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Author Topic: DremelFuge
GrumpySteen

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Icon 1 posted May 04, 2011 09:47      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
I thought this was neat enough to share:
DremelFuge

"DremelFuge is a printable rotor for centrifuging standard microcentrifuge tubes and miniprep columns"

It requires a 3D printer to make, of course, but still... neat!

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dragonman97

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Icon 1 posted May 04, 2011 16:31      Profile for dragonman97   Author's Homepage     Send New Private Message       Edit/Delete Post   Reply With Quote 
Very cool!

Horrible quality video, but amazing use of 'everyday' tech. [Big Grin]
(MakerBots aren't actually /that/ hard to come by - if you're lucky, you may be able to get use of one in a nearby hacker lab/thing. Or build one for about a grand.)

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Ashitaka

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Icon 1 posted May 04, 2011 18:04      Profile for Ashitaka     Send New Private Message       Edit/Delete Post   Reply With Quote 
as somone who oftn uses centrifuegs for prep work I can see dozens of problems with this.

a) It is not safe, cetrifuges have a cover that automatically stops the machine when opened for a reason, or the cover is locked when the machine spins.
b)It requires a drill, how do you mount the drill.
c) it probalby takes up more lab space then the cetrifuge it would replace
d) it is not cooled, big cetrifuges must be cooled or you sample will heat up too much.
e)It is unlikely cheaper, most labs don't have an unused drill lying around, a cntrifuge that this would replace is not really that expensive.
f) what happens to the drill with an unbalanced load.

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TheMoMan
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Icon 1 posted May 04, 2011 23:00      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
That thing is neat, as are explosions.

I have to agree with Ash. that is an accident waiting to happen.

Enter dim bulb cellar dweller that makes one out of low tensile strength nylon. Winds it up and shoots out the tubes as missiles. You guys need to look up "Punpkin-Chunkin" especially the centrifugals.

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Benjamin Franklin,

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Grummash

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Icon 1 posted May 05, 2011 00:09      Profile for Grummash     Send New Private Message       Edit/Delete Post   Reply With Quote 
C'mon gents - give DremelFuge guy a break (insert 'bad pun' groan here).

I don't think he is quite as reckless as you suggest - after all, he was holding it a saucepan in case it shattered [crazy]

But seriously, he has tested it with a working load to 33,000rpm (over 50 thousand Gs) without a catastrophic failure and suggests that using it at 16,000rpm will match the G forces of a commercial centrifuge. That seems like a reasonable level of headroom to me.

I don't think there is too much of a concern about "drills with uneven loads" in this scenario. Dremels are used just as much for sanding/grinding/cutting as they are for drilling and should be able to cope with the modest off-axis forces that might arise from varying density of nylon in the 'printed' DremelFuge. The DremelFuge itself may be less able to cope with manufacturing flaws, but everything that we make is vulnerable to manufacturing flaws to some degree. The biggest risk in this area is probably poorly prepared samples, which would be the fault of neither the DremelFuge nor the DremelFuge designer.

Ash's points about guards and emergency stops are, of course, perfectly valid, but these would not necessarily keep TheMoMan's 'dim-bulb cellar-dweller' safe and sound. Safety devices enhance responsible usage but are easily circumvented by wilful abuse. Dim-bulb cellar-dwellers are solely responsible for any risks they take.

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TheMoMan
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Icon 1 posted May 05, 2011 00:38      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
Grummash, I wish to relate a centrifugal launch. Enter Die-Room Bob the most dangerous Diemaker where I worked. He was drilling Bolt holes in a Big Die-Ring Think huge piston ring, about 200Lbs. He did not use tie-downs, safety straps or any thing to contain the ring. As the drill broke through the steel it grabbed and yanked the ring out of his left hand. He then let go of the quill lever and let the drill lift, he still had his foot on the power switch. I was setting on a stool with my back towards this mayham. The Drill broke, throwing the now rotating Die-Ring through the tool-room taking out the stool I had just hurriedly vacated. Total flight 40feet. Large mass rotating slow or small mass rotating very fast may have the same amount energy.

