X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 13 Nov 2013 13:29:21 -0500 Message-ID: X-Original-Return-Path: Received: from mail-ve0-f172.google.com ([209.85.128.172] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6588198 for lml@lancaironline.net; Wed, 13 Nov 2013 12:31:43 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.128.172; envelope-from=pjdmiller@gmail.com Received: by mail-ve0-f172.google.com with SMTP id oz11so558509veb.3 for ; Wed, 13 Nov 2013 09:31:09 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.52.230.35 with SMTP id sv3mr11665786vdc.27.1384363869778; Wed, 13 Nov 2013 09:31:09 -0800 (PST) Received: by 10.220.98.71 with HTTP; Wed, 13 Nov 2013 09:31:09 -0800 (PST) In-Reply-To: References: X-Original-Date: Wed, 13 Nov 2013 12:31:09 -0500 X-Original-Message-ID: Subject: Re: [LML] Re: N181AM nose gear collapse From: Paul Miller X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=089e0102fe6eb2bb2704eb1254a4 --089e0102fe6eb2bb2704eb1254a4 Content-Type: text/plain; charset=ISO-8859-1 Colyn and others: why aren't we using a simple off-the-shelf motor controllers like those used in power chairs, golf carts, forklifts and other safety-minded devices? They handle hundreds of amps, reversible, employ logic to prevent accidental reversal, work with voltages 12-48, programmable, log diagnostics and come already packaged in a heatsink and there are no contactors to worry about. I see them selling for a few hundred dollars. What bugs me about Adam's incident is that he had a switch in the down position and the pump ran in the UP direction. We certainly have cheap access to the technology to prevent that from happening to someone else. The scooter and forklift people can't afford to have someone go backwards when they press forward on the lever and this appears to be a mature area of motor control these days but we don't employ it. Such a device would dump all the relays as I understand it. On the Curtis models I reviewed, external contactors like the one that failed on Adam's plane are still optional but the controller current is reduced to Zero before the Contactor engages or disengages. I'm not seeing any downside and since the Oildyne pump is not a high amperage device (compared to a forklift) I believe a solid state controller can be directly connected to the Parker pump without the relays (solenoids). What am I missing? Paul Legacy On 13 November 2013 09:43, Colyn Case wrote: > A lot of contactors are not really up to it. Some things to look at in > the specs: > - for Adam's application, life expectancy vs. break current. See > "resistive load performance" on the attached ev100 data-sheet or "estimated > make/break power switching ratings" on the attached ev200 data-sheet. > - max break current. If you have a short somewhere you will have large > current. Odyssey batteries can develop over 1000 amps for example. You > would like to be able to interrupt that current by de-energizing the > contactor (e.g. turning off a master switch or pump switch) Max break > would be about the current associated with 5 cycles in the above charts. > You may have anl's everywhere designed to handle a dead short from anything > to anything within one bus. However, there's no anl appropriate for a > starter so you are really counting on the contactor to open that circuit if > you need to. Same issue with Adam trying to get his pump to stop. > > Other things that might be of interest: > - hold current. how much it takes to keep the contacts closed once they > are closed. Nice if this is low if you have an alternator failure and are > trying to stretch battery life. > - physical integrity. I think standard issue contactors are made from low > grade plastic and stamped sheet metal. It was when mine fell apart > because of abuse during installation that I got interested in higher > quality parts. > - I think there is a discussion on the archive about use of transorb's to > minimize damage of the controlling switches due to field collapse in the > contactor coil. > > I think if you can even find the related specs on standard issue > contactors, you'll find them less than satisfying. (Marv - below > attachments should be ~500KB together) > > > > On Nov 13, 2013, at 9:04 AM, Adam Molny wrote: > > Paul - > The gear relays are activated by applying a small current to the relay coil > terminals. That pulls the main contacts closed against a strong spring. > When > you remove power the spring pulls the main contacts apart. There is a known > failure mode where the main contacts weld themselves together. When that > happens the relay will remain in the "on" state regardless of what the > pressure switches are doing. > > -Adam > -----Original Message----- > From: Paul Miller [mailto:pjdmiller@gmail.com] > > Adam, I don't understand how this happens unless the pressure switches on > the pump aren't shutting down. > > Paul > > > -- > For archives and unsub > http://mail.lancaironline.net:81/lists/lml/List.html > > > -- > For archives and unsub > http://mail.lancaironline.net:81/lists/lml/List.html > > --089e0102fe6eb2bb2704eb1254a4 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Colyn and others: why aren't we using a simple off-the= -shelf motor controllers like those used in power chairs, golf carts, forkl= ifts and other safety-minded devices? =A0 They handle hundreds of amps, rev= ersible, employ logic to prevent accidental reversal, work with voltages 12= -48, programmable, log diagnostics and come already packaged in a heatsink = and there are no contactors to worry about. =A0I see them selling for a few= hundred dollars. =A0 What bugs me about Adam's incident is that he had= a switch in the down position and the pump ran in the UP direction. =A0 We= certainly have cheap access to the technology to prevent that from happeni= ng to someone else. =A0 The scooter and forklift people can't afford to= have someone go backwards when they press forward on the lever and this ap= pears to be a mature area of motor control these days but we don't empl= oy it. =A0Such a device would dump all the relays as I understand it. =A0On= the Curtis models I reviewed, =A0external contactors like the one that fai= led on Adam's plane are still optional but the controller current is re= duced to Zero before the Contactor engages or disengages. =A0 I'm not s= eeing any downside and since the Oildyne pump is not a high amperage device= (compared to a forklift) I believe a solid state controller can be directl= y connected to the Parker pump without the relays (solenoids).

