Stronger hub for 2k mid-drive fatty?

mammonista

10 W
Joined
May 27, 2018
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Hey everybody,
My Cyclone powered fatty finally destroyed the Shimano Nexxus 3-speed IGH hub. I ride the bike exclusively on the dunes and sand fields connecting the dunes here in coastal Oregon and never (well almost never?) shift under power. The Cyclone is rated at 3k but with 52 volts I'm only drawing 2k maximum and usually only about 1.5k if I turn the power down to 75% at the controller. I have a spare Shimano Nexxus hub that I'm going to replace the busted unit with but I'm curious if I'd have better luck with a Sturmey Archer RX-RK5? That unit certainly looks a lot beefier, but I'm wondering whether anyone has had any real world experience with one on a fatty?
I don't have the big buck for a Rohloff and if nothing else works I'll probably just go back to the single speed the bike came equipped with but I've grown to love the advantages of a 3-speed on the dunes.
Anyone?
Thanks,
Mark
 
NEXUS Inter-5E is apparently much stronger

but still half the torque tolerance of a Rohloff

Check out Kindernay XIV from Norway
 
For a cost-effective option, I’d try the Sturmey Archer RS-RK5.

85.jpg
 
Very interesting that you destroyed a IGH using a mid drive system with 1500W or power.
Obviously the IGH's are not meant for superman type leg power, 10x.

Spinning Magnets did a good article on IGH and mid drives.
https://www.electricbike.com/mid-drive-kit-igh/
In a 3-speed, the second and third gear are selected at the planetary shell or the planetary gear-pins (not near the axle with lifting dogs or sliding dogs, where a higher amount of leverage could be applied, and cause breakage), and it’s done by the 4-arm axial clutch (no pawls), so it’s very strong. I’m stating these design features so readers will understand why I claim the 3-speeds are much stronger in all the gears, compared to a 5 or 7-speed.
 
markz said:
Very interesting that you destroyed a IGH using a mid drive system with 1500W or power.

It’s not power, but input torque that will mangle internal gear hubs. Most of them have specifications for both maximum rider weight and minimum primary gear ratio, and some have ratings for maximum input torque. Violate these, and all bets are off.
 
For example the Rohloff is designed to shear a "torque fuse" pin at 130 N.m

which I understand can be exceeded by motors over 4000W?

Not sure about the cheaper Norwegian clone I mentioned above
 
john61ct said:
For example the Rohloff is designed to shear a "torque fuse" pin at 130 N.m

which I understand can be exceeded by motors over 4000W?

Not sure about the cheaper Norwegian clone I mentioned above

can be exceeded by motors <1000W, particularly with larger gearing ratios. That and landing a jump under power and the torque could be far, far higher than 130Nm.
 
Well I might run the 500lb longtail over a big stick, but don't think that counts as a jump.

So I take it the "slow start" rampup curve ends up being critical, maybe a CAv3, or a well configurable FOC controller. . .
 
Luna put the 5 Speed Sturmey Archer in the BABE. They indicate the stock m600 puts out 800 watts and 120nm of torque. They will not offer ludicrous controller (double current) on the BABE due to concerns the hub cannot handle more than stock.

https://lunacycle.com/babe/

Also, see comments here by Watt Wagons regarding Rohloff, torque and throttle. I believe the torque limit for throttle is stipulated by Rohloff.

https://electricbikereview.com/forums/threads/whoa-is-this-real-an-actual-3000w-controller-for-the-bafang-ultra.32536/#post-256048
 
sn0wchyld said:
(130 N.m)
can be exceeded by motors <1000W, particularly with larger gearing ratios
So is limiting amps the best way to limit torque?

Say on a true FOC controller, or are there other better parameter settings?

Or "ramp curve" tweaking I've come across, maybe CAv3 ?
 
john61ct said:
sn0wchyld said:
(130 N.m)
can be exceeded by motors <1000W, particularly with larger gearing ratios
So is limiting amps the best way to limit torque?

Say on a true FOC controller, or are there ogher better parameter settings?

