Pedelec Idea - And Hub Motor Sizing For Hills.

[BlackSky]

I want to add a motor to my existing mountain bike to assist (or augment) my peddling. Peddling will always be my main drive source. But my new location has many steep hills, mountains, and it is too much work to just peddle.

First I thought a mid-drive motor with torque-sensor was the way to go, but thanks to feedback from this forum that solution is a bit too expensive and complicated. The recommended alternative is a hub motor with a cadence sensor. But I do not want a throttle, like would be typical on a motorcycle. The reason I don't want a throttle is because I usually ride hard on the handlebars and would be pulling on the throttle and inadvertently increasing or decreasing throttle.

Instead of a throttle is it possible to have a similar mechanism as the thumb derailer control? Meaning a thumb lever that when pushed would click to different levels of motor acceleration. For example when starting out I could push to position "1" that would be low power, and incrementally push to higher position as more power is needed. If I had this kind of mechanism I feel I would not need a cadence sensor, as I would add motor power when I wanted it.

In terms of motor size for a front wheel hub motor, I weigh about 175 lbs, and as I mentioned would be going up pretty steep hills. I don't know how to classify the steepness of the hills in terms of degrees to give you a better understanding, but they are steep enough that it is a real hard workout just to go up them. So, I am looking for a motor that is powerful enough that it would make riding up the hill equal to as if I was riding without any motor on a flat road. Would 500 watts be enough or...?

 

[99t4]

But I do not want a throttle, like would be typical on a motorcycle. The reason I don't want a throttle is because I usually ride hard on the handlebars and would be pulling on the throttle and inadvertently increasing or decreasing throttle.

This confused me. All types of highly competitive motorcycle racers (motocross, GP, etc.) in extreme conditions control their bikes successfully with twist throttle without "inadvertently increasing or decreasing throttle." What makes your situation different?

Anyway, there are other options easily available. Look for half-twist throttle, thumb throttle, finger trigger throttle. You could even fit something similar to what is used for snowmobiles, or jet skis.

 

[E-HP]

as I mentioned would be going up pretty steep hills. I don't know how to classify the steepness of the hills in terms of degrees to give you a better understanding, but they are steep enough that it is a real hard workout just to go up them.

Can you provide a google maps link to a typical steep street as an example?

 

[BlackSky]

But I do not want a throttle, like would be typical on a motorcycle. The reason I don't want a throttle is because I usually ride hard on the handlebars and would be pulling on the throttle and inadvertently increasing or decreasing throttle.

This confused me. All types of highly competitive motorcycle racers (motocross, GP, etc.) in extreme conditions control their bikes successfully with twist throttle without "inadvertently increasing or decreasing throttle." What makes your situation different?

I think my wording was poor. I don't ride a motorcycle, but when riding my bike I'm often pushing and pulling on the hand grip (whatever that is called) as my body moves forward or backward, this is when standing mostly. It just seems like if the hand grip was a throttle I would be moving it up and down the way I ride.

Anyway, there are other options easily available. Look for half-twist throttle, thumb throttle, finger trigger throttle. You could even fit something similar to what is used for snowmobiles, or jet skis.

Thanks, this is what I am looking for but did not know it was an option. A thumb throttle or finger trigger throttle sounds perfect. However, just to be clear with these types of throttles, if you move the throttle with your thumb to increase power and then remove your thumb the power remains the same? This is what I am looking for. I would not want to have to hold my thumb to the throttle to keep the power, and if I remove my thumb the throttle would go back to zero with some sort of spring mechanism.

 

[BlackSky]

as I mentioned would be going up pretty steep hills. I don't know how to classify the steepness of the hills in terms of degrees to give you a better understanding, but they are steep enough that it is a real hard workout just to go up them.

