Jury-rigging a geared duallie as a SS to get home

El Guapo

Likes Bikes
Laugh at my misfortune, but please, give me some advice on how to succesfully jury-rig a geared duallie to get home when a rock jumps up and attacks your rear mech!

Vegetable and I did the 6' track in the blue mountains yesterday. Epic, awesome singletrack all the way to the Cox's River and then two of the biggest climbs I have ever had the pleasure of cresting on a MTB. Over an hour's worth of climbing. After a short break to regroup, we were off again, destination Jenolan caves. Maybe two hundred metres later, a fist sized rock somehow got caught up with the path of my rear wheel and took out the rear mech. Oh joy.

Now for the interesting part...After removing the damaged item, the gear cable etc.. We tried to jury rig the Dawg to get back to the car, about 20Km's away. At first we tried to shoprten the chain to a 32/28, but couldn't tension it enough to stop it shifting. Eventually, after much frustration, we settled on a 44/16 or something equally stupid. It worked OK on the first descent, but somewhere jumped a gear at the rear and was so tight that it made peddling almost impossible. I have never seen a chain have so much tension on it, it was rather disquieting to say the least. Upon approaching some climbing, I decided to try the granny ring, hoping I could get a 22/28 going. More shortening of the chain, some faffing around vainly experimenting with the broken rear mech as a tensioning device (very hard when you've only got one cable-tie, Doh!) Got it working with no tensioner in 22/28, climbed OK for about two minutes, until I tried to negotiate a rut, the suspensions sinks, chain moves....Crunch.

From then on, lots of pushing, and one last vain attempt to ride, this time with the chain skipping from the 30/32 at the back until the tension bent the 32's teeth at 90 degrees to the rest of the cassette. Oh well, I am a male after all, denial is one of my strong points, "I will get this thing to work if I just stomp HARDER". The chain tension was like a guy rope on the Harbour Bridge by this stage, had to break the chain, because we couldn't remove the back wheel to get any slack. Nearly took out my face with the chain when it finally gave way.

I had to walk the final 15km's except for the ball-tearing second descent, the lovely, flowing singletrack turned into a lug>trip>stumble>hoik uphill nearly all the way back to the car.

So, any suggestions on how to jury rig said bike to get home? Oh and just for my own vicarious enjoyment, if you want to post your worst ride experiences as well, it would make me feel a lot better!

I have attached a few pics of said jury-rigged action.

Cheers,
 

Attachments

That happened to me awhile ago, and this idea did work, so try it some time!
Take the smashed mech completely off, (you make it sound like it was that bad!) So, the mech is completely off, with the cable wrapped up with a cable tie, or just removed alltogether.

Now, tension the chain, whilst in a middle gear (one that you can ride on most grades) Keep the spare links from the chain. Jump on, and off you go! DO NOT stand up, in case the chain slips or something bad. Just take it easy and be grateful that you arent walking!

Also, if your changer/mech cable snaps from use, or your mech still kinda works abit, then remove the cable completely from the mech, and adjust the screw/s on the mech itself, to 'fit' a middle/average gear, and ride home. If you don't understand how to adjust the screws, then just loosen the top one on most mechs, and that will allow the mech to go UP a gear or two (toward granny gear), and tighten the bottom one, to stop it from shifting toward the HARDEST gear. Just play around til you get it right....

On the same note, if you get a flat, and you have a car valve tube, instead of a schrader valve tube, just cut/stab/prod/jab a hole in your expensive new tyre, and pass the valve thru the hole (since it won't fit thru the hole in the rim) And pump it up real hard to prevent tyre flex.
Then replace the tyre, instead of the rim... ;)

Hope that helps???
 

digger

Likes Dirt
Unless it's a rotec with a single pivot around the BB shell or you can totally lockout your rear wheel travel I can't see any of avoiding walking. (you could carry a singulator type of replacement) I had the same problem on my FSR. The chain length changes as you compress the suspension. I snapped my chain trying to bunnyhop or manual sections about 3 times before giving up and starting to walk. just one of those things. sounds like you had a good ride anyway.
 

DaGonz

Eats Squid
until I tried to negotiate a rut, the suspensions sinks, chain moves....Crunch.

...

I have attached a few pics of said jury-rigged action.
Wow... what a really sucky place to break a derailieur, right at the bolt!

Suspension does lots of evil things. If you need to jury rig a dually for anything, you need to lock it out, either via the appropriate lever or jack up the pressure as much as you can or both. Even once you've done this, it can still possibly move enough to cause issues though if you're carefull and don't go over too rough a terrain, it can be enough to get you home. There are probably other options but may not be inline with your frame warranty :)

Most of your issues with skipping were probably due two things: having your chain tension move under the suspension, and not picking a straight chain line. 32/28 is kinda gonna be prone to pull down the cassette, you'll need something in the middle.

Fix the suspension, and a straighter chain line and you might have been trumps

*shrug*

Cheers
Gonz - experienced spoon handler...
 

alchemist

Manly Warringah MTB Club
More zip-ties (shoe laces/hydropack straps/gaffer tape/spare tubes/velcro). Attach derailleur to chainstay to provide a bit of tension, but still SS pick the easiest gear you can get a reasonable chain line on.

Get home, through derailleur and bouncy bike in bin and get a propper SS.
 

El Guapo

Likes Bikes
More zip-ties (shoe laces/hydropack straps/gaffer tape/spare tubes/velcro). Get home, through derailleur and bouncy bike in bin and get a propper SS.
Ah, Alchemist, you are so PREDICTABLE. The vegetable and I were discussing posting yesterday whilst up to our elbows in repairs and we mooted the possiblity of you posting a similar response. I would like to see the state of me after an hour of climbing on an SS at 10-15%. If god had wanted us to ride SS, he wouldn't have given us thumbs for shifting!!!
 

slaw

Likes Bikes
Even on a hardtail it can be hard to find a gear combination that works. A friend broke his rear derailleur on a tour in Western Victoria we were doing over this summer. I'd often carry a spare on such trips, but since I was riding my new Rohloff equipped bike, I didn't bother. No one else in the group had a spare so he had to do the best he could with shortening his chain.

Unfortunately he had a similar experience to yours with the chain bouncing into other gears. Once it become so tight that we believe it might have bent his axle in the process.

One thing he tried was to wrap the chain with some plastic sheeting (another guy's chopping board) but that had marginal success.

Luckily, the Logan's Cycles in Portland came to our rescue by delivering a new derailleur to the caravan park where we were staying that night, some 30km from Portland.

The same shop later rescued us again when another guy's bottom bracket fell to bits. They sent out a replacement and tools via the boys in blue courier service to our campsite in the forest.

http://mbtc.atspace.com/lowerglenelg/slides/Freds derailleur.html
 
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