sloar 

I’m unfamiliar with this freewheel, what can you tell me about it? Thanks

beicster 

That looks like a freehub to me.Does the bit sticking out of the hub have flats to fit a hex key?

sloar 

No.

more pics, am I missing something here? I’ve never seen this before.

sloar 

The freewheel has a bearing race with this cover over it.

sloar 

Better pic of the hub, it’s solid and doesn’t come out.

rccardr 

Looks like a freehub to me. Reinstall and remove outer cog, will require two chain whips.

scarlson 

Yeah that's an early freehub. The smallest one unscrews as rccardr says, with two chain whips. Cogs after the smallest ones are splined onto that body. IIRC, the earliest freehubs didn't have the big 10mm allen bolt holding them on - they were just held on by the axle and the bearings. Neat to see one like that close up! The machining of that splined boss on the end of the hub is interesting.

sloar 

I’ve never had a freewheel just fall off before when I removed the axel.

Jeff Wills

It’s a first-generation Shimano Uniglide cassette hub. The freehub body presses onto the snout of the hub and is held in place by friction and the axle and bearings.

If you want to remove the cogs, you’ll need to unscrew the smallest cog. You’ll need two chainwhips or a chainwhip and a freewheel vise.

If the cassette body and cogs slipped easily off the hub, the hub’s snout is probably worn or distorted. If that’s the case your best path forward is rebuilding the wheel and replacing the hub. This hub is 40 years old and spare parts weren’t widely available back then.

pastorbobnlnh 

The teeth on the sprockets appear to be very worn and not worth saving. I'm guessing the connecting screw broke or unthreaded and fell out, allowing the freehub to disconnect from the hub body. I doubt there are any parts worth salvaging, except the sprocket spacers. Just my two cents.

scarlson 

I don't think there was a screw. See Sheldon's page (linked below). The axle retains things on its own. There are photos looking exactly like what's going on in the pictures in this thread.

Probably true that things may not be worth salvaging, unfortunately, unless sloar can find some more UG cogs or has a wear-matched chain and doesn't mind using it.

It's the freehub body that fell off. See the previously-linked Sheldon Brown page: https://sheldonbrown.com/k7.html#uniglide-old
Your hub looks exactly like the ones on Sheldon's page. Very bottom of the page. Here's a quote:
"The earliest Shimano Freehubs, however, used a more primitive construction. There was a set of splines to keep the body from rotating on the hub shell, but instead of a hollow bolt to secure the body to the shell, there was a smooth cylindrical projection past the splines, and the corresponding Freehub body was a slip fit over this projection. The axle held the assembly from falling off, but the design was not fully satisfactory. The Freehub body could burnish the projecting sleeve, and loosen."

You just have to remove the axle and bobs yer uncle, the freehub cassette body falls right off.

dddd

I've had these loosen but not fall off, because there was swaging on the end of the snout of the hubshell which still held the freehub body on.

It made for some difficulty assessing the bearing tension adjustment, which had to be evaluated after the QR lever applied it's tension.

The easy fix for this one is to clean the surfaces and put the freehub body back on, slowly, using Loctite. Might as well use the green penetrating grade or the red, it would be even more permanent than the factory swaging (with the weak interference fit between the snout and the inner freehub body).

This looks like the Model 60 freehub that so often came on otherwise 600 equipped bikes like the Bianchi Super from 1979-1980.

It's a good hub if the smallest cog isn't worn out, that's becoming hard to find but the rest of the cogs could come from an HG cassette with each cog's positioning spline shortened using a chainsaw file.