13-12-2011 12:09

MattC9

Re: pic: 816's 2011 Off-Season Teaser

Are they gripper parts? It looks like a pulley with a hex broach and something else with a hex broach

13-12-2011 12:17

Andrew Schreiber

Re: pic: 816's 2011 Off-Season Teaser

That's no pulley! (I cannot confirm or deny that I am watching star wars)

I assume I'm ineligible for this...

13-12-2011 12:31

Nick Lawrence

Re: pic: 816's 2011 Off-Season Teaser

A little hint to stir the crowd;























It does cool stuff.

-Nick

13-12-2011 12:53

sithmonkey13

Re: pic: 816's 2011 Off-Season Teaser

Isn't anything robotics related cool?

13-12-2011 13:07

AdamHeard

Re: pic: 816's 2011 Off-Season Teaser

A double sprocket before the teeth are hobbed, and the cylinder is likely a wheel hub to be press/cast into a plastic wheel.

13-12-2011 13:25

Andrew Schreiber

Re: pic: 816's 2011 Off-Season Teaser

No, it is a system for keeping the Fro fluffy.

13-12-2011 13:28

thefro526

Re: pic: 816's 2011 Off-Season Teaser

Dang it.

You're right, though I hoped that it'd take a little longer to figure out.

The part on the left is a blank for a 22T double sprocket, made from 7075 Aluminum. It's been broached before the sprocket cutting to make things a little easier for the mill operator.

The part on the right is a 'plug' for a 2" wide colson wheel, made from 6061 AL. Preliminary testing shows that the press is good to at least 80 foot-pounds of torque.

(I'll have to bug you on FB for a shipping address once the stickers are made.)

13-12-2011 13:29

CNettles11

Re: pic: 816's 2011 Off-Season Teaser

I'm pretty sure that the smaller item could be part of a cable winch. Could the larger item be an adapter from a hex shaft to a different type of shaft?

EDIT: Dangit, I was both late and wrong.

13-12-2011 14:15

rcmolloy

Re: pic: 816's 2011 Off-Season Teaser

Oh I see where you're going with this one Dustin. The topic that we were discussing about makes sense then.

...Or just give them to me for hand delivery dude. We don't live that far away.

13-12-2011 14:23

Andrew Schreiber

Re: pic: 816's 2011 Off-Season Teaser

If you guys can wait until Madera I can hand deliver them as long as they go next to the "Powered by..." sticker on your bot

13-12-2011 14:27

roystur44

Re: pic: 816's 2011 Off-Season Teaser

Drain plug to keep the water out and a small anchor???

13-12-2011 14:35

Brandon Holley

Re: pic: 816's 2011 Off-Season Teaser

I've been making a variation of the press-fit Colson hub since 05 using the same principle. If I'm seeing the hub correctly, it looks like its knurled which is something I've had great success with as well.

Looking good.

-Brando

13-12-2011 14:42

AdamHeard

Re: pic: 816's 2011 Off-Season Teaser

For season I see the resources used to make the double sprockets better used elsewhere, and instead just purchase off the shelf sprockets.

13-12-2011 15:35

rsisk

Re: pic: 816's 2011 Off-Season Teaser

Why do I get the feeling there is going to be a heck of a good time had at Madera?

13-12-2011 15:41

thefro526

Re: pic: 816's 2011 Off-Season Teaser

Hehehehe. I don't know if you're fully aware of how ridiculous our current project is.

Brando, Technically the hubs aren't knurled. The grooving that is visible in the picture was done by running a tool at a relatively high rate across each plug. Technically, it's not the right way to create a strong press because the cuts are in the same direction as the wheels would see force but I'm very happy with the results so we'll probably just stick with this method since it's easy for our Lathe guy to knock out - and it's pretty easy to replicate in house with minimal skill/effort.

Adam, you're right on the money with this. I doubt we'll do a run of double sprockets again unless they're absolutely needed or it makes sense to do so.

This entire project is heavily influenced by a few factors:

-We wanted to try some new construction methods.
-We wanted to build a lighter more competitive drive than what we used in 2008.
-We wanted to move to an 'assembly' style build method.
-The shop foreman at our machine shop told me to design something 'interesting' for his guys to make - one thing lead to another and yeah....

Here are some more pictures for those of you that are interested:

13-12-2011 18:45

craigboez

Re: pic: 816's 2011 Off-Season Teaser

I assume your hex broach goes all the way thru the ~2" wide Colson hub. Did you have any issues hex broaching that length? The Dumont literature states the max length of cut is 1-3/8" but that is based on mild steel. I'm curious what it can do in aluminum.

13-12-2011 19:23

Cory

Re: pic: 816's 2011 Off-Season Teaser

I can tell you from our experience that would likely be a problem and require it to be broached multiple times, or from both sides (with a standard push broach). It's going to take a LOT of force too, since you have so much tooth engagement.

13-12-2011 19:53

ttldomination

Re: pic: 816's 2011 Off-Season Teaser

Where do you guys go for your off the shelf double sprockets?

- Sunny G.

13-12-2011 20:21

AdamHeard

Re: pic: 816's 2011 Off-Season Teaser

We just use two single sprockets. Makes all of our drive sprockets the exact same.

