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[172.14.16.72] by web161204.mail.bf1.yahoo.com via HTTP; Wed, 23 Apr 2014 09:49:19 PDT X-Rocket-MIMEInfo: 002.001,CgrCoApUaGFua3MgQ2hyaXMuwqAgCsKgCkF0IGx1bmNoIEkgbG9va2VkIG92ZXIgeW91ciBleGNlbGxlbnQgcmVwb3J0IG9uIHRoZSAzMjAvMzYwIGFuZCBMZWdhY3kgaHlkcmF1bGljIHN5c3RlbXMuwqAgV2UgaGF2ZSB0aGUgcHJlLTIwMDUgTGVnYWN5IGh5ZHJhdWxpYyBwdW1wIHdl4oCZZCBtb2RpZmllZCBmb3IgMjggVkRDIGFuZCBjaGFuZ2VkIHRvIHRoZSBoaWdoIGNhcGFjaXR5IHB1bXAuwqAgSeKAmWQgbmV2ZXIgaGVhcmQgYW55dGhpbmcgZnJvbSBMYW5jYWlyIGFib3V0IGEgY2hhbmdlIGluIHRoZSABMAEBAQE- X-Mailer: YahooMailWebService/0.8.185.657 X-Original-Message-ID: <1398271759.8065.YahooMailNeo@web161204.mail.bf1.yahoo.com> X-Original-Date: Wed, 23 Apr 2014 09:49:19 -0700 (PDT) From: Chris Zavatson Reply-To: Chris Zavatson Subject: Gear Down...INOP X-Original-To: LML posts , "Thorn Valin B. \(JSC-VA411\)" MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="1173436188-555757058-1398271759=:8065" --1173436188-555757058-1398271759=:8065 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable =0A=0A=C2=A0=0AThanks Chris.=C2=A0 =0A=C2=A0=0AAt lunch I looked over your = excellent report on the 320/360 and Legacy hydraulic systems.=C2=A0 We have= the pre-2005 Legacy hydraulic pump we=E2=80=99d modified for 28 VDC and ch= anged to the high capacity pump.=C2=A0 I=E2=80=99d never heard anything fro= m Lancair about a change in the internals as you described it =E2=80=93 sym= metric spool, spool centering springs, 150 psi backpressure circuit removed= , etc.=0A=C2=A0=0AOf course we have the three way dump valve to handle the = hydraulic cylinder rod retraction/extension on dump valve activation.=C2=A0= But, it seems everything thing else must be 320/360 type internal on the s= pool and backpressure circuit.=C2=A0 =0A=C2=A0=0AI=E2=80=99m not sure what = changes we should make, if any, to have a system that isn=E2=80=99t prone t= o these pressure lock ups with temperature changes=E2=80=A6=C2=A0 Suggestio= ns?=C2=A0 I think William Ford=E2=80=99s Legacy kit number is close to ours= so he likely has a similar setup=E2=80=A6=0A=C2=A0=0AThanks again,=0A=C2= =A0=0AValin Thorn=0ALegacy Project=0ABoulder, Colorado=0A=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=0AValin,=0AMy involvement with the Legacy pumps started when t= hey began showing up in 320/360s.=C2=A0 Lancair wanted to only carry one co= nfiguration for both planes.=C2=A0 This is when I learned of the return spr= ings having been added to the Legacy pump.=C2=A0 Apparently no one really t= hought through what would happen during thermal cycling.=C2=A0 Personnel tu= rn-over at both Parker and Lancair left everyone scratching their heads as = to why this change was made.=C2=A0 All agreed it had the potential for lock= up.=C2=A0 They was little motivation, however,=C2=A0to do anything about i= t.=C2=A0=C2=A0The Legacy had a 'get out of jail free' card with=C2=A0the th= ree way dump valve .=C2=A0 The 320/360 was a little more problematic.=C2=A0= The most I could get from Lancair was an offer to include a note with each= 320/360 shipment stating something to the effect "this pump may lock up yo= ur hydraulic system on a warm day".=C2=A0 =0AWhile Parker was still in the = aviation business, they were supplying parts free of charge to revert Legac= y pumps back to the original 320/360 configuration while retaining the high= er volume gear pump.=0AThe Legacy fleet unfortunately has a mixture of pump= variants.=C2=A0 Early unit were likely 320/360 pumps.=C2=A0 Then came the = higher volume gear pump and a symmetric spool.=C2=A0 After that, the return= springs (which also removed the return line back pressure spring).=C2=A0 I= f an early model=C2=A0pump ever went into Parker for servicing, the interna= l configuration may have been 'upgraded'.=C2=A0=C2=A0=0AIn my opinion, the = best configuration for the Legacy is: =0A=0A1.=C2=A0 high volume gear pump = - larger fluid volume in the system.=0A2. symmetric spool - system has cyli= nders in both extension and retraction orientation=0A3. no spool return spr= ings - they add no benefit, only lock up potential=0A4. add/retain the 150p= si back pressure circuit in the reservoir return line - belt and suspenders= to ensure the spool cannot get stuck at a travel endpoint.=C2=A0 Note that= the return line from the dump valve (third line in the center) bypasses th= e 150 psi circuit.=C2=A0 Only fluid coming from within the pump is subject = to the 150 psi back pressure.=C2=A0=0A=0AThe Legacy may also benefit from a= higher low side pressure setting, especially for those with older, low vol= ume gear pumps.=C2=A0=C2=A0The higher volume gear pump may be able to outru= n the pressure surge that is generated at the initiation of gear extension.= =C2=A0=C2=A0This is where pressure gauges are useful.=C2=A0=C2=A0You'll see= =C2=A0the pressure spike on the low side upon selecting gear down.=C2=A0 If= the spike hits the low side pressure setting the pump will shut=C2=A0down.= =C2=A0 800 psi works well for the 320/360.=C2=A0 The higher=C2=A0volume gea= r pump lowers the risk, but I can't put a number to it without some data.= =C2=A0 =0Ahope that helps,=0A=0AChris Zavatson=0AN91CZ=0A360std=0Awww.N91CZ= .net=0A --1173436188-555757058-1398271759=:8065 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable

 
Thanks Chris. 
=  
At lunch I looked ov= er your excellent report on the 320/360 and Legacy hydraulic systems. = We have the pre-2005 Legacy hydraulic pump we=E2=80=99d modified for 28 VD= C and changed to the high capacity pump.  I=E2=80=99d never heard anyt= hing from Lancair about a change in the internals as you described it =E2= =80=93 symmetric spool, spool centering springs, 150 psi backpressure circu= it removed, etc.
 
Of course we have the three way= dump valve to handle the hydraulic cylinder rod retraction/extension on du= mp valve activation.  But, it seems everything thing else must be 320/360 type internal on the s= pool and backpressure circuit. 
 
I=E2=80=99= m not sure what changes we should make, if any, to have a system that isn= =E2=80=99t prone to these pressure lock ups with temperature changes=E2=80= =A6  Suggestions?  I think William Ford=E2=80=99s Legacy kit numb= er is close to ours so he likely has a similar setup=E2=80=A6=
 
Thanks again,
=  
Valin Thorn
Legacy Project
Boulder, Colorado
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Valin,
My= involvement with the Legacy pumps started when they began showing u= p in 320/360s.  Lancair wanted to only carry one configuration for bot= h planes.  This is when I learned of the return springs having been ad= ded to the Legacy pump.  Apparently no one really thought through what= would happen during thermal cycling.  Personnel turn-over at both Par= ker and Lancair left everyone scratching their heads as to why this change = was made.  All agreed it had the potential for lock up.  They was= little motivation, however, to do anything about it.  The L= egacy had a 'get out of jail free' card with the three way dump valve = .  The 320/360 was a little more problematic.  The most I could g= et from Lancair was an offer to include a note with each 320/360 shipment s= tating something to the effect "this pump may lock up your hydraulic system on a warm day". 
While Parker was still in the avia= tion business, they were supplying parts free of charge to revert Legacy pu= mps back to the original 320/360 configuration while retaining the higher v= olume gear pump.
The Legacy fleet unfortunately has a mixture of = pump variants.  Early unit were likely 320/360 pumps.  Then came = the higher volume gear pump and a symmetric spool.  After that, the re= turn springs (which also removed the return line back pressure spring).&nbs= p; If an early model pump ever went into Parker for servicing, the int= ernal configuration may have been 'upgraded'.  
In my o= pinion, the best configuration for the Legacy is:

1.  high volume gear pump - larger fluid volume in the system.<= div>2. symmetric spool - system has cylinders in both extension and retract= ion orientation
3. no spool return springs - they add no benefit, only lock up potential
4. add/retain the 150psi back pr= essure circuit in the reservoir return line - belt and suspenders to ensure= the spool cannot get stuck at a travel endpoint.  Note that the retur= n line from the dump valve (third line in the center) bypasses the 150 psi = circuit.  Only fluid coming from within the pump is subject to the 150= psi back pressure. 

The Legacy may also bene= fit from a higher low side pressure setting, especially for those with olde= r, low volume gear pumps.  The higher volume gear pump may be abl= e to outrun the pressure surge that is generated at the initiation of gear = extension.  This is where pressure gauges are useful.  = You'll see the pressure spike on the low side upon selecting gear down= .  If the spike hits the low side pressure setting the pump will shut&= nbsp;down.  800 psi works well for the 320/360.  The higher volume gear pump lowers the risk, but I can't put a number to = it without some data. 
hope that helps,

Chris Zavatson
N91CZ
360std
www.N91CZ.n= et
--1173436188-555757058-1398271759=:8065--