Standard vs. Custom Frame

[BanksKid]

i was just dyeing to say this....................................NYLOCK IS GOD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!

[Viper37]

Originally Posted by Cody C

The weight difference to our teams extruded frame was negligable, and the strength of the kitbot is anything that you would need for FIRST competition.

You must not get very far then.

2 years running we have used the kitbot frame. 2 years running the front and rear are badly smashed in.


Time to get our brand new TIG/CNC Aluminum frame from HP's machine shop!

Personally, even if it would be a resource stretch, I would rather my team go with a custom frame. Here's my reasoning.

Engineering experience: For a real world experience, you aren't going to be given a base chassis, drive system. You need to be able to design one. Adapting an old one is good, but it doesn't come up very often.

Plus, designing and building your own fram gives you a very real sense of the design phase. If you mis-measure, you pay the price by having a component not fit. By having heavier consequences for design failures, you learn to take more time on the design.

[/soapbox]

edit: also, as far as strength... custom is far superior. Just by hitting another bot at full speed from 5 deet away, we bent in their straight frame, and sent a gearbox flying. It made us feel very bad, and so we helped them fix it.

[Donut]

Originally Posted by Viper37

You must not get very far then.

2 years running we have used the kitbot frame. 2 years running the front and rear are badly smashed in.


Time to get our brand new TIG/CNC Aluminum frame from HP's machine shop!

2 years we've used the kit frame, and 2 years we've made the semi-finals at the Arizona Regional (one we won Industrial Design award as well).

Is it just the different strategies teams pursue that cause such a wide range of results with the kit frame? Some teams are reporting complete failures with them where they come apart frequently and make for a poor robot, while others report perfect durability and being extremely competitive. Is it the attachements, the driving strategy, or what?

If teams are looking for a good adjustable chain tensioner for the kit bot frame I'll try to get ours up, I looked but we don't have any good pictures of them off hand. It uses an idler sprocket that can be adjusted with a wrench.

There is a certain satisfaction in doing a custom frame I believe; I know our team would certainly like to try it. But when you absolutely don't have the possibility of doing it, the kit frame is certainly not a "well we're going to be mediocre at best" choice, and if done right there are probably times you'd still want to try it over the custom frame. If nothing else everyone has a nice practice/demo bot chassis to use.

[Gary Dillard]

Originally Posted by 114ManualLabor

Engineering experience: For a real world experience, you aren't going to be given a base chassis, drive system. You need to be able to design one. Adapting an old one is good, but it doesn't come up very often.

In my 25 years of engineering design experience (in 3 totally different fields), I've had HUNDREDS of times where I was required to design components to adapt to an existing platform. In fact, it's more likely that you will be required to modify an existing system or component, or add something to an existing system or component, and the desire is to change as little as possible on the existing system. Clean sheet designs are few and far between in the engineering world when compared to modifications.

What this means is that you need to evaluate the performance of the existing frame for its task. If you think it's going to bend locally, beef it up! Custom isn't stronger because it's custom, but because you put the stiffening in the right places. There's not much wasted weight in the kitbot chassis, so put an extra gusset or brace here and there - you probably need attachment points anyway. The great thing about the perforated angle and sheet is that you can assemble it, test it, modify it, all in the same night.

[Karthik]

Originally Posted by 114ManualLabor

also, as far as strength... custom is far superior.

Umm, okay.

We have to be careful about making all encompassing statements on these forums. It's one thing to say "My team chooses to use a custom a chassis, because we have enough resources to build something better than the kit chassis". It's another thing to say "custom is far superior". Yes there are custom frames that are better than the kit frame. By no means it the kit frame the ultimate solution. But, to imply that all custom frames are better than the kit frame is ludicrous and insulting. I've seen many teams design custom frames in lieu of the kit frame, and fail miserably because of it.

The decision on whether to use the kit frame or not depends on a variety of factors. If your team feels that you're losing part of the FIRST experience by going kit, that's a personal decision. When it comes to a sheer engineering decision, here's the guideline I offer to teams.

Step back and honestly evaluate your team's resources. Do this in terms of finances, experience, manpower & talent. This will help you answer the following questions.

1. Consider the custom frame you're considering building. Does it provide a large advantage over the kit frame? Consider strength, rigidity, ease of mechanism integration, and ease of repair.

2. With this frame, can you have your drivetrain completed in 2 weeks?

3. Will building this frame still leave you with enough resources to work on and complete the rest of the robot at a high quality? (Will you still be able to build as good of a mechanism as you want?)

If the answer to these three questions is Yes, then it sounds like you're ready to go custom. Otherwise, stick with the kit frame. The easiest way to make your robot perform better at competition is to have a well practiced driver. That means having the drivetrain done early. This is why I feel more teams should use the kit frame. The kit frame allows you to get your drivers practicing before week 2 even finishes! This is such a huge advantage. Time is such a valuable resource, it can't be wasted. Plus, by using the kit frame, you can allocate resources to your mechanism.

