Is it worth it to opt out of the KOP chassis for a low resource team?


#47

In my experience, the KoP Chassis is controversial. On one hand, it is fast to make and reliable, which is good for the chassis, a more simple yet important part of the bot. On the other hand making your own chassis (i.e sheet metal) is a great experience, is a good learning experience, is more diverse, and can be cheaper.

On our team, drivetrain is something we put reasorces and time into, in order to perfect it.

Another way of looking at it as if you rather guarantee a reliable chassis in comp, or make it into a learning experience.


#48

This thread has been a very interesting read. Our team had made the decision to try and develop our own chassis/gearbox this summer after watching the 2363 videos on building a drivetrain. Our calculations seemed to indicate that we could be build a drivetrain cheaper than the $450 voucher. We then planned on using the voucher to get additional parts so we could have two identical drivetrains for the season. We thought it would be a better use of resources and allow the opportunity for some of the newer students to practice manufacturing techniques in the off-season. We are now having some second thoughts after reading this thread.

Are there some hidden costs associated with building a tube in chassis design that we may not be aware of?


#49

If your building your own DT to save money then you probably aren’t doing it for the right reasons. IMO I don’t think building a drive train is a particularly good learning tool, if your drivetrain is as easy to build as it should be then there really isn’t much to learn.

Looking at your team’s history it looks like you had a pretty amazing season. Ranking 2nd at both your regional events is pretty incredible as a rookie. I really like the elevator + rear dumper design too. It looks like you put a lot of thought into strategic design.

That’s what makes it so surprising to me that you were unable to get out of quarters at both your events. Of course I don’t know all the details but from watching your matches it doesn’t look like your drive train was holding you back at all. What sticks out to me as a place you could improve is your intake.

While grabby intakes do work it’s pretty obvious looking at the top teams that a wheeled intake was superior. A new intake could be a really good way to walk students through the process of prototyping, design, fabrication and iteration of a robot function. This could have a huge impact on your future results and better prepare your students for next season than building a custom drive train would.


#50

You definitely don’t need a mill. Drill presses, or even cordless drills, with a hole saw can work wonders for any hole you’re using a VersaBlock on.

Here’s the process we follow for marking up our tubing for drilling.


#51

Thank you for the kind words about our season. We learned a lot. We would have loved to have been able to switch over to a roller intake, but we didn’t have the budget to buy the extra motors/sensors/intake wheels to accomplish it. That is why we are looking to shave a couple hundred dollars off the cost of 2 drivetrains so we can have money available for parts.


#52
  1. The opportunity cost. The time and effort put into designing, procuring the parts, building and refining/correcting the drive train could have been used to develop better scoring mechanisms.
  2. The delay in having a working drive train (or a second one) often means that the programmers have less time adn there is less practice time for the drivers.
  3. The risk that something doesn’t go right and the drive train has a major weakness. Been there, done that.

It is probably easier to keep the students interested in developing a better scoring mechanism.

The drive train has to work 100% reliably. If the students building it are very inexperienced, there is the chance that you end up with the situation 3) above.


#53

+1. In 2015, we made the AM14U2 into a 4 wheel omni drive (attempted an H/slide drive but failed until post season). In 2016 we made the (pre-purchased) U2 into a 10 wheel tank like thing, and in 2017 we chopped the front third off the U3 and made it into a 4 wheel relatively wide skid steer. In 2018 we went pretty straight up, using the U3 frame and wheels and belts and U2 reduction gears, but no other mods. In each case, we still spent much less effort with our drivetrain than we did in 2012 and 2013, and were more happy with the drivetrain results. How happy are we with our mods? Our 2018 off-season robot is being built on our 2017 practice chassis.

The big difference for us is confidence. Since 2015, we have spent almost all of our off-season and most of our build season effort on manipulator systems. The only time we spent significant time since then on the drive train was 2016, when the drive train WAS a manipulator when it came to our primary objective of damaging defenses. Even then, without the confidence of working with the same chassis as the previous year, we would likely not have been confident enough to build anything as good as we did.

Additionally, while I have seen many VF chassis with clamp-on gearboxes at competition, the idea of the drive train gears being THAT exposed gives me the heebie jeebies. If you go to the enclosed gearboxes, the costs appeared significantly higher than $400 when I did an analysis a few years ago.


