Leo, Your opinion of my attitude is that it is fatalistic, while I have no problem with you having an opinion it actually is realistic. I do not know you personally and I am sure you are a fine gentleman the point I feel you are missing is that while you may be able to successfully rig up your setup, and whether you believe it our not anysetup can fail even yours many folks would simply doom themselves by doing what you may be able to do with success, That is my feeling on the matter as I believe as was said earlier in keeping things simple. I do use the JR Power safe double batt system as it makes sence to me, but I will never place another electrical device in my wiring in hopes that it will stop a servo from frying itself or the receiver. What happens if your solder diode becomes seperated, are you now placing your expensive model in the hands of multiple solder joints ? While I appreciate your opinion I will respectfully have to say no thanks. Kevin.

Kevin, I have strong opinions on those things that I care about. Most people I meet do. I don't mean to come right at you and sound like a jack. Yet I will keep pushing on this issue with anyone who engages in a dialog because the status-quo is not good enough and I think it takes a foundational change of opinion and attitude to improve this situation. Sometimes people need to get a little radical for the cause and a little out-there to get people off dead center resulting in change. The average modeler can do a lot more if they are motivated to do it. I'd like to keep pushing issues like this until the radio and servo manufacturers embrace it. That would certainly make it easier for the average modeler to rig a more reliable set-up. Today's standard set-ups are not good enough when even the best modelers in the world, who do extensive pre-flights, and are careful with there equipment, pile them in due to loss of control. We've all seen it. We all here about it. I think some of it is preventable.

I'd like my systems to get better and better. Certainly they are not immune to failure so I hope to be open to recommendations for improvement.

You ask what happens if a solder diode (I think you mean fuse) becomes separated? I lose control of that one surface. That's it. Relatively harmless relative to overall flight control. That is my whole point. The plane gets sluggish. You notice it and you land. What a wonderful thing. Sure beats crashing.

Leo

Well said Leo and we will just have to agree to disagree. I just hope you guys do not start getting guys coming on here asking why their solder job did'nt hold up and their otherwise fine plane crashed. I can only guess the response would be the same as we always get. Well ya must have not done it correctly. Take Care, Kevin.

Wasn't the original thread about a cheap servo that failed on a small .60 ARTF?
I'm all for keeping it simple and using quality stuff.
I accept that when things get big, 33%- 50% one needs a series of regulations issued from some governing body to introduce simple safety precausions... but...
On a small hobby plane... fiddle as little as possible... because there's a 99.999% chance that any future failure will be a direct result of that fiddling!

Oh come on now, you are comparing apples to oranges. Houses don't fly, and neither do most cars. Furthermore, both are designed to allow humans to be inside of them. That statement is so irrevelent that I will address it no further.

On the subject of crashes 'caused by radio/ servo failure by experts': apparently you have witnessed far more than I have. I, like another suggested, have witnessed crashes which were blamed on 'interferenece/ component failure', but in most cases: I have my doubts.

Case in point: I witnessed a giant scale FW-190 crash at the 2008 Mint Julep event. I later heard the pilot blamed interferrence. My opinion tho was different: the pilot was completing a figure 8 during exteme crosswinds and was nearing (or over) the pits/ flightline. I saw the plane banked nearly 90 deg, attempting to complete the turn and get it back over the runway, when it suddenly spun in. My impression: hi speed stall/ excessive angle of attack. IF the aircraft had any reduntant sytems, I'm thinking they would have made the aircraft heavier, and thus more difficult to turn.

Just my opinion, but I did not see any crashes that weekend that could be attributed to radio and/ or servo problems. And until now, I have never heard of a shorted servo, or it's wiring. But then again: I have no experience with giant scale aircraft, so maybe the components of such large aircraft are more prone to such things? Both of my servo failures resulted in servos that would not move. They did not cause an excessive current draw, and all other servos and Rx remained fully functional.

One more thing: I DID have one of my Hangar 9 Hellcat 'shot down' be someone turning on a Tx at a very large event which had no impound and poor frequency control. I KNOW it was another TX being turned on becuase the mechanical landing gear ( 1 servo per 'leg' ) suddenly started to come down just as the aircraft abruptly rolled left and into the ground.
Of other possible causes:
1) battery failure of any type, including shorted servo: the landing gear would have remained in the up position.
2) pilot error and/ or windshear/ exteme weather: the landing gear would have remained in the up position.
3) retract switch was inadvertantly switched while simultaneuosly left thumb developed severe cramp, causing it to contract toward my hand: retracts switch is located away from active hand and thumbs, must make very deliberate effort to switch it.

I don't think having system redundency would have helped, UNLESS I had another pilot controlling another TX, but even then..................I'm not sure it would have helped.

I have since converted all of my expensive ($200 ~ $1500) aircraft to 2.4 GHz systems (with dual/ reduntant Rx antenna)

Leo,

According to information that I've read elsewhere, such as Red Schoefield's Battery Clinic and some testing results that were posted somewhere here on RCU, it's not a problem to use two packs without diodes. According to the testing that was done, a failure in one of the packs caused only a very slow drain on the second pack. My recollection may not be correct, but I thought that after an hour, the remaining "good" pack was only drained by 10% or so. The conclusion of the testers was that with regular checks of battery voltage, e.g., between flights, or every other flight, that the risk of a failed pack draining the other pack and bringing down a plane was extremely low. I generally use two 6v receiver packs into two ports on a receiver on all my planes and am interested if you have more information on this approach. I would like to better understand the scenario you are thinking about.

Thanks,

-Ed B.

