'lightest.bike' 1.7kg 1000w mid drive

[raylo32]

I don't nerd out on all that stuff. I just ride. But for sure, I am spun out and that top speed is purely on throttle. IIRC pedaling 80 to 90 RPM might get me 25-28 MPH, IIRC. I am a aging hard core cyclist so I can still pedal pretty fast, well over 100 RPM for a time, but that is not enough to keep up with the motor with the 42t chaining. I also have a 50t chaining in my parts box but have not tried it yet. It may not fit on this frame.

You can ask those questions about amps in the Photon thread and I believe they may be some folks who can answer.

Assuming that is on 52V? Can you share the watts/amps being pulled at those speeds?

And semi-related, can you share the cadence/rpm/cycling comfort and your chainring size? My Lightest motor is outpacing me at 52V.

 

[nervagon]

I don't nerd out on all that stuff. I just ride. But for sure, I am spun out and that top speed is purely on throttle. I am a aging hard core cyclist so I can still pedal pretty fast, well over 100 RPM for a time, but that is not enough to keep up with the motor.

what is your wheel size and chainring?

 

[nervagon]

Thanks, I did see the post.

It would have been good for Bikee to warn buyers in advance that 300 miles of break-in would be needed to make the motor noise less obtrusive. Wouldn't it be better for Bikee to factory run the motors under load prior to shipping for a time and speed equivalent to 300 miles?

Bikee claim that 2 negatives about this motor get better over time: motor drag with no assist, and loud motor noise. If any end users have put hundreds of miles in on their Lightest kit, it would be great to get confirmation on that.

 

[neptronix]

5 minute burst speed doesn't matter that much. I'm more interested in knowing what speed i can maintain thermal stasis.
It's probably in the low 30mph speeds.

I'll find out!

 

[nervagon]

5 minute burst speed doesn't matter that much. I'm more interested in knowing what speed i can maintain thermal stasis.
It's probably in the low 30mph speeds.

I'll find out!

I do not ever need to go over 30mph on a bicycle. But sustained 28-30mph is desirable.

 

[neptronix]

I'd like to go 25-35mph but i'm not willing to blow my motor/invalidate the warranty yet, 30mph will do, lol

 

[Pilot Engineer]

Bikee claim that 2 negatives about this motor get better over time: motor drag with no assist, and loud motor noise. If any end users have put hundreds of miles in on their Lightest kit, it would be great to get confirmation on that.

@nervagon the motor should have no drag with no assist

 

[nervagon]

@nervagon the motor should have no drag with no assist

It does drag. The pinion gear doesn't spin freely and I'm pretty sure I'm not the first to comment on this.

 

[nervagon]

Mine is the same as this person's.

Edit, I'll also add that I don't think a proper cyclist would allow a pulley in their drive train that is this gummed-up.

 

[Chalo]

I'll also add that I don't think a proper cyclist would allow a pulley in their drive train that is this gummed-up.

You'd think that! But some folks prefer not to dwell on things that aren't making any problems yet.

I've been surprised many times how much breading had accumulated on my derailleur pulleys since the last time I bothered to notice.

 

[nervagon]

You'd think that! But some folks prefer not to dwell on things that aren't making any problems yet.

I've been surprised many times how much breading had accumulated on my derailleur pulleys since the last time I bothered to notice.

I don't think the video is really doing it justice then. There is supposed to be a freewheel in there, but it doesn't feel like there is one. It feels like you are turning over the entire rotor.

 

[Chalo]

I don't think the video is really doing it justice then. There is supposed to be a freewheel in there, but it doesn't feel like there is one. It feels like you are turning over the entire rotor.

Yeah, the video is definitely showing mechanical or maybe magnetic cogging and not only filth and entropy. I would not be pleased by that, but when the motor is pulling I would not feel it either.

 

[nervagon]

Yeah, the video is definitely showing mechanical or maybe magnetic cogging and not only filth and entropy. I would not be pleased by that, but when the motor is pulling I would not feel it either.

Except, this is what the marketing says:


They don't say low drag, or not too bad drag, they say ZERO drag. That is just not the case. It doesn't freely freewheel... feels broken or something.

 

[neptronix]

It's kind of hard to assess physical force over the internet but i'd say as for mine..

backwards drag: tons, it's a motor.
forward drag: like a bottom bracket that's >75% of it's useful service life.
Not notchy, the rotation is smooth.

It doesn't seem like enough drag to make a substantial effect on pedaling with the motor off thanks to the reduction ratios in play.

How is the drag in reality while pedaling?

 

[rivers]

I don't think the video is really doing it justice then. There is supposed to be a freewheel in there, but it doesn't feel like there is one. It feels like you are turning over the entire rotor

Yes, there is a freewheel in there. It is on the first stage of gear reduction, but there is a second stage that drives the output pinion. When you turn the pinion you are not turning the entire rotor, just the second gearing stage which looks to be not a high ratio. The bike is easy to pedal with zero battery power.