Can you provide a google maps link to a typical steep street as an example?

https://www.google.com/maps/place/Point+Lakeview+Rd,+California,+USA/@38.9339577,-122.6632512,17z/data=!4m5!3m4!1s0x80838ae2fe026b0b:0xa947cce359642c9e!8m2!3d38.9442646!4d-122.6790125

 

[E-HP]

Can you provide a google maps link to a typical steep street as an example?

https://www.google.com/maps/place/Point+Lakeview+Rd,+California,+USA/@38.9339577,-122.6632512,17z/data=!4m5!3m4!1s0x80838ae2fe026b0b:0xa947cce359642c9e!8m2!3d38.9442646!4d-122.6790125

I know that road. I used to ride my motorcycle up to Clear Lake when my friend was living up there.

With 500W, you should be able to ride most of those hills with moderate pedaling, but pedaling harder than on flat ground without power. You'll definitely need to contribute more on the steeper 15% sections. I'd use a 1000W motor. You may need cooling, since that one hills basically looks to be a mile and averaging 10%.



On the thumb throttle, you could always add a thumb throttle and get a controller that has cruise control. Then you have the flexibility of using the thumb throttle, and set the cruise control when you are too lazy to use it.

With 1000W, and you contributing 150W, with Statorade for cooling, you could climb 10% at 15mph indefinitely.
https://ebikes.ca/tools/simulator.html?motor=M2707_SA&batt=B5213_GA&axis=mph&grade=10&hp=150

It will do 15% for the shorter section in the example, but overheat if you go too much past 15 minutes, or you could pedal harder...
https://ebikes.ca/tools/simulator.html?motor=M2707_SA&batt=B5213_GA&axis=mph&grade=15&hp=150

 

[99t4]

However, just to be clear with these types of throttles, if you move the throttle with your thumb to increase power and then remove your thumb the power remains the same?

No, not unless you engage cruise control (if available option), as stated above.

I would not want to have to hold my thumb to the throttle to keep the power, and if I remove my thumb the throttle would go back to zero with some sort of spring mechanism.

Yes that is how they work.

Perhaps in your case, due to your inability to safely use a hand control as a speed/power control, you should look for a torque-sensing system that applies power based on your foot pressure spinning the pedals. If well programmed, it is quite an elegant solution (possibly the most seamless natural-feeling implementation of power augmentation; as if you had bionic legs!), if potentially spendy.

 

[BlackSky]

Thanks, I think I'll go with a 500w and just peddle more up the steeper hills. The map I linked is one of the tougher hills.

I would do the mid motor with torque sensing, but for my first conversion I really can't put that much time and money into it.

In looking at front hub motors there seem to be few options. On Bafang's website I can find a motor that I think would be the right fit but when I search the web for it I cannot come close to finding a seller. There are plenty of Bafang Mid, and some rear.

Is there a reason the front hub is not that popular?

 

[E-HP]

In looking at front hub motors there seem to be few options. On Bafang's website I can find a motor that I think would be the right fit but when I search the web for it I cannot come close to finding a seller.

What donor bike are you using? Front hub isn't a good choice if using a suspension fork. Fine on a rigid fork, and best if it's steel.

 

[BlackSky]

In looking at front hub motors there seem to be few options. On Bafang's website I can find a motor that I think would be the right fit but when I search the web for it I cannot come close to finding a seller.

What donor bike are you using? Front hub isn't a good choice if using a suspension fork. Fine on a rigid fork, and best if it's steel.

I do have front suspension, Trek Marlin MTB Hardtail.

Is the rear hub motor that much more difficult to install? The kits all seem to come with the wheel, but I do not need, or want, the wheel as the one I have is surely better. Where can the motor and individual components separately?

Thanks.

 

[99t4]

Is the rear hub motor that much more difficult to install? The kits all seem to come with the wheel, but I do not need, or want, the wheel as the one I have is surely better. Where can the motor and individual components separately?

Yes you do need to verify the motor OLD will fit between the dropouts, and may need to use a freewheel with fewer cogs (again, fitment issue), and securely fit good quality torque arms.

If you like lacing wheels and are good at it, then just get a bare motor and lace it into the rim of your choice. Some have trouble calculating the correct size spokes to order. Otherwise just get a prebuilt motor/wheel.

One of the more efficient DD hubmotors is Leaf motor. They sell bare motors to order; look them up.