Lafree motor playing up/ slipping in third gear

[marwigan]

Perhaps one for he who knows stuff...? my 'was for spares' 3 speed Lafree lite has started losing all traction when in third gear. one is pedalling along happily and then its clack clack and the pedals seems to slip a quarter turn so with no power; change down to second and we have 'drive' again. Does this whether or not power on. The gears incidentally appear to be set correctly judging from the yellow marker guide.
I took the housing off to see if i could see any chain/front ring/rear sprocket 'jumping'/ or visibly jarring. None seen.
I think slipping is coming from within the body of the motor.
I have taken these motors apart [ala Flecc's instructions] and can do again if i must. Any thoughts? is the motor knackered? I don't absolutely mind because in a way am looking to scrap any of my 4 Lafrees so i can ride others in the fleet. Nonetheless would like to fix it if poss.
Thanks

 

[flecc]

It sounds like the chainring freewheel is slipping. You'll know on these that the crank arms and chainring aren't as one like a normal bike, the chainring able to turn forward with the crank arms stationary.

The freewheel centre is number 3 on this photo of the pedalshaft assembly.

It's surrounded by the internally toothed housing on this photo, shown at two angles. The splines at the right are those the chainring sits on at number 2 on this photo.

The circular spring shown in this photo may be broken and failing to hold the pawls up in the engaged position you see on this photo.

With the pawls flapping around it will be luck whether one or both engage at any time. When they fail to engage the cranks will lose drive and the torque sensor will have no input, cutting the motor.
.

 

[marwigan]

Gosh, right on Q, this is like Springwatch dangle a fly outside a dark corner and it doesn't last long. Thank you very much Flecc for this timely and irresistible intelligence.
I can now plan to spend a day shortly in the back-yard with tools, meths and newspaper[for cleaning] handy, fired up to face the dread that is 'opening up the crank-case' and allow 1 to 2 days' for fiddling.
more anon...

 

[Tintaglia]

Have you tried just swapping one of your other rear wheels to see if the problem is in the hub gear? We have previously tried changing the front sprocket to cure this gear slipping but it made no difference.

Like you we have a collection of previously condemned Lafrees (3 on the premises and 2 out on loan!) We still haven't had a bad enough basket case to warrant using it for spares on the others but we are beginning to get some battery failures now.

Let us know how you get on with it

 

[flecc]

Have you tried just swapping one of your other rear wheels to see if the problem is in the hub gear?

Yes, also possible and impossible to be certain which in advance since both can lose torque input pressure and cut the motor power.
.

 

[marwigan]

Okay, this sounds simpler to try first thank you Tintaglia; I recognise this reluctance to write off a bike that just may just need one more tweak.
Wil post result of trials but may be a few days yet.

 

[marwigan]

Thought my earlier interlocutors deserved an update;
I've not done anything yet as- all the usual reasons but mainly cos i don't need to get the specified 3 speeder back on the road particularly quickly as using my 5 speed- how much easier to get the rear wheel off [open frame later model] for a puncture if you discard most of the chain guard- specifically the lower part. And my Pana. mk 2 Raleigh Leeds which loads on my rear towball cycle carrier so nicely and recently enjoyed a spin round the Machars [it's a real place].
Also haven't got another 3 speed hub to cross check ala Tintaglia. Got four speed and 2 x five speeds. I'll just wait for the warmer weather and fiddle next spring- but fiddle i will as these things are surely fixable- and certainly worth it.
Thanks for now e-guys