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Member postings for Tim Kearsley

Here is a list of all the postings Tim Kearsley has made in our forums. Click on a thread name to jump to the thread.

Thread: V tail question
01/08/2020 14:46:10

I don't think I explained myself very well, looking back at what I wrote Ron! As far as I can tell, the Excalibur maintains a straight line in the dive. It's when I apply elevator to pull out that it turns to the right. This is why I originally thought that there was some rudder input occurring through the two elevator halves not moving equally. But I can't see anything noticeably unequal in their movement back on the ground.

At the end of the day, I can live with it by applying corrective input, but I like things to be right!

Tim.

01/08/2020 09:20:45

Well thanks to everyone who's contributed to this. Next time I fly the Excalibur I'm going to pay much closer attention to exactly what happens to try and get to the bottom of this. As I fly mode 2, it's quite possible that I'm slightly pulling the stick across as I pull down. However, I don't notice that effect in other models I fly, nor did I see it in the two previous Excalibur models I've owned.

Martin, it isn't a particularly vigorous manoeuvre I fly. I climb to height, roll inverted and then power off and put the model into a vertical dive, slowly pulling out as terra firma approaches! What is very noticeable is that, without intervention, by the time the model is in level flight it is now flying some 45 degrees to the original line, to the right.

Tim.

31/07/2020 08:59:41

OK chaps, thanks for the opinions. I hadn't considered a warp in a wing. This is the third Excalibur I've had and I didn't see this pulling to the right characteristic in the previous two versions. Perhaps I was just lucky!

Tim.

30/07/2020 18:50:59

Good point Peter, thank you. Any way to prove or disprove it? One other thing to add - I don't loop the model very often, but now I come to think about it, I think it similarly pulls right entering a loop. I wonder if I'm unconsciously pulling the stick slightly to the right as well as down and putting in some aileron input? I hope so, because I can easily cure that!

Tim.

30/07/2020 18:22:29

A question for those with a better grasp of aerodynamics than me (almost everyone!):

I have a Durafly Excalibur, which is a foamie "warmliner" with a V tail. It flies beautifully and is trimmed to fly straight and level at around half-throttle. I like to fly a manoeuvre which includes a vertical dive (unpowered) from a good height. When I pull out of the dive to level flight I notice quite a pronounced pull to the right. My question is, is this likely to be due to the two halves of the V tail not "tracking" properly as up elevator is applied to pull out of the dive? I must say that by simply looking at the elevator deflection both sides of the V tail seem to move equally, but that may not be meaningful, as the total deflection is fairly small. My theory is that a small rudder effect is being introduced with the elevator movement. Is that feasible?

Thanks,

Tim.

Thread: Avios 1450mm Spitfire MkV
26/07/2020 12:40:49

I've just purchased this model, as it looks nicely done from the photos and videos I've seen. I have to say that I'm not a fan of foam models generally and not really a fan of this one now that I've assembled it!

Some of the problems:

A peculiar, warped fin. Its hard to describe but it seems the left hand side (looked at from the rear) is convex and the right hand side is concave. It's almost as if the fin has an asymmetric aerofoil profile.

None of the control surfaces centre properly, i.e. they don't return to the same neutral point when deflected in each direction. The rudder is particularly poor.

Paint adhesion is poor. I put a piece of low-tack masking tape very lightly on the wing when measuring the CG - it removed a piece of paint when pulled (very carefully) off.

Fairly poor instructions. For example, no mention is made of connecting up the LEDs at all.

I'm a bit apprehensive about the maiden flight, given the first two problems. Anyone else noticed similar issues?

Tim.

Sorry for the double post - router issues here!

Edited By Tim Kearsley on 26/07/2020 12:41:40

26/07/2020 12:38:54

I've just purchased this model, as it looks nicely done from the photos and videos I've seen. I have to say that I'm not a fan of foam models generally and not really a fan of this one now that I've assembled it!

Some of the problems:

A peculiar, warped fin. Its hard to describe but it seems the left hand side (looked at from the rear) is convex and the right hand side is concave. It's almost as if the fin has an asymmetric aerofoil profile.

None of the control surfaces centre properly, i.e. they don't return to the same neutral point when deflected in each direction. The rudder is particularly poor.

Paint adhesion is poor. I put a piece of low-tack masking tape very lightly on the wing when measuring the CG - it removed a piece of paint when pulled (very carefully) off.

Fairly poor instructions. For example, no mention is made of connecting up the LEDs at all.

I'm a bit apprehensive about the maiden flight, given the first two problems. Anyone else noticed similar issues?

Tim.

