Mitchell Howard

Matt do you think I should run a smaller prop still? It's recommended above to use ecalc, but I'm an engineer by training and I learnt a long time ago not to trust theoretical values too much. There's no harm in adding to the arsenal of props anyway!

Hi Matt - the current hardware I'm using is only what was recommended by the model shop. I'm still green, but I was even greener at the point I bought everything! I've got an 11x8 and 12x6 prop in the post which hopefully will be much lower in peak values.

I don't know if this is a known problem, but I'm getting the below image appear upside down. It doesn't matter if I've turned it around myself in windows and then upload an upside down one myself, it still appears upside down.

I got rid of the spinner yesterday evening and the vibration did disappear. I've managed to adjust well enough for now to leave it in place, but will get it changed out for a better one. I charged a LiPo and ran it up again for it to show 67A and 1001W... vid-20210603-210353_TwuPrHdz_qbyu.mp4

Tell me about it! Got some building to do and wary of getting ahead of myself!

I don't have a reference point to be honest, but the ZTW 60A is hot and the Zeee LiPo barely warm! I use the EC5 connectors, and I think Amazon UK have stopped selling the 3700s. I think Zeee have stopped making them too, they're not on the website. Shame, I'll have to try something else or re-plug another Zeee pack!

Now I know the actual amp draw I should think this will be a good comparison to ecalc. I wonder if it assumes in-air amps or on-ground amps.

I am, I get a good 6-7mins. Another 2-3mins would be great. I'm less concerned about in-air performance, i.e. not fussed about making it climb vertically or all-out horizontal speed, but am fussed about having what I can most closely relate to as 'torque' in a car - the ability to get off the ground with ease and climb steeply, perhaps 45-60deg without any fear of stalling. It certainly has that characteristic at present. It doesn't sound like the model is ?overpropped?, what with this concept of in-air amps being lower than on-ground amps.

Do you have a feel for how much amp draw might drop by Simon? are we talking 10%? Less? I think I'll hold off on adjusting prop and just get the spinner and ventilation sorted. Heat must be wasting mAh too. My Radiolink AT10ii has a voltage sender module attached to the receiver which I'm about to start using, but nothing for amps. I'm quite happy with this ground pulls more amps theory, so will be interested to see spinner-less current draw later this evening!

Got two days in row at the field after passing A test the week before. First time I've been able to get through 4 LiPos, half an hour of solid flying each day without needing to ask someone to supervise!

I'm glad you've said that, I'd got it around the wrong way. More pitch = more speed More diameter = more thrust. It's a Seagull Boomerang v2 Is there a way to get a good reading without taking the wattmeter up in the air? Lift it off the deck I suppose? Two man job. Do you think it's a good balance then Frank, no change? What's the feeling on fully plastic spinners? I do want to resolve the vibration.

I've just used a wattmeter for the first time on my trainer setup; APCE12x8 prop, Ripmax Quantum ii .40 motor, ZTW Beatles 60A ESC, Zeee 4S 60C 3700mAh. The numbers it pulled seem close to the knuckle; peak power and amps at 790W, 57.9A. I think there's a few things to do to address it, but this forum always comes up with solid suggestions, so please review my approach! 1) Reduce prop diameter and/or pitch. Not sure by how much to move away from 12x8. I'm thinking I'll get and test a 12x6 and 12x7. I'm don't think I'm pushing the envelope of thrust or speed with current setup (possibly why it hasn't died!). 4-max has the model at 50A with APCE12x6 and an 800KV 3547 motor. Difficult to read across and compare, everything's different to mine. I've not yet figured out the best way to weigh models, so I'll assume it's the advertised 2.5kg/5.5lbs. Output power as measured puts it at 143W/lb which I understand as being 'fairly meaty'. Surprised the Ripmax Quantum .40 box says use a 12x9 and 60A ESC. I can't find a max current for the motor but a very similar Overlander Thumper 4250 says 63A maximum, so the Quantum must be struggling too. How far beneath 60A should I be aiming for? 2) Ventilation improvement I'm definitely going to get some ventilation into the airframe. A clubmate had a square pocket about 60x60mm in the base of one of his models to let air out heated by the motor, ESC and LiPo. The ESC has been getting hotter that I recall it ever getting, but my confidence has been growing and I've been getting more liberal with the throttle. 3) Vibration and prop spinner I feel like the nose of the plastic prop spinner is running slightly eccentric and above 50-60% throttle I think it's responsible for vibration. I'm going to take it off and run it without to see if the current and vibration reduce. If it does drop, I don't think the plastic nose is going to lend itself to being pushed and pulled into a centre position. Is this what aluminium backplate spinners are better at? I think the self-tapping threads in the plastic backplate are likely responsible for pulling the cone off centre. I've just seen on 4-max, a recommendation to lose the stock 'IC' spinner and to use an electric one that has an alumnium backplate. What's the difference? The site just says runs truer - that must be a benefit for IC also?

Evolution Models with the Fusion series of fun fly models. Their site appears to have been hacked in the last 48hrs as it's churning out spam ads.

