BS: Tandem Bicycles

Subject: BS: Tandem Bicycles
From: GUEST,Dazbo at work ;-)
Date: 02 Oct 07 - 05:54 AM

I'm a fairly keen (fair weather) cyclist and have never ridden a tandem bike. It does strike me though that (in my atrophied mechanical engineering mind) that it would be "better" if the front and rear pedals were off set by 90 degrees. Now I'm sure I'm not the first person to think this but as all the tandems I've seen the pedals are in synch there must be a good reason why.

I can only think of one possible reason: when starting off only one cyclist can apply pressure to a pedal i.e. starting at half power.

Any tandem riders out there?

Subject: RE: BS: Tandem Bicycles
From: PMB
Date: 02 Oct 07 - 06:19 AM

We tried it when we used to have a tandem years ago. It works very well for hills- if you are fairly evenly matched, the output torque is much more constant and you don't slow down nearly as much, this being the big drawback of tandems- they are MUCH harder on hills.

The big drawback is in starting off. The rear rider has to have one foot (usually the right) on the pedal at twenty past or twenty to- which means that the front pedaller has to put in all the initial power to get you moving and balanced. We worked it out after some practice, but we doing a right turn in heavy traffic was nervewracking.

There's also the problem of coordination. The stoker has to be well warned and quick on the uptake when starting off and stopping, otherwise they can easily get a smart rap across the shins as the pedals start or stop unexpectedly. With the pedals in line, it's much easier to follow the leader as you work in unison. I suppose people who are good at singing rounds together should be good at deviant tandeming.

So if you fancy a go at tandeming, and have a good powerful initial thrust (ooer missus), strong arms to keep the balance on starting, a pal with good anticipation, and a quiet road to practice on, I think it's worth having a go.

Subject: RE: BS: Tandem Bicycles
From: Grab
Date: 02 Oct 07 - 06:19 AM

I'm not a tandem cyclist, but I do know the reason - it's corners. When you go round a corner sharply, you want the pedals on the inside of the corner at the top to avoid them catching the ground. If your pedals are offset, it'd be rather difficult to get both pedals raised.

Graham.

Subject: RE: BS: Tandem Bicycles
From: The Fooles Troupe
Date: 02 Oct 07 - 07:05 AM

"If your pedals are offset, it'd be rather difficult to get both pedals raised."

A nice lady told me that was my probelm...ooo, er...

... leaving now...

Subject: RE: BS: Tandem Bicycles
From: GUEST,buspassed
Date: 02 Oct 07 - 07:25 AM

On a recent holiday in Whitby outside the bike shop there we saw the strangest modern tandam, the front part was ridden in a recumbant position while the rear rider sat up normally. The bike shop owner knew nothing about it's origins as it was only in for repair.

The wife suggested it might be a local service for picking up p****d cyclists and taking them home safely!

Subject: RE: BS: Tandem Bicycles
From: PMB
Date: 02 Oct 07 - 07:40 AM

Not a problem Graham, as long as you corner with the pedals on the inside at ten past and ten to. We set ours with the front pedal leading the rear so that the stoker has a cue from the movement of the pedals to put power back on.

Subject: RE: BS: Tandem Bicycles
From: artbrooks
Date: 02 Oct 07 - 08:10 AM

It has been a while since we tandemed (herself didn't like not being able to see ahead clearly and really didn't like somebody else steering), but it seems that offset pedals would be a problem if you stand to muscle up hills rather than use super-low gears.

Subject: RE: BS: Tandem Bicycles
From: Gedpipes
Date: 02 Oct 07 - 08:42 AM

Ive got one you can have for fifty quid

Subject: RE: BS: Tandem Bicycles
From: Wolfgang
Date: 02 Oct 07 - 10:28 AM

I had a tandem for many years and the pedals were offset initially. I had to change that for riding was much more difficult. The reason: Both riders were not "swinging in tune" which made steering exactly much more difficult.

