Sprocket bolted to drilled flip/flop

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Nashville Kat

Nashville Kat

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Apr 20, 2009
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Getting ready to do this Huffy cruiser build- this is a 41 stock sprocket bolted directly to a flip flop rear hub I got on Craigslist. The sprock has the six inner Disk brake hole configuration with minimal bolts. the flip/flop is high flanged and didn't have any natural holes- not TOO hard to find- so it was easil to drill the alloy. The diameter of a flip/flop and our sprokets are the same- except nothing threads on, so it must be bolted or rag jointed anyway

The bike has 700 c wheels with 28 mm tires (1 1/8"), handbrakes front and rear (with a double pull hand lever, naturally!) , alloy seat post, single speed low rider 38 front sprocket and rear freewheel. The bars and stem are also alloy.

It's extremely light- wish I had a bathroom scale- need to lose weight anyway!

will be motored with 50cc slant head 2 stroke china girl, and smaller tank.

Took it out for a test ride before I shot these- rolls great. Should be about the lightest thing going.

.ride9
 

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happycheapskate

happycheapskate

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If I understand you right, the left side cog was pre-drilled for disk-brake hubs, but the hub is a generic flip-flop (aka track) hub?

How did you mark the hub for drilling the bolt holes?
What size bolts did you use?

This looks like a good cheap way to get a motor on a used road bike.

I have thought of using a flip flop hub with a 20t fixed-wheel cog on the left side and just running the motor on that. I don't know if the motor is big enough (49cc) to pull that though, wth a 26x1.75 wheel & tire.
 
Nashville Kat

Nashville Kat

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Apr 20, 2009
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I think the 20 is way too big a gear especially for a 50- it'd be nice if they just made a thread on 36 or 40 track cog huh? Solve all the problems- I've searched for one- no luck. I think the lockring WOULD hold it on, but threads are reversed.

No this flip flop is large flange, and had undrilled smooth sides. A lot have holes in them, and might work, but these smooth undrilled ones are out there if you look- These just hapened to pop up on Craigslist.

The kit sprocket didn't have the six inner holes but I had an unused 32 that does and I used it as a pattern- I actually bolted the two together to drill the one.

I don't recall the drill size- I just matched it up- a new bit helped quicken it- and the bolts are standard rag joint kit bolts- fairly short ones that came with the kit.

Still haven't put the motor on- tired and busy with other things. The other cruiser has been getting some use.
http://motorbicycling.com/f46/show-off-your-motorized-bicycle-8357-3.html#post233691

Here's the motor:
 

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Nashville Kat

Nashville Kat

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Apr 20, 2009
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Heres a link to a flip/flop that has high flanges and is not yet otherwise drilled out-

Bulletproof BMX Rear Hub LF 48 x 14 Black Sealed Flip Flop

If you're nervous about the drillings, look at those on any other high quality high flanged road hub (Campagnolo, Shimano) and you can see that their drillings usually have even more of the hub sides absent. Newer hubs that are already drilled often have a teardrop shaped drilling- not sure if it would work, but like I said, the alloy flange drills quite easily. a steel motor sprocket is a bit harder- get a good new bit! You can probably go with smaller bolts and drillings if you are drilling both yourself- and maybe even a 4 hole pattern, for even less weight!
The bolts are very supported by the hub otherwise.

This vendor on ebay sells the sprockets with the 6 inner drillings- boygofast has them on request too.

http://cgi.ebay.com/motor-motorized...924?pt=LH_DefaultDomain_0&hash=item5d2bfde09c
 
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happycheapskate

happycheapskate

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You have a cool idea, and I've passed it on, but I've got a simple enough idea:

Run a 20" wheel in the back, with the 20t fixed/20, 18, or 15t for the pedal side. I'd have to weld on a simple cross brace and drill a center hole, in order to mount the rear caliper brake, but that should not be too hard, esp on a hardy steel beach frame.

This should give a low inertia wheel that the motor can get on top of even at pretty low RPM, with scary fast top speed. :)
 
Nashville Kat

Nashville Kat

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Apr 20, 2009
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Jacksonville, Florida
Here's the tank-

It actually looks a little better than the photo, which tunes out some of the glitter and looks more gravelly- and I'm still clearcoating-

I haven't gotten this build together yet- I ordered some longer back mounting studs to use my "wrap around" technique on the ground wider front mounts- they got here a few days ago-

but I been messing with the other one- and two of these in a 1 bedroom apt is really a little too much- and two other bicycles too!

I was almost gonna sell the orange Huffy- but it's this drilled flip/flop that keeps me building it up- I just wanna see what it does.

The build should go really fast now when I turn my attention to it.

.santa
 

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Nashville Kat

Nashville Kat

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Apr 20, 2009
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Jacksonville, Florida
Check out these 700c wheels!

