Thorp Air Command - T18.net

I have a O-290g conversion, with O-320 gear case. It has the old style "velocity valve" in the case. As the oil warms up and gets thinner, the spring pressure closes the valve, diverting oil thru the cooler, then the screen. This requires a winter cover for the cooler on my plane.
I could replace the screen with a thin, home made mount for a spin on. Automotive filters come with a bypass relief valve inside, so the Lycoming oil filter adapter with bypass relief valve and Vernatherm isn't the only way to get a filter.

Is this the remote filter with a Vernatherm?

Ebay#130793426180

I've been using automotive filters for 20 years, with an engine-mounted adapter I designed & made that includes the vernitherm & oil temp probe. It orients the filter vertically for nice, clean changes. Two friends & I decided to design & build our own when nothing was available commercially that would fit the Thorp & some other airplanes, and I wanted to avoid extra hoses, fittings, etc. Access to a milling machine and a big hunk of aluminum is necessary. The Lycoming spin-on adapter, we all know, presents a clearance problem on the Thorp. One of the main reasons we went with automotive filters was because the aircraft filters at that time didn't contain a built-in bypass valve, which was built into the Lycoming adapter. We could avoid having to incorporate a valve into the design by using filters with built-in valves. Also, the price at the time was about 1/3 that of the Champion aircraft units. We did our homework, & tested many different brands & models of filters. We built a test rig, using an old grease gun to pressurize them to failure, & we also cut them apart to measure shell thickness, filter media quality & square inches of area, etc. We chose filters based on knowledge of the very high flow rates necessary with a Lycoming - with it's positive displacement oil pump, there WILL be that amount of flow through a full-flow set-up, and there's nothing as useless as a filter that's bypassing all the time. A Porsche 944 filter was chosen because of it's engine having similiar oil flow rates & pressures. They had greater filter surface area than the aircraft units, a shell thickness of 0.015", and were basically better. Originally I would buy the German-made genuine Porsche filters by the case at about $6 each. I've used the K&N filters now for many years. For what it's worth, some of the worst filters we tested were made by Fram.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

I got lucky and chose the K&N HP 2008 some years back. I chose it because it could be safety wired and had a bypass. I mated it to a Summit Racing remote mount that was 35 bucks. Been working great for several hundred hours. I still change my oil at 25 hours because I do not like the look of it at 50 hours. Recently, I have been adding a cup of MMO five hours before oil changes.
Cubes

http://www.knfilters.com/search/product ... od=hp-2008
This is a pull from K&N's site. Nice filter. No pressure bypass. That could be a bad thing if your system does not have a bypass to assure cold oil flow to the engine.
However, if you don't need the filter to have that bypass, that's a good thing too. On our Cessna 172, the spin on filter is oriented as yours, with the closed end down. The bypass valve is in the bottom. Carbon grit settles out into the bottom, so when the bypass opens on a cold engine start, that carbon is washed right into the engine. In a Continental O-300, you will witness the result right after take off, as the oil gets warm and the oil pressure drops rapidly. The carbon sticks in the oil pressure regulator after it has passed the full length of the oil gallery.
On filters with a bypass valve in the bottom, I would prefer to mount them "Bottom Up" so the particulate carbon and swarf stay trapped in the filter jacket near the rim.
Yes, it would be messier when changed.

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Scott Emery
EAA Chapter 326
T-18 N18TE

The bypass should never open, in my opinion, unless the filter clogs or you do something real dumb like trying to start with straight weight oil at very cold temperatures & no pre-heat. I use a semi-synthetic multi-grade and always pre-heat below 30 deg. If the filter is sized correctly - plenty of surface area - and you're running the proper oil for ambient conditions, and the bypass check is designed for a reasonable pressure drop there should be no bypassing occuring. If your filter is bypassing frequently, or at all, during warm-up, something's very wrong. You'd do better to scrap the spin-on and go back to a filter screen & housing. Also, the filters I use have the bypass inlet some distance from the bottom of the filter, which would tend to at least minimize the pick-up or flush of any particles laying in the bottom of the can. Anyway, the vast majority of the particles, if any, are imbedded in or sticking to the filter media. But the bottom line is, the bypass valve should never open unless something is not right in design or application, or if the filter clogs (and then you sure have other problems anyway).