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Benjamin Franklin,

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The Famous Druid

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Icon 1 posted May 05, 2011 09:31      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
A place I worked in back in the age of steam-powered computers had a room full of these...

 -

That's **20 Megabytes** of storage there, in a package no bigger than a household washing machine. We had a couple of hundred of them.

They were dinosaurs, even then, but needed for a legacy system.

One day we had a head crash, some glitch caused the read/write head to come into contact with the spinning disk surface, and the head shot through the plastic enclosure, through the wall of the computer room, and embedded itself in the far wall of the corridor outside.

It taught me to respect rapidly spinning machines.

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Grummash

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Icon 1 posted May 05, 2011 12:45      Profile for Grummash     Send New Private Message       Edit/Delete Post   Reply With Quote 
We all have our horror stories...and whilst they are all valid and relevant, they shouldn't be allowed to stifle innovation, but rather "guide and inform" it.

My story goes back to engineering college in the late 1980s, where the main workshop was furnished with pre-WWII tooling (Sir John Mills has been seen in films flying Spitfires whose propeller cones were fabricated on the same Churchill lathes and milling machines that we had in our workshop).

Anyways, we had a grinding machine with a 6-foot diameter wheel (probably 4 inches thick)... I can't remember the operating RPM, but I do remember that that the peripheral velocity was said to be well in excess of 300mph, and I remember the fist-sized gouges in the "blue engineering brick" wall 15 feet away, resulting from the only time someone had burst the wheel. We were told about this in our first lesson...

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HalfVast

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Icon 1 posted May 05, 2011 14:45      Profile for HalfVast     Send New Private Message       Edit/Delete Post   Reply With Quote 
Completely sideways from the topic (hey, it's me...)
I read the title but thought Dremel Fugue. I imagined
a setup of differing sizes of Dremel tools attached
to different resonant surfaces and controlled with
a microprocessor to start, stop and run at diferent
speeds to make music! What can I say, I love
my variable speed rotary tools. [Razz]

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GrumpySteen

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Icon 1 posted May 06, 2011 01:32      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
Diameter of the DremelFuge: 6.4 cm
Circumference: ~20 cm
Radial speed @ 30,000 RPM: 10 m/s

I couldn't find the weight of a 2 ml centrifuge tube, so we'll use something ridiculous and say 10 grams for the tube and contents.

10 grams @ 10 m/s = .5 joules

For comparison, getting shot with a BB gun will deliver about 1 joule to a far more concentrated area of your derrière.

Now let's get silly... assume the entire DremelFuge was a solid block of nylon (the crappiest, most likely to break material used by 3D printers). It would weigh around 157 grams. We'll assume it's going 30,000 RPM and it somehow breaks free as one chunk and assumes the velocity of a point on it's circumference (I did say silly)... the total energy would still be less than 8 joules.

Stop freaking out. Yes, if you get hit in the eye, it would hurt. Otherwise, it's not going to kill you and it's certainly not going to blast through the top of a pressure cooker (what the guy was holding in the video) or take chunks out of a concrete wall.

Didn't any of you ever climb a tree as a kid? Or did you all stand on the ground, terrified that you might fall out and break an arm.

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TheMoMan
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Icon 1 posted May 06, 2011 02:34      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
I have a Chicago Pneumatics Die grinder, CP7556 rated for 30Krpm. I only buy wheels rated for 50Krpm. They will still explode. Yes safety glasses and face mask are recommended, I have been cut by flying debris. I attempt to keep all of my body parts out of the plane of rotation.

I have never found a 50K wheel bigger than 2.5"Dia. might there be a reason?

http://www.boschtools.com/Products/Accessories/Pages/BoschAccessoryDetail.aspx?pid=148

These do hold up well.

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Benjamin Franklin,

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Xanthine

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Icon 1 posted May 06, 2011 06:45      Profile for Xanthine     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by GrumpySteen:
Diameter of the DremelFuge: 6.4 cm
Circumference: ~20 cm
Radial speed @ 30,000 RPM: 10 m/s

I couldn't find the weight of a 2 ml centrifuge tube, so we'll use something ridiculous and say 10 grams for the tube and contents.

