Discussion in 'General Questions' started by Tommy Griffin, Jul 9, 2016.

  1. Tommy Griffin

    Tommy Griffin Member

    image.png image.png I am buying a new wheel for the rear of my motorbike because I have major problems out of coaster brakes. I want to know what I will need to do in order to attack a sprocket to the six holes on the wheel . I am attaching it to a beach cruiser so I'm putting a one gear freewheel on it .

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  2. bakaneko

    bakaneko Active Member

    Hey, charge your phone! Only 15% charge left :eek:. Umm, in all seriousness, Tom and I were over at Lynn's place and I think we talked about this exact thing but unfortunately I have goldfish memory. Send a message to Tom from Rubicon and maybe he can recall exactly what Lynn said about it or can review more insights.
  3. crassius

    crassius Well-Known Member

    google for a sprocket drilled for both 9 hole and 6 hole disc mounts
  4. bakaneko

    bakaneko Active Member

    yes, but he also might need a spacer, which is what Tom and I discussed with Lynn (owner of custommotoredbicycles). i just don't remember the exact specifics of what she said might needs to be done.
  5. mrbg

    mrbg Member

    It looks like a single wall rim , double wall is the ticket for rear wheel.
  6. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    The disc brake rotor is quite far out from centre (and spokes) so that the caliper can fit in there and not get hit by the spokes. If you attach a sprocket directly to the six ISO disc mount holes it would be too far out from the centre line of the bike to match up with your front sprocket.
    The sprocket is likely to be larger diameter than the disc that the frame was intended for anyway (160mm rear is usual) so it would be impossible to fit inside the chainstay (maybe on a fatbike with more parallel chainstays).

    The Kings top hat adapter has two sets of holes so that the sprocket is mounted inside the adapter, 1/8"-1/4" further in towards the centre line. However, when i was looking into this myself I found that it is made with the weird nine hole pattern so you can only use the kit sprocket and the limited choice of (tooth count) sprockets sold by the same company that makes the adapter. It makes commercial sense I guess, but mechanically and for the greater good of the hobby and PEOPLE WHO AREN'T IN THE USA, I really wish they would make them with any of the common standard bicycle chainring bolt patterns. Perhaps they could have both the 9-hole and also a five bolt 74mm or four bolt 104mm standard pattern... Hi there. ;)
    Last edited: Jul 20, 2016
  7. Just went and measured the bolt circle of the wheel Tommy Griffin is interested in. The bolt circle is 44mm.
    When bakaneko and I visited Lynn. she showed us a prototype adaptor plate with a hole pattern that mounted to that hub which was for attaching a brake disc. The drive sprocket could be mounted to either side of the adaptor plate if needed to optimize chain alignment. That said, I have no idea when Lynn will have any made. Consequently I am going to make my own in the near future. I have a 6mm thk. steel disc turned and bored which I will center up in the Bridgeport. Then drill the hub 6 hole pattern and the 3 hole pattern for my drive sprocket.
    Lynn's adapter, when made will be of 7075 T6 aluminum.
    Tom from Rubicon
  8. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    How does this differ from the original top hat adapter made by Kings since eight years ago? ($37.50)

    A FLAT PLATE with two sets of holes could only mount the sprocket so it's outside edge is flush with the six holes on the hub, and that is STILL too far out from the bike's centre line to get a good straight chain line or to clear the chainstay.
    Would you use long bolts and 1/8"- 1/4" of washers to achieve the necessary offset? Would that hold up to the torque? If made from a good hard steel will it weigh far too much?
    To solve these problems the original Kings top hat adapter is more than simply a flat plate with holes. It is machined to give the necessary offset to bring the sprocket closer to the spokes and avoid the chainstay and chain line problems.

    The only drawback I can see of the original Kings 7075 T651 aluminium 3-dimensional top hat adapter was/is that it only fits the MB specific or "kit" sprocket 9 x 8mm hole pattern and not standard bicycle chainring bolt patterns.
    The way you describe it, it sounds like this prototype is either a direct copy or an inferior copy of the original.
  9. Lynn has all sorts of shim rings to adjust sprocket position. I don't know if you have given thought mounting the drive sprocket inboard on the adapter ring. All I know is I have re-bored 50+ steel drive sprockets to I think 54mm ID.
    To be used with her "system" as she calls it. Lynn's adapter has as I recall four bolt circle patterns.
    The adapter I plan on making is to mount the 56 tooth drive sprocket recommended for use with EZ=matic transmission.
    I can Email Lynn to let her know Tommy Griffin wants one of her "systems".
  10. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    Yes, inboard on a flat plate wouldn't do it, that's why the Kings top hat is a top hat shape, gives you 1/8"-1/4" more "inboardness" (two versions available).
    If this new top hat adapter has the bolt pattern for the four bolt mountainbike chainrings that would be a great improvement over the original and I'm all for it. :)
  11. Tommy Griffin

    Tommy Griffin Member

    I just seen that a guy destroyed one of these from the torque on his bike so I dropped it . I'm getting a chrome single speed freewheel and then I gonna use caliper brakes and a hub adapter .
    Tom from Rubicon likes this.
  12. Tommy Griffin.
    I emailed Lynn, this is her reply: "If this guy emails me I can show him what I have."
    Lynn told me she last week that she is doing a build for a 350# fellow. That is quite a load on six 5mm screws.
    That said, as I have a machine shop I am rethreading those disk brake hole to 6x1mm an shrinking a 3mm steel band around the hub for support. Just because I can do it.
    I am a Tool and Die Maker and Lynn's engineering impresses my time and again. She is aware of the inherent danger of these fragile machines and that I appreciate too.
  13. You will have to email Lynn, her universal adapter looked mighty universal. That said, customer input greatly influences product.
    Lynn has several CNC machine shops in the Milwaukee area that make product for her. I am happy to help her out with low volume items.
  14. Do you have a link to the part failure Tommy? My curiosity is killing me. :)
  15. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    I second that. I know that the disc mount can handle massive deceleration forces with a hydraulic brake and 205mm rotor.. and the force needed to stop from a certain speed in a certain amount of time is equal to the force needed to accelerate to the same speed in the same time, so it would be a very strong motor or a very large sprocket to exceed the force exerted by a brake.
    Tom from Rubicon likes this.
  16. Good reply Furry,
    I hope something comes of it
    My enquiry to Tommy is solely based on possible failure by any load. I am using the same laced freewheel hub supplied by Lynn. She was very sure that the hub would withstand the drive force of my 79cc engine.
    That said I am still going to do the old wheelwright method of heat expanding a steel band and let it shrink unto to wheel hub O.D. for additional strength. I may have a foolish streak but I am not stupid, I hope.
    When I get around to doing the above I will post photos.