Exhaust keeps shaking loose

[Craig Spence]

Hi all, on my recent trip to the field I keep't getting dead sticks on my first few flight's, after checking the engine I noticed that the exhaust was loose. This had happened before on my first few trips to the field, one screw had came out completely on one flight and the exhaust was hanging by one screw. After that I used screw lock but it hasent solved the problem because it's happend again.

On inspection this time the bit of cloth (material between the exhaust and engine has all rubbed away, does anyone know what this is called nad where you get spares. Do I need to replace it?.

 

Also the engine has been running fine every time ive been down the field and on my last trip I had 17 minit's out of it, however I was also getting alot of dead sticks on idle and no matter the adjustments made the problem persisted, this is a problem for me at the moment as im practising low approaches for landing and it keeps going deadstick and im having to run fields to retrieve it.

 

The engine is a sc46 and runs on propower 10%, would running it on a high percent of nitro (say 15%) break the engine in better.

 

Any info, help or suggestions appreciated.

 

Many thanks, Craig.

 

[Tim Mackey]

Simple thin gasket made of waxed paper, or better still proper gasket material if you can find some.

Use a drop of threadlock on the fixing bolts and make sure they are REALLY clean ( and the "holes" too before applying.

Stick to 10% nitro - thats PLENTY

[Dusty]

Timbo sumed it up! However you can get vibrating reducing engine mounts that might reduce the problem, I had it happen a million times with mufflers falling off etc! If you get some new screw for the muffler that you can do up with a flathead screw driver then you can do them up abit tighter, the supplied screws on SC engines I have replaced as they are soft on the alley key hexagonal head and wear away quickley!

 

Pre flight checks check the screws are tight along with prop nut etc

[Craig Spence]

Thanks fellas,

 

any tip's on the engine being out of tune or is it just because it's still a bit stiff.

 

Cheers.

 

[Brian Cooper]

It's a sad fact of life, but if you use the gasket, the exhaust WILL fall off. 

Don't ask me why it happens --- it just does.

 

The way to keep the exhaust attached to the engine is to use a small amount of 5 minute epoxy and smear it on the silencer (where it mates with the engine) before bolting it on.

The epoxy acts as a much better gasket and seals the joint properly.  But the real bonus is the silencer doesn't fall off.

 

Don't worry... the silencer can still be removed easily when required.

 

B.C.

[Bruce Richards]

I agree with you Brian. A small amount of epoxy works well. I can't realy comment on whether your engine is out of tune without seeing it run. Do you do a nose up test to check it is not too lean? Does it go dead stick when wide open, when throttling up, at tick over? When you have the exhaust fixed then tune the engine. 

[Brian Parker]

Balance the prop to reduce vibration. Use proper gasket material and new spring washers on the exhaust bolts/screws. Run engine to normal temperature, allow to cool then re-check tightness of bolts. The engine will be off tune until the exhaust is seated.

[flytilbroke]

Sort the exhaust problem first. Then get the engine running correctly at full power, the low rev cutout indicates the low mix needs some adjustment, but only after the first two issues are resolved.

 

I have never had exhausts loosen when using proper gasket material along with the threadlock on clean threading of bolts and engine. Epoxy can work too, but allow time for it to set after tightning up the bolts, before starting the engine. I do prefer a proper Gasket.

 

Epoxy will soften with heat when you wish to remove the exhaust later

[Craig Spence]

Thanks for the feedback everyone, Im going to use 5 minit epoxy now and thread lock. However I dont think ill be able to clean the inner threads as screw lock has been used on them before.

 

Well see how it goes and then ill retune the engine.

 

Cheers all.

[Ed Darter]

I used to use the gaskets but got fed up with hem still leaking even when I tightened the bolts up as much as possible - I use the 5 minute epoxy method now and have never had a leaky exhaust manifold since - do it the day before you plan to fly the model for the first time though to give it a chance to go off properly.

As said by others - sounds as though you have a vibration causing the bolts to come loose, check the prop is balanced and use a good spinner ! - lots or ARTF's - especially cheap ones have spinners that are out of balance and appear to be made of chocolate. If only they were they would be slightly more useful as they wuld be a tasty snack down the field !

Ed

[ken anderson.]

hello craig---i'll add my six pence worth-----i don't bother with the gasket either--what i use is clear silicone/the type used to construct fish tank's etc---make sure every thing is clean and dry and apply to the engine and bolt on your silencer--i also put a blob of it over the nut's so they can't undo them'selves--balance your prop--make sure the exhaust is well supported and bingo-no more loose silencer's---i've seen people spend a long time looking for them in the grass at our field.....

 

 

                                 ken anderson......................

 

 

     ps--the silicone is easy to get off when you want to remove your silencer.....