Simon Clark

Test flew my latest F3A plane today. Really please with it so far Simon

Just started working again here!

I haven't had this problem before but last night and this morning it is ridiculously slow - I have superfast Toob Broadband (900 Mb/s up and down!) and all other sites are fine except for sister sites such as Model-engineer.co.uk. Problem is with Chrome and Edge.

My suspect fuel was bought direct from Weston! As I said, many people think this fuel is the best thing since slice bread, so I was probably just unlucky. Simon

Many years ago, I used Weston Viper fuel. All went well on a few bottles until one bottle when suddenly none of my engines would run properly and I got the same effect with tight needle valves and sticking 'O' rings. In my case, it was even worse in that it attacked all the plumbing so I had to change all the silicone tubing in every part of every model and completely re-plumb my pit box. I then changed to Optifuel and have not had any problems since. I have no idea exactly what caused the problems but I can't see how it could have been anything other than the fuel. I know that many people swear by Weston fuels but I have also heard of some with problems. Personally, I steer well clear of them. Simon

I have a 2M F3A plane with petrol power. Originally it had an OS33GT with Krumscheid full pipe (aluminium) which was good. I then swapped the pipe for an ES composites carbon type which was even better and lighter. Both setups were generally quiet on the ground but there was some definite prop noise in the air. I then swapped the engine for a GP38 and this has phenomenal power. In all cases, the engines run very well on the pipes with good throttling, and compared to std silencers, better sound and much more power. Simon

You can on my T18SZ so I assume you can also on the T16SZ as the software is basically the same. I've never actually done it but you can set up a fine tune of differential with any trim, stick or lever as the input.

Yes you do now - this was introduced via a software update to my T18SZ a few years ago (can't remember exactly when). I don't know for certain if it is on all new Futabas but the T16iZ uses basically the same software as T18SZ so it is a reasonable bet to assume that is on this also (and probably on all new Futaba TX's)

Hello Nigel, I think that we will just have to agree to disagree on this subject! The manufacturer recommended charge method is to terminate charging with a negative delta peak voltage of 5-10mV. Your scenario has a pack charged to a point where this level is 20 times the maximum recommended amount! I have no data or experience of anything even vaguely close to this and so I have no idea what would happen and certainly would not dispute that if this was done then some sort of problems would likely arise. I would just summarise that there are some people who think that the simple two battery/two switch system is a bad idea and presumably do not use it for that reason and then there are others, like myself who think that it is a good idea and use it without issues. It is up to individuals to decide what they think and do. I have attached to this post a publication from Panasonic their 'Ni-mh handbook' that has a quite a lot of useful information, things to avoid as well as typical charge and discharge curves for various cell types. It certainly only covers a small amount of scenarios but some might find it useful. Simon id_ni-mh_1104_e.pdf

Hello Nigel, I apologise if I have misunderstood your points. Just for clarity, could you explain exactly what you think would/could happen up to the point where it has become stable and what problems you think that would cause. Thanks Simon

Thankyou Gary - some well made points. For those who may be thinking about using the double switch/battery setup advocated by myself (and some others) a concern has been raised about a phenomenon where if the two batteries are in very specific and different states of charge then one battery will discharge into the other and this will not stabilise. The reason that I think this will never happen is this: In order for current to pass from battery 1 into battery 2, then the voltage on battery 1 must be higher than that of battery 2. If you take the discharge curve of battery 1 and compare to the same charge curve for battery 2, there is no starting condition that has the voltage on battery 1 always higher than that of battery 2. In practice, if battery 2 starts from a point of mild overcharge with a slightly lower voltage than a fully charged battery 1 at peak voltage, then some current will initially flow from battery 1 to battery 2. The voltage of battery 1 (being discharged) will very rapidly fall to the same level as that of battery 2 which may see a very slight drop in voltage and so current flow will stop and the whole system will stabilise. It is easy to see this from the charge and discharge curves of any Nimh battery you care to choose. Of course, the proviso is that both battery packs are nominally the same type and capacity. Simon

