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    » Proposals for Model aircraft flying ( CAA registration) April 2019
    The effects of Nitromethene ? Empty2019-05-08, 17:49 by Gary M Jones

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    The effects of Nitromethene ? Empty2019-02-10, 16:31 by melfyn

    Saturday 7/7/18

    2018-07-07, 21:07 by Gary M Jones

    I was at the field today between 14:00 & 15:00 all on my own , good flying too. There is a dead sheep along the fence line towards the gate from the pits, I saw the farmer so reported this to her. I hope no one had plans for a BBQ Smile .

    Farmer …

    Comments: 1


    The effects of Nitromethene ?

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    The effects of Nitromethene ? Empty The effects of Nitromethene ?

    Post by melfyn on 2009-09-09, 21:55

    A few weeks ago I brought my new creation the Sonerai to the field for its first outing. It's maiden flight never took place as the engine refused to run. The engine in question is an ASP .32 which previously powerd my Kerfuffle for a brief spell but was replaced when it became troublesome. Anyhow the carb was stripped and cleaned and the engine fitted to the Sonerai. Following the disappointing first outing of it I have now replaced the ASP with an Enya SS .25.

    Once I had removed the ASP from the airframe and removed the exauhst I discovered a reddish brown deposit on the outlet manifold and the inlet of the silencer. I then decided to remove the crankcase backplate to investigate further. Upon its removal I discoverd tom my horror that the crankshaft couterbalance and crankpin were badly rusted. The rest of the engine was then dissmantled to discover that both bearings are shot and the gudgeon pin is also in need of replacement.

    Here are some photos of the rust damaged parts:
    [img]The effects of Nitromethene ? ASP32crank2[/img]

    The effects of Nitromethene ? ASP32crank1

    The effects of Nitromethene ? ASP32rearbearing
    The effects of Nitromethene ? ASP32crank

    Pretty bad as you can see. I now have a question for any of you engine Gurus out there. How should I go about removing the old and re fitting the new bearings? Any help on this would be much appreciated.

    I have owned many engines in my time and whilst I have encounterd some minor pitting of steel and iorn parts in my engines in the past I have never found anything near as bad as this. It makes me wonder if the rust was in there soon after manufacture as I bought it some time ago and it was stored in unused condition for about two years before being used for the first time.
    melfyn
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    The effects of Nitromethene ? Empty Bearing removal

    Post by Guest on 2009-09-09, 22:41

    Hi Mel, Bearing removal is quiet straightforward once you have done a few. Strip the engine down so that you just have the crankcase and bearings. You now need to heat the crankcase. The case having a higher coeficiant of expansion than the steel the bearings are made of will expand more and allow the bearings to be removed. Once hot a sharp rap on a block of wood and the rear bearing will come out. You then need to use a drift to push out the front bearing. I use a piece of ally so as not to damoge the crankcase. I use a paint stripping heat gun as a heat source but another method is literaly to cook for 10min at gas mark4 in the oven Exclamation

    Replacement is done by again heating the crankcase untill the bearings just drop in useing the crank to ensure they are linned up correctly and bottomed in their housings..

    The only way to slow down this rusting process is to do as we do with our helicopter engines and that is to
    1. Run the engine dry at the end of a flying session by removing the fuel line.
    2.Turn the engine over with the glow connected to remove the last traces of fuel.
    3.Rotate the piston so that it is at TDC and blocking the transfer ports
    4.Block the exhaust.

    This stops air and moisture from entering the engine and reacting with the exhaust residue and methanol left in the engine.

    You note that I said slow down the rusting process not stop it. The only way to stop it is to flood the engine with after run oil and wrap it in an air tight bag.

    John Haytree an acknowleged engine guru has said to me on more than one occasion that we have to treat bearings in IC engines as consumables Question Question

    If you have any trouble I am only to happy to do it for you if you fancy a trip to my workshop Very Happy .

    DaveS

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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by Andy Sayle on 2009-09-10, 09:11

    The best way to stop the rust completely, is to swap the engine for a motor Twisted Evil

    Seriously though, corrosion of steel/iron will only occur when two things are present and in contact with the surface of the material. Water, and Oxygen. Exclude one or both of them, and you will not get any rust forming. The thing is, that is much easier said than done Smile

    Slathering components in (after-run) oil will go a long way to excluding moisture, but what can happen then is you get little pockets of moisture trapped under the oil film, and this can quite often accelerate corrosion at the oil/water interface. It's quite a well documented phenomenen in full size aerospace circles, I'll try and dig out some white papers on it for you to read through if you like?

    All of Dave's advice is bang on the money too. If it were me, I would treat whole engines as consumables, and beat the life out of them, expecting them to die sooner or later, be it from corrosion, crash damage or over use!

    Cheers
    Andy

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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by PDQ on 2009-09-10, 10:58

    Perhaps I couls add my 4 penyworth here
    Engine Corrosion Damage

    Magic Words needed here 'Lyophilic' (likes water) and 'Lyophobic' (hates water)
    Steel parts are usually prone to rusting. In the case of hardened steel, as used in model engines, this effect can be severe.

    WD40 contains a chemical molecule that is Phobic at one end and Philic at the other. It interposes itself between any water and metal. It is a spin off from chemicals used to mothball military equipment. It is another reason why modern cars seem so corrosion resistant.

    Methanol and Castor oil are both Lyophilic.
    Not a problem because moisture (H2O) is produced in combustion anyway. However, the combustion does produce a potentially acid residue which is corrosive to hardened steel parts. The engine should be rinsing out with fresh Nitro free fuel containing a corrosion inhibiting oil. PAW recommend leaving the piston down with the exhaust port open to allow any residue to disperse when the engine is stored.

    Nitromethane
    Another name for Nitro Methane is Nitrated Methanol, it is made by reacting Nitric Acid with Methanol.
    As soon as it burns in an engine it releases large amounts of Oxygen. It also releases other chemicals and in particular, Nitric Acid.
    Nitro allows extra fuel to be admitted. The extra oxygen from the Nitro supplements the limited fresh air supply that the engine would normally breath in. Hence the fuel / air ratio can be increased and the engine will then produce much more power.

    Unfortunately
    the residues from burnt Nitro leave a very corrosive acid mixture behind in the engine. If this is not removed entirely, the hardened steel parts of the engine will rot away very quickly. This is accelerated in warm damp conditions.

    There are after run oils available in the model trade.
    e.g Model Technics
    "After-Run Oil should be put into the engine after each session of use to give additional corrosion protection. It also makes a superb general purpose lubricating oil and is supplied in a spouted container."
    Price £3.05
    PDQ
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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by Guest on 2009-09-10, 11:18

    or use a fuel with only synthetic oil. bin that southern modelcrap and get some bekra What a Face

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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by PDQ on 2009-09-10, 13:54

    Leigh
    You scored, but entirely missed the point.
    Nitro will still rot it to bits no matter what lubricant you use.
    How do you ensure your engines last?
    PQ
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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by Andy Sayle on 2009-09-10, 15:32

    I have a simple method of making sure my Engines last. I don't buy any, and use electric motors, as God/Buddha/Flying Spaghetti Monster * intended Twisted Evil

    Andy

    * delete as appropriate or insert deity of choice here.....

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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by Guest on 2009-09-10, 15:34

    i use them paul, like dave said an engine is a consumable, every motorsport going looks at an engine that way, they only run for so many hours and there done. or at least past their best.

    also modern fuels with synthetic oils naturally inhibit corrosion as the oils are lyo(hydro)phobic. so whilst concise my answer didnt miss the point Cool

    on the other hand.
    if im storing an engine, strip it clean it with petrol and apply plenty of wd40 then into a sealed bag. re assemble it when it is put back into use with new seals o rings and gaskets.

    if the motor is of no real value or pedigree then chuck em in the bin cant go collecting paperweights forever, we aeromodelers do seem to have an afinity for holding on to clapped out old motors which barely run and cut constantly.

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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by melfyn on 2009-09-10, 21:19

    Not sure what's happened to the photos they were there when I did the post yesterday.
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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by Andy Sayle on 2009-09-11, 08:48

    Sorted Mel, No idea what happened, but I'll say I mended it take all the credit Wink

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    The effects of Nitromethene ? Empty Re: The effects of Nitromethene ?

    Post by Sam Thomas on 2009-10-06, 16:20

    With the glow engines on cars we have 'after run oil' that stops corrosion from happening!
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