Standard vs. Custom Frame
 

We are trying to decide whether we should use the standard stock frame that comes with the kit of parts or build our own custom frame. Since we don't really have any adults helping us with CAD-ing, our concern is that we would make technical mistakes while designing the frame (this happened to us last year). Can anybody weigh in on the advantages and disadvantages of using a custom built frame instead of the stock frame? Also, could anybody give us a link with drawings of frames that teams built last year?

Thanks,

Daniel, Team 1560

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

Main advantage, less weight, more adaptability and more customizing.

Re: Standard vs. Custom Frame
 

On the other hand, Using the kitbot frame could save you two weeks of design/build time. You can do alot to a manipulator/shooter in two weeks. 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. We have used the kitbot frame for two years now and have been strong competitors for both of those. There is something to be said about having a driveable base a week after kickoff.
The one thing I would suggest improving though, is the et of wheels that comes with the kit. While they'll get you where you're going, they are by no means the grippiest wheels out there. There are numerous things you can do to increase their traction, but there are also quite a few alternatives.
Colson Wheels are one of them, but there are a number out there.
If you are worrying about CADing a frame, then look to Extruded Aluminum.
Welded frames are fine and dandy if you have an experienced welder at your disposal, but if you don't exactly know how, they can result in a lot of wasted material and a mediocre end result.

Re: Standard vs. Custom Frame
 

Custom Frame hands down. It is much lighter and it is much more easier to change. Also if you need to add support to it later it is more simple because all you have to do is add some trusses and make a few other changes and you are "made in the shade."

Pavan

Re: Standard vs. Custom Frame
 

To answer your question Daniel, it really depends on what the team wants and what they are looking for as well as how much resources does that specific team has.

Now let's look at a veteran team who has members who have been through this design process a few times, engineers to correct their mistakes, resources to make what they want. Ofcourse they will want to go with a custom frame where they have the flexibility to work with what they want. After given the game, they will design chassis such ways to satisfy their needs.

Let's look at a rookie team, or a 1st or 2nd year team. They have dedicated members, engineers who are there to help. But they haven't been exposed to FIRST or they haven't been to as many competitions as a veteran team has. What I am trying to get to here is experience. Due to less resources, teams may want to go with the kit of part chassis.

In both ways, there are pros and cons. You ask how? If you use a custom frame, it will take time to design it, machine it, put it all together (like Cody pointed out in his post). On the other hand, if you decide to use the kit of part chassis, it will only take you the first week of build season to put it all together. That's just one example.

There have been many teams that have been successful with the kit of part chassis. For example, Team 121 and Team 1625. The reason I used those two teams as an example is because one of them is a veteral team and the other is a 2nd year team.

My team (team 1345) is a 4th year team. In the first two years, they have used extrusion and aluminum tubing to make their frame. Last year, they used the kit of part chassis. This coming year, we will be using a custom frame, we will see how it turns out.

Bottom line is, if you have the resources to make a custom frame, then why not? But if you don't have the resources, don't take the risk.

Re: Standard vs. Custom Frame
 

I think a custom frame would be preferable if it is possible; but if you don't have the resources to pull it off effectively, and want to save yourself some time, the kit frame is definitely a good option. So many pre-drilled holes give you lots of nice places to bolt stuff onto (not that you need pre-drilled holes, as I assume your team owns a drill, but they're nice), and the frame is extremely adaptable, being able to fit most designs you can think of (cut a few frame pieces and you can make almost anything fit).

The only thing to worry about with the kit frame is strength and possibly weight; not strength from taking a hit and coming apart, but more from a mechanism or large amount of weight causing the C channels to start to collapse. We had to wedge a piece of extruded aluminum into the frame to keep it from folding in underneath our motor mount for our conveyor belt. Weight I suppose could be an issue, though we haven't had it be a problem yet.

Re: Standard vs. Custom Frame
 

You can always cut a piece of wood board to fit perfectly into the c-channel pocket. This would prevent it from collapsing as well as being light in weight and cheap. (Plus wood is all-around easier to work with.)

