Research Question: Speed of Motorized Bike Uphill

[saralynjenkins]

Hi everyone!

I am currently working on a research project for the college of engineering at my school and I am trying to calculate the power that a standard bike kit motor would provide when going up a certain incline compared to a person pedaling up this same incline. I know that I can find the average power output of these engines, but I have been using a set of equations to verify this and I need some general info.

Does anyone have any information or even logical guesses to the average speed that their bike with an attached motor will go up a hill with? I know I had seen somewhere that the average speed is around 25-30 mph but I am assuming that this value is for flat ground? Again, it doesn't need to be exact, I am just trying to get a grasp the concept. If you have the RPM value instead of speed that would be even better, otherwise I will convert it.

Thanks!
- a curious college student

 

[DAMIEN1307]

I am trying to calculate the power that a standard bike kit motor would provide when going up a certain incline compared to a person pedaling up this same incline. I know that I can find the average power output of these engines, but I have been using a set of equations to verify this and I need some general info.

There are too many variables to list, such as front and rear sprocket sizes which determine torque vs top speed ratios etc...how much weight combined like body mass/weight and bike weight.

In my case, 215 pounds with bike weighing in at 80 pounds...10 tooth front drive sprocket using a 36 tooth rear drive sprocket...I average 32 MPH going up most hills here in the high desert, 4500 ft above sea level, here in Alamogordo NM, running the leanest needle valve setting on the carbie due to altitude.

Pics of this bike are below...From an engineering interest such as yours, i edited the pics by adding more so you can see what has been "engineered" to make this bike possible...DAMIEN

The first 4 pics are of the front engine mount that myself and a friend fabricated from scratch from 7075 T6 military aviation grade aluminum.

The next 2 pics are of the rear disk brake caliper adaptor from the frame to the caliper made of the same aforementioned material, also hand made or "engineered"...lol.

The 7th pic is of the aviation ADEL clamp used to secure the front disk caliper to the bike frame, also a custom job.

And the last 3 pics are of the bike itself, (as well as my old fat self)...lol...Just click on each image to see enlargened pics...enjoy.

 

[Wrench]

How steep and how long is your hill?
Many guys use a shift kit, allowing them to use gears.

A running start helps but it depends on how steep the hill is to say what mph you'll be going when ya clear the top
From a stop it depends on how long and how steep the hill is.
If it's too steep Pedal assist helps and my speed would be 15 to 20 mph.
As Damien said there are too many variables

 

[DAMIEN1307]

How steep and how long is your hill?
Many guys use a shift kit too allowing them to use gears.

Wish i knew how to calculate the "grade" of these hills going up to the foothills, i just know im in NO shape to pedal my fat butt up there and im using a single speed bike, a Hyper beach cruiser with the Zeda 80 motor...lol...DAMIEN

 

[Wrench]

Wish i knew how to calculate the "grade" of these hills going up to the foothills, i just know im in NO shape to pedal my fat butt up there and im using a single speed bike, a Hyper beach cruiser with the Zeda 80 motor...lol...DAMIEN

Nowadays I avoid steep hills too, I always take the easy grade
Pedal assist up steep hills (mountains) ain't no fun and it's not necessary where I ride 99% of the time
Plus I hate to stress my motor and clutch

 

[DAMIEN1307]

Pedal assist up steep hills ain't no fun and it's not necessary where I ride 99% of the time

Thank God i only have to slightly pedal assist at a full stop like at stop signs or signal lights or when some idiot doesnt give right of way...lol...DAMIEN

 

[Wrench]

Thank God i only have to slightly pedal assist at a full stop like at stop signs or signal lights or when some idiot doesnt give right of way...lol...DAMIEN

I always pedal assist from a stop It's good to be nice to the engine.
With my centrifugal clutch I can just twist and go. But with pedal assist my take off speed is increased.
I'll be going about 17 mph by the time I get across the intersection. It only takes about 7 turns of the pedals.
I cant pedal any faster than 20mph, by then my legs are moving so fast I can't keep up with the bike I don't do that it looks funny
44t front 20t rear

 

[Street Ryderz]

Here's a video of a stock engine maybe making 3 hp with 4:1 internal gearing and 4.4:1 drive gearing on a 26" wheel climbing 830 vertical ft in a 797 ft run, accelerating up the grade to around 7000 rpm or 30 mph with no pedal assisting. I had shot this video for a naysayer whom swore that these engines couldn't climb steep grades without loading up LOL and that's just a well tuned all stock engine, my modified engines can climb that same hill at 50 without issue so as the guy's said there are alot of variables but this give's you a good idea at least.

 

[zean]

That stock engine runs and sounds very good. Say with a 40 or 36 tooth rear sprocket would the engine still be able to accelerate to 7000rpm without pedal assist?

 

[Street Ryderz]

That stock engine runs and sounds very good. Say with a 40 or 36 tooth rear sprocket would the engine still be able to accelerate to 7000rpm without pedal assist?

We'll soon see as I'm putting a 40t on it soon. I don't think it will make much difference though, I have a video here with the same stock bike being ridden by my son and a slightly modified 29er and myself climbing the other side of that run on the street and the 29er has a 36 t gear with it's 29" wheels and I'm running 11/30 gearing with a 27" dia tire.