#B152 Bike Diary (More Testing)

                        W/O trailer                trailer w full load     

Ride length:       24.59 km                       24.48 km             

Time:             52 min 29 sec                51min 19 sec    

Av. speed:         28.1 km/h                      28.60 km/h          

Power usage:

                            6.85 Ah                          9.81 Ah              

                        386.06 Wh                     501.27 Wh        

                         15.70 Wh/km                  20.60Wh/km  
  

Max speed:       45.0 km/h                       35.50 km/h 
          
Start voltage      58.10                             58.10                    

Finish voltage    53.00                             50.90                   


                            trailer no load    full trailer w/o batteries

Ride length:            24.60 km                 24.61km

Time:                  51 min 28 sec          52 min 1 sec

Av. speed:             28.6 km/h                 28.30 km/h

Power usage:

                              7.92 Ah                    8.73 Ah

                          414.39 Wh               447.00 Wh

                            16.70 Wh/km           18.20 Wh/km

                     

Max speed:         42.90 km/h              36.70 km/h

Start voltage       58.10                       58.10

Finish voltage     52.00                       50.90

Tonight's test was to find the energy cost of the trailer with all battery boxes in order to estimate the energy loss from the additional aerodynamic resistance. The trailer was without any batteries. So we had the full aerodynamic losses with very little additional inertial losses. This will allow us to subtract the rolling resistance  (1 Wh/km) plus aerodynamic resistance from the total load of the full trailer (4.9 Wh/km). Logically, this result can only be for the inertial resistance of the remaining load.

Tonight, with the added aerodynamic resistance, there was an added 1.5 Wh/km of energy consumption. Therefore, 4.9 Wh/km total trailer resistance minus 1.0 Wh/km rolling resistance leaves 3.9 Wh/km. Subtracting 1.5 Wh/km of aero losses leaves 2.4 Wh/km as the energy cost of transporting the remaining 90 lbs of cargo or .027 Wh/km per lb.

The total weight of the bike, rider, trailer, and cargo is 76 lbs, 255 lbs, 19 lbs, and 113 lbs (90 lb battery + 23 lb battery boxes), respectively for a total 463 lbs. Total rolling resistance energy needed to move this weight at 28 km/h is (463 lbs x .027 Wh/km/lb) 12.5 Wh/km.

Rolling resistance of trailer is 1.0 Wh/km but this is with 19 lbs of added weight. The 19 lbs of added weight use up (19 x .027) .5 Wh/km leaving .5 Wh/km for rolling resistance.

Since this figure is for two wheels on the trailer there is no reason not to conclude that the bike's two wheels have the same resistance. So the total rolling resistance for a loaded bike and trailer going 28 km/h is 1.0 Wh/km.

Total energy for the loaded bike and trailer at 28 km/h is 20.6 Wh/km. Therefore, subtracting 12.5 Wh/km (inertial or weight resistance) and 1 Wh/km (rolling resistance) leaves us with 7.1 Wh/km of energy use to overcome aerodynamic drag.

Total energy use     = 20.6 Wh/km = 100.0%
Aero resistance       =   7.1 Wh/km =   35.0%
Rolling resistance   =   1.0 Wh/km  =     5.0%
Inertial resistance   = 12.5 Wh/km  =   60.0% 
Just remember: these figures are for a speed of 28 km/h. Someday I will do a series of tests at 35 km/h to show how fast aero drag increases as a proportion of overall drag.

Fun fact: If I lost 60 lb I could save (60 x .027 =) 1.62 Wh/km.
On a 350 km trip this amounts to 567 Wh. That's 75% of another battery. Something to think about.

Update: The Grin computer shows that losing 60 lbs would only save .80 Wh/km or about 280 Wh over a 350 km trip. I think the computer is underestimating the number.

Right now, my brain is tired so I'll get back to this another time.
 

#B150 Bike Diary (Testing)

                        W/O trailer             trailer full load     trailer no load

Ride length:       24.59 km                    24.48 km              24.6 km

Time:             52 min 29 sec             51min 19 sec     51 min 28 sec

Av. speed:         28.1 km/h                   28.6 km/h           28.6 km/h

Power usage:

                            6.85 Ah                       9.81 Ah              7.92 Ah

                        386.06 Wh                  501.27 Wh         414.39 Wh

                          15.7 Wh/km                20.6 Wh/km        16.7 Wh/km                          

Max speed:       45.0 km/h                    35.5 km/h           42.9 km/h

Start voltage      58.2                            58.2                    58.2

Finish voltage    53.0                            50.9                    52.0

Above is my Wike heavy duty flatbed trailer.

Weight 19 lbs.

Carrying capacity 125 lbs.

Tonight's test was to find the energy cost of the trailer's rolling resistance. The trailer was without any load and the aerodynamic profile was nearly zero because it is only a platform with no sides.

At an average speed of roughly 28 km/h the trailer adds about 1.0 Wh/km over the bike without `the trailer. Since the difference in energy consumption between Bike Alone and Bike With Trailer, this leaves the energy cost of the trailer's battery load at about 3.9 Wh/km. This represents the energy cost of the aerodynamic resistance and the added weight.

I will separate these two factors next time out by just loading the empty containers. The empty containers plus trailer weight are about 25%, or so, of the total load weight so, while the new figure will not completely separate out the weight from the aerodynamic resistance, it will still reveal good intel about the effect of weight on overall energy cost. 

Once the testing is complete I will have a very good idea of the percentages of energy consumption for rolling resistance, aerodynamic resistance, and inertial (weight) resistance.
 

#B147 Trailer Test For Parasidic Drag

Without trailer                         With trailer

Ride length: 24.59 km              24.48 km

Time: 52 min 29 sec                 51min 19 sec

Average speed: 28.1 km/h       28.6 km/h

Power usage:

6.85 Ah                                     9.81 Ah

386.06 Wh                                501.27 Wh

15.7 Wh/km                              20.6 Wh/km                            

Max speed: 45.0 km/h              35.5 km/h

Start voltage   58.2                    58.2

Finish voltage 53.0                    50.9

As you can see the two trips were nearly identical for length and average speed. The major difference was towing the 130 lb trailer with batteries, etc. 

The difference in energy consumption was entirely unexpected: it took an extra 4.9 Wh/km to tow the trailer. My original guess of an extra 1 Wh/km was so far off the mark that it is embarrassing.

Without even considering gravel impedance my range is reduced to 364 km and - using an additional factor of 1.5 Wh/km for gravel impedance - my range would be reduced to 340 km. This leaves me 65 km short of my destination. An even worse scenario is that my gravel impedance estimate might just as ridiculous as my trailer estimate.

This KOs the Dempster trip. Bummer.

Note: There is a plan "B" for the Yukon. I will write about it in the next couple of days.