2019 ditch your rear disc brake ?

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

2019 ditch your rear disc brake ?

Post by cheapcookie » May 30 2019 1:07pm

Hey folks, been looking at a few recent threads recently, still love this stuff.

I see many builds wanting to keep +85% bicycle.

This makes me think...

What is worth keeping from the bicycle world as a result of a mid drive electric conversion/install.

In a hypothetical world, 1 or 2 stage direct driven 6 bolt disc brake mid drive mountain bike, vesc controller.
  • I doubt the usefulness of a rear disc brake (lightweight human) because of powerful front brakes and regen braking
  • I double the usefulness of speeds, derailleur and cassette. Because of powerful top end and low end, added complexity

User avatar
Chalo   100 GW

100 GW
Posts: 7961
Joined: Apr 29 2009 11:29pm
Location: Austin, Texas

Re: 2019 ditch your rear disc brake ?

Post by Chalo » May 30 2019 1:14pm

Why keep the pedals?
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 30 2019 1:15pm

Chalo wrote:
May 30 2019 1:14pm
Why keep the pedals?
Why keep the handlebars, self driving eMTB 2020.

Edit: I go further/faster legally with pedals. With a flat battery, I also go further with pedals.

User avatar
Deafcat   100 W

100 W
Posts: 214
Joined: Aug 13 2015 1:25pm
Location: City of Bridges (in the Canada Rectangle)

Re: 2019 ditch your rear disc brake ?

Post by Deafcat » May 30 2019 7:32pm

Rear brake: redundancy

derailleur gears: kinda super useful on mid-drives, also great redundancy on a hub motor ebike

Not saying you need em, and a bike can be built and ridden with many features deleted... But they all have some value.

flat tire   1 MW

1 MW
Posts: 1903
Joined: Feb 26 2014 12:20am

Re: 2019 ditch your rear disc brake ?

Post by flat tire » May 30 2019 8:02pm

You are right, there is no need for rear disc brake with direct drive and good variable regen.

The only real reason to keep the disc brake is if your motor is too small to handle the additional thermal load generated from regen braking.

It's not needed for functionality with good variable regen, and it's not needed for safety because you still have a mechanical front brake that is responsible for all your stopping force anyway.

AHicks   100 W

100 W
Posts: 296
Joined: Jul 24 2018 10:53am

Re: 2019 ditch your rear disc brake ?

Post by AHicks » May 30 2019 8:29pm

A mid drive with regen braking? How does that work with the clutch in play? Is the rear wheel not free to spin on it's own unless under power? Seems like I have missed something somewhere along the line here...

I do have some direct drive hub regen experience, and based on that, trust me, you still want that rear brake!

User avatar
neptronix   100 GW

100 GW
Posts: 14194
Joined: Jun 15 2010 5:56pm
Location: California refugee living in Utah, USA
Contact:

Re: 2019 ditch your rear disc brake ?

Post by neptronix » May 30 2019 10:31pm

I ran no mechanical rear on my bike with strong regen ( 1kw of regen ). The rear did around 80% of the braking. It was awesome and a very efficient ride.

Image
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

User avatar
Dauntless   100 GW

100 GW
Posts: 8802
Joined: May 29 2010 1:49am
Location: Coordinates: 33°52′48″N 117°55′43″W

Re: 2019 ditch your rear disc brake ?

Post by Dauntless » May 30 2019 10:48pm

Chalo wrote:
May 30 2019 1:14pm
Why keep the pedals?
Why keep the bike? Get a hoverboard.
Any sufficiently advanced technology is INDISTINGUISHABLE FROM MAGIC!
- Arthur C. Clarke

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 31 2019 12:16am

Deafcat wrote:
May 30 2019 7:32pm
Rear brake: redundancy
A lot of things have to go wrong for vesc6 and front hydraulic brakes to go out.
But you're right, I think the biggest failure point is battery, maybe others can confirm.
Although I could put some lights or some other power intensive device on the regen like the ODRIVE.
flat tire wrote:
May 30 2019 8:02pm
You are right, there is no need for rear disc brake with direct drive and good variable regen.

