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.

Happy Birthday

So last Thursday (the twenty fifth) was my birthday. On the next Wednesday (after being somehow misdirected to Brownsville, TX), my gift arrived.

 Huh. Steve sent me something.

 Big 'ol row of staples

 Second, smaller row of staples

Boom. Motor.

Catching Up

To say I've been keeping very records of this build would be... a tremendous understatement, so in an attempt to make all future record keeping easier, I've started up this blog. From time to time I may put up a few design details that I have tucked away, but this post will mostly contain pictures and information about the build so far.

(9/8/12) This is a picture of almost all of the steel stock we started with - I think there were a few pieces hiding that we had to find later.

 A day's worth of cutting.

(9/14/12) "Stephan, we need to take pictures. Take one of me grinding, grinding looks badass!"

(9/15) We used these little carpentry dealies to hold the right angles together. It wasn't the most secure fit, but it held long enough for us to get a good tack in.

And this is a day's work - all of the bulkheads welded, just waiting to be connected.

 (9/16/12) I'm not entirely sure why we took a picture of this at this point. But it shows a problem we had - the steering wheel fits where it's supposed to, but my hands and the steering wheel do not fit between the two braces. In later pictures you'll see this portion of the frame has been widened by around eight inches.

 Me sitting in the frame with the steering wheel. I look really tired in this picture. I was.

 (9/22/12) Daniel's welding was so hot he blue the bearing cups.

 Completed control arms - it doesn't look like the bushings were put in at this point

 (9/24/12) Frame with lower control arms and shocks mounted - you can see where the frame was widened to allow for the steering wheel. If you look closely, you can also see the brake pedal and the steering rack mounted.

 I took these two pictures to show the modifications we made to the original Integra uprights. The rectangle at the top replaces a much longer piece that was cut off. The portion where steering control is bolted into was filled in to be replaced by smaller holes.

I'm not a great cook.
But really, The bearing cups on the end of the control arms needed to be substantially ground out, and the bearings ground down, then boiled and frozen respectively. Then pushed in with a C-Clamp. "They should just drop in" my ass.

 (10/20/12) - Lots of grinding later, the suspension fits together, with full suspension range of motion and full steering range of motion. The steering gets sticky at the full lower limit of the suspension, which I'll deal with later, when I figure out if it's a problem worth dealing with. And how to deal with it.

  

 (10/27/12) - Because sometimes (rarely) things just work out - turns out I can mount the accelerator directly to the frame, with a little extra bracing for the bottom mount hole.  The way it's set up here is approximately the same as the brake/accelerator setup in my VW.

I can't mount directly to a plate, due to the fact that the accelerator pedal is designed to travel beyond the mounting holes, so this makes mounting the accelerator substantially easier.

 Hah. Dopey ass dog can't even figure out how to sit down properly.