It would appear that I am effectively being accused of promoting something that is 'fundamentally wrong'! I think that this deserves some kind of response: The method that I have been successfully using for many years now was not just the result of some random thought but was actually the result of some very careful consideration. I had considered the possibility of using diodes but wanted to make sure that these would be absolutely necessary. I was fully aware at the time that the general recommendation was not to connect Nimh cells in parallel but after further reading and analysis, it was (and still is) pretty clear that the issues relate to charging in parallel. It is very easy to see why this would be problematic and I would never consider doing this, let alone recommend it. Having allayed my concerns re this, I then got all the charge and discharge data together and started to calculate what would happen under different scenarios. These calculations were then verified by some actual (although relatively crude) testing and finally by many years on actual in field testing. Anyone may think this this is a bad solution and have other ideas but please do not state that this approach is 'fundamentally wrong'. Of course it is up to the individual to do whatever they want to, but the question was asked if this system worked OK and I have answered this to the best of my ability and, I think, from a position of some knowledge on this. Simon

Yes, a Nimh cell voltage when on charge will drop once full charge is reached but this is only a few millivolts (less on a Nimh cell compared to a NiCd) and will still be higher than a cell that is not on charge due mainly to the effect of internal resistances. If you take one pack that is at the absolute peak voltage and connect to a second that has just been slightly overcharged then some current will indeed flow from the first cell to the slightly overcharged one. However, by nature of the internal resistances of both packs, the voltage on the first pack will immediately fall and the voltage on the second pack will immediately rise and so the current will be reduced significantly. Even if this small current did cause the second battery pack open circuit voltage to fall a bit by nature of a small overcharge, the first battery voltage will also fall as a result of it becoming discharged and this effect will be much greater. So, yes, there may be a small amount of overcharging happening initially and you could consider this to be a temporary 'positive feedback' situation, there will be a very rapid roll-off and the first pack voltage will reduce to a point where no current flows and it is essentially self regulating ('negative feedback', if you prefer). I would argue that 'positive feedback' only occurs when the rate of change of the second battery pack voltage is greater than the rate of change of the first battery pack voltage and I don't believe that this will ever be the case (just look at the typical discharge curve of a Nimh cell). Diodes (Shottky types) are a good addition that will allow totally mismatched batteries to be used together but, in my opinion, not required if you have matched batteries packs. Simon

I disagree! I have been fitting two batteries with two switches for years now and there is absolutely no problem (providing that both batteries are nominally the same). Purely out of interest, I have tested using one fully charged battery and another half charged with no adverse effects, although I would definitely NOT do this in practice. I have also tested using a new battery in parallel with an old battery with a failed cell and definitely no problem here either. The vast majority of failure modes with batteries / switches are some kind of bad connection / high cell resistance. All of these failure modes are mitigated by parallel connection. Each to their own, but I have been doing this for years now on every model and have never had any problems at all. Before that, I lost one plane due to a bad switch (slide type before anyone asks) and since, I have seen a few planes crash due to bad switch / battery that I am certain would have been saved by using two switches / batteries! Simon

Hi Tim, If you would prefer a refund, then it is always best to make that clear and you may get one without any arguments or hassles. However, legally they are not obliged to do that. For anything older than 28 days and within the warranty period, the seller has the choice of either replacing, repairing or refunding regardless of what you might ask for. However if they send you a replacement or repaired item and that then subsequently fails, then they need to send you a full refund if you request one. Having said that, many retailers (especially larger ones) tend to try to ignore the law if it suits them. I had a problem with a laptop bought from a very well know retailer and after the first repair did not work, I asked for a refund which they did not want to supply. When I reminded their customer service that this was the law, the reply was 'Yes, I know that is the law and that legally you can a have a refund but that doesn't matter and we follow our own procedures' Eventually, I got my refund but only after four repair attempts! Good luck Simon