10 grams @ 10 m/s = .5 joules

For comparison, getting shot with a BB gun will deliver about 1 joule to a far more concentrated area of your derrière.

Now let's get silly... assume the entire DremelFuge was a solid block of nylon (the crappiest, most likely to break material used by 3D printers). It would weigh around 157 grams. We'll assume it's going 30,000 RPM and it somehow breaks free as one chunk and assumes the velocity of a point on it's circumference (I did say silly)... the total energy would still be less than 8 joules.

Stop freaking out. Yes, if you get hit in the eye, it would hurt. Otherwise, it's not going to kill you and it's certainly not going to blast through the top of a pressure cooker (what the guy was holding in the video) or take chunks out of a concrete wall.

Didn't any of you ever climb a tree as a kid? Or did you all stand on the ground, terrified that you might fall out and break an arm.


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GrumpySteen

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Icon 1 posted May 06, 2011 07:25      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
Xanthine:
You fall off mountains and stuff. I wasn't including you in the "Didn't any of you climb trees" question [Smile]

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Xanthine

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Icon 1 posted May 06, 2011 07:27      Profile for Xanthine     Send New Private Message       Edit/Delete Post   Reply With Quote 
That previous post was a screw up. What I meant to say follows...

Not all materials can handle the g's a centrifuge going 33000 rpm can pull. And once the rotor breaks... Even if you don't get hurt, you've lost your sample, lost your toy, and you have a mess to clean up. I've honestly never seen a plastic rotor on anything but the little benchtop spinners and those only get fast enough to spin stuff down to the bottom of the tube - no one actually uses them for anything serious. But that doesn't mean you can't machine some hefty parts out of a bad-ass polymer, so long as it's the right polymer. We have Teflon crap all over my current lab because it's robust and doesn't get eaten by some of our more fun chemicals.

Oh yeah, and the big rotor on the big 4 degree floor centrifuge in my former lab was partially carbon fiber. But that rotor wasn't rated to spin faster than about 10K and we never actually ran it faster than 4K because we ran the risk of damaging cells and, just as distressingly, crushing the tubes.

quote:
Originally posted by GrumpySteen:

I couldn't find the weight of a 2 ml centrifuge tube, so we'll use something ridiculous and say 10 grams for the tube and contents.

A typical 1.5 mL eppie is about 1 g and really holds closer to 1.7 mL. A 2 mL is 1.2 g and really holds closer to 2.2 mL. I have no idea how much a miniprep column weighs but I'm guessing it's a little more than a 2 mL eppie when combined with a collection tube and the max volume for that is 700. Given that the contents of the tubes is usually primarily water, I think you can take a guess at how much a loaded tube would weigh.

That said, the real concern about spinning a tube really really fast isn't what happens if it flies but what happens if it falls apart. These things can't handle more than 25K g's; run them any faster and they crush. The people doing ultracentrifugation have to buy special plastic wear for that.

I wonder what sort of disaster an unbalanced DremelFuge would create. The boxy centrifuges at work wobble and walk and then, if it's going really fast, the rotor might go flying out of the casing. But a Dremel...if you're holding it it'd probably go flying out of your hand while still operating and if it's mounted it'd probably try ripping itself off the mount. And I doubt that thing has all the springs most lab 'fuges do to correct for careless labrats. Balance your tubes people!

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TheMoMan
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Icon 1 posted May 06, 2011 07:52      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
If we decide that a sample tube weighs 3gms and is wound up to 22Krpm. If the tube were to come out of the holder: It would would be 1/13the the weight of a 45Cal. slug going half as fast. The shape might allow it to penetrate flesh.

Nope trees were too scary I preferred to stand on the skids of Hueys while flying to and from pick-ups.

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Benjamin Franklin,

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GrumpySteen

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Icon 1 posted May 09, 2011 03:57      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
If the tube were to come out of the holder: It would would be 1/13the the weight of a 45Cal. slug going half as fast

No.

