Thing is the smaller engines are less prone to corrosion than the 999. All same materials. As a matter of course I ventilate the 777 too. They are now happy engines. The 9-90 is now at flight 160! (flights around 10-15 min). Mechanically still quiet. Remember Enya 4 strokes? The rear cam area could rust out in one overnight. I learned quickly to put a DuBro pressure tap on the cam housing so that at the end of the day I could flush out the crank case and cam housing. That stopped the corrosion in those engines.

Just curious, it's been several years since I was flying with glow fuel. I understand how water vapor can get into an open bottle of fuel, but if you are sealing your bottle after each fueling, how does enough moisture find its way into the crankcase after a day's flying to create that kind of crud in your engine? Is that moisture that's sucked into the motor from the air, then left in the crankcase? When I was flying glow, it was just the typical single-cylinder 4-stroke motors. I never did anything to them in between trips to the field, and I never experienced an issue like this...

OK, I found out what happened to my UMS Evolution 7-77 seven cylinder radial engine on Saturday. The problem was not with the engine. The 4200 MAH nimh receiver battery failed causing the throttle to go into fail safe and a loss of some control of the ailerons. That battery only had two flights but did set for some time. It was charged a full 24 hours before flying but caused a rough/crash landing. I still need to inspect the engine further but one pushrod was lost and one pushrod was bent. I am not sure if there is any more damage to the engine but there was a lot of damage to the BH Corsair. What a shame that the receiver battery with so little use could cause such damage.

Best wishes and good safe flying.

Heli-NuBee (AKA Roger the radial rabbit)

I have 10 flyable airplanes all with 4 stroke engines mostly twin cyl. and one is a o.s. 320 4 cyl. which btw is 7 years old, all planes are at least 5 years old and I have never put any kind of rust inhibitor or any thing else and sometimes were just put away and I have only had to replace bearings on 3 of my Saito engines after about 3 years running on them, my o.s. 320 4 cyl. after seven years on the Christen Eagle bi-plane the bearings are smooth as a baby`s butt, and still runs strong 4 of my planes have saito engines and the rest are O.S. engines, only one time did I replace bearings in my O.S. 300 twin, after 5 years running, and this 9 cyl. Evolution engine is the most frustrating after trying to really take care of the bearings but will now have to take extra ordinary care and bathing the bearings with air tool oil and going through the air pumping "drying out moisture" procedure, I guess is the only way to manage these engines, but they are very unique engines and really sound and look great.

Replacing bearings in only three years??? I have original Saito FA-30 open rockers 30 years old with original bearings! Been in three airplanes and getting ready for the fourth.(scratch built Robin Hood 25) I bought my Pegasus 240 in 1987 and has been flown for the entire period to the present, on original bearings. I am even flying the Kalt FC-1 an it came out in 1976, original bearings. One of my OS FS-60 open rockers has over 1000 flights on it but yeah I had to replace the bearings finally, not due to corrosion but just too much play! My engines are precious beautiful things to me and I learned early on to take the best care possible. I am so appreciative of the wonderful things available to the hobby today an am willing to work and learn to make them perform and last to the fullest. I have put many hours in to figuring out these radials resulting in hours of enjoyment and I started this thread to help others have fun with them too. -Tom

Air tool oil by itself isn't the best for storing engines - it doesn't "wet-out" well onto the metal surfaces, evaporates relatively quickly (months), and usually doesn't have any corrosion inhibitors. Need to supplement it with something that helps on these three counts - typically ATF (automatic transmission fluid). Since I began using a 50/50 blend of Rislone & air tool oil about five years ago, have never had a bearing, ring or cylinder corrosion issue on some 80 engines in storage.

Interesting point Redball. The brand I get boasts that their airtool oil has multiple corrosion inhibitors. I have heard ATF is quite good. -Tom

hello all radial lovers
Soon I'm back in the air with PT17/UMS 7-35, the engine works fine after repair.
fuselage forward had to take a beating, so I built a box for the fuel tank.
I then got the tank later (shorter hoses to the engine).

boring pictures of corrosion in evo 9-99.
I have been using ATF oil in my engines for over 20 years = no corrosion
I have followed Tom's resept to protect radial engine they worked very well.
I did not change any corrosion ball bearings now that has ATF oil.
ATF oil does not protect against mechanical damage sadly

http://www.rcuniverse.com/forum/atta...mentid=1928226http://www.rcuniverse.com/forum/atta...mentid=1928227http://www.rcuniverse.com/forum/atta...mentid=1928229

