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Modern custom Ultra-9 freewheel build.

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Modern custom Ultra-9 freewheel build.

Old 02-23-24, 06:46 PM
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Modern custom Ultra-9 freewheel build.

Freewheels are alive and well in 2023!

Having noticed that freewheels with ever greater numbers of speeds have become available for E-bikes, I began to ponder modifying one of them to a narrower width by deleting the smallest cog and shortening the body.

My first effort, a few short years ago, started with a Sunrace 10s freewheel, but the body had two problems (one was a design defect).
Firstly, there was a plastic sealing ring that was in the way of tightening the freewheel on the hub all the way, the seal getting pinched so as to prevent reverse rotation.
I simply couldn't believe that such a defect made it into production, so I sent the freewheel back. It also had a visible gross spacing error between two of the smaller cogs, looking like a 6-speed spacer got thrown in!
The freewheel also weighed a proverbial ton, it was an 11-34t if I recall, and positioned the largest cog none too close to the spokes as would be needed to arrive at a decently-short driveside axle extension (modern 10s road cassettes all feature such offset, and larger-diameter largest cogs increase clearance to the canted driveside spokes, allowing further offset).

So while the first freewheel was rubbish, other makers have since appeared (with 7- through 11-speed offerings) and at really low prices, well less than half of what the defective Sunrace freewheel cost on Ebay.

I recently bought two ten-speed freewheels (11-32t and 11-36t) off of Ali Express, made by VG Sports.
First thing that caught my eye was the offset largest sprocket, critical for arriving at a narrower driveside freewheel axle extension, for both wheel dish and axle strength considerations.
Right out of the bag, this 11-36t freewheel looked really good. No lightweight, but nothing "clunky" about it and still lighter than the Sunrace.
I easily removed the steel lockring (which looked identical to an HG cassette lockring, but is actually a millimeter or two smaller on all of it's critical diameters).
I simply used a curved-jaw locking plier to grip the smooth edge of the 2mm-thick flange (slightly ovalizing it in the process but easily corrected by squeezing it again).

Measuring everything up, I saw that I first needed to remove the smallest 11t cog with integral spacer, about 5mm thick.
I then needed to shorten the freewheel outer body a few millimeters (to 33.5mm overall thickness) using a bench grinder and large wet sanding block to arrive at a perfectly square end surface.
Finally, I needed to make a washer, since the OD of the lockring flange was a bit to small to support the #2 13t cog's splined ID (I simply modified the ID of a 1.2mm-thick 1-1/8" headset washer).
The end threads on the lock ring also needed beveling to allow the lockring to go far enough into the now-shortened body (the internal threads only went in so far).

Since the 2nd cog and washer had no mating knurling teeth, I used Loctite on the threads to prevent loosening. And I gripped the lockring flange at different positions during tightening using the locking pliers, helping to settle the threads fully without re-ovalising the lockring (no, an HG lockring tool doesn't fit this lockring).
I also filed away the lockring's knurling, to reduce the installed height. With the washer in place, the lockring extends only 3mm beyond the face of the smallest 13t cog (it should nearly graze the frame and still provide plenty of chain clearance).

The now-smallest 13t cog mates to the very end of the splines, but engages it's entire thickness steel-on-steel for reliability.

While the cog stack is wider than any 7-speed cassette or freewheel, this freewheel is no wider on the hub, as installed, than 7s freewheels.
This is due to it's offset largest cog actually overhanging the inner body seating surface by about 1mm, instead of stacking that same one millimeter proud of the seating surface as on 7s freewheels.

So it's a success, and cost me only about $25 and a couple/few hours (a lot of test-fitting arriving at the 33.5mm overall width). Glad I bought two!
These freewheels should be very strong, as they are rated for Ebike use.









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Old 02-23-24, 06:56 PM
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Interesting idea. At the co-op, we get customers who bring in bikes & wheels with lots of added washers/spaces and broken axles - and 9-10 speed freewheels they get on eBay or Amazon or salvaged. Have to explain that even though the threading is the same, these freewheels really only work with super-thick e-bike axles able to handle the added bending moment.
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Old 02-23-24, 07:49 PM
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7+ speed freewheels are the blight of my existence. At the Co-op we see at least one broken or badly bent axle per shift. When the rider first notices something funny is going on at the back of the bike, it is usually too late and the bearings, cones and rear axle itself is a mangled mess of metal shards.

7-speed freewheels are marginal on bikes with 10mm rear axles, and a light careful rider. But on mountain bikes, e-bikes and tandems(!), unless the rear hub axle is specially designed and super strong, it is just a matter of time... In January we worked on a tandem with a 10mm rear threaded axle and a freewheel. Seriously. Both of the riders were light, but it maybe lasted 100 miles before breaking.
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Old 02-23-24, 07:56 PM
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Verrrrrry interesting tinkering. Love the name, Ultra-9

Any comments to how well the freewheel spins? And what bike are you planning to put this on? Some 126mm aluminum or carbon frame?
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Old 02-23-24, 08:03 PM
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Ingenuity at its best!
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Old 02-23-24, 08:44 PM
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Originally Posted by Dave Mayer
7+ speed freewheels are the blight of my existence. At the Co-op we see at least one broken or badly bent axle per shift. When the rider first notices something funny is going on at the back of the bike, it is usually too late and the bearings, cones and rear axle itself is a mangled mess of metal shards.

