Al,

My plan was to pull from the radiator scoop of the Sam james rotary cowl.  Do you think this area would be pressurized sufficiently at high speeds?  Any significant effect on radiator performance?

Bryan

Before we get too excited about putting leaf blowers under the cowl; you might consider this.  The baseline case here (no blower) is with the plane standing still with at sharp edge intake at the TB – correct? Fairly significant inlet pressure loss for that configuration.

You may get a similar increase in manifold pressure by putting a nice bell-mouth entrance on the TB. And you will get a similar increase in manifold pressure with a ram inlet scoop flying at about 160 Kts.

Al G

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Dennis Haverlah
Sent: Monday, February 15, 2010 7:58 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Air Pump

Bill: 
Thanks to my younger brother who was brave enough (use younger brothers for dangerous stuff) to operate the leaf blower I ran the leaf blower test for the group.  I used a fairly new hand held Echo leaf blower Model PB 251   I "borrowed" from my neighbors hangar. 
Specs - 25 cc 2 stroke,

No information on rpm's at these data points were listed.  I would guess that the 2 stroke engines are operated between 6000 and
8000 rpm. but I'd like to have real rpm data.

Four tests were conducted as shown below.  Local air pressure was 30.2 in Baro. - 0.5 in for 1000"  = 29.7 in hg. air pressure at field elevation.
Weather was Clear, low humidity and 53 deg. OAT.  All tests were at WOT.
Pictures are attached for each test.  Note the 180 deg. bend in the Scat tubing during the (C) test.
The (C) test picture was taken after we had taken the Scat tube but my brother was holding it in place.

Test condition               Static max. RPM      Manifold Pressure        Engine Temp.
(A) Standard intake,               5870                        28.9                    Barely warm
      air filter etc.

(B) W/O air filter &                 5660                        28.7                    Fully warm
       prop blast

(C) Leaf Blower full                 5925                       29.9                     Fully warm
      throttle into throttle
      body - 180 deg turn.

(D) Same as (A)                       5700                       29.0                     Fully warm

It appears that the blower raised the inlet pressure by 1.2 in Hg. and the engine rpm increased from 5700 to 5925 rpm.
I needed to turn the mixture knob slightly richer with the blower running to get max. power.
Also note that the tube feeding the intake had to make a 180 deg. bend just before the throttle body.

The leaf blower used in this test was the smallest Echo makes.  Their web site lists approximately 15 blowers and the largest is a 63.3 cc 2 stroke as follows:

My thought is that several blowers are available that probably would provide the needed blower capacity. 
I believe we need a system that is adaptable to using Tracy'c RD-1 drive.  I also believe it is not likely a centrifugal blower can be placed between the engine and gear box because the spacing between the gear box plate and the engine is about 2.5 inches and the ring gear is approximately in the middle of the space.  If someone is interested in adding a direct drive blower why not attach it to the rear of the engine with the centrifugal fan attached to the crankshaft pulley?   The fans from the big blowers  may have enough capacity to work at our crankshaft speeds.  If this could be made to work it would fit the majority of the rotary installations and be an inexpensive way to add More Power Scotty.

PS I have all the power I need with my DIE intake - if someone can find a way to build it that may solve most of the power needs.

Dennis Haverlah

Bill Bradburry wrote: