How much wouold it cost to build a 4 foot half pipe?

Question

How much wouold it cost to build a 4 foot half pipe?

Answer 1

Let's get this straight. You want to make a half pipe using a plate say steel of a given thickness t by welding a half circle bent plate on a flat plate?.

Let:

L = the total length of the pipe in feet which is and integer multiple of the unit width of the plate

W =unit width of issue of the  plate  say 6ft and 8ft

l = unit length of issue of the plate say 20 ft

a = unit price per square foot of the plate of thickness t in $/sqft

b = unit cost of welding per foot in $/ft

c = unit cost of cutting per foot in $/ft

d = unit cost of bending in $/sqft

h =unit cost of handling n $ / sqft of the raw materials

The plate length of the half round sections is:

(1). C = pi x 2 = 6.283,  

thus a 6ft x20ft long plate could produce 3 pcs of half round sections of 6 ft lengths

For a total length of pipe L, the number of 6x20 plates needed is:

n1 = L/(6 x 3)

For the flat plate part we use a 8 x 20 plate which would be cut longitudinally to 4 ft wide. Hence the number of 8x20 plates needed is:

n2 = L/(20 x 2)



The total area of raw plates needed therefore is:

A = 6x20n1 +8x20n2

and the cost of the plates is;

M = aA

The total length of cut to be done is:

For the 6x20 plates; s1 =( n1x3) x6 = 18n1 in ft

For the 8x20 plate; s2 = 20n2 in ft

The total length of cutting work would be;

s1 + s2 = ( 18n1 +20n2)

and the cost of cutting is:

B = c(18n1 +20n2) in $

The total length of weld to be done is:

butt weld of the curved plates, w1 = (3n1 -1) x 6.283 ft

butt welld on the flat plate w2 = L feet

Fillet welds of the curve plat to the flat plate (both sides)

w3 = 4L

The total length of welding work therefore is:

w1 + w2 + w3 = 5L +(3n1-1)6.283 ft

and the cost of welding is

W = b(5L +(3n1  -1)6.28) in $

The cost of handling the materials is:

H = hA in $

The total cost of fabrication therefore is:

Total direct cost = M + B + W + H

There may be other incidental costs which are not accounted for in the above and the normal practice is to cover it as an overhead cost of about 10 to 15 % of the total direct cost.

If you are doing this for somebody else and for a profit then you just have to crank in you desired profit margin.