Sheet metal vs Tubing Chassis

Our team is entering our second year in the 2016 season and we’re trying to do plenty of training and offseason work to be very competitive in our competitions. Last year we went to Worlds and I had the chance to look out some robots and there was a variety of robots that used a sheet metal chassis and some that used a 2x1 aluminum tube style frame.

Thus begs the question: tube or sheet frame? We recently got a sheet metal/fab sponsor so tooling won’t be an issue. We also are planning on getting a decently sized CNC router so making standard gussets and custom sheet parts won’t be an issue, but we definitely don’t plan on making a chassis on it. My current 2x1 aluminum tube based project (Hex shape just for kicks):
Larger view

The best drivetrain is the the one that fits your team’s capabilities.

Each drivetrain has pros and cons, so it’s best to choose the one that your team is most capable of producing. This should take into account design, manufacturing, assembly, repair, and control.

I’d look into decision matrices, and use those to help you decide which is best for you and your team.

Edit: Here’s a sample decision matrix for a drivetrains.

Having a sheet metal sponsor is awesome but the hard part is having the skill and knowledge to utilize them properly.

If there are people on your team with the knowledge of sheet metal take advantage of it. If not reach out to teams who do or hold off and experiment and prototype and get good at it then bring it into your robot design.

My basic understanding of materials is that if you look at a lot of top teams that consistently put out solid robots is that they consistently use a set group of materials to make their robot. Instead of asking which is “better” considering the metal sponsor take this year as a learning expedition and contact as many teams as you can that fully utilize sheet metal and just learn.

How much can they commit?
Have you thought about using a hybrid system of 2x1 and flat panel parts? That way your sponsor doesn’t have to worry about bending the parts and there will be a reduced learning curve for the team and a possible faster turn around time.

As all have said above, it’s a matter of what works best for you. We’ve never used tubing for the chassis, and only used sheet metal as part of a kit chassis. Our second and third robots were made of extrusion (6063, I believe), a combination of c-channel and angle with a bit of bar and plate here and there.

Don’t let your new sponsor’s first custom part be your chassis! Design some smaller parts like custom mounting brackets for them to fabricate first, so you can verify that the flanges and holes end up where you expected them.

Off topic, but we should really get our teams together sometime soon, considering that you folks live next door to us now :slight_smile:
We’re also doing training and offseason work and I bet our students would benefit by checking out each other’s work.

Something to consider when working with an outside company making parts is determining to what quantity of parts and how long they can support you. Some companies can support as many parts as a team needs and for however long into the season you need them which is good to know if you might need replacements or redesign something. Other companies can only support teams once or in small batches of parts so some teams have multiple shops who help them out but to the casual observer it looks like all the fancy parts came from one shop.

Good communication with your sponsors can lead to a long, successful relationship.

Once you know what is out there and what you have in your control (in house such as machines, knowledge, and finances for COTS parts) evaluate where those resources would be best used. Most teams use their sponsors to develop custom drivebases while others utilize their sponsors for manipulators and upper assemblies.

Good luck!

Make sure your new sheet metal vendor can supply you the parts WHEN you need them. One of the local teams showed up at a tournament with their competition bot in the bag and only half built. Their sheet metal vendor gave them the parts the day before bag and tag.

I would do a tube frame and save the sheet metal resource for superstructures, personally. Making a WCD nowadays takes very little time, and for us at least it makes more sense to go with that rather than use our sponsor’s time making the chassis for us.
However, having flanged sheet metal for superstructures is very lightweight and nice IMO.

We’re not too sure at the moment as we just obtained the sponsor. I hear the standard turnaround time seems to be a week or so, but I have yet to find out what ours will be.

My personal factors in the chassis are
•$@#Learning Curve
• Ease of fabrication
• Strength
• Weight

For right now, it’s fairly easy for us to put build tube-based structures and I want us to learn more, but the amount of knowledge to pull off an entire sheet chassis might be too high. Thanks for the input guys.

Most important thing when it come to using sheet metal effectively is understanding exactly what your sponsors capabilities are. Once you understand that and understand what the turn around time is, you can decide what to do with sheet metal.

But once you get good at it and get the logistics worked out for a fast turn around, it will open up a lot of doors for you. If possible, you should try to get them to make a few parts for you before the season starts so you can get an idea of the turn around time and the quality of the parts.

Be sure you understand the risks. You may want to start with non-critical parts that you can design early in the build season and that you can replace with parts that your team fabricates without the help of your sponsor. That “week or so” can easily get pushed out to a month or so when your sponsor gets a paying gig. This is assuming that they are donating the time and material to your team. I have situations where the delivery time for my prototype parts for work (that we pay to get made) be pushed out by our Purchasing Manager due to the capacity being needed for production parts

Our team used sheet-metal parts last year on both our chassis and multiple mechanisms, we learnt quite a few things… Mainly that by adding flanges to plates, you can greatly enhance the strength of parts even if the flange isn’t long. The small things make a difference. We had a great turnaround time of 3-4 days so that was awesome. One thing to note is that a relationship with a fabrication sponsor can be greatly improved if you have strong communication with them, in other words, be very organized and straight forward and respect that they are providing this service free of charge and that you aren’t their top priority. P.S. (Using the same software as your Fab Sponsor is also great because they can easily make changes to the part if necessary, and again helps in communication)

We have designed a WCD Chain-In Tube chassis this off-season, so we are wanting to see how that comes out. It does provide quite a lot of advantages, but with any system there are dis-advantages. We really like designing with “tubes”, either it be 1" x 1" or 2" x 1". Interfacing your superstructure with your chassis can be difficult for some teams, but if you use a similar construction and design method, it can be somewhat simplified.

Good Luck! And congrats with going to Worlds last season, it was our first time too!!

On top of this. Once the build season starts figure out how you want your robot to function and how you want to implement those functions. I know from personal experience and trudging through a glorious 12 seasons so far that we’ve used everything from the KOP, Tubing, sheet metal, etc. It all depends on our game plan for the upcoming/current build season and what we would like to accomplish during the comp.

This guy really doesn’t like learning curves!