Archive for the ‘Edscort’ Category

Will that motorcycle pay for itself really?

Friday, October 10th, 2014

In deciding whether or not purchasing a motorcycle is a prudent decision, cost plays a significant factor. Motorcycles often get much higher gas mileage (fuel efficiency) than cars. A common belief is that because of this fact, a motorcycle might pay for itself. I wanted to believe this is true, but after running the numbers, this belief is a myth and is only true in extreme circumstances. I’m recording the relevant equations here so that next time I get the impulse to by a motorcycle, I won’t use cost savings as a justification.

In my situation, my everyday car, the Edscort, gets about 34 mpg highway, 30 mpg city. I don’t think I’ve ever seen less than 30 mpg so I’m going to use that figure as the Edscort’s fuel efficiency. The motorcycles in which I’ve been interested have been around $1500 in cost and achieve about 60 mpg. For simplicity’s sake, I will ignore the cost of insurance, maintenance, and accessories.

The cost, c, to drive a vehicle m miles is given by:

eqn1

where f is the fuel efficiency of the vehicle in mpg and r is the cost of gasoline in $/gal. The cost savings Δc is the difference in the cost of driving those miles with the motorcycle (bike) vs. the Edscort (car). A negative value for Δc corresponds to money saved.

eqn2

In order for the motorcycle to pay for itself, the cost savings must be at least as much as the purchase price of said motorcycle, P. That is, -Δc = P, where the negative sign makes a negative cost differential equal to a positive purchase price. The number of miles that must be driven before the bike pays for itself is therefore:

eqn3

In my case, where the Edscort gets 30 mpg, the motorcycle gets 60 mpg, gas is $3/gal (as of this writing, it’s $2.99/gal down the road) and the motorcycle purchase price is $1500, I would need to drive the motorcycle 30,000 miles to break even. And note, these trips on the motorcycle must be in place of rides in the Edscort, not in addition to my usual driving.

To point out how impractical this is, consider that I’m currently averaging about 10,000 miles per year driven. If I can substitute the motorcycle for 20% of those miles, I’ll put 2,000 miles on the bike per year and it will pay for itself in only 15 years. I could cut that to 6 years if I substitute the bike for 1/2 of my normal driving. Ideally, I’d want the bike to pay for itself in 2 or 3 years, but that’s obviously not going to happen.

New bikes are considerably more expensive and I’ve not considered other ownership costs in which case things get even worse. Of course, reducing the wear and tear on the Edscort might stave off a significant repair bill, but there’s no guarantee that’s the case. Nor is there a guarantee that the bike won’t need a major repair itself.

The bottom line is that cost savings cannot be used to justify the purchase of a motorcycle. The decision to buy one is not a practical decision. Face it.

Replacing the Edscort’s broken wiper switch

Saturday, September 7th, 2013

Eventually the Edscort will have its own page, but until then, a small introduction is in order. The Edscort is a 1998 Ford Escort ZX2. We have a long storied past and I have no plans to change vehicles ever. So, when something breaks on the Edscort, and it is something necessary for continued safe operation, it gets fixed. This post details how I went about repairing a broken wiper switch.

slider top view slider bottom view

It’s not important how the switch broke, but it involved significant force being applied to the long wiper switch handle protruding from the steering column. The leverage broke the small brown plastic component inside the switch housing as well as the plastic handle itself. Initially I was able to “plastic weld” the brown piece back together and rejoin the the two pieces of the plastic handle by screwing them into opposite ends of a hex nut coupler. Eventually though, the plastic weld gave out and the switch was inoperable again. I would have to do a complete rebuild.

contacts inside switch housing

contacts outside switch housing

By studying the inside of the switch I was able to determine that the small brown plastic piece rotates to make and brake the connections in the following manner:

  • OFF = 5 + 6(4)
  • VARIABLE = 4(6) + 5, 1 + 3
  • LOW = 3 + 4(6)
  • HIGH = 2 + 3

Where the numbers refer to the contacts as shown in the photos and diagram. Using a multimeter I determined that contacts 4 and 6 were electrically connected, as were contacts 3 and 8. This would prove useful as it reduced the number of wires I needed from 10 to 8, the same number found in a length of CAT5 cable. Because there are four settings, I would need at least a 4-throw switch. I ended up ordering a 3-pole-4-throw switch from ebay. It would turn out that a 2-pole-4-throw switch would have worked as well, but I think the 3-pole switches are more common. But note: if you order a rotary switch, do yourself a favor and get one that comes with a knob. I didn’t and regretted it later.

diagram

The diagram above shows how the connections were made to the rotary switch. There are two more contacts on the outside of the switch housing that originally ran through the middle of the wiper switch all the way to the turn knob on the end. The turn knob is simply a 500 Ω variable resistor. I opted to replace this with a 500 Ω potentiometer (got a knob this time!).

The spring contact inside the switch housing connects contacts 7 and 8(3) and activates the spray wash. I wired these to one circuit of a two position momentary switch (SPDT?). The switch has three contacts which are all disconnected in its un-pressed position. When the rocker is pressed one way, it connects the middle contact and one of the end contacts. When pressed the opposite way, it connects the middle contact to the third contact.

There is one remaining function of the wiper switch that I haven’t mentioned. When it was operational and the handle was pushed up, the wipers would come on at their highest speed momentarily.

  • MOMENTARY HIGH = 2 + 3(8)

Since contact 3(8) was already used in the momentary switch for the wiper spray, all I had to do was connect contact 2 to the third and unused contact of the two position momentary switch. Now, when pressed one way the sprayer would activate. When pressed the opposite way, the wipers would come one momentarily. In practice this worked, though there is a slight delay before the wipers come on and the speed isn’t as high as one would expect. I’m sure this is because the rotary switch is in the on position. In other words, I have the MOMENTARY HIGH position wired as follows:

  • MOMENTARY HIGH = 2 + 3(8), 5 + 6(4)

I decided its function was good enough. If I really need high speed I can turn to that position on the rotary switch rather than use the momentary rocker switch.

wired up

With everything working I had to find a way to mount everything to the steering column. I wasn’t able to mount the switches directly to the plastic housing around the column because it fit so tightly (no space inside). I had to mount everything externally. I opted to use the plastic lid of a jar of peanuts because it had the right depth. I used drywall screws to screw the jar onto the steering column’s plastic housing. The CAT5 wire was a good choice because it was relatively thin. There was no extra room for fat wire.

Disappointingly, I found that my momentary switch was to big to be mounted directly to the steering column housing. I ended up cutting a hole through the housing to run the wires and then hot-gluing it flat to the top of the housing. It’s ugly but should work (at least until the summer heat deteriorates the hot glue). Eventually I will replace this switch with a much smaller (less tall) version and mount it directly to the steering column housing. Actually there is probably enough room left on the red plastic lid to mount some tiny push button switches, though it might be a challenge to find ones with high enough ratings.

in place - side view

The final product is shown mounted in the Edscort. You’ll see that for the time being I’ve had to resort to jamming a washer in the slot of the rotary switch until I can find a knob that will fit. But hey, it works, and there is no long wiper switch handle to get in the way of things.