The only real reason to keep the disc brake is if your motor is too small to handle the additional thermal load generated from regen braking.

It's not needed for functionality with good variable regen, and it's not needed for safety because you still have a mechanical front brake that is responsible for all your stopping force anyway.
Puuuurfect
AHicks wrote:
May 30 2019 8:29pm
A mid drive with regen braking? How does that work with the clutch in play? Is the rear wheel not free to spin on it's own unless under power? Seems like I have missed something somewhere along the line here...

I do have some direct drive hub regen experience, and based on that, trust me, you still want that rear brake!
Sooo, right side of bike, AKA human powered side, has single speed freewheel.
Left side of bike has 6 bolt disc mount, on which is installed a sprocket instead.
Flip Flop hub works too, but more gearing down on first stage I guess, or small wheels.

AHicks   100 W

100 W
Posts: 296
Joined: Jul 24 2018 10:53am

Re: 2019 ditch your rear disc brake ?

Post by AHicks » May 31 2019 7:35am

Sorry, this is new to me. Please help me get my head wrapped around this. I get the human powered side. It sounds like nothing is new there.

Would like more info on the brake side. Is there a link to this setup with more details?

The sprocket that has replaced the brake disk is now powered only by the motor? And there is no (free wheel) clutch in play? This motor employs some sort of internal transmission/multi gear ratio setup? Is there a "neutral" to allow the bike to freewheel?

Thanks!

User avatar
Drunkskunk   100 GW

100 GW
Posts: 7202
Joined: Apr 14 2007 11:37am
Location: Dallas, Texas. U.S.A.

Re: 2019 ditch your rear disc brake ?

Post by Drunkskunk » May 31 2019 10:18am

cheapcookie wrote:
May 30 2019 1:07pm
In a hypothetical world, 1 or 2 stage direct driven 6 bolt disc brake mid drive mountain bike, vesc controller.
  • I doubt the usefulness of a rear disc brake (lightweight human) because of powerful front brakes and regen braking
  • I double the usefulness of speeds, derailleur and cassette. Because of powerful top end and low end, added complexity
A 2 stage drive isn't a direct drive. With any kind of freewheel or one way bearing, you have no regen. You need a rear brake.
Also, regen braking is just a drag brake. it will slow you down, but not stop you. While some high end controllers have variable regen, it has no where near the modulation of a rear brake. If you're not also using a rear brake, you're not riding your bike anywhere close to it's potential.
For example, it would be impossible to perform proper trail braking with a Regen brake. Without a rear brake, you will be much slower through a corner.

A 1 speed bike is fine, for a hub motor. I've built several and geared them to be easy to pedal unpowered if I want to.
But this is the non-hub motor forum, and a non hub motor not running through a variable gear set is kind of missing all the fun and the point of a non hub motor. Variable gear trains let you run smaller, lighter motors with a wider torque range and higher efficiency under load.
Buy the ticket, take the ride.
Monster Bike:http://endless-sphere.com/forums/viewto ... =6&t=38667

flat tire   1 MW

1 MW
Posts: 1903
Joined: Feb 26 2014 12:20am

Re: 2019 ditch your rear disc brake ?

Post by flat tire » May 31 2019 11:59am

Drunkskunk wrote:
May 31 2019 10:18am
With any kind of freewheel or one way bearing
Well no shit. I think he has demonstrated an IQ above room temperature and is overwhelmingly likely to know that he can't regen with a freewheel and is instead talking about a high reduction ratio possibly with multiple stages but no freewheels. A 2 stage drive can surely have regen, just make sure the wheel spins the motor under load.
Drunkskunk wrote:
May 31 2019 10:18am
While some high end controllers have variable regen, it has no where near the modulation of a rear brake. If you're not also using a rear brake, you're not riding your bike anywhere close to it's potential.
For example, it would be impossible to perform proper trail braking with a Regen brake. Without a rear brake, you will be much slower through a corner.
You have NO clue. With ASI controller and left hand domino regen throttle, it is extremely easy to modulate the rear brake to balance the bike and trail brake while riding at the limit. The only difference is you cannot lock the rear brake, which is not a problem since if you ride at the limit of traction just hitting it a little bit will have the same effect. It also goes down to basically zero speed.

