pstock

my GoTo local bike diagnostician is closed today so I am going to toss another problem up here I'm afraid.

I am rehabbing a cheap 8S City bike that has been left out in the elements it seems.

the wheels are cheap but decent and clean BUT the rear Freehub is not engaging under load
the pawls click nicely when freewheeling but it just slips when under load.

I have soaked and lubed the FH body as best I could.

what could be going on here? (I am not even sure now that I think about it where the "Grab" comes from when a FH is under load.)
is this just a Toss and Replace situation?

peter

alcjphil

Looks to me as if the free hub threads into the hub shell. If those threads are stripped, the hub is toast

pstock

yes. on closer inspection (with some local expert eyes) I'm told the part of the FH that attaches to the hub has snapped off. hence the no Grab.
sorry to bother you all.

soyabean

If this wheel is a total loss, I'd weld the FH to the hub.

Worth to do if you own a welder (I do).

Otherwise toss it.

Andrew R Stewart 

The two usual methods to secure loose balled (as in no cartridge bearings) FHB to the hub shell is with a hollow bolt that is removed from the LH hub side or having a FHB with s threaded stud (again hollow for the axle to pass through). If the later and that stub broke off it should be easy to view the raw fracture face on both, the still in the shell stud and the FHB back side.

Now finding a replacement will be the challenge. Were this mine I might call it a day, save the axle parts and tossed the rest then find a replacement wheel. Or find a used hub and relace that into the current rim. Andy

I forgot to add that I'd love to see how the Al shell and steel body get welded together

soyabean

Pull the axle and bearings out, plenty of room from the inside.

You can even grind slits into the hub just to access the contact points from the outside.

Like doing a dental amalgam that's in-between the teeth. You gotta drill top-down good enamel to get to the cavity.

FBinNY 

I define 2 classes of freehub body
The Shimano type affixed to the hub. the clutch entirely within, and those like Campy, with the clutch between the body and hub shell.

I consider the Shimano style as unserviceable other than the soak and pray method. Those with clutches between body and shell are different and sometimes can be serviced with replacement springs or other parts.

grumpus

Does it weld steel to aluminium?

Duragrouch

Sounds like the fixing bolt that holds the freehub to the hub may have loosened, causing bending loads. But could have just failed due to bending loads without loosening. If you can remove the part on the hub side (should be a close slip fit, not press fit), you should be able to simply replace the freehub, 8s shimano style (and widely available generic) are pretty cheap. Key is to make sure you get the exact correct style of freehub body, the interface with hub varies.

Bill Kapaun

Like this?

Duragrouch

Interesting. Pressure bonded like tri-ply cookware? Or actually melty interface?

At least several decades ago, there became available heavy truck bumpers that were stainless-steel-clad aluminum, stays pretty, saves weight.

grumpus

I'm pretty sure a conventional welder can't do explosion cladding. Or are you suggesting we should use a bimetal layer to "fix" the freehub? 😁

FBinNY 

If so, I suspect the broken off stud was threaded into the shell. With a bit of luck, you might get it out with an EZ out. Then a new freehub body can save the wheel.

Note: a decent amount of torque will be needed, so the EZ out goes into a vise, and you turn the wheel.

pstock

Thank you.
Yes, while all the instructions I read called for a 10mm it took a 12mm inserted from the NDS to extract the threaded stump (I expect this is a non-standard FH to need 12mm)
But At my local DIY Bike Repair Coop I went through their bin of about 30 salvaged FHs and while there were two which looked to be about the same design as my busted one (similar diameter and threaded stud) neither would thread into this hub.
Both when about 1x turn and then jammed, as if the thread pitch was different.
I have no idea where I would find a compatible replacement.
maybe I can replace the entire hub and rebuild the wheel? (I have been wanting to try my hand at wheel building)

zacster

Since the rest of the wheel looks clean you could probably replace the hub and rebuild it in place, meaning you transfer the spokes from one hub to the other and follow the pattern, one spoke at a time. It would require a hub with the same spoke hole spacing to do this. Once all the spokes are transferred you tension it as you would with any other wheel. I did this once when I first built a rear wheel on the original 7sp hub, but then decided I really wanted a 10sp hub so I could run all 10 cogs. It went from one LX hub to the newer LX hub and they hadn't changed the spoke hole spacing. I had only used it a few times with the 7sp hub, the rim and spokes were otherwise new. It ran as a 9 of 10 cog cassette that way as only 9 cogs would fit although it was otherwise 10sp. This was almost 10 years ago and I still ride that wheel and it has never needed a retruing.

KCT1986

If you decide to rebuild, Sheldon Brown has a good writeup of wheelbuilding. Very worth a read if you haven't done so already. Includes step by step directions in the easy to read method. Can be found through the sticky on the Mechanic sub-forum. Park tool also has a good instructional post.

A suggestion is to change the head-in, head-out position from what you currently have on this wheel. See the diagram below. Your wheel has a symmetrical pattern (S1). Going to a mirrored pattern will make lacing easier. The directions on Sheldon's page will give you a M2 pattern, head-out for trailing (drive pulling) spokes. Sheldon's writeup discusses the head orientation towards the end. All patterns seems to work well for non-disk brake wheels, (subject to some controversy).