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  1. #1
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    7151x driveshafts stupid design ?

    I was ''pleasantly'' surprised when I got the 7151x driveshafts and realize that I must take apart whole vehicle including the diffs in order to install them.
    Why can`t they be made like center driveshaft (7250r) with bolt-on drivecup?
    It would then require removing just a few screws to install them.

  2. #2
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    why is it a stupid design? due to the cups, it wouldnt be able to have removeable youkes, and still have the dogbones

    look at other vehicles that use dogbones, their cups are part of the diff, not a piece you add on later

  3. #3
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    Stock drive-shafts are mounted this way, aren't they? `....Can`t see the reason why steel-cups can`t be.... .
    I`m just presuming that you can replace the drive-cup with the bolt-on cup from the center drive-shaft ....

  4. #4
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    Quote Originally Posted by jimbo74 View Post
    why is it a stupid design? due to the cups, it wouldnt be able to have removeable youkes, and still have the dogbones

    look at other vehicles that use dogbones, their cups are part of the diff, not a piece you add on later
    Companies still make shafts that have removable yokes, they just use a long screw pin like the stock plastic shafts use or a set screw on each side. MIP makes their shafts this way.
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  5. #5
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    mips are much different, they are a completely different thing, that doesnt use cups/dogbones.... they actually use a joint

  6. #6
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    Quote Originally Posted by jimbo74 View Post
    mips are much different, they are a completely different thing, that doesnt use cups/dogbones.... they actually use a joint
    Yes but, they are mounted on the axle with a pin, same as cups on center-shaft.

    Somebody that owns both should check it......

    I`m just saying that Traxxas could make drive-shafts that can be installed without taking the whole car apart




  7. #7
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    Maybe it needs more support because of movement of the arms. Different loads at different angles. The 7250r is set doesn't move up and down

  8. #8
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    exactly, the problem with those is they would go halfway to the axle, not allowing movement of the suspension travel....

  9. #9
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    I agree with mtc777 traxxas should redesign them, like the CVD's for the big erevo, they need just a pin.

  10. #10
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    Quote Originally Posted by jimbo74 View Post
    mips are much different, they are a completely different thing, that doesnt use cups/dogbones.... they actually use a joint
    Not all of them...MIP has a lot of CVDs, with the dogbone style end on the diff.

    Last edited by airmaxx23; 10-22-2012 at 03:52 PM.
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  11. #11
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    Quote Originally Posted by airmaxx23 View Post
    Not all of them...MIP has a lot of CVDs, with the dogbone style end on the diff.

    i am not saying that they dont make them, but that on the mini revo, a huge cup liek that, would extend halfway too the wheel, and not allow the suspension to move without a rediculous amount of binding,

  12. #12
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    Bolting on another piece to the existing shaft is going to do three things:
    1) put the geometry of the axle way out of whack
    2) add a ton of stress to the differential
    3) allow a lot of slop or play in the axle

    The engineers at Traxxas know what they are doing... at least in this instance.
    Whatever it is I just typed... could be wrong.

  13. #13
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    Quote Originally Posted by jimbo74 View Post
    i am not saying that they dont make them, but that on the mini revo, a huge cup liek that, would extend halfway too the wheel, and not allow the suspension to move without a rediculous amount of binding,
    Those cups are really long to accommodate for the long travel in the Rustler's rear suspension, they wouldn't need to be quite that long for the MERV. I like what Traxxss did even though I don't use them.

    Quote Originally Posted by Jimmie Neutron View Post
    Bolting on another piece to the existing shaft is going to do three things.
    1) put the geometry of the axle way out of whack
    2) add a ton of stress to the differential
    3) allow a lot of slop or play in the axle

    The engineers at Traxxas know what they are doing... at least in this instance.

    I'm Airmaxx23 and I support this message...
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  14. #14
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    Is it the design you think is flawed or are you simply upset it's not as easy to install?

    What benefits would there be with the grub screwed on vs the TRX option? Seems the only issue pointed out is the diff need be taken apart, so what. That's not a design flaw but a lazy user overwhelmed by a 30min install, maybe a RadioShack RC is what ur after. Tongue in cheek. Look at it as an opportunity to get more familiar with your MERV and shim up the diffs

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    Quote Originally Posted by Assassin View Post
    Is it the design you think is flawed or are you simply upset it's not as easy to install?

    What benefits would there be with the grub screwed on vs the TRX option? Seems the only issue pointed out is the diff need be taken apart, so what. That's not a design flaw but a lazy user overwhelmed by a 30min install, maybe a RadioShack RC is what ur after. Tongue in cheek. Look at it as an opportunity to get more familiar with your MERV and shim up the diffs
    Yes the only issue pointed out is the diff need to be taken apart.... I just didn`t see (and still don`t, tbh.) the point...
    I`m not lazy I just hate useless work, beside that I had to take it apart due to broken bulkhead anyway.....

    And RadioShack RC is not for me, that`s for sure, I have been into models probably before you were born .....

  16. #16
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    The content of this post has been remvoed for multiple rule violatings

    Dadx2mj
    Last edited by Dadx2mj; 10-24-2012 at 11:39 AM.

