HPMGuy/R-Dubb triple clamps Group buy - KTM forks on your Airhead!

Discussion in 'Vendors' started by Solo Lobo, Jun 9, 2011.

  1. Solo Lobo

    Solo Lobo airhead or nothing

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    Hi R-Dubb, good to see you 'round again...

    Just to be clear here, are you saying the 640 WP 50mm triple stem won't work with HPMGuy's triples?
    #41
  2. R-dubb

    R-dubb Dubbious Adventurer

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    Jeez, you guys expect me to give up all my secrets :lol3

    Give me a day or so. Will post all the info you need.
    #42
  3. Solo Lobo

    Solo Lobo airhead or nothing

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    Thanks!

    At least three of us have stems that are from the stock WP Extreme triple clamps (me, ontic and walking bear)... need to know if these stems would work if the ID of the triple could be changed and if HPMGuy could even change that ID at this point.
    #43
  4. R-dubb

    R-dubb Dubbious Adventurer

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    Good news!

    It looks like the KTM stems, until very recently, are the same part number (which is the one needed). LC4's & RFS from the WP 50mm Extreme days throught the WP USP 43 and the 48's all use the same 30 x 244mm stem.

    50101033100 FORK TUBE L=244 '91 80.49

    You'll also need the cap.

    54801036000 STEER.HEAD SCREW M20X1,5 WS=27 11.49

    Just to refresh, the idea here was to use BMW bearings because they fit the frame. Then we designed the triple clamps to make a 248 +/- mm sandwich with the 244mm stem. This leaves around 4mm for preload and stack tolerance. The stem modification is only required because the BMW bearings are a little smaller in the waste line.

    Below is the drawing. Guy needs to bore the lower clamps for a 30mm interferance fit like he did last time. They were a little tight but worked with a heavy press and some heat. The vertical transitions can move around to match the KTM stem as it is not critical where the tapers start and stop. They just need to catch the bearings. The bearing tapers shown on the drawing are too big in diameter. I'm a little dumb and 28.10mm is way too large to slide a 28mm bearing over even with heat. Needs to be more like 28.03mm. Not a big deal, but if you heat the bearing and try to stretch it on there it will never come off!!...DAMHIK. So that should also be adjusted accordingly.

    I would not be afraid to make these modifications to the stem using a drill press and a file. Worst that can happen is you mess it up and need to buy a new stem, assuming the measurements are taken somewhat seriously. My recollection is that KTM uses 29mm ID steering bearings, meaning that to take off half a milimeter all the way around is not a big deal. Someone else will be able to measure these and report back. My machinist did about six of them for me last time. Took no time at all. I like the KTM stems because they are hollow, strong, and match up perfectly.

    Thats about it for now on the stem front.

    [​IMG]
    #44
  5. R-dubb

    R-dubb Dubbious Adventurer

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    The bosses on the top clamp were designed to match up with a standard BRP submount.

    The model I ordered from them on the phone (won't come up on web site) is:

    model number: SMO-9018P3 - 90mm spread; 18mm offset.

    It looks like this (very nice!!):

    [​IMG]

    Works with Fat bars and a Scotts Submount Stabilizer

    [​IMG]

    Any generic 12mm bolt, two piece, bar clamp set will also work.
    #45
  6. ontic

    ontic

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    [​IMG]

    Excellent R-Dubb!
    That was exactly what I was hoping for:clap
    very nice to be able to use what I've got, shouldn't be a problem to turn it down- just gotta find someone with a press, and it confirmed some of my measurements and concers- which is always a nice surprise:lol3


    Bar clamps are something I haven't let myself worry about yet... time to think about it maybe.
    Cheers,
    #46
  7. Airhead Wrangler

    Airhead Wrangler Adios Mexico

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    +1, big thanks.
    #47
  8. Airhead Wrangler

    Airhead Wrangler Adios Mexico

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    :ear

    BUMP
    #48
  9. igormortis

    igormortis Cafe Reise

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    Do all KTMs share the same fork spacing? I’m just thinking about what wheels/hubs/brakes/axles will work with which forks.
    #49
  10. Airhead Wrangler

    Airhead Wrangler Adios Mexico

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    Same leg spacing since about '98 or so, but the axles and hubs changed a bunch from around '98 to 2003. The 50mm took one axle, the 4354 forks took another and then the 4860s took a different one. Then to make matters worse, after a couple of years the 4860s switched to a larger axle.
    #50
  11. HPMGuy

    HPMGuy Been here awhile

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    Thanks for posting the clamp/stem drawings R-Dubb!

    I have a sample stem/clamp here now from Airhead Wrangler, I will measure the interference they use between the stem and the clamp and duplicate that when machining the triple. Also, for those who have asked if I would be willing to machine the KTM stem for them and press it in the lower triple, that would not be a problem.

