Brake failure resulting in airborne bakfiets

[amberwolf]

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.

I'd still be using my dual-rim-brake setup on the heavy heavy-cargo SB Cruiser trike, if it hadn't been for the only collision I've ever been in, back in 2019. Pics of the intact version at the end of this post.


I converted to disc brakes then for a number of reasons, but so far the Avid BB7 MTN on the front has been more braking than I could use without losing front wheel traction, so I never went back and added the rim brakes too (wouldn't have added any braking). But the rotor does get RFH on every braking event. No surprise given the mass it has to stop from 20MPH.

Now I am using variable regen on the rear DD hubmotors to give just enough extra braking to greatly ease the stress on that single front mechanical brake.















On the old Crazybike2 I used the studs plus a bit of seatstay off another old frame to add rear brakes to the custom frame that didn't hve any yet








and the Crazybike2's first clamped-on arch (steel arch of a crappy fork, shaped and weld-reinforced to clamp to the aluminum studless fork I had at the time)




While I was doing the work to get that all done, nearly a decade ago now, Yogi decided it would be great to get his head stuck in the rotor of the hubmotor I had apart, leaning against a wall; I had to grab the rim to keep him from breaking himself or the world (thankfuly he wasn't panicky like some dogs would be). :lol:

 

[PaPaSteve]

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.

Could overheated feed lines be a source of squishy ?

 

[Papa]

Could overheated feed lines be a source of squishy ?

Heated liquid eventually starts boiling and begins changing to a vapor. Vapor, unlike liquid, is compressible - causing a spongy lever.

 

[4πr^2]

Hard to say for your specific situation. I have a couple of 12-14% down hill runs, and almost inescapably there is either a "T" intersection or a red traffic light at the bottom. I've found what helps me the most is to stab the brake hard, bleed off some speed, then release for a moment, let it cool, then stab hard again. Often I alternate front, rear, front, rear to allow some cooling in between. If you 'ride' the brakes continuously at a low or medium level, they will overheat and quickly loose braking ability.

Obviously bigger brakes will help some, but there is a lot to be said for technique, too.

 

[offGridDownUnder]

I'd still be using my dual-rim-brake setup on the heavy heavy-cargo SB Cruiser trike, if it hadn't been for the only collision I've ever been in, back in 2019. Pics of the intact version at the end of this post.
View attachment 341950

I converted to disc brakes then for a number of reasons, but so far the Avid BB7 MTN on the front has been more braking than I could use without losing front wheel traction, so I never went back and added the rim brakes too (wouldn't have added any braking). But the rotor does get RFH on every braking event. No surprise given the mass it has to stop from 20MPH.

Now I am using variable regen on the rear DD hubmotors to give just enough extra braking to greatly ease the stress on that single front mechanical brake.


View attachment 341951
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On the old Crazybike2 I used the studs plus a bit of seatstay off another old frame to add rear brakes to the custom frame that didn't hve any yet

View attachment 341967
View attachment 341968


View attachment 341963


and the Crazybike2's first clamped-on arch (steel arch of a crappy fork, shaped and weld-reinforced to clamp to the aluminum studless fork I had at the time)
View attachment 341964
View attachment 341965


While I was doing the work to get that all done, nearly a decade ago now, Yogi decided it would be great to get his head stuck in the rotor of the hubmotor I had apart, leaning against a wall; I had to grab the rim to keep him from breaking himself or the world (thankfuly he wasn't panicky like some dogs would be). :lol:
View attachment 341966

Man, some of the machines on this forum are like watching a Mad Max movie.

 

[Chalo]

Hard to say for your specific situation. I have a couple of 12-14% down hill runs, and almost inescapably there is either a "T" intersection or a red traffic light at the bottom. I've found what helps me the most is to stab the brake hard, bleed off some speed, then release for a moment, let it cool, then stab hard again. Often I alternate front, rear, front, rear to allow some cooling in between. If you 'ride' the brakes continuously at a low or medium level, they will overheat and quickly loose braking ability.

Obviously bigger brakes will help some, but there is a lot to be said for technique, too.

One thing that I've learned from my California friends (who have longer and taller inclines to ride than I do) is that there are two conflicting approaches to minimizing brake heating. One is to let 'er rip and go as fast as you are comfortable with downhill, so that aero drag does the lion's share of energy dissipation, conserving the mechanical brakes for fine adjustment and coming to a stop. The opposite is to tiptoe down at low speed, to maximize the time available for the brakes to shed the energy as heat.

