martyn sharp Posted March 25, 2009 Share Posted March 25, 2009 I,m hope some one can help here I want to use brushless motors with 3 bladed props i know i need to increase the power setup to compensate but not to sure how i would go about calculating what i need any advise would help thanks in anticipation Martyn Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 25, 2009 Share Posted March 25, 2009 The effect of using a 3 blader instead of 2 will be to increase current. I have no data to hand, but would expect an increase in anything up to around maybe 40% or so. You will need to ensure your powertrain is capable of handling that, and merely reducing volts to compenaste may not be a good idea, as the efficiency of 3 bladers is generally less than 2 baldes. Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted March 27, 2009 Author Share Posted March 27, 2009 Thanks timbo, I,v been offered a couple of these with 30amp ESC there is not a lot of data, on them I was thinking of 8 x 6 master airscrews I could put a 4s or a 3s in but im not to sure if it would over powerd so if anyone can advise please do so. Martyn Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 27, 2009 Share Posted March 27, 2009 Well the prop range stated is 10 X 6 to 11 X 7 so I would assume the 10 X 6 is on 4S and the 11 x 7 on 3 cells. If so, then a 3 blade 8 X6 should be fine on 4s On 3s... it may in fact need something a little larger to get the power up. Really, the only proper way to know is with a wattmeter, but if you simply must rig it up without one, then just check that the motors are not getting too hot. Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted March 28, 2009 Share Posted March 28, 2009 A 500 Watt Twinstar? Mine will slide off ground in six feet and go near vertical on 250W. At full power anything other than gentle manoeuvres get the wings curling into a semi-circle, so you might want to think about laying some carbon into the wings. Good luck and keep us posted. Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted March 28, 2009 Author Share Posted March 28, 2009 Yes Timbo I guess a watt meter is on the cards to do some testing that's the beauty of this hobby its not just build and fly .Rob you set be thinking 500 watts is a bit high I know they the Sky's the limit but the moon!!!! maybe a lower Watts motor would be better some thing like this BRC do do a fact sheet but not for 3 bladed I think, and I,m not to sure if the KV is a bit high.what do you think Timbo ? (sorry Timbo picking your brains like this) i want to put a undercarriage on and paint her but i don't think it will add to much wight but maybe some drag but i do like the Ider of carbon on the wings in any case. Martyn Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 28, 2009 Share Posted March 28, 2009 Ooops forgot it was Twinstar you were doing! Rob is right, thats far too much for it in stock form ( I alwyas disliked the model but thats another story ) Yeh that motor should be Ok, but IMO its still a bit OTT for this model....however as I say, tis not one of my favs, so I cant drum up a lot of enthusiasm for it. Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted March 28, 2009 Author Share Posted March 28, 2009 well thanks for the advise anyway Timbo i heve a few models that are not on my top ten list i wll have to test and see what will happen all the best Martyn Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 28, 2009 Share Posted March 28, 2009 Sorry Martyn - I think my reply was a bit off hand and not terribly helpful I dont know what other mods you are planning for the Tstar, so AUW may come out differently to planned weight. Remember that increasing weight of foamy models increases their chance of breaking considerably and in most cases does nothing to improve performance, in fact the old modellers motto of "add lightness" still applies. I never saw the Twinstar as performance type machine - at all. It was designed as absic intro to electric flight at lowish cost, and is designed around brushed speed 400 can motors. I modded a friends once by leaving the motors and props stock, and fitted a 3s LiPo - the performance improved A LOT, but of course the motors dont last long then. IF I was to do anything on the model, I would fit a pair of cheap and cheerful bell outrunners, and a medium capacity 3S ipo of say... 2000 m/a. Fairly high Kv motors will be fine if you stick to the small props ( gunther push ons if I remember correctly ?) BRC will have several suitable ( one example linked to above ) combos - keep it budget stuff mate Hope that helps a bit more... Edited By Timbo - Moderator on 28/03/2009 08:59:50 Quote Link to comment Share on other sites More sharing options...
scott cuppello Posted March 28, 2009 Share Posted March 28, 2009 Use a pair of CF2815 [Amps will drop using GWS 3 bladers, they really are in-efficient] or if you really wish, the 2212-10, it's not a bad choice as with those props you are on around 150w per motor [down from 170w on 7x5 APC].......my only question is, will it take 8" props? I was always under the impression they were too big, but could be wrong. Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted March 28, 2009 Share Posted March 28, 2009 My Twinstar is fitted with a pair of these which fit into the supplied motor mounts with just a bit of trimming for clearance. You can run 8" props but ground clearance is marginal. I run7X5" (one tractor and one pusher) which give ample power. Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted March 28, 2009 Author Share Posted March 28, 2009 Thanks to all, don't worry Timbo you must get asked lots of questions every day and if its not your area of interest, and its to your credit that you manage to help so many . Well I understand ! but advised has been taken, got a watt meter this morning. Scott i think it will just about take 8"props but I,m wiling to go smaller if needed I car,nt find the CF2815 on your website (while and if your reading this pass my thanks on to the rest of BRC for great service I got when i ordered some kit from you) Rob are you running 2 or 3 blades on your twinstar ? again thanks Martyn Quote Link to comment Share on other sites More sharing options...
scott cuppello Posted March 28, 2009 Share Posted March 28, 2009 Like I said though, if you want to run 8x4 three blade props, I would use the 2212-10 that you already picked out, you really need 14-1500kv on this model, 1100kv as suggested is really low, especially for 7" props. The most popular fitment [7x5 props APC] for this model is a pair of; CF2812....not 2815! Hence the confusion, sorry....so many motor numbers in my head.... Edited By Timbo - Moderator on 28/03/2009 19:45:11 Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted March 29, 2009 Author Share Posted March 29, 2009 Thanks Scott I know what you mean so many numbers ok i will probley go for the 2210-10 with 8x4s i have found a twinstar with 2 Two Esskay 400xt outrunners and Two Master Airscrew 8x6 3-blade props but can not find that much about the Motors watts power ect. thanks Martyn Quote Link to comment Share on other sites More sharing options...
