Stephen Belshaw
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Everything posted by Stephen Belshaw
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Difference between these two motors
Stephen Belshaw replied to Stephen Belshaw's topic in Motor Discussion
Thanks Frank, when I put the figures in for the Topmodel recommended motor/ESC/prop it comes out at a staggering 700W but e-calc saying everything is overloaded: This would give power to weight ratio of around 200W per pound! -
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I'm thinking of buying this 1.7M hotliner from TopmodelCZ Link Topmodel recommend this motor which is rated at 1130Kv max power 570W. However at €90 I think it's expensive! I have this 4-Max motor recently acquired from George, this is rated at 1105Kv and 450W max power and which was half the price of the above motor, obviously I would prefer to use what I already have. I asked Topmodel if the 4-Max would suit the airframe and they replied that "whilst it would work it the flight performance would not be very dynamic due to the low power". I'm slightly puzzled because on paper (at least to my untrained eyes) they look similar specs. However having run the 4-Max in a not dissimilar airframe I was underwhelmed with the performance, running on a 3S 2200 LiPo and a 9x6 prop I got around 300W on the watt meter. Running the figures for the Topmodel airframe and the 4-Max motor through e-calc the best I can achieve is 320W with a 12x8 prop and a 3s 3000mAh LiPo, Topmodel recommend a 13x8 prop but e-calc doesn't like that combination. Either way this is hugely below the theoretical maximum of 450W. What am I missing here?
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Am I getting to complicated?
Stephen Belshaw replied to SIMON CRAGG's topic in Electric Flight for Beginners
I'm glad I'm not the only one who struggles with the black art of motor/battery/prop matching! After trying to match a selection of props and batteries to various motors on various models I decided to buy a wattmeter and based my "calculations" loosely on the 100 watts per pound formula, give or take depending on the type of aircraft. A little knowledge can be a dangerous thing and I felt I wasn't getting the best results, so decided to "invest" in eCalc in order to save on stockpiling redundant props. I too then found a big discerpancy between my wattmeter and eCalc, the wattmeter always reading much higher. So I'm back to where I started - that it's a black art ................. -
Göppingen Gö-1 Wolf
Stephen Belshaw replied to Rene Wallage's topic in Gliders and Gliding - General Discussion
This is the Chris Williams plan I think? The magazine article had build article and pictures as I recall if you can acces this (digital subscriber), failing that an email to Chris would probably get you that info - I did that for one of his other designs and he kindly supplied a whole raft of photos and build instructions. -
Thanks all, some very good advice. I will look to swap the props, I'm using the 8 x 4's as they are all I have - as I'm predominantly a glider guider I don't have a stock of these things! Would there be any advantage in running the two motors in opposite rotation to each other, I understand it is often done on twins? Edited By Stephen Belshaw on 06/10/2019 05:45:59
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Connected a three cell 2200 LiPo, wow, what a difference! Now putting out 314 watts and pulling 28 amps with the 8 x 4 props (14 amps per motor so still within safety margins)? I'm guessing the TwinStar would fly quite nicely on half throttle, if so, what would be my approx. duration? Edited By Stephen Belshaw on 05/10/2019 19:43:25
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Ok, I can plug a 3S in, would the 8 x 4 props not be suitable?
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Oh, it must have gone AWOL during the edit??? 2S 7.4V 2200mah
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This doesn't seem like enough power to me, my set-up is as follows: 2 x HobbyKing FC 28-12 1534Kv brushless outrunners 2 x 30A HobbyKing ESC's 2 x 8 x 4 Aerostar composite props The ESC's are connected to a Y lead with the red wire cut on one of them, the battery feeds the ESC's in parallel. With a wattmeter connected I'm getting 106 watts at full throttle, drawing 16A. I'm assuming, given how the battery is wired, that this is the sum total of both motors? The AUW of the model, a TwinStar, is around 1300g in new money so a tad under 3lbs and I doubt this is anywhere near enough power. What am I doing wrong, how can I get more power?
