I have given some thought to the idea you
mentioned. I am not certain what the results would be. Here
are some thoughts on the topic.
The two primary tubes would create intake
pulses every 60 deg rotary (or 180 deg e
shaft) revolution. Same for the secondaries.
The primary and secondary of the same rotor would be near simultaneous
in sucking air. So those two pulses I would think tend to
reinforce each other. Now the pulse theory states that when
a FAW pulse hits an "Open" (relative speaking) it reflects an
opposite wave back down the tube. So if a "negative" pulse hits
the TB opening, then it would reflect a positive wave (helping to
push the air toward the intake). However that wave could be
opposing the following set of pulses which it could interfere
with. So would have to do some calculations to see how long the
manifold would need to be at some rpm (high I presume) such that the
positive reflected wave would reach the intake port area in
time to help shove more air in - before running into the
next pair of pulses in the tube.
No! No! no more manifolds (at least
not this summer {:>)) Well, maybe a few
calculations.
Lets see - at 6000 rpm the rotation period
of the rotor is 60/2000 = .03 sec = 30 millsec. 6 pulses
created(one for each of the 3 faces *2) during each revolution so
we have 30/6 = 5 millisec between each pulse sets. If you assume
sea level speed of sound approx 1100 ft/sec, then for a pulse to be
generated by the intake opening, travel to the TB and back to the next
set of intake port openings would be approx .005* 1100 = 5.5 ft. or 1/2
of that for length of runner (trip one way and trip back) = 2.5 ft or
apprx 29". But that was at 6000 rpm and 1100 fps.
For 7000 rpm 60/3500 = .017
sec. .017/6 = .00286 sec or 2.86 millsec. .00286
*1100 = 3.14 ft or 1/2 of that would be 1.5 ft or 18" for a runner
length, at least if my math is correct. This is only an
approximation but should give you an idea of lengths.
Ed
----- Original Message -----
Sent: Sunday, May 08, 2005 1:07
PM
Subject: [FlyRotary] Re: 4-port
intake measurements
When I
combined my primary and secondary on one of my intake designs I used a
1.75" dia tube, so sounds like your dimensions closely
agree. I currently have a 1 1/2 and 1 1/4 for the secondary and
primary respectively. So that gives me a total of 2.99 sq inch
runner area per rotor. So approx .45 sq inches more per rotor than you
currently have, so I would say your current design could be
restrictive.
Thanks Ed, That's pretty much my
conclusion too. While it's certainly making good power,
it could clearly be better, so it's probably worth the hassle of
making another intake.
I'm
not sure if we ever cleared up this business about whether you
need a single TB big to allow for both rotors, or just one at a
time. That was at the heart of the Ellison debate.
Interestingly, if you add the sizes of the ports on both rotors,
it comes to an equivalent tube of about 63mm ID, which is right in
line with the recent discussion of TB
sizes.
Here's another wacky idea for your
entertainment- I'm familiar with the scavenging concept used in
exhaust systems. For one bank of a V-8, you
start with 4 pipes, then combine them to two bigger pipes, and
finally one even bigger pipe. The thought is
that active flow from one pipe is creating a suction on the
others to help pull out exhaust of a cylinder that's almost done with
it's exhaust cycle.
Will this work in reverse? It almost
seems like it would to me. What would happen if you start
with two primaries, and two secondaries, then combine them to
make two larger pipes (one for each rotor), then combine again for a
single larger pipe with a TB on the end of
it?
Cheers,
Rusty (more power Scotty)