Thursday, September 24, 2009

Let us "B-gin!"

So the last major hoop to jump through was repairing/replacing the exhaust flange on the Polini cylinder, and fabricating a new header to fit the enlarged exhaust flange. The old & standard exhaust flange dimensions are 22mm outer and 17.3mm inner diameter. The new flange is 23mm ID & 25mm OD. I used pieces of a random exhaust for the new flange and a stock Sachs exhaust to fab up the new header. To accurately recreate the standard Vespa geometry and location, I built a cardboard jig, and used that to accurately sculpt the new flange to fit the old cut marks. Immediately after this was complete, I thought of a faster and more efficient way of doing this. I required a no-bake cookie to console myself.

I then chopped up the Sachs pipe to fit the new flange, which was kinda complicated. When I suspected I was finished, I took my cobbled bits over to Phil's place, where he proceeded to 'turn hellfire into horsepower'©. The flange welding was a piece of cake, but the header geometry I developed was flawed. I took it apart for another go, then back to Phil's where I welded it myself and am ashamed to say, did some Gawd-awful welding. -And to think of the many hours I welded away in CCAD's nearly vacant metal shop. whatevs. So then I rented an enormous angle grinder and fixed all my sloppy blacksmithing on the roof of my building where I undoubtedly made all the babies in the neighborhood wake-up and cry. In your face, infants!

That night I bothered to actually read the section in Graham Bell's book on exhaust headers and through no planning on my own part, the header looks pretty good on paper. It seems like there is tons of power hiding in the nuances of header design. In warfare, military commanders use the expression: "Amateurs study tactics, professionals study logistics" I think the application here would be: "Amateurs study porting, professionals study headers".

Thrice returning to RJ's weld-o-rama, Phil expertly welded the improved header to the Simonini pipe. Thanks Phil! I'm still waiting on various parts to arrive, and it looks like my flywheel will be fat and heavy for the race. But the bike should be together lickitty split and none too soon. I take back any fence-sitting or half-heartedness towards the paint job, it is f**king magnificent and indeed, Louder than God.

In totally unrelated news, Liz & I have been going to Quiz Night at a bar and kicking so much ASS! we've won the MF'er two weeks in a row now, usurping the reigning champs after several weeks of less than glorious performance. BOOM!

Stealth Pics: (cardboard seat is a mock-up, I assure you)
Bonus Round: I'm looking at this blog, while taking pictures to be used on the blog.





7 comments:

Philip Patrie said...

Now lets paint your leathers!

Ian T said...

i am happy i might actually see this bike run. also, you write good.

spookytunee said...

man that paint job is sooooooo fly!

Trina said...

oh... I had no idea it was so colorful.

Wadowski said...

Are you planning on re-bracing the subframe since you hacked the bottom out of it? Are you worried about its structural integrity?

Josh said...

Yep. I will be bracing the subframe where I cut it out.

Wadowski said...

Sweet. Looking forward to seeing more. Been enjoying following this build. Super sick stuff man.