I'm frankly tired of a lot of the "kit bot snobbery" I hear from people in this program. I definitely agree that it's not for everyone. There are some teams who can whip out a wicked, strong welded aluminum tube frame in a couple of days. If you don't use it, this doesn't mean you need to come out and say that it's a horrible product, and that teams who use it are making a dumb decision. The kitbot is a great tool for all teams. For those low resource teams who need a kick start, and for those savvy teams who don't want to re-invent the wheel and would rather spend their time practicing and building an awesome mechanism.

[Scott358]

Based upon the original statement that resources are very limited, and assuming that you'll want spend those resources designing mechanisms to play the game, I would strongly suggest the kit frame. Having used the kit frame this past year, it works very well and stood up to 3 events for us without issue.

I'd suggest spending your limited resources on the drive train design (that will run in the kit frame) and the remainder of your robot.

Good luck with whatever you choose to use!!

[Gdeaver]

Karthik,
Thank you for your post. It's what I tried to point out earlier but, you said it better. The kit base alone is not enough to survive a physical game the 2006 comp turned into. The kit frame is a beginning. How it's added to and reinforced can be the difference between success and failure. In 2006 bumpers were introduced. Not all teams took advantage of them. If the bumpers are allowed again for 2007, I would encourage both kit and custom teams consider their use. The strength of the plywood bumper frame should not be ignored. In fact with the proper type of plywood the 2006 bumpers can be considered a structural element. Better yet a major structural element that is not part of the weight budget or size limitation. If the bumpers are back, this opens the possibility of incorporating the bumpers into the frame design and eliminating some material and weight with out sacrificing strength. I would try to avoid home center plywood. Grade B/BB 3/4" 15 ply Baltic Birch would be a good choice.

[Jonathan Norris]

Ok here's a perspective from a team that built many good and troublesome custom frames and have used the kitframe for the last two years. Before the kitframe was introduced for most teams the most complex and important aspect to their robot was the drive system. This was because on field success mainly stemmed from the strength of their drive systems (look at the 2002 and 2003 games). However the 2004 game brought a different direction in the games (in my opinion), going from a relitivly basic and one-dimensional game in 2003 to a very complex and multi-dimensional game in 2004. I believe that FIRST saw that innovative robots came from their success at manipulating the game objects and not how they drove around the field. This is not say that teams who built more complex drive systems (swerve for example) were not innovative, but a drive system is something you are going to need every year and inevitably many teams will be using the same design for their drive system.

FIRST introduced the kitframe in 2005 to try and stem innovation in how teams manipulated the game objects and increase the success of the rookie teams. As Karthik noted it also provided any team with a valuable resource, more time to build the important part of your robot the manipulation of the game piece. This is why my team, team 610, has used the kit frame for the past 2 seasons. The first year we used it we were able to build our first 6-wheel drive system in only 2 weeks. Last year we decided to use the same design, with the addition of an andymark 2-speed, and were able to finish it in just over a week. Giving us more time to work on the most important part of the robot, the manipulation of the game piece. This is why I am surprised more 'veteran' teams have not used it.

We have also used a tensioning system with the kit frame where we can slide the wheels to tighten the chain (which some people said cannot be done...). Basically every wheel is supported by 2 pillow blocks, pieces of 1.5" angle, with slots milled where they are bolted to the kitframe. Its the same system we have used for the last two seasons and has worked well for us, allowing us to slide the wheels back in fourth to our desire.

[artdutra04]

Team 228 is by no means a rookie team, as this upcoming FRC season will be our ninth. But for the 2007 game, we've begun to seriously consider using the Kitbot frame as the basis for our robot chassis. While evaluating its possible pros and cons, we've begun to seriously consider manufacturing custom CNC'd 1/8" sheet metal flanges, brackets, and more to fit/weld onto the Kitbot chassis to uberly-strengthen it. Rather than re-invent the wheel by designing an entirely custom-machined frame, a "CNC-modded" Kitbot chassis could be up and running faster and cheaper, while still having the same or a very similar end-result.

Plus, a chassis done in the first or second week of the build season has plenty of time to go off to be powder-coated, and still come back quick enough without interrupting the design and manufacturing of other robot components.

[redbarron]

Ok, Im not going to get into the "arguement" about kit frame or custom, but i thought i would share some of my experiences with frames. My first year was 2003 and the competition was a fairly simple one. In 2003 you had to go up a ramp and then knock down boxes. the field was split into red and blue sides and the boxes were to be put onto either red or blue and stacked for even more points and then at the end of the match it was a king of the hill game.

Now in 2003 my team (541) built a frame out of extruded aluminum and some aluminum box tubing. We won the Buckeye Regional that year and were picked as an alliance in the championship. We had no problem with the strength of the frame or the flexibility in designing a super-structure.

In 2004 there were balls to score, a large one to cap the goal and a two step platform where on the second level there was a bar to hang from. We (Team 541) had improved on our previous frame by going to aluminum channel. We did well that year and were pleased with the improvements.

