Faustian:
I think we have a problem.
As I understand it, each piece is supposed to be 7.5" long at the outside. The inside is supposed to be 1.5" long after you cut the 22.5° angle at both ends. Is that correct?
Okay, we found out that the OD of the pipe is not 6" but 6.25". If two 22.5° angles were cut even without rotating, the inside should be 2.32". The 22.5° cut lops 2.59" inches off each end.
Even if use 6.0" pipe, (which we thought we were, but we weren't), the inside edge should be 2.53" inches after the 22.5° cuts are both made.
I believe you said that the inside edge should be 1.5" long.
Do we have a mistake here, or did I figure wrong?
I think we have a problem.
As I understand it, each piece is supposed to be 7.5" long at the outside. The inside is supposed to be 1.5" long after you cut the 22.5° angle at both ends. Is that correct?
Okay, we found out that the OD of the pipe is not 6" but 6.25". If two 22.5° angles were cut even without rotating, the inside should be 2.32". The 22.5° cut lops 2.59" inches off each end.
Even if use 6.0" pipe, (which we thought we were, but we weren't), the inside edge should be 2.53" inches after the 22.5° cuts are both made.
I believe you said that the inside edge should be 1.5" long.
Do we have a mistake here, or did I figure wrong?
well, not so much a mistake as it is a change order. 🙂
actually, IIRC my model was made using a 6" INTERIOR diameter pipe. so the outer diameter would be 6-3/4", assuming a 3/8" wall thickness.
however, it's my belief all that is immaterial. the one sacred dimension in all this, is the 4.5" length down the middle.
so, derive all your lengths from that.
using a 6.25" OD pipe:
long side of wedge piece = 4.5 + 6.25*tan(22.5) = ~7 3/32"
short side = 4.5 - 6.25*tan(22.5) = ~1 29/32"
hey, i can do the math stuff too.
actually, IIRC my model was made using a 6" INTERIOR diameter pipe. so the outer diameter would be 6-3/4", assuming a 3/8" wall thickness.
however, it's my belief all that is immaterial. the one sacred dimension in all this, is the 4.5" length down the middle.
so, derive all your lengths from that.
using a 6.25" OD pipe:
long side of wedge piece = 4.5 + 6.25*tan(22.5) = ~7 3/32"
short side = 4.5 - 6.25*tan(22.5) = ~1 29/32"
hey, i can do the math stuff too.
planet10 said:
It'd be the highest honor.
I'm also keeping a video record of the trial and error process. Are you interested in an MPEG of the project once I'm done?
Dave
faustian bargin said:well, not so much a mistake as it is a change order. 🙂
...
hey, i can do the math stuff too.
Sorry to throw that curve ball. I thought I had measured correctly...
So now it will be 7 3/32"-->1 29/32". Cut once, measure those dimensions again, turn the marks 11°, cut again.
Yes? No?
Dave
kelticwizard said:
My wife: "Why don't I just post all my 3rd grade math papers that need to be graded"
Me: Laughs
She: "Why is that funny?"
faustian bargin said:yes.
if you can cut PVC to 1/32" tolerance with a hacksaw, you're a god.
Give or take 1/128th"
faustian bargin said:
...and don't forget the end piece, which is 6" down the middle and cut square on one end (see diagram posted previously):
long side = 6 + 3.125*tan(22.5) = ~ 7 9/32"
short side = 6 - 3.125*tan(22.5) = ~ 4 23/32"
Suggestion for lining up the inside measurement.
Cut a piece of the PVC about 2.5" long.
Take a 90° or so slice of that. Actually, any sizable angle.
Cut that down to 1 29/32, or thereabouts.
After you make the first cut, have rotated the piece 11°, and are going for the second cut in the piece, slap that 1 29/32" piece against the height of the oval you just cut. Then mark with a pencil. The curvature of the 1 29/32" piece won't allow side-to-side motion, and you can mark exactly the place you want to cut.
Maybe cut it just a bit shorter than 1 29/32" to allow for the pencil mark.
Just a suggestion.
Cut a piece of the PVC about 2.5" long.
Take a 90° or so slice of that. Actually, any sizable angle.
Cut that down to 1 29/32, or thereabouts.
After you make the first cut, have rotated the piece 11°, and are going for the second cut in the piece, slap that 1 29/32" piece against the height of the oval you just cut. Then mark with a pencil. The curvature of the 1 29/32" piece won't allow side-to-side motion, and you can mark exactly the place you want to cut.
Maybe cut it just a bit shorter than 1 29/32" to allow for the pencil mark.
Just a suggestion.
The very end of my pipe has a "sleeve" as part of the molding in order to just insert another pipe without the need for coupling. I wonder if I could use that for what you're suggesting, except I wouldn't need to cut it in half.
I would just mark its 11° off-axis point, then orient it with respect to the measurements on the piece about to be cut.
