20-12-2007 17:33

Re: pic: Team 100 Prototype Base - Underside

55 pounds is pretty heavy... Why the bosch extrusion, as opposed to something lighter, such as 1x1 box extrusion, or C channel?

Looks nice!

20-12-2007 17:43

Qbranch

Re: pic: Team 100 Prototype Base - Underside

Hey hey show a little modesty! We don't go around turning YOU upside down and taking pictures!

*chuckle* Anyhow, on the more nuts-and-bolts side of life, for what you're building there, why not use a Kit Bot frame from IFI? It's rock solid strong, really light, and sports 1" center free fit holes accomadating 1/4"-20s. I know it sounds tacky to use a kitbot frame... but really, its tough to beat for strength/weight balance.

Are the transmissions AndyMarks? Hard to tell from here.

Looking good... NICE wheels, did you all make them?

-q

20-12-2007 17:47

pakratt1991

Re: pic: Team 100 Prototype Base - Underside

Wow 55 pounds is pretty beefy, I agree with Manuallabor, go with some extrusion, either 1X2 or if you like the shape if the bosch extrusion you could go with a 1X2. Although this might require you to build in some cross bracings. I know that bosch stuff is pretty solid.

Are you planning on using the old andymark transmissions or just waiting on build season to order some super shifters?

On a side note, I was able to shift both of our transmissions last year using only 1 of the pistons with an extender build on. I can include some pics if you're interested. Although our transmissions were modified to be thinner, and thus lighter, I do not know if you can do it with an unmodified set, but might be interesting to look into anyways.

20-12-2007 17:50

Re: pic: Team 100 Prototype Base - Underside

Shifting with only 1 cylinder has its perks, but it's not for every system. If your transmissions are centered in your bot, it makes it annoying to rout different subsystems around the cylinders, and it also limits putting a chassis member there. We did this for our 2k5 bot, AimBot. It works best if the transmissions are direct driving one of the front wheels (or in your case, front pulley.)

PS, pakratt, wanna have sam shoot me an email? We're doing pre season planning, and I'm interested in a few details for the upcoming season. Thanks!

20-12-2007 17:58

pakratt1991

Re: pic: Team 100 Prototype Base - Underside

Will do, A mentor and a few students (including myself) are heading up to his shop on the 28th, so we will know much more after that.

I guess he plans on modifying some super shifters and using them, there is a little bit of modification needed to make them mirror one another, we also plan to drop a couple of pounds from the trannys.

20-12-2007 18:27

=Martin=Taylor=

Re: pic: Team 100 Prototype Base - Underside

I'm a little confused why you all think this is so heavy. That weight includes our entire electronics board; drive motors, air-tank, and compressor. There is a full 65 lbs. available for a scoring device. Last year's drive train weighed 50 lbs. without electronics, pneumatics and the upper frame! And we never had any weight issues!

I hate those little holes. They are always exactly where you don't want them to be! Which means that you have to create an oval-shaped hole to bolt on the desired part.

This is exactly why we use the bosch. The 80/20 has linear grooves that make attaching anything a breeze. It also makes tensioning chains very easy, just slide the pillow blocks down the grooves and tighten the bolts. We only use it in the base to save weight.

Our team used the Kit Bot in 2006 and it was a big pain. There just isn't a good way to keep things adjustable with it.

As for the wheels we bought them from Andy Mark. Our little CNC isn't powerful enough to make a wheel in a reasonable amount of time. It would take all day to make one wheel! The AM Performance wheels are great, but they're really expensive. Next year we'll probably just use two of them in the middle and the kit wheels on the corners to save weight and money

20-12-2007 19:43

Re: pic: Team 100 Prototype Base - Underside

Our previous drive base(07 season), with electronics, pneumatics, and motors was 45 pounds, and it was too heavy for me. My current drive designs, with all materials set correctly, weigh in around 38-40. The heavy end is the Crab, which is 50. Just because the drive base is light, doesn't mean the weight of the bot will be high. You can always design low, with very light upper members.

20-12-2007 19:56

DonRotolo

Re: pic: Team 100 Prototype Base - Underside

Nice concept. Those corner braces will eliminate most of the need for bracing, and the electronics board can go a long way towards rigidity as well.

Is that #25 chain or #35?

Thanks,
Don

20-12-2007 20:02

MrForbes

Re: pic: Team 100 Prototype Base - Underside

Why is that too heavy? the 100 robot fell over in a match (with some help )....seems to me that means the drive base could have been heavier, which would have forced them to keep weight off the top of the robot, and make the whole thing more stable.

Weight down low isn't necessarily a bad thing.

20-12-2007 20:03

Travis Covington

Re: pic: Team 100 Prototype Base - Underside

I wouldn't worry about it. I think it's perfectly reasonable. You've also got the two larger CIMs on there which weigh considerably more than the smaller ones.

You guys need to ease up and give them some credit. I think this is one of the better put together systems I have seen posted on CD in a while - not to mention they actually succesfully built it and tested it. It is also one of the more creative solutions that I have seen...

It's pretty sad that I'll be the first one in this thread (Edit: aside from the last two) to give them a thumbs up on the whole thing. There isnt much I would change, as I am sure they have seen the alternatives and have weighed those options against this chosen design.

