Yet another new mentor question - how much to order preseason?

[trycatch]

Since we're only a second year team (and last year fell on us right before kickoff), I'm still feeling a few things out. One is how much to stock up on stuff during the pre-season - with the six week build season it seems very prudent to stock up before build season gets going so you can hit the ground running, but at the same time knowing what the game is so you can spend more wisely would be nice to some degree to. How does your team handle this? How much do you do in advance vs. after kickoff?

Thanks for the input!

[tjwolter]

Also second year so perhaps pondering the same questions. There are some things you just know you will need. Use FIRST choice to lay in a supply of speed controllers for instance. You can roughly guess what might be in the kickoff kit, but it is not a bad idea to get a few staples such as wire, connectors etc. We are going to use more 80/20 this year and hope to have a stock on hand by January first. We are going to build two machines this year which stresses the logistics more.
T. Wolter

[asid61]

115 ordered stuff that we knew we would use before the season, such as:
1. Bearings. We use these every year!
2. Hex shaft. Also common.
3. 2x1 tubing in 1/8" and 1/16" wall thicknesses. We run through around 32-64ft of this stuff each year.
4. 1x1 tubing in 1/8" and 1/16" wall. Maybe around 16ft per year.
5. Sprockets. Need these for drivetrain and other applications.
6. Versaplanetaries. If we're running low we pick up some more.
7. #25 chain, although we bought 100ft in 2015 and didn't buy any 2016.
8. Screws and nuts to refill lows. 1.5" long screws run out pretty quickly. We don't like to re-use nylock nuts. Rivets are also a refill item.
9. Drill bits, taps, etc. if we need them.

Generally it's raw stock and tools that we stock up on.

[pandamonium]

Originally Posted by tjwolter

We are going to build two machines this year which stresses the logistics more.
T. Wolter

I would recommend doing the electronics for the second robot before build season.

[tjwolter]

"Doing" or getting the parts for? You can't actually build anything that will go into the comp machine before 7 Jan. And the actual basic electronics don't seem to be an obstacle, we are second year in FRC but have a good pool of students with experience in speed controllers etc. Now, the tricky stuff with sensor integration, on board Arduino stuff, sure. But we have no idea what we will be building yet. We are a very focused team. Last year we had a finished machine in the middle of week 5. It promptly broke, true, but we still had time for everything to be solid before Bag and Tag.
T. Wolter

[AriMindell]

Our team makes a lengthy pre-order before each season. Our pre-order includes electronics, sensors, and tools that we are interested in using during the season. Keep in mind that the electrical system varies little from year to year, so you can almost pre-order the entire thing.
In addition this year, we CADed our drive train in advance, so the materials for that are on our list as well.
Here is a link to our pre-order if you are interested.

[pandamonium]

Originally Posted by tjwolter

"Doing" or getting the parts for? You can't actually build anything that will go into the comp machine before 7 Jan. And the actual basic electronics don't seem to be an obstacle, we are second year in FRC but have a good pool of students with experience in speed controllers etc. Now, the tricky stuff with sensor integration, on board Arduino stuff, sure. But we have no idea what we will be building yet. We are a very focused team. Last year we had a finished machine in the middle of week 5. It promptly broke, true, but we still had time for everything to be solid before Bag and Tag.
T. Wolter

If you are in fact doing 2 complete robots you can start making parts for the practice one such as assembling the electronics. Even if your team is really good at this it is still a few days worth of work that can be saved.

[BrendanB]

For some teams with smaller overall budgets you don't want to pre-buy too much. If you have some budget to spend, stick to the basics to get you through the first two weeks of development and some initial building. My optimal pre-buy would be some Vexpro Versa Frame stock in 1x1 & 2x1 so we can start building some of the base assemblies before the larger order is placed when we know our needs. Hex bearings, hex shaft, some gussets, 12awg wire, andersons, motor controllers etc. Unless you have a healthy robot budget you really don't want to go too far past the essentials or you'll start locking yourself to using items you wouldn't prefer using but you already ordered them so you might as well.

If the budget is tight I find its wiser to just focus on having some essential items for good prototyping like an intake using hex shafts, bearings, and some wheels. Having a gameplan for a driving chassis in the first few days is also valuable.

As long as you keep it flexible and within the reasons of your bank account you can't go wrong. I wouldn't recommend buying things like specific ratios of gearboxes.

The reality is you won't miss out on much unless you wait until late January to place your initial build orders for key items. The harder items to acquire are the game specific robot parts that are hard to predict like 8" pneumatic tires this year or banebots wheels in 2015, but some of the larger companies like Vexpro and Andymark do their best to react to the FRC market with alternatives or quick replacements.

[jayred1127]

One thing to order for pre-season is metal. It's always good to have C-channel and L brackets. You can build a whole robot just with those.

Another thing are wheels and/or tank drives. If your budget allows you should have something for each type of drive. If not decide what wheels you are using in the first week of build season. AndyMark never fails to run out of the most popular wheels every season.

[GeeTwo]

This is one of those many things where the true answer is "it depends," mostly on your teams budget and design/build process. My experience follows, along with the reasons; your mileage may vary.

