Mathematical Genius HELP

[BIGNASTY]

Ok I have a question for a Mathematical Genius Type person. Im building an entry gate to our place. The driveway will be 20 feet wide. The pillars on the sides of the drive will be 25feet center to center. The pillars will be 10 feet from ground to top. I would like to build an arch out of some 12 inch pipe from pillar to pillar and have it be at least 20 feet high in the center so I can put a plasm cutout of our brand in the center. BAR- B N . How long of a piece of pipe will I need to make the arch. Also unless anyone can come up with a different way of doing it I plan to make the arch by cutting an welding the pipe in Angles to make it. So the degree of the angle cuts would be nice if you could figure it. This seems daunting to me but im just an old truck driver that can only figure the angles sitting in the driver seat. Thanks for your Help BIG

 

[fest3er]

To get you in the ballpark:

For a simple semi-circle atop the pillars that will give you 25' clearance at the top, the equation is pi*d/2. The span is 25'. The length of pipe needed is measured on the outside (upper) edge of the installed pipe, so add plus 2*pipe diameter/2 (12" in your case) to center the pipe on the pillars. The outer diameter of the arch is 26'. This works to (3. 14*26/2): 41' pipe. Be sure to add to that what you'll waste in cuts (width of the cut times the number of pieces is close enough).

As to angles, how many pieces do you want to cut and weld? 10? 20? If ten, you'll have 10 steps to get from 0 degrees to 180 degrees; the angle is 18 degrees at every welded joint; each piece of pipe gets a 9 degree cut. If 20 pieces, you'll have 20 steps, or 9 degrees at each welded joint and each piece will get a 4. 5 degree cut. The ends of the arch are, of course, square.

If you want a semi-oval on top with the outside height closer to 21', that'll be a very different calculation. It should be less pipe, but the angles will be very different and non-uniform.

 

[BIGNASTY]

The amount of cut's is no big deal to me and the welding is not that bad either as I have a SA 200 Lincoln. The arch would be nice to be just a continual arch. So what ever would be the easiest to do that would look good nice smooth arch. So many others around here just have Vertical and horizonal over head. We would like to be DIFFERENT (like im not already). The clearance at the top could be more as this is BIG SKY country and I would like it at least 20 high to get enough clearance to get equipment in and out without going thru a by pass gate. To mount it on the pillars I was going to get some plate cut it with the I D of the pipe weld it to a 8 inch drill casing run it thru the pillars and into the ground and cement the whole mount in to the ground and pillar. Then weld the arch to the plate on top of the pillar. Thanks for your help Ill take the info you gave me to my drafting table and draw it out and see how its going to work now that I have some idea of what to use for numbers thanks again BIG

 

[The patriot]

Sounds like youre building some sort of a "compound". :-laf

 

[rscurtis]

I assume you don't want a semi circle, but want a "chord", which is part of a circle. If you can find a copy of Machinery Handbook, it has a section on chords that will help you.

 

[BIGNASTY]

Ill look for that Machinery Handbook thanks. Ya im looking for a half of a circle or (chord) kind of thing the first thought was to extend it down and add the gates into the arch making it a full circle. But this is going to get me picked on by the guy's at the Dinner that I have breakfast a couple time a week enough. No compound just a way to keep out the UN WANTED AND UN INVITED. Mostly just because someone is always driving down this drive and thinks it's a county road its not its our driveway then they turn around and throw dirt up and the wife #@$%! (Im sure you get the picture) But the COMPOUND thing will stop them long enough to get a bead on them it''s only about 400 yards from the gate to the house. :-laf

 

[Wayne M.]

Id like to see this project in pictures. Geez my whole lot is 45X100...

