(rock music)
- Building your very own bike frame
is the dream of many riders
and it just may be more accessible than you think.
This is part two in our how-to guide
and our GCN frame is beginning to take shape.
We have our working dimensions.
We have our tubes.
Now we need to set up the jig
mitre and then tighten the tubes into place.
And this is all being done
under the watchful eyes of The Bicycle Academy.
Andrew, we have our tubes.
Can you explain how the jig works?
Because none of these are the right length
at the moment are they?
- No, that's right.
So they're all straight ended.
They're not gonna fit together and make a nice bike
so what we're gonna have to do
is cut them and shape them.
But before we do that
we need to set this thing up over here.
So, this is the jig.
It's a tool which allows us to hold
all of the tubes together in the right position.
The same position that we've designed.
- Okay.
- It's entirely adjustable.
It's something which we can change
according to the design that we're creating.
So should we take the numbers
and set it up right now?
- [Man] Yeah let's do it.
- So the way the jig works
is that the bottom bracket is zero
so everything is referenced according to that.
- Okay.
- So, what we're going to do
is we're gonna start off by positioning the head tube.
So we've got 73 degrees.
So if we take this here and adjust it to 73.
And then the seat tube which is also 73.
Okay, and now we're gonna position the head tube
so we need to set this up 448.
So if you want to adjust that down here.
- [Man] Yeah, alright.
448, right.
There you go.
- Cool, and now the vertical
we need to set that up 423
so it's this one here.
If I loosen it and you position it.
- That would help, yeah thanks.
423, okay.
- [Andrew] And now the back end which is 401 and 75.
- [Man] Okay.
And so that's rear axle.
- [Andrew] That's right.
- [Man] Okay.
- And this sets our chain stay length.
- Oh so because we're only building a frame
it's irrelevant where the front axle is
because the fork is.
- Yeah, and that's all factored in already
but we don't need to think about it for this part here.
- [Man] Yeah, okay cool.
- So we need to do now is put the bottom bracket
and the head tube into the jig.
- Okay.
- So, I'll start with the bottom bracket.
So pop it on here.
- Right, so we have a head tube and a bottom bracket
are now in exactly the right place.
We just have to make the tubes fit?
- Yeah, that's right.
So if you take the seat tube.
Although it's the right tube, it doesn't fit.
The shape of this doesn't fit this
so what we're gonna do now is we're gonna cut it
and we're gonna shape it
and I'm gonna teach you how to do that.
- [Man] Brilliant.
- Great so, our seat tube is it's too long right?
And the bottom of it is the wrong shape.
We need to make it shaped so it's gonna fit to this
the bottom bracket.
And so the way that we're gonna do that
is we're first gonna mark it up
to make sure that we cut this shape at the right point.
- Okay.
- And we've already done that
and the length is 480.
So the next thing that we need to do
is pop it in the vice.
- Yup.
- And then do a rough cut
for using the file to make it the right shape.
Okay so I've marked up the tube.
- Yup.
- We've got that dimension.
I've clamped it in the vice
and what I'm gonna get you to do
is do a rough cut
so that we can start shaping it.
So here's the saw.
- Right, okay.
- Over to you.
- Yeah, you gonna show me how to use it properly?
- Yeah so, draw the saw back towards you.
Okay now forwards, and repeat.
- Yeah that almost looks like
how I expected sawing to be.
(saw scraping)
Okay, I think I'm at the mid-point.
- Cool, so now I'm gonna rotate it
and we're gonna repeat.
We've roughed up the tube.
- Yup.
- We've taken off the edges.
And now we need to make it fit really well
to this tube, the bottom bracket.
- Okay.
- So what I'm gonna get you to do
is follow my lead alright.
You're gonna take the file in two hands
and you're gonna push it across this tube.
- Across this time.
- Absolutely.
Repeating this process equally on each side
and then check the two fit together.
Wherever there's contact, that's a good thing.
If there's a gap
the way that we're gonna get rid of that gap
is by continuing to file wherever the contact is
so it's touching all the way around.
- Alright, and this is the process of mitering?
- And this is mitering.
- Okay.
So we're still filing the sides down by the look of it
is that right?
- That's right.
- Okay.
(file scraping)
We're getting pretty close now.
We're what, about half a mill off Andrew?
- [Andrew] Something like that yeah.
- Okay.
Slowly does it.
Should we try?
- Yeah.
- Alright, okay.
And then I need to drop the jig down is that right?
- [Andrew] That's right.
- Seat tube.
Right, how many more have we got to go?
- Six more.
- Starting with the down tube.
- Alright, cool.
(rock music)
How's that looking Andrew?
- It looks really good.
- Cool.
- The top tube's one of the trickiest tubes to get right
because any change you make at one end
effects the other.
- [Man] Right.
- So we really have to make sure that that's spot on.
- As in, if we'd filed too much off
that would just have gone
(whistles)
and slipped down.
- Absolutely, that's right.
- [Man] Okay well lucky.
- Okay so before we tack this
we need to make sure that we can fit a bottle in position
and we need to position the bottle bosses.
So this is where it's gonna go.
We're gonna take some measurements
and then you're gonna drill some holes.
- Alright, bottle bosses.
(drill whirring)
- [Andrew] Try and get more force.
- About to go.
Right, we still don't have a back end on the bike now
but it's time to do some welding right?
- We're actually brazing.
- Same thing.
- No, so there's a bit of a difference.
With welding, we're gonna join the tubes together
by melting them.
With brazing, we're gonna melt something else.
We're gonna melt this and brass.
- Okay.
- [Andrew] So it's a high temperature process
but it's not quite as hot.
- Okay, cool.
Now this isn't the point at which
these tubes are like completely fused together is it?
- No that's right.
So we're just trying to hold them together
to the same shape as it is in the jig
so that we can take it out of the jig
to do the full braze.
- [Man] Okay.
- [Andrew] So this is called tacking.
- [Man] Right.
- And the first thing we need to do
is put some flux on, on every joint that we're gonna heat up
and then we're gonna put little spots of braze
in some key places so we can take it out the jig.
- [Man] Okay, what does flux do?
- [Andrew] So flux stops the steel from oxidising
when we put all that heat into it.
- [Man] Okay.
- [Andrew] We need the steel to be nice and bright
so we can get a good quality joint.
(rock music)
- So this is a specific brazing torch now right?
- That's right, so we're gonna be burning
acetylene and oxygen.
- Okay.
- And this torch allows us to control
how much of each of those two things we're burning.
And therefore, the profile of the flame.
- Okay.
- So I'll light up.
- Whoa.
Whoa! Whoa.
That's like a lightsaber.
That's amazing.
Weld in place.
- Yup, bring the flame in.
A little closer.
Hold it there, push the rod down.
And now twist the torch towards the top tube.
Or towards the top tube.
Or the other way.
- Oh sorry.
- There are two ways.
(laughs)
- Yeah the top tube as opposed to the seat tube.
- And stop, good job.
That's a really good tack.
- Whoa, woo!
Check it out.
Here we go then, one tacked up frame
unmistakably bike shaped.
Look at that, there's a few hints on there
as to just what kind of bike this is going to be.
So, also some bits on there
that you probably didn't recognise yet isn't that right?
- Yeah, that's right.
We made those a bit earlier.
Off camera, it's much easier to do that
in sub-assemblies, but we popped it all together
and now it looks like a bike.
- That's right.
So we're very nearly there.
We just have to braze and then we have to finish.
Which we will cover in part three.
If you want to get through to that section
then click just down there.
If you didn't see part one
of how to build a bike frame
then that is just down there.
And then we're off to get another cup of tea
because well, we've been working pretty hard.
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