Reverse threaded freewheel?

[Mainer]

Hi All,

I'm new here. Has anyone out there heard of this? A adapter that would allow mounting a reverse BMX freewheel (also called Lefty or Southpaw) to an ISO 6 bolt hub? I'm trying to drive the left side of a Nuvinci hub with a geared motor. No need to run a disc brake in conjunction with the freewheel. Just to be clear, the threading would be standard 1.37 x 24 but left hand threaded...

Any help would be appreciated.

Best,

Davis

 

[Thud]

I haven't come accros one of those yet....its going to be a custom part I suspect.

What kind of center hole clearance do you need to fit flat onto the hub? I suspect there may be an issue with having enough material for the threaded section & still have it resting flat on the mounting surface.

I know my shimano disc hubs need 1.25" of center hole in the pattern to clear the end of the dust seal section. It wouldn't work in that situation without spacing it off the mounting face. Then there are clearance issues maintaing 135mm drop out spacing.

Nothing is impossible but if it was easy, it would be no fun.
Let us know what you find.

 

[Miles]

Looks like about 32mm dia. clearance is needed at the mating surface. You'd need at least 3mm thickness for the bolt heads, so it would be ok within that. Bolt head diameter encroaches on the 1.37" thread OD, though.... Not to mention that there isn't the needed 19mm min. clearance to the frame.....

 

[drewjet]

I am curious as to why would you want to drive the left side of the Nuvinci with a motor? The left side doesn't run through the gearing but would directly drive the wheel, 1:1. That would leave just the pedals for the driving right side and making use of the gearing, the nuvinci is kinda heavy for that aplication IMO.

 

[Miles]

At least you wouldn't waste 20% of the motor's power

 

[Mainer]

Thanks for the info.

Luckily I'm not limited to 135 mm dropout spacing on the frame, so I was hoping to squeeze out a few mm. of extra clearance that way. Countersinking the bolt holes and using 5 mm stainless flat head bolts would hopefully take care of the bolt head interference problem.

I'm planning to use a geared 48V 1000W motor as a supplemental drive. My thinking is that there would be very little drag when the motor is not being used. I thought about a system like the King Top hat adapter (using a fixed sprocket) , but I was trying to avoid the extra drag and noise of the left side drive chain always rotating...

This is for a pedal/electric cargo trike, so weight is not super critical..

Best,

Davis

 

[Mainer]

Oops. Guess I missed the meaning of the bolt head diameter encroaching on the threaded section......good point. I may have to consider using the smaller metric version of the freewheel (30.0 x 1.0)

 

[Miles]

You got it.

You could lose a bit off the countersunk head diameter and counterbore the holes a bit. Nominal OD for M5 head is 11mm, I think.

You can certainly get the 14t freewheel in 30mm x 1mm. You'll have to watch the internal bore clearance for that.

Maybe Staton could make you up something?
http://www.staton-inc.com/store/products/14_tooth_Freewheel_Sprocket_with_30_mm_x_1_0_mm_SouthPaw_LEFT_HAND_Thread-1216-50.html

Countersunk holes for unmodified M5 countersink head bolts - 1.37" thread :

 

[MattyCiii]

The N360 has three types of left side adapters for brakes - they're removable. See page 5 of the parts catalog. Maybe you can have a custom left side adapter machined that mates with the NuVinci and has the left 1 3/8" thread, skipping the disc brake mounts. Then the horizontal clearance will be less of an issue.

 

[Miles]

Maybe you can have a custom left side adapter machined that mates with the NuVinci and has the left 1 3/8" thread, skipping the disc brake mounts.

That looks doable. Machine the edge of the adaptor to fit their retaining ring.

 

[MattyCiii]

Also, I did a quick Google search (set results to "images") and I found this:

So it;s been done before, and maybe someone who has done one has a small stock for sale?

 

[amberwolf]

If you already have a lefty-threaded rear hub, you could also cut it's left side spoke flange and threaded section off, and drill it out for the disc bolt holes, removing the bearing cup from it.

I did this with right-hand thread and on the rightside of a front hub motro to turn it into a rear:
http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=37837
so it should be possible to do the same thing for the above.

 

[Mainer]

Some great ideas. I'm using the older Nuvinci, not the N360, but from what I've heard, the N360 seems better/lighter, and more importantly, easier to adapt. I sense an upgrade in my future...

I did actually contact Jeff ( Monkeylikesshiny)The one he built was right threaded for a gravity bike. It looks like it could be done with reverse threads...

I'll get an N360 hub, as well as the tool, and let you know how it turns out...

Thanks for all your help.

 

[MattyCiii]

This thread from 2010 has some great discussion of this topic - related to a N170/N171 NuVinci.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=18232&start=15#p266798