With a tandem you realise more than with a normal bike that the steering is not done with the handlebars but with shifting the weight first and only then use the handlebars. Once with my brother behind me we were cycling on a cycle lane which had a pole in the middle coming up to us. I had to slow down to a standstill before the pole and then I turned to him asking: "Say, you thought I wanted to pass on the right of the pole?" He said yes and because of that i was unable, though having the handlebars at my command, to pass to the left of the pole as I thought was the better way.

I often stopped for hitchhikers (they usually didn't dare to say no thanks I wait for a car) and with someone not used to a tandem the pedals being not parallel was really bad.

Last argument: If it would be any good you'd have seen it at the Olympics or world championship tandem competitions.

Picture of the most successful tandem, Morelon/Trentin, offered as proof

Wolfgang

Subject: RE: BS: Tandem Bicycles
From: PMB
Date: 02 Oct 07 - 11:21 AM

From http://www.sheldonbrown.com/synchain.html:


The usual setup for a tandem synch chain has the two cyclists pedaling in exact synchronization, to when the captain's right pedal is straight up the stoker's right pedal will also be straight up. This is called "in phase."

If the cranks are at different angles from one another, they are described as "out of phase" sometimes with an angular measurment. For instance, if the captain's right pedal is at the top of the stroke while the stoker's right pedal is at the bottom of the stroke, that would be 180 degrees out of phase. (Nobody uses 180 degrees out of phase, it just makes the bike handle weird with no benefit.)

if the captain's cranks are horizontal when the stoker's cranks are vertical, that would be 90 degrees out of phase.

A minority of tandemists prefer "out of phase" setups, usually 90 degrees, with the captain's cranks 90 degrees forward of the stoker's. The advantage touted for this system is that it smooths out the power curve so that one of the riders is able to exert full force on one of the pedals at all times. Some folks believe this offers benefits in climbing, but I don't know of any evidence to support that theory.

        90 degrees out-of-phase setups also reduce maximum stresses on the frame and drivetrain, so parts mighg last a bit longer this way.

There are a couple of serious drawbacks to this system:

    * The riders must exercise great care in cornering to avoid striking a pedal.
    * The riders body movements are out-of-synch, which reduces the feeling of "togetherness" and also can complicate steering/handling especially at slow speeds.

Some tandemists prefer a setup where the cranks are only slightly out of phase, typically with the captiain's cranks just a few degrees ahead of the stoker's cranks.

Fortunately, no hardware changes are required if you wish to experiment with out-of-phase cranks. It's just a matter of removing and re-installing the chain.

    There are essentially three entities riding a Tandem:
    The captain, the stoker, and the spirit.
    It is the spirit who likes in-phase cranks.

As I say, I've tried it and found it had some advantages. I thought of making up a Pattent Devvis so that you could start off in phase, then flip the 90 degrees once you were under way. Coulkd have made my fortune if both the tandemists in Britain had bought it.

Subject: RE: BS: Tandem Bicycles
From: Greg B
Date: 02 Oct 07 - 04:33 PM

So, what's the trick for learning to do this tandem thing
and not getting killed? I tried it once, and don't mind saying
that it scared the living daylights out of me, and I was in
the front.

Subject: RE: BS: Tandem Bicycles
From: Dazbo
Date: 02 Oct 07 - 05:02 PM

Well I never realised the person at the back was the stoker, very nautical, and the captain up front.

Subject: RE: BS: Tandem Bicycles
From: Bert
Date: 02 Oct 07 - 10:41 PM

The finest vehicle on the road.

Where are you Gedpipes? If you're anywhere near Colorado Springs, Colorado, then you've got a buyer.

I'd hate to even think of riding one that was out of sync. When I had a tandem years ago I always rode in front. I was a real bad rear seat rider as I couldn't relax and follow the leader.

Greg B. The only 'trick' is courage; although it does take a small amount of skill to control the beast.

Subject: RE: BS: Tandem Bicycles
From: Catherine Jayne
Date: 03 Oct 07 - 04:30 AM

We both really enjoy cycling and have talked about a tandem but haven't got round to trying one out. I think though we might stick to single bicycles for the time being. The information has been interesting, thank you!

Subject: RE: BS: Tandem Bicycles
From: GUEST,buspassed
Date: 03 Oct 07 - 04:33 AM

Strange nobody's mentioned the real downside of tandem riding, that, of course, being the risk of having buckets of water thrown over the dual crew by outraged citizens!