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Reviving an old TwinStar
Stephen Belshaw replied to Stephen Belshaw's topic in General Electric Flight Chat
It's been a while but I've finally got round to doing this! All the components are now in the airframe and I just need to conect the ESC's, I'm intending to use this option. I have run the motors independently to check prop direction but I'm not sure how I program the ESC's (brake) - do I set them up seperately before I wire them together (Y-lead in to one throttle channel) or can they be programmed together as a single unit? -
Pat, yes - I intended to use this for smallish models that I can fly from a field across the road from me.
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Thanks chaps, I knew it was a bit of a straw clutching exercise and, as I indicated earlier, all the possible options for binding have been tried so it does look like a dud. So back to HobbyKing it goes ........... Edited By Stephen Belshaw on 20/09/2019 17:50:13
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I've had this new receiver on the shelf for a few months and just got around to using it. I have followed the FrSky instructions (such as they are) and on-line tutorials for binding this Rx which is pretty straightforward: Short signal pins on channels 1 & 2 Connect Rx to battery, red LED lights up Switch on Tx (X9D+), select D8 mode and select bind At this point the red light should flash to indicate that binding has taken place. Mine stays solid red so no bind achieved. I've been round the houses with this and have come to the conclusion that it must be faulty, unless I'm missing something??
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Thanks for all the help and advice chaps, I asked George at 4-Max and he recommended this motor along with a 9 x 5 prop. These are now inbound, along with a few other bits, so I should have the "Match" up and flying again shortly.
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Thanks again Simon, I wonder though if I need 300W - flying it with 250W seemed plenty fast enough and is giving me around 130 watts per pound so does that leave the door open for retaining the 2S set-up?? RC Plane Flyer, thank you for that suggestion I'll have a look at 4 Max and perhaps give George a call.
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Simon, thank you for your comments. Having already significantly reduced the weight of the model with the use of a LiPo and re-positioning the battery accordingly I doubt I have any adjustment left in that department so would have to make the difference up with lead. Not a problem as I am already well under the design weight. Running a 8" x 4.5" folding prop my watt meter gave a max reading of 250W, I queried the use of the Jeti ESC with the UK distributor and received this reply " the JES 350 Eco was designed to work with 6 to12 Ni-XX which is 7.2 to 14.4 volts so should be fine on a 2 or 3 cell Lipo". This is the airframe:
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I have been persevering with a marriage of old and new tech, namely a brushed "Graupner Speed" motor with a twenty year old "Jeti JES350 ECO" and new LiPo batteries. These were powering a Graupner Match airframe, twenty years old but newly built and with a AUW of a tad under 900 grammes (compared to the original design weight of 1.25Kg). It does run and flies very well (fast) but is obviously overpowered as twice it has snapped a prop in flight with fairly hairy consequences, although the airframe has survived! I'll have to throw the towel in with the old school stuff and, if possible, convert to brushless. So I'll need a direct replacement for the Speed 500 which will have the same dimensions (presumably an in-runner) and a suitable ESC if my Jeti cannot work with the new motor. This is the current motor/ESC combo: And this is the battery: Is a suitable motor available that will slot in to the airframe/existing mounting holes? Edited By Stephen Belshaw on 12/09/2019 15:58:27
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Funny you should say that Bob, after a frustrating few hours I discovered that there were no values entered in Curves! I had assumed copying and pasting was all I needed to do - obviously not and another Taranis lesson learnt. Because I only program for a new model infrequently, by the time I come to do it again I've forgotten my previously hard earnt lesson!
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I have a mix for operating spoilerons via the switch SF on my Taranis X9D which I have been using succesfully. I have copied this mix to another model via my computer and uploaded to the Tx only to find that it doesn't work, flip the switch and nothing! I cannot see any differnces in the programming and so am baffled as to what is preventing it operating. Here is a screenshot of the mix:
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