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  • Constant Mesh Gearbox - Discussion

    Kaustubh Katdare

    Kaustubh Katdare

    @thebigk
    Updated: Oct 27, 2024
    Views: 1.7K
    I'm no automobile or mechanical engineer. Can someone explain the technicalities of 'constant mesh' gearbox - a commonly used term in Automobile engine specifications? Where is it used and what are its advantages?

    I'd also like to know what are the other alternatives to constant mesh gearbox?
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  • ISHAN TOPRE

    Member • May 2, 2011

    Good question Biggie. See, The work of transmission is to connect the torque generated by engines to the wheels. It is done through a clutch.

    In constant mesh gear box, the gears are fixed to their positions. They are meshed. It is a type of manual transmission. It is this gear box that we use in todays automobiles, right? Synchros are absent here.

    Another type is a sliding gear type gear box. This one is not used now a days. here only the cluster gear and driving gear rotate and nothing else.

    Have you ever seen a car in a garage? If you rotate one wheel then the other rotates in opposite direction. Just try to imagine. See this image.

    It shows a simple constant mesh gear box though from it you will not be able to understand its simulation. I would suggest that you try to analyze how the power is transmitted through main shaft to the wheels through clutch and gear system. We use various gear ratios to control the vehicle speed.

    Still unable to understand? Ask me those precise questions. They are always welcome. 😀

    [​IMG]

    Image source: #-Link-Snipped-#
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  • Kaustubh Katdare

    Administrator • May 2, 2011

    Okay, that's fair amount of information for me to visualize. Any more information on why this type was adopted and what are the demerits?
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  • ISHAN TOPRE

    Member • May 2, 2011

    LOL I think everything has gone above your head. Actually I am supposed to start these type of threads. I will do it as soon as I find time (Which is hard nowadays).

    OK so let me tell you the merits of constant mesh. Earlier a crash box(Sliding box) was used. Now constant mesh is used.

    1. The clutch used in constant mesh is having a smaller diameter than the gear it controls. So we can have a smooth and easy engagement and disengagement.

    2.By using a constant mesh, we assign the gear box with only responsibility of power transmission. In sliding type the same gear box had also to look after sliding engagement that is the work of clutch. In constant type, we use a clutch specially designed for the purpose.

    3. Constant mesh uses helical gears which can carry more torque than ordinary gear of same size. It is also because these gears are easier and quite in its operation, that is why we use them.

    4. Howz zat? :razz:

    One more, I think that sliding type is mostly used for heavier vehicles(This point I do not know for sure) But I have heard this.
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  • ISHAN TOPRE

    Member • May 3, 2011

    OK everyone, just stumbled across this video. Check this out. 😀

    [video=youtube;P8YMh8TQ1gg]https://www.youtube.com/watch?v=P8YMh8TQ1gg[/video]
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  • ISHAN TOPRE

    Member • May 6, 2011

    Ok I am back in this discussion. I have got more information to tell now. Both synchro mesh and constant mesh gear box are used in today's automobiles. A synchro mesh is just used in heavy vehicles like trucks. 😀

    One more thing. In a synchromesh we used a conical plate which synchronises with gear. That is why it is called a synchromesh. 😀

    I will be back with more information from time to time. I will keep updating this forum. 😀
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  • ISHAN TOPRE

    Member • May 10, 2011

    The transmission gear box provided/recommended by Mahindra alpha for SAE baja is a constant mesh type. 😀
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  • Shankalp Mohanty

    Member • Sep 9, 2011

    Issue
    The transmission gear box provided/recommended by Mahindra alpha for SAE baja is a constant mesh type. 😀
    can anyone tell me
    even if constant mesh gearbox is used in baja india , why dont we face the problem of double declutching ?
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  • Kedar Malwadkar

    Member • Jul 22, 2012

    Issue
    The transmission gear box provided/recommended by Mahindra alpha for SAE baja is a constant mesh type. 😀
    Why there is no problem of double-declutching?
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  • zaveri

    Member • Jul 22, 2012

    hey issue

    what kind of gear boxes are used in two wheelers ? constant or synchro ?

    nowadays different motorcycles have different gear-shift patterns . do the mechansim of the gear boxes vary along with the shift patterns ?
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  • white_hat

    Member • Jul 22, 2012

    zaveri
    hey issue

    what kind of gear boxes are used in two wheelers ? constant or synchro ?

    nowadays different motorcycles have different gear-shift patterns . do the mechansim of the gear boxes vary along with the shift patterns ?
    To my knowledge two wheelers use synchrnomesh gearbox.
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  • white_hat

    Member • Jul 22, 2012

    Shankalp Mohanty
    can anyone tell me
    even if constant mesh gearbox is used in baja india , why dont we face the problem of double declutching ?
    Double-declutching is carried out by the driver to synchronize the speeds of the mating gears so that they can mesh without any jerking.In a constant mesh gearbox all the gears are meshed together already so no need of double declutching.
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  • Ifthikar Mohamed S

    Member • Jun 13, 2016

    zaveri
    hey issue

    what kind of gear boxes are used in two wheelers ? constant or synchro ?

    nowadays different motorcycles have different gear-shift patterns . do the mechansim of the gear boxes vary along with the shift patterns ?
    Hi,

    Two wheelers only have constant mesh gearbox.

    I hope there won't be any change in mechanism due to shift pattern!
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