flyrotary@lancaironline.net Mailing List Archive

Excellent point Finn; the CAS shielding should definitely NOT be grounded at 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 would induce interference to the CAS signals. Jeff -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf 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 current would find alternative paths. If on of those paths were CAS wiring it would introduce a voltage drop in that wiring, just like 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 > firewall on top of the wing spar. I have #10 wires that connect from > the batery terminals to feed the power and fround buss for the fuel > puels, coils, fuel injectors, EC-2, etc. I have two 1/0 AWG cables > that also connect to the battery terminals. The positive runs back tot > he starter, and is about 6 feet long. The negative did run to one of > the tapped holes for the A/C compressor on the front engine housing. > The ground is about 4 ft long currently. I am going to remove that > cable and run the ground from the battery to one of the starter > 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 > mounting plate, and the torsion bolts through the engine, that it > wouldn't be a really good conductor, but I would apparently be > mistaken. I am not exactly clear on how it interferrs with the CAS > signal, but it does. My ground was mounted just below the CAS about 8 > inches, so perhaps that has something to do with it. It works fine > there though for several years, before I started having difficulty > 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 >> isn't conductive either, even with bare aluminum - conduction is made >> through the bolts and not the entire mating surface of the plate. The >> math checks out too. I'm still curious about their specific setups >> though; I can see how a stack of aluminum/iron/aluminum, etc with a >> layer of hylomar in between each stack might not be the best >> conductor - the sub-mount plate has to help. >> >> In my setup the battery is behind the cabin for weight and balance >> considerations. Ground is made to a steel tube frame with about 1 >> foot of #1 welding cable; Positive runs through Master relay under >> the floor to firewall with about 6 feet of same #1 welding cable, >> then another 2.5 feet to starter. The engine ground is via stainless >> braid from front iron to engine mount hardware at the >> firewall/airframe. So if the starter current path is from post to >> post on the battery, then in my case it has to be close to 16 feet! >> I've never had any starting problems, but it would be interesting to >> see if an extra ground strap from starter bracket back to the >> airframe makes the starter spin faster or engine fire sooner . will >> test that and post results. >> >> Jeff >> >> *From:* Rotary motors in aircraft >> [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 >> is a light duty one but its rating is 1.2 KW. With a typical cranking >> voltage of 10 volts, that's 120 amps. With that kind of current, the >> only logical routing of the ground cable is as directly to the load >> as possible. >> >> Do the math. At that current level, it only takes about .008 ohms to >> drop your working voltage a full 1 volt. That's 10% of your cranking >> power lost. Rotaries are especially sensitive to cranking speed >> because they lose more compression than piston engines at low speed. >> Low compression makes starting more difficult. Losses in this circuit >> must be minimized for many reasons. Also note that the ground >> connection point that many have said they are using goes very near >> the crank sensor and its wiring. This proximity makes inductive >> coupling into the CAS circuit more likely. >> >> Add all these factors up and it is not surprising that many builders >> have starting problems. >> >> Tracy >> >> On Tue, Nov 24, 2009 at 8:52 AM, Jeff Whaley <jwhaley@datacast.com >> <mailto:jwhaley@datacast.com>> wrote: >> >> I'm curious about the engine mount style you guys are using with this >> voltage drop situation. >> >> I can't imagine this problem occurring with the bed-mount/aluminum >> plate between the oil pan and engine block configuration. >> >> Surely a 3/8" or ½" plate of aluminum and 20 bolts will conduct from >> housing to housing? - unless maybe it was anodized? >> >> Jeff >> >> *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net >> <mailto:flyrotary@lancaironline.net>] *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). >> Sure gives one a good feeling after battling a problem for so long. >> BTW, I have two grounds on my engine. One is to the front cover, one >> 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 <cozy4pilot@gmail.com >> <mailto:cozy4pilot@gmail.com>> wrote: >> >> Al & Mark, >> I would say that many people may have their ground to the engine >> block. Mine has been that way since I built the plane, and worked >> 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 >> longer ground cable. Hopefully they will arrive before Thanksgiving, >> 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 >> ground. I wonder how many of us have our engine grounds tied to a >> 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 >> starting issue, but I have followed this discussion with interest >> because a couple of years ago I did a starting spark check and found >> the sparks considerably weaker than the mode 8 (or whatever) check. I >> just assumed it was due to the voltage drawdown when the starter was >> running. Now it's worth another look. >> >> I recall giving it some thought when doing the wiring (My EC/EM >> manuals apparently predated Tracy recommended wiring diagram). I >> concluded that the various things bolted to the engine, like the >> manifolds, would provide good conduction paths regardless of the >> sealing between layers - and the 20B has a couple more layers. Both >> my intake and exhaust flanges are continuous and connect all the >> layers, and there are other things making the connection to the front >> cover, so this would be less of an issue compared to an installation >> having separate flanges to each housing. >> >> Anyway, Steve; I'm glad you found the problem. And thanks; it's a >> help to the rotary community, and again proves the value of a list >> such as this. >> >> Al G >> >> >> >> -- >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub: >> 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 > -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html