Steering

So I bought one of these:

 

 And then this happened:

Basically, the pieces have been cut and fit together for steering. The steering holes are not as centered as I would like them, but if they were... well, I'd be a wizard.

The weld nuts need to be welded, as well as the interface between the steering wheel and... pretty much everything. I'll likely pay someone to do it, since it's quick work, and I don't trust myself to make those welds solid. I would also need to cut the steering column to size, and put in a bearing/support to hold it in place (so no, that's not where the steering wheel goes).

Some numbers

I'm going to run a few quick back of the envelope calculations (that I've probably run a half dozen times) here for future reference. Unfortunately, manufacturers of larger electric motors are loathe to give up specific specs. Something about wanting to sell engineering solutions. I don't know.

Regardless, here's some of what I know:

Weight: 54 lbs
Operating voltage : 48 volts
6.1 HP continuous at 48 volts
30 HP peak voltage
125A, 2,295 RPM continuous

Some estimates I'll be using:

1.27 m^2 cross section (based on rough measurements of the largest part of the chassis.
Cd of .4 (After fairings and bodywork have been added. Daniel's estimate, not mine)
density of air (20 degrees c = 68 degrees f) = 1.2

The drag force formula is:
.5 * rho * v^2 * Cd * a

First we'll solve for max continuous speed (based on max horsepower). Work is found by multiplying by distance, work becomes energy by dividing by time. Distance over time is... speed. So the equation for work based on speed is:

.5 * rho * v^3 * Cd * a

Divided by 746 to convert from watts to hp, our equation is:

6.1 = (.5*rho*v^3*Cd*a)/746
6.1 = (.5*1.2*v^3*.4*1.27)/746
v = 24.6236 m/s = 55.08 mph.

So, no long road trips on the highway, but certainly serviceable.

Power usage for other speeds is:

31.3 m/s (70 mph) - 12.53 HP
29.01 m/s (65 MPH) - 9.98 HP
26.9 m/s (60 MPH) - 7.95 HP

Quickly factoring in a 75% efficiency estimate for the motor

55 mph - 8.13 HP - 6.06 KW
60 mph - 10.6 HP - 7.91 KW
65 mph - 13.3 HP - 9.93 KW
70 mph - 16.7 HP - 12.47 KW

Divide this by DC voltage (48) to get current

55 mph - 126.25 A
60 mph - 164.79 A
65 mph - 206.88 A
70 mph - 259.8 A

And dividing by MPH
55 mph - 2.295 ah/mi
60 mph -  2.747 ah/mi
65 mph - 3.183 ah/mi
70 mph - 3.711 ah/mi

long story short, velocity cubed is a bitch.

Progress!

So I haven't posted much because... I haven't been able to do much worth posting about. Most of my time has been spent trying to drill steering holes through the uprights.

Then I got tired of that, so I mounted the accelerator.Woo.