Should e bikes have gearboxes?

Should E Bikes have gearboxes?

  • Yes

    Votes: 69 71.1%
  • No

    Votes: 19 19.6%
  • Undecided

    Votes: 9 9.3%

  • Total voters
    97

FlowDough

Active member
Nov 11, 2018
41
23
North America
Here's an overview on gearboxes:


The primary reason gearboxes haven't seen widespread use on regular bikes is because of the added weight and the efficiency loss in the drivetrain. Neither one of those concerns is as much of a detrimental factor on a heavier e bike with a motor, so I'm surprised more manufacturers haven't tried them on e bikes. But most e bike manufacturers seem to be obsessed with making their e bikes look like regular bikes, so adding a gearbox makes that harder. Most gearbox bikes actually look like they already have an e bike motor.

But I think a gearbox would be worth it for many e bike riders who want a more sealed drivetrain, more reliable shifting, and less mechanical failures related to the rear derailleur.

Shimano seems to be leading the way with its internal gearbox patent for e bikes, but we've only seen drawings so far. Mubea has made one, and drivetrain maker Revonte has developed a mysterious automatic transmission gearbox integrated into an e bike motor. The advantage of the Shimano system is that the gearbox is centrally ocated near the motor for a more balanced bike, similar to the old Honda gearbox DH bike. If you want an internal drivetrain for your e bike right now, Kindernay might be the best option but it currently requires 2 shifters so it will interfere with a dropper post.

I wonder if we might see single speed e bikes with more power levels rather than gears in the future, along with some type of on the fly adjustable torque? What would be your dream e bike drivetrain?

As someone who has had rides ended from having the vulnerable rear derailleur destroyed, I would like to see gearboxes happen on e bikes even if they are a little heavier, bigger, and slightly less efficient. It also seems like with the higher speed of e bikes riders are more likely to go slightly off-trail and get sticks and grass in the rear derailleur, causing damage or the shifting to skip around.


I also like the idea of not having to lube or replace the chain so frequently, and bikes look better without derailleurs.

What are your thoughts on gearboxes for e bikes?
 

Slowroller

Well-known member
Founding Member
Jan 15, 2018
494
496
Wyoming
The main drawback is the significant cost it adds. Most people don't appreciate the difference, so it'll be a while before a major manufacturer risks a product line speccing them. As motors keep getting more powerful, they'll become more necessary to keep from burning through drivetrains.
 

KeithR

Well-known member
Jul 1, 2020
679
610
Blyth, Northumberland
As motors keep getting more powerful, they'll become more necessary to keep from burning through drivetrains.
Or things will go in completely the other direction: electric cars and electric "motorbikes" like the Zeros have no gears at all - just gobs of torque at any and all speeds.

I can easily see ebikes going the same way: a strong chain (or maybe better, a belt); a good, tough chainring; a single sprocket; and intelligently delivered variable torque managing the power delivery.
 

Minikeum

Member
Oct 29, 2020
23
6
Switzerland
Effigear is about to release a “solution for e-mobility” in 20 days:

as a reminder, they designed a gearbox, mounted on Cavalerie bikes, that compete for a few years at world cup DH level through team Dorval.

Worth checking what they come up with. Maybe just a city bike. Maybe an eMTB.
it was supposed to be released at eurobike but that got canceled.

EDIT: that’s what they were working on lately, but I believe the e-mobility project took priority:
a380a7_4e39a05f36964a5cb004a6befc6cfef0~mv2_d_3719_2480_s_4_2.webp
 
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DrStupid

E*POWAH Elite World Champion
Patreon
Jul 10, 2019
1,464
2,128
Pleasureville Ky
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The industry doesn't want gearboxes.if it wanted them, we would have them.

It's a hard problem for bicycle standardization to encompass, just like mid drives are.

Standards seem to be a big deal in the bicycle industry. I'm not sure why this is, to be honest?, but I think this is what's holding gearboxes back.

I'd buy one, but my price point is 7K.


Ebike motors dont need gearboxes, ebike riders need gear boxes. Take the cranks off, replace them with pegs, and abra-ka-pocus. No tranny needed. It's called a sur-Ron.
 
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Waynemarlow

E*POWAH Master
Dec 6, 2019
1,054
868
Bucks
The least loss of efficiency in gearboxes are CVT gearboxes, which is basically a type of flexible steel belt driving 2 variable diameter pulleys. Honda, Toyota Subaru all market them heavily abroad where more auto boxes are sold than the stick shift we all love in the U.K. Yes they need computer control but then so does the electric motor driving them, why not combine the two ?

