Peter Costello Posted March 14, 2011 Share Posted March 14, 2011 I have been given (lucky boy) a 53" fan trainer that is sturdily built (weighs 3.5lbs w/o battery) and although I have a motor rated at 4000kv I can't get more that 350 watts on max power using 3S 3000ma battery. Main restriction is the size of the prop which is max 6" due to design - there used to be a thread somewhere on the forum for the fan trainer but with ic engine but can't find it (just in case someone didn't know the design - which is unusual for a propped ac). Am using 6x5.5 prop and a 40 amp esc. I need MORE POWER! Any ideas?? Would a 4S battery help? but that would mean v. high revs? Thanks in anticipation!! Peter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 14, 2011 Share Posted March 14, 2011 Yes - try a 4s, and yes the RPM will increae. What motor is it, and are you sure it, and the speed controller can handle the extra current? Quote Link to comment Share on other sites More sharing options...
001 Posted March 14, 2011 Share Posted March 14, 2011 I had a Fantrainer, probably the same one, which I think was by HB models. At that time I had little experience of larger electrics but I came to the conclusion that a 125+mm ducted fan was the answer. As it was already built it would have meant dismantling the fuselage to fit it, so for that and other reasons I sold it on. I do have some photos of a full size one at Farnborough if anyone is interested. Quote Link to comment Share on other sites More sharing options...
Peter Costello Posted March 14, 2011 Author Share Posted March 14, 2011 Tim, Looked the motor up on the net and found that it is only rated at 330w! It was given from a friend so didn't have the spec sheet. This obviously isn't big enough as I would like around 120W/lb as I really want it to zoom. If I use a 4S batt this should reduce the current to keep it within 40W if I increase the power. The question is what motor? Can you suggest something - not too up market as I have exceeded the budget already. Peter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 14, 2011 Share Posted March 14, 2011 Not sure what you mean Peter. For the same Watts a 4 cell battery will use less Amps than a 3s.I dont understand the " keep it within 40 watts thing" Quote Link to comment Share on other sites More sharing options...
Peter Costello Posted March 15, 2011 Author Share Posted March 15, 2011 Sorry Tim, I really meant 40 amps - so I don't have to purchase a new esc. I already have a 4s battery. My theory being that if I get a bigger motor but reduce the current by using a 4S battery I am hopeful that 40 amps will not be exceeded. Any idea of a motor?? bearing in mind a max 6" prop. Peter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 15, 2011 Share Posted March 15, 2011 You wont reduce the current just by using a 4s - you will increase it.What you are actually trying to do is achieve the same or slightly greater watts from a higher voltage, and therefore lower current, but to do this you need a higher wind ( lower Kv motor ). Without knowing the motor type and fitting etc, its difficult for me to advise. Seems a bit odd to have a model of a fantrainer, yet use a prop!How about some pictures, and maybe dimensions of the motor fitting shroud /plate whatever. Quote Link to comment Share on other sites More sharing options...
Peter Costello Posted March 15, 2011 Author Share Posted March 15, 2011 Tim, I understand the original model was ic. There used to be a forum topic on this (with pics) but can't find it (lost my original reply to you when I went looking for it!!). The motor is a GS B36-30-08 rated at 4000kv but only 330watts. If Watts = volts x amps and I increase the volts for the same watts then the amps should reduce? Then if I increase the watts on the already increased volts then the amps should vary a little and hopefully stay within 40amps! That is my theory!! No pics as I am work but if you can find the original thread there are some good ones there. The motor is in the rear of the fuz and is fitted using a standard four pronged star if you get what I mean. I think I need around 400watts spinning a 6x5.5 prop. Peter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 15, 2011 Share Posted March 15, 2011 You're nearly right Anyhoooo, lets see what we can find. This one is rated at 40A so on 3s should do 400 Watts+because of the prop size limits you may need to go 4s, but dont exceed 40A.Best to use the wattmeter and a few different props around the size you need - just to be safe.I assume you have a wattmeter - if not, get on the naughty step. Quote Link to comment Share on other sites More sharing options...
Peter Costello Posted March 15, 2011 Author Share Posted March 15, 2011 Tim, Thanks but you didn't put the link in for the motor! I thought it was only me who did things like that. I am not experienced with props - I thought it was the case that the bigger the pitch the more power?? Would a 6x5 or 4 prop give me more? Please sir I want some more!! Had a watt meter for some years now so escaped the naughty step (smug!) - this time!! Peter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 15, 2011 Share Posted March 15, 2011 ooops.here ya go. You may need a different prop adaptor as this has a 3.17mm shaft.Bigger pitch = more speed, bigger diameter = more thrusteither = more current ( especially diameter) Quote Link to comment Share on other sites More sharing options...
Peter Costello Posted March 17, 2011 Author Share Posted March 17, 2011 Tim, I have just tried a 4S battery and got 400+watts pulling just under 40 amps. So much for the motor rating but it may mean that it won't last very long!! Esc got quite warm so will have to vent it well. Thanks very much for your advice though - may well come in useful if it all goes bang!! Peter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 17, 2011 Share Posted March 17, 2011 The motor rating is only what the maximum its designed to run at - if you throw enough volts at it, it will go to thousands ...but only for a few seconds.If you have good cooling, and only use full power briefly, you may well get away with 400.A 4s battery should hold about 14V, so if your showing 400 watts, thats a current of 28ASomethings not right with the data. Quote Link to comment Share on other sites More sharing options...
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