13-12-2011 21:38

craigboez

Re: pic: 816's 2011 Off-Season Teaser

AndyMark has a few
http://www.andymark.com/SearchResult...ouble+sprocket

14-12-2011 03:07

waialua359

Re: pic: 816's 2011 Off-Season Teaser

Team 2348 has been making our double sprockets for the past 5 seasons for our "West Coast" bicycle chain drive.
As suggested, we should instead just buy them if possible. A lot of time, energy and round stock is used.

14-12-2011 08:54

thefro526

Re: pic: 816's 2011 Off-Season Teaser

As far as I can tell, the Colson hex may need to be cleaned up a bit. It seems to need to be opened up by a few thousandths, or we might just undersize our shafts a bit. The press we used was massive, I can get the tonnage if anyone wants it. Didn't seem like it took too much force compared to the depth of the broach.

14-12-2011 09:01

Brandon Holley

Re: pic: 816's 2011 Off-Season Teaser

Ah- yes the mental picture popped into place. Knurling is really REALLY simple (and pretty cool). It could be something you guys experiment with now, especially since you already have the lathe, etc.

The gearbox plate looks good. I assume bearings will be pressed into it. I'd be curious to see what results you get as far as the tolerance on the press fit from a waterjet. We've had access to a waterjet for a while, and we use it for a lot of things. One thing I've always been wary about is bearing holes though. We usually will cut out almost the entire part and then go back to correct the bearing holes with a secondary process.

-Brando

14-12-2011 09:20

thefro526

Re: pic: 816's 2011 Off-Season Teaser

We might experiment with knurling in house before build, but we have about a dozen other parts that are on the priority list first. Our sponsor can knurl if we absolutely needed it too.

The bearings are more of a tight slip fit then a true press. I can get a good measure on the bore when I go to the shop tonight. We have originally intended to ream the holes under the assumption that they'd run under, but they came out of the waterjet just right it seems.

Got one of the finished Sprockets:

30-12-2011 21:13

thefro526

Re: pic: 816's 2011 Off-Season Teaser

We hit some snags with the kids on winter break, so the axles are keeping us from getting this guy running. Here's how we left it before the Holidays:



My lathe guy assured me that our parts would be done by our next meeting, so we'll see if this thing runs before Kick-off.

Here's a render of the finished product that I may as well post up since someone (Andrew...) made me talk about it in the EWCP Christmas Cast:



And Brando, to follow up, I had the chance to test the press fit on one of the colson plugs at the machine shop with a few of the guys. Pressed the hub into the colson, clamped the wheel into the vice, then used a Torque Wrench to apply Torque. We found out that I wan't strong enough to apply more than 80 ft-lbs of Torque before stopping. (Interestingly enough, the tread of the wheel started to deform after ~50ft-lbs of TQ or so, pretty sure they'll rarely see more than that during competition.)

31-12-2011 10:25

Brandon Holley

Re: pic: 816's 2011 Off-Season Teaser

Sweetness.

Yeah with those what I assume are polypropylene hubs you can do quite a generous interference fit. I think last year I had a .010" interference and pressed the hubs in with no problems, and never had an issue with slipping them. I imagine you will see similar success.

I'm curious about the 10WD tho. Are you guys just playing around with possibilities, or do you feel there is a strategic advantage to the 10WD?

Looks slick.

-Brando

31-12-2011 12:57

Akash Rastogi

Re: pic: 816's 2011 Off-Season Teaser

The 10wd is to test a couple drive configurations as you guessed.

Am I the only one who thinks Dustin's CAD looks like a bug for some reason?

31-12-2011 13:24

thefro526

Re: pic: 816's 2011 Off-Season Teaser

Haha, this is the question that everyone has asked.

10WD is is to change Drive trains on the fly, we can pull two bolts and make it an 8WD, Four bolts to man a 6WD, so on and so fourth. Should help the kids get a real world understanding of Drive trains.

The side note to this is that we'll be using this as a testing rig to see what wheel configurations perform the best and to see if the number of wheels increases and or decreases performance. Should be interesting...

31-12-2011 15:19

Brandon Holley

Re: pic: 816's 2011 Off-Season Teaser

So are the center 6 wheels all on the same plane?

31-12-2011 19:16

thefro526

Re: pic: 816's 2011 Off-Season Teaser

Correct, the center 6 Wheels are 1/8" lower than the outer pairs.

05-01-2012 14:56

thefro526

Re: pic: 816's 2011 Off-Season Teaser

Just wanted to Follow up on Cory's post in case someone stumbles onto this thread in the future.

Each part, especially the hubs, did need to be broached multiple times. We've found that most Aluminum Hex runs a few thousandths over, which was enough to make assembly a PITA. If I counted correctly, each sprocket has now had the broach pressed through it three times, once to do the primary cut, two more (each from a different side) to open the hex up enough that it plays well with hex shaft. The wheels each took between 3 and 4 passes a piece before they played nice, again alternating sides with each pass.

With any luck, this should be running tonight.

05-01-2012 15:16

Brandon Holley

Re: pic: 816's 2011 Off-Season Teaser

Come back with vids.