New Pipe Layout

[JohnL]

With wire welders on thin sheet they tell me to do a succession of tack welds, go back after it cools for a minute and put tacks in between the old ones, go back again etc until the tacks are overlapping creating a complete weld. The reason to keep from overheating and warping the metal, though it looks like there is no problem with that there.

 

[JimL]

Id like to see the spread sheet when your done, How do you figure the arc between the corners, circumference is easy to figure out.

 

[Dennis Cahoon]

Al....the trick is to make your cones butt up tight. Then get your heat right and fusion weld them without popping thru. Any gaps and you'll pop thru and have to use rod.

 

[timberwolf]

The arch between the corners is easy enough.

Lets say the cone section goes from 46 mm to 76mm diameter in a distance of 100 mm.

(1) 76mm-46mm = 30mm
(2) 30mm/2 = 15mm which is the change in radius from big end to small end

(3) square root of (100mm)squared + (15mm)squared = 101.1, this is the 3d length of the cone as if it were measured along the metal.

(4) now take the small end radius 23mm divide by 15 mm change in radius from big end to small end = 1.53 multiply by 101.1mm = 155.0 mm this is the radius on which to draw the curve for the small end of the pipe section, for the large end add 101.1 + 155 = 256.1mm.

The tougher part is to determine the location of the strait lines on the template.

 

[jokers]

Gas welding with the right tip also anneals the metal next to the weld eliminating the HAZ, or Heat Affected Zone common in arc welding which causes embrittlement. This is especially significant in thin metal subject to high vibrations as Brian is working with, and thicker structural metals which might experience a shear failure near the edge of the localized HAZ. Post heat and mechanical stress relief are often necessary to minimize the effect of the HAZ.

I know that Brian knows all of this, his dad is also an expert in these things, just thought I`d mention it for anyone who may be just starting to weld.

Russ

 

[JimL]

The arch between the corners is easy enough.

Lets say the cone section goes from 46 mm to 76mm diameter in a distance of 100 mm.

(1) 76mm-46mm = 30mm
(2) 30mm/2 = 15mm which is the change in radius from big end to small end

(3) square root of (100mm)squared + (15mm)squared = 101.1, this is the 3d length of the cone as if it were measured along the metal.

(4) now take the small end radius 23mm divide by 15 mm change in radius from big end to small end = 1.53 multiply by 101.1mm = 155.0 mm this is the radius on which to draw the curve for the small end of the pipe section, for the large end add 101.1 + 155 = 256.1mm.

The tougher part is to determine the location of the strait lines on the template.

sure thing im not that good with ##'s

 

[timberwolf]

Just to give the example of whats the trick, if you take a 2x4 8 feet long stood on end straight up, the top is 96 inches off the floor. if you lean it to one side the top gets lower to the floor the more you tilt it. So if you wanted a 2x4 at a 8 degee angle from straight up to have its to exactly 96 inches above the floor it would have to be longer than 96 inches.

So the first step is to find out how long the metal of the cone needs to be. The cone its self in the example needs to be 100mm long if measured straight down the middle, but because the sides are tilted at the cone angle the metal must be cut longer to make up for this.

Once you got that number you can move on.

to explain the radius of the curve, take a triangle piece of paper and roll it into a cone. You will note that the cone is not even along the base, this is because the length of the sides of the cone are not even. Now take a circle shaped piece of paper, cut a large chunk of pie out of it and roll the paper into a cone, this cone has an even base all the way around because the distance from the point of the cone to the base is the same at any point around the cone.

The idea behind the calculation is to take a cone section and make a projection of where the cone would come to a point if it were to be extended. from tis point a radii can be drawn to give a equal distant curve, so that when the metal is rolled into a cone the base is even all the way around and the cone section will butt evenly and tightly against the next section.

 

[Al Smith]

A little note,for those inclined to do sheetmetal work and desire more knowledge.A book ,titled appropriately"sheet metal" by Leo A. Meyer,describes in detail how to lay out elaborate bends etc.It is the same text used by the sheet metal workers union in their apprenticeship training.The ISBN number is 0-8269-1907-3 and available over the internet.I think I paid around $25 for mine.

 

[timberwolf]

More or less finished the pipe. Re did one cone section that I made a calculating error on other than that Everything fit well. I think the math I worked out is valid, I did put it in an Excel format, but want to test it out some more.


I only bent the pipe out 90 deg to the side and left it horizontal, I wanted to try it like that before bending it up and back. I had seen some guys cutting with pipes straight out to the side and want to give it a try first. Any opinions on having the pipe 90 deg out to the side as opposed to swept up and back?


here are some photos, needs a bit finishing, a support bracket and some high temp paint.

 

[timberwolf]

Numbers are in

Muffler on 12" poplar single cut
2.42

Old Pipe
1.93

New Pipe
1.65

The newer pipe sounds a little quieter and definently holds the unloaded RPM down, but cuts a good bit faster.

 

[GOBRDGO]

Way to go Timberwolf, That is impressive indeed.