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X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from access.aic-fl.com ([207.30.253.2] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2177440 for flyrotary@lancaironline.net; Sat, 14 Jul 2007 12:39:12 -0400 Received-SPF: softfail receiver=logan.com; client-ip=207.30.253.2; envelope-from=unicorn@gdsys.net Received: from acerfcafbfa90d (50.aic-fl.com [207.30.255.50]) by access.aic-fl.com (Rockliffe SMTPRA 4.5.6) with SMTP id for ; Sat, 14 Jul 2007 11:34:58 -0500 Message-ID: <002801c7c63d$a90f37c0$32ff1ecf@acerfcafbfa90d> From: "Richard Sohn" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Single Rotor Run Date: Sat, 14 Jul 2007 12:36:56 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0025_01C7C613.AA0EBF80" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0025_01C7C613.AA0EBF80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message ----- Original Message -----=20 From: Russell Duffy=20 To: Rotary motors in aircraft=20 Sent: Friday, July 13, 2007 8:59 PM Subject: [FlyRotary] Re: Single Rotor Run What torque pulses? Today was the first run with the complete engine = in flight configuration, meaning engine - psru - prop. No vibration out = of the ordinary. It, off curse, is shaking at 1300 RPM idle, just as my = Soob does. Once it goes over 1700 running like an electric motor, = almost. =20 Sounds great Richard. What prop are you running? =20 A couple thoughts come to mind about why you might not have the same = torque reversal problems I have. One is the damper in the Hirth gear = box. It might just be that it's exactly right for the job. =20 The other possibility I've mentioned before is that maybe you're = benefiting from one of the PP shortcomings. As I understand it, PP = engines tend to have less power down really low in RPM's. Perhaps this = lack of torque is what's keeping you from having the torque reversal = problems. I don't see a down side to this, and it would be THE reason = to go with PP for me (if indeed it has anything to do with it). =20 Cheers, Rusty I am using a 75" three blade Powerfin set at the tip to 13deg. =20 The key to eliminate the influence of the power pulses is to have all = natural frequencies in the power train well below the rpm operated. This = meaning high rotational inertia and soft couplers.=20 We can't do much about the inertia except bigger flywheel, and that = would be weight. So we can only Play with the coupler. Early on, I = determined that the coupler used on the two rotor is way too stiff for = single rotor. Even with the softest rubber, you can not get the freedom = needed for low enough natural freuency and sufficient damping factor. = The only way to achieve that is with a much smaller radius for the = location of the coupling elements. I don't know what your coupler looks like, but I would suspect that it = is very close to what is used on the two rotors. If every thing else fails, the Hirth comes with the option for a = clutch. And the price is right. Richard ------=_NextPart_000_0025_01C7C613.AA0EBF80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message

----- Original Message -----
From:=20 Russell=20 Duffy
To: Rotary motors in = aircraft

Sent: Friday, July 13, 2007 = 8:59 PM

Subject: [FlyRotary] Re: Single = Rotor=20 Run

What torque pulses? Today was = the first run=20 with the complete engine in flight configuration, meaning engine - = psru -=20 prop. No vibration out of the ordinary. It, off curse, is shaking at = 1300 RPM=20 idle, just as my Soob does. Once it goes over 1700 running like an = electric=20 motor, almost.

Sounds great Richard. What prop = are you=20 running?

A couple thoughts come to mind about why you = might not=20 have the same torque reversal problems I have. One is the damper = in the=20 Hirth gear box. It might just be that it's exactly right for the = job.

The other possibility I've mentioned before = is that maybe=20 you're benefiting from one of the PP shortcomings. As I = understand it,=20 PP engines tend to have less power down really low=20 in RPM's. Perhaps this lack of torque is what's keeping you = from=20 having the torque reversal problems. I don't see a down side to = this,=20 and it would be THE reason to go with PP for me (if = indeed it has=20 anything to do with = it).

Cheers,

Rusty

I am using a=20 75" three blade Powerfin set at the tip to 13deg. =20

The key to=20 eliminate the influence of the power pulses is to have all natural = frequencies=20 in the power train well below the rpm operated. This meaning high = rotational=20 inertia and soft couplers.

We can't do=20 much about the inertia except bigger flywheel, and that would be = weight. So we=20 can only Play with the coupler. Early on, I determined that the = coupler used=20 on the two rotor is way too stiff for single rotor. Even with = the =20 softest rubber, you can not get the freedom needed for low enough = natural=20 freuency and sufficient damping factor. The only way to achieve that = is with a=20 much smaller radius for the location of the coupling=20 elements.

I don't know=20 what your coupler looks like, but I would suspect that it is very = close to=20 what is used on the two rotors.

If every=20 thing else fails, the Hirth comes with the option for a clutch. And = the price=20 is right.

Richard

= ------=_NextPart_000_0025_01C7C613.AA0EBF80--