20-12-2007 20:16

s_forbes

Re: pic: Team 100 Prototype Base - Underside

Looks great! I like the simplicity of it, particulartly the lack of chain tensioners. Those axle mounts seem like a nice simple solution as opposed to the CNCd ones we usually see. Nice work.

The weight sounds about right, too. If you need more than 65 pounds for your manipulator, then the drivetrain isn't the part you should be redesigning...

20-12-2007 21:18

Dan Petrovic

Re: pic: Team 100 Prototype Base - Underside

I wouldn't really consider the kitbot frame rock solid strong...

C-channel has about half as much torsional strength as box tubing even though it has only one less side.

20-12-2007 21:39

Madison

Re: pic: Team 100 Prototype Base - Underside

I'm happy to see you all got this built. Prototyping in the off-season is an invaluable experience for new and experienced team members, allows you a chance to safely try new ideas, and helps you to work out the kinks in your manufacturing processes. Even if, on the day of kick-off, you have to throw this design out (...and I hope that you won't...) or rebuild all of your modeling and design work from the ground up, it's worth the effort.

55 lbs. is respectable -- especially with a pneumatics system on board and two of those large CIM motors. That alone probably represents ~15 lbs. of your total weight. The 1x2" extruded profile is a bit heavier than rectangular tubing, yes, but that penalty may be worth the time saved in labor. We finished our prototype chassis, for the most part, back in early November. It's 30 lbs. -- but that's with two motors and no pneumatics system -- and it required considerably more manufacturing effort. The most recent iteration incorporates a lot of the features y'all have here and, though it's a few pounds heavier, involves far, far less work. It's a worthwhile compromise.

If you don't mind answering a few questions:

-- From what are the bearing blocks made? They look like they're 1/4" thick, overall dimensions of 2.25 x 1.5. McMaster-Carr, nor onlinemetals.com, seem to carry stock of these or similar dimension. Are they custom made?

-- What machining work was done to the 1x2 extrusion to accomodate the axles?

-- Where'd you find 1/2" bore, keyed sprockets for #25 chain? What were lead times and cost like?

Thanks for sharing this.

20-12-2007 22:17

=Martin=Taylor=

Re: pic: Team 100 Prototype Base - Underside

Our team did a stress analysis a while back and determined that the kitbot was actually quite strong. I think its infamous reputation comes from teams cutting notches in it and weakening its structure. Left in its original state it is very strong.

No problem

--Wow that’s the exact dimensions ! We searched and searched for channel stock that came in these dimensions, but it didn't exist . So we just purchased a 2.25 x 1.5 block from a local metal supplier and machined a 1 x 2 slot in it. It took forever on our little mill, but our sponsor will probably be able to get it done in an afternoon.

--We just cut two 0.75" long slots on either end with a 0.75" end-mill. The center slot is vertical, allowing the center wheel to be raised or lowered an 1/8 of an inch.

--McMaster Carr. We had to machine them thinner and broach them, but it wasn't too hard. Just like everything else they carry the sprockets were cheap and arrived soon

20-12-2007 23:14

Jeff K.

Re: pic: Team 100 Prototype Base - Underside

This is a really nice example of a modifiable prototype chassis. 55 lbs ain't bad, our mecanum base last year was 80 lbs, while the arm was 30 or so. With all the weight down low, we never were close to tipping over. The method of tensioning is also a pretty slick idea. How heavy are the wheels? Will you be using a similar chassis layout with the box extrusion?

21-12-2007 00:10

Cory

Re: pic: Team 100 Prototype Base - Underside

Pretty cool guys. I agree with Travis. Looks extremely well designed. Wish we had ever had our acts together enough to have an offseason project as nice as that when I was on the team

For those criticizing the weight, there's all kinds of weight they could easily remove. The sprocket hubs can be turned down. The gears in the AM shifters can be lightened. The big CIM's can be swapped for small CIM's.

Even without swapping the CIM's, I'd say they could cut 2-5 lbs pretty easily.

21-12-2007 00:25

Brandon Holley

Re: pic: Team 100 Prototype Base - Underside

I would not worry about the 55 lb drivetrain you got there. With electronics that is a PERFECTLY acceptable weight. I like the whole setup you got here. Good job.

21-12-2007 01:18

Blue_Mist

Re: pic: Team 100 Prototype Base - Underside

It's organized and simple, and very light for a drive train and frame and electronics and pneumatics. However, as Squirrel said, weight down low isn't a bad thing. We try to keep a low center of gravity and almost never tip, although the ramps were sometimes a problem and we aren't considered fast. I like how neat and clean the chains are- no tensioners. If I may, I think the motor wires might do better tied against the frame to keep them out of the way. Just my opinion. I do like the frame extending to protect the wheels in the front and back. That would be a nice place to put bumpers; mount them with bolts on either side of the wheels. And good looking welds, too, from what I can see.

21-12-2007 14:40

Re: pic: Team 100 Prototype Base - Underside

Sorry for bashing the weight. I spent too much time thinking about that one number. It is quite the nice system. How quick is tensioning?