 

GrandPaBrogan

⚡ eGeezer ⚡
Oct 5, 2019
1,329
2,068
New Zealand
I voted NO... that's no to gearboxes... but that doesn't mean I voted to keep the derailleur either.

Below is the 2019 (Honda?) Mugen Shinden... developed and raced specifically for the Isle of Man ZeroTT format.

Screen Shot 2020-11-27 at 11.50.07 AM.png


“It averaged 121mph over the flying TT Zero lap. It did 176mph through the speed trap, which was 3mph hour quicker than the 600cc SuperSport bikes. The performance is up there. You take a little bit of a weight penalty with the electric powertrain, but with continued development, we'd think that would come down over the years.”
"The bikes have no clutch and no gears, meaning it’s a twist and go experience, and not at all comparable to combustion powered super bikes."
(Full article, here: The Mugen Shinden is an all-electric Isle of Man TT conqueror)
-

It is my understanding that electric motors are highly efficient with FULL torque available from 1rpm all the way up to a bazzilion rpm , attainable because there no reciprocal moving parts and hardly any friction losses (with the exception of the drive train itself).
I don't believe the technology is quite here yet to do away with the derailleur (AND gearbox)... but it also doesn't help that the bicycle industry by enlarge is a deeply traditional if not a highly political domain. I wouldn't be surprised if it had never occurred to them yet that an electric motor doesn't actually need a gearbox to micro-manage torque output - IF (and that's a big if) the new-gen pedal assist motors are designed to be run that way. The main issue for a bicycle is "cadence-management" hence the set-ups we have currently... but there might be a way to achieve this by software programming without utilising mechanical means.

I can imagine that an eMTB without a derailleur would have a bigger battery and bigger motor. At this point in time, the weight savings by removing the complexity of a shifting drivetrain may not be enough to offset the added weight of a bigger motor and battery... but, who knows given time. I'm curious which brand will be the first to give it a shot... it might be a complete outsider to get in there and give the old-guard a wake up call.
.
 
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TorAtle

Member
Aug 4, 2018
86
81
OSLO
The main issue for a bicycle is "cadence-management" hence the set-ups we have currently... but there might be a way to achieve this by software programming without utilising mechanical means.
Software programming won't help the rider which is stuck in a single gear without a gearbox or derailleur. Unless you would detach the pedalling motion from the drivetrain and just use that to generate power to drive the electric motor. Possible, I guess, but the riding experience would suffer greatly.
 

Zimmerframe

MUPPET
Subscriber
Jun 12, 2019
13,771
20,455
Brittany, France
It is my understanding that electric motors are highly efficient with FULL torque available from 1rpm all the way up to a bazzilion rpm , attainable because there no reciprocal moving parts and hardly any friction losses (with the exception of the drive train itself).
There's quite an interesting explanation here from Mate Rimac about motor torque & Power and how that relates to torque for acceleration - "Wheel Torque" :

With some introduction as to why they're talking about it :

27 minutes into Nico & Mate's Video

Straight into the explanation 2 minutes later for the really impatient....

29 ish minutes in
 

DrStupid

E*POWAH Elite World Champion
Patreon
Jul 10, 2019
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Pleasureville Ky
We humans with legs, have limited power bands. We can only output an reasonable amount of power over maybe 150 rpm range, say 0-150 rpm. The motors range is say 0-30,000 rpm. A ratio will be required to connect them, hence a transmission of some sort.

Even a generator motor coupled system using switchable pole motors will require electronic switching, (virtual transmission) to perform the ratios.
 
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GrandPaBrogan

⚡ eGeezer ⚡
Oct 5, 2019
1,329
2,068
New Zealand
Software programming won't help the rider which is stuck in a single gear without a gearbox or derailleur. Unless you would detach the pedalling motion from the drivetrain and just use that to generate power to drive the electric motor. Possible, I guess, but the riding experience would suffer greatly.
Correct. Good point for discussion.

