68 Spoke wheel help needed

Discussion in 'Frame Mounted Engines' started by DutchDude, Aug 13, 2007.

  1. DutchDude

    DutchDude Guest

    Like Duane already predicted - I am having problems fitting the sprocket. But my wife choose the bike, so I am kinda stuck with it :)

    As you can see in the first two pictures, there are two problems.

    1. The hub is 70 mm, and the inner diameter of the holes in the sprocket is 65 mm

    2. Too many spokes, so the bolds don't line up.



    As you can see, you can actually see the hub through the bold holes. As well as the many obstructions of spokes :)
    Last edited by a moderator: Aug 14, 2007

  2. DutchDude

    DutchDude Guest

    Last edited by a moderator: Aug 14, 2007
  3. npk1977

    npk1977 Guest

    Interesting & fun idea. I'm not qualified to answer your question, but I can offer a solution: take the hub to a qualified machinist. I guess that you want your hole pattern to be concentric to the axle. A real machinist will be able to (1) drill a nice concentric hole-pattern and (2) give you some advice to tell you if the idea is stupid or not :)

  4. DutchDude

    DutchDude Guest

    Alright - I was thinking of drilling it myself - but just what do you think a machinest would charge for 9 holes in hub and sprocket (18 total)? Might be less of a headache, if it is reasonable...
  5. srdavo

    srdavo Active Member

  6. japat100

    japat100 Guest

    it is not only to drill holes ,,but you must have a way to center the sprocket and keep it centered ,in other words the holes alone with bolts will not keep it centered

    , i place 8 3/16 bolts with lock nuts and made a adapter plate 1/4 thick to fit the small ridge on the hub ,and the other side made to fit the hole in the sprocket that would keep it centered .,, very time consuming to get it right ,, if you knew someone with a lathe that tinkers may get it done with little cost ,but i would not want to think how much it would be at machine shop charge by the hour ,but you could get a set price ,,
    it worked out great for me because i have a lathe and plenty of time ,, and in my opinion a much better way to place sprocket then using the spoke system .. no broken spokes and my spokes are very small gage ,,,and the sprocket is very true ,,, may have about 300 miles on bike so far with no sign of problem

    you may have a biggest problem and cost 10 times more if you change bike style ,,, did i hear you say the wife choose the bike


    Last edited by a moderator: Aug 14, 2007
  7. DutchDude

    DutchDude Guest

    I like that idea of the adapter - but that still has me drilling the same holes in the hub itself. I think I would be more comfortable with more holes then six. Doesn't the torque on a bold increase, the less holes you use? From just looking at it, and the amount of material available, it looks like you can fit between 8 and 10 bolds.

    So, technically, it seems the only thing $65 would buy me is a hole pattern, that might, or might not center itself on the hub? And perhaps even an added problem of increased thickness/clearance. That money is probably best spend on a new wheel or hub, if I screw mine up :)
  8. DutchDude

    DutchDude Guest

    I probably should figure out a way to drill the hole pattern in the sprocket first. Evenly, in a perfect circle, with perfect spacing :) Any suggestions there?

    Then, I was hoping to be able to modify the dustcap with a dremel so that it would fit perfectly inside the sprocket hole? When I would hold down the dust cap, shouldn't it hold the sprocket in place long enough to drilll a perfect hole pattern through the sprocket?
  9. drimpact

    drimpact Member

    personally I would get a heavy duty rear wheal with 36 12guage spokes and not drill my sprocket.

    Just my opinion, but having a concentrically mounted sprocket is absolutely positively necessary for smooth operation.

    The hub also does not look very thick, you might have issues just bolting the sprocket onto it.

    If this were my bike project I would look for the heavy duty wheel. Take it or leave it, It is only my opinion.

