The Ideal for a moderate-powered ebike

[Reid Welch]

Here's my for=sure recipe! (yours may be different, bah! ha ha!)

Presuming it is strong enough:

-The NuVinci hub transmission
-A Currie style drive on the right side, in parallel with the pedal chain.

Why? Full flexibility for both edrive and pedaling.
Shiftless, shockless, full power all the time.

Unitized: I like the currie-type drive because it's so easy to service (I've got a Mongoose entry-level bike).

I like NOT having a $$ hub motor in the wheel, dependent on special spoking.

I do like having a conventional bike wheel, rear wheel e-drive and changeable gearing
(which at present I do not have).

I wonder---down the road, will the NuVinci be mod-able to contain a tandem input sprocket? (this means stacked freewheels).
I wonder if that's even do-able?

-----

Oh baby, that's what I want!



So what do -you- want for your dream drive?
Surely not a fifteen or twenty pound front hub motor?

And if NuVinci turns out strong and good, and could be adapted to our (MY) wants, what is the future for Cyclone-type bottom bracket drive?

 

[fechter]

If the Nuvinci hub is not strong enough, one of the other multi-speed rear hubs would make a next best. The idea of shockless gear change would be attractive with e-drive.

As far as stacked freewheels, anything is possible to a good machinist.
You would need to leave a fair amount of clearance between the sprockets so the chains don't get tangled up in each other.

If you got the gearing right, you would still be able to pedal when the motor was at full speed.

 

[xyster]

Sounds good to me, Reid. However, the NuVinci isn't a shift-free auto CVT. Shifting is continuous instead of by discrete gears, performed by moving a continuous dial on the handlebars.

I'll probably being getting a mongoose/currie ~$400 ebike for the little lady, and for me to ride to work in areas I don't want to park my slightly more expensive ebike.

What are some good motor/controller/other mods (besides batteries) still available for this type 24V bike? I have plenty of ideas for battery upgrades already! As far as the other electrical, I'd like to go at least 36v, hopefully 48v, ~30 or more amps. I understand the uspd kits are no more. If not appropriate here, could you start another thread? I know you had posted lots about this at one of the other old e-haunts.

 

[Reid Welch]

Hi gents. Thanks for helps!

The NuVinci, I termed "shiftless" in the sense that it transitions the gear ratio without any mechanical disconnect or jump.
Therefore, if it's strong enough for, say, a 500W power input (I suspect it will be), you may "shift" under full power, and yes, as fechter noted, pedal and power at all times in sync if the motor is geared similarly to the pedaler's own potentials.

I can imagine it'd drive like this: Full power! Dial the gear ratio to obtain the acceleration you desire; or for the slogging uphill at minimum current consumption v. the speed you desire to pay for from your account at Battery Banking, dink (inc.)

For the cheap curries with their Unite 1018 motors,
the bike will go 24mph by just upping the volts to 36.
The stock controller will still serve, won't blow (mine hasn't, anyway).

The motor -will require- forced air cooling though.

And I am greatly convinced by vast experience (ha ha) of having ruined one motor, and then by keeping its replacement alive ever since,

it's well-worthwhile to cement the motor bearings to their shafts (banish journal slip-fits) And I lightly 'glue' (PerfectGlue, rubbery stuff) the bearigs' OD's to the bores. This stops odd squeals and makes the gear meshings solid, unchanging. My second motor runs relatively silently under load. It's surprisingly quiet. The gear mesh is adjustble to a degree, owing to slop-fit of the case covers. Make book of that by trial running the motor without load, on a few volts, whilst fiddling the covers;
then lock them down. Seal the case joins with a smear of something or other; otherwise water will work in. Make the grease compartment re-greaseable by two 8/32 tapped holes; syringe-in a supply of moly bearing grease (my fave for this), and plug the grease-in-grease-out holes with stubby screws.

I like a 45 dollar motor that, when it fails or gets old, can be swapped in just a few minutes of time. Run within its design center of 15mph/250W, I daresay it's "efficient" as anything else, for practical purposes.

Yet, for pushing hard, it will go inefficient, converting many amps into toaster heat. But that's a price I'll pay to have a five pound motor system capable of driving my cheap bike 24 or more mph. I will make it to thirty some day with this thing. Need more volts, is all. And more force cooling.

