Customer asks a good prop question with implications…..

Hi Dave,

Quick question about the APC props. I note that for multi-rotor the sizes seem to be with 4.5 pitch. Is there a reason why I should not use say, 9×6 with 9x6R for multi rotor craft?

Thanks
David

Answer:
Hovering props or props that produce best thrust in static air tend to be pitched about 1/2 of diameter or less. As you add more pitch, they can fly faster, but have less bite in static air. They can actually be stalled and have less lifting force until the prop gets to moving forward. This is also why props which are the same otherwise make more noise with lots of pitch. Initially they are stalled or partially stalled. So, if you need more prop than a 9-4 to apply the power to the air you have available in your system, you go to 10-4, not a 9-6. Certainly a 9-7 would be such a bad choice as to be worthless.

All this is considering the model is essentially hovering all the time. Even forward flight isn’t quite as forward as an airplane. Other types of flying and machines can have other considerations that make higher pitch (relative to diameter) correct but this is unlikely in all multi-rotors except maybe a racer.

What we call these props is 1/2 square. Meaning pitch is about 1/2 the diameter. A pattern aircraft or war bird might use a 3/4 square (like a 10-7 or 11-8) or even a square prop (like 12-12) because hovering is not a required and speed is more desirable. These setups are poor on hole shot, but once they get moving they really go.

Dave
Hi Dave,

Quick question about the APC props. I note that for multi-rotor the sizes seem to be with 4.5 pitch. Is there a reason why I should not use say, 9×6 with 9x6R for multi rotor craft?

Thanks
David

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Ford C-Max Energi Part 2

A full week on the ticker. Remember the very important point presented in part 1. That point was Ford says to wait at least 1000miles before making any mileage calculations. This implies there may be some break in mixture settings that prevent it from reaching it’s potential for a while. That being said, here are my shots of the data thus far.

Life Time Summary 01/06/13
Life Time Summary 01/06/13

Over 20 miles of driving on engergy generated from braking. 200 miles exactly in pure electric driving. The brakes are interesting. When you lightly press on the peddle, you get a braking action, however it’s really the generator robbing your inertia for energy to charge the battery. As you move down on the peddle you can feel there are about 3 steps in this level of braking (or level of power generation) which each step increasing in rate of power generation and braking force. If you don’t move your foot at all, you’ll come to a complete stop. Obviously, when you are barely moving (moment before you stop) there can be no electronic braking (or little) yet it feels just like the brake pads are stopping you. Some super-brain programming must be managing this and it works perfectly!

Ford C-Max Energi MPG & Miles 01/06/13
Ford C-Max Energi MPG & Miles 01/06/13

Shown here are total miles, state of battery charge and what remains of our first tank of fuel given to us by the dealer. Not bad, close to 500 miles and we have about a 1/4 tank left. Notice, I have changed the mileage calculation. It was at first combined with with electric power. I wasn’t interested in that figure. I wanted to know what we were getting per gallon of gasoline. So, that is now represented. It’s continued to climb all week and as you can see, it’s over 40mpg at this time.

Overall my impression of this car is a “fine ride”. Really enjoying the gizmo factor of playing around with an electric car. It’s as fine a ride as any luxury automobile I’ve ever driven. Comfortable, handles nice, great on the highway. Can’t wait for an excuse to take a long trip in it.

I did run into a couple of irritations this past week. When it comes to any kind of product manual or help file, it seems not to include “my” answer. While switching it from MPGe to MPG I encountered a wrench icon. A retangular yellow light with a wrench in it. Going to the bible like (thin pages and thick!) manual to look over the two pages full of warning icons, I could not find a wrench. Going to the glossary and looking up words like “icon”, “wrench” and “symbol” produced a big fat zero. I’ve come to expect that when I look into any kind of help file or manual. Is a black cloud following me? Probably not. Once I got the setting to what I wanted, the wrench never appeared again. Not sure what it was trying to communicate to me.

The second item is the foot actuated lift gate. It seemed to work iratically, opening partially then stopping at times. I discovered we were using it wrong, wiggling your foot back and forth under the bumper can start it opening and also toggle it to stop. Just sticking your foot under the bumper and pulling it out gets a reliable full open every time.

More to learn: You’ll notice in one photo, a full battery stating it has 12 miles range. We had read this car has about 20-22 miles on battery alone. I’ve still to figure out if this is part of a break in or what the reality is on final full electric range.

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