When you turn the pinion backwards you are turning the motor's rotor thru double gearing so there is high resistance. Nevertheless, it is easy to roll the bike backwards

 

[amberwolf]

You then 3D print a custom disk and move the magnets from the old disk to your custom disk.

Or secure the magnets directly to your chainring, with the sensor mounted so it will read them.

 

[amberwolf]

Regarding the pedalling resistance: Depending on the kind of setup they have inside, it might be a part that is not properly setup initially, or maybe design issue, but has to "wear in". I couldn't find it in a quick search, but I've read posts for at least one of the middrive systems, TSDZ2 or BBSxx, where new ones sometimes require time / usage to wear in before they stop having resistance to pedalling. It isn't something every unit has an issue with, just some of them. Maybe it applies to this one too.

 

[nervagon]

Or secure the magnets directly to your chainring, with the sensor mounted so it will read them.

This won't work. The chainring is able to spin independently from the cranks. We need to know when the cranks are being pedaled, not when the chainring is spinning.

 

[nervagon]

Yes, there is a freewheel in there. It is on the first stage of gear reduction, but there is a second stage that drives the output pinion. You are not turning the entire rotor, just the second stage which looks to be not a high ratio. The bike is easy to pedal with zero battery power.

When you turn the pinion backwards you are turning the motor's rotor thru double gearing so there is high resistance. Nevertheless, it is easy to roll the bike backwards

So it could be related to the noise? The gears need to be worn in?

 

[amberwolf]

This won't work. The chainring is able to spin independently from the cranks. We need to know when the cranks are being pedaled, not when the chainring is spinning.

Sorry, didn't even think of that.

 

[nervagon]

Sorry, didn't even think of that.

This solution is very clean:

Freewheel for Sempu T4 Bottom Bracket - 104mm BCD — Revel Propulsion Ebike Mid Drive Conversion Kits

High quality dual bearing freewheel with 5 bolt mount for Sempu T4 bottom bracket only. Fits 104mm 4-bolt chainrings. Chainline depends on which model of T4 you have and your BB shell width.

www.revelpropulsion.com

The freewheel spider mounts right to the torque sensing bottom bracket.

 

[nervagon]

Notice how that setup above allows you to choose any square-taper cranks you want. They don't need to have a freewheel socket on them!

 

[neptronix]

It's so cool you can just use bike parts.

You still have the too small chainring problem and ~110 RPM cadence. What you gonna do about it?

 

[nervagon]

It's so cool you can just use bike parts.

You still have the too small chainring problem and ~110 RPM cadence. What you gonna do about it?

I really don't know what I'm going to do. Maybe wait until Bikee gets external torque sensors working, and then go dual chainring. There is no reason to expect external torque sensors, as it's not something they've promised. I'm still debating. The noise really does bother me. On my cargo bike, I rarely hear the BBSHD over the sound of my tires. Motor noise seems to be one of those polarizing details... either it really bothers people, or they don't care at all.

I pretty much told Bikee this via email, but due to how loud and conspicuous this motor is, I don't even consider it part of the stealthy, fitness, ultralight category. I think it should be aimed at the performance market to take on the CYC stealth and Pro, BBSHD, etc. I would aim for selling the power of the BBSHD at 1/3rd the weight. As rivers mentioned, you aren't going to be taking this on a group ride with your Lycra-clad cyclist friends. I mean it sounds illegal, just the sound it makes... if that even makes sense. I think people will have trouble believing it is legal. Cyclists already scoff and say that aint no bike, that's a motorcycle, so it doesn't help when the motor is obnoxiously loud... it just feeds into the bias and stereotypes.

I need to take a couple days to decide. Prime biking season is here.

 

[neptronix]

I did some number crunching on what would be the best 3 speed IGH ( we need the extra strength of these! )



1st gear - 18mph 25% reduction
2nd gear - 24mph 100% - direct drive
3rd gear - 32mph 133% increase

From second gear to 1st gear is like dropping from a 26" wheel to a 19.5".

In 1st gear @ an 8% incline with 300lbs weight and this gearing, you should be using ~1000w.
If you drop 1-2mph off this then you should have ~900w load.. the motor should be able to handle that continuously.

There's also this hub which would improve the gearing dilemma but has a smaller shell so it might not be as strong..



Shimano makes a nexus 3 and the 36% gearing steps would work out like:

1st gear - 17.5mph 36% reduction <-- like dropping down to a 18.9" wheel, better
2nd gear - 24mph 100% - direct drive
3rd gear - 32.6mph 136% increase

.. and it's ~150g lighter ..

I think the Shimano is the right one.. you can run a >=14T rear gear and slow down the rate of chain/gear destruction that mid drives dish out. We're solving a typical mid drive problem and a gearing problem at the same time, not bad.