7-speed freewheels are marginal on bikes with 10mm rear axles, and a light careful rider. But on mountain bikes, e-bikes and tandems(!), unless the rear hub axle is specially designed and super strong, it is just a matter of time... In January we worked on a tandem with a 10mm rear threaded axle and a freewheel. Seriously. Both of the riders were light, but it maybe lasted 100 miles before breaking.
My first MTB was a 1990 Giant Iguana with a 7 speed freewheel. Jumped it a bunch. Nothing happened.
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Old 02-23-24, 09:04 PM
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Thanks for the comments, I too find lots of bent, even broken axles on the bikes I work on.

Prior to this project, I've always re-done the axle spacing on most bikes that I ride.
Seems like the factories didn't understand or care that a modern 8s chain only needs 3.3mm from the face of the smallest cog out to the dropout. Even 7s freehubs all seem to be waiting for at least 1mm to be removed from the driveside, and many 5s bikes have all but perhaps 1mm of needed extra axle spacing to utilize a standard-spaced 6s FW.

I've used solid (i.e. nutted) 10mm axles on hard-ridden MTB's together with 7s freewheels and minimal (3.3mm) chain clearance spacing, no bent or broken axles to date!

The freewheel spins nice with no discernible play. I plan to use these freewheels on 126mm 7s freewheel-hub wheels that might interchange with my 10s-fitted 7s cassette hubs, bikes already having indexed 10s gearing retrofitted.

I just followed up by test-fitting a bunch of freewheels on various 6s and 7s hubs, to see what width penalty might be imposed.
I incorrectly stated that the installed width (out to the smallest cog) was the same as 7s freewheels. The cog stack is about 4mm wider than a 7s freewheel, and the installed width of the modified freewheel was actually about 1mm wider than most 7s freewheels, ranging from .7mm wider than Sunrace and 1.4mm wider than Dura-Ace 7s or Suntour 7s.
But most 6- and 7-s hubs have a lot more than the required 3mm of redundant added chain clearance space from the face of the smallest cog out to the dropout, so my modified freewheel actually fit on the first old 6s hub that I tried it on!

It is satisfying having my second try at Ultra-9 go so well, especially at such a lower cost.
And it might be nice to be rockin' a tight-enough 13-36t range on, say, a Nuovo Record hub.
Ratios are a sensible 13-15-17-19-21-24-28-32-36.
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Old 02-24-24, 11:00 AM
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Originally Posted by dddd
These freewheels should be very strong, as they are rated for Ebike use.
IME, the issue with freewheels having more than seven sprockets is not the strength of the freewheel, but a propensity to axle breakage due to the longer unsupported length of axle needed to provide the space needed for all those sprockets. Modern freehub systems avoid this by incorporating the ratchet mechanism into the hub, which allows the drive side bearing to be located much closer to the dropout, resulting in less unsupported axle between the bearing and the dropout.
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Old 02-24-24, 11:32 AM
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This is similar to the idea I have had in my head of a freehub body that threads onto a freewheel hub.

I like the "stepped" cassette here. On most cassettes nowadays, the largest cogs are on a separate spider that (conceivably) could be mated to a larger diameter spider that would interface with the larger diameter freehub body (necessary to fit over the hub threads).

But like everyone here is saying, the main feature of a cassette hub I would want to incorporate is a set of bearings at the outside end of the freehub to put less strain on the axle. If you can incorporate that then I think we're in business. I too would love to mate an 8/9/10 speed cassette to a classic NR hub.
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Old 02-24-24, 12:57 PM
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Do You Take Requests?

Originally Posted by dddd
... I plan to use these freewheels on 126mm 7s freewheel-hub wheels that might interchange with my 10s-fitted 7s cassette hubs, bikes already having indexed 10s gearing retrofitted.
....
Thank you for sharing your experiments! Enjoyed, learned and benefit from your 10v on 126 spaced 7v hubs, and have applied it with those more deeply threaded Temu "freewheel covers."

This freewheel mod presents an opportunity, perhaps, for a wider gearing on 120 Phil hubs, of which a couple few are lying around waiting to be pressed into service.

Could you please try out your modded freewheel on a 120 hub and bike if you happen to have those handy?

Thanks! Keep up the Interesting and Imaginative Work!
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Old 02-24-24, 01:18 PM
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Originally Posted by Dave Mayer
7+ speed freewheels are the blight of my existence. At the Co-op we see at least one broken or badly bent axle per shift. When the rider first notices something funny is going on at the back of the bike, it is usually too late and the bearings, cones and rear axle itself is a mangled mess of metal shards.
Ouch that's a lot of busted freewheel setups.

I tell folks avoid them unless the hub is Gucci boutique. Me, across the country and down the coast and years of crappy commuting on a 135mm dishless phil wood hub and freewheel combination. STILL TICKED 6 years later the bike was stolen just because of that hub. Touring weight 255-280 lbs.
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Old 02-24-24, 02:09 PM
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A solid 10mm axle does expand the boundaries of load limits of whatever combination of freewheel and unsupported axle length one happens to be wanting to use.

