Talbot Frameworks Tandem - Sik Fadez Family Chariot

Maybe build it with a 650C rear so the downhill bits aren't as steep? #science

The other option might be to get some discs laser cut that have a much larger surface area and can radiate the heat out more ably than a standard 203mm disc.

What we need is a Man of Science to work out the energy generated by a spirited descent of Ventoux by a laden tandem.

On my cycle to Excel last night I'd been imagining how we might use a magnetic drag brake as seen in (for e.g.) turbo trainers - they seem to have no issue generating 300 watts of retardation for an hour without cooking themselves. Lot of mass there, of course.

My old pug tandem had a thread on drum brake actuated by a friction gear lever. Not sure of the name of it. It weighed roughly as much as an oil tanker.
It worked really well at setting a top speed on descents and left the rim brakes for normal use. It did get insanely hot but never failed on me.

No doubt things have moved on since that was top shelf but it was a good bit of kit.

I still have an ancient wheel built up with my Arai drum if anyone wants to play with it.

(700c, 135mm)

^^I'm going to guess it was an Arai drum brake.

Yup that's the badger. Worked like a champ on the friction lever.

My current tandem also has a Atom drum brake (same one as used on old mopeds) and 2x cantis. Drum brake was pretty much useless and was a bit of a mission to get set up right when changing tyres etc as all cables had to come off. Do we have any engineering types round these parts these days? Maybe @mdcc_tester has an opinion?

Fixed and a caliper brakes is Tester approved..

My preference, since you're going custom is for a custom steel fork with a nice 4-pot caliper on each leg to take a hub that will take a 203mm disc each side. Then use a backward problem solver thingie and a Hope V-twin to split one cable from your shifter into the two hydraulic feeds for the calipers. Do it properly.

Fixed and a caliper brakes is Tester approved..

For a race bike used on flat courses

Pair of HS33s plumbed in to SRAM wireless. Past, meet future, meet a solution that might actually work.

Actually scrap that, Magura use Mineral don't they? Thought it was Dot for a second. Shimano Di2 it is then

This would work, but I'm having a whole-body shiver moment thinking about how we'd make it look elegant.

Just stick a motorcycle brake on it and be done with it

Scale a Buell style brake to bicycle dimensions, should allow rotors of about 600mm :-)

Looked at that already, issue is how you attach the rotor to the rim.

Just stick a motorcycle brake on it and be done with it

A) fails the elegant requirement and B) the "heavier than the Lusitania" test.

Build a brake dynamometer and test to see which combination of OTP parts will work?

To be fair, this isn't going to be the first tandem which has ever been taken touring in the Alps. I expect a quick ask around the Tandem Club will elicit several known-good solutions.

surely increasing the volume of fluid in the lines and using a f1 style funnel shaped vent is all you need!

and maybe an emergency system to release a refrigerant onto the brake calliper if it all gets too hot1

It would pass the "won't kill you" test, though.

You just have an abusive relationship with hydraulics.

Double front disks on motorbikes aren't that ugly.
Far less than a drum break .

I was thinking about one lever for front+ rear ,
and one lever for the extra front.

What defeats it,
is that you need to be able to shed speed constantly,
and disks are not good at this.

Just to chip in on the rear brake conundrum, from what I gather the drum/disc brake is only really useful when heavily loaded on long descents. Rim brakes will have enough power to stop a loaded tandem (different story if it's wet but that's the same for any bike), but if you use them too much the rim can overheat and burst the inner tube. A hub brake doesn't have this problem.

I know of a couple touring from NZ to London, loaded with shitloads of stuff including a trailer, they didn't have a disc on the rear and their inner tube exploded on a descent at high speed. Not nice. The frame builder at Longstaff was in the room too and he was not impressed.

What we need is a Man of Science to work out the energy generated by a spirited descent of Ventoux by a laden tandem.

Right then

The major component of this would be kinetic energy (rather than the component of gravitational potential energy you are resisting by going down a slope), so lets estimate this.
Assume m = 175kg (tandem, two riders, loaded)
At thirty five miles an hour, v = 15m/s approx.
Kinetic energy = 1/2 m * v squared
= circa 19,700 joules (or Watt-seconds)

If you wanted to stop all of this dead in ten seconds, you'd need to apply 1970 watts.
Or five seconds, 3940 watts.

#fridayscience
#flamestorm
#caveatemptor