Current Avinox MG Prototype Bikes Don't Support Battery Regen

[slickrock]

All the current announcements for the Avinox MG (and the Gobao XP1 motor as well), officially and through influencers, tout that their ECVT design can support battery regenation, which is actually the case due the inherent capabilities of ECVT Hybrid Drive design. However, I just realized with all these Avinox MG prototype bikes, in their current design form, battery regeneration would NOT be possible.

Not only do you require a fixed wheel hub (which is possible on these bikes) with the belt/chain always spinning, but the mere presence of chain tensioner disqualifies reverse tension on the belt/chain that is essential to battery regeneration. I forgot about this because I've had the Rivian/ALSO TM-B on my mind for a while now:

Instead you need to have a concentric wheel path rear suspension design (or just a plain hardtail like with a city bike). This design requires no tensioner (awesome in its own right) where the chain/belt can be at full tension always, and more importantly allow reverse tension with forces operating in the opposite direction from belt/chain rotation when the motor acting like a generator. The TM-B beautifully pulls this off because the drive axle is well above the pedal axle with the drive axle right behind the single pivot, which pulls off a HP design without an idler. True, it's pedal-by-wire instead of ECVT, but that doesn't matter. All that matters is the concentric wheel path (which exhibits zero chain growth) and motor that can act as a generator.

With the current crop of ECVT motor designs from Avinox and Gobao the pedal and drive shafts are concentric, so it will be quite difficult, if not impossible, to get a concentric pivot to surround the BB to get a concentric wheel path, like with the faux-bar suspension of the Lenz Milk Money (I own one, BTW):

Besides, having concentric BB pivot will kinda kill anti squat features. Instead you would need some kind of dual chain high-pivot design, similar (but not the same) to Pivot's downhill bike to get the the kind of anti-squat Enduro folks are after:

Keep in mind though the DW6 design used by pivot (seen above) still does not have a concentric wheel-path, so a tensioner would still be required a but with a true single-pivot arc. In this case that chainstay pivot would either need to be co-located with fixed idler or directly in front of it.

Technically, a ECVT motor could be designed to have non-concentric pedal and drive shafts, similar to the original Effigear gearbox design:

It would be awesome if some future generation ECVT motor would have a layout like the Effigear: you get a real HP rear suspension where you can finally ditch the lameness of belt/chain tensioner as well as fully open up battery regeneration capabilities.

As an aside, what I said about the above Avinox prototypes not supporting battery regeneration is a bit a of lie. You could always pedal the bike to charge the battery (mechanically allowable with ECVT), but I'm sure that's not what customers have in mind when they hear the term "battery regen".

BTW, Hub-based MGUs don't have this constraint because the regen forces happens inside the hub.

 

[Brawwp]

I think in Rob’s interview with Avinox they mentioned adding braking battery Regen.

My question is how much does it actually even do? I wouldn’t think very much at all. Like would the added nuances and weight be worth the amount it’d give back?

 

[TimC7]

I don't see lack of regen being a show stopper, be nice to have for free but an 800Wh battery is more than enough for most days.

 

[Astro66]

Regen brakes would create some complexity that a EMTB just doesn't need. The brakes would need to interface with the motor, unless everytime you stopped pedalling the bike immediately went into regen, which would be unfavourable.

Having the chain or belt run continuously would also create a safety issue, requiring guarding, like on a motorbike.

I don't think the juice is worth the squeeze.

 

[RustyIron]

I don't see lack of regen being a show stopper

Right? Who cares about regen? Maybe it would be helpful for commuters who are afraid to go fast on downhills, but I don't think it would be all that great for mountain bike riders. But the discussion is moot, since regen isn't even available on mountain bikes.

 

[slickrock]

Regen brakes would create some complexity that a EMTB just doesn't need. The brakes would need to interface with the motor, unless everytime you stopped pedalling the bike immediately went into regen, which would be unfavourable.

Having the chain or belt run continuously would also create a safety issue, requiring guarding, like on a motorbike.

I don't think the juice is worth the squeeze.

Agreed, but that's exactly how the TM-B works. Regen is part of their ABS braking system and it works wonderfully - I mean crazy good. The very best braking system I've ever experienced on an EMTB. The TM-B also has a belt guard as you alluded. That may seem like a lot of hoops to through to get to true battery regen, but actually seeing in action with TM-B hints to possible ECVT regen future for EMTB. It's just not a feature that can be had easily.