The worst thing is what most people are instinctively inclined to do-- rolling down at modest speed of 15-20 mph, moderating the speed with brakes only, and making sure that almost all that potential energy gets dumped into the bike parts relatively quickly.

 

[Sturmey]

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.

I think moisture/water/vapor droplets in the air in tube can cause extra large increase in pressure with temperature. Another possible good reason for using nitrogen in tires which is normal I believe in formulae 1 cars (as well as 'Divvy' bikes etc).

 

[N8!]

I'd still be using my dual-rim-brake setup on the heavy heavy-cargo SB Cruiser trike, if it hadn't been for the only collision I've ever been in, back in 2019. Pics of the intact version at the end of this post.
View attachment 341950

I converted to disc brakes then for a number of reasons, but so far the Avid BB7 MTN on the front has been more braking than I could use without losing front wheel traction, so I never went back and added the rim brakes too (wouldn't have added any braking). But the rotor does get RFH on every braking event. No surprise given the mass it has to stop from 20MPH.

Now I am using variable regen on the rear DD hubmotors to give just enough extra braking to greatly ease the stress on that single front mechanical brake.


View attachment 341951
View attachment 341952
View attachment 341953
View attachment 341954
View attachment 341955
View attachment 341956
View attachment 341957
View attachment 341958
View attachment 341959




On the old Crazybike2 I used the studs plus a bit of seatstay off another old frame to add rear brakes to the custom frame that didn't hve any yet

View attachment 341967
View attachment 341968


View attachment 341963


and the Crazybike2's first clamped-on arch (steel arch of a crappy fork, shaped and weld-reinforced to clamp to the aluminum studless fork I had at the time)
View attachment 341964
View attachment 341965


While I was doing the work to get that all done, nearly a decade ago now, Yogi decided it would be great to get his head stuck in the rotor of the hubmotor I had apart, leaning against a wall; I had to grab the rim to keep him from breaking himself or the world (thankfuly he wasn't panicky like some dogs would be). :lol:
View attachment 341966

wow.... that is gnarly, I love it, the hose clamps are terrifying.

really good idea

 

[N8!]

Hard to say for your specific situation. I have a couple of 12-14% down hill runs, and almost inescapably there is either a "T" intersection or a red traffic light at the bottom. I've found what helps me the most is to stab the brake hard, bleed off some speed, then release for a moment, let it cool, then stab hard again. Often I alternate front, rear, front, rear to allow some cooling in between. If you 'ride' the brakes continuously at a low or medium level, they will overheat and quickly loose braking ability.

Obviously bigger brakes will help some, but there is a lot to be said for technique, too.

I was alternating them fore and aft but couldn't cool them fast enough, I normally stop just before the steepest part and cool them with water before I take the chicanes.... it's a "fun" part of the road, steepest grade with tight curves and single lane wide. At least once a year cars catch fire and/or concrete trucks break their transmissions and brakes fail as they roll backwards... that's the easy road, the hard road is so tight a F150 has to do 3 point turns and there's a uphill section with mean dogs at the top waiting for slow cyclists, they don't respond to mace at all.

 

[PaPaSteve]

Heated liquid eventually starts boiling and begins changing to a vapor. Vapor, unlike liquid, is compressible - causing a spongy lever.

A compound problem could exist here.
Should the fluid reach the temperature of vaporization then it should be expected the rubber or plastic feed line would also be hot enough to soften and stretch.
For extreme use brake systems like race cars or aircraft the flexible part of the brake lines are braided with a stainless steel weave to control stretch.

Tandems are sometimes built with two brakes on the rear wheel.
One brake at the hub and a second on the rim.
The bike ends up with three hand levers.
Some setups all three levers are controlled by the captain.
Or in other cases the stoker controls the hub brake (also known as the drag brake)

 

[Chalo]

Tandems are sometimes built with two brakes on the rear wheel.
One brake at the hub and a second on the rim.
The bike ends up with three hand levers.

The most usual arrangement was for the drum brake to be attached to a friction shifter, so it could be applied at the desired level and left engaged.

