Metric Teams

[timytamy]

Now that championships is over and some of us have slightly more time to breath, I thought I'd ask CD to humor my curiosity.

This year our team went to the Orlando regional, where we had the pleasure of meeting team 342, who to our surprise, used primarily metric hardware. We got fairly close to them as they became the main team that we lent parts to and them to us. Their main reason was that the sponsor whose shop they use is almost completely metric, so it made sense for them to go down the base 10 route.

In Australia, we are officially metric, although there are still some places where you can get imperial parts but they are harder to get and more expensive. Our rookie year the bot was a complete mess with both metric and imperial everywhere, as we went on we used less imperial. This year the entire bot being metric, apart from wire sizes and the drive chassis (and even there we are migrating towards M6 instead of 1/4").

So what other teams use metric, and for what reasons do those teams uses metric?

[Jeff Pahl]

Drivetrain and ball feeder was all imperial. Shooter was almost all metric. It was designed by two brothers who moved here from overseas last year, who are on a mission to try and convince the rest of the team that metric is better.

However, we can buy imperial hardware by the pound at the farm supply place in town, so until metric hardware can become price competitive with that, we are not going to switch.

All the plywood we used to build the entire chassis was metric sized.

[Nemo]

We use a lot of M4/M5 screws for metric Bosch T-slot extrusions that one of our sponsor donates. 20 mm Bosch is a nice size for FRC.

[Tristan Lall]

I'd rather use metric, but always end up with a mix (and mostly imperial), because of supply limitations.

I think TechnoKats (45) standardized on M5 screws a number of years ago, but I don't know if that's still their common practice.

[Mark Sheridan]

I think 217 is metric. maybe?

[MrForbes]

I had to go to the hardware store to buy some metric screws to mount the Fisher Price motors.

Everything else we do in inches, because they're fantastic. None of that "divide by five" nonsense

[Wetzel]

We were mostly imperial this year on 2914, I think. We used hardware that we already had in the shop, the only things we bought were 2 inch deck screws for building the crate. We even managed to (unintentionally) replace the M5 nut on the PDB with an imperial nut. When I was on 1884 in London, England, we were mostly metric - including wire gauge. IIRC, we had to ask for special permission to use it and had the email from FIRST with the approved substitutes for the AWG specified in the manual.

I would like to use metric, but it's hard to give up the supplies on hand or to mix and match units.

Wetzel

[Alan Anderson]

Originally Posted by Tristan Lall

I think TechnoKats (45) standardized on M5 screws a number of years ago, but I don't know if that's still their common practice.

We did M3 and M5 almost exclusively for a couple of years, and were well on the way to getting rid of most of the remaining Imperial stuff. Then mentor turnover and some well-meaning but uninformed shopping ended up with a large collection of 1/4-20 and other assorted hardware. We haven't quite hit the other end of the pendulum swing yet, but I have some hope that those in charge of design will soon figure out that the large number of different tools required to maintain the 'bot the past few years is something to avoid.

[Mr V]

The only metric we use is for mounting those motors with metric threads. It just isn't that practical in the US, the selection at most hardware stores is minimal and if they do have it the price is much higher.

[Sam Crow]

Since 2010 we've been using 30x30mm Bosch extrusion for robot frames and metric hardware (M6, plus a little bit of M5 and M4) to connect things to it. The AndyMark drivetrain parts are designed in the imperial system, so we have to use imperial hardware for drivetrains. For everything else, people mostly use M6/M8 hardware (because we've accumulated lots of it) or smaller imperial hardware from our pre-2010 stockpiles.

[Savvy578]

My team usually uses about half and half. However, at the end of this build season, we got rid of all our metric wrenches and we're trying to move over to completely imperial. Yet, other than bolts, we use fully imperial for measuring.

[Paul Copioli]

217 is mostly metric except for where Imperial is the only option like the CIM motor mounting.

The only real exception to this rule is for our bumpers where we use 1/4-20 PEM Studs on the robot. We do this because IFI has an obscene number of 1/4-20 wing nuts that are perfect for bumper removal.

M4 and M5 screws are our standard, but we mostly use rivets anyway so the screws are at a minimum.

[Tristan Lall]

Originally Posted by Savvy578

My team usually uses about half and half. However, at the end of this build season, we got rid of all our metric wrenches and we're trying to move over to completely imperial. Yet, other than bolts, we use fully imperial for measuring.

The power distribution block is going to cause you grief. You can't easily tighten the metric nuts sufficiently with an adjustable wrench.

[Cuog]

Except those few silly metric parts 422 is all imperial. In fact someone on the team has a love affair with 1/4-20 as that's what was used for about 90% of the bolts on our past 2 or 3 bots.

My mill and lathes are inch machines, so anything I make for the team needs to be specified in imperial anyway.

[Mk.32]

We are all imperial expected pre-threaded holes on the FP/PDB etc.
It is just easier for all the students who are used to it, and mentors who are as well [most of them can do both]. In addition most of the machining gear we have access to are set up to be imperial. In addition AndyMark and a lot of parts we have are already imperial.

I think for most US teams it just makes more sense to do imperial for the above reasons. 1/4-20 all the wayyy