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Vans engineers having a laugh
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Little Mark
I had a guy working for me and his nick name was "Little Mark." I asked him what was the source of the nick name and he said: Right out of high school the foreman sent me to go take a measurement, I climbed up the latter and called out - 121 inches ...... and 9 little marks. :p
So I call the Van's CAD guy: Little Mark. I see the crazy tolerance markings all over the plans, but they are fun to try to and achieve. :D So how do you mark 1/64"? Mid point between the 1/32 marks. |
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Of course I've tried marking with a Sharpie, then lightly scribing the precise location on the part. Then center-punch -- oops, it's about 1/64th off -- drill -- dang it!! Drill press wandered off another 1/32 in the other direction... and it ends up "in the vicinity". I eventually learned to offset the work in the drill press to keep that part to a minimum. |
I get the same thing at work. I submit drawings to the shop with 1/64" tolerances, I go out on the floor and watch them measure it to 1/16", mark it with chalk to 1/8", and then cut it with a torch that has 1/4" kerf.
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Yes, the per each hole placement accuracy isn't to 1/32 of an inch, but if there are 32 holes along that edge, they do need to be roughly spaced at 1 and 1/32 because by the time you get to the end of that row of holes, 32 holes add up to an additional 1 inch, so if you spaced them at 1 inch you'd have a 1 inch gap left at the end of the row. I think that is the reason for the 1 and 1/32 call out.
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How many beer did he have when he was making this video?
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Engineers
Not calling anyone out here. Engineers are engineers - they deal with 1/000s of an inch sometimes (like when they send instructions to the machines that 'punch' out the critical pieces of our kits. Its a mind set. They are taught to be as accurate as possible. I like that.
I strive, like most, to be accurate but when I fail, I don't worry about it if I'm off by 1/64 or 1/32 if the part dimension is not critical. It the measurement is critical, its time to purchase a replacement part and get it right with the next new part. I've known a few engineers and almost without exception, the ones who have spent some time building what they have drawn out have respect for those of us who are building what they have specked out. The ones who bug me are the ones who have no respect for us who build their projects. I think that most or all of Van's engineers respect us builders and try to spec out the measurements as accurately as possible. I like that too. |
The dimension on the drawing has to be something. 1" or 1 1/32" what's the difference, you still need to use a scale and measure it to 1/32" accuracy. I found it to be no additional work to measure and mark to 1/32. As mentioned in a previous post, The tolerance stack up starts with the measurement, gets worse with the mark, center punch, and drilling. Minimize error at each step and you will be amazed at how much better it fits together. Be off high at each step and you will be short ED.
And yes, I am a aerospace design engineer. |
Not an engineer of this type but I would imagine that they use CAD and have the program space the rivet holes appropriately and these measurements is what the program will come up with. Nothing wrong with providing a more accurate measurement and let people do to their best of their ability to adhere to it. Besides, if you have 32 of these rivets in a row and rounded off by 1/32, now you have put one less rivet.
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We have to thank modern technology, modern practises and a little bit of irony in this.
Now, as a Brit, we understand irony, not usually an understood thing in the Colonies.... But. There is an interloper. There is a Brit in Vans and we think, possibly, that his wit and wisdom is seeping into the very fabric of the organisation. Why would you see an instruction in the 12 plans to use a 'metric crescent wrench' to - err facilitate the longerons ? Come on chaps (and chappesses), the Engineers are playing with us. They must sit with their Pabst beers, maybe Milwaukee, will will defer, and say - hey, how can we p1ss these guys off with using such tiny, weenie measurements as to sent them insane ? It is Engineer amusement. Let us all laugh collectively, let us all raise a glass of weak, domestic lager to them and say - thanks guys, thanks for making the best designed, the best supported and the best flying Experimental airplanes on the market today. Rejoice, do not criticise.......:D:D:D:D |
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