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Wanted: Tandem Crankset

Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

Wanted: Tandem Crankset

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Old 01-05-18, 10:44 AM
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Chukbacca
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Wanted: Tandem Crankset

Greetings all!

So I have an old Motiv Duet, I bought it from a fellow who allowed it to rot outside for $40. It needed virtually everything, but as I was new to riding a tandem, I wanted to see if the enthusiasm would be shared by my family, and if it was a good long term investment. Long story short, it's been a GREAT investment, and I've just replaced stuff as it has failed and as I could afford it (Tires, Chain, cables, etc). Last night, while at the local co-op, errors were made removing the front crankset with a goal of replacing the bottom bracket.

What I'm hoping for is that someone has a good usable crankset sitting in their garage that they wouldn't mind selling on the cheap. The co-op was great, but they didn't have any tandem specific parts on hand.

Here's a fun picture of a typical ride for us.
Thanks for your consideration!
Chuck
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Old 01-05-18, 12:40 PM
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CliffordK
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That must be a long bike towing two trailerbikes... eek.

I have a tandem frame that I built up from scratch. Rather than putting on a tandem crankset, I used a triple on the rear, and matching small ring on front. Then just used the small ring for the timing chain.

It worked for my needs, but unfortunately I couldn't get my nephew or niece interested in riding it.
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Old 01-05-18, 02:33 PM
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thumpism
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^What he said works if you begin with a triple crank but are willing to ride with a double for actual gearing. I happen to have most of a T/A tandem triple crankset; no BBs but the right side rear triple and two left syncronizing front and rear crankarms with small rings. What is missing is the right front bare arm, but you could use almost any RH crankarm if you don't mind how it looks. Functionally, there might be an issue with the Q factor since your bike's stays might splay more to clear the 26" rear wheel than this crank was designed to work with.


All this is from memory. My stuff is stashed in the garage and my not have seen the light of day since we moved here five years ago.
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Old 01-05-18, 02:44 PM
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fietsbob 
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With an internal gear hub, you really only need a double crankset for the stoker and a single up front..


the cross over drive can be kludged by re threading the 3 crankarms, other than final drive, with a pedal thread repair insert..
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Old 01-06-18, 09:48 AM
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I have a hard time believing the captain crank was destroyed beyond usability during removal. Far more likely is the bike had an eccentric with a wedge and the shop blew out the wedge threads trying to drive the wedge out by hitting the bolt. It seems like you would hit the wedge bolt like you would to loosen a standard stem. But that will destroy the eccentric. The proper way is actually to remove the bolt and hit the eccentric body away from the wedge with a BFH. http://www.bushnelltandems.com/artic...splitwedge.gif

https://www.rodbikes.com/store/?prod...bottom-bracket

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Old 01-06-18, 11:09 AM
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Chukbacca
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Thank you all for taking the time to respond!

It IS a very long train! My eldest will pedal if she's on a trailer, and my middle child will usually pedal if she's on a trailer...but really, I'm usually doing the bulk of the work. We went out nearly ever night in December to look at the lights, and we go to local parks every chance we get (nearly every weekend). It's entertaining how many people gawk.

The young fellow who was assisting me at the co-op didn't fully engage the crank puller into the crank, I saw it, it crossed my mind, and I should have said something but didn't; compounding the issue, neither one of us pulled the washer out. We ended up completely trashing the threads. It's no biggie, I chock it up to learning by making mistakes; and I'd rather make my mistakes on an old inexpensive bike.

The lead fellow stepped in once he realized what happened. We tried all sorts of things to get the crank off, finally we pulled the crank and eccentric out, I laid the crank on the vice and hit the center as hard as I could (even then it took a few strikes). We put a normal bike crank on the front, and didn't think about the repercussions of the pedals (it was 9:30pm). I would like to just rethread the crank arms (reversing their current threads), but I suspect that's not a probable option. That being said, I like the idea of using the modified triple crank.

Happy New Year!

Originally Posted by CliffordK View Post
That must be a long bike towing two trailerbikes... eek.
Rather than putting on a tandem crankset, I used a triple on the rear, and matching small ring on front. Then just used the small ring for the timing chain.
Originally Posted by thumpism View Post
^What he said works if you begin with a triple crank but are willing to ride with a double for actual gearing. I happen to have most of a T/A tandem triple crankset; no BBs but the right side rear triple and two left syncronizing front and rear crankarms with small rings. What is missing is the right front bare arm, but you could use almost any RH crankarm if you don't mind how it looks. Functionally, there might be an issue with the Q factor since your bike's stays might splay more to clear the 26" rear wheel than this crank was designed to work with.

All this is from memory. My stuff is stashed in the garage and my not have seen the light of day since we moved here five years ago.

Originally Posted by fietsbob View Post
With an internal gear hub, you really only need a double crankset for the stoker and a single up front..
the cross over drive can be kludged by re threading the 3 crankarms, other than final drive, with a pedal thread repair insert..
Originally Posted by base2 View Post
I have a hard time believing the captain crank was destroyed beyond usability during removal. Far more likely is the bike had an eccentric with a wedge and the shop blew out the wedge threads trying to drive the wedge out by hitting the bolt. It seems like you would hit the wedge bolt like you would to loosen a standard stem. But that will destroy the eccentric. The proper way is actually to remove the bolt and hit the eccentric body away from the wedge with a BFH.

Last edited by Chukbacca; 01-06-18 at 11:15 AM.
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Old 01-12-18, 08:53 PM
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I have some NOS Shimano Deore DX (MT-60) front tandem cranks if you are interested. Brand-new, nice cranks. 110/74 chainring BCDs, 175mm arms, takes a square taper BB. $40 + shipping if you are interested. (See attached photo... mine look just like these.)

Depending on the pedals you are running, if the axles are removable you can swap the axle left/right and just run standard cranks with standard pedal threads. I did this on one of our stokid crank setups when I ran it on the opposite side from what it was intended.

Or, run the pedals the "wrong" way, but just use lots of blue loctite to keep them from unthreading.

The best way to do it (apart from an actual tandem crank) is to drill out the pedal threads and install Helicoil inserts. Most bikes shops can do this, but it can be expensive as the tools and inserts aren't cheap. Once I also had luck running a pedal tap through messed up threads, but it's a challenge to do that as you need to be very careful to keep the tap straight when it goes in. If not, the pedal will thread on crooked. If you have access to cheap (aka free) cranks at the Co-Op, you could try this tap route first. If it doesn't work, try the Helicoils.
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Old 06-18-18, 10:23 PM
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Are you still looking for a crankset? I have a DImension tandem crankset that takes Shimano Octalink bottom brackets - I think V1 like Ultegra/105. I bought it to upgrade a mountain bike tandem that I ended up selling.

Captain cranks are 175, stoker 170 mm.

Drive side chainrings look to be 28/38/48.
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