pic: 6CIM WCD

[Chris is me]

Originally Posted by DampRobot

Have you considered how your corner gussets will stand up with significant torsional loads? Or are you using a bellypan? Also, how will you make sure that the two sides of the drives are parallel? Rivets holes usually have enough play in them that locating of them doesn't work super well. Are rivets the only things holding the frame together, or is the tubing welded too?

Rivets and gussets are definitely both rigid and adequately strong for this application. I don't understand where you're getting rivets with enough play that you can't hold a frame together with them.

We used overly thick 1/8" gussets and a 1/16" solid belly pan this year instead of welding. Chassis was just as rigid, really. No noticeable performance or strength difference at all. Welding is not mandatory for this kind of drive. And there is definitely no need to do *both* permanently.



Here's a picture of our setup. The thickness of the gusset and the number of rivets used were both excessive, but rivets are almost "free" in terms of weight.

[T^2]

What hasn't been mentioned yet is that belly pans are almost critical for resisting shear -- never mind torsion. My bosses at work call shear the forgotten force, and for good reason; it's more difficult to simulate than simple point/line loads or torsional loads. Something as thin as .025" sheet aluminum, even with additional lightening holes, will make your whole frame much stiffer when it experiences shear forces.

[IndySam]

Originally Posted by Chris is me

Rivets and gussets are definitely both rigid and adequately strong for this application. I don't understand where you're getting rivets with enough play that you can't hold a frame together with them.

We used overly thick 1/8" gussets and a 1/16" solid belly pan this year instead of welding. Chassis was just as rigid, really. No noticeable performance or strength difference at all. Welding is not mandatory for this kind of drive. And there is definitely no need to do *both* permanently.

Here's a picture of our setup. The thickness of the gusset and the number of rivets used were both excessive, but rivets are almost "free" in terms of weight.

Add a good epoxy like Locktite Hysol and those riveted gussets can be just as strong as a welded joint but still removable with a drill and some heat.

[AdamHeard]

Our 2011 and 2012 robots were entirely riveted, no welding of the frames. Our 2011 WCD was not noticably different from the others in terms of strength or rigidity.

I hate anecdotes, but I'll be a hypocrite; Rivets hold airplanes together.

Also, the bellypan doesn't have to be exotic like 233/254 does. We made two of those and while they are cool, the resource cost is so high. We've run both garolite (G-10/FR4) and a high quality 6mm plywood with great results.

[DampRobot]

Originally Posted by Chris is me

Rivets and gussets are definitely both rigid and adequately strong for this application. I don't understand where you're getting rivets with enough play that you can't hold a frame together with them.

We used overly thick 1/8" gussets and a 1/16" solid belly pan this year instead of welding. Chassis was just as rigid, really. No noticeable performance or strength difference at all. Welding is not mandatory for this kind of drive. And there is definitely no need to do *both* permanently.

Here's a picture of our setup. The thickness of the gusset and the number of rivets used were both excessive, but rivets are almost "free" in terms of weight.

I was less thinking of rigidity after the rivets are installed, and more before. When a rivet is first placed in a hole (but not installed) the two pieces being joined together can still move in respect to each other a small amount. 3/16" nominal rivets are designed to go into #10 (.194") holes. While the OD of the rivet is probably larger than .1875" exactly, there is still some play between the rivet and the hole when it hasn't been crushed yet.

Rivets are rigid enough to hold drivetrains together, no problem, just as you said. We riveted (and didn't weld) parts of our drivetrain together this year and the year before. After the rivets were installed, the drive was quite rigid. However, I definitely noticed a significant amount of play before the rivets were installed. I do wish I had taken more care to make sure the drive was square, as rivets aren't perfect for locating frame members together. A bellypan certainly would have helped with getting everything square before the rivets were installed.

Riveting with a bellypan is probably perfectly square, strong and rigid. But, if the OP has TIG and MIG welders in house, why not learn to use them in the offseason?

Just like I said before, it's perfectly fine to completely disregard my (or anyone else's) advice on CD. Personal experience and experimenting in the offseason should always trump what someone says on this forum.

[AdamHeard]

Originally Posted by DampRobot

Rivets are rigid enough to hold drivetrains together, no problem, just as you said. We riveted (and didn't weld) parts of our drivetrain together this year and the year before. After the rivets were installed, the drive was quite rigid. However, I definitely noticed a significant amount of play before the rivets were installed. I do wish I had taken more care to make sure the drive was square, as rivets aren't perfect for locating frame members together. A bellypan certainly would have helped with getting everything square before the rivets were installed.

