Brake failure resulting in airborne bakfiets

[N8!]

I'm on hydraulic discs,180mm front 160mm rear, sintered pads... it is NOT enough for a 10% grade. I'm carrying 80Ah @ 66.6v of battery, 3kw mid drive with a nuvinci CVT rear hub, steel frame weighs 80kg plus rider(60kg) & cargo.

I had a runaway situation yesterday and encountered a small ditch as I steered off the pavement into a driveway. The cargo bike, and cargo, became airborne. For a brief moment I was piloting an aircraft, but I did not fall with style.

I fell over as the bike landed but I stayed on the frame as we slid through the dirt and mud to a stop. I used all my drinking water and some puddles to cool the brakes, they were hissing and steaming as the water hit them.

Bicycle damage: headset bearing seat bent out of round, (fork moves fore and aft under brake load now, steering's a bit wonky too).
Rider damage: 2cm diameter abraision on the left knee, no blood loss.

The Flying Red Bakfiets, the black ebike was in the cargo basket at the time of the crash:

https://imgur.com/a/9qmOIzS

I've not ruled out scrapping this bike and building a lighter long tail, but still, I need better brakes on both bikes.

any suggestions?

 

[PaPaSteve]

It's possible for a hydraulic caliper to heat up enough to melt the feed line and then have no brakes.
Unfortunately, a lesson learned the hard way.
Cable brakes lines don't melt.
Santana Tandems sell a brake with a 10" disc rotor. link here
I've made my own disc rotors from cold rolled steel which have much better friction.
Automotive disc rotors are carbon steel for a reason.
Stainless is actually a poor friction material . . .

 

[Chalo]

Everyone who doesn't ask much of their brakes will tell you "discs are better!", but those of us with experience slowing down heavy bikes know there's a lot more thermal mass and surface area in a rim than in a disc rotor.

Since you don't have studs for V-brakes, the easiest thing would be to fit larger and thicker rotors. It won't make a huge difference, but it will help.

You could use linear pull adapter plates to mount good rim brakes on your bike. They're hard to find new these days, but there were a lot of them around at one time:

Another, perhaps easier approach would be to get mechanical disc calipers and then use dual cable levers to pull them and caliper rim brakes at the same time. If you choose to do this, use short pull disc calipers to better match the short pull rim brake calipers.

 

[N8!]

It's possible for a hydraulic caliper to heat up enough to melt the feed line and then have no brakes.
Unfortunately, a lesson learned the hard way.
Cable brakes lines don't melt.
Santana Tandems sell a brake with a 10" disc rotor. link here
I've made my own disc rotors from cold rolled steel which have much better friction.
Automotive disc rotors are carbon steel for a reason.
Stainless is actually a poor friction material . . .

Fortunately I was able to get the bike airborne before melting my feed line, unfortunately drag overcame lift in about .005 seconds. I have had significant brake issues with my cable braked bike on this same hill, I posted about it recently, but I think it's just due to cheap brakes on that bike.

I've considered a manual parking brake lever that forces a rubber shoe into the rear tire, simplicity is long lasting, not great braking response but better than boiling oil, splaying cables, failed tubes or flying.

Good idea on replacing the rotors, it's closer to my cost ability than a re-gen hub motor is. There's a nearby machine shop I could get those made, my lathe only swings 150mm.

 

[N8!]

Since you don't have studs for V-brakes

hmm... no.. but I do have a steel frame, a MIG welder and pile of steel donor bikes that do have V brakes

 

[Chalo]

hmm... no.. but I do have a steel frame, a MIG welder and pile of steel donor bikes that do have V brakes

Check out what Amberwolf has done in that regard. I think his favorite approach is to hack the brake arch off of a cheap steel suspension fork, then weld it to the subject frame or fork.

 

[harrisonpatm]

Everyone who doesn't ask much of their brakes will tell you "discs are better!", but those of us with experience slowing down heavy bikes know there's a lot more thermal mass and surface area in a rim than in a disc rotor.