Look at the math that I did above. See the 10 meters per second speed? If you aren't comfortable with metric, that's about 33 fps or about 22.5 mph.

You should have a sneaking suspicion that your math is way off at this point.

Most .45 caliber loads will, in fact, exit the barrel going over 240 mps (over 800 fps or 545 mph for the non-metric). Here's a reference for proof, if you feel the need to look.

10 is not half of 240. 33 is not half of 800.

And let's not even get into the difference in being hit with a piece of flexible plastic that won't shatter vs. being hit with a bullet that's designed to fragment and cause maximum damage on impact.

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TheMoMan
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Icon 1 posted May 09, 2011 07:44      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
30KRpm/60secs= 500 RPS

Outer diameter is where surface/tangent velocity is measured.

So hub and tubes will be near 6" dia.

.5' * 3.14159 * 500 = Fps

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Benjamin Franklin,

Posts: 5848 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
GrumpySteen

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Icon 1 posted May 09, 2011 10:45      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
TheMoMan:
Outer diameter is where surface/tangent velocity is measured.

Absolutely wrong.

The center of mass of the tube is where you should measure the velocity since that is the velocity that the the tube will assume if it breaks free.

And you missed a -lot- of details.

 -

1.1 cm more of the tube extends beyond the rim of the DremelFuge than is inside the Dremelfuge, but the end is tapered and will hold less and weigh less than an equal length of the main body of the tube.

While the tapering probably doesn't perfectly balance out the longer length of the tubing that extends past the DremelFuge's radius, it's probably close enough to make the difference in energy negligible.

Would you like to make any more assumptions about things I must have overlooked?

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TheMoMan
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Icon 1 posted May 09, 2011 11:30      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
Go ahead build it wind it up with out a guard!!

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Benjamin Franklin,

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The Famous Druid

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Icon 1 posted May 09, 2011 16:41      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by GrumpySteen:
Look at the math that I did above. See the 10 meters per second speed? If you aren't comfortable with metric, that's about 33 fps or about 22.5 mph.

You should have a sneaking suspicion that your math is way off at this point.

Actually, I have a sneaking suspicion that you've misplaced a decimal place...

quote:
Diameter of the DremelFuge: 6.4 cm
Circumference: ~20 cm
Radial speed @ 30,000 RPM: 10 m/s

Looks like 100 m/s to me. (500 revs/sec * 1/5 metre per rev)

Unless you're assuming the centre of mass is 90% of the way towards the hub, which seems unlikely.

Which gets me thinking...

Imagine the payload in the spinning dremelfuge is suddenly released...

The law of Conservation of Momentum says it will travel at the average velocity of the mass, which will be the velocity of the centre of mass, in this case about 1/2 of the rim velocity.

The law of Conservation of Energy says that kinetic energy is also conserved, but kinetic energy is proportional to v squared, so the 'centre of kinetic energy' (did I just invent a new technical term?) will be closer to the rim than the centre of mass.

Does anyone know how these two reconcile?

[edit] Just realised the answer to my own question: The loose payload will be spinning, so my rough assumptions about the momentum and kinetic energy are inadequate. You'd have to include the angular momentum and kinetic energy of the spin as well as the net velocity of the centre of mass. CBA doing the maths but I expect they'll balance.

Damn. Disproving one of those laws would have been cool. There goes my Nobel Prize for Physics.

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GrumpySteen

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Icon 1 posted May 09, 2011 18:29      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
TheMoMan wrote:
Go ahead build it wind it up with out a guard!!

And you can go ahead and keep making asinine assumptions about what I would or wouldn't do. In fact, just go ahead and assume I'll stick the thing in my mouth and turn it on full speed. It's as realistic as your other assumptions about me.

The Famous Druid wrote:
Actually, I have a sneaking suspicion that you've misplaced a decimal place...

I did. My original calculation was off by a factor of 10. U. caught it first and I thought about changing it, but I wondered how long it would be before anyone noticed. Since I'd also used 10 grams for the tube weight when it should have been closer to 3, the numbers were wildly off anyway.