FYI, that's just a link to bbc.co.uk.

Thought you'd be interested to know what I've found on my first wattmeter run. I haven't weighed the trainer yet. vid-20210602-192306_SAf7yOqL_eC9r.mp4

It's not a large model, it's a Wot4, but having been gifted the servos I'd like to use them. They're better quality items than I was planning to buy. I'm thinking about a 6V output from a ZTW 6A UBEC will do the job. I'm happy with the technical principle that a motor will only pull the current it needs to. I don't have any idea what kg loading the control surfaces will need in the worst case. The servos are 9-10kg stall at 6V, so judging by the hitec spec, if they're all stressed at once (2* aileron, 1* rudder, 1* elevator) then we're looking at 10.4A. The engineer in me is saying, "make sure you've got enough current for that condition"!

Hi Philip, thanks for the note about 5.5V. I want to plough ahead with using the UBEC solution if only to learn something new. I've had a replay from Radiolink already - they've said; "The R12DS receiver does not return overload. You can use it with confidence. The positive pins of each channel of the receiver are connected in parallel, and the negative pins are also connected in parallel. You need to be careful not to mix high-voltage servo and ordinary servo, otherwise it may cause damage to the normal steering gear due to overload." I take this to meant the white or yellow signal wire is low voltage, low current and doesn't factor into the load calculation. Mixing HV and standard servos means you could overvolt the standard with a supply for HV. I'm not doing that, all servos are the HV type. They're saying each servo is connected in parallel to common + and - rails. That means that while you're not pulling voltage/current through each servo in turn, you're still putting an increased load upstream of the common connection point, and the rail itself has to cope with that. Presumably the physical rail is just a printed track on a PCB. If each of the servos pulls 3A at the same time, the question I think I should be asking Radiolink is, "can the rails cope with 12A@6V". Frank - if they're each rated to 6A and Radiolink have factored that in to the design of the rails, then presumably a 12ch receiver can handle 72A... which doesn't seem likely, so there must be a lower value.

Hi Frank - models in the subject of the thread. That's good to know, paralleling two smaller connectors to increase the max current to the receiver.

Hi all - building a new model and have been gifted some JX servos from a clubmate. They certainly seem to be of a decent spec, but they're high voltage. Normally I would have used the ESC BEC at 5.5V, 5A to run the receiver and servos, but the voltage is too low for these servos being rated for 6-7.4V. Another clubmate recommended a UBEC, something like ZTW's 6A version for £15. I think this is the right idea. Only problem I'm having is that I can't find any information on what amperage the servos will pull nor the receiver's max current per channel. Can anyone help? Is there a standard current the receivers are built for? Can servo current be estimated?

If I'm understanding correctly (and I think I'm piecing the puzzle together now), the following statements should be true; For a given LiPo, ESC, Motor, airframe, the prop at say 11x9, 12x8, 13x7, 14x6 etc would yield the same motor power output (as read by a watt meter) but would be respectively lower speed higher thrust, thru higher speed lower thrust depending on where you set your diameter-to-pitch balance. To increase power draw (i.e. to make use of spare pack capacity), for a given LiPo, ESC, Motor, airframe; the prop at 11x10, 12x9, 13x8, 14x6 would use more amps than above but would only give more thrust. because the pitch is increased without reduction in diameter. the prop at 12x9, 13x8, 14x7, 15x6 would use more amps than above but would give more speed. because the diameter is increased without reduction in pitch. Is there any evidence to suggest that 1" off the diameter and added to pitch yields the same power draw? Or is it less convenient than that, i.e. 1.5" etc. there must be a ratio.

My watt meter arrived yesterday, much tinkering to be done!

I've had a Ripmax Quantum 40 on a trainer with a 12x8 prop. There's no minimum prop recommendation I can see for this, only Ripmax suggesting 12x9W (W?) is equivalent to a .40 2-stroke. Having found the stock issues with Ripmax aren't ending anytime soon, I'm aware of the Overlander Thumper motors, and they have a motor almost identical but with a 13x10 minimum prop size. @Steve - Judging by the numbers, there's going to be more thrust and speed on a 13x10 vs a 12x8. Will have to get on eCalc. What will happen if I fit the smaller prop? There's still a load there on a 12x8, so it won't be running free (high current).

How does the load that a prop puts on an electric motor differ from the load the same prop puts on a glow engine? Does a 12x8 on electric not require the same amount of energy to drive on a glow engine? Is there an offset rule one must apply?

Hi Frank it's a Radiolink AT10ii. Draw is rated at 100mA but I guess that would be at 7.4V as it's the only number reported. It has a customisable voltage setting rather than a chemistry selection setting, so you can set where it cuts off if you want telling earlier or later than nominal. I know the Tx gives me the opportunity to calibrate the pack voltage relative to what the Tx reads by default, but I need to check how linear that is. Looking at it again, a 3S LiFe would also do the trick. I'd have to satisfy myself the Tx keeps pace with the reading of a separate multimeter reading to the tune of 0.6V seeing how one cell can drop 0.2V over 80% of its useful charged life.