Astroflight Cobalt 05 direct drive compares to what??

I have an AstroFlight Cobalt 05 direct drive motor in a Midwest Electric Hots that I am tired of flying . I was thinking on picking up something else, but most everything I see uses either the smaller 180/280 motors or a Speed 500. Since this is the only electric I have owned, is the Astro 05 comparable to the Speed 500? Can I interchange their usage? I run it on

7-cells (8.4v).
Reply to
Trowelfaz
Loading thread data ...

A Speed 400 is not even close to the Astro 05 Cobalt. Most Speed 400's are in the neighborhood of 35-50 watts. The Astro 05 is somewhere in the 350-400 watt range and probably

5-6 times more thrust. This is pretty close but you can go to the Astroflight site and can get all the data on it.
formatting link
Hobby Lobby has a number of Speed 400's and they have all the data on these.
formatting link

Ken day

Reply to
Ken Day

The specs on the Astroflight website:

formatting link
show about a 200 watt output on 7 cells. That's a bit more than the Graupner Speed 500 Race series (150 watts) and better than a plain speed 700. I suggest a Astro gearbox and a 12x7 prop for some kick in the rear power.
formatting link

30 amps is about right in my experience.

-- Michael 'Fritz' Blackburn VP-94 Techrep NAS New Orleans

formatting link

Ken Day wrote:

Reply to
Fritz Blackburn

That puts the Astro in teh speed 600/700 class or better.

Similar to a hottish buggy motor roughly.

Reply to
The Natural Philosopher

So basically, if a kit requires a Speed 500, my Astro 05 Cobalt would more than suffice?

Reply to
Trowelfaz

Oops ! Sorry. I misread your post. Thought you said Speed 400. I guess I better keep my specs on. It's much harder to make a comparison on electric motors than on glow because there are so many variables, especially in the "Speed" series. You really need to compare the watts. It will vary so much within a particular motor size such as the "Speed" series. Most all the sites will post the data on the motors. Look for the "watts" and make sure you are comparing "input" to "input" or "output" to "output". Battery voltage x the amps the motor will handle determines "input" watts. eg: 8 cells x 1.2 = 9.6. 9.6 x 35 amps=336 watts. Actually since you have a little more than 1.2 volts per cell that would really figure a little over 10 volts.

The "output" watts is another story altogether. A lot of energy is lost as the current passes through. Some motors , especially brushless are much more efficient and the output watts will be at a much higher ratio.

As far as direct drive goes , this is mostly used on pylon racers turning a small prop. In most all cases a gearbox swinging a larger prop is the most efficient and powerful.

I'm sure a lot of the things I said here need to be "tweaked" but this will be in the ballpark.

There is some sofware available that is a tremendous help in working with electrics. One is " Electricalc" , the other is "Motocalc" I have used both and I have Motocalc. I like them both.

H>

Reply to
Ken Day

Yup.

Looks like a 7x5 prop on 8 cells will be nice on that without a gearbox.

Reply to
The Natural Philosopher

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.