The actual energy should be around 1.5 joules (10x the energy due to speed * 1/3 due to the overestimate of weight=3.33...) or about 1.5x what a BB would deliver. That energy would, however, be delivered to a larger surface area by a more elastic material, reducing the impact damage significantly.

The law of Conservation of Momentum says it will travel at the average velocity of the mass, which will be the velocity of the centre of mass, in this case about 1/2 of the rim velocity.

From what I can tell, the center of mass for the tube should be close to the rim of the DremelFuge (hereafter called "holder" because I'm tired of that name). That would give the tube an average velocity that would match that spot. Unless maybe you mean the tip of the tube as the rim? The radial speed there should be about 1.76x the speed at the rim of the holder.

The loose payload will be spinning, so my rough assumptions about the momentum and kinetic energy are inadequate.

I considered spin, but I reasoned that a non-spinning bullet-ish shaped mass that shot straight forward (which is impossible because the tube would never break free cleanly and would always gain some spin). would have less loss of energy due to air friction and the smallest possible impact area for the object's shape. That would allow it to deliver the most damaging impact... i.e. a worse-than-worst case scenario. Since the goal was to get an idea of how much damage it would do, using the worse-than-worst case scenario seemed like an acceptable compromise in exchange for simplifying the mathematics.

And for bonus points, I looked up the density of bananas (1.15 g/cm^3), banana oil (.88 g/cm^3) and percentage of water in bananas (75%) and spent a few minutes trying to figure out what effect centrifuging would have on the distribution of weight in banana mush. I couldn't find numbers for the percentages of banana oil and solids in the banana (though together they must be about 25%, obviously), so I couldn't actually figure that part out and gave up.

Note: all banana numbers are from memory and may not be correct since it's been a while since I looked.

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The Famous Druid

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Icon 1 posted May 09, 2011 22:03      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by GrumpySteen:
The actual energy should be around 15 Joules (100x the energy due to (speed^2) * 1/3 due to the overestimate of weight=3.33...)

FTFY.

quote:
See the 100 meters per second speed? If you aren't comfortable with metric, that's about 330 fps or about 225 mph.

Most .45 caliber loads will, in fact, exit the barrel going over 240 mps (over 800 fps or 545 mph for the non-metric).


100 is 'about' half of 240. 330 is 'about' half of 800.

FTFY.

Now, where's that Cosmic Bong...?

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GrumpySteen

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Icon 1 posted May 09, 2011 23:11      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
So when a shop offers a $240 item for half off, you can pay them $100 because it's almost half off. 20% error is nothing.

And 800 is way below the average speed (1122 fps) of a .45 caliber bullet. It's one more intentionally fudged worse-than-worst number I used to make the comparison fair. So 330 is "about" half off 1122. 42% is nothing (oh look... it's "about" half off).

And an impact by a feather going at 100 mph is virtually identical impact of a brick going at 100 mph, so straight velocity is the ideal way to estimate impact results.

And we've all been extremely accurate because the fact that we're missing a lot of critical data is irrelevant.

Yeah... no to every bit of that.

But hey, I have DremelFuges to stick in my mouth because I don't know what the fuck I'm doing, so I don't have time to continue this post. See y'all when I've demonstrated how safe it is to lick moving equipment and electrical wiring. Durr.

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The Famous Druid

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Icon 1 posted May 10, 2011 01:05      Profile for The Famous Druid     Send New Private Message       Edit/Delete Post   Reply With Quote 
quote:
Originally posted by GrumpySteen:
So when a shop offers a $240 item for half off, you can pay them $100 because it's almost half off. 20% error is nothing.

Ok, so TheMoMan was off by 17% in his 'half the speed' comment.

That's within 'near enough' range for a casual discussion, and 'about half' of your 90% error.

Now where's that Cosmic Bong got to...?

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If you watch 'The History Of NASA' backwards, it's about a space agency that has no manned spaceflight capability, then does low-orbit flights, then lands on the Moon.

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TheMoMan
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Icon 1 posted May 10, 2011 04:37      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
http://www.youtube.com/watch?v=bFQNBudpST4

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Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

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