John Barker Posted April 13, 2009 Share Posted April 13, 2009 I have an Acromaster thats almost finished, with an Turnigy 42-40 900kv outrunner installed. My question is can anyone recommend a prop to suit? Thanks in advance John Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 13, 2009 Share Posted April 13, 2009 Assuming you are using 3s Lipo, then about 11 X 7 should do it, if you go to 4S then either prop back a little or expect shorter flights Quote Link to comment Share on other sites More sharing options...
Former Member Posted April 13, 2009 Share Posted April 13, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 14, 2009 Share Posted April 14, 2009 I run an 11x7APC on my Turnigy 35-42 1100kv & get 38A on a 3S battery so an 11x7 on this motor might be a little small. Looking on the web people seem to use anything from 11x6 to 14x7 although 12x6 & 13x4 seem very popular props for the Acromaster...... It depends on what performance you're looking for & what battery you have I suppose. Start with an 11x7 or 12x6 & work from there.......Just remember the Whattmeter is your friend here..... Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 14, 2009 Share Posted April 14, 2009 13 x 4 crikey thats low pitch eh Steve? Quote Link to comment Share on other sites More sharing options...
John Barker Posted April 14, 2009 Author Share Posted April 14, 2009 Thanks chaps, am i right in thinking that its the max current drawn x the battery voltage = the wattage? The motor advert says its 500 watts+ so im guessing as long as i stay around that figure things will get on ok right? Im using Emax 20C 3 cell packs. John Quote Link to comment Share on other sites More sharing options...
John Barker Posted April 14, 2009 Author Share Posted April 14, 2009 The 3 cell packs are 2100mAh by the way..... John Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 14, 2009 Share Posted April 14, 2009 Correct. However one slightly potentially misleading thing about quoting maximum wattage on motors is that they are designed for a particualar cell count range EG: say 3 - 5 cells or whatever. In this case, with the minimum recommended cell count of 3 ( approx 10.5V ) and the maximum wattage of 500 the motor would be pulling around 50A. However....theoretically one could use 1 cell @ 3.5V and prop it to still reach the maximum 500 Watts but the current required would now be 142 Amps - resulting most likely in the magic smoke and melted windings Quote Link to comment Share on other sites More sharing options...
John Barker Posted April 16, 2009 Author Share Posted April 16, 2009 I have a clamp meter for measuring current but its aimed more at higher ranges, is there a 'common' meter you guys use or recommend? John Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 16, 2009 Share Posted April 16, 2009 Astro flight "Whattmeter" from West London models....or a cheaper version from John at Puffin is HERE Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 20, 2009 Share Posted April 20, 2009 Yep 4" is a pretty shallow pitch but apparently its popular with the 3D guys as it a) reduces torque reaction when prop hanging b) keeps the top speed down. This is what our club 3D expert told me anyway.......when I try 3D flying it is best viewed through those red & green glasses...or even better between the fingers of a hand placed over the eyes!!! I have a 13x4 on a 52 ic powered 3D type model & it certainly does what it's supposed to..ie good pull at low speeds & limited top speed despite the motor screaming away!!! I suppose it depends on what you want the model to do!!!!! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.