How To Build Your Own Bike Frame

- We've covered many, many different aspects
of maintaining your bike here on GCN,
but have you ever thought
about actually making one?
Now I don't just mean assembling it together
from all the different component parts.
I mean actually welding or braising
together your very own frame.
Well, this is the Bicycle Academy in Frome, in the UK,
and it exists to help people do just that.
So, with their assistance, we are gonna take you
through the process.
This is how to build
a bike frame.
Now, Andrew Denham, behind me, is the founder
of the Bicycle Academy and he is gonna be our teacher today.
Andrew, I am ready to do some welding.
- Now, wait a minute Si.
I think we're gonna have to back up a second.
- Really?
Huh.
(slow rock music)
- Tom, I'm pretty adept at looking
at a bike manufacturer's website
and seeing a geometry chart and knowing whether or not
a bike is going to fit me.
But the idea of looking at a blank sheet of paper
or a blank whiteboard
and actually starting from scratch,
actually makes me a little bit nervous.
So how do you do it?
How do you get the geometry right?
- Sure, so it is quite a tricky part of the process.
And the first thing we've got to consider is
the rider's position. - Okay.
- We've got to make sure that
their body is in
a suitable position to allow them to use the bike properly
and that will depend slightly on what type of bike it is.
So, if we think about
the rough shape of your contact points with the bike,
so we've got a bottom bracket
to which cranks will be attached,
a saddle,
- [Simon] Yeah.
- A stem with some handlebars attached.
What we're looking to define first and foremost
is
some boundaries about where we might be able
to put the saddle and where we might be able to put
the handlebars, in order to suit that rider
but also what type of bike it is.
So where we might aim for would be different
depending on the type of bike.
And then from that,
we'll take some key measurements.
- Yeah, so far, so familiar.
I know all of those numbers and I'm pretty confident,
but how do we join
that bit to that bit to that bit
and know that the bike is gonna handle
brilliantly at the end of the day?
- There is no quick answer to that,
so it does take quite a lot of iterations.
But there are a few things
that we want to consider first and foremost.
So thinking about how we want the bike to handle
out on the roads, specifically how it's gonna respond
to any dynamic rider input.
We need to
think about the most important dimensions,
and those are wheel base and the mechanical trail,
which are defining the sort of straight line stability
and also the cornering stability.
- Okay, so we've got our fit points here.
I'm still really concerned, Tom, 'bout how I'm
actually gonna join it all up
and make a frame out of it.
- Sure, so once we've got
everything sorted and we're happy with the rider position,
then we start looking at a
CAD system that we use to design the geometry
and then ultimately move on to the structure of the frame
and stick some bits of metal together.
- Alright.
- Okay, so once we've got the fit information from
the fit session that we did,
we can put that into the model
in such a way that it fixes
the rider's position
and that frees us up to design the geometry of the bike
for the specifics of what we're looking to do.
So, we can set the wheel base
and we can
do that and then manipulate the chain stay length,
for example.
- To know what those numbers
should be
is that,
is that artistry or, you know, could you
copy them from an existing bike?
- So, if you're starting and you don't have any numbers
in mind, then
using existing bikes is a perfectly valid way of doing it.
If you might have ridden a bike in the past
that you liked how it felt, well you can go in,
as long as you're looking at the right size,
you can look at the wheel base and some of the other
dimensions as well and get a feel for what that bike was
and that's a pretty good starting place, yeah.
(slow rock music)
- Step two of the process and we're now onto selecting
the tubing for our frame.
Now, we're confident that the CAD drawing
has spat out the right dimensions, even down to the
location of the bottle bosses, to make sure that
we can get two bottles on our frame.
But now we're presented with a
huge array of different tubes.
How're we gonna select the right ones?
- So there's a few different manufacturers.
We're working with steel and we're gonna be using
tubes from Columbus, an Italian company.
And they offer
hundreds and hundreds of different tube options,
both in terms of different alloys,
so actually slightly different versions of steel.
- Okay.
- And also different lengths, different diameters,
different wall thicknesses and that sort of thing.
So, as well as the actual, physical size of your bike,
we have to consider the loading
that it's going to go through,
things like how heavy you are, what sort of power output
you ride with and also whether that's power
delivered through high cadence or low cadence
and whether you like, for example, sprinting or climbing
in and out of the saddle,
what your preference is.
- Okay, 'cause it's a common misconception, isn't it,
that you could get a tube set,
let's say, Columbus XCR, which they're stainless steel,
and it would give you a
a certain ride quality, when actually you can
alter the diameters of the tubes and the shapes
of the tubes and even the lengths of the tubes,
and actually that is gonna be what governs
how your bike feels to ride.
- Absolutely, yeah.
So the different alloys do have different
properties.
They're largely there to give the designer or the builder
a range of options in terms of wall thickness,
butted profile, shaping of the tubes and that sort of thing.
And combining is
actually
relatively common to combine different alloys of tubes
in order to get different properties in different
parts of the frame.
- Columbus, on their website, they will actually sell you
a seat tube, and a chain stay, and a, you know, head tube.
And it's that
specific a use.
So like this one, for example,
that is gonna be a chain stay?
- That one's a fork blade.
We've got some chain stays here, so.
These are some chain stays.
- I thought that was a BMX chain stay.
- It would look quite good as a chain stay.
- Yeah, there you go.
Can we play a little game?
Could you tell me exactly what each tube was,
if you turned around and I plucked one out of thin air?
- I could have a go.
(both laughing)
- Right, close your eyes a minute.
Hang a minute.
I gotta find one.
That might be easy, let's see.
What's that?
- That's a steerer tube, so that's a one-inch
steerer tube for making a fork.
- One inch steerer tube!
Man alive.
What've you got that there for?
And there's that.
A mountain bike chain stay?
- That's correct, yep.
So that's a chain stay with a bend for big tyre clearance.
- Cool.
So, fork blade?
- Chain stay, yeah.
- Chain stay, yeah, got that one.
And then one last thing,
we haven't got a down tube yet.
- Here you go, here's a down tube.
- Whoa!
Look at that.
Here we go then.
We've got our tubes.
- Let's go build a bike.
- Let's go build a bike.
Right, we've got our tubes.
Tom, is it time to do some welding?
- Unfortunately, not yet.
We've got a few more steps to go,
so we're going to
cut these down, shape them, so mitre them up together.
Tuck them together as well,
so that we can get it out of the jig,
do all the braising and then finish it up, ready for paint.
- Alright.
Well, at least steps one and two of the process
are now done.
We have our geometry, we've got our working dimensions
and we have our tube set.
If you want to see those next processes, (COMING SOON)
then they will be in the next two videos
in this series, and you can get through to them
just by clicking down there and down there.
Now, we need a much needed tea break,
but while we're doing that, make sure you subscribe to GCN.
To do it just click on the globe.
How do you take it?
Milk, sugar?
- Milk. - Cool, bye.

How To Build Your Own Bike Frame | Maintenance Monday

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