Thread: Telemetry problem
23/07/2020 15:20:00

Just a thought Barry, how often does the Taranis log the telemetry data, e.g. every second, every two seconds? I just wonder if a burst of throttle is causing the Voltage to momentarily sag between logging writes. Unlikely I would have thought but, as I say, worth a mention.

Tim.

Having now re-read your original post, I see you mention flying at constant throttle.  Forget I spoke!!

Tim.

 

Edited By Tim Kearsley on 23/07/2020 15:21:16

Thread: Help! Can't charge my Lipo
13/07/2020 12:42:19
Posted by Richard Clark 2 on 13/07/2020 00:50:12:
Posted by Keith Miles 2 on 11/07/2020 21:21:42:
Posted by Mike Blandford on 11/07/2020 16:06:00:

You haven't mentioned what radio gear you are using. Many modern radios include telemetry back from the model. With suitable sensors you can get the flight pack voltage and the motor current displayed (and even spoken). This may well avoid the need for a wattmeter. I have one, but haven't used it for a long time as I use the telemetry.

Recently I've started using FrSky Neuron speed controllers with FrSky radio gear. The Neuron has built in sensors and sends voltage, current, RPM, capacity used and temperature back.

Mike

Telemetry is all well and good if you are prepared to buy and fit the necessary sensors or the type of ESC you describe to each and every model and it can be fully justified as opposed to it being just a fancy and unnecessary additional gizmo.

Each to their own, but I also prefer not to have too many potential distractions when I’m flying! I prefer to pay attention to what I and the model are doing rather than be tempted to pay undue amounts of attention to the transmitter.

Also, for some, a wattmeter, being a universal device, is simpler, perfectly adequate and probably more cost effective especially if you only fly models that are already set up or fitted with the recommended components which should not need in-flight monitoring.

Beginners are also better off with simplicity than complexity, in my view.

I'm far from a beginner but I don't bother with telemetry at all and don't intend to, even though my chosen make of radio (Multiplex) was the first 2.4 radio to have it and it was inbuilt from day one..

It's just gizmology.

I've been flying RC since the 1960s and have never had a radio caused crash. Or "You are using 60 amps and the RPM is 9 thousand." So what?

PS: Why do they have rev counters on automatic cars?

Some telemetry is more useful than others. It certainly isn't "gizmology". If you're flying electric powered models then a knowledge of how much battery capacity you've consumed is a far better guide to when you should be thinking about landing than a simple timer. As Mike said, if you're a FrSky user, the Neuron ESCs have much telemetry built in, so no need for extra sensors and cabling. And they're not expensive. Also, as a glider pilot I fit all my sailplanes with telemetry to tell me altitude and vertical speed (i.e. vario). None of this stuff needs to take your attention from the model as it's child's play to program a switch to announce it.

Tim.

Thread: LiPo over-voltage
09/07/2020 10:31:17

If you are referring to the charger I used when I saw the high cell Voltage, it is a Graupner Ultra Duo Plus 60, which was not a cheap charger when I bought it (somewhere around £280) and I don't think is "poorly designed".

As for charging at 12C, well I wouldn't do it even if the manufacturer said it was possible. I'm never in a hurry as I prepare batteries the night before a flying session, so I charge at 1C.

Tim.

09/07/2020 08:54:59
Posted by Andy48 on 08/07/2020 22:16:10:
Posted by Allan Bennett on 08/07/2020 20:37:39:

There's obviously many different makes/types of chargers being considered here. Mine displays individual cell voltages throughout the charge, and I've never seen any cell go above 4.20v -- if it did, the charger would have stopped and given an 'over voltage' error message. If a pack is out of balance it holds the first cell to reach 4.20v while the other cells catch up. Like Chris, I don't understand how any charger can display a cell voltage over 4.20v and not figure out that something's wrong.

Simple, because at the time it does not realise the cell voltage is over 4.2v due to a poor connection.

But this doesn't make logical sense. If the charger is displaying a Voltage of, say, 4.35V then it "knows" that the offending cell is over-Voltage - how else can it be displaying it? I can understand the similar scenario where some high resistance connection results in the charger "seeing" a falsely low Voltage, but then it would display that false reading wouldn't it?

Tim.

08/07/2020 20:40:10
Posted by Richard Clark 2 on 08/07/2020 20:06:34:
Posted by Nigel R on 08/07/2020 11:54:39:
Posted by David Hall 9 on 08/07/2020 11:23:12:

As will the charging current for all the cells (though it won't be the same for each) as they are connected in series.

Really? That's the first time I've heard of items in series having different currents through them. Physically impossible I believe.

Tim.