Really man don't talk out of your ass. Variable regen is a totally awesome solution and that should be overwhelmingly obvious.

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 31 2019 12:10pm

Just wanting to point out, this idea came from riding the bird segway's es2, and many other other e skateboards.

None of them have mech brakes, its all regen, guess what, it might not stop you at 60mph, but 25mph very well.

here is a thread with another person interested in regen middrive
https://endless-sphere.com/forums/viewt ... 6&t=100143

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 31 2019 12:12pm

AHicks wrote:
May 31 2019 7:35am
Sorry, this is new to me. Please help me get my head wrapped around this. I get the human powered side. It sounds like nothing is new there.

Would like more info on the brake side. Is there a link to this setup with more details?

The sprocket that has replaced the brake disk is now powered only by the motor? And there is no (free wheel) clutch in play? This motor employs some sort of internal transmission/multi gear ratio setup? Is there a "neutral" to allow the bike to freewheel?

Thanks!
go have a look at the #25 sprockets section of electricscooterparts, pick 3 items chain, hub sprocket, motor sprocket, hopefully that helps visualize.

Edit: have a look at e skateboard, belt driving wheels, same thing but for a bike :-)

User avatar
E-HP   100 kW

100 kW
Posts: 1217
Joined: Nov 01 2018 9:20pm

Re: 2019 ditch your rear disc brake ?

Post by E-HP » May 31 2019 12:36pm

I haven't read too much on regen with a mid drive motor. Does that mean that braking power would also depend on the gear you're in, so more braking in lower gears and much less in higher?

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 31 2019 1:09pm

E-HP wrote:
May 31 2019 12:36pm
I haven't read too much on regen with a mid drive motor. Does that mean that braking power would also depend on the gear you're in, so more braking in lower gears and much less in higher?
Maybe you are thinking of downshifting a manual car or 4stroke bike?

Or maybe you are referring to gearing ratio ?

Edit: Forget the mid drive thing, the motor can be placed anywhere, the concept I and others are talking about is electric skateboard type drive on one side and human on the other.

User avatar
E-HP   100 kW

100 kW
Posts: 1217
Joined: Nov 01 2018 9:20pm

Re: 2019 ditch your rear disc brake ?

Post by E-HP » May 31 2019 2:09pm

cheapcookie wrote:
May 31 2019 1:09pm
E-HP wrote:
May 31 2019 12:36pm
I haven't read too much on regen with a mid drive motor. Does that mean that braking power would also depend on the gear you're in, so more braking in lower gears and much less in higher?
Or maybe you are referring to gearing ratio ?

Edit: Forget the mid drive thing, the motor can be placed anywhere, the concept I and others are talking about is electric skateboard type drive on one side and human on the other.
Yes, the gear ratio between the wheel and motor affects the amount of regen braking force. Lower gearing, higher braking force.

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 31 2019 3:50pm

E-HP wrote:
May 31 2019 2:09pm
cheapcookie wrote:
May 31 2019 1:09pm
E-HP wrote:
May 31 2019 12:36pm
I haven't read too much on regen with a mid drive motor. Does that mean that braking power would also depend on the gear you're in, so more braking in lower gears and much less in higher?
Or maybe you are referring to gearing ratio ?

