Nigel Heather

Posted by Biggles' Elder Brother - Moderator on 01/09/2018 21:24:14: The reality is Nigel that this is very complex stuff with a lot of interactions. To be honest most experienced electric power modellers can make an educated guess using theory at the sort of size prop they will need to extract the power they want from any particular set up - but its just that,...an educated guess. Theory can only take us so far here because in reality all the theories are approximations and simplifications of the true situation. So yes we tend to have good stocks of props for models of around the size and power we like to fly, just like we have good stocks of particular batteries. So for me, for example, I have a lot of models that use 6s, 5000mAh batts, set up to give in the range of 1kW to about 1.5kW and I have a selection of props that tend to work in that range with that battery. In the end the Watt meter decides - even there I have take into consideration that in the air the current pull will be less than in a static test on the ground. BEB I get all the complications but still puzzled. I see a plane I like, but not sure how much it weighs - the specifications include a weight but does not make it clear whether that includes battery, motor, ESC, servos and receiver. And when I look at motors the specifications are often limited. For example, the one I linked just gives the maximum current - which I assume is the absolute maximum current it can draw before it breaks/burns up. So how do I say, right I’ll have that plane, with that motor, that ESC and that prop. I get the fact that it is complicated, there are lots of factors and you need to experiement but I don’t think I will get far going into a store saying “I’ll take those three motors, that ESC, those two batteries and those five props. I’ll play with them at home to see which works the best and bring back what I don’t want”. An example, say I am looking at the Ripmax Esay Street 2. It says use the Ripmax Quantum II 25 and a 60A ESC. It gives a weight but not clear whether that is the all up weight. Now say I don’t want to use (or can’t get hold of) the Quantum II 25, how do I determine what alternatives I could use. Cheers, Nigel

Posted by Dave Hess on 01/09/2018 20:42:34: Posted by Nigel Heather on 01/09/2018 15:05:45: I get the electronics, but using the Quantum II 25 specs that I linked. Max Current = 50A Suggested ESC = 40A LiPo = 2S to 4S = 7.4v, 11.1v or 14.8v So I assume that max amps would be on 4S which would make the resistance = 3.37 ohms That would mean 4S = 740W 3S = 415W 2S = 184W Does that sound right? Cheers, Nigel Unfortunately, it's not nearly as simple as that because the speed that the motor maxes out at has a big affect on current and efficiency. The max speed is more or less controlled by the choice of propeller. A critical characteristic for all that is the motor's kV. You therefore have kV, battery voltage, propeller size/pitch and motor winding resistance all affecting the current significantly. Also, you have to bear in mind the efficiency because it's the difference between the power consumed and the power output that will burn the motor. In theory, if you had a motor with 100% efficiency, it wouldn't burn at any current, but it would break if you went too high. Basically efficiency accelerates downwards as the motor slows down, which is why you need to choose the right propeller to keep the speed up in the efficient zone. Increasing the voltage shifts the whole efficiency curve up along the RPM axis, which is why you need a smaller propeller for the same motor when you increase the voltage, so you can get the same current and efficiency at higher rpm, which means that you get more power because torque is proportional to current and power is torque times RPM. It's difficult to explain in words because of all the different variables working together at the same time. Did you look at the simulator I linked above. It takes some figuring out because the graphs are back to front from what we need to get a clear picture of what's happening, but if you move the cursor up and down, you can see the results changing in the table at the top right. that should help with your understanding if you spend some time studying what happens when you change things. Which gets back to my point. The advice is x watts per pound. But how do you know what motor/ESC/battery will do x watts per pound before you buy if you need to connect it all up and try a range of propellers. All the motor that I have quoted gives is that it can handle a maxium of 50A and can support 2S, 3S or 4S batteries. Cheers, Nigel

I get the electronics, but using the Quantum II 25 specs that I linked. Max Current = 50A Suggested ESC = 40A LiPo = 2S to 4S = 7.4v, 11.1v or 14.8v So I assume that max amps would be on 4S which would make the resistance = 3.37 ohms That would mean 4S = 740W 3S = 415W 2S = 184W Does that sound right? Cheers, Nigel

