airhound Posted August 30, 2012 Report Share Posted August 30, 2012 Doug, think about a special wire that has a known resistance per inch or foot. This wire gets wrapped around a non-conductive center support. For each wrap the resistance goes up a known amount. Only one end of this wire is connected to a ground source. The wire from the instrument is connected to a pointer that moves up and down the wraps of wire. For each wrap that it moves away from the ground connection the resistance increases and the input voltage drops. The instrument actually measures voltage and displays it in what ever unit you want displayed. For oil pressure the instrument is supplied 12 volts. It then sends the 12 volts to the sending unit. As the oil pressure increases the pointer moves on the wire increasing the resistance. The resitance causes the voltage to drop. The instument measures the voltage drop and displays the increase in pressure on the instrument. Yes I understand better what sender is sending and why.....again many thanks for your time and effort to explain the science to me. Link to comment Share on other sites More sharing options...
airhound Posted August 30, 2012 Report Share Posted August 30, 2012 Vibration kills them because of the mechanism inside. The oil and fuel pressure senders are the same design internally. The pointer that you see in the picks moves along the horizontal rail and copper wire. This pointer is spring mounted and moves from pressure coming in. Because of this design with the pointer just hanging out there and the very small movement it takes to make a pressure change reading in the cockpit is is highly susceptible to vibration over time. Thanks Roger, Jim and Tom.......yup the picture along with the professional explanations have me in a better place with understanding what the parts surrounding me are doing and how...dj Link to comment Share on other sites More sharing options...
Runtoeat Posted August 30, 2012 Report Share Posted August 30, 2012 Not being very knowledgeable of electronics, I thought that the senders were strain gages and didn't realize that they were just mechanical reostats. No wonder they are so affected by vibration. I"m amazed that these senders hold up as long as they do. The pictures were great. Thanks Roger. Link to comment Share on other sites More sharing options...
airhound Posted August 31, 2012 Report Share Posted August 31, 2012 Not being very knowledgeable of electronics, I thought that the senders were strain gages and didn't realize that they were just mechanical reostats. No wonder they are so affected by vibration. I"m amazed that these senders hold up as long as they do. The pictures were great. Thanks Roger. Woops! An afterburner, if you please...........Along with the eletrical component aptly explained above--how do liquids; fuel, oil, water, etc enter into the measuring function of these gauges? We omitted that aspect of how pressure sensors/senders work...in our discussion. Thank you again! Link to comment Share on other sites More sharing options...
Roger Lee Posted August 31, 2012 Author Report Share Posted August 31, 2012 The way these senders are built it doesn't make any difference as to the liquid for our use. The only difference in the senders is that some read 0-30 psi (fuel) and some 0-150 psi (oil). Water would work in them too. Link to comment Share on other sites More sharing options...
airhound Posted August 31, 2012 Report Share Posted August 31, 2012 The way these senders are built it doesn't make any difference as to the liquid for our use. The only difference in the senders is that some read 0-30 psi (fuel) and some 0-150 psi (oil). Water would work in them too. So, are the different psi ranges predicated on the size of the hole at the male end of the sensor? Why any liquid/fluid at all then? How do the fluids factor in any gauge's measurment function.....Thanks! Link to comment Share on other sites More sharing options...
Roger Lee Posted August 31, 2012 Author Report Share Posted August 31, 2012 The small hole is to help dampen pulsation or the readings would be jumping around. Some times these holes aren't small enough. Case in point, our fuel pressure steadiness is helped out with a Bing 35 idle jet in line and the MP is helped the same way. My MP is rock steady because I have a Bing idle jet in line up at the carb cross over balance tube. Link to comment Share on other sites More sharing options...
airhound Posted August 31, 2012 Report Share Posted August 31, 2012 Roger, I probably got it wrong and don't want to wear my welcome out.....but how significant is MP in our fixed pitch prop setup? And in general are we talking improving function by modifying the fuel system with an inline carb idle jet? If so, then is the mod function-----one of restriction? Link to comment Share on other sites More sharing options...
Roger Lee Posted August 31, 2012 Author Report Share Posted August 31, 2012 You aren't actually modifying anything operational. You are only dampening the impulses so the instrument reading is more steady. Go back and read the MP post. It will have everything you want to know. Link to comment Share on other sites More sharing options...
FlyRatz Posted August 31, 2012 Report Share Posted August 31, 2012 Hi Roger, good Job! In 2010 I did the job on our Dynon equipped CTSW. And yes, I used some kind of final solution and rewired the grounding. I installed a central grounding point (Picture #4) and routed a earth strap from here to every point which needs to be grounded (Battery, Rectifier, Starter, Panel etc.) in a star shaped way. No more grounding issues ever since. Greetings Markus Link to comment Share on other sites More sharing options...