Or "ramp curve" tweaking I've come across, maybe CAv3 ?

only way to control the torque directly is phase amps - battery amps have at best a tangential control on motor torque, and in reality next to no control...

only way to be sure that your torque is <130 is to calculate:

Ratio to the hub (ie sprocket ratio)
ratio of any additional reduction stages
kv of the motor

a.take the kv of the motor and divide 9.5 by that kv (there's a more accurate # for this but this is close enough) ie 9.5/kv=...
b.this is your 'torque per amp' at the motor shaft.
c.multiply this value by all the reduction/transmission ratios between the motor shaft and your hub, ie 'torque per amp' x 'reduction ratio' = ...
d.multiply 130 by the value calculated in step c, and that will give you your max phase amps that you'll need to program into the controller, ie 130 x 'answer to c' = 'max phase amps'

for a sanity check the value you get should be in the region of 50-200A or so (educated guess)... so if you've got values of 2A or 3000A something is wrong in the maths. The most likely cause is that the reduction ratio is 'backwards' - not wrong, just the inverse of the one needed for the above calculation (ie a 10:1 ratio could be either '10' or '0.1'... it should be the '>1' version for the above to work).

In reality you could put in a little higher value, as there'll be some losses etc that will rob some torque, but the above calc will get you close.

from that you can calculate the max phase amps your controller should feed your motor in order to stay below the 130 mark... that said you'll still have the 'shock value' of torque that can be far greater should you land a jump under power.

sorry im also doing a shitty job of explaining it, gotta get some sleep, my coffee has worn off :p
 
john61ct said:
If the torque needs to be limited for throttle control, why doesn't it for PAS?

I am guessing PAS blends in the delivery so less likely to damage the hub from abrupt changes. A few comments by pushkar on EBR:

https://electricbikereview.com/forums/threads/just-ordered-the-first-ever-fat-tire-watt-wagon.30645/page-3#post-246600

https://electricbikereview.com/forums/threads/do-you-own-a-watt-wagon-useful-information.32309/#post-252546

https://electricbikereview.com/forums/threads/whoa-is-this-real-an-actual-3000w-controller-for-the-bafang-ultra.32536/#post-256048
 
sn0wchyld said:
sorry im also doing a shitty job of explaining it, gotta get some sleep, my coffee has worn off :p
No, thanks, that's a great start!

And shows a CAv3 is not an option only having access to heat and pack amps. . .

Another (maybe?) way to go with a Rohloff providing their shear pins as "torque fuses", might be first get some spares, and

given a certain rig fully loaded and some typical big hills, keep tweaking the phase amps upwards at low rpm until you shear one

then back it off say 5% at a time until you stop breaking them.

?

 
Tom said:
I am guessing PAS blends in the delivery so less likely to damage the hub from abrupt changes. A few comments by pushkar on EBR
So maybe a CAv3 could be useful for the "throttle mapping" feature,

on a controller whose control features don't include any ramp up control.

I bet a good FOC implementation would also help, everyone goes on about how smooth their takeoffs are.

I never heard of going up to 200+ N.m with the Rohloff, that's pretty exciting!

Thinking the #215 chain used on Lightning Rods' big blocks & XL might work well driving that.

Overkill for most, but heavy cargo, big hills. . .

That note about not doing throttle from dead stop worries me though, just can't stop halfway up a big mountainside slope?
 
The dead stop comment was for the stock bafang ultra controller. To get Rohloff certification they could only offer a 750W version of the Ultra if you wanted throttle. They are in the process of upgrading to the newer aftermarket controller which allows them to limit throttle to 90nm while not capping motor output for PAS which allows you to gun the throttle from full stop if you want: "with this new controller, the recommended way to use the throttle is to just gun it."
 
The SA RX-RK5 5-speed hub arrived day before yesterday. Looks like it was developed by the folks at Mack Trucks! Stout and heavy?

I'm gonna have it laced into my rim and turn the power down to 75% on the controller (1500 watts) and hope the Cyclone doesn't destroy it. I promise never, ever, 'cross my heart and hope to die' to shift under power and I never jump my fatty and come down under power.

The kind of riding we do is strictly low speed stuff on the dunes and sand fields connecting the dunes here in coastal Oregon.

