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Old May 29, 2001, 10:11 AM
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Aikens's Avatar
Houston, Texas
Joined Mar 2001
255 Posts
Help! Must Resist Urge to Alter New Push-E Cat!

I recently received my new Push-E Cat version 3. Darwin really makes a fine kit! The only thing that I am tempted to do, although I know it is evil of me, it put a more powerful drive system in it. I know that I shouldn't, but the recommended Speed 400 7.2 volt direct drive on a 6x4 prop doesn't look too powerful on E-Calc. Please help! My brain is melting due to my indecisiveness... What should I do???
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Old May 29, 2001, 01:15 PM
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Darwin's Avatar
USA, IN, Fort Wayne
Joined Dec 1996
701 Posts
There's no reason to resist if you don't want to. The V3 was designed to accept anything in the 400 to 480 class.

You just have to be aware of the prop to boom clearance. Remember that the Push-E Cat was designed around the 6" prop originally. For every 1" of prop diameter you add, place a 1/2" balsa spacer between the motor plate and the motor pylon.

The fact of the matter is, you can stick with the 6x4 prop and change the motor to a Velkom 2020-27, an MPI 4013, or go brushless. Most of the new generation of 480 cobalts and brushless motors can be set up with the 6 inch prop to draw around 20 amps. This is about the right amp draw range, and yields a healthy boost in climb performance.

You will need to have a pack of 800ARs or the new CP-1300s to quench the thirst of these new motors, however. Bigger motors and batteries may make balancing dicey.

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Old May 29, 2001, 01:53 PM
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Houston, Texas
Joined Mar 2001
255 Posts
Darwin,

Thanks for the information. I've been wondering about using a larger propeller, with a spacer to move the motor higher. I don't know much about motors mounted above the cg.

It seems that at some point, the motor would be mounted high enough that it would kind of pitch the plane forwards/backwards during sudden throttle changes.

What would be the practical limit for propeller diameter on a Push-E Cat? 8" diameter? 9" diameter?

Thanks in advance,
Aikens
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Old May 30, 2001, 10:26 AM
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USA, IN, Fort Wayne
Joined Dec 1996
701 Posts
I would not recommend any motor that uses a prop larger than 7 inches in diameter direct drive. I have successfully flown an 8x4.5 folder on a 2:1 gearbox with an S400, but that was a much lower power system.

My principle concern is tail twist under load from either the torque offset or the prop wash force on the tail surfaces.
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Old May 30, 2001, 10:40 AM
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Houston, Texas
Joined Mar 2001
255 Posts
Darwin,

I hadn't thought about the torque causing twisting.

How about a direct drive Astro Flight 010? That is light and puts out more power than a Speed 400. According to E-Calc, duration and power would be increased (and $$ too, but what the heck).

-Aikens

[This message has been edited by Aikens (edited 05-30-2001).]
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Old May 30, 2001, 04:30 PM
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USA, IN, Fort Wayne
Joined Dec 1996
701 Posts
I'm making a point of trying to not tell anyone what to do with their kit. Once it's out of the shop, it's our of my hands. My basic premise is that the instructions describe "1" way of building and powering the plane that will work. After that, it's all up to individual predilictions, creativity an insight.

Still, I have a hard time believing that an 010 would be happy with the continuous current requirements for something as large as a Push-E, but, hey, if you got the bucks, have at it. I expect to see all sorts of interesting combinations now that the Cat will accept something other than 400 motors out of the box.
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Old May 31, 2001, 01:17 PM
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Concord, CA, USA
Joined Dec 2000
328 Posts
Currently I am flying my older generation PushEcat with an AP-29 ball bearing look alike, using a 6x2 pro. Using 7x1400AEs and 8x800ARs, I still had to balast the nose.

Actually my favorite motor for this plane has been a Multiplex 480 with 6x4 prop.

We are using it as a club trainer and It has flown virtually every Sunday for years, I'm on the fourth motor.

Great Plane,

Chuck Hill
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