Bob Sipp emergency gear change tool.

[Airbear]

Btw, Ian (equipo5) has a gearbox shimming/backing plate for a 4 speed. Would that work on a 5 speed box?

I just looked at Cycleworks and it appears that the 4 speed (US$94) is different to the 5 speed (US$88). I've been using Jeff's 5 speed measuring plate, and I imagine he wouldn't mind lending it out. I'm in the process of putting together a step by step, pictorial 'how-to' titled "A Woodworker's Guide to Gearbox Rebuilding". Watch this space.

[Major Softie]

I'm in the process of putting together a step by step, pictorial 'how-to' titled "A Woodworker's Guide to Gearbox Rebuilding". Watch this space.

Well, I certainly love the title.

Chuey????

[Sibbo]

I might do one called "A Boatbuilder's Guide to Not Fixing Gearboxes". I think I'm up to that, technically anyway.

[Airbear]

Edit: On page 4 of this thread is a revised tool and a link to a YouTube video of the tool in operation. End edit.

Ok, I finally got around to this.

I pulled a selector mechanism apart and disconnected the pawl spring. The one on the left is what happens when the spring breaks and on the right is what you need to achieve to be able to select a different gear to the one you are currently stuck in ...



I didn't bother with the Bob Sipp diagram (it was way up at the house). I snipped off a bit of 2.5mm fencing wire, made some bends, tweaked a bit, tried again and came up with this:





In practice, the dimensions are not too critical, nor is any strength required. An old fashioned wire coat-hanger would provide the perfect material and it can be bent easily with pliers. You are lifting a quite small lever against gravity. No centering plug is required. In use, feed the end through the filler hole





... and ...



... lift



With the pawl engaging the 'dogs' on the selector plate the gear lever becomes usable.

Obviously, with the back of the box open it was a simple matter to locate the pawl with the tool, so I tried it blind a few times. I quickly learned the feel and heard the characteristic click as the pawl lifted into position. I am confident that I could do this easily enough on the side of the road. I reckon I could now also find a fence, clip off some wire and make the tool on the spot.

If on blacktop, third gear is recommended to get you home. In town or the bush a different gear may be required.

By the way, provided the broken pawl spring doesn't interfere with the swinging of the pawl, it should be possible to turn the box (and/or bike) upside down to achieve the same effect.

[SteveD]

Excellent Charlie. I haven't got back to this project...too much stuff on lately. Great pix and I might get on and do some more next week. I've only managed to make one so far and with some limited practice didn't achieve a gear change. I'm sure the pix will help. They're great. It appears you insert then rotate cw until engaged where you want it.

[Airbear]

Excellent Charlie. I haven't got back to this project...too much stuff on lately. Great pix and I might get on and do some more next week. I've only managed to make one so far and with some limited practice didn't achieve a gear change. I'm sure the pix will help. They're great. It appears you insert then rotate cw until engaged where you want it.

Thanks Steve. Does the box you are playing with have a broken or disconnected spring? To disconnect it you need to remove the cam plates and the e-clip on the pawl lever pivot shaft to make enough room. It is worth doing. I'll keep this box set up here for Airhead afflicted visitors to play with.

It is really just a matter of lifting the pawl lever through maybe 30 degrees, about 8 or 10mm vertically. The wire hook touches the lever about 20mm from its pivot. You lift that couple of grams until you hear it click against the selector plate dogs and the gear lever will work again. In a real situation you would want a bit of rotation inside the gearbox to assist gear selection, probably by rotating the rear wheel with your foot to get some rotation via the output shaft - as the Wunderlich bloke suggests in the vid.

[SteveD]

Gearbox is ok apparently, but untested. It's a spare.

[Airbear]

Gearbox is ok apparently, but untested. It's a spare.

Ah, ok. So you won't be able to test the tool. Don't worry, just carry the tool with you and one day you may have the opportunity to use it. When the spring breaks the pawl drops down with gravity through that 30 degrees. You just poke around with the tool feeling for something that has a little bit of swinging mass - quite detectable - and when you lift it you'll hear and feel it click against something solid. At that point moving the gear shift lever will have the expected resistance. And you know the rest.

I'll set up a jig and make a bunch of these to spread around at the Oz BW gathering.

And when yer in the neighbourhood come and look at some box innards. There is stuff in there that your BMW will want you to know about ...

[enigmaT120]

Cool write up and pictures, thanks. But:

"By the way, provided the broken pawl spring doesn't interfere with the swinging of the pawl, it should be possible to turn the box (and/or bike) upside down to achieve the same effect."

I tried that on my gearbox after I pulled it off, and I still couldn't shift it even upside down.

[Airbear]

Cool write up and pictures, thanks. But:

"By the way, provided the broken pawl spring doesn't interfere with the swinging of the pawl, it should be possible to turn the box (and/or bike) upside down to achieve the same effect."

I tried that on my gearbox after I pulled it off, and I still couldn't shift it even upside down.

Yes Ed, I saw that earlier in the thread. I can only assume that somehow the broken spring was getting in the way or that the pawl shaft was somehow binding. Or maybe the thick gearbox oil meant it would take time. I dunno. When I was playing with this one I rotated the box in different directions and each time it was inverted heard the click that meant the pawl had moved into operational position.