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  • Re: Crooked carb diffuser?

    by » 7 months ago


    Thanks for the replies and helpful feedback particularly the reference about LEAF being able to do this type of repair.

    BTW, anyone with experience out there at looking at vibration frequency analysis on the Rotax 912? RPX has a nice video were they indicate that a spike at a 2.43 per frequency (crankshaft RPM) is indicative of poor flow distribution between the front and rear cylinders because of the different lengths of the intake runners. But they also indicate that it should go away at cruise RPM. In their video they say a 1.2 per vibration is due to carb imbalance. I would think that a carb issue would then show as a 1.2 per and not 2.4 per imbalance.

    Anyone had experience (or opinions) on other possible reasons for this 2.43 spike to occur?

    Warning: my analysis was performed with a sensor in the cockpit while flying and not at the engine. There is always the possibility that this vibration is caused by other airframe related factors but I don't think so since the vibration perfectly follows the engine RPM frequency.  

    Best Regards,

    Chris

     

     


  • Re: Crooked carb diffuser?

    by » 7 months ago


    Hi Rotax Wizard,

    I posted my last message before I saw yours.

    We did check the gearbox for proper clutch torque (yes, 912 ULS with clutch). Gearbox "supposedly" overhauled by iRMT Repair Centre 100 hrs ago. Vibration analysis doesn't show vibration at a frequency in line with gearbox issues (2x per RPX). But of course I am not discarding that possibility.  

    Airplane is a new Europa homebuilt that I finished and started flying in March and has 100 hrs now. New rubber mounts installed a couple of months back. This buzz was present from day one.

    Let me reiterate, the vibration is not really that bad. It's more like a buzz that becomes more noticeable over 5000 RPM. For all I know it may be normal for this engine but I am jealous that I don't feel this in a CTLS, RV-12 and  a Tecnam I recently flew in. The frequency analysis (see attached picture) does show a large spike at crankshaft speed which is what is prompting me to investigate. 

     

    Best regards,

    Chris

    31464_2_N11EU 5600 RPM in air.JPG (You do not have access to download this file.)

  • Re: Crooked carb diffuser?

    by » 7 months ago


    No relationship between the vibration and airspeed whatsoever?


  • Re: Crooked carb diffuser?

    by » 7 months ago


    Rotax-Owner wrote:

    Tyler Hathaway, Who did you submit a CSIR through? - RFSC?

    Was this related to your carburetor piston slide post about 7 months ago??

    Yes, that's exactly what is was...

    One of the things I learned in business school is... if you are going to have a Suggestions box/department, you really ought to let people giving the suggestions know that they have been received, if not actually acted upon.  Otherwise, people just stop bothering.


  • Re: Crooked carb diffuser?

    by » 7 months ago


    Thanks for mentioning that LEAF has done this.  I'll be coming up on my 600h overhaul in 130 hours or so... I'll probably send it to them, knowing that they can do that fix.


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