Home made MTB tandem - It made it to the pub! - Pics page 4

[hamster]

My tandeming experiences:
1 Riding out of the saddle is difficult, so you need low gears to winch up. I'd be putting a 32T middle ring on it, or at least a 36.
2 Ground clearance is a major issue, especially pedal clearance. I guess that you will use some kind of singlespeed tensioner for the timing chain. Big timing chainrings are nicer to ride with (otherwise the drivetrain feels very mushy for the captain) but small rings give more clearance.
3 It's best that the stoker sits with both feet in the pedals when starting, ready to give a good shove as the captain starts off.
4 You need powerful brakes (but appear to have that sorted). The back brake is much more useful than on a solo and won't lock up easily. Similarly you can put down huge braking in the front without the back lifting.
5 36 spokes is desirable.
6 Downhill you will be more aerodynamic, and can power along straight sections. In the twisty stuff it's like driving a bus and you are a lot slower.

 

[s1monf]

Gearing etc

Thanks for the tips on gearing:
1 We may have to have a rethink as we were hoping to run a single sided drive using the granny on the rear for the timing chain which would mean being restringted to 30 tooth whilst the captain who has a slightly slower cadence would run a 32 up front - Would this be too small in your opnion?
It would be easy enough to pick up a 36T middle ring as long as there's sufficient clearance from the granny ring.
2 Initial measurements suggest that we will have about a 13" BB height on the front and 12" on the rear. with 170mm cranks and a 32T front and 50T rear big ring I'm hoping this will give sufficient clearance. I guess we can raise the rear by mounting the stoker fram higher up the captain's seat tube (oo er missus!).
3 Thanks for the stoker tip.
4 I'm hoping the brakes will be sufficient but will consider hydraulics up front if we need it.
5 We have add odd pair of rims: Mavic 321 36 hole DH front on Halo DH hubs and Halo DH 32 hole rear on Halo DH hubs and solid axle. Halo Twin Rail 2.2 Tyres.
6 Should we go really wide on the Captain's bars to aid steering or is most turning done via leaning?

We have a number of the bits for the build in our respective garages and have set a strict budget of £300 for the build so we won't be buying extravagant parts.

Picture of the Captain's frame and various other bits attached - Stoker's frame being collected tomorrow for the princely sum of 99 pence!!!

 

[phill77]

You will definitely appreciate lower gearing than you are used to on a single bike.
Climbing is frustrating because in my experience, no matter how fit both of you are, you will always be slower than when on a single.

Read This Thread for one very knowledgable mtb tandem riders experience of single side drivetrains.

 

[DeletedUser006]

Sounds like an intersteing project, Tandems are fun, especailly when going to the pub

This was mine but was moved on in December, good brakes are a must

more here http://www.retrobike.co.uk/forum/viewto ... quatrefoil

 

[s1monf]

Timing chain

Are there any issues with running smalling rings for the timing chain other than increased wear - I'm keen to utilise the granny on the rear triple.
It would be ideal if we could get away with 28 or 30 teeth for the timing chain?

 

[hamster]

Running smaller timing chain rings means more tension in the chain - you can really feel it springing as you push hard - even on my tandems which have 38T rings the captain's foot can rotate the crank around 10-20mm just as stretch. :shock:

I don't advise running different chainrings on the timing chain - the two of you will come in and out of phase which will make the thing hard to control. There are arguments for in-phase and 90 degrees out of phase, play around when you have got the hang of things and make your mind up. Personally I run in-phase with the stoker about two teeth in advance of me, so I can feel them come onto the power at the beginning of the stroke.

Tandems are hard work to steer, long bars definitely help - I used to get shoulder ache after 20 miles or so. I really get on well with On-One Marys. You do need to do lots of steering. Moving something 8 feet long down singletrack needs lots of steering input.

 

[MikeD]

a strict budget of £300 for the build

Without wishing to discourage you, I bought a perfectly good, little-used MTB tandem for less than that.

 

[s1monf]

Budget

I appreciate that I could buy one for that amount but I'm interested in the challenge of the build and the abject fear of the first test ride!

 

[MikeD]

Fair enough

Definitely stick with same-sized rings F&R for timing chain, things get very weird otherwise. You'll need some way of tensioning the timing chain, too.

 

[drcarlos]

We created a couple of Tandems in our teenage years, we did it by joining 2 BMX's together. Basically we removed the front wheel of one bike and using a bike with a long rear axle (for trick pegs) secured (in the loosest sense of the word) the forks of the second bike to the rear axle using a second nut. The whole bike then pivoted around the axle and using a set of forks with long lips and a kink at the end ensured they stayed in place (well for the month or so we played with them).
They were very fast and actually very manouvreable ground clearance also wasn't a problem either.
Looking back now I cringe as we were bloody crazy as they could really have separated at any time!

Carl.