(MBBO#6 Class 2) Twist of Lemon

[tjwilson]

Glad to hear the derailleur set-up won't be a show stopper. On a concept as wild as this one, I'd suggest an IGH just for simplicity's sake. Pull this off and the headaches you went through won't go unnoticed.

An internal gear would definitely simplify things but, guess I just have a weakness for the old derailleurs. The chain noise and klunk with every shift reminds me of the Varsity I had as a kid. Never fails to bring a smile to my face.

 

[tjwilson]

Do you use MIG? I'm not a welder, but everything I've read and watched on bicycle building suggests that tig is more accurate and cleaner. I appreciate the vote of confidence. I will continue to watch and learn from your builds. Keep up the amazing design, building and documentation. It's all a treat to follow.

Wouldn't call myself a welder so much. I mean there's welding and then there's Welding. I've seen images of weld beads online that are works of art in themselves. I do use a MIG welder, wire feed with a CO2/Argon gas mix. From what I've also read TIG absolutely offers more control. Especially with limiting the heat affected area. A real advantage when working with thinner materials. I got into welding wanting to build monster machines for Burning Man. Didn't really need the accuracy and the MIG machine was considerably cheaper than a comparable TIG. Had no idea just how much I'd enjoy it. For the .049" to .065" mild steel material I'm using MIG does the trick. But yeah, there is a little voice in the back of my head that keeps saying, "You should probably take a TIG class!".

 

[Chad T]

Looks like another great one. Was amazing watching last year's build come to life.

 

[johnp.smith]

Glad to hear you're going to finish. Really love the fork selection and tire choices you've made. The accessories are making it look like a fun ride for sure.

They are what I had in my stash, the tires go amazingly well together. Both were free. I will have time tomorrow to get it apart

I admire you guys that can design and build stuff like this

 

[LukeTheJoker]

When you going to make a new post on your build? I can hardly stand the suspense!

Mine wont be anything special this year, I am still catching up on the garden that got left alone over winter and tiding my work area, so there may be progress soon.

 

[tjwilson]

Rolling Tubes

Capped one end, packed with sand, and capped the second end of the tubes. The sand keeps the tubes from deforming too much when going through the roller. I used duct tape for the one inch tubes and welded caps for the three quarter inch. When welding the second caps I made sure not to completely weld shut the ends to prevent pressure from building up within the tubes. The three quarter inch tubes are all duplicate bends so I welded these together in pairs.

Tried a couple new tricks that seemed to work. It has always seemed like a battle to try and keep tubes from twisting when I've run them through the tubing roller. This time I ran a straight line along the tubes so that I could catch the start of a twist sooner. Also made a template for each bend so I didn't have to continuously pull the tube from the bender to check the curve. I have no idea why it has taken me so long to think of that!

One Inch Frame Tubes

I needed to put a bend ninety degrees to the first bend in the chain stay tubes. I first ran the tubes through the roller parallel with each other to get the sweeping curve front to back. Then I split the tubes, laid them down ninety degrees and re-welded them together side by side. Using a roller from a hydraulic bender I was able to push the tubes far enough into the tubing roller to get the second bend. The tubing dimpled a little on the inside of the bend but that shouldn't be too noticeable once the stays are welded in place.

All the Frame Tubing Complete

 

[tjwilson]

Starting The Frame

I rough cut the down and seat tubes to length and then fit and welded up the bottom horizontal tube.

Bottom Bracket Post

I've tried using a tubing notcher in the past but have never had any luck. I usually end up breaking all the teeth off of the hole saw. There are probably better ways but, this is the way I do nearly all the joints I make. [starting from top row, left to right]... Roll paper around the end of the tube that will be notched and press that into the joining tube. Trim the paper roll at the crease lines created. Mark cut line on tube using trimmed paper roll with marker. Cut / grind / file notch tube. There's usually a bit of back and forth trimming the paper roll and notching the tube to get a tight fit.

 

[tjwilson]

Head Tube Details

I created the head tube from .065" tubing. The inside ends were filed and sanded to fit the diameter of the bearing cups.

