pic: Team 100 Prototype Base - Underside

[=Martin=Taylor=]

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

Looks nice!

[Qbranch]

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

[=Martin=Taylor=]

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!

Originally Posted by Qbranch

...and sports 1" center free fit holes accomadating 1/4"-20s...

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

Originally Posted by Hachiban VIII

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!

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.

[DonRotolo]

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

[MrForbes]

Originally Posted by 114ManualLabor

Our previous drive base(07 season), with electronics, pneumatics, and motors was 45 pounds, and it was too heavy for me.

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.

[Travis Covington]

Originally Posted by Hachiban VIII

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 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.

[s_forbes]

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...

[Madison]

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.

[Dan Petrovic]

Originally Posted by Qbranch

*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.

-q

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.

[=Martin=Taylor=]

Originally Posted by InfernoX14

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

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.

Originally Posted by M. Krass

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?

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

[Jeff K.]

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?

[Cory]

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.

[Brandon Holley]

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.