Jim Meade Posted August 31, 2012 Report Share Posted August 31, 2012 Markus, Sehr Schoen. I am going to do essentially the same thing this winter. Note the bolt(s) that go through the firewall and act as ground points for the ring terminals on the equipment in the cockpit. Did you change those bolts or redefine the grounding system inside the cockpit? Did resolution of the ground straps have any affect on the CHT and oil temperature reading stability? In the situation where an item was grounded to the engine or other part, did you modify that to make a home run to the star terminal in picture 4, or did you continue to rely on case grounding? Did you do anything differently with the Dynon case ground? TIA Tchuess Jim Link to comment Share on other sites More sharing options...
FlyRatz Posted August 31, 2012 Report Share Posted August 31, 2012 Hi Jim, no I didnt change anything inside the panel. The Bolt you see at the third picture, is the one for the grounding base panel inside of the cockpit. In theory all grounded points have the same electrical level because of the identical earth straps leading to them from the central grounding point. This radical solution was necessary because in this CTSW the readings have been horrible unsteady. Since this change, everything is OK and all readings are rock steady. If weight is a considerable topic to you, you should prefer the solution of Roger. I think, my solution is at least three times the weight of Roger's. I think, it is a little bit of overkill but it's a german "heavy duty" solution and lasts for at least a million years ;-) The best to you Markus Link to comment Share on other sites More sharing options...
Adam Posted September 8, 2012 Report Share Posted September 8, 2012 I have been testing and looking into radio and instrument read out issues which are usually a grounding related. FD has the ground wire start at the water pump, down to the center engine mount bolt, up to the starter solenoid and battery, over to the reg/rec, and up to a bolt on the firewall and into the instrument panel and connected to either a bolt with all the ground wires stacked or a grounding block attached to this bolt. This bolt loosening and sometimes the other grounding points loosening cause radio and instrument issues. Simple things like low oil pressure or the oil temp bouncing 20F and other anomalies are related to the ground. I have experimented and think I have come up with a good solid solution. I have tried this on 3-4 CT's and seems to have corrected owner complaints. I take a #8 thin strand wire cable and solder brass ends on and then cover the connection with heat shrink. Make this 14" long. Then run that from the battery negative to the #3 cylinder drip tray screw which is located on top of the #3 cylinder to the rear. If you have an LS this is just an empty screw hole as your drip tray mount is different. I make another #8 wire that will go from this point on the #3 cyl. and routes into and through the plastic tubing or fire sleeve which ever you might have into the instrument panel. Make this wire 18" long. This end connects directly to the ground screw or on the ground buss. I leave all the standard CT ground wires in place and this is just an addition. After testing this on a few CT's it has worked very well as the resistance loss is less and there is no loss from loose connections or corrosion. It's about as solid a connection as we may see on the CT. My bouncing oil temps quit. They do fluctuate 3-4 degrees, but this is because of the sensor type and high temp for it which makes the reading a little less stable (per Dynon tech). Another had a 30 psi oil pressure, adding this ground wire setup increased it to 48-50 psi and nice and steady. Another issue was some radio interference and that went away. The ammeter fluctuation is reduced. It won't totally go away, but is is certainly reduced. I think this addition will help many, but it may not fix everyone, but it's a good start. When I go out to the field tomorrow I will take a few pictures and get wire length and post them here, but I wanted the testing out of the way first. p.s. Don't buy the normal #8 wire as the strands are thicker which make the wire stiff. The thin strand is very flexible. Make sure you buy the electrical solder connectors with the right size hole for the smaller screws. You can buy all this for a few dollars at most any Hardware store or my favorite Ace Aviation (a.k.a. Ace Hardware). Roger, what is the diameter of the screw holes on the 8 gauge crimp connectors you used? (1/4", 5/16") ? Link to comment Share on other sites More sharing options...
Roger Lee Posted September 9, 2012 Author Report Share Posted September 9, 2012 Hi Adam, How are things in sunny CA? When you reply try using the blue tab "Add Reply" either down at the bottom of the post page or at the top. The one in each post quotes everything and makes all the threads really long to go through. The ones on the #3 cyl. drip tray and the one that goes into the panel are 1/4". The one to the battery is smaller. 1/4" on the battery is too big. Link to comment Share on other sites More sharing options...
Adam Posted September 10, 2012 Report Share Posted September 10, 2012 Thanks Roger! Sunny So Cal is hot as Arizona lately! Seems the whole country is burning up! I'll miss Page this year. My co-pilot is pregnant and will be a little too big to make the flight in October comfortably! I sure hope it cools off sometime soon! I will be at the AOPA Summit in Palm Springs (FDUSA is going to "borrow" my new CTLS to use as a static display) so hopefully will see some of the crew there! Link to comment Share on other sites More sharing options...
