hey i am new joint today,

[Meta]

i am interested in starting some metal work but to be honest i am stuck

i got alot of pre bent tubes and i just can seem to work out how to measure the angle/degrees of the bends

also what sort of tool can i bend 38mm mild steel tube (2mm wall thickness)

please bare in mind i am new and please go easy

[Stustoys]

Hi Meta
Welcome.
How long are the bends?
Are the ends of the tubes square?
How accurate do you need to be?

Get a sheet of metal or wood with one straight side or draw a straight line on a flat surface somewhere.
Put one side of the tube along the edge/line.(use a square across the end if the straight part of the pipe it to short).
Draw a line along the other side.
With a rule continue the line to meet the first edge/line.
Now you can either measure the angel with a protractor or you can measure 200mm along both lines from the point they intersect, measure the distance between the two points and use trig to work out the angle.
Hope this gets you close enough for what you need.

Stuart

[China]

This is just a guess, if you are building a buggy frame or roll bar and you are new to welding I would practice on some scrap first

[joe greiner]

If the legs are short enough, use an adjustable bevel (like this: Squares & Bevels - about half way down the page) to set the angle, and a protractor to measure.

If the legs are too long for that, use Stuart's suggestion.

Cheers,
Joe

[Meta]

Hi Meta
Welcome.
How long are the bends?
Are the ends of the tubes square?
How accurate do you need to be?

Get a sheet of metal or wood with one straight side or draw a straight line on a flat surface somewhere.
Put one side of the tube along the edge/line.(use a square across the end if the straight part of the pipe it to short).
Draw a line along the other side.
With a rule continue the line to meet the first edge/line.
Now you can either measure the angel with a protractor or you can measure 200mm along both lines from the point they intersect, measure the distance between the two points and use trig to work out the angle.
Hope this gets you close enough for what you need.

Stuart

length of the bends varie
sorry what do you mean square? 90 degree if so nope some are slightly curved and others are sharp
need to be rather accurate

i tried drawing around the outside of the bend drawing a line across to connect up the ends then i found dead centre of all 3 lines and drew a straight line through them but is this ok?

oh and yes this is for rollcage work. etc

[slhouetteV8]

If 0deg is pointing towards the east and you rotate in an anti clock wise motion you have your direction of travel.

So if you relate this to a compass, 0deg is East, 90deg would be North, 180deg is west and 270deg south.

If all bends start at 0deg then a line drawn from where the bend starts to where it ends will give you the degree of the angle/bend.

So if you have a bar sitting flat on the ground pointing towards the Right (East) and you bend it so it points North you have a 90deg angle.

If you have a bar sitting flat on the ground pointing right (East) and you bend it so it curves and points back towards the West, the degree of the curve would be a line drawn from the start of the curve to the end of the curve, 90deg.

[Stustoys]

sorry what do you mean square? 90 degree if so nope some are slightly curved and others are sharp

I mean "Were the ends of the lengths of tube cut square to the sides? If they arent cut square you wont be able to "(use a square across the end if the straight part of the pipe it to short).". It we also be a pain to weld.

i tried drawing around the outside of the bend drawing a line across to connect up the ends then i found dead centre of all 3 lines and drew a straight line through them but is this ok?

Not sure what you mean sorry. A drawing or a picture would help.

oh and yes this is for rollcage work. etc

Do you have to weld up the roll cage from pieces? I'd rather use one length of tube.

Stuart

[China]

If you are planning to engage in a C.A.M.S. event the cage must be built to C.A.M.S. specs( 2mm in most cases will be to thin) this includes the radius of the bends and the material it is made from, they may also require a welding certificate if they think the welds are suspect. You may already know this I am just informing you so that you don't purchase the wrong gear and put a lot of work in and have it all wasted

[Meta]

drew around bend of a subframe i had laying around





connected both ends together


found centre of line and drew a line through it


found centre or both ends drew line


measured degree


is this right?

[Meta]

I mean "Were the ends of the lengths of tube cut square to the sides? If they arent cut square you wont be able to "(use a square across the end if the straight part of the pipe it to short).". It we also be a pain to weld.


Not sure what you mean sorry. A drawing or a picture would help.

Do you have to weld up the roll cage from pieces? I'd rather use one length of tube.

Stuart

the large parts of the cage is going to be one piece bent tube but the little parts such as bracings of legs etc are going to have to be bent around the door skins etc

all perfectly square edges mate

[Meta]

If you are planning to engage in a C.A.M.S. event the cage must be built to C.A.M.S. specs( 2mm in most cases will be to thin) this includes the radius of the bends and the material it is made from, they may also require a welding certificate if they think the welds are suspect. You may already know this I am just informing you so that you don't purchase the wrong gear and put a lot of work in and have it all wasted

my welds are goodish just not tidy but penetrate well,

the cage isnt for any compliances its really just for retaining strength due to removal of panels of the vehicle

such as anything infront of the scuttle (bar subframe) the roof the boot + bootfloor the doors and rear bulkhead and rear seat some parts have been replaced with carbon fibre but the rear bulkhead cant be so i am replacing that with some cage

[Meta]

update

[Stustoys]

Sorry When you said prebent tubes I thought you meant short lengths of tube with one bend in them.

At first look at your drawings I'd say your idea is wrong. Your answer is about 60deg. The bend "looks" like its closer to 90(but it might be the picture). If the radius is smooth and your chalk work is correct the three lines should intercect at one point.
I'll have a think about it.

For the corner in the picture you could get two staight lengths of square tube lay them on the ground along the side of each round tube until they meet and just measure the angle.

Stuart

[Stustoys]

The way I figure it, your drawing, if done correctly will give you and answer of half the angle of the bend.

Cant you just do this?

Stuart

[joe greiner]

The bend (deflection angle) is properly measured between the tangents. Looks like about 85 degrees.

[Drawn freehand in MSPaint. Unreliable]

Cheers,
Joe