My vote is with the kit chassis, because it's light weight, strong, free (-6K), and easy to find replacement parts at a regional simply by asking other friendly teams. Just remember to replace the nuts that come with the kit for real nylon insert locknuts or else you will end up missing some screws here and there. ;)

Re: Standard vs. Custom Frame
 

We use custom and always have. (There wasn't a Kitbot frame back in 1997 or so.) However, just because another team uses a custom frame doesn't mean you should. Some things to consider:

• What attachments will you be adding and how? Will you need special modifications (such as a raised end to help slurp up balls last year)?
• What do you have readily available? If you want to do an easy custom frame, are parts easy to come by? Can you get the frame welded? (very important for many teams)
• What drivetrain are you looking at? A basic 4 wheel, 6-wheel, or mecanum drive could be used with a kit frame, but for swerve or holonomic (non-mecanum), it would be much harder, and I'm not sure about tank treads.

The other thing is that nothing is stopping you from using a combination frame. What I mean is that you could use the kit frame as a base, then secure the rest to the top. You could even weld the kit frame together, thereby avoiding having "robot droppings" as nuts and bolts work loose.

For 330's base the last two years, we have used 1"x2"?(not totally sure)x1/8" box tubing, arranged something like this:

--------------------------
I I I
--------------------------
I I
I I
--------------------------
I I I
--------------------------

edit:the I's should be in the middle of the center, spread out, and at the ends and middle of the outside--Firefox spell check doesn't like all the spaces though./edit
We also have something across the ends of the center.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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?

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

i would go custom, in the end it ends up being easer because you can diesgn it to fit the robot and not the other way around. and who needs CAD, i do everything to a 1cm for complex to 10cm for big simple components on graph paper, and the best part...you still have the design at 3:00 am ship day when the power goes out. another helpfull thing is full-scale cardboard mockup, you can never go wrong with cardboard and duct tape.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

Looks like there are sprockets attached to the wheels to me. Dead axle drive.
Hmm.. seems like they tensioned the chain by pushing in the slack in the middle of the chain run. It looks tight in this picture, but remember this is a picture from the build season. In my experience FIRST robots get about a link and half of chain stretch over an event. Having an adjustable, simple tensioner may (or may not) prove to be worthwhile.

Re: Standard vs. Custom Frame
 

I am almost positive it is live axle, I know I talked to Rob from 121 about it, if you look at pictures of the robot from the year before you can see the drive system better, the design is almost Identical, other than the addition of more clearance this year.

Re: Standard vs. Custom Frame
 

They used bushings.

If you want to use bearings (which most people do), you can't do it without mounting pillowblocks on the top of the frame.

Re: Standard vs. Custom Frame
 

Touche

Re: Standard vs. Custom Frame
 

This thread has started to drift a little, but I will pull it back towards the original focus.

The kitbot frame is one of the best things FIRST has done to help rookie teams. Teams that don't have access to machine shops or lack the engineering support to design their own frames can use the kitbot frame easily. It is robust, comes with a fairly good drive train already, and is already designed and fabricated. There may be a weight/customizability/quality trade off, but if you have the choice between having your not-so-hot self-made frame breaking and you being dead for the rest of the competition and using a less-than-perfect kitbot frame, I think the decision is easy.

Re: Standard vs. Custom Frame
 

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

Re: Standard vs. Custom Frame
 

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!

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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!!

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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. :D

Re: 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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

[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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

So my reply was deleted...

Ok then.

Ill just retype it.

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

Re: Standard vs. Custom Frame
 

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).

Re: Standard vs. Custom Frame
 

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

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

??? 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".

Re: Standard vs. Custom Frame
 

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

Re: Standard vs. Custom Frame
 

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

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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.

Re: Standard vs. Custom Frame
 

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...

Re: Standard vs. Custom Frame
 

We were going to use some great tensioners last year but ran out of weight budget. Ill find them.

They are nice because they mount nowhere, and straddle both sides of the chain.

Re: Standard vs. Custom Frame
 

Team 85 used the kit frame the past two years with great success.
We used the kit frame to free up time to focus on the challenge.
I can not say if we will use the kit frame this year, Our students will make all the tough decisions ;) after kick off.
I think the kit frame is a very good stock frame.
And you can win using it.

Tim

Re: Standard vs. Custom Frame
 

Custom frames are by far the superior in performance, lightweight and strong if well designed.

However, you must design everything first. Randomly drilling mounting holes afterwards with a hand-drill is unprofessional and mistakes can happen.

I design the entire robot first, including electronics and wiring. Then you make everything. If you're good, you can machine and weld the frame in 20 hrs work or less.