Edit: Forget the mid drive thing, the motor can be placed anywhere, the concept I and others are talking about is electric skateboard type drive on one side and human on the other.
Yes, the gear ratio between the wheel and motor affects the amount of regen braking force. Lower gearing, higher braking force.
This is correct, although motor choice, controller choice, load/battery choice, is probably more critical than gearing ratio.

markz   100 GW

100 GW
Posts: 9421
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: 2019 ditch your rear disc brake ?

Post by markz » May 31 2019 7:00pm

Or a moped/motorcycle/harley/scooter
Dauntless wrote:
May 30 2019 10:48pm
Chalo wrote:
May 30 2019 1:14pm
Why keep the pedals?
Why keep the bike? Get a hoverboard.

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » May 31 2019 7:03pm

markz wrote:
May 31 2019 7:00pm
Or a moped/motorcycle/harley/scooter
Dauntless wrote:
May 30 2019 10:48pm
Chalo wrote:
May 30 2019 1:14pm
Why keep the pedals?
Why keep the bike? Get a hoverboard.
...GET OUT OF HERE WITH THAT ICE MENTALITY. :lol: :lol: 8)

markz   100 GW

100 GW
Posts: 9421
Joined: Jan 09 2014 11:38pm
Location: Alberta Canada

Re: 2019 ditch your rear disc brake ?

Post by markz » May 31 2019 11:25pm

You mean this kind of ice.
cheapcookie wrote:
May 31 2019 7:03pm
ICE

User avatar
DanGT86   10 kW

10 kW
Posts: 786
Joined: Sep 06 2012 9:18pm
Location: Saint Louis MO

Re: 2019 ditch your rear disc brake ?

Post by DanGT86 » Jun 01 2019 12:06am

I have not ridden a bike with variable regen but I have serious doubts about riding without a mechanical lever actuated rear brake for a variety of reasons:

I like the modulation of regular brakes and the ability to lock up the wheel for trials type riding. If high end variable regen matches modulation of my disks but wont lock the wheel then I'm not giving up the brake.

Mechanical Braking is not limited by the thermal capability of the motor. I know brakes get hot too but they are designed for the job and I can feel their behavior change as I ride. Motor drive seems way more likely to surprise you when tasked with brake duty.

Handlebar brake levers are always in the same place in my hand regardless of terrain. Having a twist grip in both hands seems frightening in rough spots. With a twist throttle there is now zero static grip on the bars.

Regen on a mid drive requires a chain without spring tensioners. This is a serious engineering challenge on full suspension mid drive bikes. It also transfers the chain slack abruptly even on direct drive straight chain runs. I dont like that feeling especially in delicate traction situations. I believe the impact and forces acting on the parts of the drivetrain are worse than under acceleration and will wear parts faster. Also that chain slap really effects the modulation. With a mechanical brake you can keep the slack out of the chain through slick stuff by slightly dragging the brake.

peters   1 kW

1 kW
Posts: 304
Joined: Oct 20 2012 11:46pm
Location: Hungary

Re: 2019 ditch your rear disc brake ?

Post by peters » Jun 01 2019 12:30am

Electronics can't be considered as reliable as a mechanical brake. Without redundancy many components of the circuit are in series in the reliability model that means any of them fail you lose regen. That includes battery, bms, fuse, controller, components of the controller, connectors, firmware, regen throttle, wiring, motor, hall sensors and others.
I don't know the automotive standards, but sure that relying on regen only wouldn't be in compliance with them. Maybe ok for "toys" like skateboard and segway, but not for vehicles.

cheapcookie   100 W

100 W
Posts: 185
Joined: Aug 02 2014 10:34pm
Location: Earth

Re: 2019 ditch your rear disc brake ?

Post by cheapcookie » Jun 01 2019 12:36am

markz wrote:
May 31 2019 11:25pm
You mean this kind of ice.
cheapcookie wrote:
May 31 2019 7:03pm
ICE
Not sure why u care bout meth in kangaroo land, when there's literally a planet of it in NorthAmerica
DanGT86 wrote:
Jun 01 2019 12:06am
I have not ridden a bike with variable regen but I have serious doubts about riding without a mechanical lever actuated rear brake for a variety of reasons:

I like the modulation of regular brakes and the ability to lock up the wheel for trials type riding. If high end variable regen matches modulation of my disks but wont lock the wheel then I'm not giving up the brake.

