ORIGINAL: i3dm
ORIGINAL: frema
If you blow the compressor wheel in the engine with pressed air ,and you dont feel vibration , but during running of the engine ,there is vibration, then its the preload.
if the preload is not strong enough ,or the washers are not exact in center of the bearing , then you can have vibration.
you have to know that ,during the run ,the shaft gets longer, because of the temp.
If you dont have the right strenght of washer then there is a bass sound in the engine at full speed.
you also feel vibration ,and the compressor or the turbine can rub ,because of the vibration.
then you think it is unbalance , but it is the preload.
i serviced a simjet 1200 ,and this engine had the same problem.
it was delivered with a preload of 4kg .
i changed it to 6kg , thats a lot more , but the engine still running ,and all the problems are over.
The engine is also more powerfull and lower egt ,because the shaft slides no more ,so with fullpower the compressor keeps the same gap between the blades and the cover.
thats very important for the engine.
Regards,
Martin.
Soudns like what we are witnessing. do you suggest spinning the engine with compressed air to check ? if so, to what RPM ?
Yes ,thats about 10.000 rpm.
when you do that , lay two fingers at the backsite of the engine ,and spin it , spin it slowely till you reach 10.000rpm .
there must be a point that you feel vibration .
do the same thing at the compressor site ,and then you know if its the compressor or the turbine.
Regards,
Martin.