Standard vs. Custom Frame

[=Martin=Taylor=]

Aside from the wheels, I have a lot of respect for the kit-frame. It is strong, relatively light, and easy to build.

The downside is quite simple. Everyone uses it.

If you want to get an advantage over other kitbots you are going to have to modify it.

This is what my team did last year and it was a huge mistake. We tried to use 25 chain, smaller wheels, custom transmissions, and a modified front-end for collecting balls. Mounting these parts on a frame that was not designed for them proved to be a disaster. In order to climb the ramp we had to implement a diabolical series of chain tensioners, as a result our chains repeatedly came off. The modifications also weakened the structure and it slowly bent over time.

As the name implies, the kit-bot is a kit and I would recommend following the instructions If you want to do something different, don't try and transform the kit-frame into something it isn't.

[Tom Bottiglieri]

Here are some things you may find useful if you decide to pursue building your own frame.

http://www.chiefdelphi.com/media/papers/1705 - Nice paper on different types of drive train setups
http://www.chiefdelphi.com/media/papers/1682 - Copioli and Patton. Cant go wrong.
http://www.chiefdelphi.com/media/papers/1522 - CAD Help
http://www.chiefdelphi.com/media/papers/1443 - Drive train basics

Keep in mind building a reliable and effective chassis is more than just welding some aluminum tubing together and slapping some motors on. Your chassis is a system that relies on each and every part put into it, and the physics behind them. The kit frame is a well engineered solution, but there are some inherent set backs you will see by using it. Its up to you as a team to decide what is important to you and whats not. Your first custom designed chassis may not be the best thing out there, but you'll learn something by going through the paces.

As the 2007 season is fast approaching, I would not recommend going belly up into a new drive train design. Either stick with the kit frame for another year, or find a team in your area (or online) who will be willing to mentor you through this stage of moving from an inexperienced rookie team to an intermediate team who can come up with their own innovations.

PS - Theres a lot of white papers for different gearboxes and code ideas, but not a lot for fr ames? Whats up with that?

[clean399]

We usually go custom frame except for two years age on the triple play game we added webs in on the kit frame made it much stronger but only experienced welders should weld aluminum because it is hard we learned that the hard way. Every since then we build custom and rivet much lighter and stronger than welds.

[Gdeaver]

We have used the Kit frame with good results. WE start with the kit frame and build it up with 1" 6061 aluminum angle assembled with Steel pop rivets with back up washers. Our robot played defense this year and took some serious hits. Frame has some dings but is fine. The key is the box we build off the frame has allot of reinforcement. We try to make ever piece off metal added to the frame also structural. The electronics board can be an excellent structural element.The KOP frame and drive train was meant to ensure low resource teams do not fail and can be competitive. Look at the resources your team has and make the Kop or custom choice. Our team has about 600$ to build the robot and basic hand tools. Of course we are going to use the KOP stuff. We are very resource constrained. The only resources in abundance are enthusiasm and brain power.

[Billfred]

I'm writing this from the perspective of a (tor)mentor of two different teams over the ages, both Kitbot users and one-event teams. If your situation is different, your conclusions may well be different.

The teams I've worked with only have one shot at the game--there's no second regional, Championship, or off-season event. Now, you can argue (and I'll agree with you fully) that the season was a success if the kids were inspired and/or learned something, but it still doesn't feel good to go to lunch on Saturday not seeing your team number in the bracket. It didn't feel good as a student, it still doesn't feel good today.

Since we only have this one chance, I'm hesitant to bring onto the field a crucial part of the robot that hasn't been tested or proven--if it doesn't work, there's little chance of fixing it. Other factors tend to limit our own off-season prototyping, so I'm forced to rely on the experiences and thoughts of other folks who have done so. To me, the kit frame has been proven in competition as much as any robot part to date--hundreds, if not thousands, of robots have used it over the past two seasons, and I have yet to see one become so damaged on the field that it couldn't finish a match.

There's also the factor that the frame is, for all intents and purposes, a freebie. Like many one-event teams, the budget is pretty small. I could use this amount of money on parts for a ball pickup mechanism or towards a pair of AndyMark shifters, or I could use it on frame materials. To me, that's a no-brainer--I'll use the kit frame.

Now, there may well be a situation where I wouldn't use the kit frame. I know for a fact that it's rather hard (but not impossible) to do a kiwi drive with the kit frame, plus a few more items. Standard four-wheel omni drive would be rather cumbersome with it, and there are other configurations (6WD with the center wheel driven off the gearbox comes to mind) where the frame is more impractical. But until there's a game where the benefits of rolling our own frame outweigh the costs (both real and opportunity), you'll probably see me advocating the kit frame.

[rees2001]

We will be doing both this year.

Our veteran team will, as always, have a custom al. tube frame. We have been trying out a 3/4" square (1/8 wall) frame this fall and believe it will work for competition. We have used 1" square for the past 5 years and have never had a problem. We have a couple robot awards over that time also.


Our rookie team will be using the kit frame & welding the joints after we are happy with the design. This should help them with the flexability in design they need and still get some experience welding. Kiss. The rookies think that if they keep it simple they should be weeks ahead of the vets. More time for programming, more time for practice & problem solving.

As far as the number of competitions the robots will go to, the Vets will go to FLR & Championship & the rookies get FLR & may go to Championship if they qualify through winning the regional. Both will attend the ruckus in the fall but we get lots of tim to modify & fix before then. We probably will build a new machine just for that competition.

[Gary Dillard]

I anticipate using the kit frame next year with our young team, but we'll see. We are engineering resource limited (although we have a "Tytus" which makes up for it) so we'll use every available asset we can.