Mechanical Braking is not limited by the thermal capability of the motor. I know brakes get hot too but they are designed for the job and I can feel their behavior change as I ride. Motor drive seems way more likely to surprise you when tasked with brake duty.

Handlebar brake levers are always in the same place in my hand regardless of terrain. Having a twist grip in both hands seems frightening in rough spots. With a twist throttle there is now zero static grip on the bars.

Regen on a mid drive requires a chain without spring tensioners. This is a serious engineering challenge on full suspension mid drive bikes. It also transfers the chain slack abruptly even on direct drive straight chain runs. I dont like that feeling especially in delicate traction situations. I believe the impact and forces acting on the parts of the drivetrain are worse than under acceleration and will wear parts faster. Also that chain slap really effects the modulation. With a mechanical brake you can keep the slack out of the chain through slick stuff by slightly dragging the brake.
Nobody said you couldn't lock up wheels up with regen.
In a nutshell, the same way ICE unconsciously encourages you to speed away from a green light.
Regen, encourages you to prepare, slow down, and engage a corner half a mile away.
peters wrote:
Jun 01 2019 12:30am
Electronics can't be considered as reliable as a mechanical brake. Without redundancy many components of the circuit are in series in the reliability model that means any of them fail you lose regen. That includes battery, bms, fuse, controller, components of the controller, connectors, firmware, regen throttle, wiring, motor, hall sensors and others.
I don't know the automotive standards, but sure that relying on regen only wouldn't be in compliance with them. Maybe ok for "toys" like skateboard and segway, but not for vehicles.
Again, above we talked about how much has to fail to be down to so little
But as a generality, I know a few EEngineers on this forum that would like to disagree

User avatar
DanGT86   10 kW

10 kW
Posts: 786
Joined: Sep 06 2012 9:18pm
Location: Saint Louis MO

Re: 2019 ditch your rear disc brake ?

Post by DanGT86 » Jun 01 2019 8:28am

cheapcookie wrote:
Jun 01 2019 12:36am
Nobody said you couldn't lock up wheels up with regen.
In a nutshell, the same way ICE unconsciously encourages you to speed away from a green light.
Regen, encourages you to prepare, slow down, and engage a corner half a mile away.
flat tire wrote:
May 31 2019 11:59am
You have NO clue. With ASI controller and left hand domino regen throttle, it is extremely easy to modulate the rear brake to balance the bike and trail brake while riding at the limit. The only difference is you cannot lock the rear brake, which is not a problem since if you ride at the limit of traction just hitting it a little bit will have the same effect. It also goes down to basically zero speed.
User Flat Tire just made that very statement as part of a glowing review on the benefits of variable regen. I was basing my statement on that since again I have not tried variable regen. I have used regular regen with chain driven mid-drive using a sprocket on the disk brake flange. That informs most of the points I mentioned previously.

As for preparing to brake early, its not always up to you as the rider. If you are making a leisurely cruiser for flat ground and not on public roadways or public paths then the front brake might be adequate. If you ride somewhere where joggers wear headphones, cars behave unpredictably, trails get wet, leaves fall on the ground, or any really technical terrain, I think rear brakes are a must.

Since brakes come on most bikes anyway I would suggest you design around using them and then take them off if they annoy you.

Also, if you plan to mess with wheelies I think a rear brake is a must. :D

An additional engineering challenge is chain management. The slack side of a chain without regen can have very light duty chain idlers like a derailleur. The jockey wheels are only controlling the weight of the chain. With regen they will get the full load of the tension if the chain so they better be strong structural components with good bearings. Say goodbye to cheap bike parts in that application.

Post Reply