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New Pipes For The Mad Dog's Black Widow

9K views 30 replies 23 participants last post by  Mad Man 
#1 · (Edited)
BMX kingpin Chris "The Mad Dog" Moeller at S&M BMX solicited my help to make some new pipes for this infamous Black Widow. S&M BMX builds their own high-dollar BMX bikes in their own building right here in the US of A, so we had skills (shop manager Jason Balls, himself a chopper freak of some repute) and equipment at our disposal. Chris and I are old BMX grease monkeys, but we put our heads together and dreamed up a pipe set for his new motor in a matter of hours using only a Sharpie, a piece of welding rod and our (half) wits. Here's the blow-by-blow from last night's shop session:

Step 1: Prep your work area

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Step 2: Make your rough drawing

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Step 3: Create your basic shape with a piece of welding rod

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Step 4: Install your header flange and start picking your bends

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Step 5: Tack your little bends and straights into shape

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Step 6: Assess your progress by installing and reinstalling your pipe as it grows

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#2 · (Edited)
PIPE HOW-TO, CON'D:

Step 7: If you like where things are headed and and everything is clearing what it's supposed to, do some 1/2" long root welds to hold your sub-assembly more firmly into place

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Step 8: With front half of pipe in limbo, assess your design and method of mounting in the rear. Mad Dog didn't like the way his cocktail shakers hung on a giant bracket, so he jetisoned this contraption in favor of some tabs. Yes, those are zip ties Jason is staring at.

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Step 9: Clean up your tube surfaces with a flap disk to make room for new tabs and new welds

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Step 10: Using your pipe sub-assembly as a guide and a jig, determine the location of your support tabs and tack them into place

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Step 11: Finish weld your pipe

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Step 12: Admire your handwork. Repeat for the rear cylinder

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Random stuff we learned along the way:

Not even the clean cut of a bandsaw will leave your tube openings in perfect shape for end-to-end welding.

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When this is the case, massage the tube openings with sandpaper. The more horsepower, the better

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The pipe for the front cylinder took us a little over 5 hours to build, and required some mods to the peg location, and the aforementioned mods to the muffler mounting. We measured three times. cut twice and welded once on every joint. It's better to whittle away a little bit of tube at a time to get your joints perfect than it is to whack off too much tube... taking off is always easier than adding on, especially on tight radii.

Beer actually made this project go faster.

If you're a badass TIG welder like Jason is, you can fuse these tubes together without rod. He did this several times and it looked awesome.

As the three of us proved, anyone with average talent, simple tools and some spare time can make pipes for their bike-you don't need a multi-million dollar bicycle factory at your disposal to do it!

Thanks to Chris for inviting me to his party, and to Jason for being such a good workmate.

I can't wait to see the rear pipe. Good luck and have fun, Mad Dog…
 
#15 ·
BLACK WIDOW PIPES UPDATE: Doing it in the rear

Chris and Jason hit this project hard last night and the finished product looks awesome. Here's some more images from the Mad Dog gallery…

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The butt joint between the Biltwell header flange and the old pipe was perfect. Jason chamfered the tube ends to do a pipe weld. When it's finished, you can see the penetration on the inside of a properly executed pipe weld.

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Here's a closer look at the finish welds on the front pipe. They'll look even better after Dave Bush in OC polishes the pipes and dips them in nickel.

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Two tabs like these-one on each rear stay-secure the P-clamps that hold the cocktail shakers and the pipe ends in one unit.

Two views of the assembled pipes on the bike.

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Note how the S-bend dodges the tranny on the front pipe, and now the cocktail shakers run parallel and follow the lines of the frame's rear chainstay (more bicycle talk.)

Thanks for the kind words. We had a blast doing this project. Can't wait to see them blinging at the Bash April 17.
 
#22 ·
surely moeller would have the RIGHT HAND 101 pedal for his kicker. it bugs me like all those kids that had LHD with flipped profiles but were too lazy to rebuild their pedals so the flats faced forwards!
having a facility like that would be awesome, chris sure has put in for it over the years, good on him!
 
#23 · (Edited)
My brother Kyle (Mad Man, new member on the JJ) built a custom exhaust for his Triumph Saturday morning using the Biltwell exhaust kit.. here is a write up with some pics:

The same principles are used from McGoo's article, including starting at the head (in this case a piece of 1.75" tubing that fits over the exhaust spigot on the head), and working your way back, cutting and tacking pieces of tubing to get the proper angles and curves you want.



This entire set of pipes was completed from start to finish, including the time to figure out a design, in a Saturday morning, about 4 hours not including the final mounts on the rear of the frame for the exhaust. It was completed with a TIG welder, a cut-off saw, 4" grinder, some flap discs, a couple files and a sharpie marker.



Keep checking the fit of your pipes as you go, and as you complete a section you can grind the welds down for a nice smooth finish. Spend the extra time getting proper fitment before you weld to ensure a nice, seamless look.







The right-hand pipe that crosses over the the left-hand side is made of 7 individual pieces. Kyle eyeballed, marked, cut and fit each one with trial and error. He used the shovelhead flanges from the Biltwell kit towards the rear of the pipes to be used as mounting brackets by welding some tabs to the frame, and finished the pipes off with a set of brass exhaust tips.







So with the exhaust kit, some basic tools and some patience a unique set of custom pipes was finished on half a Saturday, with exhaust tubing and a bunch of flanges left over. Kyle's fabricating tip: if you plan on welding all weekend check your argon so you don't run out on mid-day Saturday.
 
#25 ·
One little addition I forgot to put in there:

The spigots on a Triumph head are 1.65" outside diameter, and the inside diameter on the exhaust kit is about 1.64". To be able to clamp the pipes at the head you can just take a grinder with a cut off wheel and cut a .5" notch into the pipe on either side, that allows it to fit over the spigot then compress when you tighten the finned clamp at the head.
 
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