 

[BIGNASTY]

Pics

I will do the pic thing (wife takes most of around the house projects pics) but the first thing is HUNTING SEASON until late Oct early Nov. Then off to Calif in the first part of Dec. to have a knee replacement. And the project is in the drawing board stage right now so parts and cutting will follow some knee rehab (not looking forward to that) but the gate project will be good for a LONG WINTER IN MONTANA PROJECT followed by a spring (mud season) install. This is the back yard from house to the rock side of the hill is about 750 yards. Sometimes I think what the hell was I thinking about. I had 5 acres in Calif. This is alot of yard to cut but with those kind of lawn mowers it makes a little better. Your lot is how big 45x100 ill cut your's if you cut mine

 

[GHarman]

BIG, You can do the math and figure a perfect scenerio. Or you can draw it to scale and do the layout on construction paper. Similar and fairly simple. Both ways work. Be Glad to help with the planning and layout, if I can be of assistance! GregH

 

[BIGNASTY]

Greg I got it going on the drafting table. Along with the house plans,barn,polebarn for feed, out house for the solar, back up gen, :-laf you thought I was just going to leave it as out house didnt you, YES SIR WE HAVE INDOOR PLUMMIN IN THIS HERE HOUSE :-laf I know that I could count on you Greg THANKS

 

[The patriot]

Couple speed bumps and a sigh saying "If you can read this you're within range" should do it. :-laf

 

[BIGNASTY]

Cant do that would have guldump crying about some minor I TRIED TO BY-PASS THE CUSSING FILTER like civil right's or some other kind of BS that I should give a I TRIED TO BY-PASS THE CUSSING FILTER about :-laf We had a sign that said WE DONT DIAL 911 And had a pic of a S&W revolver

 

[Blu-meanie]

Sometimes trespassers just have unfortunate accidents while you are cleaning your guns.

 

[fest3er]

Ill look for that Machinery Handbook thanks. Ya im looking for a half of a circle or (chord) kind of thing the first thought was to extend it down and add the gates into the arch making it a full circle. ...

I'd suggest an oval. But that would be too similar to the 'blue oval' and that just wouldn't 'do' for a Dodge man.



Attached is a possibility: a semi-circle on the bottom and a semi-oval on top. Or flip it over.



If you wanted to be truly creative, put one angry 'beady eye' 20' up your driveway and the other 150' up your driveway. And put a frowny-mouth somewhere in between. When the observer is in the right position, an angry, unfriendly face appears. Any other position and they're just a bunch of odd metal works.

 

[GHarman]

For anyone interested

Heres the process if more are interested.

You need; exact outside diameter of pipe and circumference measurements. The more precise the measurements the less stacking error in multiple parts.

A pipefitters wraparound(a type of template with two parallel sides. ). The wider the wraparound the more closely a line drawn against the template is 90* in relationship to the axis of the pipe.

Here's the development procedure. GregH



Parallel Line Development - Round Pipes

 

[GHarman]

PS if you really want to get technical, you should make allowances for the thickness of your template.

The weld joint preparation is another issue. Allowances for root penetration, angle of the bevel and alignment of each joint. While welding you must consider that steel will expand/contract 0. 00075"(3/4 of a thousandth of an inch)per inch per 100*F. So the larger the part the more distortion. In a semicircle/arch the welder can move a large part a huge amount if it is not secured. Weld sequencing is a must. GregH

 

[BIGNASTY]

Sounds like you are trying to make me terrified Greg and it's WORKING

 

[GHarman]

Not at all, BIG! Its a process, just like any other project. Step #1 through Step #X. You can do it! GregH

 

[GHarman]

Pipe schedule and wall thickness

Heres another parameter. We need to confirm the OD of the 12" pipe. Pipe under 14" is nominal ID. The OD is plus 2X wall thickness. OD of 12" pipe is normally 12. 750". This will provide a more accurate calculation. However, if you are using what is classified as TUBE, it will be different. Here is an example;

Nominal Wall Thickness Pipe

GregH

 

[GHarman]

material handling issues

calculating the weight of your structure is another parameter. 12" pipe comes in many different wall thicknesses or schedules. If you have a pipe that is 40 ft long and is schedule 20, it has a 1/4" wall thickness and weighs 33. 38 pounds/ft. . Your pipe length weighs 40' X 33. 38#= 1335. 30# . Just some more information to sweeten the pot! GregH

Please see chart;

Pipe Sizes and Dimensions | M. A. Selmon Company, Inc