Standard vs. Custom Frame

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.

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.

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.

[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.

Ok… The Idea of the kitbot frame being weak is something that I had to batter out of my teammates’ collective heads when it first came out. The arguments came up of weight, strength, and versatility in designing additional components. Weight was no problem, we just took a 2’ length of extruded and a 2’ length of kitbot rail and weighed them… even though the kitbot was slightly heavier, the difference was so slight that it didn’t matter. Strength was a little harder, and after thinking it over, we decided to test this by smashing samples of both materials in an Arbor press. The Kitbot rail performed exceedingly well. After a little discussion about the ease of adding functional modules to the evenly spaced holes in the kitbot frame, we decided to go for it. We liked the way it held up the first year, and decided to use it again last year.

Last year, we were one of the most physical teams on the field, and the kitbot frame stood up to everything we could throw at it: High speed collisions, 5 robot pile-ups, everything. All with no bumpers and a removed front rail… with the default configuration. The frame is still as structurally sound as the day we shipped it.

The only problem we’ve had so far, is that the middle axle hole in the frame oblongs and causes drive-chain issues. We only noticed this last year, after two regionals (one of which we won), championships, and an off-season comp.
I believe that signs of wear can and should be expected after the battering we put it through in those four competitions.

And as for This comment:

We won the Philly regional last year.

I did not write this post on baseless grounds, either. I wrote it on two years of experience with the kitbot frame.

So my reply was deleted…

Ok then.

Ill just retype it.

Im speaking from 2 years of using the basic kit as well.

Instead of guessing at whether the kit bot is “strong” or “weak” maybe its time we actually did some tests and found out…

These are stress analysis tests my team did with inventor 10. All peices are the same length, and subject to the same variables, so it should give you a pretty acurate comparison.

Kit Bot Side Rail:

10-10 80/20:

Al Tube Stock:

These are all deformation tests. You may be suprised to find that the kit-bot rails are the strongest (which makes sense considering their profile).

I have only the vaguest understanding of how these tests are done. One of our mentors did them.

Despite these tests my team has decided to use 80/20 in our drivetrain b/c it will make chain tensioning easier (we had more problems with chains then frame breaks).

Your reply consisted of nothing but a smiley face. If contributions aren’t relevant to the thread or forum, they’ll be deleted.

Weak is a relative term. Whether a person thinks something is weak is their opinion. One thing I have learned in FIRST is that everyone has their own opinions with regard to designing robots.

If someone designs their robot so that 90% of their weight is in the structure of their drive base, then the kitbot chassis is probably not for them. Also, if a team uses their robot as a rolling brick without any regard to scoring the game object, then again the kitbot chassis is again maybe not for them.

The kitbot chassis is not “low quality aluminum stock”, if I recall correctly. It is 5052 H32 aluminum.

It may not be for all teams. If a team wants to have some weight left over to have an arm, a lift, a shooter or a latching system and they don’t want to spend much time on their drive base, then the kitbot chassis is a perfectly fine structure to use.

Also, many teams got on the ramp while using bumpers. The teams who did not succeed in this either chose the ramp to be a low priority or they did not design their drivebase well.

Andy B.

Reminds me of talking about “cool air” - with the Engine (jet) Group. You can roast a turkey in air they think of as cool.

One of the best things you can do for the kitbot is to fill the center bay with a plywood sheet and fasten it to the rails. This will drastically increase the strength of the frame. If you do this and still think the kitbot is “weak” then I suggest you plan on your next robot weighing about 200lbs with a “structurally adequate” frame.

On the other hand I can readily see how somebody who did not do this and just mounted their controls on the cross plate that goes over the kit trannys would regard the frame as weak.

That is because tying the front and back pieces together with a piece of plywood creates what is known as a shear web. Those front and back pieces are effectively turned into an I-beam 36" deep. It will be far stronger than required for FIRST. The key is proper reinforcement in the proper place.

Also, I’d like to thank everybody for all the great advice they’ve given us over the last few days. I appreciate it a lot. You guys really have put in a lot of thought into this, and it’s been interesting watching this exchange of ideas.

??? What competition were YOU involved in? I would say most of the teams we competed with (through 2 regionals and the championship) had bumpers, and I don’t recall seeing ANY team that couldn’t make it up the ramp because of them. In fact, being traction limited on the diamond plate ramp probably made the bumpers an asset because of the added weight.

Andy already commented on the “low quality aluminum” - 'nuf said.

Time to take a breath and get ready for next season. I recommend you do some detailed research and not make such quick judgments about major components. Most of these decisions are not black and white, they are shades of grey, so making such generalized statements about these are all good or these are all bad is pretty much “baseless”.

You must spread some Reputation around before giving it to Gary Dillard again.

custom frame is much better but it also has more work that needs to be done:

Custom frame is better, if you can make a custom frame that’s of a higher quality than the kitBot, AND you think its worth the time.

A custom frame may be your only option, if you’re doing treads, or something, and value your time.

I don’t even think about questions like these.

Are you asking if the KitBot is any good? If so, then yea, its not bad.

Just a correction but team 1625 has used a custom chassis for both years of its exsistance. Here’s the link to the picture our 05 chassis http://www.chiefdelphi.com/media/photos/20834

and there is no good picture of our 06 chassis

I would like to add that custom chassis take a lot longer than kit chassis but our 05 chassis gave us a really really low center of gravity and that helped a lot. This past year it was made to fit what we needed and it worked excellently. Lucky for our team we have an amazing ex-engineer who can aluminum weld very well. Without him we would have probably used the kit chassis. We also have some pretty nice prototype drivetrains that have really nice chassis.

Folks,

The frame is just what holds the all important drivetrain to the rest of the 'bot that does the work. As long as the frame holds it all together and isn’t a source of problems, then why worry about it? Our first year robot had a plywood & pine frame. The drive wheels were made from laminated 1 x 4 pine boards with rubber tread glued and stapled on. It did the job, and we had no failures in two competitions.

For those of you looking for good chain tensioning for the kitbot, I finally got pictures up of what we’ve used the past 2 years.

http://www.chiefdelphi.com/media/photos/26057?
http://www.chiefdelphi.com/media/photos/26058?

With them we’ve only lost 1 chain the past 2 years (and this was due to another robot hitting our sprocket, bending it at a 90 degree angle, and thus popping the chain off). They are relatively easy to add and can be attached pretty much anyway along the length of the wheel track.

My son made some great chain tensioners out of old skateboard wheels. Cut the groove on a wood lathe at the school shop with a sharp cutoff chisel…