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)