 

[lnanek]

At least where I am, Bionx motors get tossed out for free and old crappy ebike hub motors go for ~$40 on Facebook marketplace. I still have a free Bionx motor wheel laying around my garage I haven't converted yet. There was even a beautiful Grin front wheel motor that sells for over $400 on marketplace for $80 the other day that I barely resisted. Would have needed to weld the clutch on that, though. Anyway, feels like, with torque arms and a battery to discharge to, one could be slapped on the front to act like a regen brake fairly cheaply.

Barring that, I have seen bizarre cooling enhancements on many brakes. My own acoustic bike's Shimano IM-80 roller brake has huge cooling fins, as big as a disc brake rotor. I've seen v-brakes with large graphite cooling fins on them as well. Maybe there's a hack like that to add extra cooling, not just extra brakes.

 

[amberwolf]

At least where I am, Bionx motors get tossed out for free and old crappy ebike hub motors go for ~$40 on Facebook marketplace. I still have a free Bionx motor wheel laying around my garage I haven't converted yet.

If you run across any of the old Ultramotors (A2B Metro/etc, Stromer bikes) being tossed out, I'd be interested in those; they are much better built than most of the stuff out there, and handle enough power for a pair of them to run my heavy cargo trike (and do regen braking) without much more than 70C short peaks. I've only broken one so far (axle sheared, still not sure exactly why).
Some pics of them for identifying them, just in case:

The SB Cruiser : Amberwolf's 2WD Heavy Cargo Trike & Dog Carrier

clamping / pinching dropouts both ends, tight and flat to axle both ends both sides, no nuts needed on either side (have one on outside anyway just because there's axle length for it) is hubmotor with solid axles, can't see anything like qr axles or hollow ones? shear was at shoulder of axle...

endless-sphere.com

 

[amberwolf]

wow.... that is gnarly, I love it, the hose clamps are terrifying.

really good idea

Only use good (often old) hose clamps--IIRC the ones on that fork came off a 1985 Ford LTD, and were made by Ideal. Most of the clamps I see these days are junk. Either the straps are soft metal that easily deforms during tightening at the slots for the screw, or the housing that secures the screw to the straps is soft and deforms allowing the screw to unseat from the slots. (or both).

So I am always on the lookout for things that use hoseclamps, and salvage any that I can, especially if it is decades-old equipment as those usually have better clamps than modern stuff does.

I have yet to find any I can purchase new that are the equivalent of those old Ideal ones.


I'd've welded them but not possible on that aluminum fork for the steel parts, and I don't have the stuff needed to weld the aluminum bracket to the fork (or heat treat it all afterward).

But it worked, once I had a rim with a proper braking surface.


I do have less trouble maintaining the Avid BB7 disc vs the rim brakes, but it doesn't have the heat capacity to do a lot of hard braking over and over or continuous downhills, for instance. It might keep working, but it could certainly get hot enough to do the damage described in that linked page. :/

 

[The Toecutter]

A motor in each wheel should provide enough regen braking force that you'll be using your mechanical brakes less than 1% of the entire time spent braking, which will certainly take a load off of the mechanical or hydraulic brakes. If you can find suitable motors for that, it would be fitting for the application of a heavy cargo vehicle. But that also means you need three controllers and a shunt that can run them off of a single Cycle Analyst computer, or alternatively, three separate Cycle Analyst computers for each motor and controller pair.

I really badly want to experiment with AWD. I'm probably going to need to make some new custom spindles that are stronger in order to handle it, nevermind all of the additional straight-line acceleration potential that will be available and the mechanical robustness which that will require.

 

[amberwolf]

. But that also means you need three controllers and a shunt that can run them off of a single Cycle Analyst computer, or alternatively, three separate Cycle Analyst computers for each motor and controller pair.

Whether you can use one or require multiple depends on what you're trying to achieve.

I use just one to modulate the throttle for both my rear wheel motors, feeding it via PAS cadence to generate the throttle, and use one shunt in the main battery line to monitor both discharge and recharge / regen current for the entire system. I don't have matching motors or controllers, so the single CA doesn't make each subsystem perform to it's best. I also have no limiting, except for speed limited to 20MPH.

If i wanted :"identical" performance in both subsystems despite their differences, I'd need a separate CA and shunt for each controller/motor, even if they were both fed from the same PAS input. Then each controller could be fed or limited as needed to keep each one within whatever limits were chosen for each so that they perform "the same". I might also need a custom sensor that detects that one controller's current is higher than the other and increase throttle to the lower one to match it's load.


