31-03-2016 19:01

JohnFogarty

Re: pic: Team230 Damaged Frame Rail

What thickness tubing is that? What kind of wheels did you use?

31-03-2016 19:26

Jay H 237

Re: pic: Team230 Damaged Frame Rail

Looking at that I'd guess that adding a spacer in there would have helped by not allowing the walls to fold in and tear even with the same thickness aluminum material. Those thin walls were the only thing supporting the axles.


I was at Waterbury both days and some of those robots hit the defenses at high speed and caught air at times. You really don't know at times how well some parts will hold up until you give them the real live test!

31-03-2016 22:55

AndrewMorrison

Re: pic: Team230 Damaged Frame Rail

At least it wasn't caused by us this time!

01-04-2016 11:54

electroken

Re: pic: Team230 Damaged Frame Rail

That's 0.062" wall thickness 6061-T6 tubing. The drivetrain is 6WD, 8" pneumatic tires in a WCD (cantilevered) configuration.

It was the ramparts that did us in, with that big shot to one wheel at the start of each crossing. We told our driver to drive it as if he stole it, and he did not disappoint.

A spacer within the tube may have bought us time, but failure was inevitable. the other side of the tubing has significant stress cracks. As it was, the thing made it halfway through its 17th match before it failed. The new frame ( 0.125" wall thickness) seems bulletproof so far. We would have started off with that if we'd fully understood the brutality of this game.

01-04-2016 11:55

electroken

Re: pic: Team230 Damaged Frame Rail

Not his time, but district champs are coming up.

01-04-2016 13:25

JohnFogarty

Re: pic: Team230 Damaged Frame Rail

Yeah all of the teams I work with are using 0.125" frame rails and we haven't seen any damage at all.

01-04-2016 13:27

PayneTrain

Re: pic: Team230 Damaged Frame Rail

You said this drivetrain was in a WCD configuration, but you seem to have described a timebomb.

Source: built a timebomb in 2014. It was not fun.

08-10-2016 19:56

chrisfl

Re: pic: Team230 Damaged Frame Rail

Now that the season is over, could I ask how well the 1/8" wall tubing held up? Would you need bearing blocks with the 1/8" tubing like with 1/16"?

08-10-2016 21:33

Billfred

Re: pic: Team230 Damaged Frame Rail

I can't speak for 230, but 4901 never replaced any of their 1/8" wall tubing through two competitions and demos. The final exam would be next weekend at SCRIW.

08-10-2016 22:32

JohnFogarty

Re: pic: Team230 Damaged Frame Rail

We've also been doing some playing with our 2016 robot at off-season outreach events quite a bit. I can say with some certainty that 0.125" wall tubing holds up without bearing blocks.

08-10-2016 23:18

Eric Scheuing

Re: pic: Team230 Damaged Frame Rail

.125 tubing checking in, we're good with no blocks and no spacers.

09-10-2016 03:23

nathannfm

Re: pic: Team230 Damaged Frame Rail

MOE also used 1/8" wall but with press fit rings bridging the gap between the inner and outer bearings, still runs great after 80 matches and a few miles of parade route.

The drive is not something you want to take...lightly...

09-10-2016 11:49

mott

Re: pic: Team230 Damaged Frame Rail

1619 ran an 8WD with 6" pneumatic wheels/tires in a West Coast config with bearings pressed directly into .1" VEX 1"x2" tubing with zero issues. Our machine competed at 2 regionals, Champs, IRI and a handful of "street demo" events (where our students decided to use curbs and parking barriers as makeshift Defenses).

Running spacers inside the tube wouldn't have been an option for us because we run a chain-in-tube set-up.

09-10-2016 12:40

chrisfl

Re: pic: Team230 Damaged Frame Rail

Thank you all for the insights. Our team has been looking into trying a west coast drive this fall and this really helps. What other tips or tricks do you guys have in regards to west coast drive?

09-10-2016 12:58

Billfred

Re: pic: Team230 Damaged Frame Rail

Whether 4901's design really is or isn't WCD is a fair question (we supported both ends of the shaft out of concern for the game), but we were running chain-in-tube as many WCDs do.

1) When dead-spacing chain, the term "designing an even number of links" means "2, 4, 6, 8" not "integer". Use a calculator; we like this one.
2) If you must run half-links because you ignored #1 or had a very good reason, make it the kind that don't have the little retaining pin you bend. That pin will be busted off by the other chain, and you will throw it, and you will be fishing new chain into your tube. (McMaster-Carr sells the good stuff.)
3) Dark Soul tool is so much better for making complete chain loops than any master link. Even the normal master link will, invariably, be busted off and you will throw a chain.
4) Design your drivetrain so you can get the main rail off without too much fuss. Riveting your belly pan every inch or so is too much fuss. (This was our greatest issue once we sorted out the chain; haven't designed a better plan yet.)
5) Drive your drivetrain early and often, to make sure your teething problems happen at home and not at your event. (You should be doing this anyway, but especially when you're doing a new-to-you drive system.)