Out of curiosity, would you still feel the same way regarding motorcycles? I.e., disc brakes vs drum brakes. I have drum brakes on my conversion, 400 pounds or so, and I feel comfortable with them, but lots of people suggest they're across the board inferior to disc brakes.

 

[Chalo]

Out of curiosity, would you still feel the same way regarding motorcycles? I.e., disc brakes vs drum brakes. I have drum brakes on my conversion, 400 pounds or so, and I feel comfortable with them, but lots of people suggest they're across the board inferior to disc brakes.

Motorcycle disc brakes are thermally superior to motorcycle drums. They don't necessarily work any better than say, twin leading shoe drums, but they discharge more heat and resist overheating better. They tend to have a larger working radius. They also weigh less, like for like. All these qualities make them better for racing, and everybody thinks that what's better for racing is better for sitting in traffic, I guess?

Bicycle discs are the opposite. They have inferior heat capacity and cooling capacity compared to rim brakes, they act on a much smaller radius, they weigh more, they make weaker wheels. They have two main things going for them. They don't care how big or small your wheel and tire are. And they make ignorant people pay more because "discs are better!" when you're ignorant.

 

[N8!]

Check out what Amberwolf has done in that regard. I think his favorite approach is to hack the brake arch off of a cheap steel suspension fork, then weld it to the subject frame or fork.

great idea, no need to worry about lining up the studs correctly when they are factory assembled and easily acquired from the pile.

 

[PaPaSteve]

Long before bicycle disc brake were available we (me, friends and customers) were blowing tires off the rims from overheating rim brakes.
Some nasty crashes not so different than what N8! has described here.
Next try was drum brakes which was an improvement by removing the heat from the tire but really no major improvement in stopping power.
Then came discs which were a slight improvement in stopping power but the early Magura versions had the same plastic feed lines as their rim brakes which, as mention earlier . . . melted off the caliper.
Custom disc's I made were waterjet cut at work.
Laser cut is an acceptable method.
Nowdays I send some of my CNC stuff out to SendCutSend
Their prices are often lower than me buying raw material to make in house.
Saying from years of hands on, real world experience . . . rim brakes would be my last consideration.

 

[99t4]

Out of curiosity, how long was the hill, and what was your speed? 80kg seems real heavy for a frame. Photos?

 

[Chalo]

Long before bicycle disc brake were available we (me, friends and customers) were blowing tires off the rims from overheating rim brakes.

Donut wheels and ultra lightweight rims don't offer as much thermal advantage as full sized wheels with generously sized rims.

I've heard lore about blowing off tires from braking heat, but despite tens of thousands of miles on e-bikes with over 500 lbs GVW and many of those in very hilly terrain, I've never witnessed it myself. On my own bikes or anybody's else's.

 

[The Toecutter]

any suggestions?

Chalo's advice is excellent, especially if you'd rather keep things cheap and simple, albeit this is most suitable for speeds under 30 mph, and you will deal with the downsides that this system comes with. I've had many bad experiences with rim brakes in inclement weather while placing close to 30,000 miles on road bikes over a period of 10 years, but I also ride fast and like a jackass. Albeit, these weren't even e-bikes, and the systems on these bikes were probably not as beefy as what Chalo uses on his electric cargo bike builds.

Another possibility is a Sturmey Archer 90mm cable-pull drum brake in each wheel. Initial stopping power is not nearly as good as the disc brake systems I've used(Avid BB5 cable-pulled which are junk, Avid BB7 cable-pulled which are acceptable to good, and a custom hydraulic system described below which is great), but in my Milan SL velomobile, these Strumey Archer drum brakes can still panic stop it from 60 mph while careening down a steep hill without overheating, although there is some noticeable brake fade during such a stop and the initial braking force is not as strong as I'd like. You have to wait 1/4 second or so for them to "bite" before the system starts to give you their full stopping power, but once they do, they'll lock your tires up no problem and have more thermal mass to absorb the lost kinetic energy than any disc brake system I've used on a bike. There is a risk of glazing over the pads inside the drums, but that hasn't happened to me.

