So, I am buying my wife an eBike to take our 2y toddler on a child-rearseat to school.
We are looking at an either CANNONDALE ADVENTURE NEO 1 EQ or an CANNONDALE ADVENTURE NEO 3.1 EQ
One concern is if we have enough Nm to take them safely up the climbs to our home, which is some places are 15-18%, but only for like 200-300m.
Wifey is fit and can easily climb those hills on her roadbike. The question is, whether either of these bikes produce enough extra power to help her up.
The NEO 1 is aiding with a max of 65 Nm and the NEO 3.1 only with 50 Nm. I only understand watts how does that translate?
She is 50 kg, the bike is 14 kg and our boy and childseat is 20 kg.
Can anybody help if the 3.1 with 50 Nm is enough? Our LBS says “easy” but is not willing to let us test the hills … bummer
Price difference is around 1000 EUR.
This should be fun for the physics folks. The starter kit is that a Nm is a measure of torque. And a Watt is a Nm per second. So, the spec is missing the rate at which the Nm is being applied.
But, here’s a simple example for context. If your wife is climbing a hill at 170 W at 80 RPM, she is delivering around 20 Nm torque to the pedals. So, if the motor can add another 50 Nm, that is a lot relative to her torque.
I like to think back to the basics of my engineering study regarding that topic. I’ve written it down on a sheet of paper (see pic below), just insert correcter values if you know them (like weight of bike+your wife or weight of trailor+kid). There is another basic equation which gives you torque from power. The equation is power=torque23,14*n.
n are the rev’s of the engine in 1/s. The Bosch engine is located at the crank, so this value is the crank rpm (typically between 60 and 90rpm or better 1 per s up to 1,5 per s). You will see, that the required torque is more than 60Nm, but remember that the engine supports and your wife also put torque/power into the system. Typically the electric cycling engines can support up to 250W, the rest comes form your or your wifes legs. At the end you need to divide the power through the efficiency (maybe values round about 0,9?) to get the power which you have to put into the system. But type in your values and you will see were you are.
So, I am buying my wife an eBike to take our 2y toddler on a child-rearseat to school.
We are looking at an either CANNONDALE ADVENTURE NEO 1 EQ or an CANNONDALE ADVENTURE NEO 3.1 EQ
One concern is if we have enough Nm to take them safely up the climbs to our home, which is some places are 15-18%, but only for like 200-300m.
Wifey is fit and can easily climb those hills on her roadbike. The question is, whether either of these bikes produce enough extra power to help her up.
The NEO 1 is aiding with a max of 65 Nm and the NEO 3.1 only with 50 Nm. I only understand watts how does that translate?
She is 50 kg, the bike is 14 kg and our boy and childseat is 20 kg.
Can anybody help if the 3.1 with 50 Nm is enough? Our LBS says “easy” but is not willing to let us test the hills … bummer
Price difference is around 1000 EUR.
Any help much appreciated! T
Try putting the Numbers into bikecalculator to get an estimate
I’s go for the 65nm motor. In order to go up 19% at 6mph she’d have to out put 80watts herself with the 65nm and 130watts with the 50nm.
It’s not so much the NM, as it’s the 50w extra power output. Had to go to the technical specs on the Bosch website to find the numbers
Thanks! I am actually an Mech Engineer myself - embarrassing I had to be schooled THAT much But never touched on these things in practice for 30 years!
Your needs should be determined by the maximum demand, not the average demand, so calculate the demand for the steepest section and low cadence, not average slope and average cadence.
During a pedal stroke, max torque is roughly twice avg torque.
Your wife is “fit” and gets up the hill easily on her road bike but should picking up your kid be a workout?
Go for the 65 Nm motor, so you can occasionally pick up your kid, too.
Thanks Brasch. Good point, but its literally a price jump of more than 25% just to get a bit more motor power (and not necessary battery time).
She can fairly easily push 200w for 3-4 mins. But I will check the Bike Calculator and play around with numbers
There’s a difference What you Can push and What you want to with a kid on the back. If she wants to, she push 200w and travel at 10mph on the steepest.
Another point, there’s a difference in max speed between the two, Living in Europe e-bike power is limited to 250w and/or 25kph, whatever comes first. Rules might be different elsewhere.
However, the NM figure itself it plenty for a bike.
To put it into context, a 2018 Toyota Prius max torque is 142nm, a lot heavier, but a lot higher RPM.
1HP = 0.75kW
(NM x RPM)/5252 = HP
Prius: 95HP, 142NM (not at same RPM)
50NM motor: 250w (0.33HP)
65NM motor: 300w (0.4HP)
Another point, there’s a difference in max speed between the two, Living in Europe e-bike power is limited to 250w and/or 25kph, whatever comes first. Rules might be different elsewhere.
The 250w limit also has some pretty big wink, wink happening, especially with the high spec Bosch motors. They won’t officially say it, but the regulations are somewhat loose in their wording, so they find a way to stay at the 250w max.
