I am trying to help a math teacher spruce up a barren basement classroom
that currently looks like a prison cell.
I gave her an 18-inch WiFi antenna for her to put posters on saying it's a
parabola and showing the focal point.
But I want to find a conic section that shows that when you slice a conic,
you get circles, elipses, and hyperbolas.
If I were a great woodworker, I would just make one.
But I'm not that good and I don't have a lathe.
All I have is a circular chop saw.
Do you know of an easy way to make or buy conic sections (wood or plastic)?
On Sat, 20 Aug 2016 13:54:09 -0400, Retired wrote:
That is good for the math class.
At $30, it's best for the teacher to expense it.
So I'll see if they'll let her do that.
She's new to teaching and is shy and far too timid (IMHO), since this is a
good request, I think, for a math teacher.
I'm just trying to help her out.
Somebody (actually, I gargled and found quite a number) has already beat
you to it...
Now, what they're asking for them may not fit the budget...
I was hoping to figure out a cheap way to just give them to her, but the
ones you showed at that site were gorgeous!
At $100 each, they're a bit pricey for *me* to spend just to help someone
out, and maybe she'd even have a problem expensing them at a public school,
but they *are* perfect (and gorgeous!) and made out of wood, which is
If I had a lathe, I'd just take a light colored wood and a dark colored
wood and make two single-napped cones.
Then I'd slice each cone four ways with a thin jig saw blade (I only have a
hand-held jig saw though), and that would be what you see in that picture
So, with a lathe and a jig saw, it would be easy.
But without a lathe, I'd need the cone to exist in a material I could cut
(plastic or wood most likely) with a hand-held jig saw or circular saw.
You are half way there with the chop saw.
If it would be me I would go down to Lowes and buy a piece of round wood
stock and just cut it at different angles to show how a round circle can
be come can become the other pieces.
If you can not find a piece of round wood, you could do the same thing
with a piece of PVC pipe. After cutting you could sand the rough edges
and actually use the Pipe as a stamp; ink it and print the circles, ,
elipses, and hyperbolas.
It can't. If you cut a cylinder perpendicular to its axis, you get a circle. If you cut a cylinder at
any other angle, you get an ellipse. It is impossible to make a single cut through a cylinder
and get either a hyperbola or a parabola.
No can do. You can cut hyperbolas and parabolas from a cone, but not from a cylinder.
On Sat, 20 Aug 2016 21:06:46 -0000 (UTC), Doug Miller wrote:
You just gave me a great idea!
My original (and main) goal is to figure out where I can find a cheap cone
to slice into conic sections.
However, at the same time, I can get a similar diameter "dowel" and show
exactly what you just said!
I think, I might try a 2-inch diameter soft wood fence post.
What I can do is put my belt sander into a vise and then use that belt
sander to sand the soft fence-post wood into a cone.
It might look fugly - in which case I'll have to scrap the idea, but if it
works, I can then slice the resulting cone into the conic sections.
Then I can slice the original fence post into sections to show that what
you get out of a cylinder is different than what you get out of a cone.
I think this is a GREAT IDEA as it has to be cheap (my time is not worth
much, but my money is).
On Sat, 20 Aug 2016 14:12:53 -0400, Keith Nuttle wrote:
I don't think a cylinder will work but I guess I could put a cylinder
against my belt sander and have the belt sander (in a vise) turn the
cylinder into a cone.
Then I could slice the cone into the conic sections.
I have an old 2-inch diameter fence post that I might try that on.
I was hoping for a large conic section (like 12 inch diameter) but I can't
sand a 12-inch diameter dowel with a belt saw.
On Sat, 20 Aug 2016 21:09:22 -0000 (UTC), Doug Miller wrote:
That totally and completely misses the point.
If they existed, in wood, for something like five or ten bucks (at the
most), the google search would make sense.
But the wooden ones are in the hundred-dollar range, which is over ten
times the price limit.
I guess I didn't state that from the beginning, so, I apologize for not
being clear. The goal was to find an existing "something" that can be
sliced into conic sections.
The two best existing somethings are that I have 2-inch diameter fence
posts lying around, and I have traffic cones lying around.
So both are free.
My current plan is to put my hand held belt sander in a vise to see if I
can sand the fence post into a cone. If that works, I can easily slice the
cone with the 12-inch circular chop saw - but the kerf might be a bit wide.
If the kerf is too wide, I can probably jig saw it with a hand-held jig
saw, but it might not be a good straight edge.
The great thing about the fence post is that one 8-foot length affords me a
lot of wasted scrap! And it's free.
The traffic cones are also free, since I have a few lying around, but
they're harder to cut - but they're more visually appealing, if I can
manage to cut one. I don't think can double nap the traffic cones though.
So double napping will be best done with the fence post.
If I can find a larger-diameter fence post, I will try that, as 2 inches
seems too small to be visually appealing to the room (but it could sit on
the teacher's desk).
How about wax or clay instead?
YOu might even find clay free at an excavation, just look where utility work is being done. Or a hobby shop or a potter supply. Mold it by pushing it into the traffic cone. Cut it with a thin wire.
Or candle wax. Candles come 3 inches thick by a foot high, often for 50 cents at yard sales.
If those fail, plaster of paris from home depot is cheap, pour it into the traffic cones to mold it. 25 pound bag for $11.
On Fri, 26 Aug 2016 11:35:04 -0700 (PDT), TimR wrote:
I was thinking mostly wood - but plaster of paris should also work just as
well as long as I can slice it with a saw into sections.
As a matter of fact, paster of paris seems like the best idea overall, as
wood is too expensive (and hard to work without a lathe). Candle wax would
work but is too fragile (kids are monkeys).
Plaster of paris might be fragile too - but it's so cheap that I can make
extras. I probably need to find a mold which the inside of the traffic
cones might supply (except for the sharp tip).
On Saturday, August 27, 2016 at 6:23:44 AM UTC-4, Aardvarks wrote:
Read this first:
I don't think you'll need a jig saw if you do it soon after casting.
You might need a jackhammer if you wait too long.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.