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PostPosted: Wed Aug 17, 2011 5:31 pm 
retrobike rider
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Joined: Mon May 03, 2010 1:21 pm
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Location: Cheshire
I'm embarking on an off road tandem build using two mountain bikes welded together and, whilst I've read what Sheldon Brown has to say on the matter, I'd be interested to know whether any of you guys have any top tips or direct experience.

Current build plan as follows:

19" Marin Eldridge Grade (1998) for the front
15.5" Ridgeback Mountain Sport (1999) rear
Deore LX 9 speed shifters, brakes, front & rear mech.
Mechanical discs 203/160
Single side drive 52/42/30 with granny ring sync chain
Downhill MTB rims & hubs
29er Cromo fork

I intend removing the chain and seat stays from the Marin and welding in a connecting bar between the two bottom brackets.

Any advice, suggestions or warnings welcome!


Last edited by s1monf on Sun Apr 29, 2012 12:34 pm, edited 2 times in total.

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PostPosted: Wed Aug 17, 2011 7:33 pm 
Retro Guru

Joined: Fri Apr 28, 2006 8:42 pm
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Location: Brighton
I'd advise not welding or you'll wonder where your tubes went.


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PostPosted: Wed Aug 17, 2011 9:55 pm 
retrobike rider
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When you have it finished, please make sure you have a bystander with a camera to record the first test ride.


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PostPosted: Wed Aug 17, 2011 11:30 pm 
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Location: Heathfield, East Sussex
Goodies! Goody, goody, yum yum... :lol:

http://www.youtube.com/watch?v=4-w8OKo4phg


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PostPosted: Wed Aug 17, 2011 11:57 pm 
retrobike rider
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Location: Exeter
Your plan sounds the same as these guys:

http://www.jonh.net/~jonh/hacktandem/

I read the whole thing ages ago just because the whole have a go nature of the exercise was fascinating

Not pretty welding though!


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PostPosted: Thu Aug 18, 2011 7:07 am 
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Location: Platsa, Messinias, Greece
terryhfs wrote:
I'd advise not welding or you'll wonder where your tubes went.


Not if you can TIG weld, how do you think that those frames were put together in the first place?


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PostPosted: Thu Aug 18, 2011 8:59 am 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8754
Location: New Forest, UK
I'd suggest that you check the front fork geometry. Tandems have weird steering (I have two) that remains neutral with lean. This stops the tandem from heading into the trees whenever the stoker moves.

Typically tandems have a steeper head angle and a big fork offset - this would be horrible on a solo but seems to work. Putting 29er forks on would seem to me a backwards step, and possibly some 40cm a/c forks would work better.

Anyway, have fun playing!


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PostPosted: Thu Aug 18, 2011 9:06 am 
retrobike rider
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Location: Worcestershire / West Midlands
Andy R wrote:
terryhfs wrote:
I'd advise not welding or you'll wonder where your tubes went.


Not if you can TIG weld, how do you think that those frames were put together in the first place?


:lol:


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 Post subject: Thanks
PostPosted: Thu Aug 18, 2011 10:29 am 
retrobike rider
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Joined: Mon May 03, 2010 1:21 pm
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Thanks for the feedback so far chaps.

With regards to the vague steering, we have a back up 26" cromo fork, however the 29ers have quite a bit of offset and the head angle on the Eldridge Grade is pretty steep to start with.
We do have access to TIG welding and plan to disect the head tube of the stoker's frame and weld to the seat tube in addition to the boom between and just above BB shells.

Should it be successful and hold together, what gearing would you suggest for trails and road?
I have no experience of riding a tandem and would be interested in knowing whether we should expect to be much quicker than when we are solo.
Currently planning to run 52-40 rings with a 9 speed 11-32/34/36 but we do ride routes with some fairly tasty climbs?

If there is an interest I will post pictures as the build progresses?


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PostPosted: Thu Aug 18, 2011 10:58 am 
retrobike rider
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Joined: Sat Nov 06, 2010 11:40 am
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Location: Exeter
Definitely do a build thread of it! That will be brilliant

Sadly I havde no direct prctical experience of tandems either

but there are a couple of guys on here that do

TIBOLTRIDER has a Dawes Double Edge, I believe...


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