TaZ Posted April 2, 2009 Share Posted April 2, 2009 I fitted 2 WASP BL2835 2700Kv 300W '400/480' Brushless Inrunner Motor with 2 40A ESCs And the black Multiplex props, Take off from grass 6 feet !, climbs really fast and great fun, Loops, Rolls Glides with wind, good all rounder. Edited By TaZ on 02/04/2009 18:30:04 Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted April 2, 2009 Author Share Posted April 2, 2009 600 watts for I bet it flys today i have orderd 2 wasp 2212/10 and 8*4 3 blades so i will post any findings here Martyn Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted April 8, 2009 Author Share Posted April 8, 2009 On Timbo's advise I brought a watt meter to do some testing also from BRC I got 2* 2210-10 with GWS 8x4s 3 blades and then built my self a test rig as i,m hoping to start my sunderland soon so I built on that could take 1-4 motors. With one motor set up i used a 30Amp ESC just in case i believe the recommend on is 20Amp and set about testing this is all new to me so its been a fun filled morning so here are the results 2212-10 gws 8*4 3 blade on a 2s1p 2200 battery was 98 watts @15 Amps 50mAH 2212-10 gws 8*4 3 blade 0n a 3s1p2100 battery was 198 watts @18 Amps 88mAH The 2212-10 is rated at 140 watts @1400 kv . I wish the instruction's were a bit better so I can understand the results a bit better with over a 100 watts more on the 3s1p the reserve will be useful but don't want to overcook the motor so once again help would be useful Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 8, 2009 Share Posted April 8, 2009 A couple of observations Martyn.... The 2s battery appears to not be holding up too well, and with a capacity of 2.2A and a current drawn of only15A thats only pushiung the pack at around 7C, so I would have expected it to hold a higher volatge. I usually expect a pack to hold circa 3.5V per cell minimum under load, so a 2s should be holding at least 7V. Now 7V X 15A = 105 watts so its a bit low but not too far off. It often surpises people just how much difference adding an extra cell makes! The 3s pack seems to be showing about 3.6V per cell, which is more like it. The maths if your interested is simply .... 198Watts / 18A = 11V and then 11 / 3 = 3.66V per cell. You will probably be OK witht the 140 watt motor on the 3s as the current will unload by up to 30% in flight, and these figures you quoted are presumably at WOT anyway. Of course, it would be kinder to run it at abit less, and the only way to do that without dropping to a 2s pack or indeed a different Kv motor is to change the prop. I expect a 8X$ 2 balder woulod sit somewhere inbetween the 2 results you have had so far. If you MUST use a 3 blader, then you will need to change the pitch or diameter, or simply go with it as it is, and be mindful of the current at WOT - ensure good airflow over the motor Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted April 8, 2009 Author Share Posted April 8, 2009 yes I must admit it surprised me the jump from 2s to 3s I,m a bit worried about the 2s it,s brand new (mind you I haven't got a balance lead for it yet it would be so useful for them to be all the same) this has been a learning curive for me enjoyed which i have and thanks for all your help guys I can see just why most use 2 blades I will try it on the 8*4 I don't have the budget to test all different sizes pity there is, a library that you could book out props to do all the testing then return, now I wonder Martyn Quote Link to comment Share on other sites More sharing options...
TaZ Posted April 15, 2009 Share Posted April 15, 2009 Hi Martyn, Have you flown the Twin Star yet ? See mine in my photos, Motors and ESCs still cool from 10 min flight ! . Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted April 15, 2009 Author Share Posted April 15, 2009 Hi Taz no i haven't yet still trying to find a flying club in Poole area that isn't going to cost me the earth, but i.m really looking forward to it. love the roundels on yours where are the from seem to be the perfect size . Martyn Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted April 15, 2009 Author Share Posted April 15, 2009 Hi Taz no i haven't yet still trying to find a flying club in Poole area that isn't going to cost me the earth, but i.m really looking forward to it. love the roundels on yours where are the from seem to be the perfect size . Martyn Quote Link to comment Share on other sites More sharing options...
TaZ Posted April 15, 2009 Share Posted April 15, 2009 Hi Martyn, Roundels are from parkzone Spitfire decal sheet, You in Poole area ! Wife loves Poole, Have you not got some friendly farmers in Dorset ? or some nice beaches , I fly from RAF Bicester and 2 farmers fields nearby so must be lucky, Maybe down your way again soon !, Just had a week near Broadwindsor on a farm Lovely. Take care and watch out for the sun Kev. Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted April 16, 2009 Author Share Posted April 16, 2009 Yes we love it down here in Poole we have been here about 7 years unfortunately i.v been made redundant twice but it's not so bad when you can walk round the coast. yep you are lucky at Bicester i remember i use to fly at Weston on the green in the evenings when i was on duty there. if your down this way give me a shout. fly safe Martyn Quote Link to comment Share on other sites More sharing options...
TaZ Posted April 18, 2009 Share Posted April 18, 2009 Will Co !, 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.