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Split happens

  • Johan Wessels
    Johan Wessels
    Johan Wessels on

    split.jpg
    I note with interest the article in the Caravan Clinic pages of June 2017 on the subject of “split flywheel”. I would like to add my tuppence-worth to this subject.

    Considering all the engineering research done to improve the performance of high torque diesel engines, I do believe that we should be aware of whatever modifications we make when replacing these serviceable components, take considerable care, and also understand the possible consequences.

    As stated, the dual mass flywheel is fabricated to insulate the gearbox from torsional and transient vibrations produced by the high torque diesel engines.

    This split flywheel consists of primary and secondary flywheels, with the drive between the two transferred by a torsional damper consisting of coil springs which are generally located in the inside diameter of the primary flywheel.

    The secondary flywheel is generally comprised of two parts: The outer section which provides the friction surface for the clutch drive plate, and an inner drive plate which transfers the drive from the primary flywheel via the coil springs to the outer flywheel.

    Under high torque loading, the secondary flywheel can rotate in either direction as much as 70 degrees in relation to the primary flywheel.

    It is this compensation within the two flywheels that firstly protects the gearbox from sudden and harsh torque forces, and secondly absorbs engine vibration being transferred into the gearbox.

    What surprises me is why the flywheel face was worn to that extent. Generally, the clutch plate would wear long before a flywheel face. At only 156 000km, I am very surprised that Andrew Turpin experienced this with his Mazda BT-50. It would be interesting to hear what Mazda’s technical department has to say about this.

    I have never had to replace a flywheel due to wear, but have certainly replaced the clutch plate. Of course, that’s not to say that a flywheel can’t wear.

    I would be reluctant to replace the duel mass flywheel on my Disco TD5 with a conventional one, but I do understand that the cost of some of the manufacturer’s original equipment can be excessive. The mere fact that the replacement conventional flywheel is most likely to be a “pirate” part, and therefore a similar “pirate” duel mass flywheel could also be used at a considerably more affordable price, would make it preferable to using a conventional type, for the reasons stated above.

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