Attaching Things on WCD

[DampRobot]

Originally Posted by Thad House

We usually weld some plates to the bottom of whatever our superstructure is, and then those plates can then bolt to the top of the siderails. This makes it really easy to remove the structure, and there are plenty of ways you can mount to still be really strong.

This is how we did it. Basically, you end up with a superstructure that can be completely removed from the frame of the robot without any drilling, etc. I've seen 254 completely remove their superstructure for upgrades thanks to this frame design.

Edit: Here's a view of one of our superstructure attachment points from our 2014 comp bot.

[Dunngeon]

Generally, the superstructure is what things get attached to, it can be pemanently attached via welding, temporarily attached through rivets (use steel), or Bolted on with nuts and bolts. As posted above, the superstructure can even be made removable for easy changes to the drive base.

One small suggestion, have you thought about 3Cim gearboxes? They are an easy way to increase the torque available on your robot and make it generally faster.

Awesome to see more Oregon Teams on CD, good luck!

[Brandon_L]

We just gusseted our upper structure stuff right to the side of the rails with rivets. The rivets had low enough heads so they wouldn't contact the wheels. The other set of gussets were in a funky shape to avoid the bumper support, but overall it worked very well.

[JorgeReyes]

Originally Posted by Dunngeon

Generally, the superstructure is what things get attached to, it can be pemanently attached via welding, temporarily attached through rivets (use steel), or Bolted on with nuts and bolts. As posted above, the superstructure can even be made removable for easy changes to the drive base.

One small suggestion, have you thought about 3Cim gearboxes? They are an easy way to increase the torque available on your robot and make it generally faster.

Awesome to see more Oregon Teams on CD, good luck!

I've been considering 3 cim gearboxes but I am worried about the cost of getting them. If we find a way to set aside a bigger budget for our drivetrain then we might switch to 6 cims

Originally Posted by JorgeReyes

I've been considering 3 cim gearboxes but I am worried about the cost of getting them. If we find a way to set aside a bigger budget for our drivetrain then we might switch to 6 cims

If you don't know what you're doing, a 6 CIM drive could show little benefit, and sometimes even hinder your drivetrain. They're useful if you're purposefully planning on optimizing for their advantages, but otherwise I'd stick with 4 CIM drives. They're just as good, and won't give you problems if you don't plan for everything (source: used two 6 CIM transmissions on two different robots - transmissions were fine but didn't get much of an advantage from them because there wasn't much correct optimization).

[JorgeReyes]

Originally Posted by Andrew Lawrence

If you don't know what you're doing, a 6 CIM drive could show little benefit, and sometimes even hinder your drivetrain. They're useful if you're purposefully planning on optimizing for their advantages, but otherwise I'd stick with 4 CIM drives. They're just as good, and won't give you problems if you don't plan for everything (source: used two 6 CIM transmissions on two different robots - transmissions were fine but didn't get much of an advantage from them because there wasn't much correct optimization).

By this do you mean calculating the correct gear ratios to use?

[Chris is me]

Originally Posted by JorgeReyes

By this do you mean calculating the correct gear ratios to use?

There's a range of ratios where you're geared too fast to push continuously anyways but too slow to really get an acceleration benefit. It's around the 9-12 FPS range depending on who you ask. I would recommend experimenting with 4 vs 6 CIMS on your own in the off season to get a better grasp on how they help. 4 CIMS is perfectly adequate for a lot of robots; the jump from 4 to 6 CIMS is a lot less dramatic than the jump from 2 to 4.

If your budget is constraining your design I would probably stick with 4 unless you want a drive in the 5-9 FPS range (you'll be able to push for longer stretches of time before tripping a breaker), or you are going 13+ FPS at full weight (acceleration is noticeably better). Even in these ranges it's not mandatory to go with extra motors.

[Chris is me]

Here's one example of how we attach super structures to our base frame. In 2012 we did something similar to what DampRobot posted, and in 2013 our superstructure consisted of four 1/4" plates serving as a gearbox and arm mount. Not a great example for general purpose robot building.



The white superstructure frame was welded at the ends to 1x1 1/8" wall box tubing. The tubing had a 3/16 rivet hole pattern in it, as we try to do for all of our parts, so we drilled out 4 holes per side for #10 clearance. The tops were drilled out for tool clearance. The corresponding holes on the chassis were drilled out and 10-32 rivnuts were installed. Rivnuts are awesome as they let you bolt things together to material of any thickness without having to hold a nut anywhere. To install or remove the entire superstructure we just screw 8 bolts in or out.

There are a number of ways to attach things to the frame without welding them to another member. Flat gusset can do a lot if you pay attention to how these gussets are loaded. The VersaChassis 90 degree bent gusset is also a big help.

[JorgeReyes]

I think I might completely change my chassis design to something like this because I was also looking at the chassis from 1241 and it looks extremely light and really easy to attach anything.

[JorgeReyes]

Weren't there only 6 cims allowed? It looks like you have 8 in the picture

[z_beeblebrox]

Originally Posted by JorgeReyes

Weren't there only 6 cims allowed? It looks like you have 8 in the picture

Two of the pictured motors are miniCIMs.

[Dunngeon]

This is a picture of our chassis, it isn't a WCD, but it is simpler for us to manufacture requiring only 2x1 al tubing, steel pop rivets, and a standardized aluminum gusset.

On the sides, you can see the gusset plates and the bolts that supported the intake structure. Our biggest problem with the chassis was the lack of super structure, made mounting many things harder, so depending on the game next year we will be adding a superstructure to assist in mounting game components.
Those plates to mount the intake structure were later modified, because they became increasingly cockeyed as the bolts deformed the aluminum tubing wall. Our solution was to create a wider contact structure and use 8 pop rivets to distribute the load better.


Also note it was in fact a 6wd later in the season, just not in this picture

http://team955.com/gallery3/var/albu...G?m=1394932723

[Al Skierkiewicz]

Bumpers are always a nice addition. Just saying...

[JorgeReyes]

Initially I was thinking of going with a welded chassis design but after getting all this advice I think I am also going to go with a riveted design because it seems much easier to mount things or change things around

Originally Posted by JorgeReyes

Initially I was thinking of going with a welded chassis design but after getting all this advice I think I am also going to go with a riveted design because it seems much easier to mount things or change things around

A lot of teams do a mixture of both welding and gusseting, sometimes even both in the same place. Sometimes there are places where gusseting isn't the easiest to do - in which case don't be afraid to use welding.

tl;dr: If you have two ways of attachment, don't limit your design by only choosing one.