  10. japat100

    japat100 Guest

    drill holes in sprocket first no problem ,, then place the sprocket over the hub no problem ,,, the trick part is that the sprocket must fit over the ridge part of the hub to be centered ,,, thats why you need adapter plate about 1/4 inch thick .. even if you could make the hole in the sprocket the right size to fit the small ridge on the hub it would still not work ,, because the spokes are about 1/8 sticking out of the hub that would be enough to keep the sprocket from seating flat against the hub ,,,and then the sprocket would be pressing against the spoke ends instead of seating flat against the hub

    ,the sprocket must press against the center of the hub to keep it centered ,,and thats the job for the adapter one side of the adapter fits tight against the center of the hub ,and the other side of the adapter fits the hole in the sprocket
    not sure when you say dust cap what you mean ,,but as i understand you are going to keep the dust cap in place until you drill the holes ""no problem "", but bolts alone even if you get them perfect will not whole the sprocket centered on the hub for any length of time ,you may get a few miles out of it before it becomes off centered ,, only the adapter in my view will keep it centered
    Last edited by a moderator: Aug 14, 2007
  11. japat100

    japat100 Guest

    theres another way you could try that may be easier ,,i did not do it this way but its worth a try,
    take a 1 1/2 inch or 2 inch washer about 3/16 thick , fit it over the center of the hub make sure you fit it tight and even around the ridge of the hub ,, then you could go to a machine shop or someone with a lathe and tell him you want the washer tack welded on the center of the sprocket ,,tack welded to ovoid too much heat ,,this would cost you very little to do and would only take a few minutes ,

    ,note ,,tell the machine shop guy that the hole you put in the washer to be centered on the sprocket ,,not necessary that the outside of the washer be centered ,just in case your filing job when cockeyed

    then place the sprocket over the hub with the washer ,the washer keeps it centered and also acts as a spacer to avoid the sprocket sitting on the ends of the spokes and then drill your 8 3/16 holes ,, should work fine
    the hub seems plenty strong to bolt to ,and should have no problem but i would not go over 3/16 drill holes

    worth a try
    Last edited by a moderator: Aug 14, 2007
  12. DutchDude

    DutchDude Guest

    The sprocket hole is about 1/8" larger then the ridge part of the hub. So accept for the spoke ends, it lays flat.

    The original design has this conveyor belt stuff the gets wedged on either side of the spoke, and then compressed. If I were to cut some up and lay it on the hub before putting on the sprocket? Or, perhaps cut of the ends of automotive valve stems (thick rubber washer)?
  13. DutchDude

    DutchDude Guest

    I do own a mig welder, so I could do the tacks myself. But, unless the washer doesn't have a hole in it for starters, or if it fits just perfectly without any room on the sides before welding - it could still end up slightly off center. Might be worth a shot to see what size washer I could find though.

    I would perhaps use it to make a three hole jig? Put a peg in the center of the sprocket, and the center of a scrap board. Drill through one of the nine holes of the sprocket into the board, put a bold in it. Then drill the first 3/16" new hole. Rotate around center and repeat?

    Using the washer method for the hub drilling might be difficult. There is at least 3/8" of space to deal with because of the bearings and the oval shaped brake lever mount.

    I like the way you think though - keep it coming :)
  14. japat100

    japat100 Guest

    i am thinking back ,, that i also had to add "weld " a washer to the arm for the brake since i have coaster breaks ,,, i shaped the inside of the washer the same as the the hole in the arm ,, that allowed me to insert the arm on after i bolted the sprocket on ..the washer on acted as a spacer also so that the arm would clear the sprocket and since the washer had the same hole in it as the arm it held the cone in place ,,
    you may get away with a 1/8 washer for the sprocket as long as the spokes don.t stick out to far ,,1/8 would be easy to file down so it fits perfect on the hub ,, you do have a dremel tool and power saw file would be handy ,,washer come in many different sizes with different size holes so the secret would be to save you a lot of work is to get one that close to the righ size hole
    perfect center is important ,if you are out even a few thousands the chain will very back and forth from loose to thigh ,,

    after you fit the washer you may get away with a wooden lathe ,take a piece of hardwood and make a axle
    so it fits the sprocket and the washer ,,then tack the washer lightly with the mig until you have it on the money
    once you have that down ,,then you can drill 8 holes " 8 holes works out good on the hub "" in the sprocket in the right place o fcourse """right diam."",, then place your sprocket in place held on by clamps ,then you can drill the hub holes using the sprocket pattern ,,i drill each hole then put in a bolt and nut in each hole as i went along tighten just snug ,,also drill holes criss cross from one side to the other so that the sprocket went on even ,,

    hope this maybe some help