    I will post the rework of the 4860 lower clamp shortly.
    #51
  12. HPMGuy

    HPMGuy Been here awhile

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    Here is the rework of the lower clamp for the 4860s.

    [​IMG]


    As per the info posted by Airhead Wrangler above, the top triple on the 4860s will use the same 54mm bore as the original design, so no change is necessary.
    #52
  13. Country Doc

    Country Doc Wanderer

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    :thumb

    I'll want a set including the stem, already pressed into the triple. Then it's just a matter of popping on the bearings, and bolting 'er up.

    Oh yeah, I need the forks...wheel...frame reinforcements... !!

    dc
    #53
  14. igormortis

    igormortis Cafe Reise

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    Y’know I’m sooo close to making a decision on this... Do you guys all have forks in hand, or is availability of these pretty certain? I just want to be sure I can find a pair of the 50s.
    #54
  15. ontic

    ontic

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    I've got everything in hand now except for these triples:deal
    Well OK, there are still a few things that have't arrived in the mail yet- and I have to machine an extension bracket for an oversized rotor.

    I ended up getting my WP50's locally (reasonably) just by putting a wanted post in the Oz fleamarket (also got a few other bits this way). I did call around local wreckers, and they had them, but their prices were simply insulting (better to buy and part out a donor bike yourself).
    Other than that you can easily pick them up from US or German ebay (amongst other places). I found quoted prices on postage to be a lot cheaper from Germany than from the US, though the forks could often be had a bit cheaper in the US.

    Here is a set of 640adv forks with triples (ready for a 300mm rotor)

    Here is a set of forks alone

    For German ebay, in my experience, most sellers do not seem to offer international postage- I have had my best luck in my initial inquiry by always directly referring them to:
    http://www.dhl.de/en/paket/privatkunden/international/paket.html

    After approaching the german sellers this way, a large majority of them seem to be fine with postage.

    If you want to discuss prices or anything else regarding this, shoot me a PM- like I said, I have finished sourcing everything I need and have gone through a hell of a lot of international ebay hunting and communications,
    Cheers,
    #55
  16. Airhead Wrangler

    Airhead Wrangler Adios Mexico

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    I guess my only suggested change would be that of the material used. I'd suggest 7075T6 over the 6061T6. Below are the relevant mechanical properties for comparison. 7075T6 is superior in just about everything without any real penalty in weight and better machinability. Note the difference in fatigue strengths.

    6061T6

    Ultimate Tensile Strength 310 MPa 45000 psi AA; Typical
    Tensile Yield Strength 276 MPa 40000 psi AA; Typical
    Fatigue Strength 96.5 MPa 14000 psi AA; 500,000,000 cycles completely reversed stress; RR Moore machine/specimen
    Density 2.7 g/cc 0.0975 lb/in³
    Machinability 50 % 50 % 0-100 Scale of Aluminum Alloys
    Shear Strength 207 MPa 30000 psi
    Fracture Toughness 29 MPa-m½ 26.4 ksi-in½
    Hardness, Brinell 95 95 AA; Typical; 500 g load; 10 mm ball


    7075T6

    Ultimate Tensile Strength 572 MPa 83000 psi AA; Typical
    Tensile Yield Strength 503 MPa 73000 psi AA; Typical
    Fatigue Strength 159 MPa 23000 psi AA; 500,000,000 cycles completely reversed stress; RR Moore machine/specimen
    Density 2.81 g/cc 0.102 lb/in³
    Machinability 70 % 70 % 0-100 Scale of Aluminum Alloys
    Shear Strength 331 MPa 48000 psi
    Hardness, Brinell 150 150 AA; Typical; 500 g load; 10 mm ball
    #56
  17. Garthe

    Garthe ROCKS ARE YOUR FRIENDS...

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    OK, how do I get on the 'list'...WP EX 50mm BLACK.

    Also intrested in having a stem made/fitted, if possible.

    What's the price, lead time and how/where do we send $$$.

    Thanks for all the work in setting this up...:freaky

    [​IMG]

    I would like to use this handle bar clamp. Will this be a special order? Or, will the spacing already be set up this way?
    #57
  18. Solo Lobo

    Solo Lobo airhead or nothing

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    I've put you on the list, but send a PM to HPMGuy with your request to be certain
    #58
  19. Garthe

    Garthe ROCKS ARE YOUR FRIENDS...

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    ^:bow:clap
    #59
  20. Adrian V

    Adrian V Been here awhile

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    I'm thinking about building up a GS, possibly with a Rooney frame. Could someone fill me in on the advantages/disadvantages of the different ktm forks? Why are people going for the 50mm Extremes rather than the 4860's?

    Cheers,

    Adrian
    #60