Dave
I would just mark its 11° off-axis point, then orient it with respect to the measurements on the piece about to be cut.
Dave
Have you decided how your going to make these cuts? Have you built a jig? Have you made any cuts yet? Whats the plan?
Sorry about that... It is going to be a difficult task at best. The most difficult aspect of cutting pipe is lining it up to make the cut in the first place.. no neat square edges to line up. I made many prototypes... cut bunches of pipe.. 6 inch..8 inch and 10 inch. Your looking at a bunch of cuts.. and each one of those cuts will be really difficult with out a jig to keep the cut straight..
Fortunately, You can use a simple jig.. I made a number of jigs with my project.. what worked best was a simple trough..three pieces of wood..each the diameter of the pipe..well actually the walls ought to be the diameter of the pipe plus the thickness of the floor.. anyway you simply lay the pipe in this trough and line your saw up with the walls of the jig..
Sorry about that... It is going to be a difficult task at best. The most difficult aspect of cutting pipe is lining it up to make the cut in the first place.. no neat square edges to line up. I made many prototypes... cut bunches of pipe.. 6 inch..8 inch and 10 inch. Your looking at a bunch of cuts.. and each one of those cuts will be really difficult with out a jig to keep the cut straight..
Fortunately, You can use a simple jig.. I made a number of jigs with my project.. what worked best was a simple trough..three pieces of wood..each the diameter of the pipe..well actually the walls ought to be the diameter of the pipe plus the thickness of the floor.. anyway you simply lay the pipe in this trough and line your saw up with the walls of the jig..
kneadle said:
Or a QuickTime movie... it would have to be well edited to keep the size down.
dave
a buddy of mine needed a ride to the auto shop to pick up his car. He bought me a few for the favor. We'll give it a go early Friday morning.
Yes, Steve, I'm afraid, very afraid.
Dave 😉
Yes, Steve, I'm afraid, very afraid.
Dave 😉
hey... don't be afraid... be prepared. If you have to be making marks.. and measuring angles on the pipe... it will be a dreadfully long day.. If you take the time to make a proper jig it will be a matter of laying your stock in place and cutting.. still a long day.. but your blood pressure won't be in the stratosphere.
Have a good time.. and maybe a beer or two...unless of course you decide to use a power saw.. then watch your fingers.. might want to watch them with the hacksaw too..
good luck...
Have a good time.. and maybe a beer or two...unless of course you decide to use a power saw.. then watch your fingers.. might want to watch them with the hacksaw too..
good luck...
I've done some work with PVC pipe. It is very difficult to cut the angles with the sort of precision you are after, especially with such large pipe. PVC is rather soft stuff, and the pressure required to hold it in place while sawing is enough to distort the shape, and so distort the cut. The other problem is the solvent weld glue allows you only about 5-10 seconds to get things lined up before it locks and prevents moving the pieces. I think if you're going to be successful at this you'll have to find a glue that gives you more time to work the joint into exact position. That means you'll need a pretty accurate jig to position the pieces and hold them while the glue sets up. Between the accuracy of the cutting jig and the accuracy of the gluing jig, I think you're in for a lot of heartache.
Don't overlook the possibility that such a coiled structure is already available off the shelf from a PVC manufacturer. Who knows, there is probably some industrial use for such a thing and someone makes it already, with a lot more precision that you'll ever be able to match. Call a PVC pipe maker or two and ask.
MR
Don't overlook the possibility that such a coiled structure is already available off the shelf from a PVC manufacturer. Who knows, there is probably some industrial use for such a thing and someone makes it already, with a lot more precision that you'll ever be able to match. Call a PVC pipe maker or two and ask.
MR
Some suggestions, based upon M. Rehorst's post.
A) PVC is soft, but the walls here are 3/8" thick. Will that distort?
B) The stuff for PVC piping in hardware stores is not the only glue, I believe, that PVC will stick to. There are several different glues on the market that are designed for vinyl, and I I think they have different properties. After all, PVC is Poly Vinyl Chloride.
Finally, if I were building this, I would follow Steve's advice and make a jig. Maybe that is because I used to work in a factory, and am used to the idea of a setup which turns out piece after piece after piece. Boring, but the result is pieces that are absolutely perfect and identical.
A) PVC is soft, but the walls here are 3/8" thick. Will that distort?
B) The stuff for PVC piping in hardware stores is not the only glue, I believe, that PVC will stick to. There are several different glues on the market that are designed for vinyl, and I I think they have different properties. After all, PVC is Poly Vinyl Chloride.
Finally, if I were building this, I would follow Steve's advice and make a jig. Maybe that is because I used to work in a factory, and am used to the idea of a setup which turns out piece after piece after piece. Boring, but the result is pieces that are absolutely perfect and identical.
I'm advising that I am currently setting up to cut. Wish me luck. I'll continue advising as need be.
Dave
Dave
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