 

[slickrock]

I don't see lack of regen being a show stopper, be nice to have for free but an 800Wh battery is more than enough for most days.

Well if you can reclaim like 25% of battery capacity then a 600WH would have the same range as 800WH. That's a lot of poundage taken off your bike, not to mention improved handling with a small battery.

 

[Ndanger]

Speaking of regen
... the thumb powered perpetual motion machine where you attach a light dynamo to the bottom of the seat. As you drop your seat post when you go downhill, it will attach to the rear tire, power the dynamo, and recharge your battery.

As you can tell, I ave way to much time waiting at a train

 

[Mikerb]

Ecvt motors are for commuters. Just as in cars I cannot see them being effective for "sporty " use. On a personal level I dont want an auto emtb thanks

 

[Astro66]

Regen is part of their ABS braking system and it works wonderfully - I mean crazy good

Riders are very particular about their braking on mountain bikes, because brake feel can impact your ability to descend quickly. Having the brakes interfacing with the motor, means that you aren't going to be able to just change braking systems easily.

I could see it working well in a commuter bike. But just not an EMTB.

Whilst still significant. I cannot see you getting back more than about 10% of your battery in regen, mostly due to you will only regen when descending, then factor in the efficiency of regen braking. Looking at a best case scenario. You only descend 50% of the ride. Then of that 50%, if you got 50% efficiency. That's a best case of 25%.

When brake regen efficiencies are around 20-50% and you aren't going to brake the whole time you are descending. You can see why I think the return will be so low.

Regen braking saves the most amount of energy when you are stop-starting, which is not an EMTB ride characteristic.

 

[slickrock]

Ecvt motors are for commuters. Just as in cars I cannot see them being effective for "sporty " use. On a personal level I dont want an auto emtb thanks

Then you've probably not heard that CVT was banned for Formula One racing because it created too much of a driving advantage.

 

[DylanJM]

Ecvt motors are for commuters. Just as in cars I cannot see them being effective for "sporty " use. On a personal level I dont want an auto emtb thanks

It doesn't have to be auto all the time. It can be configured with "gears".

 

[Astro66]

Ecvt motors are for commuters. Just as in cars I cannot see them being effective for "sporty " use. On a personal level I dont want an auto emtb thanks

And a derailleur is sporty ?

A ECVT can exactly mimic the manual shift pattern of a derailleur, except it will be silent and almost instant shifting. It can also shift when completely stationary, or under 100% load, creating almost no wear.

There is no downside.

 

[slickrock]

Riders are very particular about their braking on mountain bikes, because brake feel can impact your ability to descend quickly. Having the brakes interfacing with the motor, means that you aren't going to be able to just change braking systems easily.

I could see it working well in a commuter bike. But just not an EMTB.

Whilst still significant. I cannot see you getting back more than about 10% of your battery in regen, mostly due to you will only regen when descending, then factor in the efficiency of regen braking. Looking at a best case scenario. You only descend 50% of the ride. Then of that 50%, if you got 50% efficiency. That's a best case of 25%.

When brake regen efficiencies are around 20-50% and you aren't going to brake the whole time you are descending. You can see why I think the return will be so low.

Regen braking saves the most amount of energy when you are stop-starting, which is not an EMTB ride characteristic.

Juice worth the squeeze angle is defensible on it own for battery regen. But when combined with ABS braking, it's insanely good when done right. If anyone ever gets a chance to demo a TM-B, you will know exactly what I mean. it really worked well on the Sea Otter MTB test trails. The modulation was transparent in transition from regen to actual braking and stopping power was intense but in a fully controllable way. An ECVT with concentric rear suspension, free of a belt tensioner, along with battery regen on a 600wh battery with full ABS would an ideal bike for me.

 

[Mikerb]

And a derailleur is sporty ?

A ECVT can exactly mimic the manual shift pattern of a derailleur, except it will be silent and almost instant shifting. It can also shift when completely stationary, or under 100% load, creating almost no wear.