As you may have noticed that the discussion at hand is dealing with extreme and rare cases. The people involved are all very experienced RCers who take all the normal precautions. All these diodes and fuses etc are for those 1% problems that arise and not for the standard run of the mill problems we normally encounter. When very expensive aircraft are involved, I think Leo is trying to cover as many bases as he can. I fly single Nicad system myself and replace the batteries every couple of years. I have never had a problem, but I'm a big KISS person so in my book less is more. I also don't fly multi thousand dollar airplanes either.

My apologies to the original thread starter who was talking about a cheap servo. The thread morphed. It is my fault. Not to worry; I'll get tired soon and go back to building.

Ed,

Excellent information. I would agree depending on the type of cells you use and the level of charge you have left in the batteries before you take-off. 10% would be a good rule of thumb for a Nicad on the first flight of the day but it will go up considerably with each flight. It is more of a concern on the 4th or 5th flight.

Here are some quick tests that show 10% of a fully charged packs capacity would be a good ballpark for NICAD & NIMH cells. Not for Li-Ion cells with lower impedance like A123. Let's look at some quick test data for cells I have in the shop. I just did a 2 cell to 1 cell charge on sub-C size NICADS, AA size NIMH, and A123 cells. They read 154 mah, 162 mah, and greater than 10 Amp respectively. It blew-out my meter. You can see the pictures. I knew the A123 would be something outrageous because they have very low impedance. My meter was fuse protected to 10A. (Huh? Figure that. Fuse protection.) I saw an initial reading of 6A then it blew. So it is something greater than 10A and I have nothing to check any higher.

10 years ago I used to fly with single 1200 mah Nicad packs. I would use about 250 mah per 15 min. flight and I would fly 4 times on a plane in a day. In hind-site not very smart because I only had 200 mah left at the end of the day. The battery would test good and still be on the plateau before the last flight but I really didn't have much reserve energy in the cells. A weak pack or a stalled servo and it would have crashed. It's amazing that I got away with that.

About 6 years ago I thought I was smart and I converted to dual 700 mah Nicad packs plugged directly into the RX (1400 mah total). No diode isolation. Took my total mah up slightly. In hind-site not too smart because on the 4th flight of the day I would test the battery voltage and everything would look good and in theory I was leaving the ground with 650 mah left in the combined packs. But here is the problem. If I dropped a cell after takeoff (which I have seen happen, and you will too if you fly enough) then I would unknowingly be down to a theoretical 325 mah left in the remaining pack for a flight that will consume 250 mah. Add to that the drain of the low pack would consume another 40 mah and it would be all over. I amazingly got away with that for another 3 years on roughly 3 airplanes.

About 3 years ago I boosted everything up to over 4500 mah total capacity. I have more than enough reserve capacity for just about anything. Some of the planes are equipped with dual A123 cells which must have diode isolation if you use them on one common RX. At a greater than 10A charge rate a lost cell will cook the buss on the RX they are connected to. However, with the dual RX, I don't need that diode isolation but I still use it to drop the voltage 6.6V down a bit.

Leo

So your running a singe battery pack per receiver and not using something like a smart fly battery isolater ($30) which has dual outputs so if you lost one of your batteries, you would lose half of your system?

Sorry if I caused any problems here, I was just posting about a failed servo. I have had bad luck with cirrus, and will not use again. And I know and except anything can fail and will eventually.
The pony flies again with a new servo for now.




Rule of thumb.
Kiss every plane goodbye before you fly them, because you do not know if there coming back.

Poorwboy, Sorry for such a departure from your Cirrus servo problem. I hope you can see how it happens. I'd jump off an start a new thread, but all the action is right here so what am I to do?

P-40 Driver, Yes I am running a single battery into each RX right now. Yes I will lose half my system and have to land the plane with limited control. Throttle control remains with the servo on one RX and the engine cut-off on the other. Complete separation of each system was more important to me than dual battery on each RX. I am open to the options here and have looked at the SmartFly product. I had a long talk with Don of Don's Hobby Shop in Salina KS regarding this product. He said he could make a lot of money selling them along with all the PowerPanels on the market but he won't because they routinely fail. I was not encouraged. Don does endorse the use of MatchBoxes for multi-servo high power applications, and I can understand this because each matchbox only deals with a single control function. It does not effect your overall power supply to the RX. My friend Pierre, who is an electronics expert as a profession, is after me to run the two RX off a common battery bus with diode isolation. I may do this. What has stopped me from the bus idea is that I want to know what protects this combined battery system from a high amp draw down either RX path? I am open on this and would like to hear your recommendations. Leo

No harm taken.[sm=thumbup.gif]

I will have think about that one for while and see trade offs make sense to me. I really wish I could build one of those Wildcats you make the fuselages for, but finances and time are not there at right now.

Sorry POORWBOY for hijacking your thread like this, I think we got a little carried away.

P-40 Driver,

Sorry on the Wildcat. I retired the mold starting in 2009 and no longer make it anymore. I will continue to make the cowls and canopies to support Jerry Bates plans, but after about 4 years and 35 fuselages the mold was shot plus Robart quit making the gear so it didn't pay to make a new mold. I think the days of the Wildcat are over unless Sierra Giant Scale was to create new gear for it. I am always amazed that we don't see more Wildcats flying. In the last 10 years I have made over 90 Cowl & Canopy sets and 35 fuselages. In all that time I could only count 6 Wildcats that are flying. They must all still be on the bench or just kit collectors. Leo

Leo....Mine (Wildcat) is in primer.

Jeff