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Thread: Marina 4 speed gearbox gearchange extension.

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  1. #11 Re: Marina 4 speed gearbox gearchange extension. 
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    Both halves of the selector shaft needs to be in line as it needs to turn, having one on top of the other will force them to try to turn in a circle around each other.
    I am going to try a 15mm universal joint and tilt the new frame upwards at the same point as the u/j. I will have about 20mm to work with between it catching on the prop and the top of the tunnel.
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  2. #12 Re: Marina 4 speed gearbox gearchange extension. 
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    No problem with the sliding joint of the prop shaft at the front, mine's been like that since I built it as with less bouncing around it doesn't wear as much. That will give you a bit more clearance.
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  3. #13 Re: Marina 4 speed gearbox gearchange extension. 
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    Hmmm, not sure this is going to work.
    Waiting for a universal joint from Banggood, think it's coming from China as ordered it last week.
    Thinking about this, by using this universal joint to raise the selector will be ok for the side to side movement between 1st/2nd and 3rd/4th but not sure it will work well for forward and back movement, they are designed for turning and not push and pull. Have to wait and see.
    Adrian, how are you getting on with yours?
    Martin.
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  4. #14 Re: Marina 4 speed gearbox gearchange extension. 
    frequent forum contributor Club Member listerjp2's Avatar
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    Will be going to my mates week after next.

    Have cut selector and gearbox and have dressed both so all parts are ready for fixing.

    Interested in the work your doing and had the same idea as you with regards reversing the drive shaft.

    Decided that's the way I will be going.

    Adrian
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  5. #15 Re: Marina 4 speed gearbox gearchange extension. 
    frequent forum contributor Club Member stevejgreen's Avatar
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    Quote Originally Posted by meverett View Post
    Hmmm, not sure this is going to work.
    Waiting for a universal joint from Banggood, think it's coming from China as ordered it last week.
    Thinking about this, by using this universal joint to raise the selector will be ok for the side to side movement between 1st/2nd and 3rd/4th but not sure it will work well for forward and back movement, they are designed for turning and not push and pull. Have to wait and see.
    Adrian, how are you getting on with yours?
    Martin.
    I thought that it might be practical to machine a complete new shaft but it appears to be difficult.
    Be aware that under load, the standard propshaft, though being reversible, deflects a great deal, your calculations must co sides the maximum vertical bump stop.

    so far as UJ's are concerned, two, rotated 90 apart, would give the best 'feel' theoretically, one may be oK provided it is centred about the rotation of th selector shaft, otherwise unacceptable forces might be indipuced.

    I am watching with interest, real possibilities if a design kit can be produced and sold, not just for Marina based cars but Triumph too.
    MOC member since 05/97
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    The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

    Loads of Marlin Reference can be found documents here or there.
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  6. #16 Re: Marina 4 speed gearbox gearchange extension. 
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    To have machined a new longer shaft would still be straight and the selector would still catch on the prop.
    This is where I am so far, the 3 blue lines are 1st/3rd, neutral and 2nd/4th and where the u/j will be located on the shaft. I need to keep the original shaft from the gearbox level so I will cut the alu frame at this point and bend up slightly to the selector giving the clearance from the prop.

    IMG_4055.JPG

    If this doesn't work I will be on the lookout for another rear extension.
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  7. #17 Re: Marina 4 speed gearbox gearchange extension. 
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    Thanks Adrian, keep us posted with your development.
    Martin.
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  8. #18 Re: Marina 4 speed gearbox gearchange extension. 
    frequent forum contributor Club Member b_caswell's Avatar
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    A friend of mine ran a rear engine and Hewland box race car and that used what we called a helicopter joint.

    When I googled it I came up with this a expensive though

    http://www.demon-tweeks.co.uk/motors...iversal-joints
    Ben Caswell probably not the last word on anything here!!
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  9. #19 Re: Marina 4 speed gearbox gearchange extension. 
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    Ouch, that is expensive. I have ordered a UJ from Banggood for 9, may take a while to get here though and hopefully will do the job.
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  10. #20 Re: Marina 4 speed gearbox gearchange extension. 
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    Try Car Builder Solutions, under budget gear change U J https://www.carbuildersolutions.com/...sal-joint-75mm
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