UPDATE: dateline January 24th 2012.
These pipes are no longer produced or sold. I very much enjoyed working with John over at Economy Cycle, but time constraints and lack of profitability have caused me to cease production. (If you bought a set, congratulations, you now own a set of very rare chambers!)
I have decided to make the design available in PDF format (for print and cut) and DXF format for laser, plasma, water-jet etc. Purchase will include drawings (templates), dimentions, detailed materials list, and sources.
By purchasing you agree to the following terms (limited use licence)- Information to be used for yourself only. Not to be used for commercial purposes. Not for resale. Not for electronic or manual distribution. Sharing of the data/design is strictly prohibited. Single use (build) only. You agree to not hold me liable for anything incidental to your purchase of the design, or the building/use/ownership of the product produced by building the design or any variation of the design. You agree that chambers produced using the design and adhering to the majority of the designs features are to be called Vanguard Pattern Pipes, not simply Vanguard Pipes or Vanguard V1’s. Substantial modification of my design need not be referred to as Vanguard Pattern Pipes (this term has the intent of keeping the original pipes I produced distinct from any not made by myself). Terms and conditions subject to change at any time without notice. Furthermore, purchase/use of the designs constitutes your acceptance of all the terms and conditions above.
The basic design is for the Yamaha RD350, that said, the design may be a useful starting place for someone interested in producing their own pipe/variation of my design.
Purchase full drawings PDF/DXF, parts list, sources for only 39.99 via paypal. Please allow 7 days for electronic delivery. Please don’t share the plans. I invested hundreds and hundreds of hours and many thousands of dollars into the research, design and fabrication of these pipes.
I hope that this Blog/tutorial on how to make these pipes has proven useful to you. If you have enjoyed learning about how these pipes are made, please consider purchase of the plans (even if you don’t plan to build a set) purchasing the plans can be seen as a thank you to Vanguard for making information available to you and the world!

I can be reached at natefoerg@gmail.com if required.
UPDATE END: dateline January 24th 2012.
I have been building expansion chambers for the past 7 or 8 years. I started with mild steel pipes for single cylinder medium displacement engines and eventually moved into producing stainless chambers for the Yamaha RD350.

Vanguard's V1 Expansion Chambers.
In this post, I will be detailing the construction of my chambers from start to finish complete with pictures. I will not delve deeply into the design of the chambers, as their are many other sources that cover how to design a chamber for a particular engine/riding style.
The chambers are for sale at Economy Cycle http://www.economycycle.com/servlet/the-397/V1-Expansion-Chambers-by/Detail

Not just a peak, a plateau!
For the past several years most of this info has been kept close to the vest. Today I am revealing most of the tricks of the trade…
The bill of materials for building these pipes is as follows .250 stainless plate for the header flanges, 2 sizes of stainless tubing for the header stub and the header overlap tube, tubing for the stinger, aluminum tubing for the silencers, perforated metal for the silencers, aluminum caps for the silencers, 2.5 OD thick stainless washer for the stinger mounting flange, stainless (mill finish) sheet, silencer packing material, neoprene washers, stainless springs, nylon washers and misc. stainless hardware.
From header to silencer, heres how they are made:
I started with hand cutting the header flanges for my pipes, but this was very laborious. I ended up having them laser cut from .250 thick plate. the flanges are then hand drilled and chamfered for the spring holes. The laser cut flanges look and fit very good.

Flanges before finishing operations.
Spring mount holes are drilled/chamfered, pre-cut header stubs are tacked in place and finish welded .

Flanges in progress.

Finished flange.
Now that the flanges are done, its time to move on to rolling the header pieces and massaging them into true roundness.

Most of the parts/materials for a set of pipes. Note the header sections laid out flat.

Each one of these pieces was rolled, then tacked, then rolled again and finally trued by hand with brass hammer over the tube suspended between v-blocks.

After straightening with a brass hammer and tube mandrel.

Header building general overview.
The headers contain 20 sections, the last 13 of which are tapered.

A close fit is very important.

Tacked and ready for finish welding.

Lots of tedious welding.

The tedium is beginning to pay off.

I don't do any finish welding without a full Argon back-purge. No "sugar" in my welds! Here is the Argon back-purge setup. Runs from a second Argon tank/reg unit.

