I just watched:
http://www.simbotics.org/media/videos/2011/presentations/kitbot-presentation-kitbot-steroids
They seem to be really advocating the KitBot in this video, yet 1114 themselves and most of the advanced teams build a sheet metal chassis. Which is better?
Do you have a sheetmetal shop and designers with sheetmetal experience?
Yes? Build sheet metal.
No? Build Kitbot.
It’s not about which is better, it’s about which is better for your team. For a lot of FIRST teams, they have the resources (financial, material and experience) to build custom drivetrains that can be very lightweight, yet maintaining robustness and effectiveness. However, most FIRST teams don’t have these resources. As such the kitbot can be a great solution for them.
The “kitbot on steroids” as we’ve coined it, is a simple drivetrain that be put together in a couple of days using just the KOP and a few additional COTS parts. When constructed properly, it’s extremely robust and reliable, and far more effective than the average FIRST drivetrain. (At least based on what we’ve seen over the years.) The time and resources saved by building this drivetrain allow teams to focus on practicing, programming and of course the designing and building of other manipulators. For years it’s frustrated our team to see so many teams with so much potential who end up with underperforming custom drivetrains, that could have been easily avoided. That’s why we made this video and have been promoting it heavily. Look for us to publish improved documentation to go with it this fall.
One sentence and Karthik sums up about 75% of the “which is better” threads on CD. Talk about hitting the nail on the head!
Jason
I just want to open your eyes to what can be done with the kit bot.
the chassis in the picture is my team’s (3339) chassis which is built from the C channel. We drilled holes to the outer wheels shafts in the c channel.
This chassis worked very good without any problem!
Very cool! I really like this re-arrangement of the kit frame. Thanks for sharing.
you can do what ever you want with the kit bot, you just need to think out of the box
Here is the Robowranger 2011 “custom sheetmetal” chassis:
http://1.bp.blogspot.com/-FiqGQ9OI708/TdUiRSHBTuI/AAAAAAAAAzw/LfQ2beZ8Nkc/s400/GHS2011-110+Rev1.JPG](http://1.bp.blogspot.com/-FiqGQ9OI708/TdUiRSHBTuI/AAAAAAAAAzw/LfQ2beZ8Nkc/s1600/GHS2011-110+Rev1.JPG)
It probably looks familiar.
Custom sheetmetal? Yes.
Reinventing the wheel? No.
2005 Kitbot FTW!
It looks like you were set up to run 6wd as well. Was that a contingency plan if the nonadrive didn’t pan out or you were too close on weight?
I threw the tabs on for versatility reasons. We figured for the weight of 4 tabs we would now have the ability to switch to a 6WD if the game needed it.
We’re very happy with our “Butterfly Drive” setup. We’d be happy to run this configuration again!
-John
That’s what I figured. It’s a really clean frame layout and your nona/butterfly/whatever-crazy-drive-next-year certainly inspired a ton of teams this season.
Our team, 3467, used this chassis this year and it worked really well! The only downside is this pre-assembled chassis comes with wedgetop, not roughtop tread which wore down us easily this year. If you talk to AM they should be able to give you roughtop plactions over wedgetop.
Just keep in mind when making the decision to go with supershifters over CIMple boxes the weight vs. having a lower gear. Also, if you use the supershifters be careful and fully aware of what you are doing during assembly. Somehow ours had an extra washer in one that would compress the tranny, overheat the cims, and cause them to shut down for a few seconds. At the beginning of the season/regional our driver was losing one side of the drive for a split second in a few matches over the weekend and we didn’t thing much of it. In St. Louis the problem grew astronomically to happening every few seconds and lasting a while. We diagnosed everything electrical and mechanical and even had an AM rep look over the supershifter guts. When nothing worked we carefully examined the guts and realized there was an extra washer. Problem solved.
Lesson learned: even the smallest parts can cause a world of pain. Check, check, check, check, check.
Thanks for pointing this out. As a FIRST newbie, I was extremely impressed by the quality and versatility of the kit chassis and drive train. It is a beautiful piece of engineering.
Team 3504 did something similar to “kit chassis on steroids” this year, but we had complications with chain tensioning system. In the video, it looks like the chain lengths just worked out without the need for extra tensioning, but that is not how it worked out for us. Is there a certain sprocket size you need to use? Is there some other trick we missed?
Thanks,
-George
I’m not sure how 1114 routed the chains in the video, but we’ve dead spaced axles for the last 3 years (once using the kit frame) and haven’t needed a tensioner. When using #35 Chain, if your axles and transmission are spaced using factors of 3/8" (3/8" is the pitch for #35 Chain) then you’ll always end up using an even number of chain lengths.
I have found that especially with longer lengths of chain the stretch becomes a big issue. A chain run that seemed perfectly tensioned may be really loose after you drive the robot hard for a few minutes. We have tried pre-stretching our chains and it helps but we still threw on some tensioner this year.
~DK
Two things that you can do to help alleviate (but never entirely eliminate) stretch:
Use #35 chain. Stretches much, much more slowly than #25.
Use high quality chain. You get what you pay for - we have found that different manufacturers’ chain tends to stretch at very different rates.
Keep in mind, of course, that this advice holds true only if everything is collinear.
I will rephrase the question: When done properly, what advantage does a sheet metal chassis have?
Thanks for the advice. We used #25 this year mainly because we figured we could make our lengths more precise because each link is smaller, we also used half links which we had back luck with and ended up scrapping. I will look into where we buy our chain from. Do you have any recommendations as far as good chain suppliers?
To add a bit to this topic we have always (in my years on the team) used the kit-bot chassis with some modifications (some minor some major). We have done 6 wheel rocker, mecanum and 8 wheel rocker and even Ackerman drive with the kit-bot chassis. We do not have access to a sheet metal shop but we have found that the kit-bot frame is a great foundation and with some more support it is incredibly sturdy.
~DK
