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Thread: SlipStream / UniTine Comparison

  1. #1

    SlipStream / UniTine Comparison

    At this point, I have to say I am at least 90% certain that a Frog Legs UniTine fork will fit directly on the fork stem on the new ZR/ZRA Series 2. This UniTine is over a year old and is the version made by Frog Legs for Quickie. Because Quickie uses a 12 mm metric bearing instead of standard 2R8RS fork stem bearings, it wouldn't fit on a TiLite fork stem. As these pics show, however, if the only difference between this UniTine and the current version of the UniTine Frog Legs makes for Invacare/TopEnd/TiLite models is the amount of space milled out for the bearings, they will fit the latest ZR/ZRA S2 fork stem. At first glance, they look almost identical.



    The two forks take slightly different paths to get the caster aligned with the fork stem. These differences may explain some of the characteristics with their caster axle designs. Most-notably, the side of the UniTine curves inward about halfway down the fork while the SlipStream remains absolutely straight.



    Because the side of the fork is straight on the SlipStream, the caster axle needs to be longer to get the caster aligned under the fork stem. To maintain the necessary space between the side of the fork and the hub of the caster, the SlipStream's axle has a tapered section that functions like an integrated spacer. The additional length of the axle means more torque is exerted by the caster axle against the side of the fork. This may explain, in part, the need for a stronger larger diameter axle (and hence the need for the now infamous R6 bearing). Because of the UniTine's curve, the caster's hub ends up being located much closer to the side of the fork. Less distance means less leverage. Less leverage means less torque. Less torque means less stress. Less stress means a caster axle diameter designed to accept a 608 bearing can safely be used on a one sided fork without an increased risk of failure.

    The SlipStream caster axle is threaded and screws into the fork while the UniTine is smooth and attached with a button head cap screw on the outside of the fork (the screw itself is identical to the screw used to mount the caster at the other end).

    Isn't it amazing how much difference there is in the design of two forks/casters that look so much alike?
    Last edited by SCI_OTR; 10-27-2010 at 09:44 AM.

  2. #2
    Fantastic write-up as always. Thanks again for all of the effort you put into this.

    An aside: What are the respective weights of these particular SlipStream and the Uni-tine forks including axles and casters? Visually, the Uni-Tine seems more robust and probably weightier.

  3. #3
    Nice review, that`s is going to be helpful.
    i`ve got another question.
    I`m going to order a new ZR series 2, have tilite removable push handles?

    Any pic of bolt-on pushles and bolt-on height adjustable bolt-on pushles?
    If you don`t have any pics, will be height adjustables ones similar than this ones?
    Thanks.

  4. #4
    Quote Originally Posted by stephen212 View Post
    Fantastic write-up as always. Thanks again for all of the effort you put into this.

    An aside: What are the respective weights of these particular SlipStream and the Uni-tine forks including axles and casters? Visually, the Uni-Tine seems more robust and probably weightier.
    As one of my favorite characters from South Park would say

    Quote Originally Posted by stanmarsh
    "Don't know. Don't care"
    For all I know, TiLite may be manufacturing the SlipStream from a proprietary alloy of depleted uranium which is 4x's lighter than standard depleted uranium, is marginally stronger and lighter than aluminum, but costs 4x's as much.

    All I was really looking at was the potential interchangeability of the two parts to assist in identifying options for potential and current end users.

    My analysis was mostly to provide an FYI for the curious. In pointing out the design differences, however, I hope anyone who sees this and is contemplating milling out the hub of a FL aluminum hub soft roll to fit an R6 bearing or milling down a SlipStream caster axle to accommodate a 608 bearing will think twice.

    My question to you Stephen, Does the Quickie version of the UniTine seen in this post appear to be identical in it's dimensions/recesses as your UniTine?

  5. #5
    SCI_OTR,

    i'm thinking about buying the unitine.i have seen people using it, but only on ZR.kinda hard to find TR in this case.will it fit?does ZR have the same fork stem as the TR? *curious*

    And since i have the 1" caster, kinda waste to dump it.but i would love the 1.5".do frog legs supply both of the shaft or do i need to buy them separately for 1" and 1.5"? (sorry if my question is wrong due to wrong understanding)
    walking is OVER-RATED!!!

    Broken in August 14th, 2003. T9-L1 complete.

  6. #6
    Quote Originally Posted by SCI_OTR View Post
    My question to you Stephen, Does the Quickie version of the UniTine seen in this post appear to be identical in it's dimensions/recesses as your UniTine?
    Aside from very subtle differences in the fork head, for the purposes of your "analysis" the Quickie and TiLite versions of the Uni-Tine appear to be identical.

  7. #7
    Senior Member DaleB's Avatar
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    Awesome. Unitines, ftw! Thanks for putting the nails in this coffin.
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  8. #8
    Quote Originally Posted by SCI_OTR View Post

    The two forks take slightly different paths to get the caster aligned with the fork stem, but these differences may explain some of the differences in their caster axle designs. Most-notably, the side of the UniTine curves inward about halfway down the fork while the SlipStream remains absolutely straight.


    Judging from the bottom picture, the Slipstream design, with more of its caster axle exposed, is much more likely to collect hair, etc. than the Uni-Tine. This is almost a non-issue with my Uni-Tines.

  9. #9
    Good write-up with great pictures.
    C5-6 Complete - 8/13/1982

  10. #10
    Quote Originally Posted by nia adha View Post
    SCI_OTR,

    i'm thinking about buying the unitine.i have seen people using it, but only on ZR.kinda hard to find TR in this case.will it fit?does ZR have the same fork stem as the TR? *curious*
    Yes.

    Quote Originally Posted by nia adha View Post
    And since i have the 1" caster, kinda waste to dump it.but i would love the 1.5".do frog legs supply both of the shaft or do i need to buy them separately for 1" and 1.5"? (sorry if my question is wrong due to wrong understanding)
    The axle will work with either caster.

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