Fully welded headers.
If the welding in the picture above looks like it takes a fair bit of time, your right, it does. Two headers takes me over 2 hours of finish welding. If you add rolling, hand forming to perfect roundness and fitting/tacking, the time for a set of headers jumps to around 6 hours. Now you know why most makers use tubing or hydroform their headers!
On to the body of the pipes:
Originally, I cut and formed my own header sections and cones. I still form the header sections on a slip roll and hand true them, but I now have the cones cut and welded by a company that specializes in this task. They are not cheap, but its the age old, time-or-money equation, and for me, forming the cones is so laborious that farming out the task was worth it. If you have ever tried to bend/roll a 20GA stainless sheet thats 18″ long into a cone, you will see why I hire this part out.

Cones ready to tack.

Cones tacked and belly sections tacked in also.
The belly sections above are 4″OD and do NOT want to stay round. Look in the upper left of the picture and you can see the slide hammer attachment I use to force the belly sections round as I tack them in place.
Another pic of the slide hammer round-forcing-tool:

Special forcing tool.

Tacking and welding the cones with Argon back-purge.

Extreme care must be used to keep all the parts in alignment.
Next, with great care the parts are tacked to each other. Keeping the cones and belly sections true during tacking is VERY difficult. The fit-up required to be able to “fusion” weld (welding without filler rod) with 20GA SS is very hard to achieve. All the parts must continually be massaged with a rubber mallet into “true” so that no gaps or out of roundness occurs. Any gaps will create BIG problems. Gaps will get bigger and melt away as the arc runs over them. Putting metal that has melted away back where it needs to be is not easy! I make every effort to get my fit-up so good, that only occasionally do I need to use any filler rod.
A weld done without any filler rod is smoother and better looking than one done with filler rod. My welds polish up beautifully.

Looking aggressive.

Argon Purge while finish welding.

Putting it all together. Note some pre-polishing was done on this set. Once fully welded, they are quite a pain to polish.

Getting the stance and alignment correct.

Looking like pipes now.
At this stage, the alignment having been verified, the Argon back-purge is setup again and the pipes are finish welded.
Stinger tubes are welded in and the flanges for the silencers are aligned and welded on.
Heres a shot of the tooling I use to bore and drill the 2.5″ SS washers that become the flanges.

Washers and special tool.
The washers are first drilled while held in a set of aluminum softjaws and then bolted to the tool for boring.
The softjaws are also used to drill mounting holes in the silencer caps.

Modified softjaws and special tool.
Silencers are made as follows:
Cut body tubing to length, machine endcap slugs to size, cut and roll perforated metal, assemble and drill and tap 9 holes per silencer.
A neoprene washer is hole punched for mounting screws and goes between the silencer mounting flange and the silencers.

Custom cut Neoprene washers.

Silencer endcap slugs before finish machining.

Silencer body's and endcaps being checked for correct fit and finish post machining.

Completed silencers.
At this point, spring mounting tabs are welded to the headers, header stubs are finish welded to the headers, footpeg mounting tabs are welded to the pipes and everything is assembled and checked for correct fitting and alignment once more.
Everything is then disassembled for cleaning and polishing.

Red carpet treatment!

Nice and shiny!
That’s the nuts and bolts of the process I use. There are countless other steps required that I did not have any pictures of, the most notable of which is the lathe work that is done on the header stub and the piece that welds to the header that is a slip fit over the header stub. Machining on several parts is needed to create the fit that I require.
All in all, many hours and lots of money go into each set. They were conceived as a project for myself, more of a personal challenge, rather than a product for market. Had I designed them for the market, they would have been MUCH simpler, especially the header.
The results:
43 peak horsepower and a spread of 40+ HP between 6850 and 8250! Most available pipes will give you a high number, but a high number is fairly useless if it peaks and then rolls off again. My design keeps the power over 40 HP for a 1400 RPM spread, and over 35 HP for a spread of 2600 RPM!

Power spread.
This chart is from a motor that is running stock port timing/widths and without a widened exhaust port. The transfers were flowed at the transition of the cases and the bottoms of the barrels, the case transfers were matched, the exhaust port had the rough casting cleaned up, corrected squish and is running banshee reeds. 1.8mm timing on Newtronics. Stock carbs.
Not too bad for a motor with stock port timing and widths.
FAQ:
Like this:
Like Loading...