Sturmey CS RK-3 stripdown - a query - now solved

[Mick F]

Just had the rear wheel off to clean it then come in for a cuppa.

Checked the dead angles per freewheel click in 3rd gear. Difficult to be exact, but it seems that the rear cassette takes up the dead angle in about 20degs. Less than two sprocket teeth on the big sprocket 28t. Two teeth would have been 25.7degs, but it's less than that.
When I replace the wheel and SA gear changer, I'll check 2nd and 1st.

--------------------------------------
Cleaned the wheel. Not much extra lube on the LH side from when I cleaned it off the other day, but the RH side was oozing grease too.
Cassette off and cleaned it properly.

[Mick F]

When I replace the wheel and SA gear changer, I'll check 2nd and 1st.

Just checked.
One tooth of the 28t per engagement in both 1st and 2nd gears.
12.8degs

Maybe Brucey has some facts, and knows the number of teeth on the ratchets.
Not stripping my hub down (again!) to check.

[Brucey]

IIRC the current SA hubs have 20T ratchets. If the hub is set up badly (so that the wrong parts move when you freewheel or backpedal) then there can be additional backlash between the driver and the other parts in the hub. The driver uses a 10T ratchet onto the ring gear in gears 1 nd 2.

Obviously the gear ratio increases (in low gear) or decreases (in high gear) the apparent backlash by ~33% because of the effect of the gearing.

If you also have a low input gear (small chainring and large sprocket, schlumpf gear or w.h.y.) and/or a long floppy chain connected to the hub, you will have plenty of lash anyway.

In most cases (on normal bikes) you get used to a lot of lash in a transmission after a while, i.e. wind back the pedals to start and even when you resume pedalling you don't just stamp on the pedals, you take up the lash and then apply power. It is quite amusing if you see someone who is not used to this trying to pedal smoothly; lots of jerky pedal strokes until they get the hang of it. IME uphill starts on recumbents are not at all easy, regardless of the transmission used. I am sure it makes a difference what you use but what you are doing is difficult anyway; one thing you shouldn't do (regardless of transmission type) is to stop turning the pedals forwards, even momentarily. [Needless to say this is made somewhat easier by using clipless pedals because you can pedal forwards using one foot only if you have to.]

One way you can get a good push off is to select gear 2 in the hub for the first pedal stroke and then to immediately select gear one. Gear two may give a gear that is too high to climb on but gear one might give a gear that is too low for a good push off (with or without backlash) so the instant gearchange allowed in the hub give you a chance for a different strategy.

BTW there is less lash in gears 1 and 2 with a SRAM DD hub but this feature is (indirectly) also what makes the DD hubs quite likely to break. Swings and roundabouts.....

cheers

[UpWrong]

Thanks Mick and Brucey. After doing some static checks I have to admit that the engagement seems quick - Mick's calculations are about right. I tried all 3 gears and there wasn't an obvious difference. I shall ride it some more and see how I get on with it. I'm wondering if the short cranks (148mm) are making the take offs more difficult. Might try to find some 165mm cranks.

[Mick F]

I've been considering a modification ..............
..................... idea is to drill the hub shell and fit an oil/grease port like the SA hubs of old. Grease nipple perhaps.

Any comments on this idea?
Is it worth the effort?
If so, what should I fit?

[Brucey]

I've been considering a modification ..............
..................... idea is to drill the hub shell and fit an oil/grease port like the SA hubs of old. Grease nipple perhaps.

Any comments on this idea?
Is it worth the effort?
If so, what should I fit?

as long as you have a toggle chain to unscrew, and are planning to use SFG rather than oil, it is arguably better to introduce the lube via the hollow axle; th elube starts out in exactly the right place for it to work its way around the hub nicely.

cheers

[Mick F]

Yes, I'm aware of that idea, and you showed a grease-gun attachment thingy with a long thin nozzle.

Simplicity is the way forward methinks.
To insert a soft grease through the toggle side of the hub, you have to release the gear cable, unscrew the toggle and input the grease. Unless you can get the grease forced in without it coming out of the RH wheel nut indicator holes, it won't go in. If you get some in, you then have to reassemble and readjust the gear selector.
I have tried it, but not successfully, though I don't have a long thin grease-gun thingy.

Seems simpler to me to have a dedicated hole somewhere. Might take some engineering, but once fitted, it's there.
Failing that, it's maybe a good idea to do what I've done, and to take out the cassette body and spoon it in, but I was thinking of being able to inject grease without stripping anything ............... something as simple as putting air in the tyres.

Maybe there's no point in it at all.

[[XAP]Bob]

I just use a syringe, and a bag of Brucey's special sauce.
There is a chance that I take the wheel nut off of course (been a while, since it's hanging up at the moment - but there are plans afoot)

[Mick F]

Rolls Royce solution is having seals on the outside of bearings, and be able to fill up the hub without leakage no matter how the grease is put in.

[[XAP]Bob]

Rolls Royce gave more horsepower available to drag seals around with.

[mjr]

Rolls Royce gave more horsepower available to drag seals around with.

Don't drag seals around! It's cruel!

Seals

[Geoff.D]

Rolls Royce gave more horsepower available to drag seals around with.

Don't drag seals around! It's cruel!
geograph-1016182-by-Geoff-Clark.jpg

Wot? No dust covers?

[Mick F]

There's a sort of dust cover on the LH side, but not much of one. Item 19.
The RH side is just cup and cone balls open to the elements.
http://www.sturmey-archer.com/files/cat ... CS-RK3.pdf

[Brucey]

IIRC it may be possible to fit a seal from another hub if you want improved sealing here

cheers

[Mick F]

25miles this morning on the Moulton. Out very early because it's going to be a scorcher today.

Not ridden Moulton for over a week, so any of the soft grease that would have settled, must have done.
After and during the ride, there was no leakage seen.
Also, I was riding in near silence. SA hub was lovely and quiet and completely rattle free.

Highly recommended:
50:50 mixture of black moly CV joint grease and Hypoy 90 gearbox oil, spooned in with the cassette carrier removed on the RH side, and into the LH side with the cone etc removed. Put in as much as you can.