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One throttle cable

Discussion in 'Norton Commando Motorcycles (Classic)' started by madass140, May 21, 2017.

  1. RoadScholar

    RoadScholar VIP MEMBER

    Joined:
    Dec 28, 2008
    So, how often does the Norton (British motorcycle) owner change slides or needle positions?? Once, possibly twice, during the run of the tuning? Yes it is a PITA, but I'd rather do that than shim the old Isolastics...
     
  2. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    yes RoadScholar I agree, I think those concerns are coming mainly from the racer set and with good reason. I had considered having the option but If I was to make a good production run then I would make them all the same "racer style" .
    Don
     
  3. nortriubuell

    nortriubuell

    Joined:
    Aug 29, 2010
    Kewl ... 8) Thanks for posting Don :)
     
  4. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Very nice project, Don! And elegant too.

    A couple concerns. The top plate needs very accurate machining to seal the carb tops. I guess you cnc-machined your sample.
    Also, are carbs manufactured accurately enough to warrant the top plate will fit any carb pair? A slight twist between flange and body, and the plate will no longer fit.

    Wouldn't it be better to leave the Amal carb top covers in place and make an actuator fitted on a forked sheet metal structure of 2mm thickness clamped between the carb and inlet manifolds, sort of T160 style? It would be cheaper to manufacture and would facilitate a cable restraint as well, rather than your fatigue-prone bracket. Re. concerns of stiffness, the structure could be additionally supported at the balancer tubes which are threaded in your application. It's all a bit tight but I believe it could work.

    Rgds.

    Knut Sonsteby
     
  5. Brooking 850

    Brooking 850 VIP MEMBER

    Joined:
    Oct 3, 2011
    Hi Don, I could do with that system on my race bike as I am running Mk1 Premiers and irt would fit my bike very well.
    Once you go intp production, I am up for a set , will you make 2 x options, one system to accommodate chokes and one without?
    I dont use chokes on mine.
    Also while I have your attention, I need a new tank cap rubber seal for that gas tank you made for me, any idea the part number?
    Regards Mike
     
  6. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    https://photos.smugmug.com/One-cable/i- ... 003-XL.jpg

    Geez Knut you're on the ball, I was going to post some pics later today with it all together but here is the latest.
    Regarding your other concerns
    I tried fitting the plate to a 2 unmatched carbs from many years apart and found one carb was taller than the other.
    I since tried it on a pair of Amal Premiers and a pair of Wassell (Premiers) and both were the same height.
    This would be the scenario when fitting the plate " slightly loosen the 4 carb allen screw mounting bolts, fit the top plate with all 4 screws tightened
    then tighten the 4 4 carb mounting allen screws. this seems to work fine.
    Todays project is looking at alternatives for cable restraint,
    thanks for the input
    Don your bits went out yesterday
     
  7. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    https://donaldpender.smugmug.com/One-cable/i-JpNBp5L
    https://donaldpender.smugmug.com/One-cable/i-thTZB2b
    https://donaldpender.smugmug.com/One-cable/i-vSrwdqw
    It will be something like this, looks like the cable riser restraint will be TIG welded on.
    It will come with 4 longer carb top screws and probably a new set of slide springs
    When ? 2 months or so I reckon
    How much ? havent got a clue but it will be affordable and a good investment.
    Remember you will be riding down the road knowing that them carbs are always in synch.
     
  8. speirmoor

    speirmoor VIP MEMBER

    Joined:
    Apr 11, 2010
    Thats a sweet setup Don
     
  9. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Hi Don,do you have seals fitted to the carb tops? And what sort of bearing/bush is used on the pivot? Cheers
     
  10. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    not shown but there will be seals (guides) for the lift cables. the main shaft pivots on the 5/16" heim joints (rod ends) I was going to fit very small bearings
    in the other end for the trunions but cancelled that, a drop of oil once in a blue moon on them should suffice.
     
