The International Cessna^® 170 Association

Anyone put a restrictor on the fitting that leaves the case of the engine? As I was searching around the airport for a mandrel one of my friends recommended I put on a restrictor and be done with it. He told me to make one by soldering a fitting and drilling a smaller hole. Makes sense I guess.

A restricter fitting is recommended to restrict the overboard pumping of oil in the event of a pressure line breakage.

Mike, get an AN 816-2D which is aluminum. Solder it closed. Drill it out with a #60 drill which is .04" or as large as a 1/32" which is .03125".

See this thread for discussion: http://www.cessna170.org/forums/viewtop ... restrictor

Correction: Had a brain fart. I must have found a steel AN 816 or maybe I got lucky and found a brass AN 816-2B. But the solder won't work with the aluminum. I just tried it.

Bruce,
What kind of solder do you recommend for closing down the hole in that aluminum fitting?

I would think this stuff might work pretty good.
http://www.ebay.com/bhp/hts-2000-brazing-rods
I have a friend that has used it for repairs on his ATV with amazing results???
Gary

Thanks Bruce! Sounds like what I was told out at the airport today! Thanks for the part number for the fitting.

blueldr wrote:Bruce,
What kind of solder do you recommend for closing down the hole in that aluminum fitting?

I used regular old 60/40. Clean the hole and use flux. Nothing fancy. Same stuff I use on copper water pipe.

Under the circumstances above, I'm amazed that 60/40 lead/tin solder will bond to that aluminum fitting.

blueldr wrote:Under the circumstances above, I'm amazed that 60/40 lead/tin solder will bond to that aluminum fitting.

I thought the same thing until I tried it.

Of course now your making me wonder if I might have used a silver solder. But I don't think that silver would work any bettor or worse than lead/tin. I know one thing I used what was on my bench and I don't have anything exotic there. Now I'm going to have to get a fitting and do it again to be sure I'm reporting correctly.

Bruce Fenstermacher wrote:

blueldr wrote:Under the circumstances above, I'm amazed that 60/40 lead/tin solder will bond to that aluminum fitting.

I thought the same thing until I tried it.

Of course now your making me wonder if I might have used a silver solder. But I don't think that silver would work any bettor or worse than lead/tin. I know one thing I used what was on my bench and I don't have anything exotic there. Now I'm going to have to get a fitting and do it again to be sure I'm reporting correctly.

BL your sharp as a tack.

Correction: Had a brain fart. I must have found a steel AN 816 or maybe I got lucky and found a brass AN 816-2B. But the solder won't work with the aluminum. I just tried it.

One might also braze a brass fitting. (I believe there's an actual part no. for this restrictor fitting....I'd look in my records but our home desktop computer died and this is the first time I've logged onto (another) new computer and haven't transferred all my data from the old hard drive yet. They keep making things that aren't back-compatible....)

If you have a brass fitting I'd just solder it. In order to braze it you need to melt the brass rod and the heat will likely melt the fitting. All the "factory" parts I've seen are brass with solder. BTW brass AN fittings are not easy to get.

I don't remember if this fitting does have a part number. I know the primer fitting that sprays fuel in the manifold has a part number but that is different.

Here is another solution,

Tap out the fitting for a 1/4-20 set screw. Use lock tight to set the screw then drill it. The AN816-2 fitting I have is already a perfect #7 size hole for the 1/4-20 threads. If you wanted to use a 1/4-28 set screw you would have to drill out the AN816 with a #3 drill according to my charts. You would also need a bottom tap to get enough threads in the fitting to hold the set screw.

What do you do when that set screw comes out an drops down into the engine? (Unlikely, I know, but if you recall Voorhees story about the illegal oil restrictor fitting that caused the loss of the airplane..

Maybe put the set screw in the pressure-line side...?

I like the brazing or silver soldering idea best....but I KNOW there's an actual PN for this thing, and who cannot afford the price of airplane parts?

To make a restrctor fitting, use a brass or steel fitting, either may be bonded with 50/50 or 60/49 solder using a soldering iron and a flux. Silver solder will also do a nice job, but a soldering iron will not produce the necessary heat and a torch will be required to generate enough heat to melt the silver solder. Use of a torch requires diligence to keep from burning the base metal surface which will preclude acquiring a proper bond. A number 60 drill hole will be fine but if you're drilling into lead based solder you must be very careful to keep the little no. 60 drill bit from biteing into the solft solder too quickly and snapping off. Drilling into a soft medium must be done carefully to keep the drill bit from grabbing.

Here's how the Stearman guys do it.
http://www.stearman.net/index.php/oil-p ... estrictor/