Swapping 1500w DD for a geared hub?

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AHicks   1 kW

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Swapping 1500w DD for a geared hub?

Post by AHicks » Feb 28 2019 4:04pm

I have a bike currently set up with a 1500w DD, using a 35a KT controller and LCD3 display (very similar to that sold by Leafbike). Battery is able to supply 25a with shorter bursts slightly higher.

Having no use for speeds in excess of 20mph, and a desire for a little better performance in hilly terrain (bike used in a rolling coastal area), currently kicking around the idea of converting the bike to a geared rear hub. Thinking I may be able to get away with using less power at 10mph on the level, and have more "grunt" available when needed for the hills? Perhaps a 1000w Mac 10 or 12t, but I'm open for suggestions. I know very little about the available 750+ watt geared hub options. I'm 315 lbs and playing in a hilly area, so I'd much rather have too much power than not enough.....

Also wondering if I'll be able to use my existing 35a controller and display, or if I'll be forced to update? Pretty sure the controller is able to be configured with an external wheel speed sensor, and I'm assuming my current PAS sensor and throttle will be able to be used as is.

A question for those with DD and geared hub experience. How much difference in the noise levels between the 2? Squeaks and rattles drive me batty, will the noise from the gears make me crazy?

Thanks for any help/guidance/links that might give me a hand making this call -Al

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Re: Swapping 1500w DD for a geared hub?

Post by itsallwhite » Feb 28 2019 5:22pm

I'm in a similar situation with regard to wanting grunt to help get me up hills rather than top end speed on the flats. Interested to see comments on this one.

I've looked for a high powered geared rear hub, but most of the ones i've seen are rated at (nominal) 500w (e.g. Bafang BPM and MAC).

Another option mentioned in the thread I started was a slow wind DD motor, possibly in a smaller 24" or 20" wheel...
Bike 1: Giant Hybrid Steel Frame (old) with TSDZ2 48v 500w.
Bike 2: GT Sensor 2 full suspension mountain bike. Work in Progress - ready to 'electrify'!
House: 100% off grid - 5.6kw solar array with selectronics inverter and 24 Volt 1450 Ah BAE Gel battery Bank

markz   100 GW

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Re: Swapping 1500w DD for a geared hub?

Post by markz » Feb 28 2019 6:06pm

https://em3ev.com/shop/upgrade-mac-ebik ... 2000w-max/
Geared MAC motor rated for 2000W Max!
Gets you better grunt for the hills.

You could go to a smaller wheel diameter but you'd need a faster wind motor, or a higher voltage to compensate for the reduced speed. I've been contemplating a smaller wheel diameter myself, but I have really seen nothing on the graphs to help go that direction. https://www.ebikes.ca/tools/simulator.h ... grade_b=12

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Re: Swapping 1500w DD for a geared hub?

Post by dogman dan » Mar 01 2019 7:46am

The big dd motor will not be less efficient than a geared motor when cruising on the flat, going slow. Nor will it be more efficient climbing a hill. Basic physics, the hill climb takes a certain minimum energy. In this case, the big motor can climb efficiently, because it has the power to keep its rpm up.

Where you gain efficiency with geared motors, is when you start and stop a lot. Each start with the geared will take less power, because it gets up to rpm faster.

IMO, nothing climbs a hill better than a big motor, with 2000w or more of power applied to it. I do not recommend putting more than 1000w into geared motors though. Not sure what paul did to the 2000w mac, but I'd likely fry one if I used it in the desert where I live. But if you do not live in desert, :twisted: 8)

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Re: Swapping 1500w DD for a geared hub?

Post by AHicks » Mar 01 2019 9:27am

Dan, thanks for sharing. If I may ask, would your opinions change if you did not have 2000w available? What if your system were all tapped out at 1200w or so? What setup would you prefer for the riding you do with that restriction?

That's more along the lines of where I'm coming from. I don't have unlimited battery and controller power available, and plans to upgrade that part of the bike are much more expensive than the simple motor upgrade I'm considering.

I see the big starting advantage the gear drive has on the simulators. I find myself riding in the area of 10-13 or maybe 14mph most often, and recognize there's not a lot of difference between the 1000w plus hubs there. Where I'm interested in improving performance is where the bike enters a climb and starts to slow (to maybe 8-10mph). Which will have the more reserve grunt available to get this fat butt to the top of the hill without using more than 1200w or so....