If you insist on sticking with hydraulic disc brakes, contact adam333 on this board. The bicycle-specific hydraulic disc brake systems available on the mass market are all junk, IMO. However, adam333 made a dual-caliper single-lever hydraulic disc brake system for a KMX trike that is much more robust than these mass market systems. I've ordered it and used it. He tells me it is rated for 40 mph. It has a motorcycle lever with built-in fluid reservoir using DOT3 brake fluid. I have had great success with this system on my custom build velomobile thus far. It stops it straight 100% of the time. While it was made specifically to fit a KMX tadpole trike, you might be pointed to a place where you can obtain the components used to make your own system suited for your bike. It uses ATV-suitable calipers and aluminum components that won't melt in this application.

http://kmxsuspension.epizy.com/Trike%20Twin%20hydraulic%20disc%20brake.html

 

[Chalo]

For what it's worth, one of my local friends is currently in the process of sourcing/helping develop a bicycle compatible moped disc brake. It doesn't work with everything yet because of caliper dimensions, but it should be more potent than anything else in the space right now, and cheaper than you'd think.

 

[PaPaSteve]

Donut wheels and ultra lightweight rims don't offer as much thermal advantage as full sized wheels with generously sized rims.

I've heard lore about blowing off tires from braking heat, but despite tens of thousands of miles on e-bikes with over 500 lbs GVW and many of those in very hilly terrain, I've never witnessed it myself. On my own bikes or anybody's else's.

Good point
More mass in the rim and tire will slow the overall speed of the vehicle reducing the braking load and also increase the thermal distribution. Both might be helpful here.
Although, blowing tires from heat buildup is not lore.
Besides bicycles, race cars are known to suffer from the same issue if the brake cooling is not done correctly.

 

[neptronix]

Oof, it would be nice to have regen during descents like those. Dual 203mm's may even fade out in those conditions on a heavy bike. Regen won't fade if tuned appropriately.

Source: my local terrain is like a rollercoaster and i love climbing mountains.

Also, get into physical therapy as soon as you can if you've been injured. I had one of those airborne moments and it did a number on my shoulder and leg for a long time..

 

[N8!]

Out of curiosity, how long was the hill, and what was your speed? 80kg seems real heavy for a frame. Photos?

I only traveled 1.5 km in my descent before my crash, but I was running faster than usual because I was wearing a full face shield and helmet, I'm not clear on exactly how many meters I descended before the crash but it is the steepest part of the road. My speed was probably about 25-30kph when I hit the ditch, but I can't judge that, Ive got no speedometer and time got really slow for a moment.

There's a photo of the cargo bike and the bike I was carrying as cargo in the original post but here's the link if you can't view that

https://imgur.com/a/9qmOIzS

yes, 80kg is VERY heavy for a cargo bike.. stupid heavy, heavier than me.. I can carry my welder, a ladder, saws, grinders, PPE, extension cords, and even my kid all at the same time. I destroyed the CVT by overloading it but the bikes a beast, I built it in 2017-18 and have racked up about 2k km but I don't like to ride it down the hill.

 

[Papa]

Excellent read (all of it!). Santana builds, arguably, some of the finest tandems available

Brake Technology

santanatandem.com

"Finally, in the interest of safety, we feel compelled to pass along the following. Santana tests brakes on a 15 percent grade that’s two-thirds of a mile long. The vertical drop is 528 feet. At the bottom of this short test course the temperature of a disc brake caliper exceeds 500°F. (On a single the heat rise would be one third as great.) Two problems: First, this temperature melts plastic. Avid disc callipers with their red plastic fittings become paperweights after the disfigured adjusters render them unserviceable. Second, because cured carbon bicycle parts are destroyed if subjected to heat greater than 225°F, mounting a tandem’s disc caliper to a carbon fork or frame is, ahem, not recommended."

