. Very inexpensive, very easy to use, and prime shipping from Amazon. Cut to length, solder on leads, good to go.



A good bit of progress filling out the guts of the robot too.

[Andy A.]

It always seems like the last 10% of the robot takes half the build. Not a lot of photogenic progress in the last few meetings, but we did come to what I think is a good part to keep our brake pistons from, uh, breaking.



It's a small aluminum cylinder that serves as both a bearing for the shaft and a replacement for the nose nut. One end is drilled for a tight fit on the piston shaft and the other threaded for 1/2-20 to match the piston nose. When extended the unsupported shaft length is much shorter now giving it, we think, a greater (adequate?) safety margin to resist bending.



Most of the wiring and pneumatic plumbing is completed. Everything lights up and no smoke escaped! The new cRio has been imaged and the drive train works, validating the changes we've made from our preseason designs chain tensioning. Everything (and I do mean everything), has been labeled and for the first time ever we have some semblance of logic behind our PWM, breaker and motor assignments.

All that's left is lots of little wiring tasks and resolving the inevitable fitment issues between the two major and separately manufactured robot subassemblies.

Oh, and I guess programming. We'll probably want to budget, like, a half hour for that.

[JamesCH95]

A complete function check, from the electronics perspective, is complete. Everything talks to everything else the way it should. Tonight is an actuation check... hopefully everything works as advertised.

Added some frosted lexan backers to set off LED light in the "95" cut-outs.



We now have a nice, reliable, set of mounting points to connect the deck and drive base. We still have a good view of important lights, gauges, etc.



A shot of the deck on the drive base with everything deployed.

[Andrew Schreiber]

Got a part number for those hinges?

[Ty Tremblay]

Originally Posted by Andrew Schreiber

Got a part number for those hinges?

http://www.mcmaster.com/#piano-hinges/=qjss18

[Answer42]

Is this the magical just passing bot I've been waiting to see? Also, glad to see that your brakes are a lot sturdier now.

[JamesCH95]

Originally Posted by Andrew Schreiber

Got a part number for those hinges?

The locking hinges: http://www.mcmaster.com/#1604a43/=qjtc7k (what I assume you want)

The piano hinges: http://www.mcmaster.com/#1581a561/=qjtcck

Originally Posted by Answer42

Is this the magical just passing bot I've been waiting to see? Also, glad to see that your brakes are a lot sturdier now.

Indeed. Passing, ground loading, and one heck of a catching mechanism.

Thanks, and thanks for pointing out/reminding us of the issue in the first place. It took a good bit of brainstorming and a few failed attempts (three?) to arrive at that solution. I think it'll work pretty well.

[JamesCH95]

Ah... one of the reasons I love doing FIRST. A students was shown how to do a difficult task, and then they 'get it' immediately.

These are the current-sensing chips a sophomore student soldered last night, one of their first times soldering too. Every single chip worked, none were overheated and no joints were missed. Only basic equipment was used. We can't tell the difference between the one a mentor did and the ones the student did.



Again, apologies for the cell phone pic.

[Caleb Sykes]

Our team is going to have a very similar design as yours. I am curious to know if you can hold more than 1 ball at a time relatively easily (for autonomous). Would you be so kind as to post results or PM me when/if you attempt to do so?

[JamesCH95]

Originally Posted by inkling16

Our team is going to have a very similar design as yours. I am curious to know if you can hold more than 1 ball at a time relatively easily (for autonomous). Would you be so kind as to post results or PM me when/if you attempt to do so?

Based on past experience with this type of mechanism it should be fairly easy. The order of operations would be: deploy rear carwash, run the rear-ward carwash in to grab a ball off the ground and pinch it against the bumper, drive forward to the low goal, run both carwashes at the same time towards the goal, pushing both balls in.

Might work, haven't tested it yet since we're being plagued by control/wiring issues.

[JamesCH95]

Here are a few videos from yesterday. We finally got everything working together: the automatic 2spd drivetrain, carwashes, and flower petals.

inkling16 - We did try various ways of carrying multiple balls at once, it seems like it will be very easy to carry 2 balls at once for autonomous. We plan on doing some more testing once the bumpers are ready.

We tried a few different ways of catching the ball, and as soon as our ball-retaining mechanism broke (snapped a few bits of string) we tried actively catching the ball, i.e. closing the blossom before the ball had a chance to bounce out. It worked pretty well.

https://www.youtube.com/watch?v=scz6LEt_D_M

https://www.youtube.com/watch?v=uL7XIHzCm_w

https://www.youtube.com/watch?v=Eak27I1cJbo

https://www.youtube.com/watch?v=kYI3Xv5LaPw

https://www.youtube.com/watch?v=nMoalLT3IpM

https://www.youtube.com/watch?v=KmG-7fNlTXA

[JamesCH95]

A little ground-loading action.

http://www.youtube.com/watch?v=1jsviL2X-TQ