Also, do you happen to know around how much the electronics board in whole weighs? I'm curious as to whether or not this thing would be lighter with a less hefty board.


Very nice, and props on getting something together before the season! I know it's not easy, as all of my attempts at doing this have been shut down.

Props!

21-12-2007 15:46

MrForbes

Re: pic: Team 100 Prototype Base - Underside

A piece of plywood can be kind of heavy, or not....depending on what you use. 1/8" lauan plywood is fairly rigid, light, and not very expensive, usually available in part sheets from big building supply places.

21-12-2007 16:56

=Martin=Taylor=

Re: pic: Team 100 Prototype Base - Underside

Its a sawed off piece of our 06 ramp, I believe its 0.5" thick. We also used four different fuse boxes because that was all we had. I think the major weight came from the Big CIMs. As Cory said, those big CIMs weigh significantly more than the small CIMs. We used them because we didn't have any of the small pinion gears that are needed for the small CIMs in the AM shifters.

Tensioning is really easy. You just loosen three bolts and slide the bearing block into place and tighten it down. And no, the blocks don't slip. The chains will stay tight until they begin to strech.

Yes, there are many things we could have done to lighten it. But it all would have taken time and money and the purpose of this system is to create a simple prototype base.

For the competition version we may use 7075 or 7068 aluminum for the axels. Any advice on that?

21-12-2007 20:33

Cory

Re: pic: Team 100 Prototype Base - Underside

Nothing too special you need to do. ours are just plain old 7075 1/2" main diameter, with 7/16" hexes on either end. No heat treatment or hardening necessaary

21-12-2007 22:45

Ross340

Re: pic: Team 100 Prototype Base - Underside

340's proto frame weighs somewhere around there made of 3/4 bar stock. it's so bulletproof. We love it.

21-12-2007 23:24

team2061

Re: pic: Team 100 Prototype Base - Underside

What is being used to hold down the electronics and other stuff because in the 2007 season we screwed and bolted everything down.Bad idea it bit us in the butt big time.I heard zip ties are the best way to go.

22-12-2007 15:11

caraddicted101

Re: pic: Team 100 Prototype Base - Underside

I have seen some teams use zip ties as they are easy to cut and replace, I have also seen some teams use strong Velcro, as it is even easier to change a component then zip ties. As for me, we had a little room and just put a few extra spikes on the robot unwired that way we would only have to pull the wires off the bad one and we would be good to go.

22-12-2007 22:24

Andy Baker

Re: pic: Team 100 Prototype Base - Underside

This is a great drivebase. Kudos to you for not only getting a prototype put together in the off-season, but also having the guys and GP to post it on this site, for all teams to see.

The only advice I can think of at this time (for your competition version) is for a different material for the electronics board. The plywood is lightweight and easy to use, but a perforated sheet material (aluminum or gray PVC) works great. If you use this sheet, there is no need to drill holes when you mount your electronics and route your wires. I would suggest 3/32" thick aluminum or 1/8" thick PVC perforated sheet with 3/16" dia holes to start with. McMaster-Carr, MSC and other places sell this stuff.

Andy B.

22-12-2007 23:09

lukevanoort

Re: pic: Team 100 Prototype Base - Underside

This looks really solid guys! Doesn't quite have the intimidation factor of those massive pneumatic wheels that your last drive base had, but I imagine it'll serve you guys much better! In the last couple of years, we finally abandoned big pneumatic wheels as well, and we'll probably never go back; it is so much simpler not to have to worry about whether wheels are equally pressurized, if anyone packed the tire pump, whether the tire is leaking air, and so on. (much lighter too)

I was planning on using the perforated aluminum on our robot next year, but I'm curious about how well it (and PVC too, which actually sounds like a more attractive material to me) handles the weight of the circuit breaker panels and the distro block. Have you experienced any issues with tearing or extreme bending with the heavier parts?

23-12-2007 11:27

AdamHeard

Re: pic: Team 100 Prototype Base - Underside

Allways good to see teams being productive in the off season.

55 Lbs isn't bad at all, especially with the possible weight savings of a lighter board and the small CIMs.

Also, I'm liking the very minimal amount of fabrication that had to be done.

Overall, great job. I'll be sure to look out for it at silicon valley.

23-12-2007 16:52

=Martin=Taylor=

Re: pic: Team 100 Prototype Base - Underside

We usually use 1/8" ABS plastic for the board. But its kinda expensive to waste on something that will never see competition.

Yes, all the components are held on with zip-ties. This is a great way to attach stuff IMO. We just drill one hole, stick a zip tie through, and stick another zip-tie on the bottom. This creates a little plastic bolt that can be cut and replaced as needed.

23-12-2007 19:54

kramarczyk

Re: pic: Team 100 Prototype Base - Underside

You may want to plug and chug this spreadsheet to play with various materials and diameters. It also includes the possibility of drilling them out.

http://www.chiefdelphi.com/media/papers/1998

29-12-2007 23:57

robostangs548

Re: pic: Team 100 Prototype Base - Underside

Looks nice, I bet you with my experience in lightening, that, I could help you loose about 10-12 off of that 55. Other then that looks nice!