Santana 10" Rotor

 

[N8!]

Oof, it would be nice to have regen during descents like those. Dual 203mm's may even fade out in those conditions on a heavy bike. Regen won't fade if tuned appropriately.

Source: my local terrain is like a rollercoaster and i love climbing mountains.

Also, get into physical therapy as soon as you can if you've been injured. I had one of those airborne moments and it did a number on my shoulder and leg for a long time..

I would love to have regen but the cost is outside my range at this time.. I've looked at a Canadian company that makes a regen hub motor, seems like a great power plan for a different bike, maybe for my next build.

I appreciate the concern for my health, I was very lucky this time and the bike frame took the impact. My knee abrasion was mostly due to friction.

 

[The Toecutter]

Oof, it would be nice to have regen during descents like those. Dual 203mm's may even fade out in those conditions on a heavy bike. Regen won't fade if tuned appropriately.

Source: my local terrain is like a rollercoaster and i love climbing mountains.

Just make sure that your battery is not fully charged when you need to use regen, or it may not stop, or alternatively, may damage the battery, depending upon your controller and/or computer settings.

I plan to have AWD regen on mine at some point to compliment the hydraulic brake system on the front wheels and cable-pull BB7 disc brake in the rear. The total combined braking capability should be suitable for panic stopping the trike from interstate-appropriate speeds if the calculations I did are correct, but I will definitely need more rotor mass, and DOT tires aren't merely optional at this state anymore, but necessary.

 

[N8!]

Excellent read (all of it!). Santana builds, arguably, some of the finest tandems available

Brake Technology

santanatandem.com

"Finally, in the interest of safety, we feel compelled to pass along the following. Santana tests brakes on a 15 percent grade that’s two-thirds of a mile long. The vertical drop is 528 feet. At the bottom of this short test course the temperature of a disc brake caliper exceeds 500°F. (On a single the heat rise would be one third as great.) Two problems: First, this temperature melts plastic. Avid disc callipers with their red plastic fittings become paperweights after the disfigured adjusters render them unserviceable. Second, because cured carbon bicycle parts are destroyed if subjected to heat greater than 225°F, mounting a tandem’s disc caliper to a carbon fork or frame is, ahem, not recommended."

Grascias Papa, this is all good info, if my calipers got hot enough to get sqishy brakes that means mineral oil reaching it's boil point under pressure.... does pressure on oil raise boil point like it does water?

I know my calipers and discs made exciting hiss when water hit them, so they were above 100C/212F... and the oil got so hot my brakes got squishy... is that due to pads/rotor glowing or oil in the calipers boiling? I didnt' get any smell of hot brake pads, but they are tiny little things.

 

[N8!]

Just make sure that your battery is not fully charged when you need to use regen, or it may not stop, or alternatively, may damage the battery, depending upon your controller and/or computer settings.

I plan to have AWD regen on mine at some point to compliment the hydraulic brake system on the front wheels and cable-pull BB7 disc brake in the rear. The total combined braking capability should be suitable for panic stopping the trike from interstate-appropriate speeds if the calculations I did are correct, but I will definitely need more rotor mass, and DOT tires aren't merely optional at this state anymore, but necessary.

I've been thinking about this and my frame is a huge heat sink, if the battery was full and charge controller could dump extra amps into the frame...

of course a simple drouge 'chute would do the needful without programming or rotations....

 

[N8!]

Chalo's advice is excellent, especially if you'd rather keep things cheap and simple, albeit this is most suitable for speeds under 30 mph, and you will deal with the downsides that this system comes with. I've had many bad experiences with rim brakes in inclement weather while placing close to 30,000 miles on road bikes over a period of 10 years, but I also ride fast and like a jackass. Albeit, these weren't even e-bikes, and the systems on these bikes were probably not as beefy as what Chalo uses on his electric cargo bike builds.