I’d probably go with the higher spec motor if you have hills like that. We have an Urban Arrow with the Bosch performance line motor (65nm) so we are hauling a ton more weight around, but the few times I’ve taken it on a hill near that gradient, I can see the advantage of the next level up (would have been the CX when we bought it with 85nm).
Forget the math, listen to the bike shop and people that have actually ridden one. We have an ebike with Bosch Active (like 40NM) and it provides plenty of boost for almost anyone. If wifey actively rides a road bike then I think she’s likely to not even put it in turbo mode as it is too easy. My 12yr old son is heavier than her and he rides it up some pretty decent hills with no effort at all (doesn’t even shift into low gear). Ebikes are heavy to begin with, the weight of the toddler/seat aren’t going to matter very much.
Thanks a lot y´all! I just did a more thorough study of the hills leading up to our house, and I guess it´s my memory playing tricks with me, when I come home after a long day in the saddle, these hills feels VERY steep
Below is the actual climb from the beach to our home in the hills, set on Strava:
At 2 places it hits 11-12% but only for like 100-150m
In believe she can easily power over these, but we get to test a 40 Nm Cannondale in a couple of days, and if that does the job, then all is settled.
Junior weighs in at 11.5 kg now at 21 month, and is expected to be around 15.5 kg at 3.5y of age. By then I well get him a tag along bike like this, with a PM installed so he can help propelling mum forward
All the engineers are missing the forest for the trees. This is a relatively simple question, and it doesn’t require a slide rule or calculator. I respectfully suggest the focus should be on whether transporting a two-year-old in a bike seat is really safe. I submit it is not a safe way to transport your most precious cargo (and I did it with my son when he was that same age). Bike seats offer little protection in the event of an accident. Both Consumer Reports and the American Academy of Pediatrics recommend a trailer over a child bike seat. https://www.consumerreports.org/cro/news/2009/05/bicycle-seats-vs-bike-trailers-for-children/index.htm
“The AAP believes that a mishap at any speed on a bicycle-mounted seat could cause significant injury to a child.”
So, I am buying my wife an eBike to take our 2y toddler on a child-rearseat to school.
We are looking at an either CANNONDALE ADVENTURE NEO 1 EQ or an CANNONDALE ADVENTURE NEO 3.1 EQ
One concern is if we have enough Nm to take them safely up the climbs to our home, which is some places are 15-18%, but only for like 200-300m.
Wifey is fit and can easily climb those hills on her roadbike. The question is, whether either of these bikes produce enough extra power to help her up.
The NEO 1 is aiding with a max of 65 Nm and the NEO 3.1 only with 50 Nm. I only understand watts how does that translate?
She is 50 kg, the bike is 14 kg and our boy and childseat is 20 kg.
Can anybody help if the 3.1 with 50 Nm is enough? Our LBS says “easy” but is not willing to let us test the hills … bummer
Price difference is around 1000 EUR.
There are lots of child seats and trailers in the US. In fact, I often see people pulling their dogs in trailers. People are strange in the US.
I was not being critical of you in anyway. Sorry if my post came off that way. As I said, when my son was young I rode with him in a child seat. Several accidents later (including one requiring a nine day stay in the hospital— but thankfully none involving my son), I think it is too risky. In a bad accident, a child’s head and neck are no match for the weight of a bike and child seat. That’s just common sense. Good luck.
A quick Google search found an article in a Dutch publication about the safety of toddler bike seats. Interestingly, none of the many, many toddlers pictured in the article (and accompanying videos) are wearing helmets. Not one. That strikes me as careless. https://bicycledutch.wordpress.com/...ing-with-a-baby/amp/
No offence taken I appreciate your input! We would always put a helmet on our kiddo.
We have been using a Babboe E-Curve Cargo bike so far, but not enough motor power over this heavy bike.
We have been using a Babboe E-Curve Cargo bike so far, but not enough motor power over this heavy bike.
Ah, this has the 250w motor and the bike weighs 70kg? That’s interesting. You could probably make an estimate of how much human power input you (or your wife) would need to get up the hill, and that might help clarify which motor would work for you.
A quick Google search found an article in a Dutch publication about the safety of toddler bike seats. Interestingly, none of the many, many toddlers pictured in the article (and accompanying videos) are wearing helmets. Not one. That strikes me as careless. https://bicycledutch.wordpress.com/...ing-with-a-baby/amp/
There are a lot of wonderful things about biking in Amsterdam, but some of the individual practices tend (from my perspective) skew towards riskier because there’s so much less danger from car traffic. The “kid standing on the rear rack holding the rider’s shoulders” (scroll down in this article) was one I saw at least once on most rides and certainly felt quite risky - I guess the kid would have to jump off in an emergency stop situation. There are also a lol of basket bikes that people use with really little kids - we personally use a helmet for our daughter in ours, but I also see how they’re more protected in that type of bike.
how does that translate?
But never touched on these things in practice for 30 years!