  11. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    Sounds extremely good, cheers
     
  12. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Don, TIG welding is an improvement, but the right angle cable riser restraint is an extreme stress riser design. Ideally the transition should be evenly curved and the joint should be on the straight section. If you can't fabricate it accordingly, I strongly recommend welding a small triangular stiffener centrally located at the transition. It´s still not ideal.

    A better design would be to make the riser restraint out of a bar rod shaped like a polygon and weld it horizontally on top of the plate by a circumferential fillet weld twice the length of the riser restraint width. This ensures low stresses in weld seam as well as in the riser restraint. I would weld before machining the plate underside, to ensure perfect flatness.

    Best regards,

    Knut Sonsteby
     
  13. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    yes I had thought about using rod . Its only got to take the load of 2 light springs, I'm not at all concerned about the strength of the bracket or its weld.
     
  14. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Don, the potential failure is due to fatigue, not static load. Cantilever design means a low eigenfrequency. That's why the T160 design is a heavily ribbed non-welded design which meakes it much stiffer, increases natural frequency and ensures no residual stress. Please remember that welding aluminum significantly reduces yield stress and produces high residual stresses, unless post-weld heat treatment is applied.

    Based on an assumed cross section of 5x30mm, a length of 100mm and aluminum as material,
    the first natural frequencies are f0=411 Hz and f1=2567 Hz. f0 may be excited by the firing interval of each cylinder at idle and is probably the most dangerous excitation due to high amplitude.
    f1 may be excited by the crankshaft at normal running revs or by each firing cylinder at higher revs. It's dangerous due to being a sustained load.

    A bar rod could be welded top/bottom of the plate by providing an oblique drilling. Assuming a Ø10mm rod and identical data otherwise, the first natural frequencies are f0=727 Hz and f1=4546 Hz. This ensures far less likelihood of excitation, IMHO.

    -Knut
     
  15. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    1/4" x 3/4" over 2-1/2"
     
  16. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    ". It's dangerous due to being a sustained load."
    Ok lets put this "load" in to perspective. Put a slide spring between finger and thumb and compress it 1" (25.4mm)
    Now x 2 , would you really consider that sustained load enough to cause the weld to fracture??
    Keep in mind I intend supplying lighter springs.
     
  17. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    The data you provide yields first natural frequencies of f0=1261 Hz and f1=7880 Hz. f0 is out of normal idling rev excitation which is assuring. It may still be excited by the firing interval of each cylinder at normal running revs. The excitation amplitude is probably fairly low. f1 is not a problem.
    Still, I would consider PWHT.

    I should add that partial weight of cable, ferrule and adjuster hasn't been accounted for, nor has damping effect of the cable. These factors could bring f0 down to 900-950 Hz, which makes the riser restraint susceptible to excitation by idle revs. It's hard to assess these effects without further data.

    -Knut
     
  18. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Don, the potential failure is due to self-weight of the riser restraint and the excitation produced bye the engine. I am dismissing static load by springs as cause of failure.

    Cheers,
    Knut
     
  19. madass140

    madass140 VIP MEMBER

    Joined:
    Nov 6, 2011
    thanks for your input Knut.
     
  20. cliffa

    cliffa

    Joined:
    May 26, 2013
    Hi maddass140 / Don,
    I would definitely be interested in this product if you decide to go forward, however could I make a couple of observations / suggestions ( which I'm sure you have already thought of, and I realize this is a prototype )

    1) Given that the carb tops will be 3 - 5 mm higher than standard (a guess from the pics), is there any danger that at WOT the tip of the needles will pass out the top of the main jet and jam them wide open ? i.e. needle moved to the bottom groove etc. Like I say i'm sure you've thought of it, but it does no harm to ask (especially if you are going to test them out them first)

    2) The lifter arms look a little thin where the ferules pass through, with I'm sure will lead to premature wear (ovulation) is that the right word?

    3) To knut's remarks, how about bending the cable mount in a nice curve which is "Concentric" :wink: with the spindle? No welding stresses, and would look pretty neat.


    [​IMG]


    Cheers,

    cliffa.
     

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