[Duncan]

If the seventh time is an allowed fade, you have no brakes at the bottom of that 600 foot hill because you are maintaining speed all the way down in your calcs.

Maintaining speed is only 12 kW - not likely to overheat any modern brakes
The total energy could overheat the brakes but its over 20 times the time period

 

[remy_martian]

It's 12kW applied for ten minutes. Ten glowing hot space heaters trained on that disc of metal for ten minutes.

Look at your 6x energy-needed analysis, which coincidentally plugs right in to the 6 stops NZ regs...

 

[Duncan]

It's 12kW applied for ten minutes. Ten glowing hot space heaters trained on that disc of metal for ten minutes.

Look at your 6x energy-needed analysis, which coincidentally plugs right in to the 6 stops NZ regs...

On that disc of metal in a nice cool 100 kph breeze

Correction on those four discs of metal in a cool 100 kph breeze

 

[MattsAwesomeStuff]

American side is flatter than the Canadian side overall imho.

The American side isn't just flat, it's all on the upper side. You can't even see Horseshoe Falls from the US, just the crappy little American Falls. The US side is a sheer cliff the whole way. The Canadian side ranges from lower lake, to upper lake (top of the falls), to the hill that rises away from the water, up, and above the falls.

The downhills he's talking about are mild and long, it's not braking on the edge of a ravine. Old ladies and their walkers go up and down them around the casinos:

I find it hilarious that people with DUI's and such, or SouthAm/Euro/Asian tourists who only got a US visa, and can't get into Canada, thinking "well we'll just look at the falls from the US side", and they go out on that expensive observation platform that reaches right to the edge of the border, looking back at the crappy American falls/Bridal Veil falls (which aren't even 30% waterfall, they're like 45 degrees down to the lower lake most of the way), and are like "Oh wow! It's so beautiful, it's so amazing. Niagara Falls is a wonderful place!", and have literally no idea what's just a thousand feet farther down the cliff. The geography is such that you just barely, just can't quite see anything at all of Horseshoe Falls.

Anyway, I digress.

They're not rappelling over the edge on the US side. Braking is a non-issue with ordinary OEM brakes.

The only reason there's any braking concern is because the "brakes" on a Model T are a greased up cotton rag pressed against the transmission, and they're basically a suggestion. See SuperFastMatt's breakdown of the Model Y vs. Model T:

(Relevant section is at 10m30s)

You can do resistive braking instead of plug braking on the DC motor. Plug braking is basically putting the car in reverse and feathering the throttle. You're actually spending energy, to lose energy, so it dumps twice the heat into the motor than you actually remove from your momentum. Resistive braking is simple, but less powerful. Just a big dummy dump load. oven or stove or dryer element, not sure what the right ballpark would be. You'd want a heat shield separating it from the wooden car body though. It's only 10x as much heat to dissipate as an adult on a bicycle. It's really just not a lot of energy.

 

[piotrsko]

There you go: Google and Matt making my point about power and braking requirements being relatively small. Does now cause me to think this is a Canadian project but there were horse drawn touristy things on the American side, too.

 

[remy_martian]

According to Duncan's fairly correct energy calcs, you'll need a 12kW oven element to dump into, then...

Lets see...240V oven, that's 50A. Make that two or three...at 240V.

Yeah, bicycle, lol.

Meanwhile, find an Ontario Professional Engineer who is willing to work with you and sign off because it's illegal to transport the public in a homemade contrivance that has safety implications.

 

[MattsAwesomeStuff]

Does now cause me to think this is a Canadian project but there were horse drawn touristy things on the American side, too.

Oh, I didn't know anyone was confused about that. Can you guys not see the Canadian flag under his username? Also, first post: "I live in the niagara falls canada area. [email protected]" Specifies Canada and Canadian address.

The US side (Buffalo) isn't touristy. It's a rust belt crime-ridden dump. There's no hill above or below the falls, you have no idea you're anywhere other than an industrial park until you're half way over the Rainbow Bridge, through customs. From the Canadian side you're above the falls looking down at them any time you look southeast. The falls are on the US side, so you can't see them from the US side. It's just the edge of a cliff. You see them from across the water on the Canadian side.