There is no downside

Yes I agree the derailleur and cassette arrangement is from the arc and I much prefer the potential of an MGU with belt drive. I just doubt that for mtb use cvt or ecvt is the right technology. In the auto industry CVT has been problematic ....ecvt as used in hybrids much more reliable but is limited in terms of more active/sporty driving.

 

[Mikerb]

It doesn't have to be auto all the time. It can be configured with "gears".

Yes I know but then becomes complex in terms of software

 

[Mikerb]

Then you've probably not heard that CVT was banned for Formula One racing because it created too much of a driving advantage.

What determines the optimum gear is very different on a formula one track than on a mtb trail.

 

[slickrock]

Yes I agree the derailleur and cassette arrangement is from the arc and I much prefer the potential of an MGU with belt drive. I just doubt that for mtb use cvt or ecvt is the right technology. In the auto industry CVT has been problematic ....ecvt as used in hybrids much more reliable but is limited in terms of more active/sporty driving.

So what's the alternative? Good old clunky Pinion gearbox? We've seen where's that led the market. Pedal-by-Wire might be the only other alternative I can think of.

 

[Mikerb]

So what's the alternative? Good old clunky Pinion gearbox? We've seen where's that led the market. Pedal-by-Wire might be the only other alternative I can think of.

Yes mesh gears mgu design has some defects but they can be resolved. It probably needs the parnership of a leading bike brand and an automotive engineering company to do that.

 

[Mikerb]

You also have to question why the leading brands did not include mgus into their ranges of bikes. The same reasons may apply to adoption of ecvt mgus.

 

[Fangs2k]

So what's the alternative? Good old clunky Pinion gearbox? We've seen where's that led the market. Pedal-by-Wire might be the only other alternative I can think of.

There doesn’t need to be an alternative does there? The derailleur and cassette etc has served cycling well for decades and is simple, effective and cheap. People don’t have to buy SRAM XO groupsets at the end of the day.

I think like everything in cycling, there’s room for all kinds of difference, why can’t MGUs exist alongside the current default solutions?

I know the answer, and it’s got little to do with solving problems but everything to do with keeping factories busy and retailers tills ringing.

I’m not a luddite, I’m interested in MGUs but not because I struggle to be in the right gear at the bottom of a descent or start of a climb or even because the derailleur is ‘ugly’. Mind you, some of those belt and tensioner setups don’t look great either!

I’ve had a bit of time on one of my brothers e-commuter bikes, a Leonardo with a Gen3 Zehus hub motor with regen (yes, he lives in London and has that kind of moustache and lifestyle!) and it’s a cool thing for the cycleways of that city.

He reckons he can add about 10% of battery range just by normal braking regen, without any back pedalling. Doesn’t sound a lot to translate into much extra range for an EMTB even if the technical challenges to enable it can be overcome with a full suspension bike.

I’m often reminded of the legendary engineer and designer Colin Chapman whose mantra was always ‘simplify, then add lightness’. It feels like MGUs are doing neither, replacing one set of complexities with another.

I’ll be watching with interest though, to see how each of these early concepts develop over time.

 

[Sherman]

I guess regen would just suck the fun out of downhills (like drag). Like it was mentioned, it would probably mess with braking, and precise brake control is everything in MTB. Plus, the energy return wouldn't even be that impressive—maybe 10–20 Wh per 100 vertical meters.

It might make sense for cruising down alpine roads.

 

[Ndanger]

Speaking of alpine decents my arms hands and brakes would be delighted to sign up for regen.

So the question becomes how excited would you be with hub motors since mid drive and freewheel are not an option.

 

[TheKaiser]

Speaking of alpine decents my arms hands and brakes would be delighted to sign up for regen.

So the question becomes how excited would you be with hub motors since mid drive and freewheel are not an option.

Hub motors have always been way more popular on road and commuter ebikes, whereas mid-drive has seemed to be the preferred solution for EMTBs. I have never been totally clear why, other than hub drives will add a lot of unsprung weight.

 

[DylanJM]

Hub motors have always been way more popular on road and commuter ebikes, whereas mid-drive has seemed to be the preferred solution for EMTBs. I have never been totally clear why, other than hub drives will add a lot of unsprung weight.

Middrive can fully utilise the gears of a mtb. Hub motor can't

 

[Powerslider]

To me the big issue is the false/misleading claims.