Frame Pieces in Fixture

 

[gowjobs]

I feel like the rest of us are competing for second place. That's fine by me - I'm really excited to see this thing come together.

 

[Southfield10]

This completion needs a 3rd category called "Pro" or something. Wow - the engineering and fabrication skill sets are off the charts here.

 

[CRASH]

This completion needs a 3rd category called "Pro" or something. Wow - the engineering and fabrication skill sets are off the charts here.

I agree. I'm just amazed at the engineering of this! I'm glad I'm only in lowly Class 1 this year!

 

[LukeTheJoker]

Looking awesome!

 

[tjwilson]

@gowjobs , @Southfield10 , @CRASH , @LukeTheJoker
Thank you very much for the compliments and encouragement!

 

[tjwilson]

Rear Dropouts

I refined the dropout shape a little to match the actual tubing bends and transferred the outline to 3/16" thick mild steel plate. Shape was then cut out using a cut off wheel, drill and grinder disc.

Seat Cantilever Tubes

I wanted these tubes to visually flow as much as possible down into the front fork. I capped and ground them off round for a finished end. Then I tacked them in place as far forward as I could. The arched tubes from the rear dropouts will connect and blend into the bottom of these tubes.

 

[deven_science]

Great job so far! Instead of drawing a line down the tube to watch for deviation, I just make sure the weld seam on the tubing is straight up. Works the same way, unless you're using seamless tubing.

 

[CRASH]

Great job so far! Instead of drawing a line down the tube to watch for deviation, I just make sure the weld seam on the tubing is straight up. Works the same way, unless you're using seamless tubing.

How did I know you'd sniff out the scratch built entry? lol

 

[JNOACK]

Starting The Frame

I rough cut the down and seat tubes to length and then fit and welded up the bottom horizontal tube.

View attachment 62699

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Bottom Bracket Post

I've tried using a tubing notcher in the past but have never had any luck. I usually end up breaking all the teeth off of the hole saw. There are probably better ways but, this is the way I do nearly all the joints I make. [starting from top row, left to right]... Roll paper around the end of the tube that will be notched and press that into the joining tube. Trim the paper roll at the crease lines created. Mark cut line on tube using trimmed paper roll with marker. Cut / grind / file notch tube. There's usually a bit of back and forth trimming the paper roll and notching the tube to get a tight fit.

View attachment 62702

View attachment 62703

Have you tried using one of the tube notching programs online? They will let you insert measurements for your tube size and angle and then print out the paper profile template that you can use to mark cuts on your tubes. I've never tried it, but I watched a few youtube videos and it looks like a good resource.

https://www.blocklayer.com/pipe-notching.aspx

 

[tjwilson]

Great job so far! Instead of drawing a line down the tube to watch for deviation, I just make sure the weld seam on the tubing is straight up. Works the same way, unless you're using seamless tubing.

Thanks!

I had to double check the type of tubing I used. Didn't even think to look for the seam to watch for twist. It was there but pretty faint. If nothing else I could have used that as a guide to draw the line!

 

[tjwilson]

Have you tried using one of the tube notching programs online? They will let you insert measurements for your tube size and angle and then print out the paper profile template that you can use to mark cuts on your tubes. I've never tried it, but I watched a few youtube videos and it looks like a good resource.

https://www.blocklayer.com/pipe-notching.aspx

I haven't but I can guarantee you I will next time around! Especially for smaller angles which I've struggled with using the "rolled paper method". Great link, thanks.

 

[tjwilson]

Haven't had access to a computer that I could download camera images to for a while so I've got a bit of progress catching up to do!

Frame Additions

Lower cantilever tubes and chain stays.

Frame Center Joint

It has been "interesting" trying to get all the different tubes that meet in this area to connect and flow together. A lot easier to draw than actually fabricate.

Trimming the frame's rear vertical tube and fitting the cantilever connector tube.

Side sweep pieces.

Sweep tubes welded / tacked in place.