Hi to all, I've just finished an S1 Ringmaster with a home made metal tank and no matter how rich I set it on the ground the engine (OS35s) leans out after 4/5 laps until its doing 4.5 sec per lap on 60ft lines. The tank plumbing is standard (no baffle) with muffler pressure.. There's something not right with this set up, Is there anywhere that shows the various plumbing setups? (Hope I've got the photo of my tank showing) Any help would be really appreciated...
Phil

Wes, Thanks for the reply, (and thanks for the compliments on my tank Its the 1st one I've made) As for castor content, the fuel is Model Technics Sport 5 (5% nitro) with 18% oil of which 4% is castor. I've replaced all tubing and pressure tested the tank in a bucket of water; all was fine. Could it be the castor content and if so why?
Cheers Phil

First of all 18% total oil is not near enough for that engine. It needs at least 25% oil of which the biggest share should be castor. The oil is what cools the engine, and after a few laps with low oil, the engine is overheating which inturn leans it out. If you add 20 ounces of castor to a full gallon of 18% fuel, you would have 29% total oil which would be good for that engine, and stop the overheating. It would give you close to 17% castor and the rest synthetic, which would be OK. It would also lower the nitro content a bit, but that should not cause a problem.

Here is a link with all kinds of good stuff.  If you scroll down a ways you will find diagram and various discussions of uniflow tanks.  I would just say that, except for the trainers, all my airplanes have uniflow tanks.  If open to the air, I put one of my stash of KK one way vales on the uniflow to prevent siphoning and shield the tank from out side air current influences.  If I run muffler pressure t the uniflow, I don't use a one way valve.

http://www.aeromaniacs.com/Tips.html

You might want to throw a plastic clunk tank in your box just in cast. Use it as a process of elimination. That will tell if you have your tank plumbing correct.

I tried so many tanks with my Ringmaster S1. Nothing would please me until I put a Sullivan 4Oz RST tank on the other side of the fuselage and plumbed for uniflow  like John Miller taught me. Since then I get nothing but perfect engine runs.

I attached the tank using 3M clear tape and set the tank with an offset so the engine quits at once. The offset was done with a foam that also help preventing fuel foaming.

Not purty but works amazingly well.

Martin

You want the uniflow vent to be roughly in the center up & down (actually you want it roughly lined up with the needle valve), and close to the outside wall of the tank. 

Tim and Big Bear! Thank you both
BTW I really do need the back of my legs slapped coz I've been advized before on this forum to use high castor fuels with the old OS engines..  I've ordered a bottle of castor at the LHS should be in Friday
Phil

Wanted to let you know how things went with the S1 after I added castor to the fuel. I made the oil up to 25% (from 18%) and tally ho! the motor ran great. Thanks to all for the advice....
Phil

Great news, Phil! 

All the "old" iron piston engines need the castor for cooling.  Yeah, I know that there are some who run little to no castor and report everything to be fine, but I have never found that to be the case.

Randy Smith "pinned" a great article on fuel at the top of the engine section.  The best one I have ever read and good info for everyone.

Bill

Hi to all, I've just finished an S1 Ringmaster with a home made metal tank and no matter how rich I set it on the ground the engine (OS35s) leans out after 4/5 laps until its doing 4.5 sec per lap on 60ft lines. The tank plumbing is standard (no baffle) with muffler pressure.. There's something not right with this set up, Is there anywhere that shows the various plumbing setups? (Hope I've got the photo of my tank showing) Any help would be really appreciated...
Phil

    You need a fair bit of oil, but there are two other pretty common issues. The 35S came with two venturies. For stunt, you want the smaller of the two. The big one looks like a straight cylinder on the outside, flush with the boos in the case that it goes into. The smaller one is the same diameter as the big one right next to the case, but is then cut down a little bit so the diameter of the open end is smaller.

   A related problem is that your tank it not ideal for fuel draw. Your tank is very wide, about as wide as the cylinder is high maybe 2-2 1/4" wide. When the airplane takes off, the engine has to draw fuel "uphill" against centrifugal force. This makes it go lean, and the faster it goes, the leaner it gets, so it goes faster, etc.

   The other is that it's a Ringmaster, so there is a lot of vibration, which can cause all sorts of issues - like foaming fuel. The OS is better than a Fox as far as vibration goes, but it's not immune to it, either.

    Brett

Hi Phil,
The clunk tank pictured above has a fixed uniflow vent which doesn't move around because it's just a bent up piece of copper tubing that is where it is unless you twist it a bit so you don't have to physically move the tank up and down to get even inside and outside maneuvers. Proponents of this style of hard vent extol its virtues because the engine thinks the tank position (in a vertical sense because you know things like to flow down hill) is the same as the uniflow vent height. They are correct and on a built up ship where the clunk tank rectangle is is on the skinny side vertically, fuel stays in a more concentrated location and some smart guys would have you believe this works just fine all the time....great 4 them and probably even better if they're using muffler pressure.
On the other hand per profile application (you know we mount tanks on side of fuse) I have been best served by a tank that is rotated 90° from where the full fuse gents mount theirs. That affords minimized centrifugal loading or per Brett, less of a sense of uphill resistance encountered by the engine to suck fuel out of the tank once the plane starts motoring around the circle.
Back to the singing vent thing:
I've got a short copper tube that makes it into the tank about 3/4 of an inch to which I connect just a raw piece of silicone tubing (this would be the uniflow vent and it's at the 9 o-clock position on the stopper. 4:30 is the feed line and 1:30 is the vent for fueling the tank which gets plugged once full. The uniflow vent tube (once attached inside the tank) is nothing more than a loosey goosey piece of silicone tube which is captured and constrained by a 1/32 loop of music wire that's been soldered to the clunk.
Alright, so what happens (and this is where the main difference is) is that the vent now moves around with the clunk and the important part is that it stays submerged in fuel and goes for a ride with the clunk per G-forces just like the fuel. This is a big deal on a profile because the tank sits tall in a vertical sense, and for the engine to run right, the vent must not become uncovered or the engine will go rich. The uncovering thing is the trouble part
with the style shown above and this solves it.
BTW
When the tank is held with the stopper straight up, there should be no bias in the clunks location AKA the plumbing should run right down the middle of the tank nose to tail (this takes a lot of fiddling and bend, rebend and twist silicone tube and retighten stopper) and more bad news is if it runs faster doing loops one way than it does doing the other, you're going to have to physically move the tank (will be consistent 4 sure) instead of just twisting a tube that's been inconsistent per my encounters.

Grady! Gotcha this time!! Thanks for taken the trouble to explain it. Like a double clunk.
Tim thanks also, I didn't fancy cutting into the leading edge.. If I have any more issues with the engine run I will consider the plastic tank (double clunk) fitted inboard as suggested by Martin...
Thanks again
Phil