First build, dual link full suspension

I have heard it said that Tig welding is like playing an instrument. If it is, then I am like that kid at middle school band concerts sweatily screeching his trumpet through some watered down Gershwin. This is my first bike build and it was a real good time. I learned a lot as I am sure everyone does, which is my way of saying “some of it is kinda bad, but hey, I am learning”. Anyway, I just dropped everything off at powdercoat and anodize so now is the time to document some of the process for myself. And others if they mostly want to learn what not to do.

Design: I wanted to design a bike for what I like to do most, which is pedal up for 2-3 hours then kinda scare myself but hopefully not descending some sketchy pirate lines. So basically a mountain bike. I like the CBF suspension, but the geometry has never gotten along with my weird bod, so I adjusted some things to what I hope will make a good setup. The short of it is:
HTA: 64.5 (w/170 fork)
STA (eff): 78.5
Reach: 480:
ST length: 405
CS: 444
Travel (60mm stroke shock): 151 (65mm stroke shock) 161

Linkage Highlights:
Lev ratio

Anti-squat

CAD:

Of course. all of these numbers are contingent upon it being made right. That remains to be seen. Next will be fabrication high(and low)lights

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I forgot to mention that Pax is my fake bike company that I will be building under on here and this will be the Orion. Anyway, back to business:

I decided to make a dual link for my first bike chiefly because I like how they ride but also you have all the bearings in the links which are much easier to machine than frame pieces in my guesstimation. I tried to have no threaded bits in the frame except water bottle bosses as well.

Fabrication took place at my place of work which let me use the knee mill, manual lathe, tig welder after hours. After some course work at Youtube University I got after it.

My first ever tig weld.


Strong start. Didn’t turn on the gas. Also, not technically a weld I guess.

It technically got better, but not by much:

Little by little

I made the front and rear triangle jigs out of some Mic6 and aluminum extrusion my work was recycling. The mic6 was really precise and flat but my skill with welding is low enough that it made the tacks really hard to do. I will have to account for that in the future.

Front triangle jig with HT and BB:

Rear triangle jig:

In design, I spent about 10 times the time designing the rear triangle compared to the front. And I still designed a rear that was hard to make. It took me about 4x the time to weld up the rear and it was sloppier than I would have liked.

The 2 triangles welded up

Reaming the pivots after its welded up.

3D printed links fit up. It all went together nice. The tires and cranks clear and the brakes even fit!


Links courtesy of PCBway. I bored the bearing holes though, so I technically helped.

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Some things I learned that I wanted to record:

I would like to use Oshcut instead of Sendcutsend for some of the 4130 plate. I sized down to 1.6mm on some plate that I wanted to have at 2mm but SCS didn’t carry the thickness I wanted at the time. I didn’t know about Oshcut and would have rather used their 2mm plate. Hopefully my bike doesn’t break too soon.

I need to practice a bunch more with welding. If I had to give myself a welding nickname it would be “The Big Dipper” or “Hot Hot Heat”. I did a lot of tungsten grinding and lot of overcooking joints.

I need to limit tight angles. I made a bunch of really tight angles in the rear triangle and it just made things hard.

Fixture every floating point in your jig when you tack

Practice brazing. I made a real mess of the 4 water bottle bosses I brazed. I did like one practice braze and I should have done more. A lot more.

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Good job. Never ridden a CBF, but I have modelled a few and I like the numbers I can get. What tubes did you use?

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This thing is pretty rad! Dual link bikes are where its at. I wouldn’t worry too much about the 1.6mm plate, just keep an eye on it. It should let you know if its about to go.

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Thanks! DT is 38.1x1.2, TT is a butted tube. 31.6x(.9x.7x.9). ST is 35mm butted to 1.6 at the top and .9 at the bottom. CS and SS are 19x.9. The rear triangle big plates are 4130 .125" thickness.

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Thank you! I love your builds, @Kitchen

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That is one hell of a first bike! I like the use of plates for the pivot mounts. Similar to the last bike I built. I’ve started learning tig several months ago and I can relate to the troubles you come across. Someone else said this before me but sometimes I need to sharpen my tungsten again before my bench grinder even stops spinning. All part of the process.

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I love your build- it’s awesome! Thanks for sharing what you learned; I didn’t know about OSH cut, and I had never thought of using plate for pivot architecture. It makes a ton of sense; Rocky Mountain used it to good effect for a long time!

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Thanks! Time will tell if it holds up. If it doesn’t, I’ll replace the plate with thicker stuff. The plate pivot points were easy to fixture, and it was nice having them a little undersize then reaming after it was welded.

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I like this. Looks like tube chassis drag car stuff. 2 very enthuisastic thumbs up!

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Great work. Digging the flat plate usage.

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