Smitty; yeah, we old guys are now lucky in that there must have been women in the "Freeway Rest Stop" planning groups. Seems like a number of stops were later additions in the West.

About your early pipe & valve questions & comments. Here is an unfortunately long comment. I hope none doze off in the reading.

Hallum & I used two small 1961-62 motorcycles, a 50cc Tohatsu & 80cc Yamaha, as very good test machines for many later porting modifications and pipe test. The Anzani port numbers went to the motorcycles and then added carving & features tested went back. At times the large mostly empty Mukilteo public boat launch parking lot across from Loser’s Boathouse was the easy & quick place to test the pipes. We found some odd effects at different tuning ranges. Both moto's raced the short dirt oval tracks too.

Mainly, all that was needed was to learn what not to apply to the Anzani or any of the other motors. We could almost simulate the race boat conditions by making higher gear full throttle runs from very low motor speeds. That gave time to see what the tach was reading as we felt the pipe doing normal or strange things.

We did try various schemes to have pipes be effective over a longer rpm range. I don’t recall that Hallum’s bounce pipes had an operating range that was much different than any others. They did have a strong effect and depended on porting relations for peak performance. Nothing odd there. I will guess that the double pipe for a single cyl. that you saw could easily have been a test set for the 50cc Tohatsu. Dividing the initial pressure wave into two pipes near the cylinder is a problem for returning wave strength. Probably would have done strange things on the Tohatsu, including nasty flat zones and crankcase pressurizing since it wasn’t reed valved. One extra long Tohatsu pipe had 3 nodes where you could feel it “come in” twice more above its start point and wasn’t a strong action pipe either. This was years before the double divergent cone discovery. (Later, Anzani bounce pipe c-case pressurization problems were found when I took a good gage to Hallum for a tank test after seeing a vapor plume out of the Vacturi carb just before the tuned range when at a race).

At that same time for the 80cc Yamaha I built a coaxial double pipe to test for a broad operating range not needing a valve. The arrangement was an outer megaphone set to start about 6000 rpm with a standard expansion chamber mounted internally on center and set for about 9000 rpm. The test was to find out if the outbound pressure wave would divide equally enough between the outer megaphone and the inner bounce pipe. The tapered header pipe ended at about 2 in. diameter. The megaphone was welded to the header pipe. The expansion chamber divergent cone initial diameter was maybe 1/2 inch smaller and was supported downstream from the header pipe about an inch or two. The megaphone angle allowed for the inner bounce pipe angle.

The thought was that the initial shock wave would have its center portion “cored out” by the bounce pipe while the outer portion would flow as an annular ring out of the megaphone and hopefully act normally. The result was that both pipes had their effect but much diminished over what would be normal as individual pipes. The power band covered the full expected tuned range smoothly, had marginally OK power to top rpm, but was well below what either pipe would provide as normal single pipes of either type. Adjustments to change the “cored out” area made no difference. This is why I speculate that the outbound shock wave can be easily disrupted.

The now common two into one siamese bounce pipes on twin cyl. outboards did come after the double divergent cone discovery but that may not be why having half of the header pipe wall fall away at the convergence zone doesn’t seem to cause a large wave disruption.

=== Clear memories from 50 years past seem good, but .... ===
As for the “ram’s horn” -B- Anzani pipes. I recall being there sawing metal for them with Jim at the farm shop. That particular tubing was the initial expanding curve divergent cone portion starting at the exh. port mount plate and ran several segments around the long curve. I went home to make the end cones because I had the right lighter sheet stock. Brought them to the farm as Jim was finishing the divergent section (double divergent by then) and we rolled up the straight sections, mounted the end cones & exit tubes. That is my early memory. Jim built a good aux. mount system made easier by the short length of pipes aft of the motor.

The Anzani -A- motor for record use was already sitting on a rack somewhere with the diverter valve and double pipe setup on each cylinder. I recall Jim making the wood pattern for the first cast diverter valve. I rode along with him to a pattern shop - small foundry of an old friend (Peterson) which was near the Spokane street overpass. Seems like it was a year or more before those castings became operating valves. That whole effort was a serious chore for Jim. I do know that the valved 4 pipe -A- motor was in Walin’s trailer box the year I subbed for Halum as his mechanic at the APBA DePue Nationals and the week later NOA Nationals at Midland, MI. I keep thinking that was 1966. I think that was also the first year of the “ram’s horn” pipes on the -B-.

Both races were very disappointing. Wain said the motors did not seem to have the normal power. Just plain felt feeble but still ran about equal to the other top racers. We didn’t discover the fuel type problem until back at the Boathouse and found that the “sponsored” fuel was not methanol and not nitro-methane. In the test tank the -B- wouldn’t pull the normal load wheel to proper rpm until the “nitro” was added at nearly double their top competition fuel percentage. Jim was very worried about dumping in more nitro so went in steps and hoped to catch problem indications before melting a piston. At something just under 60% nitro, instead of their normal 30% the motor was close to normal power and ran fine. Walin and I had discussed increasing the nitro at DePue after he commented that the motors acted like they were running straight methanol break-in fuel. I think Gerry even called Jim about added nitro but it was simply too much of a risk outside of experience and there was not enough time or extra fuel for testing. Had we tipped the nitro can hard at those two Nat’s the results would have been much more fun.
R.R.
Photo of me wrenching on Walin’s -A- to get at the twisted crank in a Milwaukee parking lot in between DePue and Midland Nat’s. Walin was inside getting a proper OMC recognition for his StarFlite 4 record. Yeah, my travel rig was the ’63 Stingray back then. Nice ride for a Model Maker apprentice. It hauled half a trailer box load of late prepared Anzani powerheads & pipes to catch up with Walin in Minnesota.
Fun times for sure (and a little stretching of the "Reasonable and Prudent" Montana posted highway speed limits).
1966 Wrench-Milwaukee.JPG