08/07/2020 19:50:29
Posted by Richard Clark 2 on 08/07/2020 18:56:07:
Posted by Tim Kearsley on 08/07/2020 13:21:17:
Posted by Richard Clark 2 on 06/07/2020 21:10:54:

Actually I agree. It wasn't a good example. It also gets extremely hot if you charge and use it at the same time which Chord say is fine to do.

A question:

Do you own a Mojo or did you search specifically to cast doubt on my overall 'argument' without yourself trying non-balanced charging over a long period as I have done?

No, I don't own a Mojo. I'm open-minded about the pros and cons of balance-charging every charge, but on balance (no pun intended) I shall continue to balance every time. My search was to see what came up in respect of Mojo and the battery it used, and it soon became evident that there was a body of complaint about the short battery life. As you say, it wasn't a good example.

Tim.

08/07/2020 18:42:25

In reply to the final point you make Chris, the charger has been in regular use (usually at least weekly, sometimes much more, for the last 10 years or so) and has NEVER overcharged before. As to how I measure the cell Voltages, I normally use a fairly simple LiPo checker which shows the Voltage on each cell. When I saw the anomalous Voltage I further checked with a digital multimeter, which confirmed the value to within 0.01V. The charger has since been used to balance charge without incident. I did take the precaution of re-seating the balance boards where they plug into the charger, in case a poor or intermittently poor connection was the culprit.

Tim.

08/07/2020 13:21:17
Posted by Richard Clark 2 on 06/07/2020 21:10:54:

(I recently replaced the 2 cell 1600 lipo inside a British made £400 Chord Mojo portable digital to analog 'hi-fi' converter. It's intended to be charged from near enough any USB charger (I mostly use the Apple iPhone charger) and it's not got any facility for balancing at all, so Chord, which is a very reputable company, think it's safe enough.)

Having just read through some forums and seeing the number of people complaining about the short life of the LiPo in their Chord Mojo I don't think Chord, who might well be "reputable", are a good example of how to charge a LiPo battery!

Tim.

08/07/2020 11:41:17

I should add, out of interest, that when I tried to use the same Graupner charger to either balance or discharge the pack it refused because of the high cell Voltage! The only way I could proceed was to partially discharge it by connecting ONLY the main power leads (no balance lead connection) and then balance and finally charge as normal.

Tim.

P.S. - The pack, by the way, is a Turnigy Graphene 4S, 1800 mAh 65C.

08/07/2020 11:28:08
Posted by Phil Green on 08/07/2020 11:23:13:
Posted by Tim Kearsley on 08/07/2020 11:12:02:

... a cell ended up at 4.34V. The charger (a Graupner Ultra Duo Plus 60)

Thats the LiHv terminal voltage. Is it possible the charger have been set wrongly?

No, Phil, I can 100% guarantee that the charger was set correctly. I use a set of preset values of battery chemistry, no. of cells and capacity (mAh) stored in the charger's memories. Additionally, I do always check that the values are correct before I hit the button to start charging.

Tim.

08/07/2020 11:12:02

Whoa, I didn't intend to start any arguments!

I don't dispute the necessity to keep the cells in a LiPo pack balanced, and indeed, as I said, that's what I always do. But can you not see the danger that Andy pointed out a couple of weeks ago, and which I encountered? If you have a poor connection somewhere in the chain of connections between the charger balancing circuit and the connections to the LiPo battery, resulting in the balancing circuit seeing a falsely low Voltage on a cell, then it will potentially overcharge that cell. It's the only explanation I have for my own circumstance, where a cell ended up at 4.34V. The charger (a Graupner Ultra Duo Plus 60) has performed faultlessly since.

For what it's worth, my own view is that I will continue to balance charge every time, but having seen with my own eyes that overcharging can happen I will be even more cautious!

Tim.

 

Edited By Tim Kearsley on 08/07/2020 11:17:13

07/07/2020 18:10:32
Posted by Richard Wills 2 on 07/07/2020 17:14:09:

Can you measure the cell internal resistance with your charger? If they are all similar I would be inclined to think the pack is OK to continue using

Unfortunately I only get a measure of the total pack IR, not individual cells. The pack IR is very similar to two other packs which are of the same capacity, cell count and manufacturer, and which have had similar use, as I always use the three packs in the same session.

Tim.

07/07/2020 16:46:41

I just read your post from a while ago Andy. Yes, indeed it does seem to be a potential hazard in balance-charging. I've always, in my ignorance, balance-charged, every single time, because I didn't see any disadvantage. But this puts a new perspective on it.

In my own case, I partially discharged the over-charged battery and then balanced it and finally re-charged. I have to say that it seems absolutely fine and in fact powered a model for a decent flight this morning. I checked the cell Voltages after the flight and all were within 0.01V of each other.

Tim.

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