Hello Tom
I am glad to hear about your engine success on those bearings, that is remarkable, I do have to admit that I have never really used the after run anti rust oil or anything like it, but I do a lot of flying usually 5 or more cases of fuel on the airplanes and at least 2 or 3 cases of fuel in my Helicopters per summer season, I only just started the after run oil that is the blue blocker that Horizon sells just for the 9-99. after talking to Peter Bergstrom, He says possibly I may not be using enough? that may be true because it seems like it is not getting to the back of the crank case? and my corsair sets level on a shelf because I do not take my planes apart, they stay together , However, the question I have is, are you saying that you are putting the after run oil in after every flight? or just when at the end of the flying day? I do think that your Idea of using the air pump over night would make sense drying out all the moisture, and do you use the same procedure with your other older 4 stroke engines with the air pump? I would like to try some other stuff to put in the engine when I get it back other than the blue blocker what other blend is available and where can I get it? possibly the hardware or auto store? BTW I loved my O.S. 240 Pegasus flew it for 9 years in a Piper Tri- Pacer. sold it {wishing I had it back} but the 320 is by far the best engine I have ever owned. thanks again for the info-Steve.

sorry redball8, linklan2, and Maxam{tom] I posted the last posting without reading the previous post I apologize, sounds like atf and air tool oil is the way to go, thanks for the info. I have the 777 on back order for my Stearman, I will definitely use more care on these engines.

Oh no, I just do the oiling process at the end of the day! That would be awful if I had to do it every flight. I have once flown the 999 8 times in one visit to the field. Believe me the ventilation has been 100% successful. The pegasus flat fours are most likely the finest running model engines on earth with electric motor smoothness.

OK "great on the ventilation" I will start that process, AMEN on the flat fours!!!!!!!

Tom just wondering if you are opening the carb to let the air flow. out? and what brand of air tool oil are you using? Thanks-Steve.

Hi Steve. I use Campbell-Housefield from Wholesale Tool supply and yes the carb is open! Just flew the 'ol corsair 4 more times last night! Lars, Glad to hear you are getting your engines and plane back together! Always enjoy your posts. -Tom

Thanks Tom can`t wait to get my cosair back in the air, do you know if the RCS 150. 5 cyl. The same as the Moki? Just diff. Name? - Steve

Yes Steve it is. -Tom

I have an RCS 150, been trying to sell it to fund the Evolution 260 sitting in my basement now. The RCS is identical to the Moki, made in the same factory, just sold through Troy Built Models instead of other dealers. I've just about decided to keep the RCS rather than give it away.

Picture #3 is the clue... See the bumps in the rust. This is indicative of galvanic corrosion, not simple oxidation type corrosion. So, someplace in this motor we have stainless steel (I'm guessing the round plate behind the circlip) and zinc creating a circuit. Dissimilar metals are notorious for rusting in hours like this.

http://www.engineersedge.com/galvanic_capatability.htm

The zinc could even be the coating on the cap screws or an alloy in some of the aluminum parts.

Couple that with us using full synthetic oils which are almost corrosive on their own and we get, RUST. First action item is to get rid of any zinc. It is usually the easiest to replace with some other metal.

This is by far one of the best theories I've heard on this subject and explains a lot of the problems with corrosion. Next step should be to identify the parts which need to be replaced. If anyone has any idea I think it is worth for all of us to do some research on this. I am definitely willing to do it and replace parts in case ...

That doesn't sound good for the stainless bearings I had installed in my ASP 4.00. It was that, or go with original bearings that rusted also.

Stainless doesn't rust.

Well, as always: it depends. Stainless is no synonym for "rustless". Depending on the alloys you get steel that is more or less prone to rust. With regard to what has been guessed: There may be some alloys in our engines that may result in electrolysis, whether from stainless steel or other parts. As an example: I saw a welded connection of stainless steel tubes with ordinary steel tubes, and this corroded significantly.

No, stainless doesn't rust, at least at the conditions you'll ever see a model engine exposed to. That's why they're called "stainless". It's the chrome that oxidizes and provides a barrier against more iron oxide formation. Sure, martensitic alloys (say 440) aren't as corrosion resistant as austenitic (non-magnetic - 302, 304, 316), but relative to carbon steel they're much, much better. See http://www.sppusa.com/reference/white_paper/wp_ss.pdf.

Redball, the point to focus on is not pure stainless steel (with more or less proneness to corrosion), but on the mixture of components and electrolytic reactions due to different valencies. So the question is, how alloys within the engine may interact. I think this is the point where an experienced chemist should jump in. Edit: Just remembered some personal experience: Putting steel weights onto aluminum wheels in order to balance them will damage these during the next winter season (becoming leaky due to massive corrosion). I found out the hard way after the mechanic did this with my wheels ...

Right - corrosion, not just rust. Btw, I'm a chemical engineer with nearly 40 years in the CPI (chemical process industries). We deal with material-of-construction issues all the time.

Personally, I think stainless bearings are a waste of money. Better to invest in good oil (I also work for an oil company). Carbon steel and aluminum will do just fine in a glow motor (save maybe the plugs)!