Some of our riveted assemblies are sort of self squaring (nice bellypan, etc...) but the ones that aren't we roughly jig together, as if it were a weldament.

Not saying either method is a better fit universally for all teams, just adding more data to the discussion.

[Gregor]

Originally Posted by DampRobot

I was less thinking of rigidity after the rivets are installed, and more before. When a rivet is first placed in a hole (but not installed) the two pieces being joined together can still move in respect to each other a small amount. 3/16" nominal rivets are designed to go into #10 (.194") holes. While the OD of the rivet is probably larger than .1875" exactly, there is still some play between the rivet and the hole when it hasn't been crushed yet.

Check out Cleco fasteners. They work as temporary fasteners to hold things together. My team used them when we got our sheet metal back to make sure everything was square and all the holes line up, before we riveted. They need a special tool to install and remove, but they take no more than a second.

They're known as "hole-grip clamps" on McMaster-Carr

McMaster-Carr P/N:

Tool- 5099A27
Cleco (3/16)- 5099A33

[Akash Rastogi]

Originally Posted by DampRobot

I was less thinking of rigidity after the rivets are installed, and more before. When a rivet is first placed in a hole (but not installed) the two pieces being joined together can still move in respect to each other a small amount. 3/16" nominal rivets are designed to go into #10 (.194") holes. While the OD of the rivet is probably larger than .1875" exactly, there is still some play between the rivet and the hole when it hasn't been crushed yet.

I use Cleco fasteners and Cleco clamps and haven't had any issues. The only time something was loose was if the rivet hole itself was marked wrong or sized incorrectly from the laser cutter.

http://www.aircraftspruce.com/catalo...heetholder.php

[Sh1ine]

Originally Posted by DampRobot

I was less thinking of rigidity after the rivets are installed, and more before. When a rivet is first placed in a hole (but not installed) the two pieces being joined together can still move in respect to each other a small amount. 3/16" nominal rivets are designed to go into #10 (.194") holes. While the OD of the rivet is probably larger than .1875" exactly, there is still some play between the rivet and the hole when it hasn't been crushed yet.

Rivets are rigid enough to hold drivetrains together, no problem, just as you said. We riveted (and didn't weld) parts of our drivetrain together this year and the year before. After the rivets were installed, the drive was quite rigid. However, I definitely noticed a significant amount of play before the rivets were installed. I do wish I had taken more care to make sure the drive was square, as rivets aren't perfect for locating frame members together. A bellypan certainly would have helped with getting everything square before the rivets were installed.

Riveting with a bellypan is probably perfectly square, strong and rigid. But, if the OP has TIG and MIG welders in house, why not learn to use them in the offseason?

Just like I said before, it's perfectly fine to completely disregard my (or anyone else's) advice on CD. Personal experience and experimenting in the offseason should always trump what someone says on this forum.

I agree, personal experience does trump the forum, I do just want to expand on what Chris said a little bit. When we rivet our chassis together all of the parts including our rivet holes are machined on our HAAS Mill. We use a #11 drill (.191) for a slightly tighter fit. We rivet the gusset plates and chassis rails together. We then use clamps and a tape measure and compare the length from corner to corner in a X pattern and adjust the clamps as necessary to square the chassis (similar to woodworking). At that point we attach the belly pan (which is not pre-drilled.) When using rivets for structural members use High Strength Blind Rivets such as McMaster part number 98778A501 they have a much high shear strength than standard rivets.

[AdamHeard]

Originally Posted by Sh1ine

I agree, personal experience does trump the forum, I do just want to expand on what Chris said a little bit. When we rivet our chassis together all of the parts including our rivet holes are machined on our HAAS Mill. We use a #11 drill (.191) for a slightly tighter fit. We rivet the gusset plates and chassis rails together. We then use clamps and a tape measure and compare the length from corner to corner in a X pattern and adjust the clamps as necessary to square the chassis (similar to woodworking). At that point we attach the belly pan (which is not pre-drilled.) When using rivets for structural members use High Strength Blind Rivets such as McMaster part number 98778A501 they have a much high shear strength than standard rivets.

We used to use the high strength rivets, but switched to regular a few years ago. The high strength isn't worth the extra $$$.