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Archive for September, 2011

Oil Pump & Accessory Housing

Things haven’t been going so well for my little airplane these days. I keep getting stranded away from home because my oil pump won’t seem to stay primed. When I start the engine, it fails to make oil pressure. There are all kinds of hocus pocus tricks you can try to get the pump primed again and I’ve tried them all. TWICE!! I finally reinstalled my custom made fitting on the left side of my engine case and used a T-fitting to add a primer line (the orange line in this picture). It worked, but not for long…

The long and the short of the situation is that my oil pump gears and/or the oil pump housing had worn beyond tolerances and could no longer make pressure. This is my accessory housing after I removed it from my engine. The plate in the middle covers the oil pump itself, which consists of 2 hardened steel gears.

Now: I’m no engineer, but even I can see where putting 2 hardened steel gears inside an aluminum housing might lead to some wear issues.

This is the aluminum plate that covers the oil pump and holds the gears in place. You can see where the gears have caused some wear marks on the plate. A lot of people are successful in restoring oil pressure by lapping this plate and reinstalling it. By the time I had gone to the trouble of removing my accessory case, I was going for the sure thing… not a maybe.

Here are the gears in the housing. The square drive on the lower gear engages on either the crank or the cam (can’t remember now) which then spins the gears. The backside of the top gear (not shown) has the square drive output for the tachometer.

You can see the wear on the housing from where the hardened steel gear has rubbed. There was a similar wear pattern on the other side of the housing, too.

I could have the old housing remanufactured for $850 or purchase a new housing for $905. The new housing is on the right. :-) Ouch.

The new accessory housing from the backside. Sure is pretty with that gold finish…

I’ve never actually painted a chess set, but I imagine it to be very similar to taping off and painting this accessory housing.

I reinstalled the accessory housing. Sounds simple enough, right? Wrong. I needed all new gaskets for everything attached to the accessory housing including: Both magnetos, the starter, the generator (capped), the tach drive housing and, yes, even the oil sump. By the time I purchased the accessory housing, a new oil pump kit (gears and the aluminum door) and all the gaskets, I had spent the better part of $1500. All I can say is that I’m glad I could do the work on my own because I’m sure it would have been another $1000 in labor if I was paying somebody else to do it!


Plenum, Oil Cooler and iFly700

Once I decided to put my oil cooler at the bottom of the cowling, I needed to re-work the aft portion of the left side of my plenum to remove the air outlet for the oil cooler. My poor plenum has been hacked up and re-worked beyond recognition. I used clay to re-shape the aft portion of the plenum.

I used PVA mold release to keep the glass from sticking to the clay and then laid up about 4 layers of 6 ounce cloth. Complex shapes are pretty easy with clay and fiberglass.

Once the resin cured for the top half of the plenum, I trimmed it to fit and then covered it with duct tape in preparation for the next fiberglass workday.

Once again, I used PVA mold release on everything I didn’t want the resin to stick to. I made a lip for the top of the plenum to nest inside when the plenum is installed. Worked out pretty slick.

I finally got around to installing my tailwheel attach point fairing… sorta. I used duct tape for now because I wanted to make sure it didn’t cause any problems. It fits nice and cleans up the look a bit so I’ll probably have it painted when I install my wheelpants this winter.

Here’s a profile shot of my new oil cooler inlet. I think it looks butt-ugly so I’m not sure it’s going to last long. We’ll see how effective it is…

Being the absolute gadget freak that I am, I bought a new toy. You can never have too many GPS’s, can you? The new, big, GPS is an iFly700 from Adventure Pilot. I think it’s a great value at a little less than $600 for the unit itself and a year’s worth of sectional charts and airport facility directory. I hard wired it to the master switch and installed an external GPS antenna under the cowling.


Remote Filter Installation

With the fiberglass work mostly finished for the new oil cooler installation, it was time to finish the installation of the Airwolf remote oil filter installation. The gold piece to the left on this picture is the oil pickup adapter from Airwolf. It replaces the original oil screen. You’ll notice that I’ve installed a nifty AN fitting with a 1/4″ port for an oil pressure transducer. Summit racing sells these fittings as test fittings, but they work well to provide an additional oil pressure pickup port. I now have 2 independent sources of oil pressure indications. The primary source is a line coming off the left rear side of the engine case. That line goes to a transducer that drives the oil pressure gauge. The pressure switch shown in this picture turns on a low pressure light when there is less than 5psi and activates my Hobbs meter when there is more than 5psi.

This is a birds-eye view of the remote oil filter installation with all the hoses attached. If everything goes well, I can accomplish an oil and filter change without removing the lower cowling. The silver piece below the gold piece is made by Steve’s Aircraft. It spins on the oil filter adapter to provide ports for oil cooler lines.

I ran into a little problem when I ran the engine for a leak check after installing the spin-on oil filter adapter and the Steve’s Aircraft oil cooler. This stud that comes out of the Air Wolf adapter is slightly too long to allow the Steve’s Aircraft adapter to set properly against its rubber o-ring seal. The 1/32″ gap allowed oil to spray out between the parts.

Looking back on this picture taken before the leak check, you can see a little daylight between the silver part and the gold part. I incorrectly assumed that when the silver piece bottomed out it was bottoming out against the o-ring seal when it was actually bottoming out on the treaded stud protruding from the gold part. Luckily, I’ve got a good friend who’s a retired machinist who’s got a lathe in his garage. He took off about 1/4″ from the stud and all is now right with the world.