  17. #17
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    some people feel that they are better than others, and like to talk smack when they have no idea what is happening....

    those people are good to have around for my entertainment purposes

  18. #18
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    The dogbone style is really old tech, way before the u-joint(usually 4 points of articulation) or CV joint( 5 or more points of articulation).

  19. #19
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    Quote Originally Posted by RCinSC View Post
    The dogbone style is really old tech, way before the u-joint(usually 4 points of articulation) or CV joint( 5 or more points of articulation).
    Everyone's talking about the dog bone style end of the Traxxas CVDs that goes into the differential output.
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  20. #20
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    Quote Originally Posted by airmaxx23 View Post
    Everyone's talking about the dog bone style end of the Traxxas CVDs that goes into the differential output.
    Exactly. It's based on old design ideas from before the 1900s, maybe even 1800s. It would be nice to have a design based on true CVs or stronger Ujoints from Traxxas. In the designs pictured here the cups ears have to be fairly long for the travel lengths. The longer cups are not efficient, cups in general aren't efficient as they can bind twice per revolution. The joint on the axle end of the Summit is pretty efficient.

  21. #21
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    With a fixed joint on both ends, how is the axle supposed to move in and out.

  22. #22
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    well the obvious answer to that is a slip yoke like in the stock axles but you can only make those things so small before they become fragile. could only imagine how many axles we would go through if we had smaller slip yoke on the stock axles with the motors we run sheesh o.o

  23. #23
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    Quote Originally Posted by SiNiST3R View Post
    With a fixed joint on both ends, how is the axle supposed to move in and out.
    Basically very similar to the stock plastic shafts just made out of steel. I used this style on my basher Slash 4x4.

    Last edited by airmaxx23; 10-25-2012 at 02:54 PM.
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  24. #24
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    I can't see the picture, just a little box with a ? In it

  25. #25
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    Quote Originally Posted by SiNiST3R View Post
    I can't see the picture, just a little box with a ? In it
    Try again...I was editing the post. It should work now.
    Last edited by airmaxx23; 10-25-2012 at 02:55 PM.
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  26. #26
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    This is how the real trucks/cars are done. Remember when CVs first came out a lot with front wheel drive cars and the massive failures. Designs had to be improved

  27. #27
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    Traxxas cvds hold up pretty good other than bending in a good crash or common wear

  28. #28
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    Looks pretty sweet' but at the same time a heck of a lot of rotating mass.

  29. #29
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    Quote Originally Posted by SiNiST3R View Post
    Looks pretty sweet' but at the same time a heck of a lot of rotating mass.
    They added quite a bit of weight to my basher Slash 4x4 but they were probably the only thing that I didn't break.
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  30. #30
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    So the Traxxas style is lower mass, less drivetrain loss, and unless you have problems breaking them, more efficient in the thend as the additional mass of those CVDs cancels out benefits from the joint on each end, unless ofcorse you constantly breaks the Traxxas CVDs making this option more desirable.

  31. #31
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    Except it isn't an option...
    As far as I know, MIP does not make a set for the 16ths.
    Whatever it is I just typed... could be wrong.

  32. #32
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    Quote Originally Posted by Jimmie Neutron View Post
    Except it isn't an option...
    As far as I know, MIP does not make a set for the 16ths.
    They don't, I just posted the pic for visual reference.
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  33. #33
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    Quote Originally Posted by airmaxx23 View Post
    They don't, I just posted the pic for visual reference.
    I would buy them if they did. The ends on that design are like the axle ends for the Summit.

    In the meantime, I'm going to try and develop a u joint retainer to try to keep the joints from seperating. Or maybe take the Traxxas joint, cut off the 4 pins then drill and tap,etc--but that's a lot of work. I'm sure there's other options too, such as trying to use the same type of joint in the drawing on the diff end.

  34. #34
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    I think the issue here isn't even traxxas not engineering something a certain way but more of physics at the scale the merv an other vehicles are at don't handle the power or wheels we are pushing them to handle.
    Last edited by Dadx2mj; 10-26-2012 at 10:25 AM. Reason: content

  35. #35
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    The 7151x are plenty strong. You don't hear people twisting them under power and they do a good job for how light they are.
    The cvds on my t maxx are huge!
    Last edited by Dadx2mj; 10-26-2012 at 10:25 AM. Reason: content

  36. #36
    RC Turnbuckle Jr. Dadx2mj's Avatar
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    A few posts have been edited in this thread. Please guys this is a Traxxas only forum so let's leave the talk about other brands out of the conversation.
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  37. #37
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    While were talking about cvd's, does anyone know where i can get a replacement pin from? see pic.



    I lost the pin that was under the rubber band. Surprisingly, after the bad landing the rubber band was still in place so the pin must have snapped... having shot bearings in the carriers might have played a part.... is there a rebuild kit out there? Anyone elsehave the same problem?

    Oh, also, does anyone know where i can get the grub screw pins from (2nd build)? i have searched high n low... Thanks
    Last edited by mervmania; 10-28-2012 at 05:44 AM.

  38. #38
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    there is a rebuild kit available, not sure if it has those pins or not, but i think you can buy those pins in a replacement set also

  39. #39
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    well i think your wrong jimbo! Jokes, nice footer lol!

    I have searched for a while and cant find them.... Can anyone give me a link pls?

  40. #40
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    Whatever it is I just typed... could be wrong.

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