The limiting factor for how much stock to pre-order is set by budget ($$) and storage facilities. Inventory ties up your money and space in things you can't easily exchange for other things you might need, but some of those items may save a lot of down time waiting for parts. Dollars in the bank are more versatile, but take time to become parts, especially if you have to work through a school or other bureaucracy on top of shipping time. Possibly that was obvious to you, but probably not to at least one reader of this thread.

A team which is heavily based in CAD (especially if they outsource machining to a sponsor or contractor) might go into a season with practically no inventory, whereas a team which builds a prototype and iteratively tinkers with it until the clock runs out will need to have stock and basic parts in hand in order to do their best. (We're about halfway down that spectrum, working our way slowly towards CAD.)

When selecting WHAT to pre-order, we prioritize based on likelihood that we will use the parts in any given year, then on the lead time to get an order, and thirdly on the amount of money it will tie up. Unless you have a lot of cash, don't bother stocking up on things you can consistently obtain locally if aren't pretty sure you'll need them. (Again, put it in context of your team!) -- Don't be afraid to let your local hardware store or home center hold your inventory.

In case it isn't obvious from what I've already said, get to know your suppliers. At a bare minimum, go to the AndyMark and Vex and your other online vendors' web pages and figure out how many days it takes them to ship you something, and become familiar with your local vendors' stock and hours. My example: Slidell is 2 day ground shipping from both AM and VEX, and has four hardware stores (one of which is really just a garden and feed store), three home centers, and a metal supplier. None of them stock quite the same things, none are the same distance away (OK, two of them are pretty darn close), and they have different store hours. When the team figures out they need a part, being able to glance at my watch and know who (if anyone) is going to be open when I get there and would likely have that part saves a lot of wasted miles. The last two build seasons, I have spent at least a dozen hours between Christmas and kickoff scouting the local suppliers. I plan to do it again this year, because it clearly paid off, even before you count the relative weight of "off season" vs "build season" time; factor that in, and it was a grand slam.

As for pre-building parts of the "second robot" (suggested by other posters), we do NOT do this, for two reasons.

1. We do not decide what needs to be on our control board until after we've designed the robot, which is after we've worked out our high-level strategy, which is after we've given the rules a couple of good reads.
2. Second, but even more importantly, we do not build a practice robot and a competition robot, but two essentially identical robots. We do not know a priori which robot we will bag and which we will keep for driver practice and iteration. In 2015, we literally changed our decision on which robot to bag on Tuesday afternoon when "chassis 2" (Peabody) suddenly came together, at least to the appearance of those of us who had been focusing on chassis 1 (Atlas) for most of the preceding week.

[dirtbikerxz]

Originally Posted by pandamonium

If you are in fact doing 2 complete robots you can start making parts for the practice one such as assembling the electronics. Even if your team is really good at this it is still a few days worth of work that can be saved.

Define what you mean by "assembling" electronics. If you mean just wiring the roborio, motor controllers, pcm, vrm, and pdp together and putting it all on a board of some sort, that can be done within 30 minutes by an experienced crew (2-3 people). Doing this after you know the game and the basic design of the practice bot gives the added benefit of arranging stuff in a way that will fit well into the bot.

[electroken]

We already know we'll need bumpers this year, so a box of solid pool noodles would be nice to have ahead of time. I'm sure the Florida teams can buy them whenever they want them. Probably a bit tougher to find in Minnesota in January.

[efoote868]

Originally Posted by pandamonium

I would recommend doing the electronics for the second robot before build season.

Very difficult to do that until you know the game, how your robot is going to interact with the game and number of motors / actuators needed. Even something as "standard" as a drive train will vary wildly from year to year due to the field.

I would recommend obtaining any sensors you intend to use this season, or in the near future seasons and begin prototyping / learning how they work.

[Lil' Lavery]

It all depends on your resources. If you're on a tight budget, order what you'll know you need ahead of time, and then make other orders as soon as you need a part. Determine what resources you have left over from last year, and if you want to re-use any of your electrical components from your previous robots (namely the RoboRio, power distribution board, speed controllers, or voltage regulator module).

Have enough raw material and hardware on hand to be ready to prototype right away. For prototyping, typically that can be some plywood, 2x4s, and wood screws.

If you have a bit more resources, buy yourself a new set of electronics and make educated guesses as to what you'll be using in the build season. We always place orders with Vex, AndyMark, and McMaster during the pre-season at the very least. We stock on up on electronics, wire, raw aluminum, polycarbonate, fasteners, shafts, bearings, gears, sprockets, VersaPlanetaries, and WCP SS gearboxes. We also take inventory of our tools and see what could use replacements.

[Taylor]

Another difficulty is how your team builds the robot. Do you have parts custom made for you by a local fab shop, or is most of the manufacturing done in-house?
Either way, I'd load up on tools and hardware. Determine what type of connectors you'll use (1/4-20, 10-32, 10-24, rivets, etc.) and get a bunch of that. Also tools specific to your connector. AndyMark sells packs of individual tools - just the ones you need, not a big huge full set like at the home improvement stores. (Tip: put colored electrical tape around tool handles so you can easily identify by color)
Also prototyping materials are always nice. Plywood, 2x4s, etc. Stash big, empty cardboard boxes - they come in handy.