Tester's Tandem

Twice-ish the force, twice-ish the mass..

Nah, power to weight and all that, a tandem would weigh less than 2 comparable bikes and have half the wheels rotating away.

But more power loss in drivetrain; more/less aerodynamic? Don't think the difference is that clear-cut to convincingly call it one way or the other. But given whose thread this is I'm sure we'll find out the answer soon enough ;)

yes but when you ride you are only concearned with your own pedalstroke and you apply the power and bend the bike as you please. I doubt that 2 ppl with the same power would get twice the watt on a tandem compared to what they get on alone on a regular bike when accelerating from low speed.

Then again im just speculating what i think sounds reasonable.

Not twice, but more.

So power to weight ratio should be smaller no?

Nah, on bike you push yourself and 2 wheels, on a tandem you push half a tandem and one (probably slightly weightier) wheel. I reckon even if you're not quite as efficient as you are on one your own bike you'll still be quicker. The pedals will be synchronised to offset some of the problems of only concentrating on what you are doing yourself anyway, and you'll be on a tandem, so thinking about the other mandem.

Hmm in a drag race id put my money on the guy on the single bike. But maybe id be out some cash.. as usual when i bet :)

So why does one loose so much speed at turns on a tandem?

It's not about the tandem, it's the effect on average speed of any delay when you're riding for a short time.

e.g. riding 10 miles in 29 minutes riding plus 1 minute stopped at junctions drops you from 20.69mph to 20.00mph, while losing a minute out of 20 drops you from 31.58mph to 30.00mph.

You don't make up the losses at the other end of the speed range either (e.g. going down the Bank), a tandem doing 60mph is only gaining 12s per mile over a solo doing 50mph, whereas for slow riders doing 20mph instead of 18mph gains you 20s per mile.

The inverse relationship between speed and time is a bastard, basically if you drop down to 10mph on a climb, you have to go at the speed of light on the corresponding descent to get your average back up to 20mph.

^Correct, naturally.

Everyone else seems to be tieing themselves up in knots about weight, rotating mass etc. Tandems are so fast because two riders are pushing the frontal area of one person into air resistance, so even two fat blokes are comparatively aerodynamic.

They're a bastard to get going because of the huge difficulties of synchronising two fat blokes (try getting out of the saddle on a tandem!), but once they're going, they fly! Don't try riding them up big hills either.....

My memory is that a tandem weighs pretty much the same as two bikes, because of the stiffened frame and heavy wheels, let us know about the finished weight Tester, if you can lift it.

Ah k.

Still remeber me not making sense of a car going 100km/h doing 10km in 6 min and same car going twice as fast doing it in 3 min yet if its going 150km/h it takes 4min and not 4.5..

Had me puzzled, but in my defense i was prolly 12!

Don't try riding them up big hills either.....

Dunno about that, me and Styx smashed Swains Lane again and again on Swaintoux a few years back, standing ups no biggie either in my experience when you've got your rhythm down...

Everyone else seems to be tieing themselves up in knots about weight, rotating mass etc.

We were talking about acceleration, to be fair..

Wheels are 1403g rear, 1217g front including skewer/bolts and rim tape, just 200g more for the set than the Hed3/Pro disc on my solo bike. Solid 15mm stainless steel axle in the rear just picked up from the machinist.

1 Attachment

Front BB will dispense with the stock threaded eccentric and cups, with the bearings pressed straight into a new plain bore housing, eventually

ftfm
Stock BB-4600 inserted into the original eccentric for now, as the cost of machining the new eccentric was a bit high ITTET

ftfm

Oh, tester...

bump

Nice one Indra... completely forgot about this thread. Wonder how the project is coming along?

It has been ridden about 3 miles solo, just to make sure nothing is about to fall off. Pending a rear brake, it's about 13.7kg by the differential bathroom scales method.

Thursday H10/10? Or do you not fancy coming down Hawthorn Hill on it just yet?

Definitely want another brake on it before taking that on, I can almost get to the corner at the bottom too fast on a solo.

so, you and hippo should be on fine form for taking the national 24h tandem record in sussex next year then?!

13.7kg, skinny guy powerlifting! It seems tandem=2 solos still applies. I would love to do a 24 on a tandem, just spread over, say, 10 days......

My TT bike weighs about 7.8kg, so the tandem is well under twice the weight.

can we see a nice driveside picture?

also a question, from a tandemnoob, is the pilot to stoker ratio always 1:1?