For three motors, you'd have to decide what you want them to do, how you want them to respond, and determine how they *do* respond with just a common control signal first. If they do what you want, then no need to complicate anything. If they don't, then you can determine how different each one responds from the way you want it to, and then decide if a separate CA is actually needed, or if you can just insert a pot into each throttle signal line to tune each one's input range for the output you want from it.

If the response is linearly different across the whole speed or power or torque range of your total system, then a pot will fix that by linearly changing the throttle input.

If the response is not linearly different, so that at one end they're different in one way, but at the other end they're different in another, and inbetween it varies in other ways, a pot isn't going to fix that, but separate CA's might. (might instead require an MCU that is programmed with a "curve" for the throttle response to remap the input to output as needed).

 

[Chalo]

A motor in each wheel should provide enough regen braking force that you'll be using your mechanical brakes less than 1% of the entire time spent braking, which will certainly take a load off of the mechanical or hydraulic brakes.

And it will put that load on the axle nuts and dropouts, which in turn will loosen and cause the axles to spin, rupturing wires and seriously damaging the frame and/or fork.

Until Chinese hub motor manufacturers cure themselves of flatted axles for torque retention, regen braking is chasing trouble with a flashlight and a broom.

 

[amberwolf]

While mostly true, there are a few motors it's safe enough with, like the GMAC (round axle and shoulder-mounted splined torque arm), presumably the Grin All Axle with similar design, and possibly the Heinzmann (I've never held one so don't know exactly what it's design is like; I can tell much easier by holding things than seeing images or plans).

 

[The Toecutter]

And it will put that load on the axle nuts and dropouts, which in turn will loosen and cause the axles to spin, rupturing wires and seriously damaging the frame and/or fork.

Until Chinese hub motor manufacturers cure themselves of flatted axles for torque retention, regen braking is chasing trouble with a flashlight and a broom.

Very true. Adequate regen braking force that doesn't destroy components is still a lot easier to accomplish when the desired braking torque is split between three possible failure points instead of just one.

I've found that modifying the controller's settings for regen braking torque to a max of 30 Nm and no more than 500W will provide tens of thousands of miles of reliable regen. I found it out the hard way after the initial torque settings of 60Nm and 750W made my wheel rock itself loose from the dropouts and lost a nut, and ate away the axle threading. I detuned it to 20 Nm and 250W, and then increased it to 30 Nm and 500W after about 1,500 miles of use. Haven't had a failure since in over 25,000 miles since. But this was for a single motor in the rear.

The Grin all-axle motors I am considering to use on the front wheels have built-in torque arms. My biggest concern with them would be if my steering spindles can handle both regen an acceleration from the front motors, more than anything. They definitely can't handle potholes at speed given that one failed at 40 mph, and I will need to redesign them and fabricate replacements at some point.

1,500W total regen would be plenty for my application. Heavier vehicles loaded with cargo might find it insufficient by itself, although it will take load/stress off of your mechanical braking components. Given the design of the Grin all-axle motors, more than 500W/30 Nm per motor may be reliable, but that is IMO about the limit for the Leafbike 1500W motor's axle design when torquearms on both sides of the axle are present.

It sucks that we can't get a high quality hub motor built to provide hassle-free operation that also uses the best modern technology has to offer. We should be able to have 7 lb switched-reluctance hub motors that can do 5+ kW continuous which also have no cogging torque losses. If I had the equipment, I'd try my hand at building one. Then would come the task of making a control system for it, which would be extremely difficult... and potentially lucrative.

 

[N8!]

A motor in each wheel

well sure, as as long as money is not an issue,

So I am always on the lookout for things that use hoseclamps, and salvage any that I can, especially if it is decades-old equipment as those usually have better clamps than modern stuff does.

Check out the T-bolt hose clamps used in marine wet exhaust systems

eg: W2 Stainless Steel Hose Clamps Supra Exhaust T Bolt Marine Clip intercooler | eBay

 

[Chalo]

We should be able to have 7 lb switched-reluctance hub motors that can do 5+ kW continuous which also have no cogging torque losses. If I had the equipment, I'd try my hand at building one. Then would come the task of making a control system for it, which would be extremely difficult... and potentially lucrative.

Well, that's the issue with switched reluctance, isn't it? I've been reading that it's the best thing since sliced bread since I was in high school in the '80s. But only a few well-financed players have been able to make a go of it.

