Yet another screwed up order! - RC Groups
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Mar 11, 2002, 10:26 AM
Registered User

Yet another screwed up order!

About 2 weeks ago I inquired with Cyberheli about a Plettenberg 300/25/A3 heli motor for my Logo 20. They said yes they have them in stock. Great, I said, I'll take one of those! I send the necessary info via email and I get a reply back stating "Sorry, I've caught the HK flu and have to lie down for a while, thanks for your patience and understanding." What does this mean??? I reply back asking if this means my order will not be fullfilled. No reply. A few days later I finally get an acknowledgement of my order and an email confirmation.

Today my motor arrived! That was FAST! I was very impressed since this came all the way from the orient. I opened the box and on the outside label it read: 300/25/A4, NOT 300/25/A3 as I had ordered. I figured maybe it was just shipped in the wrong box. I open the box up and on the motor label it reads: 300/25/A4!!!! I know the A4 is rated for 20-24 cells, but how does it compare in terms of power? My Logo 20 has a 9-tooth pinion. Should I keep this motor or send it back?
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Mar 12, 2002, 02:30 PM
Registered User
Does anyone use the HP 300/25/A4 Heli motor? How does it differ from the A3?
Mar 12, 2002, 03:42 PM
Suspended Account
If you go to the Plettenburg web site you can get the datasheets on the two motors.

It looks like the A3 has a higher Kv and is the 3D motor while the A4 has better duration for hovering FF.

It is all in the datasheets.

Mar 12, 2002, 03:45 PM
Registered User
I suspect the KV of the A4 is a little lower than the A3. Looking at the specs the A4 is designed for 24-26 cells where the A3 is designed for 20-24 cells. This is typical for motors of similar size/weight to have higher cell count capability and lower KV.

I don't have a pletti motor but have seen an excellent set up with the A3 in it. On 24 cells and 9 tooth pinion the power is amazing. I would hazard a guess that you would have to go to 26 cells and a 10 tooth pinion on the A4 to get similar performance.

I can't find anywhere where it is actually specified what the Kv for the motors is though so I am only guessing here!

Mar 12, 2002, 03:49 PM
Registered User
You found the Kv in the datasheets? Where? I couldn't find the typical motor constants you normally get with motors. Kv, Io, etc.

There was some datasheets of motor performance at certain voltages and load (I think that's what it was, they were in German but my brain is in English).

Mar 12, 2002, 04:11 PM
Suspended Account
The column headings are:

Amps (current)
performance in (watts)
performance out (watts)

Divide RPM by the voltage at the appropriate range of voltages you expect to use to get a very accurate Kv.

So for 20 cells use 24V at start to 22V at shutoff.

Last edited by bradpaul; Mar 12, 2002 at 04:13 PM.