What am I missing?

Paul
<= div>Legacy




On 13 November 2013 09:43,= Colyn Case <colyncase@earthlink.net> wrote:
A lot of contactors are not really up to it.= =A0Some things to look at in the specs:
- for Adam's application, life expectancy vs. break current. =A0 See &q= uot;resistive load performance" on the attached ev100 data-sheet or &q= uot;estimated make/break power switching ratings" on the attached ev20= 0 data-sheet.
- max break current. =A0 If you have a short somewhere you will have large = current. =A0Odyssey batteries can develop over 1000 amps for example. =A0Yo= u would like to be able to interrupt that current by de-energizing the cont= actor (e.g. turning off a master switch or pump switch) =A0 Max break would= be about the current associated with 5 cycles in the above charts. =A0 You= may have anl's everywhere designed to handle a dead short from anythin= g to anything within one =A0bus. =A0 However, there's no anl appropriat= e for a starter so you are really counting on the contactor to open that ci= rcuit if you need to. =A0Same issue with Adam trying to get his pump to sto= p.

Other things that might be of interest:
- hold current. =A0how much it takes to keep the contacts closed once they = are closed. =A0 Nice if this is low if you have an alternator failure and a= re trying to stretch battery life.
- physical integrity. =A0I think standard issue contactors are made from lo= w grade plastic and stamped sheet metal. =A0 It was when mine fell apart be= cause of abuse during installation that I got interested in higher quality = parts.
- I think there is a discussion on the archive about use of transorb's = to minimize damage of the controlling switches due to field collapse in the= contactor coil.

I think if you can even find the related specs on standard issue contactors= , you'll find them less than satisfying. =A0(Marv - below attachments s= hould be ~500KB together)



On Nov 13, 2013, at 9:04 AM, Adam Molny wrote:

Paul -
The gear relays are activated by applying a small current to the relay coil=
terminals. That pulls the main contacts closed against a strong spring. Whe= n
you remove power the spring pulls the main contacts apart. There is a known=
failure mode where the main contacts weld themselves together. When that happens the relay will remain in the "on" state regardless of wha= t the
pressure switches are doing.

-Adam
-----Original Message-----
From: Paul Miller [mailto:pjdmiller@= gmail.com]

Adam, I don't understand how this happens unless the pressure switches = on
the pump aren't shutting down.

Paul


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