Can a flip-flop hub save my spokes?

[keysertomasi]

Hello,

So I've taken the plunge, ordered my Grubee SkyHawk 48 cc engine kit from bikeberry and have been reading up on what to expect. One thing that I've heard about is that the way that the rear sprocket is mounted to the wheel is by clamping it directly to the spokes using some metal pieces that connect to one anohter with 9 or so bolts. Basically, just a compression fit.

The issue is, that's a lot of stress on those spokes, in addition to what they're getting already from regular riding! I've busted a few spokes on my rear wheel this past year, had them fixed, and it was no big deal. But it seems like if I motorize my bike, the spokes will be the first to go.

So how about a flip flop hub? Is it possible to use a flip flop hub instead of the stock hub on my bike (a 2007 KHS Urban Xpress), and mount the rear sprocket for the engine drive to the "fixed" side of the hub? Has anyone out there tried this?

Thanks in advance.....

 

[Just_Gassit]

I know a guy that tried one. Was the main reason he selected the bike. As it worked out, it didn't work out. The engine tries to unscrew the sprocket as it is under power but also tightens it when you start the engine. It worked for the first few rides then stripped out the threads on the hub. He did use the lock ring on the hub too, looked like a case of just too much load that gets shifted back and fourth.

 

[keysertomasi]

Thanks for the info. I had heard that flip flop hubs have an opposite direction thread (left handed?), so running a engine will not cause it to become unscrewed. As a result I am a bit confused. Also, if I were to use a flip flop hub AND the clamping hardware to mount to the spokes, would this be enought reinforcement to keep the sprocket mounted and still not stress the spokes?

All suggestions welcome, thanks!

 

[ocscully]

Filp Flop hubs are right hand threads on both sides. There is a hub that has right hand threads on one side and Track threading on the other. Track threading is actually two sets of threads, a narrow width of normal right hand threads for the fixed cog and a smaller dia. narrow width set of left hand threads for the cog lock ring. I'm not sure if this type of hub is still called a flip flop or not but weather or not it is, neither of these types of hubs will work as a way to mount a driven sprocket on the left side of the wheel. A disc brake hub would work, by using the rotor mounting holes to mount your driven sprocket. Or You might want to look at the Grubee HD hub with the fixed sprocket. I would provide you with a link to the folks at bicycle-engines.com who sold the Grubee Hub but they seem to be out of them as they are not currently shown on their site. You might check with some of the other suppliers of Grubee 2-stroke kits to see if they have the HD Fixed Sprocket Hubs in stock. To save the spokes as you say, You have to get the sprocket mount off the spokes. You also might want to look at the Adapter made by Jim at Creative Engineering/Manic Mechanic. He makes a really sweet adapter that clamps to the center body of a rear hub and provides the mounting location for the driven sprocket Look for his ad on the bar at the right or left of this page. If you have a hub that is compatiable with his adapter, your problem will be solved

ocscully

 

[Nashville Kat]

A flip/flop hub would make the mounting easier- They have the same diameter on each side at the main section, as far as the diameter of the hub where a freewheel, a single fixed track cog, or our sprockets fit-
they usually have a freewheel on one side (with more axle spacing from side to side) and the track cog on the other side. On the outside of the track cog, is a set of threads of smaller diameter for the lock ring- and yes it is reverse left-hand thread-that will lock our sprocket on and not spin it loose- (A bottom bracket lockring is the same diameter as this)

Of course our sprockets just sit on the hub and don't thread- (What I'd like to find is a 34 or 36 tooth track cog--we'd be all set! But trackies usually don't ride gears that small.) Also generally, it appears that our sprockets are just a little more narrow than the track cog- so a spacer of some kind is needed- perhaps the rubber piece then- or perhaps a small (say a 14 tooth) track cog itself would work- if there is enough spacing for the lockring- and then the bolts for our sprocket to go through the high flange
I've wondered if a sprocket could be welded or driven somehow and attched to the side of a single track cog.

?????????????

So our sprockets don't thread down like the track cog but with a spacer, should be wedged and locked laterally by the reverse thread lockring-

I've inspected all this, but haven't yet actually done a build with a floppie- but I think it would be the best setup outside of a 36 track cog itself)

Then the only other factor is driving the sprocket forward with the chain and turning the wheel-

A LARGE FLANGE trackkie flip/flop seems the most ideal for the most efficient and lightweight mount- But you'd have to drill your sprocket to fit the usual openings in the large flange- Then (it appears) minimal nuts and bolts could be used to bolt your sprocket almost directly to the hub- WITHOUT getting anything on the spokes-

I've drilled a really light 34 tooth sprocket for the flanges on a Schwinn ten-speed Traveler I have- (See my thread here titled "Your bike is a grinding wheel"- I'll bump it up now- there's a picture of my hub and sprocket)

I'll put it here too-

A floppie is the best setup, but most older style alloy road hubs will easily grind down a little bit to accomodate our sprockets- and the large flange may be the best to bolt to with just rubber spacing instead of stressing the spokes. Just no lockring.

I'm also gonna bump my ancient thread on our need for a locking freewheel- which turns like a normal freewheel for freewheel pedalling, but then locks up to restart our motors

good luck!

 

[Nashville Kat]

This sprocket is drilled for the 8 flange openings in the old style schwinn hub- some vary, and some have NO holes in the flange and would need to be drilled there too

And I should mention that the center hole here has not yet been drilled for the hub- there won't be much clearnce then between that and these bolt holes- but I think enough.

This sprocket from bikeparts4you on ebay- $11 delivered)

But beware!

a small flange flip/flop or other hub would still require the usual ruber and bolting to the spokes-

this sprocket would be difficult to attach in the usual way

The hub in next post - won't download here?

 

[Nashville Kat]

Here's the hub, and the bike

I ground the hub with just a flat file-

by turning the bike upside down and pedalling it, and holding the file halfway on the spinning hub-

INCREDIBLY EASY!

If and when I build this bike- I'll probably take off the derailleurs and use a single frewheel on the bike chain side. I've got a narrow chain and motor sprocket ready too- and with a light 49cc, I'm projecting a final weight of about 37-38 lbs, withg these 27 X 1 1/4 alloy rim wheels.

I just put a 27" inch narrow 1 1/4" wheel on the front of my cruiser, and a Campy brake too. With the 26" X1.75 rear wheel still on (I may change that too, but maybe not) she REALLY ROLLS- very easy, and pedalling is approaching normal- The brake is GREAT- much better than cantilever- I'll take some pix and post here.