X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [201.225.225.169] (HELO cwpanama.net) by logan.com (CommuniGate Pro SMTP 5.0.6) with ESMTP id 935170 for flyrotary@lancaironline.net; Fri, 20 Jan 2006 22:36:23 -0500 Received-SPF: none receiver=logan.com; client-ip=201.225.225.169; envelope-from=rijakits@cwpanama.net Received: from [201.224.93.110] (HELO usuarioq3efog0) by frontend3.cwpanama.net (CommuniGate Pro SMTP 4.2.10) with SMTP id 56687261 for flyrotary@lancaironline.net; Fri, 20 Jan 2006 22:38:43 -0500 Message-ID: <021b01c61e3b$ba573920$6e5de0c9@usuarioq3efog0> From: "rijakits" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: flywheel weight? Date: Fri, 20 Jan 2006 22:35:29 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0217_01C61E11.D1302AF0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 This is a multi-part message in MIME format. ------=_NextPart_000_0217_01C61E11.D1302AF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit MessageRusty, at this stage I would try the following (all of it VWAG, as I have no experience with Rotaries WSE, but a little with track&balance): a. Cheapest way is good: Mount a chunk of whatever to go hopelesly beyond needed mass. (I don't know what is cheapest in your corner - a chunk of steel turned on a lathe, e.g. This way you can have it turned down bit by bit to find the "critical mass") b. Take off the prop, mount the mass to the PSRU. c1. If idle-problems/vibrations/shake&rattle&hum (PVSRH) continue - remove PSRU and mount directly to the engine. d1. Confirm no problems with mass and engine alone - remember, 2 rotors is NOT the same as 1 rotor and some flywheel mass, distances are different, so different resonances can happen. IF I remember right from Engineering school: The faster you spin an assembly the smoother it gets, no matter what the imbalance is - at some point it goes to zero, depending on rpm/imbalance/inertia/mass - the problem is to get the rpm past the resonance-rpms (you seem to see that at various rpm settings on your 1-rotor) Just like your car wheels - generally they would show imbalance worst around 70 - 100 km/h. Get past that speed and everything smoothes out! Better solution: Get your wheels balanced - I guess that's what we want here too: Smooth&low idle, no shakes all through the rpm-band. e1. Get the PSRU back on and start reducing the mass - if PVSRH gets worse, you have a problem with the dampers. c2. If there is no PVSRH, start to cut down mass little by little to see if PVSRH starts at some point. d2. Once the weight is down to Prop/Hub/etc. weight and no PVSRH is there, you have some resonance/vibration induced by the prop/hub. d3. If PVSRH is worse at some place before Prop/Hub/etc. weight is reached, you have an idea how much weight you need to add at the present prop/hub combo. And you know you have resonance problem with the PSRU, be it dampers or gear masses, etc. f. Whenever you take off the mass for modification: Unplug that ACES to re-charge it!! :) You always want to see the spectrum and the IPS/clock readings!! :) Rusty (resistance is futile) "I told you so" Rusty (trying hopelessly to resist) " What'd I say!!" "If I'm smart, I'll just pull the prop, so the engine runs well, and I'll run it every now and then when I go to the airport. That will keep it healthy, and let me work on the RV-8 instead." Ahh, forget that!! You couldn't sleep at night!! Just find the fastest way to get the mass on and off - this way you always do something on the Rotary, while doing your RV/Lyc (Uagh!) thing. However you could have the mass machined with a couple of threads, so you can change weights fast!! You have an electronic scale with your ACES, do you? Thomas Jakits (finished 120 messages backlog of 3 days and putting the "scientist" back into Rusty - at least trying!!) ----- Original Message ----- From: Russell Duffy To: Rotary motors in aircraft Sent: Friday, January 20, 2006 4:41 PM Subject: [FlyRotary] Re: flywheel weight? 10lbs. That is about the weight of a rotor. But you'll be spinning it 3 times as fast, so it'll have 8 times the momentum (momentum is velocity squared, right?). The object is to keep the shaft from speeding up and slowing down, and I think increasing the momentum 8 times would accomplish that well. Hi Ernest, All WAG's appreciated. I'm not sure the biggest problem is the missing mass of the 2nd rotor, but rather the missing firing pulse. If we were to continue your momentum thought though, the flywheel advantage would be even greater than you suggested. Remember that the center of the rotor mass is traveling in a much smaller radius circle than the mass of the flywheel ring that I proposed. Heck, maybe that 1.5 lbs of weight that I had before would have made up for the missing rotor :-) other ideas: Have the disc water/laser cut. And you don't need 4130, so have the cutter use whatever steel they have on hand. Have a brake shop turn the disc and balance it, or you might just be able to get a brake rotor that would bolt right into place with little or no modification. The heavy duty Matco rotors I just bought seem to be around those dimensions if memory serves. Interesting thoughts. I'm still leaning toward trying to install 4 separate weights, which makes it possible to do this without pulling the drive off. It also makes balancing a simple matter of precisely weighing the added weights. I can buy 1/2" steel discs in various diameters from McMaster Carr, so I would just have to drill a hole in the middle, and bolt them on. I wonder what the limit of a 7/16" bolt is for holding a couple pound weight spinning at 8000 rpm. Probably don't want to have anything in the arc of the flex plate the first time it was run up :-0 Dale, I thought about flywheels, but aren't they always manual trans flywheels, made to install on the shaft itself? I need something that coexists with the current auto balance weight, flex plate, and Tracy's dampener plate. Thanks, Rusty (trying hopelessly to resist) PS- Congrats to Joe! If this keeps up, people are going to think that rotaries can only fly backwards :-) ------=_NextPart_000_0217_01C61E11.D1302AF0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Rusty,
 
at this stage I would try the following (all of = it VWAG,=20 as I have no experience with Rotaries WSE, but a little with=20 track&balance):
 
a. Cheapest way is good: Mount a chunk of = whatever to=20 go hopelesly beyond needed mass.
(I don't know what is cheapest in your corner - = a chunk of=20 steel turned on a lathe, e.g. This way you can have it turned down bit = by bit to=20 find the "critical mass")
b. Take off the prop, mount the mass to the=20 PSRU.
 