 

[safe]

NuVinci Hub - 4.2 kg - 9.2 lbs

8-speed Hub - 1.5 kg - 3.3 lbs

So for the same gearing advantages you are TRIPLING the weight.

This needs to come down a little before it makes any sense. However, for the higher powered motors that might possibly damage the gears of an 8-speed this might be the perfect solution... assuming it can HANDLE more stress which I couldn't find any published data about.

A standard hub can handle at least 100 Newton Meters (about 1500 Watts continuous) without any problems.

 

[fechter]

I think a BMC 600w motor fits some of the Currie drives. A PowerPack version with external control would make a nice powerplant.

 

[xyster]

I think a BMC 600w motor fits some of the Currie drives. A PowerPack version with external control would make a nice powerplant.

That's what I was wondering. Can anyone confirm that this BMC brushless motor
http://www.powerpackmotors.com/POWERPACKMOTORinfoandphotopage.html
would fit the currie/mongoose 24V bikes?

 

[Mathurin]

I should point out that from the reviews I've read of the Nuvinci so far, it seems you have to ease off the pedals to shift it. In practise this would mean you'd still have to change gearing ratios a chunk at a time.

 

[Geebee]

The 8 speed shimano can be shift under load or unloaded and is lot, lot, lot cheaper and proven technology.
Build a delta trike pedal one rear wheel and fit a geared hub and motor to the other side and it would be great off road as you have 2wd.
Or as above but drive the front wheel on a normal bike.

 

[fechter]

I think a BMC 600w motor fits some of the Currie drives. A PowerPack version with external control would make a nice powerplant.

That's what I was wondering. Can anyone confirm that this BMC brushless motor
http://www.powerpackmotors.com/POWERPACKMOTORinfoandphotopage.html
would fit the currie/mongoose 24V bikes?

That's the motor I was thinking of. Basically the same as the one on my Vego. It works with a Crystallyte controller. I think it comes with a small freewheeling #25 chain sprocket on the motor shaft. As I recall, it's a 12mm smooth shaft with circlip grooves. It is not made for the planetary gear reduction. I have a couple of the sprockets, but I'd have to go count the teeth to tell you how many they have.

 

[TylerDurden]

I think this is the drop-in upgrade:

750W GEARED Motor - 36 Volts (Model: MY1020Z3)

MY1020Z3 36 Volt, 750 Watt, 2800 RPM, 27.4 Amp, permanent-magnet motor.

10 tooth sprocket for 420 chain.
12 gauge power leads.
Gear Ratio: 60:9 (6.67)



At least, that's what I will be using.... much wider, but I think it will clear the cranks on my currie motoX.

For the rear-mounted curries it should not be an issue , other than cosmetic. Sprocket might need swapping with the original.

 

[xyster]

At least, that's what I will be using....

Any overvolt plans, TD?

 

[Reid Welch]

I should point out that from the reviews I've read of the Nuvinci so far, it seems you have to ease off the pedals to shift it. In practise this would mean you'd still have to change gearing ratios a chunk at a time.

That wouldn't do for us at all.

Looking around now, translated by the German author,

..If you have load on the Hub the resistance on the shifter will become a little more. Not dramatically, but enough so that I think you will get used to taking a little load of the Pedals when shifting to have this ultra-smooth shifting experience. The Hub still shifts well under full load. There is no noise, a truly seamless shifting process! It still amazes me!
http://phil.veloblog.ch/post/7/333

 

[TylerDurden]

Any overvolt plans, TD?

Absolutely.

I'll bump it up to 48V to use the 24V Ridgid lithium battery packs.

 

[NickF23]

NuVinci Hub - 4.2 kg - 9.2 lbs

A standard hub can handle at least 100 Newton Meters (about 1500 Watts continuous) without any problems.

My understanding of the nexus sturmey archer type hubs is that whilst lower maintenance than a chainset they do wear. E assist will speed up that process, as will towing heavy loads. I think nexus brought out a 5 speed 'Cargo' hub specifically for higher loads. Might be a good model for ebikes. Do you know of any other high load hubs?