 

[amberwolf]

Check out the T-bolt hose clamps used in marine wet exhaust systems

eg: W2 Stainless Steel Hose Clamps Supra Exhaust T Bolt Marine Clip intercooler | eBay

I have seen those on things, but I don't think I ever had any to try out. As long as the bands can conform to the surface shapes of whatever they are securing, and don't have to be on round surfaces to tension correctly, then they would work like the more typical hose clamps and do the necessary job, most likely better.

 

[The Toecutter]

well sure, as as long as money is not an issue,

Money is always an issue. It restricts which of the solutions outlined in this thread are viable.

You have a wide range of possibilities to choose from at all price points.

Personally, I think replacing and retaining the hydraulic disc brakes you had(which failed you) and then adding rim brakes plus setting up weak regen via the motor you currently have would be the best course of action if you're looking to maximize redundancy while minimizing expenditure. If the hydraulic brakes are doing less than half the work they used to, they might never fail, and if the rim brakes aren't taking the entire load you're probably never going to experience heat popping a tube or tire.

If you need stronger regen, neptronix could definitely help you with how to go about that. I'm certain he's getting way more regen torque and power than I am, and he's using the same make/model of motor albeit wound differently.

I'm more conservative with my regen settings because I use my vehicle on an almost daily basis and can't risk being out of commission or getting stranded 50 miles from home because something failed. All the more reason I need a 2nd and 3rd ebike, because then I'll be in a better position to experiment more.

 

[lnanek]

Well, that's the issue with switched reluctance, isn't it? I've been reading that it's the best thing since sliced bread since I was in high school in the '80s. But only a few well-financed players have been able to make a go of it.

Search results seem to claim switched reluctance motors exist now, like:

48V/60V/72V 1200W-3000W DC switched reluctance motor SRD motor SRM

48V/60V/72V 1200W-3000W DC switched reluctance motor SRD motor SRM

www.czfound.com

Someone with more knowledge than me would have to look over the table of current/weight/torque there to tell if it is worth it.

Some pages there show a controller too, although precious little details:

https://www.czfound.com/product/products-7-92.html

48V/1200W Switched reluctance motor for electric tricycles and three wheel rickshaw

48V/1200W Switched reluctance motor for electric tricycles and three wheel rickshaw

www.czfound.com

Seems to have double the phase cables compared to the usual brushless controllers in ebikes:

 

[N8!]

Money is always an issue. It restricts which of the solutions outlined in this thread are viable.

You have a wide range of possibilities to choose from at all price points.

Personally, I think replacing and retaining the hydraulic disc brakes you had(which failed you) and then adding rim brakes plus setting up weak regen via the motor you currently have would be the best course of action if you're looking to maximize redundancy while minimizing expenditure. If the hydraulic brakes are doing less than half the work they used to, they might never fail, and if the rim brakes aren't taking the entire load you're probably never going to experience heat popping a tube or tire.

If you need stronger regen, neptronix could definitely help you with how to go about that. I'm certain he's getting way more regen torque and power than I am, and he's using the same make/model of motor albeit wound differently.

I'm more conservative with my regen settings because I use my vehicle on an almost daily basis and can't risk being out of commission or getting stranded 50 miles from home because something failed. All the more reason I need a 2nd and 3rd ebike, because then I'll be in a better position to experiment more.

The design I'm riding on this bike would be rather difficult to regen, this is the kit I built around.
Top 10 best and Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit world's Fastest electric dir . The motor has a ratchet on the drive and the pedals have a ratchet in the BB.

If I were to take the mid-drive off and put a geared hub I can do regen on the rear wheel. I made adjustable track tensioners with torque arms that look a lot like the trackmounts cut off of a wal-mart kids bike. So regen could be done with this bike and it would replace a lot of noisy ratchet action at the pedals.

I really like the dual brakes idea, I've got donor parts that can be welded to my existing parts for mounting the V brakes, if I swap the hydraulics to the smaller ebike and put the cable brakes on the big bike it's possible with existing parts. I put a long front brake line on and had to make an adapter, I threaded some brass plumbing bits and the corrosion between the dis-similar materials is looking very bad. ocean air does that. The existing threaded headset is basura, it's time for a better front fork too.


I forgot to add photo of the bike, so attached is one of track mounts, one of the bike and the corroded hyd fitting.