Another possibility is a Sturmey Archer 90mm cable-pull drum brake in each wheel. Initial stopping power is not nearly as good as the disc brake systems I've used(Avid BB5 cable-pulled which are junk, Avid BB7 cable-pulled which are acceptable to good, and a custom hydraulic system described below which is great), but in my Milan SL velomobile, these Strumey Archer drum brakes can still panic stop it from 60 mph while careening down a steep hill without overheating, although there is some noticeable brake fade during such a stop and the initial braking force is not as strong as I'd like. You have to wait 1/4 second or so for them to "bite" before the system starts to give you their full stopping power, but once they do, they'll lock your tires up no problem and have more thermal mass to absorb the lost kinetic energy than any disc brake system I've used on a bike. There is a risk of glazing over the pads inside the drums, but that hasn't happened to me.

If you insist on sticking with hydraulic disc brakes, contact adam333 on this board. The bicycle-specific hydraulic disc brake systems available on the mass market are all junk, IMO. However, adam333 made a dual-caliper single-lever hydraulic disc brake system for a KMX trike that is much more robust than these mass market systems. I've ordered it and used it. He tells me it is rated for 40 mph. It has a motorcycle lever with built-in fluid reservoir using DOT3 brake fluid. I have had great success with this system on my custom build velomobile thus far. It stops it straight 100% of the time. While it was made specifically to fit a KMX tadpole trike, you might be pointed to a place where you can obtain the components used to make your own system suited for your bike. It uses ATV-suitable calipers and aluminum components that won't melt in this application.

http://kmxsuspension.epizy.com/Trike%20Twin%20hydraulic%20disc%20brake.html

thanks for suggesting a forum user, I'm still very new here.

all of my motorcycles and cars have had hyd brakes, drum or disc.. when I built this one I went hyd because I want a lot of WHOA with a lot of GO... the feedback I get from hyd brakes is great.. but the size of of the rim + rim-brakes makes chalo's point really clear too...

I've got hefty rims that can take V brakes.... and disc.... so por que no dos cpntroled by a cable? I've never seen a cable disc and rim brake combo...

 

[neptronix]

Excellent read (all of it!). Santana builds, arguably, some of the finest tandems available

Brake Technology

santanatandem.com

"Finally, in the interest of safety, we feel compelled to pass along the following. Santana tests brakes on a 15 percent grade that’s two-thirds of a mile long. The vertical drop is 528 feet. At the bottom of this short test course the temperature of a disc brake caliper exceeds 500°F. (On a single the heat rise would be one third as great.) Two problems: First, this temperature melts plastic. Avid disc callipers with their red plastic fittings become paperweights after the disfigured adjusters render them unserviceable. Second, because cured carbon bicycle parts are destroyed if subjected to heat greater than 225°F, mounting a tandem’s disc caliper to a carbon fork or frame is, ahem, not recommended."

First off, that brake is badass.

Second, i'm quite surprised a brake rotor of that diameter is only tested up to 2/3rds of a mile at that drop..
In my terrain i could use a brake rated to not overheat at roughly 10x that distance.

.....yeah, now you know why i'm such a big fan of regen.

The idea of cable + disc brakes might actually work in less extreme conditions than mine

 

[neptronix]

Just make sure that your battery is not fully charged when you need to use regen, or it may not stop, or alternatively, may damage the battery, depending upon your controller and/or computer settings.

I plan to have AWD regen on mine at some point to compliment the hydraulic brake system on the front wheels and cable-pull BB7 disc brake in the rear. The total combined braking capability should be suitable for panic stopping the trike from interstate-appropriate speeds if the calculations I did are correct, but I will definitely need more rotor mass, and DOT tires aren't merely optional at this state anymore, but necessary.

Yeah i know.
It's usually plenty drained once i get to the top.