Titanium bullmoose handlebar build diary
 

I'm a bike mechanic and metal fabrication student. Later in the spring I'll be fabbing an aluminum (Nova/Easton tubing) MTB/bikepacking frame as a school project. Right now I've decided to make some titanium bullmoose handlebars for the bike because I want to get some experience TIGing titanium.

I haven't found any good guides or threads on making ti bullmoose bars online so I figured I would make a build diary. If y'all have any input or advice please feel free to post it here as well, as I am an amateur!

I'll start with the design.

Here is a rough sketch of the handlebars, top and side view:
https://c1.staticflickr.com/1/516/32...a54f7fc8_b.jpg


I chose the bullmoose design for a few reasons:

1. I like the design aesthetically and practically. Multiple hand positions and plenty of surface area for accessories.
2. Ti tubing of this diameter is pretty flexible compared to steel so having two "stems" in a diamond shape should stiffen up the bars a bit and keep things strong.
3. Doing an integrated stem/handlebar combination means I don't have to worry about getting tubing with a variable OD (outer diameter). MTB handlebars need a 22.2mm OD grip area and a 25.4 or 31.8mm OD for the center stem clamp area, so I would have to make or find tubing like this, which would very difficult. A lot of people who do custom handlebars like this use a shim for the stem clamp area, which seems like a fine solution, but I wanted something a little simpler. Because I'm welding the "stems" to the handlebar, I don't have to worry about a clamp area.

I'm hoping to get a 3D SolidWorks print going of the handlebar but for now I just have sketches.

Tentative specs:
-6deg rise of the "stems" from the steerer clamp.
-Handlebar tube is rotated 10deg up from the level top of the steerer clamp. This is assuming a 70deg head angle on the bike.
-710mm handlebar width
-15deg sweepback to the grips

I'm thinking about adding more sweepback to the bars, somewhere around 30deg. Also, if anybody has any input on how wide to splay out the "stems", I would appreciate it! I have them pretty wide right now but I haven't put much thought into it.

Have you researched the Jones bars for geometry? Andy

Materials

I ordered 6ft of 0.875" OD tubing from a surplus Ti company in Ontario called Titanium Joe. 0.875" is 22.225mm, which will work for the grip area. The wall thickness is .047", which is pretty thin but probably not as thin as I could go, but I want a little bit of thickness to help with the welding and stiffness. So I won't need to modify this tubing at all to use, except for cutting it to length, obviously. The handlebar and "stems" will both use this tubing.

I also ordered 6" of thicker tubing (1.3" OD, 0.15" thick, 1" ID) for the steerer clamp. This will go on a 1 1/8" steerer so I will have to use a mill or lathe to open up the inside of the tube an 1/8". Hopefully the remaining 0.175" wall thickness should be thick enough for a steerer clamp.

The tubing is 3AL-2.5V grade titanium.

The handlebar will be one piece. I will bend the tube to get the center angle. The stems will be welded on each side to the handlebar and the steerer clamp.

Here's that 6ft tube. Got it in the mail a couple days ago.
https://c1.staticflickr.com/1/548/31...63b8b942_b.jpg

I really like the Jones Bar and have ridden it a bit (we have a floor bike specced with it at my bike shop). While I do not want to do all the bending that is required to mimic Jeff's design, I do like the extreme sweepback and so will probably increase the sweepback in my design.

Equipment

The fabrication processes I will be using to make the handlebar are cutting, notching, bending, welding, and milling. I'll focus on the bending and welding, initially.

For simplicity, I am designing only one bend into the handlebars, in the center of the handlebar tube, to achieve the sweepback of the grips. The fab shop at my technical college has a Hossfeld bender, which I'll be using to bend the tube. It looks like a medieval torture device but is a really useful and flexible bender. It uses a swing arm and detachable dies to bend the tubing, and can be used manually or with a little engine if the stock is too hard to bend by hand:

http://www.hossfeldbender.com/stock/figure29web.jpg

Our welding shop has a bunch of Miller Dynasty power sources for TIG welding. This will be low amperage because the tubing is thin, and you only need DCEN (negative polarity) for titanium, so I don't really need something this fancy but it's what we have.

Titanium needs to be very clean and very shielded during welding. Any dirt or grease, as well as oxides, can easily contaminate the weld and cause weld failure later. Ideally I could weld this in a purge chamber, but I don't have one. So I will need to clean the metal meticulously and use a champagne nozzle and gas lens on the TIG torch to get the widest shielding gas coverage possible to protect the weld and heat affected zone (HAZ) from the atmosphere. I will also probably want to put up some sort of screen to protect from any drafts that might blow the shielding gas away.

