X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from EXHUB003-3.exch003intermedia.net ([207.5.74.110] verified) by logan.com (CommuniGate Pro SMTP 5.3c3) with ESMTPS id 3990725 for flyrotary@lancaironline.net; Wed, 25 Nov 2009 11:01:44 -0500 Received-SPF: none receiver=logan.com; client-ip=207.5.74.110; envelope-from=jwhaley@datacast.com Received: from EXVMBX003-5.exch003intermedia.net ([207.5.74.45]) by EXHUB003-3.exch003intermedia.net ([207.5.74.110]) with mapi; Wed, 25 Nov 2009 08:01:07 -0800 From: Jeff Whaley To: Rotary motors in aircraft Date: Wed, 25 Nov 2009 08:03:25 -0800 Subject: RE: [FlyRotary] Re: No start Thread-Topic: [FlyRotary] Re: No start Thread-Index: Acpt5eWViN5PbfIYQ4OaahuVahwV/AAAQ/fw Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Excellent point Finn; the CAS shielding should definitely NOT be grounded a= t both ends! It should shield/encase the CAS wires right up to the rubber grommet at CAS= body but be grounded at EC2 case ONLY! If it was grounded at both ends any current flowing through the shield woul= d induce interference to the CAS signals. Jeff -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Finn Lassen Sent: Wednesday, November 25, 2009 10:44 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: No start Does the CAS wiring have a shield grounded at both ends? Realize that when your main ground path to the starter was bad the=20 current would find alternative paths. If on of those paths were CAS=20 wiring it would introduce a voltage drop in that wiring, just like=20 inserting the 1.5 volt battery... Finn Steve Brooks wrote: > Jeff, > In my case, which is a pusher, my aft battery sits just inside the=20 > firewall on top of the wing spar. I have #10 wires that connect from=20 > the batery terminals to feed the power and fround buss for the fuel=20 > puels, coils, fuel injectors, EC-2, etc. I have two 1/0 AWG cables=20 > that also connect to the battery terminals. The positive runs back tot=20 > he starter, and is about 6 feet long. The negative did run to one of=20 > the tapped holes for the A/C compressor on the front engine housing.=20 > The ground is about 4 ft long currently. I am going to remove that=20 > cable and run the ground from the battery to one of the starter=20 > mounting bolts, which will also make it about 6 ft long. > > I also find it hard to believe that given all of the bolts in the=20 > mounting plate, and the torsion bolts through the engine, that it=20 > wouldn't be a really good conductor, but I would apparently be=20 > mistaken. I am not exactly clear on how it interferrs with the CAS=20 > signal, but it does. My ground was mounted just below the CAS about 8=20 > inches, so perhaps that has something to do with it. It works fine=20 > there though for several years, before I started having difficulty=20 > starting the engine. > > > Regards, > Steve Brooks > Cozy MKIV > Turbo rotary > > Jeff Whaley wrote: >> >> Good point on the anodizing Tracy; also a .005" layer of silicone=20 >> isn't conductive either, even with bare aluminum - conduction is made=20 >> through the bolts and not the entire mating surface of the plate. The=20 >> math checks out too. I'm still curious about their specific setups=20 >> though; I can see how a stack of aluminum/iron/aluminum, etc with a=20 >> layer of hylomar in between each stack might not be the best=20 >> conductor - the sub-mount plate has to help. >> >> In my setup the battery is behind the cabin for weight and balance=20 >> considerations. Ground is made to a steel tube frame with about 1=20 >> foot of #1 welding cable; Positive runs through Master relay under=20 >> the floor to firewall with about 6 feet of same #1 welding cable,=20 >> then another 2.5 feet to starter. The engine ground is via stainless=20 >> braid from front iron to engine mount hardware at the=20 >> firewall/airframe. So if the starter current path is from post to=20 >> post on the battery, then in my case it has to be close to 16 feet!