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Author Topic: Where do I go from here?  (Read 425 times)

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Offline cheddar-caveman

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Where do I go from here?
« on: August 09, 2018, 07:59:42 AM »
I am building an old, around 1950's, kit of a Pilatus Porter P6 and am trying to work out the power train.

I currently have this motor,  ila_rendered

with this ila_rendered ESC with a 9 X 6 two bladed prop fitted and running from a 3s battery pack.

When run up to full speed my wattmeter readings are ila_rendered which I believe shows that I am well inside the motor limits?

That being the case, can I increase the prop size, but more importantly, what size 3 bladed propeller would be best?

The finished model should weigh in at around 3.75lbs.
« Last Edit: August 09, 2018, 08:01:07 AM by cheddar-caveman »


Offline PDR

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Re: Where do I go from here?
« Reply #1 on: August 09, 2018, 08:24:19 AM »
According to the specs on Hobby king that's an 18A motor, so that's about as much as you're going to get out of it. It is too small to pull the model you have in mind - you need a motor rated for 40-45A (for 3s) or 35-40A (for 4s). In the Turnigy range you'd be looking at something more like the d3548-4 which (on 3s) should give you all the grunt you need on something like an 11-6 or 10-7 3-blader (but I don't know the specific motor - I'm going by the specs and user reports).

It might also be worth noting that for the "cheap" ESCs the specified currents are often optimistic, so if they claim 40A then it's best to keep your current below 33A, and if you want to run 40A you should get one rated at 50A or above. This only applies to the cheapies - A Jeti, Hacker or Schulze 40A ESC will run at 40-45A all day (in my experience).

PDR
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Offline cheddar-caveman

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Re: Where do I go from here?
« Reply #2 on: August 09, 2018, 08:33:08 AM »
Many thanks PDR, most helpful and just what I was looking for.
Looks like a new motor is on the cards and the bigger props!!

As a matter of interest, does the HK 40A SBEC ESC come under the "cheap" heading???
« Last Edit: August 09, 2018, 09:02:15 AM by cheddar-caveman »


Offline PDR

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Re: Where do I go from here?
« Reply #3 on: August 09, 2018, 12:02:36 PM »
Probably.

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Offline cheddar-caveman

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Re: Where do I go from here?
« Reply #4 on: August 09, 2018, 12:46:46 PM »
 :'( Oh well, see how it fares!

The full sized P6 has a four blade propeller. There seem to be very few available but have found an APC 10" x 6" or 11" X 6". I guess one of these would be Ok with my set-up?


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Re: Where do I go from here?
« Reply #5 on: August 09, 2018, 12:59:11 PM »
Would depend entirely on your choice of motor and battery.

Personally I wouldn't bother - you can't see any difference in the air, it wouldn't be the scale soze on the ground, and they are EXTREMELY easy to break (on blade is always pointing downwa5rds when you nose-over). You're better off with a bigger 2-blader.

For reference - if you want the multiblade prop that is "equivilent" (similar loading, thrust) to a 2-blade one you keep the pitch the same, but a 3-b;lade prop needs to be 10% smaller diameter than the 2-blade and a 4-blade one needs to be 16% less diameter to give a similar loading/performance.

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Offline cheddar-caveman

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Re: Where do I go from here?
« Reply #6 on: August 09, 2018, 14:40:54 PM »
Yes, thanks! Just bought the two blade!  ;)


 

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