Many thanks for the info. I understand KV now. And I get the power per pound guidelines - they are vey useful. But it still seems over complicated because the manufacturers often don’t quote the specifications I need. For example if I look at a plane model, sometimes the weight isn’t specified at all, or when it is it is not clear wwhether that is all up including the battery or not, or even if it includes the motor, ESC, servos and receiver. And then when I look at motors manufacturers don’t quote the same specifications. Some will give the power (that’s easy), where some will say maximum current, but not clear whether that is the normal operating current to the safe overload, and some just specify the size of ESC required. Cheers, Nigel

Returning to the hobby after many years, and whilst I still find IC engines very familiar, electric motors are a little puzzling. In particular, how do I compare motors or look for alternatives. It is fairly clear cut with glow but not so much with electric. For example if I wanted to consider alternatives for the Quantum II 25 how would I go about that. **LINK** I thought it would be a matter of loking at the KV value but I am not convinced, because I can find other motors with the same KV but their other parameters such as power, amps, required ESC are very different. Cheers, Nigel

Hasn’t someone said though, that in difference to the Riot, the nose weights in the Ruckus are not removeable (short of attacking the foam with a scapel of course). Cheers, Nigel

Posted by Geoff Sleath on 29/08/2018 21:28:48: It may be better to get a bare airframe and fit it out with better parts than standard. Geoff Does that look possible? I read somewhere, maybe this thread, that the motor on the Riot was unusually thin, so much so it would be difficult to find a third party replacement that would fit. Cheers, Nigel

Posted by Capt Kremen on 24/08/2018 15:17:15: Oh well ... bit the 'plastic' bullet and just taken delivery of my 'Ruckus' ... first impressions ... Fuselage - a new/revised(?) moulding with elements of the 'Riot' incorporated. Much better access to LiPo & radio gear under a detachable canopy but no pilot in this nice office ... shame! Tailplane & Fin - same as 'Riot' BUT with cyno 'paper' hinges instead of plastic that the 'Riot' enjoys ... shame! Main Wing - same as 'Riot' with (slight) modifications. (You can see where the 'Riot' wing has been adapted) Equipment - Mmm ... s'pose OK. Servos and linkages can be waggled around indicating a combination of slop and imprecision. Cheap clevisis with comically thin silicone keepers! Spinner is now a SIG 1.75" item, a vast improvement on the original 'Riot' foam effort but still an unbalanced affair with a 'bendy' no name 12x6 prop. Undercarriage retained(?) with 4 tiny self tappers ... (thinks for how long will that last in everyday use???). Chinese metal 'bolt' axles too but wheels are a reasonable size. Motor - A very slim 850Kv unit. If changing, then minor surgery needed to fit a more conventional size unit withing the nose/cowl area. Next week's weather suggests a possible first test flight. Will take some WattMeter measurements and report back later. I guess you get what you pay for. I’m coming back to the hobby after about 10 years, flying a glow-powered sports plane (high wing stick). I feel compelled to move with the times and get something electric. I must admit I don’t like the look of foamies, much prefering the traditional balsa and film. So I did look at the acro wot GP/EP but a little put off by how expensive it ends up finished, which I could just about live with, but then how expensive the batteries that would be needed 5S 5000mAh - and I guess you would need at least three. Talking close to £500. Also the batteries seem an odd size so not sure they would be of use in any other models. So any suggestions of what else I should take a look at? Cheers, Nigel

The advert says that a 4s can be used for higher performance but suggests that the prop size is changed - presumably to keep the amps down. How did its flying compare with an acro wot foam-e Cheers, NigelEdited By Nigel Heather on 23/08/2018 11:56:14

Has anyone tried the new Max Thrust Ruckus distributed by Century UK yet? I'm interested to hear how it stacks up against the Acro Wot Foam-e. Cheers, Nigel

Hi, Coming back to the hobby after quite a few years away. When I left, electric power was a growing novelty barely capable of powering tiny foam piper cubs. So much has changed and I plan to transition over to electric. I like the AcroWot but am torn between the EP and the Foam-E. My thoughts Foam E Price, cheap batteries (3S), flies well, not sure how it would deal with wind and gusts, don't like the cheap polystyrene look EP Looks fantastic, bigger, should be able to deal with wind and gusts, but about £100 more expensive, dearer batteries (5S) Anyone tried the two and have a comparison that they would like to share.