Following up on Erics' 3-spd.
1978 Sturmey Archer S3C 3-spd coaster. I have always had some trouble with Sturmey Archer coaster-3's and this particular one is problematic. I have gone down hard on a number of occasions with this evil piece of steel. I was once standing up over the bars in 3rd fully powered up and it let go. I had a concusion and multiple nasty injuries. That was one time. There have been others.
This hub slips out of 3rd when casually pedaling along. Happens about every 25 pedal strokes. I suspected spring tension on the pawls, the ratchet notches being worn or debris-laden, or the main drive clutch "creeping" off of the planetary drive pins when in 3rd.(return spring tension?) So here we go again. I hate starting this process but delved into it today..ugh..
After removing the wheel, I pulled all the fixing nuts and hardware off both sides of the axle and then removed the brake assembly unscrewing the main notched play adjustment nut. It all should slide right out with little help.
Then the drive side main axle cone is removed and the sprocket carrier can slide off the axle.
Remove the rest of the drive guts by unscrewing the threaded ball carrier with a punch and hammer. Lefty loose. I have had this stupid hub apart alot so this went pretty easy. Do not tighten this too much or you will never get it back off....proper tool would be best to unscrew it...
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Now you can pull out the rest of the internals out. Clean everything with solvent and a soft brush and set it aside. Everything...
Now is always a good time to clean the hub shell with an old toothbrush and mineral spirits. I like to clean the spoke/hub flange areas and the rest of the empty shell and set that aside for the rebuild. Really hard to do so otherwise sitting in the frame...
This hub is beginning to see some pitting on the hubs' drive side race...
After cleaning and inspecting everything, I find nothing suspect...see the sprung pawls and the 4 planetary drive pins below. Looks ok, right?
After cleaning and inspecting it all, time to re-assemble! Make sure when cleaning with a brush, to not dislodge & lose the weak and poorly-designed pawl springs which can and do easily break. Notice I bent them a bit to put more tension on the pawls, which I had suspected could be allowing the pawls to slip out of the hub shell notches. I don't think this is the problem with the slipping 3rd gear//
You then basically re-assemble the guts in the reverse order drive-side1st. Assemble the axle with the planetary carrier and all the drive side guts together and thread the whole assembly into the hub shell. The outside cone that you see now screwed onto the axle before screwing it into the shell temporarily helps hold the drive clutch in place as it always wants to slip off the axle and fall on the floor during the next steps. It is always better to assemble the entire package completely including the sprocket carrier with the drive side axle cone buried to the thread stops, and then screw it all assembled and seated together into the shell..this always seems to work the best as all the parts seem to assemble and seat better outside of the shell....If you try to put the sprocket carrier in after the assembly is screwed into the hub shell, it can be a nightmare to do it but it still can be done. Just more potential for all the parts to not seat properly and make your life miserable...
If you lose the indicator chains' sliding gear adjuster shown below, you can not and will not recover.!!! This dimunitive and easy-to-lose piece that slides in the axle that the indicator chain screws into allows you to shift, and without it good luck...it becomes a fixed gear hub....
Here is a look at the planetary axle/drive pin ends with the 4-arm drive clutch in the 3rd gear position resting against them. This is before I assembled it all and screwed it into the shell. I believe this is where the weakest point in the s3c hub is...the square armed drive clutch slowly creeps off of the ends of the pins when loaded, even with spring tension pushing the clutch down in place as you see it...
At this point, the trickery begins. If you 1st seat the driver as shown and then screw the cone on, the spring cap under the cone that you can see binds on the bearings and delicate pawls inside not allowing anything to seat or slide properly internally. No Bueno. Not all sturmeys are like this. Seat the main axle cone into the driver 1st, then carefully screw them onto the axle while holding them together seated, keeping the return spring with its' cap UNDER the bearings and sprocket carrier while doing so...very tricky. This drive side cone MUST be tightened to the end of it's threads. After you think you have done this, spin the wheel back and forth and continue to attempt to screw the cone in further. Very difficult to seat the internals during this process. I like to screw in the indicator chain and pull it in and out while spinning the wheel, occasionally checking if the cone screws further in...it always seems to have further to go. If this drive side cone is not buried as tight as it will go until it stops on the axle threads you are doomed.
So once the drive side cone is to the end of the axle threads screwed all the way in and stopped, go to the brake side of the hub. See below the ends of the planetary drive pins sticking out with flats on them...if the flats are not all cleaning pointing to the outside of the shell, you cannot assemble it correctly...make sure of this.
The rest of the brake side internals are relatively simple to install. Make sure everything seats well as you go along..Note below the location of the spring. If not in this position, the rest will not go together properly..
Install the anti-rotation washer then the notched bearing adjustment nut. This nut is the ONLY nut to use to adjust the hubs bearing play. When assembled and tightened in the drops, there should be zero play at the rim and a small amount at the sprocket....it should spin freely and not bind anywhere, or in any way and should not ghost-drive the cranks when free-spinning the wheel. If anything binds, you are screwed and have to start over...
When you are sure the drive-side cone is fully screwed in to the furthest extent possible, back it out 1.25 turns and put the lock tabs in place on its' flats. Then tighten the non-drive side threaded & notched adjustment nut until the whole mess has no play...spin the wheel in your hands working everything back and forth, the sprocket carrier and the brake action, watching for any play or looseness. If so, not good. Assuming there is no play and things look like they are working, insert the indictor chain all the way in (threaded-end shifter chain inside the axle) then back it out one turn... I also like to run these extra lock tabs pointing outboard on my 3-spd hubs as they really help keep the axle from shifting in the frames' dropouts under power. Anti-rotation axle security as well.
Some highlight pics below.....
Taking the play out at the rim using the notched adjustment nut on the brake side(below)while mounted in the frame, drive side nut tight. Tighten the left side axle nut down again after adjusting and check for any play at the rim...there should be
none... The wheel should also spin freely with no binding or noise, and the crank should not move while the wheel spins. This is what you are looking for, smooth spin and nothing binding. Attach the shift cable, adjust correctly and go ride it...
So after all of this long-winded, lengthly and detailed rebuild, do you think I solved the slipping out of 3rd gear problem?
NO!...it still slips out of 3rd while lightly pedaling at around 20 turns. I hate sturmey hubs and may never lace one up again....