c1. If = idle-problems/vibrations/shake&rattle&hum=20 (PVSRH) continue - remove PSRU and mount directly to the=20 engine.
d1. Confirm no problems with mass and engine = alone -=20 remember, 2 rotors is NOT the same as 1 rotor and some flywheel mass, = distances=20 are different, so different resonances can happen.
IF I remember right from Engineering school: =
The faster you spin an assembly the smoother it = gets, no=20 matter what the imbalance is - at some point it goes to zero, depending = on=20 rpm/imbalance/inertia/mass - the problem is to get the rpm past the=20 resonance-rpms (you seem to see that at various rpm settings on your=20 1-rotor)
Just like your car wheels - generally they would = show=20 imbalance worst around 70 - 100 km/h. Get past that speed and = everything=20 smoothes out! Better solution: Get your wheels balanced
- I guess that's what we want here too: = Smooth&low=20 idle, no shakes all through the rpm-band.
 
e1. Get the PSRU back on and start reducing the = mass - if=20 PVSRH gets worse, you have a problem with the dampers.
 
c2. If there is no PVSRH, start to cut down mass = little by=20 little to see if PVSRH starts at some=20 point.
d2. Once the weight is down to Prop/Hub/etc. = weight and no=20 PVSRH is there, you have some resonance/vibration induced by the=20 prop/hub.
d3. If PVSRH is worse at some place before = Prop/Hub/etc.=20 weight is reached, you have an idea how much weight you need to add at = the=20 present prop/hub combo.
And you know you have resonance problem with the = PSRU, be=20 it dampers or gear masses, etc.
 
f. Whenever you take off the mass for = modification: Unplug=20 that ACES to re-charge it!! :)
 You always want to see the spectrum and = the=20 IPS/clock readings!! :)
 
 
 
Rusty = (resistance is=20 futile)  "I told you=20 so"
Rusty (trying hopelessly to = resist) " What'd I say!!"
 
"If I'm smart, I'll just pull = the prop, so=20 the engine runs well, and I'll run it every now and then when I go to = the=20 airport.  That will keep it healthy, and let me work on the RV-8 = instead."=20
Ahh, = forget that!!=20
You = couldn't sleep at=20 night!!
Just find = the fastest=20 way to get the mass on and off - this way you always do something on the = Rotary,=20 while doing your RV/Lyc (Uagh!) thing.
However you could have the mass = machined=20 with a couple of threads, so you can change weights fast!! You have an=20 electronic scale with your ACES, do you?
 
Thomas Jakits (finished 120 messages = backlog of 3=20 days and putting the "scientist" back into Rusty - at least=20 trying!!)
 
 
 
----- Original Message -----
From:=20 Russell=20 Duffy
Sent: Friday, January 20, 2006 = 4:41=20 PM
Subject: [FlyRotary] Re: = flywheel=20 weight?

10lbs.  That is about the weight of a = rotor.  But=20 you'll be spinning it
3 times as fast, so it'll have 8 times the = momentum=20 (momentum is
velocity squared, right?).  The object is to keep = the=20 shaft from
speeding up and slowing down, and I think increasing the = momentum 8
times would accomplish that well.

Hi=20 Ernest,
 
All = WAG's=20 appreciated.  I'm not sure the biggest problem is the missing = mass of the=20 2nd rotor, but rather the missing firing pulse.  If we were to = continue=20 your momentum thought though, the flywheel advantage would be = even=20 greater than you suggested.  Remember that the center of the=20 rotor mass is traveling in a much smaller radius circle than = the=20 mass of the flywheel ring that I proposed.  Heck, maybe that 1.5 = lbs of=20 weight that I had before would have made up for the missing = rotor=20 :-)
 
other ideas:  Have the disc water/laser = cut.  And=20 you don't need 4130,
so have the cutter use whatever steel they = have on=20 hand.  Have a brake
shop turn the disc and balance it, or you = might=20 just be able to get a
brake rotor that would bolt right into place = with=20 little or no
modification.  The heavy duty Matco rotors I just = bought=20 seem to be
around those dimensions if memory serves.
 
Interesting=20 thoughts.  I'm still leaning toward trying to install 4 separate = weights,=20 which makes it possible to do this without pulling the drive = off.  It=20 also makes balancing a simple matter of precisely weighing the added=20 weights.  I can buy 1/2" steel discs in various diameters from = McMaster=20 Carr, so I would just have to drill a hole in the middle, and bolt = them=20 on.  I wonder what the limit of a 7/16" bolt is for holding a=20 couple pound weight spinning at 8000 rpm.  Probably = don't want=20 to have anything in the arc of the flex plate the first = time it was=20 run up :-0
 
Dale,
 
I = thought about=20 flywheels, but aren't they always manual trans flywheels, made to = install on=20 the shaft itself?  I need something that coexists with the=20 current auto balance weight, flex plate, and Tracy's dampener=20 plate.  
 
Thanks,
Rusty (trying hopelessly to=20 resist)
 
PS- Congrats to Joe!  If = this keeps=20 up, people are going to think that rotaries can only fly backwards=20 :-)
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