English or Metric?

[Jeff Waegelin]

We usually use English measurements and fasteners. We've had a lot of variations in the past, but last year we actually cut down to just two sizes of screws and two sizes of Allen bolts. It made it a lot easier to keep track of what was what. The two sizes of each were visually different, so everyone knew which wrench to use.

[Andy A.]

As was said before, adjustable wrenches become your friends, fast. As do leathermans. I know it's wrong to tighten a nut with plyers, but it's a hell of a lot faster then trying to find another wrench. Then locktite the whole silly thing so you never have to worry about it again. If it breakes, it stays broke, but you don't have to dig out you're tools!

Has anyone had any expeience with an adjustable socket head? I remember seeing ads for one, were the inside of the head was filled with spring loaded pins. I always wondered if they were worth the price.

-Andy A.

edit: spelling and other silly things

[Johca_Gaorl]

Originally posted by Andy A.
Has anyone had any expeience with an adjustable socket head? I remember seeing ads for one, were the inside of the head was filled with spring loaded pins. I always wondered if they were worth the price.

/me is not entirely sure.

My stepdad would say definitely no, and I am strongly inclined to agree with him, however, it would be soooo nice if that worked. I am pretty sure they won't take the torque they are claiming (200+ lb-ft) but I doubt anything on the robot is getting tightened near that tight. Head bolts the performance-built 351W my stepdad has don't get tightened that tight

[Wetzel]

Originally posted by Andy A.

Has anyone had any expeience with an adjustable socket head? I remember seeing ads for one, were the inside of the head was filled with spring loaded pins. I always wondered if they were worth the price.

They round off the nut head.
Not a good thing to have happen to a nut head.


Wetzel
~~~~~~~~~~
narf

[Katie Reynolds]

I personally like english better, just because I find it easier to deal with. Yeah, I know metric is based off of 10, but I like english ::shrugs:: I never used metric until I got into FIRST.

My suggestion? Get both. Our toolbox consists of both, just in case we need them. Like this year, we used Bosch as our frame (which is metric) and everything else was english. Yikes.

- Katie

[Joe Lambie]

I have been a part of FIRST for four years now and have dealt with both ends of the stick on this. Last year as Katie mentioned we had both on our robot. Now, I will say that inches can almost be easier to deal with cuz then when you have drawings of parts they most likely will all be in inches in the format of 1.125 or 1.274 or some thousandths of an inch format, no converting between cm and mm and what not, but I have also grown up on inches now. Just my thoughts, take it easy all.

[Neal Probert]

The Mars Climate Orbiter crashed over this very confusion, instead of going into orbit as planned.

NASA, which has done everything in metric for quite some while now, had programmed the space craft to operate in metric units. Somehow, the bonehead engineers did their math in english.

The result was $125 million down the drain.
Btw, this wasn't the first time something like this happened.

Missing punctuation (period instead of a comma) in Fortran code caused on spacecraft to get lost.

The following forum at http://catless.ncl.ac.uk/Risks details lots of cases like this. Good reading.

Not that a FIRST bot would get lost in space, but it might crash and burn. Anybody got good stories where programming errors did really strange things to your bots?

[Wetzel]

Originally posted by Neal Probert
The Mars Climate Orbiter crashed over this very confusion, instead of going into orbit as planned.

Guess you missed Dave's post about that....

And yes, it was Dave's fault.


Wetzel
~~~~~~~~~~~~~
No longer on 116, Dave can't get me.
"/me exhibits shifty eyes"
~Jim

[Ian Mackenzie]

I'm currently in limbo between my high school team and a team to help out with during university, but in the meantime I'm keeping myself busy designing a transmission. I initially tried designing in imperial (since that what's what I was used to through FIRST), but after not too long I gave up in frustration and switched to metric. I had to recreate the whole thing, but I thought it was definitely worth it. Almost every single dimension is an integer, and typing dimensions is a lot easier - 5 millimetres instead of 3/16 or 0.1875 inches. Now if only I could figure out why Pro/ENGINEER thinks the default metric unit of mass should be the tonne...

[dlavery]

Originally posted by Wetzel
Guess you missed Dave's post about that....

And yes, it was Dave's fault.

Yeah, I know, it is always my fault - just ask anyone on 116!

-dave

p.s. Even though Wetzel makes me take the blame, the reality is that it wasn't exactly a NASA "bonehead engineer" that made the mistake. A very young engineer, working for the contractor that actually built the spacecraft, was relatively new to the job and had not been fully trained on "how the system worked." His job was to calculate very small propulsion forces used to make minute corrections in the spacecraft navigation system. The other projects he had worked on used English units for their calculations (as required by those other contracts). But he did not know that all NASA contracts specify the use of Metric units for all force (and other) calculations.

The forces he calculated were sent to JPL and then uplinked to the spacecraft. The rest is history. The simple-minded answer is to say that the engineer made a mistake that caused the loss of the spacecraft. A more insightful analysis leads to the understanding that the real problem is that the system was set up with insufficient review and validation of the navigation calculations being performed, and that insufficient checks and balances allowed a small mistake to make it's way all the way through to the spacecraft without being caught. The lesson learned is that systems and procedures need to be designed in anticipation of people making "human mistakes" and be robust enough to recognize and correct them.

[Mark Hamilton]

Adjustable wrenches are a bad idea imho. They strip bolts very easily. It is best to standardize on a few bolt sizes and avoid them all togethor. We use Imperial measurements with a little bit of metric mixed in. The reason we use Imperial is because most materials are in that system, making it easier to work with. Its pretty rare to have to do unit conversion on the robot anyway. Foot to Inches is pretty easy, and thats the only I can think of you might need. When you get into volume measurements is when the Imperial system falls flat.

[ajlapp]

we use 10/24 hardware almost exclusively. we never go smaller unless a specific design calls for it.......and we almost always use 3/8" shafts for our drive systems. 90% of our 2002 robot could be disassembled with about five tools total. we have also taken care to standardize our design process. all parts are finalized by the same group of people who try to design each part in a similar fashion with hardware in mind.


Anthony
team 221-->857
superior roboworks