 

[piotrsko]

Idunno, the forum seems confused about my nationality. I DON'T think I'm brazilian, arab, puerto rican, Canadian, or slovak but those are some of the IP addresses my anti phish browser uses so I figure others have the same issue with their identity flags. I try to not make poor snap decisions based on obviously bad data

It's 20 miles to Buffalo city limits so that's like saying the falls are part of that goofy little town the train from Montreal stops at.

Hmm no flag at all today.

 

[dddrewski]

This operation only makes sense to me if run from the Canadian side. Charge up, go up the hill, then REGEN back down the hill. Going slow, you'll get a lot of energy back.
My esthetic says definitely design for regen.

 

[GrayRaceCat]

The wilwood engineer tells me the system is designed to stop a 4500 lb vehicle at 60 mph in a panic stop I am 1500 lbs and doing 30 mph. he told me not to worry I am overbuilt .
The siemens automotive engineer explained there are two parts to this discussion. getting the wheels to stop turning on the car which the disc brakes will do without pause.

The Wilwood engineer is correct with regard to stopping.
The Siemens engineer said there were two parts; getting the wheels to stop is one, and what was the second?

My concern is that you now have a two-wheel hydraulic brake system with minimal fluid volume. The fluid only needs to hit 270 C/ 518 F to boil, and you lose the ability to stop. Holding a set speed on a downhill run for an extended period will heat brakes more than a highspeed panic stop. This is because, in a panic stop, the brakes have an opportunity to lose heat after you are stopped. With continued braking, the heat keeps building and can easily overwhelm the capacity (mass) of the brake disc to lose that heat. The 600-foot figure, I assume, is the elevation change. I was unable to find where you mention the distance over which you descend the 600 feet in any of your posts. Could you please let us know? Is it one continuous run, or are there stops along the way? What is the speed limit or desired maximum speed for the descent?
The engineers you spoke with took into account the speed and weight of the vehicle. I would suggest you consider a worst-case scenario. The number of occupants x the average weight of an adult male in your region + the estimated weight of the finished vehicle = Maximum Total Weight to be used when calculating the required mass for the brake discs.

In a modern car, you can rub the tires against the curb to scrub off speed, an option you don't have with wooden wheels.

 

[floydr]

The Siemens engineer said there were two parts; getting the wheels to stop is one, and what was the second?

The weak link is the friction pad where the rubber meets the road. a 30 inch 3 inch high pressure tire has 3 1/2 inch foot print. this is 1/3 the surface of a modern tire. the disc brakes will lock up the rear wheels long before regen kicks in

I suggested going with 1925 model T rims and tires as they wider and of a low pressure design. Approximately same total wheel and tire diameter.
Haven't heard a response to the suggestion as of yet.
Along with resistor braking this may work.
Later floyd

 

[remy_martian]

The resistor needs to dissipate ~12kW if Duncan's assumptions are correct (they're in the ballpark, imo) - about the size of the heating element in a household electric furnace...

 

[floydr]

Could some of the energy be lost by way of the disk brakes assuming one can get around the problem the Siemens engineer raised "brakes would lock up" If you could get a 50/50 split between resistor braking and the disk brakes then you would only need a 6,000 watt braking resistor. Still likely to be a sizeable resistor element.
Later floyd

 

[remy_martian]

Or...tow a trailer full of household hot water heaters and have 400 gallons of hot tea at the bottom of the escarpment.

 

[Duncan]

Or...tow a trailer full of household hot water heaters and have 400 gallons of hot tea at the bottom of the escarpment.

We have 2000 Joules per kg - and a 700 kg car - so 1,400,000 Joules
It takes 4,000 joules to heat 1 kg of water 1 degree
So to heat from 20C to 100C for tea is 320,000 joules per kg
So we can heat about 4.3 liters about one gallon of water (its in Canada so we use proper gallons) for our cup of tea
Sounds like a plan to me

Four 3 kW kettle elements in a five liter container