Suppose I wanted to create equal lenght headers if I measured the outside of the bend I'd get a greater distance than the inside.

How would I know exact distance though?

 

If you are trying to create an equal length header and you want all pipes to be equal.

Look into using sand or water

 

you measure along the ccenterline of the bend, you can use a really small tape measure, or you can walk it with a protractor set at a 1" increment. Equal length headers can be done but it taks patience, creativity, and a whole lot of experience. We always try for tubes withing an 1/8"

 

string!

 

like casey said you've got to use the centerline radius to factor with.

to find the length of tube used in a particular bend -

use; CLR X DOB X .0174

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by L-CON1 &raquo;</TD></TR><TR><TD CLASS="quote">string! </TD></TR></TABLE>

thats what we did to measure runners on a few manifolds we built. just go along the center of the pipe/tube

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 90blackcrx &raquo;</TD></TR><TR><TD CLASS="quote">If you are trying to create an equal length header and you want all pipes to be equal.

Look into using sand or water</TD></TR></TABLE>

I dont understand this? I'm not trying to make a perfect bend I'll purchase those.

I'm new to the tubing stuff, so I'm researching, bare with me.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Casey@Burns &raquo;</TD></TR><TR><TD CLASS="quote">you measure along the ccenterline of the bend, you can use a really small tape measure, or you can walk it with a protractor set at a 1" increment. Equal length headers can be done but it taks patience, creativity, and a whole lot of experience. We always try for tubes withing an 1/8"</TD></TR></TABLE>

There are serveral different types of protractors which type specifically?

http://search.ebay.com/search/...prchi=

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fabrak8rX &raquo;</TD></TR><TR><TD CLASS="quote"> to find the length of tube used in a particular bend -

use; CLR X DOB X .0174 </TD></TR></TABLE>

School time: I need to know what each of those mean.

 

http://cgi.ebay.com/FANCY-OLD-...wItem

Like the one in the picture so you can set it a 1" length and walk the cnterline with it

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Casey@Burns &raquo;</TD></TR><TR><TD CLASS="quote">http://cgi.ebay.com/FANCY-OLD-...wItem

Like the one in the picture so you can set it a 1" length and walk the cnterline with it</TD></TR></TABLE>

Alright ill get one, thanks.


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote"> CLR X DOB X .0174 </TD></TR></TABLE>


How about this?

 

Just get a small cloth tape measure and run it across the centerline of the bend. It's really very simple.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 90blackcrx &raquo;</TD></TR><TR><TD CLASS="quote">If you are trying to create an equal length header and you want all pipes to be equal.

Look into using sand or water</TD></TR></TABLE>

Ding ding ding, we have a winner. People should really stop calling them equal lenght and start calling them equal volume manifolds. Equal length neglects if and when a header has stepped primaries or anything of the sort. It assumes each runner is exactly the same.

In short, measure the volume the runners can hold and if the volumes are close(within 5% error) they are EL.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zerostop &raquo;</TD></TR><TR><TD CLASS="quote">

Ding ding ding, we have a winner. People should really stop calling them equal lenght and start calling them equal volume manifolds. Equal length neglects if and when a header has stepped primaries or anything of the sort. It assumes each runner is exactly the same.

In short, measure the volume the runners can hold and if the volumes are close(within 5% error) they are EL.</TD></TR></TABLE>

Yep, really hard to get all bends to be the same volume inside. I find water and sand to be the most accurate.

 

Also, there's going to be quite a bit of cumulative error in measuring with any kind of linear distance device, protractor, tape, string, etc. Even with experience and practice, you can't reliably keep them on the exact center line of the tube. Sand or water all the way!

 

CLR X DOB X .0174


center line radius X degree of bend X .0174 = the length of material used in a bend.

ie, a 6.5" clr X a 90 degree bend X .0174 = 10.179 linear inches of tubing.


(in reguards to your original question)

 

With the length of the pipe along the outside you can back out the outer radius of the bend.

DOB = degrees of bend (45, 90 whatever if you're using elbows)
rO = outer radius of bend (from centerline of bend)
rC = radius at center of tubing
LO = length measured along outer surface
LC = length along center line
t = thickness of tubing

LO = rO * (pi/180) * DOB

then with that number, you can find the radius at the center of the tubing

rC = rO - t/2

Using rC, you can find the length of the center line radius using the same equation to the first.

LC = rC * (pi/180) * DOB

Its pretty much the same thing that fabrak8rX said, but he assumed that you already knew the center line radius.

 

How exactly do you use sand and water?

 

Fill primary tube, empty into graduated cylinder, write down measurement, repeat on other primaries.

 

Tape off one side of a runner, fill with sand or water, put into a 2 liter bottle and mark on there how high the sand fills up to and so on.