I ordered the proper 1 1/8" nozzle and gas lens kit yesterday and it should arrive next week. The nozzle is made of pyrex and is clear, which will help with visibility when welding. I will probably be using a 1/16" size tungsten electrode.

https://c1.staticflickr.com/1/476/32...b25d0be8_b.jpg

A couple of points from a non TI guy. First I suspect a numeral slipped in the dimension of clamp tube. Maybe a 1.475" OD? Next is the bending. I've read that TI is far more challenging to bend then steel. I also know that with small diameter steel how you clamp the fixed end and how you apply the bending pressure speaks to how smooth and symmetrical the bend is. Lastly is the common internal purging/shielding while welding. To not do so will open your joint up to possible hydrogen embrittlement.


I suggest that you do some experiment/practice under the wing of an experienced TI guy. Andy.

What's wrong with the numbers with the clamp tube?

As to bending - the Hossfeld should be able to take care of it. With the Hossfeld there is no need to fix one end - the whole tube moves freely while it is pulled over the die, so kinking shouldn't be an issue.

That's a good point that I forgot to mention about purging - we will have an argon purge set up to handle the inside of the tubes.

I do have a couple of instructors who have worked with ti so I will be making sure to consult them on everything I do re: welding. It's a good position to be in! I also got plenty of extra tubing for a practice run or two.

1.3" OD minus a 1.125 ID gets you a .0875 wall. You forgot to divide by two as there's two walls at play here.


As I said I'm no TI expert but when I read of such confidence from a newbie I take pause. There are builders out there who likely don't take part in this forum that you might want to approach off line for advice. Andy.

Oh yes, my mistake on the final wall thickness for the steerer clamp. It is .0875".

Finishing up a small jig to get the angles right. Just have to add some guides on the slope for the "stems".

https://c1.staticflickr.com/1/447/31...ac4e3cbd_b.jpg20170130_105752 by Etan Heller, on Flickr

neat thread, thanks for posting. I have thought about bending some bars. I don't weld Ti, so I would just use a regular stem and the Paragon adapters.

Looks cool I 'll take one....if it works make steel and sell a few.. Make sure it offers something different, I bet you will get offers.

It's been a while but finally continued on this project. I cleaned up and added some pieces to the jig, bent and cut the handlebar, and cut the stems today.
For bending I ended up using a pressing bender rather than a pulling bender. We had an Enerpac One Shot hydraulic bender in the back that I pulled out for this.

https://c1.staticflickr.com/4/3940/3...8939f5af_b.jpg

I filled the tube with some steel filler rod to lessen the likelihood of crimping/kinking.

https://c1.staticflickr.com/3/2948/3...74f25752_b.jpg

https://c1.staticflickr.com/4/3855/3...d739fff9_b.jpg

It still had a slight crimp to it but nothing that would have any impact. I got a perfect 30 deg bend by bending it out to about 47 deg. Titanium has A LOT of springback.

Here it is mocked up on the jig. I'll try to notch the stems tomorrow, and then it will just be a lot of cleaning and the purge setup before I can tack it together. That's a Paragon Machine Works steerer clamp (6AL-4V) because I decided I do not have time to machine one before the end of the program.

https://c1.staticflickr.com/3/2886/3...4ac3ed5e_b.jpg

The final design is 60mm forward from the steerer clamp with a 30 deg sweepback and a little more than 780mm end to end.

Did some notching today...

Used a Scotchman grinder notcher. It uses an abrasive grinding belt to notch rather than a drill. You change out the die that the abrasive belt rolls on to get the correct diameter notch. Luckily we had some dies that are close to my diameters (7/8" and 1-1/4") so I got some pretty good notches. Angling the tubes is also easy because there is an angle indicator directly on the vice that is built into the notcher.

Changing to a new belt to avoid contamination:
https://c1.staticflickr.com/4/3842/3...32601e5a_b.jpg

The notcher at work. Ti sparks up white. I had to be very careful not to overheat the tube or put too much pressure on the belt, so it was a bit slow going:
https://c1.staticflickr.com/4/3713/3...554c4cd1_b.jpg

The stems are so small that they could not reach the belt from the vice for the notch for the steerer clamp joint, once it was cut down to size after doing the notch for the handlebar joint. I found a steel rod lying around that I shimmed with a soda can to get the stem extended farther out from the vice while still being secure:
https://c1.staticflickr.com/4/3771/3...6b56f61e_b.jpg

Final fit up is tight on the handlebar but the steerer clamp notch is a bit too small. I will have to do some hand work to get it to fit more snugly because, as you can see, there is a bit of a gap at the joint:
https://c1.staticflickr.com/4/3767/3...55106a6f_b.jpg

I am also thinking of doing 0 deg of rise instead of 6 deg as the bike it is going on has a pretty slack head tube angle as is.

You got the rig to charge both sides of the welds inside and out with inert gas, so the weld is sound.?

Yes, I am going to purge the inside of the tubes. First drilling vent holes in the handlebar to let argon into the stems and hot air out, then a tapered purge hose head fitted into one end of the handle bar and some holey tape onto the other end to push the air out and create a positive argon flow. I will take some pictures of the setup when I get ready to tack.