I got this build done afew days back- just gotta take some pictures- it's really fun-

meanwhile,

check out these 700C wheels I just found on ebay-
Track Road Bike Fixed Gear 700c Wheels Wheelset F&R NEW - eBay (item 330510545021 end time Jan-19-11 13:43:46 PST)

It looks like the flip/flop hubs are LARGE FLANGED and good candiates for drilling-

and LOOK AT ALL THE COLORS!
These must be just off the boat from Japan. Never seen em before. Bet they sell fast for fixies.

This ebay storehas several varieties of wheels in all sizes and colors so click on the store link when you get there-

The beauty of 700C though is that you can use a frewheel and handbrakes on a cruiser frame instead of being locked into a coaster brake -

I love this size- there's al widths of tire- I have a 32mm on the front and a 35mm on the back with a thorn proof tube- All very lightweight and roll great!
dance1
 
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happycheapskate

happycheapskate

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I have been riding this setup some more (26" wheels, coaster HI STOP hub, 36t sprocket, 50cc china). I think you are right that this bike will not pull with the 20t. It might work with skinny tires and multi speed pedal assist, but would die on the hills. The 36t is working well though even for overpasses and small hills.

I have heard that these motor bicycles make the coaster hubs wear out fast. If that is so, I will replace it with a setup like yours. Does your idea allow for spacing the cog away from spokes for a 415 heavy duty chain? I am using the KMC Z chain now.

The tear-drop shaped spoke holes supposedly relieve stress on the spokes (Its called "chamfering". )

Chamfer - Wikipedia, the free encyclopedia
 
Nashville Kat

Nashville Kat

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Apr 20, 2009
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Jacksonville, Florida
It absolutley holds the sprocket away from the spokes without even touching them- outside of losing the weight of the whole rag assembly and three bolts- that's the best part- no wobble, arrow straight, no pressure on the spokes

The only clearance issues are ever on the frame stay side, because I don't use tensioners- just half links- and I try to space the hub on the axle with washers a little bit toward the center and away from the frame chain stay
 
happycheapskate

happycheapskate

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I have come up with a reliable tensioner for bikes like that. It just takes up about 1/2 link worth of tension, and prevents the vibration from the engine drive cog soaking into the frame. VM for info.
http://motorbicycling.com/members/h...-picture399-i-am-using-long-metric-screw.html

I solved my clearance issue on the left side, during the original build, by cold working the stays apart just enough for a couple extra washers. The smaller drive cog also helps.
 
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Nashville Kat

Nashville Kat

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Apr 20, 2009
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Jacksonville, Florida
Here's the finished build-

This is a fun little bike- it's not as powerful as my other, but it's lightweight and goes up and down the apartment stairs easier- a nice little cruise that I really don't much care to go faster than on the short trips I most use the motor for.

I'm putting some alloy BMX bars on as soon as I get the fixed grip off, just so I have a little more angle if anybody pulls out and I take a header-

I'm also replacing the front QR skewer with a solid bolt on axle- it will be safer- the bolts have less chance of breaking and the slid axle is longer and leaves axle under the fork ends ....

Finding the right races has been annoying on such an axle swap in the past, but the asians on ebay seem to have a more compatible cone on the solid axle, without the attached dust cap....
 

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Nashville Kat

Nashville Kat

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Apr 20, 2009
1,501
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Jacksonville, Florida
I may eventually change the sprocket- I have this GT 39 t alloy Sprocket-

the center hole would have to be drilled or ground wider and the 6 holes drilled for the flip/flop- if you look closely you can see I've already marked it-

I'd gain 2 teeth down from the red 41, and the GT is alloy (but thick, 1/8"- plenty strong I think),

and the GT weighs almost nothing!

But not for awhile- the motors still breaking in- I don't think I'd try a 36 on this 50 cc.

I did this image on my scanner- ha!
The others are my humble and junky abode...
 

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Andyinchville1

Andyinchville1

Manufacturer/Dealer
Dec 26, 2007
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HI,

FWIW our Super Sprockets are predrilled for the 6 bolt ISO mounting pattern also....AND are available in 9 anodized colors....

I like your colors!

Andrew
 
Nashville Kat

Nashville Kat

Well-Known Member
Apr 20, 2009
1,501
55
48
Jacksonville, Florida
Actually you don't even NEED a flip/flop to do this mount- just a LARGE FLANGE:

Here's one on ebay, but ending soon for $18 SHIPPED!
http://cgi.ebay.com/Alloy-Hub-Large...Cycling_Parts_Accessories&hash=item588c2fec71

All you need is a flat metal file- build the wheel and put it on the bike- hold the file on that hub- it only needs a little filing to get a sprocket over the other side- Turn the bike over, just turn the pedals and the file grinds a nice liitle ridge stop for the sprocket wherever you want it-

the alloy grinds real easy, and allyou need is to file it to the same diameter as the threads on the other side- the bike itself makes a great grinding wheel.

then just drill the holes in the hub and/or sprocket-

boygofast and luckyyearlybird on ebay also sell sprockets with the six drillings for the same normal price but you have to query them and specify.

If you want to eliminate the rag and keep the sprocket off the spokes that is.
 
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