Nah. You guys think we have slipped over the edge! On Sat, Aug 28, 2021, 5:52 PM Ian Williams <[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]> wrote: > >> >> >> >> >> *From:* Ian Williams >> *Sent:* Friday, 27 August 2021 4:30 p.m. >> *To:* '[email protected]' <[email protected]> >> *Cc:* '[email protected]' <[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]' <[email protected]> >> *Cc:* '[email protected]' <[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 >> >
