Agreed... Useless info but... a 400 lb. Rubber band ball dropped from an
airplane reached over 500 MPH and the free-fall skydivers could not keep up
with it. I'm guessing that a much more dense item like the bilalrs ball
with a smooth surface would best that number by quite a bit... Which makes
*my* story look even more like I made it up.
Got me scratching my head here wondering how we did it...
Terminal velocity for a billiard ball should be about 43.5 m/s,
or 97.4 mph. The drag coefficient for a smooth sphere is C = 0.5.
Some info on terminal velocity with examples:
A page with a calculation app. that you can see the results
of a vertical shot for a spherical object like a billiard
The radius of a standard billiard ball is about 2.857 cm,
density about 1637 kg/m^3 (1.637 gm/cm^2). Mass about
Good thinking - just as with routing and milling, depth of cut per pass,
adequate airflow, and a suitable feed speed are important factors for
controlling heat build-up. In the case of laser cutters, I think
additional control can be exercised by controlling pulse frequency
It's because I'm so lazy and such a cheapskate. I's a fatal combination.
If the approach could be made to work (depends heavily on collimation of
the laser beam), it'd only be necessary to drop the log on the cradles
with a fork lift, locate the height of the center of the log, specify
the diameter, and stand back. There'd be a minimum of mechanical stuff
to maintain, and no expensive bits to sharpen or replace (or stock in
different sizes). I'm guessing that power consumption would at least not
be worse than a traditional boring machine.
Probably, smoke should be considered a solved problem - and shouldn't be
more complex than ventilating a spray booth. Setting up guards,
interlocks, and shields for safety should be straightforward.
I don't know what kind of beam collimation is current state of the art,
but I'd guess that seven or eight feet should be workable.
I didn't see this until Morris had already made the suggestion, but that
was my first reaction as well.
As for the safety issues, those could be pretty easily taken care of w/
appropriate fixtures I would think. If they're doing this extensively,
a little extra for the fixture shouldn't be any drawback.
At former employer in a previous life :) we begin using laser
penetration/welding in pressurizing nuclear fuel rods w/ inert gas
during the manufacturing process "way back" in the late-70s. Laser
focussed to make a pinhole in fuel rod end cap, evacuated and then
filled w/ argon; laser defocussed and welded shut the hole. Same thing;
a fixture and interlocks prevented any way of getting the laser
activated w/o the required shielding in place.
I would thing there could be a heat removal issue in such a thick
enclosed piece, but where there's a will there's a way.
The description of a current tool that reaches (apparently) the full
length and leaves the core is leaving me w/ the desire to see that
Joe, have him look at Vermeer's moles. He won't need anything that
serious, but the parts and drives are there. Horizontal boring is one
of their specialties. They bored a hole from the church parking lot on
my street, past my house and down the street a total of 1300 feet,
deep roots, rocks, all kinds of stuff and ended up exactly where they
wanted. I can't imagine they wouldn't be able to help him.
Sounds like a job for Technidrill http://www.technidrillsystems.com/
or one of their competitors.
Google "gun drill" and you should be able to come up with more hits.
A call to the appropriate division of BAE Systems might also yield the
name of their tooling supplier (or might not depending on how close to
the vest they like to keep their manufacturing).
National carbon used a "gun lathe" to machine 6" dia thru holes in 20
ft long graphite logs for the nuclear industry.
They found both the lathe and a milling machine at an old armory
auction as I remember it. (This was 1960 era).
No leads,but it seems like having the cylinder left behind would be a
benefit -- the remaining cylinder could either be drilled to a smaller
diameter, or used in some other way. Seems like a drill that operated in
the typical manner would generate a lot of waste needlessly.
If you're going to be dumb, you better be tough
Depends on how many they need to do, how much they are willing to
spend and how hard they are willing to work, doesn't it?
Two hundred years ago, this was done by hand. Logs were bored out and
used underground in municipal water systems. I recall reading a few
years ago that there were some still in use, but that may not be so.
If you look for "pump auger" or "pipe log auger" you may find some of
the antiques that were used. According to Mercer, it took two men
about a day to bore 16 foot white oak logs in 1926.
Could you drive it by power instead? Certainly - perhaps a post hole
auger or a pipe threader. Check rec.crafts.metalworking and you'll
see that oldjag just successfully used a pipe machine to bore through
20 feet of earth with a 2 inch pipe.
For a machine made for doing exactly this kind of work, albeit in
metal, look for a horizontal boring mill. Lots of them available at
auction, and an old clapped-out machine would still be much more
accurate and powerful than they would need. They could probably find
one for little more than scrap price, although you're probably looking
at 10 tons at the least.
Coring the log sounds nice, but I wouldn't insist on it. Coring
doesn't leave much room for chips, and there will be a lot of them.
Also, the core will contain the pith of the log, so it won't be much
use as is. The guys doing it by hand bored a small (2 inch ?) hole
which they then enlarged with reamers, which seems like a good method.
On Tue, 5 Aug 2008 09:39:24 -0400, "Joe AutoDrill"
I don't know what the application is but wouldn't it be easier to rip
it on a bandsaw mill, core box bit the insides and glue it back
Thos. J. Watson - Cabinetmaker
That is what we said... But I guess they need it in one piece for some
reason. All I could picture was high end sail masts for sailboats with an
aluminum mast hidden inside... And customers who were too picky to accept a
"split down the middle" wood look...
...But God only knows what they will actually be using the wood "tubes" for
after they are done...
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