Update on 29er building process

The 29er frame is now ready to roll once the chain-stays / seat-stays reinforcements have been welded plus disc caliper mount.

Now we just have to make our minds on components and paint and off we go!

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Chapter 4: welding.

Here is where the good and bad stuff happens, you either get ur bike ready to roll or a pretty costly piece of junk, all depends on the quality and stiffness of your rig, the accuracy of tube alignment and of course the skill of the welder, among many other factors that in most case you are not even aware of until the worse happens...

To put things in perspective, the welding technique we used was TIG (Tugsten Inert Gas). That´s what the welder recommended since the metal was is so thin than with any other technique the risk to blow a hole while welding was too big.

Here are the results after the first welding session. We´ll have to take it back for some stays reinforcements to be welded and some filling to be done, but the bulk of the job is done now!

Dropouts. Still needs some filling for extra reinforcement.

Seatstay - Seat tube.

Bottom bracket.

Head tube.

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Chapter 3: IT MUST BE STEEL! it always was...

After a little chat with Javi "Piulo" Mr. welder we were informed that the wooden rig that we so carefully had put together was no good for welding. The tensions generated by the weld would easily moved out of position the bike tubes.

The only way to go was to build a sturdy metal frame that would hold the tubes in place no matter what.

So that´s what we did, we got 2m of 40x60cm steel profile and a good bunch of bolts and nuts and we set to design an awesome metal rig!

Since you must be able to extract the frame after welding, the structure had to be able to be disassembled.

It can be seen in the pictures how we designed several slots that would allow us to extract the frame after it had been welded.

Structure supporting the dropouts, chainstays and seatstays.

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Chapter 2: Tube mitering and bulding a rig.

I recently purchased a set of Columbus Zona high strength steel bike tubing from Hillbrinck up in NSW, and after setting my mind on the design, the next step was of course mitering all the tubes so they would match each other nicely. Since I don´t have a set of crown saws I have been using the freeware Tube miter which is simple as, but most useful! I recommend to check it out if you are into this stuff. This software allows you to enter the diameter of the tube to miter and the angle to meet, and it creates a stencil that you can position on the tube. Then is up to your grainding skills to get it right.

In order to get a good guide of where each tube should be sitting with respect to one another I printed a 1:1 print of the dessign and I put it on top of a sturdy wooden board.

As locking points I used an old bottom bracket to fix the BB tube to the board. To fix chainstays and seatstays I used an old and rusty rear hub which will give me the perfect separation between dropouts plus sets up the right distance for the stays.

Each tube is secured to the board by 2 allen screws which push from behind the board and a metal zip tie (plastic ones will melt when it comes to welding!). This way we have two points to regulate the heigh of each tube.

One 0f the most complicated steps is to position the right chainstay and seat stay since they extend underneath the guide board, therefore a hole had to be cut into the wood to allow the stays to go through, this however makes it easier to be secured onto the rig and therefore allows for a more stable joint that won´t move when it comes to welding.

Next step will be to position and secure the right seatstay.

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Building a steel 29er MTB. Chapter 1: Design

So I´ve set myself the goal of creating a bike from scratch, i.e. right from cutting and welding the tubes.

I´ve choosen a steel 29er single speed.

No chance of getting anything right unless you know exactly how and where you are going to miter your tubing.

So step 1:

Cad design: CAD was used software to get all the geometry right and this is the result:

The selected tubing is Columbus Zona, which should end up making a under 2kg frame on a size 19". Next step is to miter all this tubing so they match each other! easier said than done...

Wanga reinforced

Finally a decision has been taken about what to do with the Wanga damaged frame, I took it to the guys of Grip Sport and it's on their hands to weld a sleeve of 2mm steel around the kinks. That should keep away any expansion of any cracks without increasing the weight too much. I'll probably get it back in a couple of weeks and after that a have a single speed setting in mind that will be worth checking! For the time being here is a little modelling image of how the frame should look like, check the tiny increase in tube diameter around the lower diagonal tube and also around the section closer to the seat tube of the horizontal tube.

BTW this one will be professionally powder coated black with metal sparkles...

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How much more can the wanga give?

Can a vandalized steel frame be riden normally again for MTB use with confidence? Nobody really wants to be wondering whether the frame is going to snap in the next jump. That will surely affect your confidence and therefore your riding performance.

To through some light to this question I've modeled a 3D version of the frame and run a couple of finite element analysis. It looks like there is no maximums or critical points were the damage happened, however I'm going to get it checked by a professional frame builder so we stay on the safe side and quite possibly get it fixed or reinforced somehow.