207WF Posted September 11, 2012 Report Share Posted September 11, 2012 Adam: Does this mean you get to taxi in the parade of planes? WF Link to comment Share on other sites More sharing options...
Adam Posted September 11, 2012 Report Share Posted September 11, 2012 Yes... Although based on my schedule it will be John Gilmore that will do the taxiing! (I'll be out in Palm Springs on Friday). Link to comment Share on other sites More sharing options...
FlyRatz Posted June 24, 2013 Report Share Posted June 24, 2013 Hi again, I have some news to this old thread. At some earlier posts, I wrote that my new grounding scheme eliminated all erraneous EMS readings. You will be astonished that the horror show came back, when I installed a factory new 912ULS in this particular CTSW. For your entertainment, I catched a video which was taken in flight while the EMS was totally out of sync. The strange thing is, that the EMS behaves totally normal most of the time. But sometime it goes crazy. I know, that this must have something to do with grounding and the fact, that the engine was replaced, leads me to the following question: Why does FlightDesign connect the grounding cable for the engine at the engine mount and not directly at the engine?? What happens, if the electrical contact between the engine housing and the engine mount is not as good as expected?? There are rubber elements between the little ring-mount and the big engine mount. What if these rubber elements isolate the engine from the engine mount??? (OK, these are more than one question ) Look at the following picture. This is the contact-point for the engine grounding. Wouldn't it be a good idea to route a cable from this point to the engine housing?? What do you think?? I think it is worth a try. Best regards Markus Link to comment Share on other sites More sharing options...
Roger Lee Posted June 25, 2013 Author Report Share Posted June 25, 2013 Howdy Markus, It's been a while. Glad your still out and about with us. Hope to meet up with you again one day. Look at the very first post in this thread on page one. This is what I have been doing and so far it has eliminated all the ground issues many guys have been experiencing. Link to comment Share on other sites More sharing options...
CT2Kpilootroger Posted November 4, 2013 Report Share Posted November 4, 2013 Hi everybody, I am new on this blog. I own a CT2K since 2002. It has 940 hours now; all that time I flew it all over Europe. Never had any grounding problems until recently. The bolt holding the grounding cables together in the engine mount became loose and that caused a lot of problems. These days I have some small problems, the voltage in the first five to ten minutes after starting the cold 912UL is as high as 18V. After that it turns to the normal 13,5V. I also had a warning from the air traffic controller of EBOS that my transponder is not shown on his radar. Could this be caused by a new grounding problem? Has anybody seen the new video by Rotax about Voltage problems? Is it any good? Best regards Roger Link to comment Share on other sites More sharing options...
Roger Lee Posted November 5, 2013 Author Report Share Posted November 5, 2013 Okay now we have 3 Roger's here! (documentation not included ) That might drive a few batty. HI Roger, Yes it is possible. I would tighten all my grounds in the engine compartment and the one main one in the instrument panel. It might also be a god idea to hook up a better ground altogether. http://ctflier.com/i...ounding-issues/ Keep an eye on that high voltage spikes. It could be time for a new reg/rec. Link to comment Share on other sites More sharing options...
C ICEY Posted November 5, 2013 Report Share Posted November 5, 2013 Part of the hard start problems I encountered that ultimately led to my sprag clutch failure at about 1000hrs began in cold conditions, stored outside. the battery was a bit weak, but another telltale symptom (identified too late) was a loose ground wire, hidden behind the engine mount, going to the starter itself.... mike Link to comment Share on other sites More sharing options...
Airbear Posted December 28, 2013 Report Share Posted December 28, 2013 We recently added the additional ground wire as suggested here. We are still seeing very erratic oil pressure indications. The Flydat will show 40 psi - 90+ psi. All other readings on the Flydat unit hold rock steady. Should the oil pressure sending unit be replaced (again) in our 2005 CTSW? Link to comment Share on other sites More sharing options...
Roger Lee Posted December 28, 2013 Author Report Share Posted December 28, 2013 Have you removed the old oil pressure regulator parts in put in the three new parts. this was in the SB if you wanted the 2000 hr. if you had a newer engine. A 2005 wouldn't qualify, but you want the parts . It will most likely stabilize the pressure. This is one reason Rotax wanted the change was to stabilize the pressure. If it isn't a bad sender which is usually 80% of the time at fault then you need to replace these parts. The Rotax bulletin # SB912-057UL, dated Dec. 14, 2009 the Rotax oil pressure cap screw #841-983, oil pressure spring #838-122 and oil pressure regulator cone #857-230. Link to comment Share on other sites More sharing options...
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