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Oil Temperature sending unit
Many of you know this but for those who do not, I'm working on a
Christavia Mk4 with a Ford V6 for the engine. Last winter our EAA chapter invited the local DAR to speak during a meeting. The guy turned out to be a crusty old codger who appeared to be of an age where he could care less what anyone thought of him or what he said. He basically dissed any and all alternative engines. While listening to him I came to realise that this guy would likely be the person who inspected my airplane. I'd been planning to test the engine extensively prior to actually flying, but this meeting produced the impetus to actually make that happen. I'm at the stage of construction where I need to finalize the engine installation before I can finish the fuselage. The shape of the fuselage and the firewall depend on the engine installation. Before I finalize the engine installation, I need to put it through it's run in and extended testing. I built an engine test stand that is tall enough to allow the engine to run with the prop installed. It's fully independent, with a fuel tank, fuel pump, battery, radiator etc. etc. I mounted casters on the stand so I can winch it into my pickup and cart it off into the woods to run the thing without bothering the neighbors. I've been installing instruments on the instrument panel of the test stand so that I can record readings in a log that I will show the DAR. Installed on the test stand instrument panel a a tach, a cooling system pressure guage, oil pressure guage, oil temperature guage (more about that later), water temperature guage and a hobbs meter. Some of the guages I got from Summit Racing, the tach came from "Datcon" after seeing the tach in Sport Aviation on a homebuilt 3/4 size Jenny. About the oil temperature guage. It also came from Datcon and it arrived without the sending unit. This turned out to be a little problematic in that Datcon was a distributer and did not sell pieces to private individuals. The told me I had to buy the sending unit from one of their distributers. So they gave me several to choose from and I called the first company. They never heard of Datcon and were surprised to hear they were designated distributers. Datcon is owned by Maxima Technologies and they produce Stewart Warner guages. When I mentioned that, they allowed as perhaps they did have some of those, but they could not find the sensor, even when I gave them the part number. Next business said they did actually have the sensor, but did not want to send it to me. I could drive the 50 miles to get it though, if I wanted. I didn't. I had the additional problem of figuring out where I could put the sensor. I did not have any outlets left to use as the one oil port was occupied by the oil pressure sending unit. On the internet I found a VDO site for BMW's. They had an oil pressure sending unit that replaced the oil drain plug. I thought that was a terrific solution and bought one immediately. I hoped that it would end up being the same size as the drain plug in the Ford, as the Ford was a Windsor engine and was all metric. It wasn't, of course. Now I had to figure out how I'd install this thing. I measured it and found that it was 12mm size with 1.5 pitch threads. I checked in my tap and die set (terrific purchase a year ago, I use it all the time) and found that I did have a 12mm tap that was 1.5 pitch. I could not just punch a hole in the oil pan though, I needed something that would hold a few threads. Also, the oil pan was not only installed and painted, all the bolts that held it to the block were drilled and safety wired. It would be a big job to removed it to weld a flange on the inside. Instead, I picked up my angle grinder with it's flapper disc and cleaned off the paint on left side of the oil pan where there was a flat surface. I scrounged around the shop and found a rectangular piece of mild steel that was about 1/4" thick. I scribed a circle about two inches in diameter and nipped off the corners on the band saw, then rounded things off more on the bench grinder. This piece of material already had a hole in it, which I'd ream out to the proper size to tap, and I used the hole to chuck the piece onto a bolt and tightened the bolt into the drill press. Turning the press on, I used my angle grinder to trim the piece down a bit and round over what would be the outer edge to facilitate welding. Then I drilled out the hole using the 11/32 drill recommended on the tap, and clamped the flange to the oil pan. Using a medium size tip, and a large flame, I heated the flange till it got molten, and then slipped the flame to the oil pan while adding filler rod and made sure the puddle spread out into a good weld. This technique worked well to concentrate the head on the thick flange rather than the thin wall of the oilpan which prevented burn through. I tacked two sides, then removed the clamp and finished welding all the way around. It was a tough welding job because I could not rest my hands on anything and had to hold them out at length while holding the tip and the filler rod. But the welds looked good when I was done and I put the torch away while letting the flange cool. Now, using the hole as my guide, I drilled through the oil pan. Then I fixed the tap in the handle and smeared the tap with grease to pick up as much of the metal shavings and particles as it could. After inserting the tap into the hole and firmly turning it, trying to keep the tap from wobbling, I finally got the tap started and turned it in until the hole was completely threaded. I lucked out in that the flange was sited in a spot where I could turn the tap handle without any interference from engine parts or the test stand. Of course, this was after I removed the starter, which was blocking access to this part of the oil pan. Once the hole was tapped, I coated the threads of the sending unit with teflon paste and threaded it into the hole. It snugged up nicely. The unit does not have a screw to attach the lead to it, it has a flat protrusion. Looking at it sideways it looks like a T, looking at it from above it looks round. I have a box of wire connectors and found a female spade that slid right onto it with enough resistance to hold itself in place. I crimped the wire to it and connected to the temp guage. All the guages are basically wired identically, which is a great relief and makes for sanity while wiring. The same post on every guage is connected to the sensor, the same post to ground, the same post to the ignition switch. Guage lighting is handled virtually the same for each guage. There is either a post to connect the lighting lead to, or the bulb has a socket with a power and ground coming out of it. But in all cases, the bulb is at the top of the guage. Nice that there is this type of industry uniformity. Next up, now that all is pretty much done, is to finalize the carb base plate installation (nothing is final torqued yet or sealed), then adjust the carburator float level, add coolant, add oil, prime the oil gallaries and try cranking it. The PSRU is not final adjusted yet, that had to wait for the engine to be running to make sure that the belt runs centered in the cogs. Once that is adjusted and confirmed, the bolts that hold the cogs adjustment in place will be final torqued and safetied. The engine will be checked for leaks, run till it's warmed up, then shut down and the oil drained and replaced, and the oil filter replaced. With fresh oil, I can then mount the prop and begin to run the engine up against the load of the prop. Hmm, maybe I should buy myself a cheap motorcycle helmet to use while standing in the prop blast... Corky (tie it down firmly) Scott |
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"Corky Scott" wrote in message ... snip The engine will be checked for leaks, run till it's warmed up, then shut down and the oil drained and replaced, and the oil filter replaced. With fresh oil, I can then mount the prop and begin to run the engine up against the load of the prop. Hmm, maybe I should buy myself a cheap motorcycle helmet to use while standing in the prop blast... Corky (tie it down firmly) Scott I think you'll be amazed at how quickly a loud engine/prop on a test stand will make bystanders retreat. We had a fellow in our EAA chapter run his Subaru 6 cylinder on a test stand at one of our meetings. The members all started off about 10' from the test stand. As soon as it started, people backed off to 20', and when he wound it up a little, the chickens among us ducked around the corner of the hangar. It was much quieter and less windy there. KB |
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"Corky Scott" wrote snip I built an engine test stand that is tall enough to allow the engine to run with the prop installed. Snip With fresh oil, I can then mount the prop and begin to run the engine up against the load of the prop. Hmm, maybe I should buy myself a cheap motorcycle helmet to use while standing in the prop blast... Corky (tie it down firmly) Scott If you are running the same prop that you will be flying with, you will not be getting full RPM, for break-in, and for maximum HP (read heat). Will this be a problem? -- Jim in NC --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.778 / Virus Database: 525 - Release Date: 10/15/2004 |
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