Custom Bicycle Frame

[ZooHead]

I'm going to attempt to make a multipart tutorial as I build a custom bicycle frame.

Depending on your needs, it starts as simply as finding or taking a picture of a bicycle.
It can also be extremely complex as there are so many things to consider.

If you're going to take the pic yourself, try to use a telephoto lens from the
side and get as far away as possible to reduce any perspective distortion.

The image I'm using is a rendering of a 3D model built and rendered by
Robert Biehle https://grabcad.com/robert.biehle-1

Pictures and free models can be had at GRABCAD: grabcad.com/robert.biehle-1
Built in Solidworks.

I have not downloaded his models yet, and there isn't a lot of
his work out there that I can find, but he is clearly into bicycles.

If you want to see all the pictures of this frame at different angles
look here: grabcad.com/library/custom-carbon-road-bike-frame-1

1 Cheetah unit = 1 inch
27.5 inch wheels

You can use the this jas file as a starting point for a road bike, but the next one I post will be altered to be the Track bike I'm going to build.

 

[ZooHead]

This is a road bike frame that I'm using as a reference for making a track bike.
A track bike will have a higher crank, aka bottom bracket height. (BB= bottom bracket)

A track bike also has a single fixed gear, so it's called a "fixie", and has no brakes or freewheel.
That means no coasting. If you're moving forward or backward, your legs are moving as well.
Some irresponsible people actually drive these on the street.

For track racing having no brakes is for safety reasons. Imagine a tight bunch of racers
going at top speed and the guy inches in front of you stops quickly. Your going down and
so is every one behind you. Then the track has to close for repairs because it's a wooden
track and it's probably going to get gouged by cranks and pedals.

Jas file added

 

[ZooHead]

I may have forgotten to mention this is a DIY tutorial.
You have to examine the jas files to figure it out.

I'll provide some screenshots, gifs and renders to help,
but don't hesitate to ask questions if you get stuck.

 

[ZooHead]

The part we're working on is the Top Tube but in this design it flows into the Seat Stays.
There are two seat stays, so copy the Top Tube and halve each copy.

 

[ZooHead]

Now you rotate each Bend Modifier to get the seat stays where you want them.
For a track fixie I've read 4.5 inches between stays so I'll do 4 inches
and later add .5 to one side to accommodate the drive train. Just guessing on this.

Of course you also adjust the bend itself to get the stays in place.

 

[frank beckmann]

I think I´d probably go with one half and 2 bend- and 1 symmetry-modifier in this case: I skipped the taper-mod.

 

[ZooHead]

A viable alternative but the stays are not symmetrical because of the gear on one side.
I would keep the double bend, but with two copies and no symmetry.

 

[ZooHead]

Here's the next jas file with Franks dbl bend.

 

[ZooHead]

Create a polygon quad strip inside each seat stay.

 

[ZooHead]

Point Slide two points on each side.

 

[ZooHead]

With two Bend Modifiers per seat stay I can easily adjust only the right stay for the drive gear.

 

[ZooHead]

Latest jas file.

 

[ZooHead]

Now make the two halves editable without the SubDiv Modifiers, merge them, Optimize
to weld points that are close together. (remember we are not symmetrical anymore)

Then weld a few points and add a few polygons to button up the mesh for the Booleanism.
The Boolean operation will only be for "drilling" a hole slightly larger than the seat post tube.

 

[ZooHead]

Next jas file:

 

[ZooHead]

Here's what it should look like with a Boolean Subtract using
a copy of the seat post with .04 added to it's diameter:

 

[ZooHead]

Here's the mess we're left with when it's made editable again.

 

[frank beckmann]

The "Welder" is your friend.

 

[ZooHead]

This is tedious work. But the more you do it, the more you develop an eye for which lines to honor.
As Frank says, the welder will become your friend.

Here's the final result of all the welding and cutting.

 

[frank beckmann]

What scares me a little is that these are the sturdiest parts in place. Most of the more expensive frames are BTW hard soldered and not welded. I wonder how stable it can be at this point in real life&color?

 

[ZooHead]

What scares me a little is that these are the sturdiest parts in place. Most of the more expensive frames are BTW hard soldered and not welded. I wonder how stable it can be at this point in real life&color?

This frame is carbon fiber.