On my Huffy "mid-fat" mtb I found that the bike in the store already had a bent rear axle as the box was likely dropped on it's end in shipping.
I removed the solid 3/8" (9.5mm) axle and found that the driveside bearing cup had also become quite loose (radially) in the hubshell, no doubt from the same impact.
I was able to secure the loose bearing cup in the steel hubshell using red Loctite, which has lasted for years (I was sent a free replacement wheel, still unused, under warranty).
And I had in my stash some identical cones (having integral dust shields) sourced from some JoyTech QR hub having a hollow 10mm axle, so am now running a 185mm (tandem-length) nutted 10mm solid rear axle with no problems. I carry a slightly enlarged (to 15mm) 4" adjustable wrench for wheel removal and keep the threads and captive washers well-oiled.
Even wing nuts secure a solid axle quite well, again if the threads and captive washers are kept lubricated.

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Old 02-24-24, 02:30 PM
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Originally Posted by machinist42
Thank you for sharing your experiments! Enjoyed, learned and benefit from your 10v on 126 spaced 7v hubs, and have applied it with those more deeply threaded Temu "freewheel covers."

This freewheel mod presents an opportunity, perhaps, for a wider gearing on 120 Phil hubs, of which a couple few are lying around waiting to be pressed into service.

Could you please try out your modded freewheel on a 120 hub and bike if you happen to have those handy?

Thanks! Keep up the Interesting and Imaginative Work!

Good to know that you so quickly found and utilized the Temu alloy lockrings that I had raved about!

This modded freewheel won't likely fit on a traditional 5s Phil freewheel hub though. I have two such hubs and was only able to fit an "Ultra-6" (built on a Dura-Ace 7s body) freewheel on one of them, the other one I made up a 13-24t Uniglide 5s freewheel for, to use on my Steyr Clubman.
Increasing the length of the driveside axle extension could allow use on any freewheel hub however.

Again, I test-fitted this modified freewheel on an un-modified 6s Maillard freewheel hub off of a 1989 Cannondale mtb and it fit with a sufficient 3+mm chain clearance from the face of the smallest cog to the face of the axle locknut.
A 10s chain needs no more than 2.8mm clearance!

I may decide to upgrade the 7s Huffy MTB to this U-9 freewheel. I would need some 10s shifters, or perhaps 9s shifters with some kind of alternate derailer or cable-anchoring configuration to arrive at correct indexing actuation. Stay tuned.
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Old 02-26-24, 07:16 AM
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Originally Posted by Dave Mayer
7+ speed freewheels are the blight of my existence. At the Co-op we see at least one broken or badly bent axle per shift. When the rider first notices something funny is going on at the back of the bike, it is usually too late and the bearings, cones and rear axle itself is a mangled mess of metal shards.

7-speed freewheels are marginal on bikes with 10mm rear axles, and a light careful rider. But on mountain bikes, e-bikes and tandems(!), unless the rear hub axle is specially designed and super strong, it is just a matter of time... In January we worked on a tandem with a 10mm rear threaded axle and a freewheel. Seriously. Both of the riders were light, but it maybe lasted 100 miles before breaking.
Outrigger bearings can help here. A 10x20x5 works for 10 mm axles and SunTour Winner Pro freewheel with no bearing adaptation. These seem to provide sufficient support to greatly reduce bending and breakage.
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Old 02-26-24, 10:40 AM
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it's not just the length of the axle with 7,8, or more speeeds on a freewheel hub.

The drive side hub bearing is essentially in the middle of the axle !

that is why they bend. I cannot think of a way around this problem - except to go to a freehub / cassette architecture

/markp
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Old 02-26-24, 10:52 AM
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The outrigger bearing sits in the freewheel shell outboard of the DS hub bearing.
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Old 02-26-24, 04:02 PM
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Originally Posted by mpetry912
it's not just the length of the axle with 7,8, or more speeeds on a freewheel hub.

The drive side hub bearing is essentially in the middle of the axle !

that is why they bend. I cannot think of a way around this problem - except to go to a freehub / cassette architecture

/markp
Or run a freewheel hub with oversized axles like the Phil Wood, American Classic, Bullseye, Mavic 5**, etc.
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Old 02-26-24, 05:58 PM
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Originally Posted by esasjl
Outrigger bearings can help here. A 10x20x5 works for 10 mm axles and SunTour Winner Pro freewheel with no bearing adaptation. These seem to provide sufficient support to greatly reduce bending and breakage.
Wow, this is exactly what I have been pondering!

Would this be heavier or lighter than getting an appropriately sized reinforced axle for an 8 speed freewheel I wonder?

The dream is to have a stepped freehub body that threads on freewheel threads, takes standard cassette cogs (maybe with a custom spider for the largest cogs) and has outboard bearings like this.

Maybe it's time to tinker. I don't really care to have more than eight speeds, but having the cogs be much more replaceable than freehub sprockets (and easier to replace too) would bring some new life to some nice old hubs for me. Not sure if there would be any weight saving as well.
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