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Rotax 912 Carb SafeSync

in 912 / 914 Technical Questions 12 years ago

  • Re: Rotax 912 Carb SafeSync

    by » 12 years ago

    Hi Kevin,

    OK, but it does not harm anything if it does not interfere with the rest. Anyway, I shall disconnect the electrical wiring.

    See www.lemo-solar.de for some interesting pieces. It is in German but I can help if you wish.
    Select Modellbau and then Zahnrader: art.nr. SRC07.

    I have the upgraded design ready on paper. It is such that it is not in the way of the throttle bowden cable. I will solder the brass gear wheel to the cable adjustment screw. The worm wheel will be connected with the help of an axle to the servo.

    As soon as I have all the needed parts in house I will make a prototype. When I am satisfied I will publish some photos for sharing.

    Jan
      
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  • Re: Rotax 912 Carb SafeSync

    by » 12 years ago

    Hi Kevin,

    Attached is a sketch of the KS Carb Cable Adjuster.

    Please review the conceptual design.

    Jan

    SCAN0037_1024.jpg (You do not have access to download this file.)
      
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  • Re: Rotax 912 Carb SafeSync

    by » 12 years ago

    I like the idea of the worm drive, it looks very neat. Have some slotted holes to allow for adjustment will help with mounting.

    Don't forget that the gear attached to the cable adjuster will move fore and aft. It needs to be wide enough for the worm gear to engage with it over its effective range of travel. It shouldn't need to travel very far, a couple of mm should be sufficient.

    What I would say is that if you intend to add extra weight to the carbs then unless you have an airbox to support them you will be stressing the rubber manifold gaskets and they may split.

    Kevin
      
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  • Re: Rotax 912 Carb SafeSync

    by » 12 years ago

    I'm not trying to be a kill joy, but I have a few questions.

    What keeps the cable from twisting? Not all cables fit smoothly in the adjuster, not to mention corrosion.
    How or when do you put a lock nut on the other side of the Bowden cable adjuster?
    How do you later secure the throttle cable from coming in and out of the adjuster when the throttle is used after this is all done?
    Does this mechanism allow full travel on the adjuster screw fore and aft?
    I see you already have a hot water coolant carb ice setup on the carb and with the addition of this setup, weight on the rubber carb socket and vibration may lead to premature rubber socket failure?
    How about interference with the throttle and choke cable? (Choke tubing looks to be 90 degrees from normal alignment)
    There are different size Bowden cable adjusters on different planes can this be used?
    How much torque does this have to screw in and out, some adjuster nuts and adjuster threads make them a little hard to turn without a small wrench?

    Just some items I would like to know before an install.
    My wife or the owner is usually my cockpit manager, safety person and throttle jockey for carb syncs.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Rotax 912 Carb SafeSync

    by » 12 years ago

    Kevin and Roger,

    Thanks for the reviews.

    Kevin:

    The gear wheels has a thickness of 5 mm each so that travel can not be an issue. Anyway, there are slotted holes for initial set up.
    Otherwise 2 gear wheels have to be installed.

    Roger:

    Re: twisting cable: this can also happen when using the manual adjustment. Lubricate when needed.

    Re: locknut: after removal of the drive unit the procedure is as usual

    Re: travel: see above

    Re: only the additional Alu clip plus 1 or 2 brass gears wheels are left in place: very small weight

    Re: interfere choke cable: drive unit is placed sideways and below the bow of the throttle cable housing: so no interference is expected

    Re: different size Bowden cable: then different sizes of gear wheels and brackets are necessary

    Re: torque needed: Kevin has specified some torque values. If adjuster nuts and threads have to much friction you have to reduce this

    Groeten Jan
      
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