68 Spoke Micargi Wheels

Discussion in 'Frame Mounted Engines' started by RoverGT, Dec 7, 2011.

  1. RoverGT

    RoverGT New Member

    I could use some advice. I own a Micargi Rover GT with wheels that have the 68 spoke fan setup (see attached). I love the bike and the wheels and would like to make them work with my "mega motor" kit from bikeberry.com. The stock rag method isn't working out very well for three reasons:

    1. The hub flange diameter is too wide for the rubber gaskets to work properly. It causes the gasket to flex making it impossible to push more than 3 bolts through to secure the sprocket.
    2. The spokes just outside of the hub where they attach to the flange are too close together to allow the bolts through.
    3. The hole in the stock sprocket isn't wide enough to fit over the dust cover.

    I over-came the sprocket hole problem (#3) with a 2" hole saw. It's not a big deal as long as you take your time, use low RPMs with your drill, and are careful to keep the hole centered. I clamped a guide and the sprocket to my work bench to keep the hole saw steady and centered. The other two problems I have not been able to overcome yet with the stock setup. I did get the bike cranked and running with the 3 bolts I mentioned. However, I don't recommend this for long term bike function. After getting the bike cranked, riding it about 1 mile to get the idle set etc., the 3 bolt setup already started to chew on the spokes to the point where it would have ruined the wheel had I continued to ride it. I've disassembled that and I'm working on trying another solution.

    I'd appreciate some advice on my potential solution. I want to try mounting the sprocket directly to the hub. My plan is this: I'll tap four 1/4" machine screws into the sprocket and hub. I'll space the sprocket away from the hub using 1/4" hex nuts to keep the sprocket from rubbing the spokes and pushing them off the hub (bad news if that happens!). I'll use lock nuts and washers on the inside of the hub to secure the sprocket. Seems fairly simple and straight forward. However, I'm not sure how sturdy it will be. Will it stand up to the torque of the engine? Will four bolts be enough? What kind of bolts are best?
     

    Attached Files:


  2. RoverGT

    RoverGT New Member

    A couple of updates...

    I did some work on this last night and quickly discovered that using the 1/4" nuts as spacers between the sprocket and hub will not work because you can no longer turn the bolt head to tighten the sprocket to the hub...at least easily. Instead I'm using one of the three silver semi-circular brackets that you would normally use to implement the rag clamp as a spacer between the sprocket and hub. I've cut it into three sections using a dremel, and have tacked each piece to the hub with a small dot of JB Weld (pic coming) to hold it in place while I finish up enlarging the hole on the sprocket. The other two semi-circular brackets actually make a nice "guide" to keep the hole saw from skipping around and chewing up your sprocket, work bench, arms, legs, and face. Some WD40 helps keep the RPMs consistant and SLOW to keep from melting your bit etc. I measured the positioning of the hole carefully using a piece of string, a small ruler, and a sharpie. So far so good. I'll finish up the drilling tonight and start tapping the new holes for the bolts on the sprocket.
     

    Attached Files:

    Last edited: Dec 8, 2011
  3. can be done.

    I have seen a very similar setup used with great results!!
    Although it wasnt on 68 straight spoked wheel, it was essentialy the same setup, drilling through the wide flange hub and using spacers to get the chain line perfect. Also, the original 6 holes that are the same as disc brake rotor size were used.
    4 bolts may suffice?? Pocket bike sprockets only use 4 bolt mounts and they seem to hold up OK................:detective:

    Luuuvve the look of straight spoked wheels!!!!!
     
    Last edited: Dec 8, 2011
  4. RoverGT

    RoverGT New Member

    I tapped the hub and bolted the sprocket in today using 1/4 inch grade 8 bolts each 1" long. I used a unibit to tap both the hub and the sprocket. I spaced the sprocket away from the spokes using grade 8 lock washers. I was able to get 6 bolts in. On the inside of the hub I used a flat washer and another lock washer and then a grade 8 hex nut with some blue lock tite to keep the chain vibration from loosening them. It's rock solid. Rode all day today with no problems. If you take your time and use some cutting fluid of some kind like wd40 you'll be in good shape. My only advice on these particular wheels would be to use a ~1.75" hole saw instead of the two inch when boring the sprocket. While i was at it, i cut a 1" x 1/4" slot in the sprocket from the inside hole toward the teeth using a dremel and a cutting disk to allow me to slip the sprocket over the brake arm without disassembling the hub. Big time saver. This will leave a little room to move when tapping the hub so that you don't clip the end of a spoke. Still tweaking and tuning other aspects of the bike, but the sprocket is mounted securely. If anyone needs help with doing the same thing let me know.
     
    Last edited: Dec 10, 2011
  5. Delsiii

    Delsiii New Member

    OK How about this ! The hub adapter looks like it has room on the axel to move. @ 34 for 1 side the common # is a little less than 5 0r 7 if you wish. Now take 2 round disk and cut them in 1/2 the same size as the dia. of the sprocket and 1.75 hole machined in the centre. The reason is you will have to rotate 1 of them 90 so when you bolt the adapter to them inside the hub there is strength with the cuts and only 3 points of contact. Now the farther you move away from the hub the larger the space between them. You should be able to bolt through the spokes with spacers to the sprocket with 6 bolts and maybe have to ofset 1 a bit .... should be the last thing that falls apart on that Bike I would think.. What have I missed ??
     
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