jawnn

I am trying to find out if a 500watt motor connected to the drive chain like the Ecospeed motors will move 450 lbs up a 16% grade when using a NuVinci continuously variable gear hub. With out over powering the motor…that is I don’t see how the motor can run fast enough to keep from over heating. 2 or 3 mph will be enough for a trike but no less than 3mph for a bike with trailer.

I climb these hills with 400lbs less than 2mph, by leg power alone. I tried using Sheldon Browns gear calculator but it did don’t explain what the number are.


This is what I do with my legs and gears that I have.

18 front / 34 rear sprockets = 1 to .53 ratio .............
60 rpm’s at the crank x (.53) = 31.76wheel rpm's..............
62.8” circumference x 31.76 rpm's = 1994.82 ipm ..............
Divided by 12 = 166.235 fpm ..........
166.235 x 60 minutes = 9974.117 fph ............
Divided by 5280 = 1.889 mph.........

my blog is called 'commuter cycling technology' if any wants to see where I'm coming from.

Allen

I don't have a grade that steep but I've pulled 400 + on my Giant Twist (inline motor) and a NuVinci.
The Giant has a 350 watt motor and it does not overheat.

misslexi

I guess it depends on how you couple the motor to the load. You want the motor running at it's most efficient speed, if you are at a point where the motor is running too fast, it's time to gear down. If by doing that you aren't moving at the right speed then the coupling gears aren't right. Not to state the obvious but the Ecospeed system's motor does not directly drive the bike's gears.

jawnn

what grade do you think it may be? you could messure it with a level and a ruller. My hill is 3.2 " rise over a 20 " span.

crackerdog

Jawnn, that small bike you tried a year ago or so was a 500 watt motor. Since it was driving the gears, I would imagine it would be in the same ballpark.

jawnn

The Nuvinci gear-hubs for bicycles are worse than useless, they can't handle more than 26 gear-inches of torque with human legs meaning that any motor will make them slip. :shout:

The maximum torque before it starts slipping is 130Nm or 96 LbFT . One wheel revolution to one crank revolution is the lowest gear possible.


Some one told me they saw a video of some guy jumping on the pedals, and thought that it showed how strong the thing is. All it really shows is that it takes much more leverage to move in higher gear. And it shows how strong the chain is; I have torn chain links just climbing hills in low gear.

However there is an application that my be useful; let the motor do the job of bringing the bike up to a speed that you can pedal in high gear. the motor will have to be connected to the other side of the wheel.

Allen

Not my experience with them.
Mine has never slipped and I have an inline motor.

Where are you getting your information?

Allen

Not my experience with them.
Mine has never slipped and I have an inline motor.

Where are you getting your information?

jawnn

I am not getting enough info....from any where.....I can't find photos of the nuvicni set up for steep hills because every one concentrates on speed not hills.

Even the manufacturer will not give me what I need.

Llamero

I can't remember where, but I found a trike manufacturer that sells gas/electric trikes with Nuvinci and Rholoff transmissions. However, the manufacturer puts both of these hubs into the drive train rather than the rear wheel, most likely to keep the torque within reasonable specs on the transmissions themselves.

Llamero

Here's the link to the NuVinci gas powered trike: https://www.utahtrikes.com/RECENTTRIK..._Gas_Quad.html The electric/Rholoff variants are just elsewhere on the site.

Allen

https://www.bikeforums.net/showthread...i-gearless-hub
You got several in depth answers to your cross posting of this thread in the Utility section.

CowtownPeddler

An idea for measureing grade would be to use a piece of string. Make a big loop and secure two points on the hill with some weight, make a triangle of the string and then it's a matter of geometry. If you use a plumb bob for the downhill side and line its line with the string "triangle", it should be easy to mark the anchor points and the angle on the downhill side. Once there, A^2 + B^2 = the length along the ground, then use trig to get the angle of the slope.