I shot this video yesterday on my back-up fatty. Brett edited it all together. Front and rear facing Sony Action cams on my helmet.

https://www.youtube.com/watch?v=WKf0pXNZqk4

[youtube]WKf0pXNZqk4[/youtube]
 
cool dunes I gotta check that out.
How long did the shimano nexus last? and
how do you like the sturmey Archer?

thanks and have fun



mammonista said:
The SA RX-RK5 5-speed hub arrived day before yesterday. Looks like it was developed by the folks at Mack Trucks! Stout and heavy? I'm gonna have it laced into my rim and turn the power down to 75% on the controller (1500 watts) and hope the Cyclone doesn't destroy it. I promise never, ever, 'cross my heart and hope to die' to shift under power and I never jump my fatty and come down under power. The kind of riding we do is strictly low speed stuff on the dunes and sand fields connecting the dunes here in coastal Oregon.
I shot this video yesterday on my back-up fatty. Brett edited it all together. Front and rear facing Sony Action cams on my helmet.
[youtube]https://www.youtube.com/watch?v=WKf0pXNZqk4[/youtube]
 
Forgive my ignorance, but I am about to buy a used NuVinci N171 cvt hub but I have some concerns about the lack of parts like the disc brake adapter kit, and a belt cog among other things like the potential to break the hub seal under hard braking....

My question on the 5 speed geared hub options is are the subject to the same failure from exceeding torque limits briefly if the power is applied to from the disc brake side? I don't know enough about the internals and the pawls.

Edit:

Or rather if motor power applied to the disc side and human power from the cracks applied to the sprocket side.
 
TorontoBuilder said:
Or rather if motor power applied to the disc side and human power from the cracks applied to the sprocket side.

Yes this seems like a great way to save bike drivetrains.
 
Mammonista,

Save your money & time trying to employ those various gear hubs except if you build a dual drive and use the gear hub on the pedal chain side(or use a derailleur). I have a CVT as such. You become the torque sensor and not some digital devise demanding such and such input. If you want more exercise use less throttle.

Now that you are broke down you have little existing equipment costs to mitigate. The money you spend for a HD gear hub could get you a Cyclone 6K. Run the setup as a single speed, gearing it for a max speed of say 25 mph. The Cy3K geared as a one speed does not quite do the work and have much speed when geared for sand dune milling.
 
The middle gear on the Common IGH's use stout pawl's near the outer edge of the shell to transmit power from the input sprocket directly to the hub-shell for a very stout 1:1 transmission of power.

Each gearset that is added provides an over/under gear. The 3-speed is very tough with the 2nd-gear being direct-drive. 1 and 3 are equally strong as each other, but...still more fragile than 2nd gear.

The 5-speed is also very tough, which results in it being physically larger and a bit heavy. It was developed and then strengthened for cargo-bikes. On the 5-speed, the 3rd gear is direct-drive.

The farther you get away from 1:1, the more fragile one of the gears becomes, so on a 5-speed, 3 is strongest, 2 and 4 are stronger than 1 and 5.

The 7-speed IGH's available are made to be light and compact. They would work fine on a BBS02 on relatively flat terrain. There doesn't seem to be much demand for a fatter, heavier, and stronger cargo-7 (maybe someone is working on this?)

The Rohloff-14 was made for European mountains, and customers demand more gears with close ratios so they could find the exact perfect gear for the slope, and also to allow most bicycle frames to eliminate any front derailleur for "de-cluttering".

The 3-speeds and 5-speeds use the widest ratios that can fit inside the shell. I say this so you'll understand that if you get a Rohloff, you may be shifting frequently. I have met several people who report that they shift two gears at a time.

On the inside of the Rohloff, there is a close-ratio 7-speed. Just inside the input driver is a wide-ratio 2-speed, to provide a high and low range. They are designed to provide 14 equally-spaced gears.

The shear-pin is brilliant. These are well-known in engineering circles. If you try to "pop a wheelie" with too much power....the pin snaps instead of the gears.

The more power you have, the fewer gears you need. It would be nice to see a Rohloff 7-speed with wider ratios and still using the shear-pin. However, even removing the cost of the stacked 2-speed, I can't imagine it selling for less than $800.

Even without the shear-pin...the gears inside the Rohloff are the absolute strongest available.
 
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