pic: sheet metal 6WD

[kajeevan]

loading photo ...

[Chris is me]

Looks familiar.

Any reason not to make the bottom a full belly pan for electronics, etc?

[Andrew Schreiber]

Originally Posted by Chris is me

Looks familiar.

Any reason not to make the bottom a full belly pan for electronics, etc?

The op may be looking at doing something different and lighter to mount their electronics (http://www.chiefdelphi.com/media/photos/27670) It would be possible to use cables under tension to mount your electronics to and use your frame (which should be pretty rigid in most cases) to ensure tension. Not only that but there is no fear of shorting out if you use a plastic coated cable.

Just saying, there are alternate ways of mounting electronics that many teams haven't looked into, all of these have the benefits and their drawbacks which must be considered.

[kajeevan]

To answer a few questions,

I went with 1/8in Al trying to avoid having to put plates around the axles for strength and having to deal with smaller pieces. Also I was hoping to have the side plates tapped so I might not need nuts and just adjust the clutch on the drill to not strip the treads when inserting bolts.

The chain is tensioned with a bent C-channel with extra flanges for strength that hug the axle and is pulled by one 5/16'' bolt. The chain can be tensioned up to 1''. If you look closely enough you can see it.

I don't believe it's possible to have the AM SS in line with each other.
I am using pneumatic shifting.
I positioned them sideways to have easy access to the encoder and shifter.
Speeds are 5 and 18 feet per second.

There is no base plate yet but will be once the function is decided and its worked around it. But the front and back plates connect the entire base together and act like a small base plate at the triangles preventing racking.

Sorry for the late response been busy for a while.

[Rob Stehlik]

Overall, this is a solid looking design. I agree with previous recommendations that you don't cut away flanges for the gearboxes. It looks like you may have room to bend the flange towards the wheels. Also, depending on the manipulator required, you'll likely want an opening at the front of the frame.

Originally Posted by kajeevan

To answer a few questions,

I went with 1/8in Al trying to avoid having to put plates around the axles for strength and having to deal with smaller pieces. Also I was hoping to have the side plates tapped so I might not need nuts and just adjust the clutch on the drill to not strip the treads when inserting bolts.

I agree that using thicker material can be simpler than reinforcing thinner material. I'm not sure you should put threads into .125 aluminum though. It'll strip really easily. You should look into PEM nuts. They press into holes in your sheet metal and provide much stronger steel threads. We use them all the time. The correct way to install them is with a press, but we find just cranking them tight with a cap screw will seat the teeth into the aluminum just fine.

The chain is tensioned with a bent C-channel with extra flanges for strength that hug the axle and is pulled by one 5/16'' bolt. The chain can be tensioned up to 1''. If you look closely enough you can see it.

I like this design a lot! It looks like a great way to tension the chain. My only suggestion would be to put flanges at the front of the C-channel where the pull bolt goes through. Otherwise this area would bend quite easily. Also, why a 5/16" bolt? A 1/4" or even #10 bolt would be fine.

There is no base plate yet but will be once the function is decided and its worked around it. But the front and back plates connect the entire base together and act like a small base plate at the triangles preventing racking.

Triangles are good

Rob

[MWB]

Is there any way to rotate the shifters so that the motors line up, for ascetics and very insignificant COG changes?

[apalrd]

1. I would recommend a center divider on one side of the motors. It will add strength and also a place to mount an electronics tray (e.g. from the back to the middle with the front open, or something like that)

2. Electronics tray could be perforated aluminum. Just cut it to size, rivet it in, and zip tie the electronics. Nice and easy.

3. I like the chain tensioning method. Super simple. If you want, you could put a 1" tall by 1/4" thick block with a hole for the axle, then tap the end for a 10-24 (or 10-32 if you want) and just tighten the screw to tension it, then tighten the axle bolts to hold everything secure.

4. Are you using servos for the SS's? If you are using pneumatics elsewhere on the robot (or even if you aren't), pneumatics will shift easier then the servos. I do not know how much better they are, but they provide a lot more force to shift then the servo does. We always shift with pneumatics when using AM shifters.

5. Rivets. If you are waterjetting or otherwise CNC'ing the sheet metal plates, just add a few holes per connection and pop rivet it. Easier to assembly, and not much more work in CAD (this is especially true with a pneumatic riveter, those are great)

6. Have you done any math on the speed and gear ratios?

7. .125" seems really really thick. We use something around .050 in our chassis, with a plate around the axles (a little circle with an axle hole and 4 rivet holes, around 1.5" in diameter), or the above mentioned tensioning block with some reinforcement.

[548swimmer]

.125 sheet is way to thick, especially with flanges. You can easily go down to .09 (a fairly standard size) wihout too many design changes. Any thinner (.05) and I'd make larger flanges just to be on the safe side.

Is there any reason you're lightening with circles instead of triangles?

Is there any reason you rendered it as an illustration?

[Akash Rastogi]

Originally Posted by 548swimmer

Is there any reason you're lightening with circles instead of triangles?

Depending on what manufacturing process they have available, circles are great to use.

Check out pictures of 228's recent robots.

[548swimmer]

Originally Posted by Akash Rastogi

Depending on what manufacturing process they have available, circles are great to use.

Check out pictures of 228's recent robots.

True, I tend to forget about punches since we don't have access to one.

What about flipping the inner plate around so the flange is on the wheel side. It looks like the flange is small enough such that this wouldn't limit access too drastically, and having a flange along the entire length will be muh stronger.

[Akash Rastogi]

If you have access to a punch, kajeevan, I would recommend checking out Art Dutra's white papers here on CD. He posted his CAD files and he has some awesome designs in there.

[artdutra04]

Originally Posted by Akash Rastogi

If you have access to a punch, kajeevan, I would recommend checking out Art Dutra's white papers here on CD. He posted his CAD files and he has some awesome designs in there.

Thanks!

Originally Posted by 548swimmer

True, I tend to forget about punches since we don't have access to one.

What about flipping the inner plate around so the flange is on the wheel side. It looks like the flange is small enough such that this wouldn't limit access too drastically, and having a flange along the entire length will be muh stronger.

I'm sure sure of the rational behind their choice of sheet metal direction flanges, but since the flange profiles look identical to the ones on our 4WD/6WD sheet metal designs, here's the rationality behind ours. The black flanges are our chosen sheet metal flange profile.



By putting the flanges where they are to avoid geometry conflicts, the necessary space between two chassis rails is kept to a minimum. These aren't the most optimal flange configurations for chassis strength, but they work good enough for our applications.

[548swimmer]

Originally Posted by artdutra04

Thanks!

I'm sure sure of the rational behind their choice of sheet metal direction flanges, but since the flange profiles look identical to the ones on our 4WD/6WD sheet metal designs, here's the rationality behind ours. The black flanges are our chosen sheet metal flange profile.

By putting the flanges where they are to avoid geometry conflicts, the necessary space between two chassis rails is kept to a minimum. These aren't the most optimal flange configurations for chassis strength, but they work good enough for our applications.

Fair enough. I usually think of a flange's strength benefits instead of its mounting benefits. Although, with roughly 5 inches of pool noodle and 1.5 inches of plywood between colliding robots, the bottom flange may not even be necessary.

[Chris is me]

delete please.

[Chris is me]

Originally Posted by 548swimmer

True, I tend to forget about punches since we don't have access to one.

What about flipping the inner plate around so the flange is on the wheel side. It looks like the flange is small enough such that this wouldn't limit access too drastically, and having a flange along the entire length will be muh stronger.

How much is "much"?