David Wainwright Posted July 9, 2017 Share Posted July 9, 2017 Hi.Excuse ignorance as brand new to this hobby so please speak in dim terms although I understand a little.I have a 30" carbon prop I want to get spinning over 10,000 rpm and run off a speed controller (have 70a one) and 12v lithium car battery. What kind of motor would provide enough torque and speed to achieve this please? If you're wondering, I'm building a simple paraglider fan rig. After experimenting with an 8inch prop and a cordless angle grinder I was pleasantly surprised with thrust. Any tips in simpleton language please. Lol. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted July 9, 2017 Share Posted July 9, 2017 To get 10,000 RPM from a 12v supply with an outrunner you will be looking for a motor with a Kv rating of between 800 and 850, but to spin a 30" prop at 10k..... the norm for that sort of motor would be in the region of 11 to 13" prop Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted July 9, 2017 Share Posted July 9, 2017 Whats the propeller pitch, if that is known you can work out the power required. BTW my 18" dia by 10" pitch prop runs off a 30v battery. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted July 9, 2017 Share Posted July 9, 2017 Spinning a 30 inch prop at 10,000rpm would send the tips supersonic....interesting but not recommended....I doubt it would be strong enough to withstand the forces involved...I also think you would need several kilowatts of power to get anywhere near that sort of speed....Something is not right in the OP...are you sure it's not a 30cm prop? That would be about 12 inches & things start to make sense.... Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 9, 2017 Share Posted July 9, 2017 To get 10,000 rpm under load from 12v the motor kv would need to be about 1050. A safe current limit using a 70A esc would be about 60A. Therefore max power (input) would be around 720 Watts (just under 1HP). Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Hi. This is the propeller I am using.Look at this on eBay http://www.ebay.com/itm/182365314044 Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 30" x 10" carbon prop not metric Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Hi. 30" x 10" carbon prop mate. Thanks. Quote Link to comment Share on other sites More sharing options...
MattyB Posted July 10, 2017 Share Posted July 10, 2017 OP, forget rpm for now; what is your target pitch speed (the max speed of the airflow coming off the prop)? To calculate tell us the max speed you are looking to attain under power, then add 20-25%. Once we have that we can work out the rest more easily. Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 10, 2017 Share Posted July 10, 2017 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted July 10, 2017 Share Posted July 10, 2017 Hacker list a motor.the A150-10 that will spin a 30x12 at 4500 rpm. But that requires 49 Volts at 180 Amps. That's 8.8Kw for less than half the rpm requested. Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 10, 2017 Share Posted July 10, 2017 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 10, 2017 Share Posted July 10, 2017 Hi David, Assuming this prop has a average sort of pitch value you might expect, I'm afraid what you are asking for isn't practically possible with that battery - the current needed to deliver 10,000rpm would be huge!! Orders of magnitude beyond your 70A Speed Controller! That prop and that battery are just not a compatable pair. It would make a lot more sense technically to start with the question "How much power do you need to fly this paraglider?" We could then work out a sensible prop/ESC/battery combination. BEB Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Wow. Looks like I may be using this as a ceiling fan then lol. Not sure about calculating stuff but wanted enough thrust to push around 90kg through the air so what rpm needed for 30x10 prop is unknown factor to me. Main objective is to simply achieve thrust. Obviously weight is a factor so wanted to keep battery weight low as poss. Just thought would be interesting feasibility project before having a go. Thanks for all input so far. Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 So which set up would you guys say would power it with substantial thrust? Looks like I'm back to drawing board. Oh well. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted July 10, 2017 Share Posted July 10, 2017 OK David Current electric paragliding uses 15kw set ups This is about 20 HP Petrol set ups are well established, and electric flight is gathering pace with the use of carbon fibre and lightweight power packs Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 10, 2017 Share Posted July 10, 2017 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
onetenor Posted July 10, 2017 Share Posted July 10, 2017 I would try a recliner chair motor Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Actually they are about 4 hp. Even the petrol ones aren't double figures. Original question did say I was after a basic device delivering thrust and I quoted angle grinder experiment Wasn't after Frank whittle plans. Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Using model parts hence question. Unsure why you felt this answer was needed as contribution tho. Thanks anyway. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted July 10, 2017 Share Posted July 10, 2017 Posted by David Wainwright on 10/07/2017 13:10:42: Actually they are about 4 hp. Even the petrol ones aren't double figures. Original question did say I was after a basic device delivering thrust and I quoted angle grinder experiment Wasn't after Frank whittle plans. There's one here that is 10kw (14hp). 4 hp is hardly cutting it on a good aerotow tug BTW if you want to check power, thrust, rpm etc then there are some good programs on the net, Drive Calc and E-Calc are two that come to mind. Quote Link to comment Share on other sites More sharing options...
Jon H Posted July 10, 2017 Share Posted July 10, 2017 I think a few more details of the model are needed to make recommendations. a 90kg model is massive and the build would need to be done with LMA support. Large electric or large petrol engines are both options at this size/scale but the electric setup would need to be pretty serious. While i have no idea what level of experience you have exactly but you have told us you are new to the hobby and if so a project of this scale is really not recommended. Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Ok, thanks for replies so far. Just to clarify, this was never supposed to be a serious bit of kit designed to fly 90kg. For a start, the wing is what flies it. Am just after a motor to power the prop.As an incentive and seeing as they have just delivered two props by mistake, anyone who can come up with a viable option which falls within parameters, and they pay postage, they can have a free, 30x10" carbon prop as thanks. Remember, I'm not building a rocket. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 10, 2017 Share Posted July 10, 2017 David - read your PM's please. BEB Quote Link to comment Share on other sites More sharing options...
David Wainwright Posted July 10, 2017 Author Share Posted July 10, 2017 Must remember not to use hash tags as they make folk think of Donald. Understandably offensive.Edited By David Wainwright on 10/07/2017 14:20:07 Quote Link to comment Share on other sites More sharing options...
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