Here's another process that I have applied to components in general - treat the kit chassis as the prototype chassis, and test out your prototype mechanisms on it. As resources become available to design & fabricate the actual "production" components (including the chassis), replace the prototype component with the production component. If any production component doesn't get completed, you have the prototype to compete with.

[Greg Perkins]

In 2005 (that time I was mentoring team 134) team 134 decided to use the kitbot frame, rather than replicating our 2004 chassis (which was sweet).

What did we gain?
- A fully drivable base within the first week, to evaluate and for testing.
- A solid base for the rest of our super structure.
- Cheap Cheap Cheap.

Now albeit the results for the year were not spectacular, the robot base and frame did what it needed to, with no problems. And after the 05' season, we compared the results from 04' to 05' and we had came to the conclusion that neither one was any superior than the other.

Sanddrag - For me it's not even a question. We have been doing 1/8" wall thickness welded aluminum box tubing frames for the past three years. Why? Because it is stronger, lighter, and more elegant, and will not fall apart over time like a bolted together frame. We do things with custom frames that are not possible or practical with the kit frame.

As far as I know, a robot chassis is not judged on "sex appeal", and I'm sure the kitbot frame is comparable in weight to your frame. Please elaborate on why its not possible or practical to do "things" with a kitbot frame? You seem to always know everything, and I'd like to be enlightend.

[Cory]

Originally Posted by Greg Perkins

As far as I know, a robot chassis is not judged on "sex appeal", and I'm sure the kitbot frame is comparable in weight to your frame. Please elaborate on why its not possible or practical to do "things" with a kitbot frame? You seem to always know everything, and I'd like to be enlightend.

I've got no ideaw what Dave thinks the kitbot's shortcomings are, but here are mine-

No easy/good way to directly output to the center wheel in a 6wd format

No way to tension chains by sliding the wheels

No easy way to use live axles

No easy/good way to run your wheels outboard of the frame.

That list isn't meant to be a complaint. The kitbot is great for a number of teams, and anything that keeps teams from showing up to a regional with a robot that doesn't drive is great in my book. It's just not very optimal when you move on to more advanced designs.

[Billfred]

Originally Posted by Cory

I've got no ideaw what Dave thinks the kitbot's shortcomings are, but here are mine-

No easy/good way to directly output to the center wheel in a 6wd format

No way to tension chains by sliding the wheels

No easy way to use live axles

No easy/good way to run your wheels outboard of the frame.

That list isn't meant to be a complaint. The kitbot is great for a number of teams, and anything that keeps teams from showing up to a regional with a robot that doesn't drive is great in my book. It's just not very optimal when you move on to more advanced designs.

I'll concede all the points except live axles--I remember 1293 switching Ockham (which was originally kit frame and dead axles) to a live-axle setup in a leisurely-paced Saturday during the off-season. They used the bearings and blocks (and wheels, for that matter) from 2004.

[Cory]

Originally Posted by Billfred

I'll concede all the points except live axles--I remember 1293 switching Ockham (which was originally kit frame and dead axles) to a live-axle setup in a leisurely-paced Saturday during the off-season. They used the bearings and blocks (and wheels, for that matter) from 2004.

I was refering to not being able to just bore the frame out for a bearing. You could mount your own pillowblocks for sure.

[Dick Linn]

For several years, we've used a "custom" frame made from 1" x 1" x 1/8" square aluminum tube. We just cut, drill and bolt it together with quality bolts and nylock nuts or nuts and lockwashers. Nothing special, but it has never failed us. We've learned to do this because we have a low budget and nearly zero access to machining and welding facilities. Besides, it is really inexpensive and durable.

[JamesBrown]

Originally Posted by Cory

I've got no ideaw what Dave thinks the kitbot's shortcomings are, but here are mine-

No easy/good way to directly output to the center wheel in a 6wd format

No way to tension chains by sliding the wheels

No easy way to use live axles

No easy/good way to run your wheels outboard of the frame.

That list isn't meant to be a complaint. The kitbot is great for a number of teams, and anything that keeps teams from showing up to a regional with a robot that doesn't drive is great in my book. It's just not very optimal when you move on to more advanced designs.

http://joemenassa.com/Images/ROBOTIC.../IMG_3865.html

That is 121's chassis, I believe it was live axel, it was definitely 6 wheel drive, and they tensioned the chain with out using sliding wheels. This drive system proved to work out very well for them with regional wins both years that they used the kit frame. 121 certainly used it for more than just showing up with a driving robot. I would say that their designs were certainly effective. The kit bot doesn't seem to limit what you can do.

[dbell]

We have used the kitbot frame with different wheels for the past 2 years.

Besides, it is really inexpensive and durable.

That is mainly why we have used it.
In 2006 we won our regional, and had a good bot (i think). However were not able to collect balls as well as some teams with a different frame.

The kit bot doesn't seem to limit what you can do.

It can limit your robot's ability and quality, but it doesn't require any designing, is easy to build and is is strong.
Although a custom frame is more versatile it can be hard to design and more complicated to build.

[Cory]

Originally Posted by JamesBrown

http://joemenassa.com/Images/ROBOTIC.../IMG_3865.html

That is 121's chassis, I believe it was live axel, it was definitely 6 wheel drive, and they tensioned the chain with out using sliding wheels. This drive system proved to work out very well for them with regional wins both years that they used the kit frame. 121 certainly used it for more than just showing up with a driving robot. I would say that their designs were certainly effective. The kit bot doesn't seem to limit what you can do.

I never said you couldn't make a good robot using the kit frame. Just that it's my personal opinion that I wouldn't if I had the resources to do otherwise.