Author Topic: Large left hand thread single speed freewheel  (Read 296 times)

Tim Hall

  • I want to eat the fleeting shade of your lashes
Large left hand thread single speed freewheel
« on: March 16, 2020, 08:52:13 pm »
My Hase Pino is in need of some maintenance. The front chainset is the original and is (a) 20 years old and (b) has teeth that look increadibly hooked.

It is a screw on single speed freewheel, 26 tooth and looks to be a left hand thread, given the direction of the "lösen" arrow.

AFAIK freewheels are right hand thread. Is that correct?

I've found a 22 tooth left hand thread freewheel in the USA but can't seem to find a 26.  The rear chainset is a double, the inner being fitted with a26 tooth chainring, to connect to the front chain set.  The smallest chainring I can get on there is 26 tooth.

Questions:
1.  Does any one know of a 26 tooth left hand thread screw on freewheel?
2. If not, what will happen if I run the timing chain on 22/26? There's a chain tensioner in the circuit if that makes any odds.





;ooks left hand thread. The freewheel part is so the stoker can stop pedalling. To cope with it being left hand thread, there are two spot welds to fix it in place.  I can grind the welds off, exert some (a lot?) of grunt and hopefully unscrew it.  However, I can't find 
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

Re: Large left hand thread single speed freewheel
« Reply #1 on: March 16, 2020, 10:38:11 pm »
if you run the timing chain with odd-sized sprockets then the stoker and captain will have to pedal at different speeds and the while machine may go in and out of resonance as the synchronisation changes. It would certainly be a bit weird.

FWIW you may be able to rebuild the old freewheel using the outer part of a new RH freewheel and the inner parts of an old LH freewheel.

Do be 100% sure that is what you have though!

NB another machine which might use the same scheme is an 'Onderwater' childfront tandem; ISTR that has a freewheel in the (left side) front drive and it too might be of the same sort. Worth checking?

cheers

Re: Large left hand thread single speed freewheel
« Reply #2 on: March 17, 2020, 10:30:42 am »
further to the above, are you sure the freewheel you have isn't just a RH one with Loctite and spot welds to secure it?  The 'losen' arrow may refer to the lockring direction; lockrings are nearly always left threaded if they are to the RHS of a RH threaded freewheel.

If so it might still be easiest to rebuild the thing in situ using the outer part of a (similar) new freewheel; this would presumably avoid having to grind the welds out /break the threadlock and then reinstate these things.

cheers

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Large left hand thread single speed freewheel
« Reply #3 on: March 17, 2020, 11:06:59 am »
Thanks for that Brucey.

Photos of the offending part below:




It looks like a left hand thread to me, although I'm not sure why they used it. The welds seem to prevent it unscrewing.
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

LittleWheelsandBig

  • Whimsy Rider
Re: Large left hand thread single speed freewheel
« Reply #4 on: March 17, 2020, 11:22:18 am »
That looks like the 26t cog is fastened to a normal 18t freewheel (six bolts/ rivets).

It is commonplace for the freewheel to have a LH thread for the cone for its own bearings (eccentric rotation). The freewheel itself probably has a RH thread onto the hub and spotwelding the freewheel's cone is probably because the freewheel is mounted on the LH side of the bike, driven by a tandem crank with LH-side chain.

I don't think you need a special freewheel, just some metal bashing.
Wheel meet again, don't know where, don't know when...

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Large left hand thread single speed freewheel
« Reply #5 on: March 17, 2020, 11:29:39 am »
So get a 26t cog, drill the rivets out of the existing, remove then fit the new cog.  Presumably I'll have to remove the freewheel from the crank to get to the other side of the rivets?

(Meanwhile, I've emailed Hase to get their view)

There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

Re: Large left hand thread single speed freewheel
« Reply #6 on: March 17, 2020, 12:48:37 pm »
hang on, that is right-side drive, isn't it? [later pinos use a left side drive]  In which case the freewheel must have a RH thread to mount it onto the crank, and (like LWaB says) the lockring on the freewheel is left threaded onto the freewheel centre. [The freewheel uses a two-dog remover.]

If so the freewheel body is flipped left for right in its current installation, vs how it would normally be mounted on a wheel.  The welded lockring  could be for one of two reasons;

a) the lockring thread handedness doesn't work in principle in that installation or
B) the lockring thread handedness doesn't work in practice in that installation.

I suspect the latter; I have known of freewheels which have developed enough slack in the bearings that the lockring is able to contact the rest of the freewheel body (which is often not much), and should the loads be sufficient, it can cause the lockring to back out, even though conventional precession theory suggests otherwise. If so the welds are just belt and braces.

The freewheel appears to have threads running right through the centre. Having seen the photo I am pretty sure that the mounting  threads ought to be RH ones not LH ones. Provided these are not damaged or obstructed, you can test if they are RH threaded by screwing in an old left side BB cup, i.e. a RH threaded  adjusting cup not a LH threaded fixed cup.

Hase should be able to sell you the correct thing but if not riveting a new chainwheel to the extant freewheel body ought not to be too difficult.

BTW It wouldn't surprise me if the freewheel is incredibly difficult to unscrew from the crank; use the beefiest remover you can find and make sure it is bolted through the crank before you swing on it.

cheers

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Large left hand thread single speed freewheel
« Reply #7 on: March 17, 2020, 12:58:13 pm »
hang on, that is right-side drive, isn't it? [later pinos use a left side drive]  In which case the freewheel must have a RH thread to mount it onto the crank, and (like LWaB says) the lockring on the freewheel is left threaded onto the freewheel centre. [The freewheel uses a two-dog remover.]
Right side drive.
Quote

If so the freewheel body is flipped left for right in its current installation, vs how it would normally be mounted on a wheel.  The welded lockring  could be for one of two reasons;

a) the lockring thread handedness doesn't work in principle in that installation or
B) the lockring thread handedness doesn't work in practice in that installation.

I suspect the latter; I have known of freewheels which have developed enough slack in the bearings that the lockring is able to contact the rest of the freewheel body, and should the loads be sufficient, it can cause the lockring to back out, even though conventional precession theory suggests otherwise. If so the welds are just belt and braces.

The freewheel appears to have threads running right through the centre. Having seen the photo I am pretty sure that the mounting  threads ought to be RH ones not LH ones. Provided these are not damaged or obstructed, you can test if they are by screwing in an old left side BB cup, i.e. a RH threaded  adjusting cup not a LH threaded fixed cup.
Ah, peering closely, yes I can see threads on the inside of the "dogged" ring. I was distracted by the splines inboard of them. Diameter seems to be 33.6mm. The outer threads are 38.7mm.
Quote


Hase should be able to sell you the correct thing but if not riveting a new chainwheel to the extant freewheel body ought not to be too difficult.

BTW It wouldn't surprise me if the freewheel is incredibly difficult to unscrew from the crank; use the beefiest remover you can find and make sure it is bolted through the crank before you swing on it.

cheers
I've just had an email from Hase, saying they've got the bits in stock.  Hurrah! Next trick is getting the old one off...
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Large left hand thread single speed freewheel
« Reply #8 on: March 17, 2020, 02:13:26 pm »
Brucey, LWaB, you're both correct. I am a numpty. It is a right hand thread as you point out. Or as the man in Germany says:

Quote
It is a normal free wheel. We pointed the ring, otherwise it would open while pedalling, because it is on the "wrong" side.
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)