 

[Geebee]

The Rohloff Speedhub 14 speed internal hub, reported as the best internal geared hub in the world bar none, people joke of leaving them to the kids in their wills.
You void the warranty if you gear them to high levels of torque but supposedly they have never had a speed hub fail.
Oh I forgot to mention they are expensive probally in the region of a grand plus in Us dollars.

 

[Lowell]

I like the idea of a heavily built hub, but the fact remains that they were only designed for pedal power. Breaking a $1000+ hub would be an expensive experiment.

 

[safe]

I like the idea of a heavily built hub, but the fact remains that they were only designed for pedal power. Breaking a $1000+ hub would be an expensive experiment.

Just do the math. If you know what is "safe" then the hub will never break on you. Every time you lower the gear ratio you get a corresponding increase in torque. The Rohloff hub allows 100 Newton Meters at the hub and you will find that it's not that hard to keep things within that. Even with a 2000 Watt motor if the gearing is high enough you will never exceed the spec.

Know your math... save $1000... :wink:

Also, as rpm's rise the torque drops a great deal, so you can protect yourself if you make your "power peak" and "efficiency peak" be the same... translation... run a low current limit controller. Since you have plenty of gears (torque options) you can afford to run "perfectly" all the time... this also reduces heating...

 

[xyster]

The Rohloff hub allows 100 Newton Meters at the hub and you will find that it's not that hard to keep things within that. Even with a 2000 Watt motor if the gearing is high enough you will never exceed the spec.

According to the hubmotor simulator, the 5304 generates a peak torque of 115 Newton-Meters at my system's peak of 2800 watts; a 408 would generate peak torque of 85 newton-meters at the same wattage.
So IMHO, 100 newton meters at the wheel makes for excellent real world e-bike performance.
It's great for us these hub transmissions seem to be significantly overbuilt for human power input. Hopefully, years of real-world e-abuse will substantiate the manufacturers' claims and numbers.

 

[safe]

According to the hubmotor simulator, the 5304 generates a peak torque of 115 Newton-Meters at my system's peak of 2800 watts; a 408 would generate peak torque of 85 newton-meters at the same wattage. So IMHO, 100 newton meters at the wheel makes for excellent real world e-bike performance.

So a 1683 Watt peak motor that is geared "conservatively" so that it's top speed in eight gear is 50+ mph and the first gear won't blow up the hub would look like this chart. (it's my 1200 Watt project) I doubt that at the very lowest rpm's that the full torque actually happens. (due to losses) Most of the time I would be using about half the available torque.

 

[safe]

But this is where is gets weird. On my current SLA bike this chart displays the difference in torque that the rear freewheel cluster must endure depending on the use of the high gear (22 tooth) or the low gear. (14 tooth) The irony is that when I got the new controller that seems to have the "full 40 amps" that the previous one did not really have (more like 30 Amps it seemed) I can now run the taller gears if I want. The result is counter intuitive because even though I'm getting MORE power out of the motor because I've switched to the taller gear I actually am applying LESS torque to the rear freewheel.

Strange huh?

 

[Reid Welch]

The Rohloff hub allows 100 Newton Meters at the hub and you will find that it's not that hard to keep things within that. Even with a 2000 Watt motor if the gearing is high enough you will never exceed the spec.

Mr. Annoying Prediction here (lol)

regrets to inform that the conventionally geared hub is out of the application question.

It just won't work except as a near-term mechanical disaster.
It -could- work, but would require a custom designed (fill in blank here)
and this would be a kludge at best.




I'm going to tease you guys to THINK out why this is true.
Don't make me have to tell....or I might just come across on a high horse :lol:




too late! giddoff ur high horse reid!!!


Seriously, the basic answer is below, in whiteout
(click quote for spoiler):



Several members here already knew the difference between pedal power
and the kinetic juggernaught that is a motor rotor.

 

[xyster]

Several members here already knew the difference between pedal power and the kinetic juggernaught that is a motor rotor.

Answer not com-pooting. Explain, please.

 

[Reid Welch]

not to be coy, but you have the basic answer above in your quote.

see? I can put it in plainer words easily,

but not quite yet, ok?

think

 

[xyster]

A kinetically excited, circularly motivated, motor rotor possesses more momentum than a similar amount of sticky-piston-ish, leg-pedal power.

What does this have to do with peak torque specs for hub transmissions, I wonder?