#54

I will always suggest to a team that they use the KOP chassis (even though we don’t), but I will never discourage a team from trying something new in the offseason. If you have any questions about out chassis, please don’t hesitate to ask.


#55

I’ve never really been fond of the KOP chassis and when I was with my high school team we did custom chassis. Last year with the rookie team 7214 we did a custom chassis and will do so going forward. Buying 2x1 from onlinemetals with promo codes really brought down the cost as well as like Steve Forbes said its all about finding the best bang for the buck. If you have the resources machine wise then design and build a copy of your previous robot with the chassis upgrade if its better in your eyes then move forward with it if you feel comfortable with it move forward with it. It all comes down to you and your team at the end of the day.


#56

This thread was specifically responding to the OP, who stated that their team has a budget of $500. This is severly limiting, hence our responces of sticking to the KOP.

Your team, however, has proven pretty competent already and seems to have things more put together.

If you can prototype and know what you’re doing, go for it.


#57

Seconding Akash here - if you have the money to do it and it’s the off-season, go crazy. Don’t let any of us on Chief Delphi discourage you from trying stuff. We made a swerve drive last off-season. About 4 months of work and $1300+ later we had something running. It wasn’t quick, easy or cheap but we learned a lot and used it this past season.

Gearboxes will be your most expensive item if you purchase or build them from scratch. Odds are you’re going to drop $100 - $200 on a single gearbox depending on if it’s single speed or a shifter. So already you’ve spent $200 - $400 on the gearboxes. The raw material for the frame is usually the least expensive line item - 2 x 1 aluminum isn’t all that expensive. Factor in purchasing motors, wheels, belts or chain, bearings, fasteners, etc. and it all really does add up. Factor in the time to machine anything - gussets, drilling holes in your frame rails, etc. as well.

Time is honestly more valuable than money during build season so keep that in mind too. There’s always more money floating around out there but I can’t ever get a week of build season back.


#58

We opted out and will never go back. We used the voucher last year on some wheels, batteries, and the triple chargers.


#59

This is not useful advice without due context about your team’s resources. Are you a similar budget category as the OP? If so, how did you manage to build this? If you’ve largely been using kit chasses before now, what predicated the switch, and why are you “never going back”— what benefits did you see?


#60

I can answer for ns3517. Our resources are definitely not the same as OP and I would recommend the KOP chassis for teams in their situation. The years that we used the KOP chassis our robot budget was around $1,500. This year we spent over that much just on two drivetrains. It could be cheaper if we had a mill but if you’re going all COTS it’s going to be expensive.

Our reasons for switching:
-All of the benefits of WCD
-Since we usually modified the KOP chassis we would scrap it at the end of the season. With a COTS WCD we pretty much only need to buy new tubing and shafts.
-Easier to mount super structure to 2x1
-The KOP chassis sizes and ratios are more limited


#61

Thank you for the response! It makes a lot of sense why you would go the direction of a WCD in your situation, and I appreciate your candor about the cost of building your robots.


#62

While some advice, like the poster’s you’re responding to, may not be particularly useful to the OP of this thread, it could still very well hold as general advice for anyone who stumbles upon this thread in the future.


#63

Without any info of why I’m not really sure how it was helpful.


#64

For one or two of the teams I have worked with in the past, money was not the greatest limiting factor. Factors such as being able to design a robot that was manufacturable and having enough students and mentors adept enough at manufacturing were the major constraints.

I believe that one of Karthik’s Golden Rules is relevant here.


#65

Keep the KOP and use the money to maintain your batteries. One of our newer mentors has been adamant about purchasing battery-minders and desulfators - something like this. There are other battery minders/tendors on the market that may suit your needs, check around.

Another area to make certain your KOP is up to snuff is to use new motors for each competition - as I have been told that they degrade over time (thanks, Eric). The more advanced teams seem to swap the CIMs out after each competition…

After that, well there are so many options. I would look to your Motor Controller usage first.


#66

Absolutely - we ran into this some this season as well. Week 6 rolls around and everyone is exhausted, people skip a meeting here and there & there are less hands to accomplish what needs to be done. Build within your means and you’ll be less likely to get burned out.