In 2005 the competition was stacking tetrahedrons onto 9 larger goal tetrahedrons. A robot had to pick a tetra off the floor or get one from the human player, and then be able to stack them. In this year i joined the team i am currently on (1270) and we worked with the same engineer from the previous years. Again we improved on the frame and were competitive, including going to the finals in the Florida Regional.

Last year we had to either collect balls into corner goals or shoot them into a high goal. We again improved the frame and we again were competitive.

Now I have seen hundreds of robots and i have seen both kit frames and custom frames compete with each other. I have watched kit frames fail just as much as i have watched customs fail. A frame is only as good as it is designed, and even if a kit frame is pre-designed to a point, there is always room for customization. There is no rule to stop any team from beefing up the kit frame to make it whatever shape possible, whether it is making a square bot to play defense, a rounded one to be manueverable, or to design a conveyor system or herding area for object pick-up.

There is also no rule saying that if your team uses a kit frame this year you are required to use it again next year. As a matter of fact I remember Dean Kamen saying last year that FIRST is not meant to be an activity that only takes 5 or 6 months. So why not build what you have the resources for this year and after this years competition is over start gathering resources and designing a base that will be versatile enough to be designed already and able to compete in anything with a little modifications.

[Viper37]

Originally Posted by Donut

2 years we've used the kit frame, and 2 years we've made the semi-finals at the Arizona Regional (one we won Industrial Design award as well).

I never said there was anything wrong with the kit frame, simply that it was weak.

Our Rookie year we placed first throughout our entire regional and ended up 5th in the top 8. We took the award for highest rookie seed.

Our second year we did the same in Vegas and took the UL safety award.

[Cory]

Originally Posted by Viper37

I never said there was anything wrong with the kit frame, simply that it was weak.

Our Rookie year we placed first throughout our entire regional and ended up 5th in the top 8. We took the award for highest rookie seed.

Our second year we did the same in Vegas and took the UL safety award.

Yet another disingenuous statement. The kitbot is not weak when properly constructed. Maybe it will not stand up to all abuse in it's default configuration. But it could certainly do so in most situations, and almost definitely in any situation with the addition of bumpers. All it takes is a couple feet of aluminum angle and you can stiffen it up even more.

[Viper37]

Originally Posted by Cory

Yet another disingenuous statement. The kitbot is not weak when properly constructed. Maybe it will not stand up to all abuse in it's default configuration. But it could certainly do so in most situations, and almost definitely in any situation with the addition of bumpers. All it takes is a couple feet of aluminum angle and you can stiffen it up even more.

Disingenuous from your point of view, not my own. Save the rhetoric.

The kit bot material is weak. Wack 2 pieces togeather and note the fat chunk of aluminum missing. That is what happens to low quality aluminum stock such as what we are provided with.

On another note, last year bumpers were few and far between, seeing as just about everyone couldnt make it up the ramp with bumpers.

Im not saying this on baseless grounds. Pleanty of people agree with me.

[lukevanoort]

Originally Posted by Viper37

Disingenuous from your point of view, not my own. Save the rhetoric.

[offtopic] I've seen this an awful lot, people seem to use the word rhetoric for just about any bit of writing they disagree with. Rhetoric (according to Dictionary.com) means 1. (in writing or speech) the undue use of exaggeration or display; bombast. 2. the art or science of all specialized literary uses of language in prose or verse, including the figures of speech. 3. the study of the effective use of language. 4. the ability to use language effectively. 5. the art of prose in general as opposed to verse. 6. the art of making persuasive speeches; oratory. 7. (in classical oratory) the art of influencing the thought and conduct of an audience. 8. (in older use) a work on rhetoric. Most of the posts in this thread probably use rhetoric in one form or another.[/offtopic]

We have used custom plywood and 80/20 chassis, as well as the kit chassis. I can't say much about the 80/20 frames because I haven't had much experience with them (our last operational one's transmissions died my rookie year), so I'm just going to talk about our experiences with plywood and the KOP.

Our two robots with the plywood chassis were our '03 and '04 'bots. The chassis on the '03 robot held up admirably, especially considering the amount of abuse it withstood that year, and it still runs fine today with only cosmetic damage. (paint scratched, a couple of chips missing from a few edges, that sort of thing) The '04 frame was nowhere near as good due to the wood being, IIRC, 1/4" thinner than '03, which caused the frame to be rather flexy. Both frames were nice in that they are easy to assemble/disassemble, and don't require advanced tools to construct. The wood frames also had the advantages of being easy to adapt for a design change mid-build and replacement parts are easy to come by.

In our experiences with the kit frame in '05 and '06 (playing heavy defense each year) it provides a strong, relatively lightweight and customizable frame. For teams with low resources, or those that want a working drive base early in the season, this frame is very nice. We have had no major problems or complaints.

It is really a design decision individual to the team, but I'd recommend at least trying out the kit frame while the parts for a custom frame are made, you might just surprise yourself with just how nice it is.