If you are wondering why the oil pressure is hard against the stop, I had the 2 connections to the oil pressure sender the wrong way round.
Ian W From: [email protected] On Behalf Of Ian Williams Sent: Sunday, 29 August 2021 12:16 p.m. To: [email protected] Subject: RE: [DOG mailing list] FW: Dimona stuff This is not a great picture but does show the taco and hour meters plus the real cool fuel computer and CHT Actually we redesigned the engine baffles and it runs if anything too cool. It is real sad to see what is going on over there. I have been following youtube posts by a Dutch woman motorcycling around the world ( Itchyboots) Totally fascinating to see how normal people live once all the egocentric crap and power and control drama has been scraped off From: [email protected] <mailto:[email protected]> On Behalf Of Michael Stockhill Sent: Sunday, 29 August 2021 11:56 a.m. To: [email protected] <mailto:[email protected]> Subject: Re: [DOG mailing list] FW: Dimona stuff Nah. You guys think we have slipped over the edge! On Sat, Aug 28, 2021, 5:52 PM Ian Williams <[email protected] <mailto:[email protected]> > wrote: Thanks Michael. I was thinking that the rest of the world thought we had slipped over the edge. I will have another go at sending the picture of the hour meters and taco Sent from my iPhone On 29/08/2021, at 11:48 AM, Michael Stockhill <[email protected]> wrote: Well that sounds slick, Ian. The tubes delivered your text all the way across the pond(s). Michael On Sat, Aug 28, 2021, 5:42 PM Ian Williams <[email protected] <mailto:[email protected]> > wrote: From: Ian Williams Sent: Friday, 27 August 2021 4:30 p.m. To: '[email protected] <mailto:[email protected]> ' <[email protected] <mailto:[email protected]> > Cc: '[email protected] <mailto:[email protected]> ' <[email protected] <mailto:[email protected]> > Subject: RE: Dimona stuff A slight addition …. Of course the other end of the pressure switch is connected to ground. So no hour meters work until you are in the air. When engine is stopped in the air, the Airframe one keeps going and the engine hourmeter stops. From: Ian Williams Sent: Friday, 27 August 2021 4:25 p.m. To: '[email protected] <mailto:[email protected]> ' <[email protected] <mailto:[email protected]> > Cc: '[email protected] <mailto:[email protected]> ' <[email protected] <mailto:[email protected]> > Subject: Dimona stuff Hi Kurt and Michael, I must have bad breath or something because some of my posts to the DOG group seem to vanish into free space. However I hope I can help Because our Dimona was ex Thai, it had a lot of wiring which was not needed, so I completely re wired it. Rather than use the original cable driven taco, I installed a VDO electric taco Part No 333-953 driven by a little Hall effect sensor from Aircraft spruce which screws into the bottom vent hole of the Slick magneto. A real plus is being able to calibrate it using a 50Hz mains sample … ie 50Hz equals 3000 RPM. Refer to the attached picture … the 2 hour meters are also from VDO. The way I connected them is the common (-VE) of both hour counters connected to a small pressure switch (HERGA Manuf part No 6743-0003) .. operated by pitot pressure at around 30Kts. The positive end of one switch (airframe) connected to the plus bus, the other (engine) connected to the relay next to the voltage regulator on the right hand side of the firewall looking forward. If you refer to the wiring diagram on page 25 of the service and maintenance manual, notice the oil switch (the oil pressure sender) has 2 connections (actually 3 if you consider the earth being the case) It is 12 and 17 …. One output drives the VDO oil pressure gauge (15) and the other is a switched output driving the relay (9) That relay when active enables the voltage regulator to work only when the engine is running. Presumably a cunning trick to keep the current draw as low as possible when the engine is off soaring. So the plus supply for the engine hourmeter can be taken from the output of that relay. It is a real simple system and has worked faultlessly for 500 plus hours. Of interest, I have since replaced the Cyl Hd temp gauge with a MGL 4 cyl colour barograph unit I would be interested to know if you actually have received this email. Best regards Ian Williams ZK-GCB
