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Cleaning bearings in IPA


Mike Watters
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I'm laying up a OS46AX for storage, while I run in a new OS46AX for a twin project.

 

I had a thought for long term engine storage, could you give the engine a good dose of isopropyl alcohol (IPA) in the carb, swill round the bearings and drain out the excess. Then give the engine a good oil with after run oil? 

 

Previously for long term storage I'd drain the fuel tank, run the engine dry and when I'm home give the engine a good oil with Model Technics After run oil. 

 

I've heard of others after the end of season flying, fill the tank with zero nitro fuel, run the engine for a minute to clear it out, and after run oil it. 

 

Has anyone any thoughts on the IPA idea? 

 

Thanks Mike. 

 

 

 

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IPA is alcohol and a solvent too boot, why would you want to use it, are you a printer by trade? FWIW it tends to act like methanol, ie absorb water.

After the last flight, run the engine at full throttle for at least 15 seconds, pull off the fuel pipe to stop it and whilst hot pour in your after run oil, auto transmission fluid is good for this purpose btw. Some folks drain remnants of fuel out of the carb. Flick the engine over multiple times to get the oil round it.

Store the model nose up with the throttle closed and if the bearings were good before the last flight they should be good when you reactivate it.

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Hi Mike . IPA certainly cleans old castor off ok , but is it hygroscopic like Methanol ? I'm not sure . It's the methanol that mainly causes the rust on bearings when engines are in storage as it absorbs moisture from the air . The acids from burnt fuel/ nitromethane just add to the problem. An old friend always washed his engines in IPA then dried and oiled them when putting them into storage. He swore by it but he only ever used straight fuel.

PS . Have just done a Google search and IPA is apparently even more hygroscopic than Methanol. 

I have been using air tool oil as an after run oil for some years now. It does keep engine internals in good order provided that engine is run dry when hot then oiled and given a good few clicks to splash it around. The air tool oil is designed to prevent damage from water as air tools are prone to having water b?own through them from the compressed air if the water trap is not emptied regularly.

Edited by Engine Doctor
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John, water, iron, atmospheric oxygen, rust. It lasts long enough to start the pitting process, unless the lump is hot enough to satisfy your surely, ie it evaporates. 

Part burnt nitromethane, water, combines to nitric acid, result, pitted iron.

A knackered bearing only needs surface damage to earn the name. 


I’ve always favored, run it hot, disconnect from fuel to stop it, then take the motor to storage by removing the plug, and turn it over in an oil/ paraffin bath.  (Tupperware box).Put the lid on the it and forget it. 
Resurrection, shake and drain, turn it over on a starter. Refit plug, and off you go.

Purists clean the outside as well. 

There are experts at this game who will change the bearing after a long storage.

 

Edited by Don Fry
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I agree with water, oxygen, and nitric acid being corrosive. Is the "it" you refer to alcohol (methanol or IPA)? Surely that doesn't last long enough absorb water and start the pitting process. Most light alcohols evaporate in minutes at room temperature if exposed to air. You have got me worried, because I have used exactly the same method as the Mike Watters asked about: IPA followed by after-engine oil. As far as I could see, the IPA acted as a superb solvent to wash away all the other organic compounds, and the remnant IPA evaporated off in minutes. Then I applied light engine oil.

 

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As a user of air tool oil, in air tools as well as engines I recommend it. Water vapour from the air condenses in the tank and collects at the bottom so has to be drained now and then. However some does go down the line and larger air systems have a built in dryer and automatic oiler.             

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John, you or I may be right. That is not a funny statement, but an admission this is a complex situation. Despite having a degree in chemistry I don’t know what the evaporation rate is for IPA in solution with gunk, old oil, fuel residues. Careful experiments can give an answer, but the answer is not to be found in looking up relative boiling points.

A compromise perhaps is to warm the motor, hand hot in an oven, at least you can be sure evaporation is higher, bit then so is corrosion, and the science of corrosion is frankly weird. 
I stick to materials which are hydrophobic.

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  Don, No doubt it is a right minefield. A few years ago I had need to discharge a fire extinguisher in my workshop [ not models ] when some heavy duty cable's shorted, overloaded and set their coverings on fire. A dry powder did the job but the corrosion that set in on items in parts of the workshop nowhere near fire was a right pain.

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If i am putting an engine away for long term storage i first give it a wash. Mounted in the test stand a good blast with the hose usually does the job nicely as long as i dont blast water down the carb. 

 

Once that it out of the way i fire it up on a small prop. Why a small prop? The light load means you can run a really lean mix and this limits the amount of fuel left in the engine. The high rpm also gets the engine nice and toasty to both dry it after its shower, and evaporate any residuals from the crankcase after i am done. 

 

Anyway once its warmed up i tune all the needles to suit the bench (to erase the settings used on the last model) and give it a long blast at high rpm. At least 2 minutes with the throttle used to reduce the rpm by about 500 from flat out. Once that is done, pinch off the fuel and its all over. 

 

Give the engine a wipe off with a cloth, turn it to TDC (important of 4 strokes) and pop it in a plastic bag. It then sit in a box under the bed with all its mates. None of my engines see any after run, and the ones brought back into service after many years have not shown any problems when stored in this way. 

 

If you do want to fill the engine with oil, i recommend you find some klotz or ML70. You need an oil that will wash away with new fuel next time you run the engine. ANd dont be shy either. a few drops of oil will not help much, really fill it up and makes sure its sloshed all around. 

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