pic: Team 3647 West Coast Drive

[AdamHeard]

I always like seeing a quality base come together, especially with someone so willing and immediate at/to implement suggested changes.

The corner gussets could be 1/16" if you wanted to save some weight, but 1/8" certainly isn't too heavy and is easier to sell to doubting team members.

Definitly change the bolts on those gussets to rivets.

Incorporate from the get go a very rigid bellypan (as you have no internal crossmembers). Metal is nice but can be heavy unless very thing or heavily pocketed. I'd reccomend g-10/fr4 garolite from mcmaster for a VERY strong and light material that also happens to come in glossy black.

I like the changes you made to the gearbox mounting.

Can we get a close up and/or section view of the outer wheel/shaft/bearing block setup? There is a LOT that can be done right/wrong there that really make or break such a system.

On the same note, what are your plans for tensioning?

The reason the gearboxes are somewhat weakly mounted is if you view them completely from the front/back of the robot. They create a moment tryign to peel them off from teh frame, and you only have bolts at one elevation to react this. You really want bolts at two different heights (it deosn't have to be much) to react this. Our bolts are only .75" apart vertically and hold up just fine.

Ditto earlier comments about #10-32's being adequate, our entire drive uses nothing but.

Keep working guys! Very exciting to see, and you're on your way to a very nice drive.

[Bob Steele]

The key to making a six wheel drive work properly is the stiffness of the frame.
I echo the belly pan idea...if you have access to a waterjet it can be done very nicely...

In the absence of a belly pan you might consider cross members... but remember the frame must be really rigid... in all directions.

Another option to help your frame stay rigid is utilizing the bumpers as part of your rigidity... you might as well use them if you have to have them.
By engineering them into the frame...you can gain rigidity ...

take a look at the drive base we posted last week
(1983 is the team number)
We utilize a double side rail.. ours is not a West Coast drive like yours...
We also incorporated the bumpers and their mounting into the frame...legally.

I think too many teams don't think of the bumpers as part of the frame/drive base...rather they think of them as an add-on...

Think of them as integral from the beginning and you can lighten in other areas...

Nice looking CAD work!!

[craigboez]

Originally Posted by AdamHeard

Incorporate from the get go a very rigid bellypan (as you have no internal crossmembers). Metal is nice but can be heavy unless very thing or heavily pocketed. I'd reccomend g-10/fr4 garolite from mcmaster for a VERY strong and light material that also happens to come in glossy black.

I've heard others recommend this stuff too. Any particular thickness that you use? It looks spendy, but if it's worthwhile then it might be worth an order.

[AdamHeard]

Originally Posted by craigboez

I've heard others recommend this stuff too. Any particular thickness that you use? It looks spendy, but if it's worthwhile then it might be worth an order.

We like 1/16th. Runs like $60 per robot and you get a LOT left over for other parts. Mcmaster btw.

[Mk.32]

Why rivets over bolts?
I have currently a 1/8 sheet of poly carb in place as the belly pan, is that not stiff enough?

For chain tension, there are pockets for the bolts/shaft in the bearing blocks to allow them to side .25inch.
I will get a photo of the bearing block step up later.

[BrendanB]

Originally Posted by Mk.32

Why rivets over bolts?
I have currently a 1/8 sheet of poly carb in place as the belly pan, is that not stiff enough?

For chain tension, there are pockets for the bolts/shaft in the bearing blocks to allow them to side .25inch.
I will get a photo of the bearing block step up later.

Rivets are a lot lighter and are a set and forget operation.

[BJC]

You could probably move all the outer wheels a couple inches further out. They appear to be at least 8 inches inside the frame. Also, if the bumpers have to be all the way around the robot as in the last several years the need for the chassis extensions infront of the wheels diminishes except for as a bumper mount. Eliminating that and using the bumpers themselves solidly connected in the corners (such as a single piece bumper) allows you to place your wheels even further out.

Very nice looking chassis, Bryan

[Borobo]

I do not like the look of those gussets. The fact that the frame has no internal bracing and the gussets are so small and have so few holes I think might make it really structurally weak. I would definitely increase the number of holes in each gusset and make them longer so that there is more bracing in each corner. Also, I would recommend another member somewhere in the center.

[Chris is me]

Originally Posted by BrendanB

Rivets are a lot lighter and are a set and forget operation.

Also important to this design - rivets are better in shear than bolts.

[Mk.32]

How big of a rivet? And I assume pop rivet?

[Marc S.]

We use 3/16" pop rivets. These are awesome because they go perfectly in a No.7 hole(clearance for a 10-32). The gussets seem OK in size just as long as your using a good belly pan. It might just be me but it looks like your using 1/8" wall end-rails, 1/16" is plenty strong there.

One thing that will keep your gearbox clean is getting rid of all unnecessary bolts. For instance the same bolt that holds the top of the motor in can also go through the top standoff. If your making these plates with a cnc or water-jet, you can round the corners and try doing some pocketing. If you go the cnc rout then making the plates identical will keep your (cnc)sponsers happy.

[Mk.32]

Would something like this for a belly pan be okay? http://www.andymark.com/product-p/am-0836.htm

[Andrew Schreiber]

Originally Posted by AdamHeard

We like 1/16th. Runs like $60 per robot and you get a LOT left over for other parts. Mcmaster btw.

How do you feel about plywood, yeah it is ugly but it is cheap. How effective do you feel it would be? I know that 1114's Kitbot on Steroids uses 3/4" plywood for their electronics mount.

[Ninja_Bait]

Originally Posted by Andrew Schreiber

How do you feel about plywood, yeah it is ugly but it is cheap. How effective do you feel it would be? I know that 1114's Kitbot on Steroids uses 3/4" plywood for their electronics mount.

If you just put some paint on your plywood than it looks almost beautiful. It's a good material for stiffness and weight, especially at 1/2" and 1/4", and most teams that build field elements have some leftovers for things like electronics. You do have to worry about warping, though.

[JamesCH95]

Originally Posted by Chris is me

Also important to this design - rivets are better in shear than bolts.

Care to elaborate on that? For example, I'd find it very hard to believe that a 1/4" pop rivet (steel or aluminum) is better in shear than the shank on a graded 1/4-20 bolt.

A properly designed and setup bolted joint can sustain more shear loading than the bolts themselves alone. The friction between the two parts, as generated by the clamping load of the threaded fastener, carries a substantial amount of load in addition to the bolts. Can the same be said for rivets?

Originally Posted by Andrew Schreiber

How do you feel about plywood, yeah it is ugly but it is cheap. How effective do you feel it would be? I know that 1114's Kitbot on Steroids uses 3/4" plywood for their electronics mount.

Team 95 likes to use 1/2" or 3/8" high quality birch plywood. It is plenty strong enough and is lighter and more visually appealing that 3/4" construction grade plywood.