Currently considering the 12 turn Mac 1500w. Would go to the 2000, but I don't see that it's available in the 12t. Still learning, looking for practical suggestions and further discussion.

Still looking for hints regarding the use of a KT systems controller and display with one of these Mac motors? Anyone tried that yet?

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Re: Swapping 1500w DD for a geared hub?

Post by amberwolf » Mar 02 2019 12:22am

AHicks wrote:
Mar 01 2019 9:27am
Dan, thanks for sharing. If I may ask, would your opinions change if you did not have 2000w available? What if your system were all tapped out at 1200w or so? What setup would you prefer for the riding you do with that restriction?
Your best bet is to try out variations of the hubmotor system you want over at http://ebikes.ca/simulator (middrives can be simulated but you have to work out what they'd be like as a hubmotor)

Setup your battery (or something similar to it) and your controller (or it's equivalent), and the situation(s) you need it to handle, with your wheelsize, weight, and type of bike. Then try different motors under those situations, and see what works, what overheats, and what doesn't, etc.

Use the results as a guide to narrow down your options; might also show you things you didn't expect. :)


Regarding geared vs DD noise...depends on the controller. Sine controllers can make DD hubs virtually silent under most conditions, and reduce geared hub noise some--but the geared hub will still have a "whirr" that a DD does not. It may be very quiet, but it's still there.

Trapezoidal (trap) controllers make a lot more noise on a DD hub at startup than a geared hub, and for longer. But after startup, the DD hub can be quieter, as long as it's not under high load--the higher the load the more noise it usually makes in this type of controller, but it depends on the actual motor and controller in each case.

*Sensorless* controllers can make geared hubs really noisy and "bang" them back and forth at each motor startup, even if the bike is already moving. Some (like the Fusin kit I have, controller by LiShui) are really bad about this. On a DD hub it only makes the grindy noises if you don't get the bike moving manually a bit first--if it's already moving it doesn't do it.

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Re: Swapping 1500w DD for a geared hub?

Post by markz » Mar 02 2019 9:28pm

The working out of the motor simulator for a mid drive is just the gear reduction, placed on the wheel diameter.

viewtopic.php?f=28&t=90812&p=1323651&hi ... e#p1323651
To simulate this (26" nominal wheel with 3:1 reduction) set the simulator to a 9" effective wheel size running the motor

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Re: Swapping 1500w DD for a geared hub?

Post by AHicks » Mar 02 2019 9:35pm

What would you suggest using as a comparable hub motor (leaf 1500w DD)?

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Re: Swapping 1500w DD for a geared hub?

Post by amberwolf » Mar 03 2019 2:43am

I am nto cerrtain but prbably the leaf 35mm 5t.

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Re: Swapping 1500w DD for a geared hub?

Post by AHicks » Mar 03 2019 8:46am

Amberwolf,
Feeling like a dummy. I did look, and skipped right over it. Thanks!

Simulator clearly shows the advantages available with the 1500w Mac 12t gear driven hub over the 35mm Leaf DD hub (within my most commonly used range of speeds). Thinking there's easily enough difference to justify going for it.

Now to see what's going to be involved regarding the swap. Will it be a simple hub and wheel swap, adapting the phase wiring plugs as required, then reconfiguring the controller slightly, or will there be more to it, like adding a speed sensor? -Al

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Re: Swapping 1500w DD for a geared hub?

Post by docw009 » Mar 03 2019 1:13pm

Speed sensor is $10 for an external unit, or the motor may already have it inside the hub. I've used PAS sensors mounted on frame for an external wheel sensor.

Many KT controllers used with the LCD3 have a speed sensor connector. Usually a white white on a three pin JST. Move that wire to the six pin Hall if sensor is inside the motor, If it is a 9 pin connector, KT already has the wire in the cable. Nice of them.

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Re: Swapping 1500w DD for a geared hub?

Post by AHicks » Mar 03 2019 1:36pm

I'm pretty sure this controller is set up for an external speed sensor. I remember seeing reference to it while doing the original set up (I think).

Pas sensor can tell the controller you're moving, but not how fast. I read somewhere where they mentioned that the speedo would stop indicating whenever you were coasting/not peddling due to the geared hub clutch releasing. Want to avoid that potential. -Al

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Re: Swapping 1500w DD for a geared hub?

Post by docw009 » Mar 03 2019 4:45pm

You misunderstood. Not wanting to buy wait, I' hooked a spare PAS sensor to the speed sensor input. Just needed a signal that flashes when the spoke magnet passes by.

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