=20 >> I've never had any starting problems, but it would be interesting to=20 >> see if an extra ground strap from starter bracket back to the=20 >> airframe makes the starter spin faster or engine fire sooner . will=20 >> test that and post results. >> >> Jeff >> >> *From:* Rotary motors in aircraft=20 >> [mailto:flyrotary@lancaironline.net] *On Behalf Of *Tracy Crook >> *Sent:* Tuesday, November 24, 2009 9:43 AM >> *To:* Rotary motors in aircraft >> *Subject:* [FlyRotary] Re: No start >> >> I doubt anodizing is a factor. Keep in mind that the starter we use=20 >> is a light duty one but its rating is 1.2 KW. With a typical cranking=20 >> voltage of 10 volts, that's 120 amps. With that kind of current, the=20 >> only logical routing of the ground cable is as directly to the load=20 >> as possible. >> >> Do the math. At that current level, it only takes about .008 ohms to=20 >> drop your working voltage a full 1 volt. That's 10% of your cranking=20 >> power lost. Rotaries are especially sensitive to cranking speed=20 >> because they lose more compression than piston engines at low speed.=20 >> Low compression makes starting more difficult. Losses in this circuit=20 >> must be minimized for many reasons. Also note that the ground=20 >> connection point that many have said they are using goes very near=20 >> the crank sensor and its wiring. This proximity makes inductive=20 >> coupling into the CAS circuit more likely. >> >> Add all these factors up and it is not surprising that many builders=20 >> have starting problems. >> >> Tracy >> >> On Tue, Nov 24, 2009 at 8:52 AM, Jeff Whaley > > wrote: >> >> I'm curious about the engine mount style you guys are using with this=20 >> voltage drop situation. >> >> I can't imagine this problem occurring with the bed-mount/aluminum=20 >> plate between the oil pan and engine block configuration. >> >> Surely a 3/8" or =BD" plate of aluminum and 20 bolts will conduct from=20 >> housing to housing? - unless maybe it was anodized? >> >> Jeff >> >> *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net=20 >> ] *On Behalf Of *Mark Steitle >> *Sent:* Monday, November 23, 2009 4:41 PM >> *To:* Rotary motors in aircraft >> *Subject:* [FlyRotary] Re: No start >> >> Steve, >> >> Glad you got things figured out (we were running out of suggestions).=20 >> Sure gives one a good feeling after battling a problem for so long.=20 >> BTW, I have two grounds on my engine. One is to the front cover, one=20 >> to the front side housing. I'll check into moving one up to the starter. >> >> Mark >> >> On Mon, Nov 23, 2009 at 3:33 PM, Steve Brooks > > wrote: >> >> Al & Mark, >> I would say that many people may have their ground to the engine=20 >> block. Mine has been that way since I built the plane, and worked=20 >> fine for three or four years before I started having an issue. >> >> I had to order a couple of new crimp connectors, so that I can make a=20 >> longer ground cable. Hopefully they will arrive before Thanksgiving,=20 >> so that I can get it all hooked up over the long weekend. >> >> Steve Brooks >> >> >> Al Gietzen wrote: >> >> >> Steve, >> >> I read your other post on what you discovered regarding your bad=20 >> ground. I wonder how many of us have our engine grounds tied to a=20 >> bolt near the front cover or end housing? (Mine does...) >> >> Mark S. >> >> Mine does as well - bolts to the front cover. I have never had a=20 >> starting issue, but I have followed this discussion with interest=20 >> because a couple of years ago I did a starting spark check and found=20 >> the sparks considerably weaker than the mode 8 (or whatever) check. I=20 >> just assumed it was due to the voltage drawdown when the starter was=20 >> running. Now it's worth another look. >> >> I recall giving it some thought when doing the wiring (My EC/EM=20 >> manuals apparently predated Tracy recommended wiring diagram). I=20 >> concluded that the various things bolted to the engine, like the=20 >> manifolds, would provide good conduction paths regardless of the=20 >> sealing between layers - and the 20B has a couple more layers. Both=20 >> my intake and exhaust flanges are continuous and connect all the=20 >> layers, and there are other things making the connection to the front=20 >> cover, so this would be less of an issue compared to an installation=20 >> having separate flanges to each housing. >> >> Anyway, Steve; I'm glad you found the problem. And thanks; it's a=20 >> help to the rotary community, and again proves the value of a list=20 >> such as this. >> >> Al G >> >> >> >> --=20 >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub:=20 >> http://mail.lancaironline.net:81/lists/flyrotary/List.html >> > > > --=20 > Homepage: http://www.flyrotary.com/ > Archive and UnSub: =20 > http://mail.lancaironline.net:81/lists/flyrotary/List.html > -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.= html