Team Update 5

[writchie]

Originally Posted by MikeDubreuil

With that said, I do believe the GDC reserves the right to change the game at any time. We could have a new game piece in the next team update

Ah!. I missed that. (It's not in the spec - it's in the contract - I knew we needed a lawyer on the team). Now we have a good engineering lesson. Look for the fine print. When the customer has some fine print that says something like "the government reserves the right at any time to change the specifications ....." beware. You may have to anticipate such changes and their possible consequences (and build that possibility into your price ).

Fortunately, we had a Plan B contingency for the case where the idea didn't work. The idea worked but the specs have changed so Plan B will now come in handy.

[Taylor]

Originally Posted by writchie

Fortunately, we had a Plan B contingency for the case where the idea didn't work. The idea worked but the specs have changed so Plan B will now come in handy.

Remember to put a diaper on your helper monkey.

[JesseK]

Imagine what happens to the trailer, practically speaking, when it starts whipping around the back of the robot. The trailer will want to tip left/right (aka roll) when it changes lateral directions. This puts extreme forces on the contact point of the trailer tongue and the robot hitch. Enlarging the hole at the contact point allows for the trailer to roll and tip slightly without damaging the trailer tongue or the hitch. I for one am very glad of this change as it reduces the torsional reinforcement our hitch mount needs since our drive train is designed to strafe and drift. Part of engineering is to at least have considered the realm of implications and possibilities of a particular design before going forward. It's impossible to figure them all out, which is why engineers usually create room for error in their designs.

Why do people consistently post that they think the GDC is out to get them when they clarify the rules?

[writchie]

Originally Posted by JesseK

Imagine what happens to the trailer, practically speaking, when it starts whipping around the back of the robot. The trailer will want to tip left/right (aka roll) when it changes lateral directions. This puts extreme forces on the contact point of the trailer tongue and the robot hitch. Enlarging the hole at the contact point allows for the trailer to roll and tip slightly without damaging the trailer tongue or the hitch. I for one am very glad of this change as it reduces the torsional reinforcement our hitch mount needs since our drive train is designed to strafe and drift. Part of engineering is to at least have considered the realm of implications and possibilities of a particular design before going forward. It's impossible to figure them all out, which is why engineers usually create room for error in their designs.

1. The original hitch design (Prior to REV A) allowed the trailer to roll freely. REV A (before the kickoff) added a close fit pin which eliminated this roll.

2. If the GDC wanted to allow limited roll, it could have modified the hole added by REV A. This would not have affected pitch.

3. REV B now allows about plus or minus 10 degrees of roll and pitch. Under some pitch loads, it also allows the 1018 steel cylinder to be levered against the aluminum C channel.

4. I'm glad that you think this change benefits your design. When the design of a component changes there are usually some that benefit, some that are harmed, some for which the change is irrelevant, and some who remain in ignorant bliss.

Originally Posted by JesseK

Why do people consistently post that they think the GDC is out to get them when they clarify the rules?

I don't know. But what does that have to do with this discussion? We certainly don't think the GDC is out to get us. And this certainly isn't a clarification! But the fact is that the design of a major component has been changed in a significant way and we still think that such spec changes should at least be accompanied by an explanation.

It may be that this is new territory for the GDC with a major component of the robot supplied as part of the field. This introduces a new element to the engineering - mating with an externally specified and supplied component. I think that this is a good thing that opens up new opportunities. But I think that specs for a component of the robot system and a the specs for game piece are of a different character. If the intent is for the piece to be an integral part of the robot on the floor, then the specs should be frozen at kickoff and not changed without both good reason and cogent explanation.

Just my $0.02

[writchie]

Picture of side by side Hitch, Swivel Rev A and Rev B

[Rick Wagner]

Originally Posted by writchie

Picture of side by side Hitch, Swivel Rev A and Rev B

http://www.chiefdelphi.com/forums/at...5&d=1232678195

The link is not working for me.

[rwood359]

Where do you find the updated GE drawings?
All I can find on the FIRST site is 9036A and 9040.

[writchie]

Originally Posted by rwood359

Where do you find the updated GE drawings?
All I can find on the FIRST site is 9036A and 9040.

They are in the latest 2009 Game Specific Drawings.zip file.

Should be here http://www.usfirst.org/uploadedFiles...20Drawings.zip

[rwood359]

Originally Posted by writchie

They are in the latest 2009 Game Specific Drawings.zip file.

Should be here http://www.usfirst.org/uploadedFiles...20Drawings.zip

That zip file has 9036a and 9040. Not 9036B and 9040A, that's why I'm confused. The updated drawings have the old revs.

[writchie]

Originally Posted by rwood359

That zip file has 9036a and 9040. Not 9036B and 9040A, that's why I'm confused. The updated drawings have the old revs.

Hmm. I just loaded from the link and it has GE-09036_revB.

I believe the file name hasn't changed so you may have a browser cache issue. Make sure you refresh the page. Then try a save link as and specify a different name and see if that works.

[rwood359]

Originally Posted by writchie

Hmm. I just loaded from the link and it has GE-09036_revB.

I believe the file name hasn't changed so you may have a browser cache issue. Make sure you refresh the page. Then try a save link as and specify a different name and see if that works.

Thanks, it was some sort of cache problem. Saving the link got the current file.

[JesseK]

Originally Posted by writchie

... not changed without both good reason and cogent explanation.

Heh, you're right, we win some, we lose some. I truly believe this update was to prevent trailer damage, which is part of the field as you stated. Damage prevention techniques are stated and implied in several spots of the manual (since Day 1) and on the Q&A.

Don't get me wrong though; I'm all for milling a 1/4" slot to allow for roll, which would prohibit pitch. I suppose we can call the GDC lazy for going with the simple method of drilling a bigger hole.

[rwood359]

Originally Posted by writchie

Hitch Model showing Rev A and Rev B
http://www.chiefdelphi.com/forums/at...5&d=1232678195

Comes up as invalid attachment.