pic: Rastogi 8wd Iteration 1.2

[Andrew Remmers]

Originally Posted by Akash Rastogi

Ah thanks for the insight Andrew.

You might also like this. I tried to copy it from one of the pictures that was posted of your 2010 bot.

:O that looks strangely familiar! you did this in solid works right? (i need to find a copy of that...) I'm still using inventor and a little bit of Pro-E.

[Jamie Kalb]

Originally Posted by RMS11

Where here would you attempt to use PEM nuts. I was looking at them on mcmaster, and they look cool, but pressing all of them seems time consuming when you could just use rivets or a nut and bolt instead. In the long run it might save a bit of time though... Any other big advantages of them? thanks!

I'm not good at judging measurements from pictures, but it looks to me like the current flanges aren't big enough. But if the flanges bent off the main body of those enormous side plates were wider (or is that longer?), you could punch holes in them and press the PEM nuts in. As far as I know, many sheet metal shops can do this in-shop. Check out the 217/148 Sheet Metal video. It shows them pressing PEM nuts at about 5:05 in the video. Not time-consuming at all. Compare the ~1 second per insert to all the time you'd spend fumbling for a nut ... total. For a season.

Whenever possible, I like to add threads to a part (tapping or threaded insert) rather than using a nut. One less piece to worry about, one less piece to come loose, one less point you have to reach for assembly/maintenance. Plus installation and removal now only takes one hand!

But Andrew's 100% right about this:

Originally Posted by Joyride_67_1902

Being on 1902 I can say that when the flanges are facing outward it is significantly easier to run maintenance on the drive train. Considering that the space you are working with is already very small it is difficult to get to all the components even on the robot we have this year. I can only imagine what it would have been like if it were the other way around, having that "obstacle" in the way would have made some points of repair for us very difficult especially when we had a master link failure at Florida.

Having the flanges bent in rather than out definitely does make drivetrain maintenance harder. It's possible to make the plates modular enough to justify this, but you're probably better off just keeping them facing outwards.

[R.C.]

Nice Render,

Slightly curious what's the weight?

-RC

Looking good.

Also, I'll second (third?) the recommendation for using PEM nuts. We use them at my work on our sheet metal chassis, and they're wonderful to deal with. Out of 75 robots, we had one PEM nut pop loose, and the shop that pressed them fixed it for us in less than 6 hours. PEM nuts are the way to go.

How many parts in there are standardized? It's always easier for a sheet metal shop to punch out and break more similar parts than differing ones.

[Akash Rastogi]

Originally Posted by CraigHickman

Looking good.

Also, I'll second (third?) the recommendation for using PEM nuts. We use them at my work on our sheet metal chassis, and they're wonderful to deal with. Out of 75 robots, we had one PEM nut pop loose, and the shop that pressed them fixed it for us in less than 6 hours. PEM nuts are the way to go.

How many parts in there are standardized? It's always easier for a sheet metal shop to punch out and break more similar parts than differing ones.

I'll definitely check out PEM nuts.

There are only 3 different parts here. All sideplates at the same, all cross members are the same, and brackets in between plates are the same.

Originally Posted by Akash Rastogi

I'll definitely check out PEM nuts.

There are only 3 different parts here. All sideplates at the same, all cross members are the same, and brackets in between plates are the same.

Wonderful! Keep up the awesome work!

[AdamHeard]

Why not connect the two side assemblies along the bottom?

[Akash Rastogi]

Originally Posted by AdamHeard

Why not connect the two side assemblies along the bottom?

Can't see it, but there's one along the bottom on the other side. The near side is open because I was working on a 148/217 style cam kicker for fun.

[DonRotolo]

Originally Posted by Jamie Kalb

but you're probably better off just keeping them facing outwards.

I disagree. The sideplate will tend to be pushed inward by any contact from other robots or field elements. In such a case, your flange will tend to be in compression. Such a small flange will buckle. If the flange was on the inside, it would be in tension, a mode that is far stronger than the compression mode. Try it yourself with a piece of angle.

Second, you might consider putting flanges on some of those inside cutouts. Yes, it ends up a little heavier, but because the outer flange is not continuous you will suffer from low rigidity (and low resistance to bending) at certain points; use flanges to compensate.

Akash, when you're doing your analysis, be sure to model loading from another robot hitting you from the side at several locations.

[Akash Rastogi]

Originally Posted by Don Rotolo

Second, you might consider putting flanges on some of those inside cutouts. Yes, it ends up a little heavier, but because the outer flange is not continuous you will suffer from low rigidity (and low resistance to bending) at certain points; use flanges to compensate.

I was thinking about this for a while, but I am not familiar with capabilities of sheetmetal manufacturing.

Could you, or anyone else, elaborate on what types of places flanges can be made on a part like this? I wanted to add flanges on some of the inside pockets but wasn't sure if that was easily possible. Like I said, I'm looking to learn about this as much as possible.

Thanks.

[Jamie Kalb]

Originally Posted by Don Rotolo

I disagree. The sideplate will tend to be pushed inward by any contact from other robots or field elements. In such a case, your flange will tend to be in compression. Such a small flange will buckle. If the flange was on the inside, it would be in tension, a mode that is far stronger than the compression mode. Try it yourself with a piece of angle.

You're right; I didn't think about that. You definitely want flanges like that in tension.

And,

Originally Posted by Don Rotolo

Second, you might consider putting flanges on some of those inside cutouts. Yes, it ends up a little heavier, but because the outer flange is not continuous you will suffer from low rigidity (and low resistance to bending) at certain points; use flanges to compensate.

How would you bend a flange out from an inside cutout? Would you just use a really small (short) set of jaws on a brake, or is there another tool to do that?

Thanks!

[artdutra04]

Originally Posted by Jamie Kalb

How would you bend a flange out from an inside cutout? Would you just use a really small (short) set of jaws on a brake, or is there another tool to do that?

The same as they would with an outside bend; they just move the bending dies around and leave gaps where there is material that should not be bent.

This past year, 228 used a bunch of these inside bends on our GUSwerve modules to mount the lower bearing plate on. Here's a photo:

[Akash Rastogi]

Originally Posted by artdutra04

The same as they would with an outside bend; they just move the bending dies around and leave gaps where there is material that should not be bent.

This past year, 228 used a bunch of these inside bends on our GUSwerve modules to mount the lower bearing plate on. Here's a photo:

Excellent, I'll definitely be changing things around a lot then.

[Jamie Kalb]

Originally Posted by artdutra04

The same as they would with an outside bend; they just move the bending dies around and leave gaps where there is material that should not be bent.

Ohhhh! Gaps in the die! Duhhhh! Now I get it. Thanks. (the picture helped)

Originally Posted by Akash Rastogi

Could you, or anyone else, elaborate on what types of places flanges can be made on a part like this?

Hey, Akash, you can bend flanges from an inside cutout!

[sgreco]

Originally Posted by Don Rotolo

Second, you might consider putting flanges on some of those inside cutouts. Yes, it ends up a little heavier, but because the outer flange is not continuous you will suffer from low rigidity (and low resistance to bending) at certain points; use flanges to compensate.

I'm sort of in the process of leanring about the techniques of sheetmetal fabrication so I don't really know, but right now this is a fairly straightforward part to make, especially if you have a laser cutter. What I don't know is will adding those inner flanges add significantly to the fabrication time? I would imagine if in fact more strength was needed it would be easier and more robust to just add more cross supports between the inner and outer plate.