09-10-2016 17:07

Cothron Theiss

Re: pic: Team230 Damaged Frame Rail

Do you have any preliminary thoughts on how to design a belly pan such that the main rails can be taken off easily? I think that's a tough balance to find, considering that a belly pan has to be mounted properly to impart torsional strength to the chassis. Do you know of any teams that have worked this out?

09-10-2016 17:17

BrendanB

Re: pic: Team230 Damaged Frame Rail

2590 Nemesis would be a great team to chime in on this. I know in 2014 and 2016 their rails were designed to be removable.

09-10-2016 17:59

Cothron Theiss

Re: pic: Team230 Damaged Frame Rail

Those are some gorgeous drivetrains. You can see a lot of thought when into many critical factors. The staggering of the rivets to not interfere with the runs of chain, the flexible coupling on the back axles for encoder mounting, and the way they've done the tabs in the belly pan are things I'll have to remember.

10-10-2016 10:57

Thayer McCollum

Re: pic: Team230 Damaged Frame Rail

https://drive.google.com/open?id=0B4...Q3RxV Wo2QTVJ

So I'm wondering if more teams do this? ^^ It's hard to tell from the picture but we welded thick wall aluminum tube (can't remember exact thickness) into the rail and then machined the weld flat and used a boring bar to achieve the diameter we wanted for the bearing. I feel like this would have prevented the damage to the rail in the original picture. What are your thoughts? Why don't other teams do this? Is it unnecessary? Do I just have no idea what I'm talking about? I am very curious.

10-10-2016 11:17

Billfred

Re: pic: Team230 Damaged Frame Rail

I think it falls under "valid, but overkill for all but the most brutal of games". If wall thickness was a concern, doing something like 148 did with reinforcement plates at the bearings is probably a simpler method for most.

10-10-2016 11:49

Chris is me

Re: pic: Team230 Damaged Frame Rail

Teams usually use 1/8" wall aluminum tubing for their drive rails, which prevents the problem. Some teams use bearing blocks or shims to provide even more material support to the bearing than the 1/8" wall tubing, which is safer. It's quite uncommon to use 1/16" wall tubing for drive rails at all, and I generally think it's not worth the weight savings to do so.

Your solution is essentially a welded-in bearing block, which seems overkill, especially compared to the various other bearing block solutions teams can come up with that aren't so tricky to machine and install. It'll work, but there are better uses of your time, and it'd be better to just not use 1/16" tubing for supporting bearings directly.

10-10-2016 18:36

Thayer McCollum

Re: pic: Team230 Damaged Frame Rail

So I suppose I should have clarified. I agree that structurally the tube concept is overkill. It adds support the rail doesn't really need. We did this because we felt that just pressing the bearings into the rail would cause them to fall out easily. Is that not the case? Does 1/8" wall easily support bearings without them falling out? Because in my experience that hasn't happened. If someone could tell me how to put the bearings in without them falling out I would be happy to learn. (Because those tubes really sucked to put in...)

10-10-2016 19:45

Billfred

Re: pic: Team230 Damaged Frame Rail

For us:

1) Machine the hole just slightly undersized. Adjust it lightly when it's necessary.
2) Minimize axial slop on your axles. If your wheels can't slide back and forth on the axle, it makes it harder for it to wiggle the bearings too. (E-clips help with this.)

10-10-2016 22:45

Joe Finkel

Re: pic: Team230 Damaged Frame Rail

1. RIM THE HOLE.
2. E-CLIP
3. RETAINING RING
4. SCREW AND A WASHER AT THE END OF THE AXLE

10-10-2016 23:04

Chris is me

Re: pic: Team230 Damaged Frame Rail

Bearing retention really has very little to do with the wall thickness of the material the bearing is pressed in. How the hole is sized is the biggest factor, really. Machine the hole a thou or two undersize for a nice press fit, but not so much under the bearing will seize. If you can't do this, using green loctite (gap filling) will help hold the bearing press fit in securely. Otherwise, you can use the hardware on your shaft to hold your bearings in (spacers, etc).

I would definitely not recommend an E-clip to do this if the E-clip is between loads, only on the end. And even then a snap ring is simply the better tool for the job.

10-10-2016 23:05

Fusion_Clint

Re: pic: Team230 Damaged Frame Rail

Why are the holes offset from each other? It appears that the inner hole is at least 0.125" further to the left as pictured that the outer hole showing the damage.

11-10-2016 09:25

Chris is me

Re: pic: Team230 Damaged Frame Rail

I'm fairly sure that's just the camera angle here; their drivetrain was a fairly normal WCD.

(haha, get it, "normal", I crack myself up)

13-10-2016 10:33

MamaSpoldi

Re: pic: Team230 Damaged Frame Rail

After the rest of a long season... and off-season events... and community events, I can report that the replaced tubing has held up great.