Most motors designed to be used in conjuction with derailleur systems are high RPM brushless motors. Hence there is always some sort of internal mechanical reduction involved - either by gear or belt (and belt failure in particular has caused so much grief with some motors). To use this type of motor to attain a pure “electronic” cadence replicator would have impractical disadvantages. Possibly the main thing would be the feeling of ambiguity in pedal/crank engagement… there would be a major disconnect feeling between the rider and bike. The other major downside is if the battery runs out (or if electronic gremlins arise), may mean that the rider can’t ride the bike out of the trails. One might be able to engage a 'drive pin' to reconnect the chainring to the cranks mechanically for this purpose, but then the remaining mechanical drive arrangement would be in one gear ratio. In saying that, we currently put-up with similar instances with adhoc remedies with broken derailleur scenarios anyway.

However, it’s a natural tendency to interpret new ways of doing things with current methodology. It appears that a high speed electric motorcycle with a throttle and no clutch and no gears is a more viable endeavour - than to de-tune or deconstruct the advantages of electric motors in order to fit within the limitations of only partially assisting human cadences.

Cadence reintegration is going to be key. Maintaining the bond between rider and machine will be the biggest hurdle. Seems impossible right now I know, but if my Dad was still alive he would say I was crazy if I told him that I can watch streaming movies from my mobile phone. ?
.
 

GrandPaBrogan

⚡ eGeezer ⚡
Oct 5, 2019
1,329
2,068
New Zealand
We have a gear system already and its located in the worst possible space imaginable. To put it in a box, and locate it in a better space, would be an improvement.
The humble derailleur is not a gear system... it's a chain and sprocket system, very light and about 98% efficient if I'm not mistaken.

Gearboxes on the other hand have gear clusters where roughly one small tooth engages at any one time and so gears need to be made wide enough and hard enough to handle the torque applied. It gets heavy very quickly when more speeds are required. Friction losses are quite high too. From just a quick google check, depending on the ratio of just one gear combination, the efficiency can be as low as 80% and even lower down to 40%. A basic rule that designers use for spur gears is a 10% loss per engagement... so if three or four gears engage in order to achieve the drive ratio desired then it gets bad real quick. Not to mention that it still has to come out somewhere and engage the chain drive anyway. It needs an enclosed oil bath and oil seals and is not user serviceable like a chain drive is. So gearboxes have a lot of downsides.

On a clockwork bike where human power is very limited, a gearbox isn't practical. However, with motor pedal assist it might be. It would drain the battery faster though compared to a bike with a derailleur, so the mileage per battery charge will be affected... but definitely viable. (y)
 

GrandPaBrogan

⚡ eGeezer ⚡
Oct 5, 2019
1,329
2,068
New Zealand
There's quite an interesting explanation here from Mate Rimac about motor torque & Power and how that relates to torque for acceleration - "Wheel Torque" :

With some introduction as to why they're talking about it :

27 minutes into Nico & Mate's Video

Straight into the explanation 2 minutes later for the really impatient....

29 ish minutes in
I saw a documentary about various ZeroTT bikes being designed and developed for the Isle of Man. It would appear that the power to weight ratio and the wind drag coefficients in motorbikes vs cars has a big bearing on the torque parameters you pointed out above.

Getting sufficient wheel torque from these eRockets isn't an issue. In fact their problem is that they're getting too much torque. They actually have to use software to limit or 'sculpt' the wheel torque so as not to exceed tyre traction - otherwise it's just a 'donut-fest' or a drift bike extravaganza. The successful race bikes are ones where the acceleration graphs have been written correctly. It's a programmer's nightmare apparently... if they go for maximum power and performance delivery, the batteries won't last the race. If they go for mileage, then they get easily overtaken by other bikes.
 

wrayb

Member
May 9, 2019
112
55
North Carolina
I see 2 very different types of Emtb groups. Mountain bikers who ride mountain bike trails and motorcycle riders who want to ride Emtbs on motorcycle trails. The standard derailleur is fine for mountain bike trails but fails for the more varied motorcycle trails with lots of debris and mud. Personally I would like to see Emtbs designed differently for the two different markets. Motorcycle riders need a type I Emtb without a derailleur and sealed against water ingress. Design the motor/transmission like a motorcycle. It works.

Specialized has the right idea with the SL for mountain bikers (although these bikes should be less expensive than the Levo). They could totally redesign the Levo to be watertight with a mid-motor-transmission. There is a very lucrative market for an Emtb that can be ridden anywhere (and you can actually wash the mud off without worrying about destroying the electronics).
 
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Oldcrank

Member
Jan 5, 2020
67
54
Albuquerque NM
Gear box ! YES ‼️
see:
&
&
&

enjoy!
 

Slowroller

Well-known member
Founding Member
Jan 15, 2018
494
496
Wyoming

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