Hi there!

Occasionally, I take the train to another city in Belgium. When I arrive in the city, it's always very useful to have a bicycle. Unfortunately, I don't have one in every city and a folding bike is quite expensive if you only use it occasionally. That's why I made this foldable bike myself! On the website of railway transport of Belgium is mentioned that folding bikes are allowed to ride for free and I couldn't find any size or other restrictions.
Untill now, my DIY bicycle could always travel for free!

The foldable bicycle can also be useful if you want to put it in a car or other small place. :)

The folded bicycle is quite easy to carry at the saddle post (not the saddle itself!), it can stand up alone with the standard stand and it takes only 30 seconds to fold or unfold the bicycle: the only thing to do is loosen the bolt and fold the front wheel against the back wheel.

It's definitly possible to make the steer and pedals (those are for sale) foldable too, but that's not included in this instructable (yet).

Enjoy splitting your bicycle in half!

Step 1: Cut the Bike in Half

First of all, remove the brake cable leading to the back wheel.

Measure the length of the bike from the centerpoint of the front wheel to the centerpoint of the back wheel. Divide this length in two and measure that distance from the centerpoint of a wheel parallel with the ground. On this distance, perpendicular to the ground, the bike has to be sawn in two pieces. Draw a line on the tubes.
It's very important that the sawing is right-angled and straight!

To saw the bike, I used a grinding wheel. It's easy to put the bike on it's sadle and steer while sawing, this gives more stability.

Step 2: Prepare the Hinge

First of all, the hinge has to be big enough to cover the tubes of the bike. In this bike, you have 2 tubes, so I had to use a long hinge. Another essential issue: the hinge has to be strong enough. I used a hinge from a stabledoor.

Draw the lines where the tubes have to come. You can just hold the hinge between the sawn tubes and draw around it. The side of the pivot line of the hinges may not be on the same side as the chain of your bike.

The closure system for my bike is a simple screw and bolt-connection.
Same issue counts for the bolt, it has to be thick enough for strength, I used diameter 12.

In the picture, you see the holes that has to be drilled on both sides. To make sure the holes are exactly on top of each other, close the hinge and drill the two holes at once. When that is done, take the grinding saw and expand the hole on one side of the hinge as you see it on the picture.

Then for the other side of the hinge: put the bolt through the hole en weld it in on the outer side of the hinge.

Now, the hinge is prepared to insert in the bike.

Step 3: Insert Hinge in the Bike

For this step, you need an assistant with steady hands, a welding station and a big pair of tongs.

First of al: make sure all the tubes of the bike are flat and clean, you can do that by sanding or polishing. Sand also the beginning of the tubes itself, prepare them for welding.

Second, clamp the back half of the bike in a vise with the tubes easy reachable and on working height. Then, use your assistant (give him a big pair of tongs) to hold the hinge in the right place. (where the tubes are drawn already) If he has found a comfortable and steady position for the hinge, weld the hing to the tubes.

Then, detach the front wheel of the front part of the bicycle (that's easier to work with). Now the most difficult part: close the hinge and let the assistant hold the front part of the bicycle against the hinge on exactly the right place. Now, welding has to go quite fast, because holding a front bicycle on exactly the right place isn't such an easy job.

When that is done, the entire bicycle can come out of the vise and the front wheel can be attached again.

Step 4: Finishing Touch

FIXING PART

If the hinge is closed, screw a nut on the bolt, be sure to use a large ring inbetween the hinge and nut for the force distribution. I used a standard nut and each time I unfold or fold the bike, I need a wrench. It's easier if you use a butterfly nut, then you can close it with your hands.

BRAKES

Don't forget to re-connect the back brake!

PAINTING

With the welds and hinge and bike parts all in different colors, it doesn't look like the most beautiful bicycle. With a bit of paint, you have a new, nice-looking bike. For a good way to paint the bike, use this: https://www.instructables.com/id/Paint-a-bike-frame...

NOW, THE FOLDABLE BICYCLE IS READY TO USE! :)