'Skin Deep' Ironing out a stretch. DONE!

[The Renaissance Man]

Getting things ready to start fitting the first ironing board leg. Found an online calculator for notching the top tube thanks to @JNOACK 's suggestion (thanks!) that he made to @tjwilson during his build 'Twist of Lemon'.

Because the top tube is larger than the head tube, it will be squeezed into an oval with the minor axis equal to the head tube diameter (32.4mm). All of the numbers that I used in the calculation are based on my best guess at this point but the pattern should be very close and can be adjusted once I actually start fitting the tubes together.

 

[The Renaissance Man]

It took some serious algebra by my wife and son to get the correct numbers for the oval top tube, but after plugging in all of the calculations, the pattern looks like a near perfect fit!

It was interesting dinner conversation last night with the whole family (me, my wife, son and daughter) all discussing equations for calculating the unknown major axis of an oval. It was like being in a conversation with three other people speaking a foreign language.

 

[Glen]

It took some serious algebra by my wife and son to get the correct numbers for the oval top tube, but after plugging in all of the calculations, the pattern looks like a near perfect fit!
It was interesting dinner conversation last night with the whole family (me, my wife, son and daughter) all discussing equations for calculating the unknown major axis of an oval. It was like being in a conversation with three other people speaking a foreign language.

"...all discussing equations for calculating the unknown major axis of an oval."

Sheesh... I just cut the metal then file it until it fits.

Just the word 'algebra' is foreign to me.

I suspect this bike won't be as ugly as you first made it out to be.

 

[The Renaissance Man]

Sheesh... I just cut the metal then file it until it fits.

Just the word 'algebra' is foreign to me.

I suspect this bike won't be as ugly as you first made it out to be.

I would've just 'cut and filed' until it fit also before @JNOACK enlightened me about online tube notching pattern calculators. What an awesome tool! The algebra got thrown in when my initial guess for the oval measurements where off and I asked my math loving wife for help.

The reason for even building this bike at all is to see how certain things are going to work (or not) and that includes making good fitting joints before trying my hand at TIG welding. So even though it's being put together without much regard for aesthetics, I'm taking time to get things fitted as well as possible to learn from the process of building it.

As far as ugly goes, the ironing board legs are going a long way toward fixing it. I had planned to just use straight tubes to connect everything and my initial renderings where very ugly! lol

 

[The Renaissance Man]

I needed a good way to clamp the tubing while I whittle on it. Using two pieces of scrap 2x4 and a piece of 1/8" plastic, I screwed the pieces together and drilled a hole (same size as the tube) down the middle. After the hole was drilled, the plastic spacer was removed allowing some space for the wood to tighten up over the tube. It doesn't have to tighten a lot to hold it. I can clamp the wood to the work bench or put it in a vice etc.

 

[RustyGold]

Excellent!

Jason

 

[The Renaissance Man]

After cutting the tube and fitting it in the jig, it revealed that my guess was wrong on the 42° angle. So I printed another pattern with 44°. More cutting and filing ahead!

 

[The Renaissance Man]

Third time's a charm. It turns out that 45° was the magic number.

The top tube is set. I closed up the rear triangle by a few inches to get a good line on the ironing board leg while keeping the line above the BB parallel with the head tube. That was part of the reason for the angle being off. I wasn't planning to concern myself with such things, but I just can't stop myself sometimes.

I propped up the jig so that the axels are level with each other to get a look at how it will sit when it's done.

 

[JNOACK]

It took some serious algebra by my wife and son to get the correct numbers for the oval top tube, but after plugging in all of the calculations, the pattern looks like a near perfect fit!

View attachment 68713

I'm glad to see that this works, so that I can eventually get around to using some of these things I found online. So much great building going on here, and not enough time for me yet to really build what I want. I will keep watching though!

 

[The Renaissance Man]

To make the larger diameter tube match the head tube, I used a wood clamp to squeeze it into an oval. I had stuck the cut template in place so that I would know where to stop at the correct width.

Here's the wood blocks in action. They worked very well!
The tube notch contour was roughly cut close to the pattern with a saw and then I finished shaping it with a die grinder.

 

[The Renaissance Man]

Both ironing board legs fit great! Ready for some welding.

 

[The Renaissance Man]

Well, I was forced to concede defeat on my first attempt at TIG welding.

I started with some simple plug welding on the top tube (I welded a freeze plug in the end of the tube) but struggled right out of the gate with the thin metal. After burning holes and building up blobs of weld fixing them I decided it was time to punt. It was obvious that this is no place to practice with no prior experience. I'll try again on scrap metal before I completely give up. Baby steps.

Fortunately my cousin (who's welder I was using) was there to take over. He agreed that the thin ironing board tubing was a bit ambitious for a novice so I reluctantly stepped back and watched.

The good news is that it's 75% welded together!

The next step is to locate the seat tube and get it ready to weld in before the frame comes out of the jig for the remainder of the welds that can't be reached yet.

 

[Fv2]

That thin stuff is ambitious for starting, I learned by running beads on flat plates.

 

[tjwilson]

I think you have the tough parts figured out! The tubing notches look awesome as does the fixture. The welding will just take practice.

 

[The Renaissance Man]

It was a little tricky drilling through the top tube but the seat tube is roughly in place. It will have to be extended down to meet the frame. The seat post is holding it up for the photo.

 

[The Renaissance Man]

I got a small reprieve from my welding woes this evening. I tried it again, but this time I used a MIG. Much easier to use.

I'm still a beginner and it's not very pretty, but at least I didn't burn through the thin metal this time! More baby steps.

 

[Fv2]

Those are some good looking welds for a first attempt, we'll done.

 

[The Renaissance Man]

Those are some good looking welds for a first attempt, we'll done.

Thanks for the encouragement. It's still a little ugly to me, but hey that's the theme for this bike!

 

[The Renaissance Man]

Out of the jig and standing tall! Well maybe not actually tall, but standing on its wheels.

It's beginning to look like a bike! ...a long bike.

 

[The Renaissance Man]

Finished!
I took it out for it's (iron) maiden voyage and it rides great! Mission accomplished!

The drop outs are made for a derailleur and are vertical so there is no chain adjustment at all. I didn't have a half link so I had to just ride it loose. Because of that, I was not able to pedal very hard without it popping. Still I could tell enough that the geometry is very comfortable and that was the goal for this build!

Another observation was that it takes the full width of the street to turn this thing around! I don't know if that is common with all stretch bikes, but it's not very nimble.