Girders

[tbone]

Right then, Girders eh, ok. Let me start by saying that this is not going to be a blueprint for Girder making, sure, i could give you sizes, dimensions and angles, and off you`d go and make a set, and yes they`d fit and work but there are so many varients possible that i`ll leave it to you to sort the details. I will however, hopefully at least, show you how to go about making a set.
I don`t actualy have a use for a set yet, but i have got half an idea for them, but first lets see if i can make some!
First job then is to make the main leg assembly.
I`ve pre-drilled a pilot hole near the end of my tube and now i`m ready with the holesaw to cut the tube.

[tbone]

The holesaw is the same diameter as my tube and will cut a nice mitre in the end of it.

[tbone]

This is to allow me to slot a shorter piece of tube in the ends and will give a nice joint for me to weld up.

[tbone]

with the ends of the 2 long tubes notched, i cut an 8" length of the same diameter tube and tack welded it squarely onto the longer bits.
Straightforward job, use a square to make sure the tubes meet at right angles and leave a 1/4" hangover at each end of the short tube, this will give you something to weld to later 

[tbone]

And here`s how it looks. Do i need to mention that when your tacking this together, do it on a flat level surface?

[tbone]

Now its out with the bender and some more tube. At this point you`ll need to know what length headstock you`ll be fitting your finished girder on to because this will affect the position of the bend. How much of a bend you put in is up to you, the longer the Girder, the taller you can have the bend, its all about looks.

[tbone]

A few pumps on the handle .......

[tbone]

then try it in place. When your happy with what you have, make a second one.

[tbone]

Then lay the legs back on your flat surface and position the back leg so that you can mark the taper you need to cut in order to weld the legs together.

[tbone]

you`ll need to mark both top and bottom tapers on the rear leg.

[tbone]

with the tapers cut, lay the rear leg onto the front one and after making sure it sits squarely, tack weld it on. (yes mine is a little off in the photo, i couldn`t hold it all square and take the picture  )
Do the same again with the second rear leg and use a spirit level across them to ensure both legs sit the same height.

[tbone]

Now you can weld everything up fully.
After my initial full weld i layed a second bead on as a filler, this means i can flatten the second weld off and produce a solid looking assembly.

[tbone]

The filler bead is not structual so i can grind it down to produce a flush `gusset`, purely asthetical but helps give a `chunky` look to the girder.

[tbone]

then its time to put in the lower cosstube. Mark down from the centre of your toptube, the length of your headstock, then knock up a couple of support brackets, these will be welded to the front and rear forks.

[tbone]

Before i cut the brackets out, i cut out another inch diameter hole on the centre line of the bracket, 6mm in from the front leg. Again, the 6mm gap will allow you to weld the bracket in.