Why do you use a brushed motor ?
For begining, there are two major types of engines :
-A- brushed motor (used in LIFT MTB)
An electric motor with
brushes, it's simple and reliable conventional engine, in fact the most electric motor produced in the industry .
-B- The brushless motor.
An electric motor without brushes with a complex electronic controller, which allows to replace the brushes and to increase some characteristics.
But why The brushed technology is sometime criticed ?
Sometime it
is considered that the brushed is wrong has brushless because it is associated with some other technical choices that do not highlight these strengths, which not make this technology not
necessarily optimal for some specific cases (including hubs motors).
But that would be like saying: "Ferrari is a very bad car ..." forgetting to add: "For off road."
It is this technology combinations
aspect not necessarily consistent optimally, which is mostly misunderstood by consumers.
They therefore consider that ignorance is not a performance
or old technology.
Users typically read on a forum: "The brushless is
better!" they persuade themselves in without seeking further ...
That is why this is not true for the LIFT MTB engine:
For most purists of the brushless electric
motor provides with very good characteristics for the following reasons:
-Argument 1-
It allows a range of rpm, minimum / maximum larger than a brushed
motor.
For this technology accepts
tensions that increase the maximum amplitude without problems.
-Argument 2-
There is no resistance, in particular freewheel.
-Argument 3 -
It need less service on the brushless because there is no brush.
-Argument 4-
There is a good torque and good performance
especially at high speeds.
But keep in mind that all these benefits are very useful for some tipical applications and only some specific cases such as electrichubs for ebikes or RC fast
car engine.
For
exemple, with a hub motor, the wheel rotates continuously and sometimes has a large high speeds, which induces stresses totally different than a bolt on motor as the LIFT MTB:
-For Argument 1-
No need to have a large range of RPM with the LIFT MTB kit, contrary
to a hub motor which has a fixed transmission ratio, it can be on a crank drive motor as the LIFT MTB play with the different speeds with the rear derailleur.
We
must therefore remain in use speed range close to the average velocity of a cyclist , if the reduction ratio is good the performance of the brushed motor will be the
best.
No need to go at much higher tension, that would increase the speed of rotation of the crank and the ridere can't rotate the legs fast enough to help the engine ...
-For Argument 2-
Concerning
the "natural" freewheel with a brushless motor, this resistance is bad on a hub motor, because that's brake you every time if you stop to using assistance (flat, downhill, slight
side without assistance ...).
But on the LIFT-MTB system, we have a mechanical freewheel Added Inside the motor, so with this tech solution that don't brake the crank when you stoping to use the assistance, the crank
will be free same as classic bike !
-For Argument
3-
For the
brushed wear this is again valid for a wheel which rotates very rapidly and permanently, but for a motor crank, as we have designed it is negligible because:
-A- When the LIFT MTB motor rotâtes, it is not very fast (generaly 5
times slower than hub.)
-B- For
all parts or you do not pedal (flat, downhill ...) the engine will not work at all, compared to a Wheel continuously
turn.
-C- As you pedal, the freewheel help take the relay and
motor Don't turn, so the engine is not therefore cause no wear on brush.
-D- So there is only small phases when you use the engine as
the brushed come in contact …
So that representing a theoretical wear rate very much lower as you imagine !
-For Argument 4-
Regarding
consumption and the torque at high speeds, this is again interesting for the hub motor use, but not mid drive crank engine .
Yes brushless performs better on paper than a brushed, so it would lower consomation.
But that's
not incluing the losses for the reduction ratio!
As we have
high-speed torque with brushless has this requires a larger reduction rate to, don't rotate the crank too faster than the rider can move the legs.
Reduce
speed, generally require increasing the number of gearing and parts, that creates more losses due to friction at the working gear ect ...
More gears is also more weight and more volume for
the system.
So what is gained on
one side by the use of a brushless motor that consumes less one party subsequently falls with the various ratio réductions.
If we add that the brushless is more complex and sensitive technology in management controllers and that it costs much more expensive to buy ,This would increase lot the final price of the kit for nothink, because brushed do the same job with less part's.
Generaly for RC cars, brushed is Always used on trial electric car ,because this technologie offer more torque at low speed, so that is more efficient for up a steep up hill, and we search exactly the same result for e-bike, so that is natural to use the same solution for have the same result !
Conclusion:
We
could develop an adaptable kit with brushless technology involving the use of a motor / controller more expensive, and a multitude of customized parts and more as gears, shafts, housings,
bearings and specific parts needed to have a report effectively reducing (as in the photo below cons).
But if it were to
win at best 10% of autonomy being heavier and probably by increasing the price at 2500 or 3000euro, not sure it would have been more happy customers...
In short, so we
made the choice of brushed because this technology allowed the best ratio
between the different parameters to be taken into account in the design of our
product.