Subject: RE: BS: Tandem Bicycles
From: GUEST,Crystal, work computer has eaten my cookie!
Date: 03 Oct 07 - 05:30 AM

A the father of a friend of mine had a tandem and we spent a day one half term holiday learning to ride it (we were 12). As the lighter of us I was at the back which was a wierd experience! We managed an hours continuous cycle around the country roads by the end of the afternoon! Not bad really, and it was great fun!

Subject: RE: BS: Tandem Bicycles
From: Geoff the Duck
Date: 03 Oct 07 - 05:35 AM

Many years back a vintage bike rally ws taking place in the town I was living in. One bike was a ten-person bike. Apparently it did't actually have brakes.
Quack!
GtD.

Subject: RE: BS: Tandem Bicycles
From: Gedpipes
Date: 03 Oct 07 - 06:25 AM

Sorry Bert Colorado just a wee bit to far.
I'm in east Yorkshire. I'm clearing out my bikes so I'm serious about selling the tandem btw.
Its an sit up and beg 5 gear Yeomans, collector piece built in probably 1960s. Great for riding around town but not for long distances.   
Blue skies
Ged

Subject: RE: BS: Tandem Bicycles
From: Rumncoke
Date: 03 Oct 07 - 06:29 AM

My dad (born 1918) did an apprenticeship in bike building - that is actually taking some bits of tubing and welding them into the joints to start the process.

He worked on a light weight tandem that was to be used for speed trials on 25/50 miles of roads, and which got its riders into the Guinness Book of Records when it still had such ordinary things in it.

He and a friend took it out on the roads around York (Yorkshire, England) a couple of times for final tuning and adjustment. I'm afraid he is no longer around to ask about the setting up of the cranks, but was told that on their final outing they were overtaking cars.

Subject: RE: BS: Tandem Bicycles
From: Mr Red
Date: 03 Oct 07 - 08:06 AM

call me an engineer but

if there were a ratchet/clutch hub on one of the riders crankshaft then that rider could chose an angle - and get to change it dynamically. Small loss of torque, increase in cost, and probably the stroker would get to choose.

Must have been tried before. discuss.......

Subject: RE: BS: Tandem Bicycles
From: saulgoldie
Date: 03 Oct 07 - 08:22 AM

Hey Bert,
Make sure you get the proper size for you and your riding partner. There are two sizes on a tandem. The front of the bike, for the captain, and rear portion, for the stoker. It is crucial that you get the proper size for each of you. If it is too small, you may not be able to get the hands/feet/butt triangle adjusted to the right extension. This could be just uncomfortable, or it could give you bad enough form to cause injury. If it is too tall, you could get seriously injured in an emergency stop or even a normal stop. (Need I elaborate?)

By the way, plan on several very patient trial rides before you really get going. It takes quite a bit of coordination to make it work. Tandems have led to some marriages. But they have also helped cause some divorces, too. (True fact!)

I don't mean to sink the sale, Gedpipes. Too often people just buy "a bike" with no thought to size. The results can be anywhere from mildly annoying to very dangerous. I used to work in a bike shop, and I felt I should mention the importance of frame size.

Saul

Subject: RE: BS: Tandem Bicycles
From: Gedpipes
Date: 03 Oct 07 - 08:54 AM

as a time trialist I absolutely agree Saul.
Nice story rumncoke.
Blue skies

Subject: RE: BS: Tandem Bicycles
From: GUEST,Jeff
Date: 03 Oct 07 - 03:33 PM

If you go to www.bikeforums.net and scroll down to the tandems subheading you'll find 47 pages of threads w/all kinds of Q/A.

Subject: RE: BS: Tandem Bicycles
From: Dave Masterson
Date: 04 Oct 07 - 03:39 AM

Wolfgang, thanks for the photo of Morelon/Trentin. Brought back happy memories of seeing them race at the Good Friday meetings at Herne Hill back in the 60's. Amazing sprinters, legs like tree trunks! Last saw Daniel Morelon at Manchester Velodrome in 2005 when he was coach for the French National team.