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Mr. Evens machine work is a piece of art ! I wish I had that kind of talent . Besides Mr. E , I know of one other man that could pull off this kind of metal work..Mr. john Kerr . I had to go the other route and buy mine and slightly modify it to fit my application. Both the engine adaptor and the remote came fro Canton Racing Products . I choose this Company because they make the units in the USA and they are solid billet aluminum. The engine adaptor can be rotated to any position to fit the hoses . Right now I have 110 hours on the unit and no problems . As far as the oil filters , I looked at at lot of them . Including the K & N (with the safety tie ) , but after weighing the pros and cons I went with the Tempest oil filter (has a built in magnet to trap the metal ) and after a 10% discount from Spruce for a case purchase they were only a few more dollars than the K & N filter...I like the magnet thing ! I feel much better putting on a Aviation filter (with magnet) for $14.00 than a non aviation filter for $10.00 . I just sleep better ! No disrespect John ...you the metal carving man !

RB

I think you guys are very wise to use aircraft filters. If I was starting over today, I would probably build an adapter to use them. As I said, there was nothing available commercially like what I wanted, when I designed & built mine. It can be a little bit of a problem if you have a prop governor in the way (I don't), but otherwise, it's the simplest way to go. The auto filters were a lot cheaper, and the built-in bypass valves cinched it for me. Now, the aircraft filters have them too. I always felt a little concerned when I would see some of the auto filters that were being used by guys with automotive remote mounts. The K&N filters I use are rated at 12 to 16 GALLONS PER MINUTE! Believe it or not, an O-320 Lyc at 2700 rpm will be in that range. It's positive displacement pump WILL move that volume of oil through the filter, if it's a full-flow setup, since the oil filter is the first thing in line after the pump. It's a different situation with a partial bypass setup of course, with the filter in line with the oil cooler, but the flow rate will vary and still exceed the limits of many auto filters. I've seen quite a few that are rated as low as 3 gpm. Excessive flow rate = excessive pressure drop = bypass, or filter media rupture, or worse.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

It looks like one, Bob. It could probably be used on an engine without a Vernatherm, and instead having the spring-loaded check valve assembly that is used to send oil through the cooler circuit when the viscosity is high. In other words, this would probably be used in the oil cooler circuit. I'm just guessing, but it would probably require you to remove the ball & spring. Either that, or it could be used on a newer model engine with the right adapter plate & fittings for where the filter screen housing w/Vernatherm normally mounts.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Scott is right, Cubes. The HP-2008 doesn't have a bypass. You might have mistaken the anti-backflow feature for a bypass. You might want to consider the HP-2009 http://www.knfilters.com/search/product.aspx?Prod=HP-2009. It has a bypass, is a little longer and just slightly smaller in diameter, with the same thread size. It's a common Ford (among others) replacement. It has the usual K&N high flow rating. It's a good filter. There are probably other alternatives from K&N also... I'm just familiar with the HP-2009.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

That's one slick piece you got there John, mighty fine work. The firewall forward on your bird is as tidy as an un used Surgical room. You are a craftsman, no doubt.......Dan

JE's machine work should be in an art gallery ! Muey Bueno !

RB

Dan and Rich... thank you for the great compliments. I see so many beautiful Thorps, and you guys have 2 of the nicest. Good workmanship & the love of a great design continues, and has been there for us for almost 50 years. I think of John Thorp, Dean Cochran, Walt Giffin, Bill Warwick, Lu Sunderland, Russ Basye, Bill Cordoza, George Leider, Ken Knowles, B.C. Roemer, Chuck Borden, Gary Green, John Shinn, John & Lee Walton, Lyle Trusty, the entire Ginn family, Bob Dial, John Kerr... I can't do justice to this list - I shouldn't have even started it - there are just too many! I feel completely out of my league when I see how Bob Highley has continued to improve his beautiful bird after all these years, and the workmanship he and Bill Williams display with so many things - scratch-built metal cowls, etc. YOUR engine installation should be in a museum, Rich! I could go on & on - there are so many wonderful Thorps out there, but the bottom line is that I am honored to be a small mark among such a group of builders, owners and re-builders, without exception.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

John: I think I am going to kiss you ! BOOM !

Rich,,,Can you borrow a kilt from Fraser first?

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE