Power Systems Talk about motors, ESC speed controllers, gear drives, propellers, power system simulators and all power system related topics

Pheonix model Sbach .46 prop help

Old 02-06-2022, 07:38 PM
  #1  
Angler-Hi
Super Contributor
Thread Starter
 
Angler-Hi's Avatar
 
Join Date: Dec 2007
Location: Ft Hood, Tx
Posts: 4,145
Default Pheonix model Sbach .46 prop help

I'm currently building the Pheonix Model Sbach .46....I'm using the recommended Rimfire .46 motor. I'm having a bit of an issue deciding on the prop size. The Rimfire manual for this motor says to use "appropriate" sized prop. That's it. When I look online it suggests a range of 10x5 to 11x5. Maybe I'm feeding too much into it, but a 10x5 seems a little small for this plane. Especially with it being a sport plane. Anyone else ever built this particular model or use this motor than can give me some insight? Thanks.
Angler-Hi is offline  
Old 02-06-2022, 08:31 PM
  #2  
ron_van_sommeren
homo ludens modelisticus
 
ron_van_sommeren's Avatar
 
Join Date: Jul 2005
Location: near Nijmegen, Nederland
Posts: 1,437
Default

Was the prop suggested by the kit manufacturer, or by the motor manufacturer? Always high propload with lowest voltage, to keep current in bounds.
What is motor velocity konstant Kv?
What voltage do you want to use?
And since prop effectivity increase with diameter: what is the max. propdiameter you could use w.r.t. ground clearance?

Intermission
Current drawn is proportional to pitch proportional to voltage≤ proportional to Kv≥ and proportional to diameter⁴ .
Small changes, massive effects.
Some silly, realistic, expensive and hopefully useful examples.

Below an excellent quote about motor selection and powersystem misconceptions, from
brushless motors Kv?.
Originally Posted by scirocco View Post
While an absolutely critical part of the system ...
... Kv is actually the item one should choose last.
  1. Decide your peak power requirement based on the weight of the model and how you want to fly it:
    Magic numbers for modellers.
  2. Pick a preferred cell count (voltage) and pack capacity for how to deliver the power.
  3. Pick a prop that will a) fit on the model and b) fly the model how you want - often as big as will fit is a good choice, but if high speed is the goal, a smaller diameter higher pitch prop will be more appropriate.
  4. Look for a size class of motors that will handle the peak power - a very conservative guide is to allow 1 gram motor weight for every 3 watts peak power.
  5. Then, look for a motor in that weight range that has the Kv to achieve the power desired with the props you can use - a calculator such as eCalc allows very quick trial and error zooming in on a decent choice. For a desired power and prop, you'd need higher Kv if using a 3 cell pack compared to a 4 cell pack. Or for a desired power and cell count, you'd need higher Kv if driving a smaller diameter high speed prop compared to a larger prop for a slow model.
The reason I suggest picking Kv last, is that prop choices have bounds - the diameter that will physically fit and the minimum size that can absorb the power you want. On the other hand, combinations of voltage and Kv are much less constrained - at least before you purchase the components.

So Kv is not a figure of merit, in that higher or lower is better, it is simply a motor characteristic that you exploit to make your power system do what you want, within the constraints you have, e.g. limited prop diameter, if it's a pusher configuration, or if you already have a bunch of 3S packs and don't want to buy more, and so on.

Minor lay-out changes by RvS

Last edited by ron_van_sommeren; 02-06-2022 at 11:55 PM.
ron_van_sommeren is offline  
Old 02-07-2022, 01:49 AM
  #3  
Angler-Hi
Super Contributor
Thread Starter
 
Angler-Hi's Avatar
 
Join Date: Dec 2007
Location: Ft Hood, Tx
Posts: 4,145
Default

Motor is a Rimfire .46 800kv. It was recommended by the model. For 3D planes up to 5lbs and sport planes up to 7lbs. Recommended prop range is 10x5 to 11.5. Wish I knew how to upload a picture of the specs....
Angler-Hi is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ggunners
Flight Simulators
2
10-03-2012 04:30 PM
HobbyJumper
Beginners
7
11-29-2011 10:42 PM
jetsmell
Beginners
10
08-06-2011 01:39 AM
z-8
Off Topic Chit Chat
128
03-09-2011 05:39 AM
solentlife
General Electric Discussions
12
02-14-2011 05:26 AM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Quick Reply: Pheonix model Sbach .46 prop help


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.08110 seconds with 10 queries