Talbot Frameworks Tandem - Sik Fadez Family Chariot

Assume m = 175kg (two riders)

That sounds about right for my tandem. A loaded touring tandem could easily be 50kg over the bare rider mass without even considering camping.

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

My understanding* is that peak loads are not a problem per-se, disc brakes are pretty good at dealing with big decelerations (albeit, not again and again and again), it's the desire to have a brake constantly applied to keep speeds within a certain range where discs start to run out of answers as they generate more heat than the system can radiate away.

At which point the fluid can start to boil and goodbye to the brake until things cool down again.

So we're not looking for a dead stop, we're looking at applying (say) 500 watts opposed to the direction of travel, as it were.

Or to put it another way, venting 500 watts worth of kinetic energy as heat.

*Which may be wrong

bigger rotors to dissipate more heat? shimano vented pads?

Hope used to do a floating sandwich rotor. Believe they were rather heavy.

The solution in mountain biking always used to be just to get bigger discs. 225mm do ya?

this tandem has it nailed (at 0:18) ..(...ok offtopic):

https://www.youtube.com/watch?v=ImNqILCx9jI

What about solid tyres and a spoon brake?

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Tyres would melt faster than the brake fluid would evaporate?

The solution in mountain biking always used to be just to get bigger discs. 225mm do ya?

Solution to the wrong problem tho

Double front disc brake takes more load off rear braking needs

Technology is about 15 years old but could be revised and a possible Bespoked show winner

Lols, I have enough bikes with dubious braking capabilities :)

These guys enter the race every year.
They report warped rotors every year.
1'45 the speed differencial with a solo :)
https://www.youtube.com/watch?v=salr1_uc3PM

Can't you just put a drum + rim brake (or disc) on the rear? Seems to have worked for around 100 years ok before Everything Had To Have Disc Braks.

That's an amazing project, congratulation @7VEN, I'm really looking forward to see the progress of this. I recently Matt too and liking is passion for his craft I'm really keen in following all his work and his customers ideas.

Very true.

I'm not sure discs are the way forward for tandems. Much better to use a 620mm rotor than a 225mm one. HS33s would be rad.

Was there a reason cable discs arent being used? Won't evaporate or overheat (aside from the rotors but just use huge ones)

I've ridden cable disc and hydro disc on road bikes, pretty extensively, and hydro is night and day better.

Hs33 + arai drum = all the braking ever. Could even run a second hs33 under the chain stay for the lols.

Re: drum being a faff for tyre changes, mine had a neat little quick release for the cable, no idea what it looked like now but it took about 5 seconds to dis/re connect so never saw it as an issue. Presume something along those lines would be a breeze to make.

Same as the Arai but slightly less ugly:

https://tandemgeek.wordpress.com/2013/07/10/next-generation-drag-brake-now-available/

Not sure that would be for me tbh, trying to make this relatively light, stop well and look rad whilst embracing modern tech however not trying to reinvent the wheel and taking in all I can from CTC and YACF seasoned touring campaigners. I'll probably wish I did have one whilst sitting roadside on the Tourmalet waiting for the Hydraulic fluid to cool.

Currently, we have a combined weight of 105 kg unladen but it's only going to increase as she gets older and I get fatter.

combined weight of 105 kg

Think I might have a little cry....

I want those brakes, they work.
They're flying past everybody with flat bars.

The bike appears at the end.
https://www.youtube.com/watch?v=sjDW7cDhzAg

Been interesting reading this thread.

hydro is night and day better

I'm sure they are, but for this application after reading the discussion so far, it sounds like cables solve the problems that hydro creates. Also isn't this for father/daughter riding with some touring rather than for racing.

If the length of the rear hose is an issue for hyrdo and elegance is an issue, have you considered running some interal copper brake pipe? You could have nipples brazed into the frame and use tiny short runs of braided flexi bewtwixt frame and caliper.