The genesis of many (most? all?) of askJOHN articles are user's questions.
This remains true tangentially of Regarding ignition and radio switches because it's a continuation of a free wheeling question and answer discussion regarding model aircraft equipment installation/placement on one of my favorite modeling forums, RCSB.
Note; if you're unfamiliar with RCSBit, and if you love models closely resembling full scale aircraft, then I urge you to join. This, because it's where others suffering a similar affliction conjoin to share and learn. You'll fit right in, trust me.
Further to this; clicking the above RCSF-link will open a new tab in your browser (this, so you don't loose your place, here). Anyway, believe me, you owe it to yourself to join up if like me, scale models are a great love amongst the many genres of modeling.
So where was I? Oh yeah, we were at RCBS . . . sop there we were, specifically within a thread about a gorgeous giant scale model of a civilian parasol powered by a radial engine, and whilst making my point, the OP called foul.
Here's what happened; the gifted modeler in question (the OP or original poster) had installed within the model's fuselage a lovely twin cylinder gasoline-ignition engine. Like a proud papa showing off photos of his grandchild, he'd shared detail photos of his progress with the model. These, to include the engine and equipment installation. I'll swipe this one to give you a taste of the content.
And along the way, unaware of what was coming, he'd innocently fielded a comment and left an question. I stepped in, mayhem resulted and yes, it was my fault, too, so mea culpa! But let me explain.
Basically, and unlike Facebook, forums are threaded. Conversations routinely take months and years to die. And it's important to recognize, you're notified of new posts so you can keep up. How? Easy; open your yap (even just once).
At that point you're officially part of the peanut gallery (unless you subsequently ,expressly, opt out). Anyway, and as the peanut gallery is wont to do, OP was being told not that his grandchild was ugly (definitely not true), but he was definitely shall we say . . . being gently schooled.
Think of the smart students ss believing they knew more than the teacher and thus, were eager to teach him. In this case, as if an +80 year old uber-experienced craftsman such as he 'still' needed to be taught much of anything - but I digress. Just bear in mind, few modelers can help but avail themselves of the opportunity to 'help' another modeler. Me, least of all.
Proof of all this being we'd gotten sidetracked from engine installation (very nicely done) to equipment installation. This is an area rife for various opinions and opinions being like bellybuttons (we all have one), we had delved into the rabbit hole regarding the pros and cons of various ignition switches, and their types, and then batteries, too!
did I step in the cow patty?Well, eager to make my point, I posted a gruesome picture, one which drew the red card by the OP. Another ref concurred. Since by then the thread had also birdwalked further (evolved into the topic of batteries when the foul was called protesting the photo), OP also mentioned the radio-type material kindly be removed from his thread, also.
He was right and I promptly complied. This, because we were far afield from his gorgeous scratch built model. Put another way, we were well and truly deep into the weeds by anybody's measure!
Since information never dies, the point being, you are now where said information presently reposes. Make of what follows what you will, but know this; it contains the yuk photo in question. Thus, consider this your heads up before scrolling further, OK?
Further background
What follows are both what was excised, and my fuller thoughts. And note; we began this conversation with respect to switches, specifically of a type for use for engine cutoff of gasoline ignition engines before going onto batteries. You get to learn a bit about both in one brief article, a twofer!
First, the photo I was asked to remove. It's of a friend's hand he put in front of him to keep from being eaten up by his model airplane's propeller. Ugly wound.
- Think of a spinning prop as flying ginsu knife blades . . . with an attitude!
So this photo is actually used for a reason, and it isn't to gross anyone out. That it is gross, however, of that there is no disagreement from me. However, I'm trying to convey the seriousness of your decision for using the manual-cutoff type, which I favor versus radio-cutoff types of ignition switches.
You see, gasoline ignition engines can start and run at the flip of a prop. And since these engines require fuel and air, compression, and ignition to run, then interrupting any one of those means it won't run. And the wisdom that's evolved is a switch to electrically cut off the possibility for ignition is 'the' way of keeping the engine from running. The point of this being, of course, to keep flying ginsu knives away from human body parts!
Switches - technical details of two basic types
Whether an engine ignition works via megneto or battery powered ignition isn't germane, you have to cut off the ability for either to let a spark plug sparking, or igniting the mixture of fuel and air, which lets the engine run.
Toward that aim, an NGO called International Model Aircraft Association published a set of rules, amongst them ones dealing with disabling the ignition in the interests of safety. Note; the IMAA is the largest special interest group of the Academy of Model Aeronautics, or AMA. As such, it represents the interests of giant scale radio controlled modeling community.
Anyway, if you don't have your copy of the IMAA Safety Code handy, and while I'll be first to admit it's seriously out of date regarding servos and DC power for same, what remains as pertinent as ever is section 5. There, as regards ignition engines (both magneto and battery powered) it says, specifically about switches . . .
Section 5.0: EMERGENCY ENGINE SHUT OFF (kill switch)
5.1 All magneto spark ignition engines must have a coil
grounding switch on the aircraft to stop the engine. This will also
prevent accidental starting of the engine. This switch shall be
readily available to both pilot and helper. This switch is to be
operated manually and without the use of the radio system.
5.2 Engines with battery power ignition systems must have a
switch to turn off the power from the battery pack to disable the
engine from firing. This will also prevent accidental starting of
the engine.This switch shall be readily available to both pilot and
helper. This switch shall be operated manually and without the
use of the Radio System.
.
. . so please don't shoot the messenger on this. Blame the defunct IMAA
for codifying common sense rules for keeping us as safe as possible.
And if this photo doesn't give you pause regarding how consequential your decision may be, nothing will (and it's my opinion you should take up another hobby) because a spinning giant scale prop is effectively a set of spinning ginsu kitchen knife blades!
This photo expressly drives home the need to take special cautions with these big boy toys we call scale mode airplanes because they can be dangerous. So I used a photo expressly to make a point and the OP promptly asked me to remove it and certain information because it was both gross and being about control elements of radio equipment, were not specifically germane to his thread and a model he made of a lovely civilian aircraft.
So judging both of his points to be valid and true, I removed the photo and the information. However, I didn't share the photo to gross anyone out but to make a point, a reasonable one in my estimation, if not one that is entirely necessary for me to offer up to a wider audience. You!
SWhat I am leading up to is saiid image 'is' included within this material and in the interest of not offending folks, please consider yourself warned because it depicts my friend's terribly wounded hand, which was a direct result of warding off a engine-driven propeller. -- John
Background
My friend was interested in using a switch to cut off the ignition, which depends on the radio functioning. Since the ignition can bleed into the receiver and prevent it working, this is dangerous. Enough so the IMAA Safety Code, rule 5.0 specifically directs the ignition of a gasoline ignition engine, whether magneto fired or one using a battery powered ignition module, be able to be disabled via externally mounted switch. Here's where we were in the conversation . . .
In the alternative, you can always put your hand out to stop the beast eating you alive. This photo shows the result of a good friend doing just that to protect himself from the prop. And while his hand's healed, he lost function of that knuckle because the doctor had to obliterate it and fuse it into a solid joint. And yes, he flies to this day.
So, now switching gears to batteries. FYI, I've begun steering clear of 'po' constructed batteries of all sorts for control avionics because they can shift in flight and be damaged, or just due to the adverse effects of being handled in the workshop (dings or dents incurred just by being set down on a tool, for example).
This means in addition to LiPo (for which there's no reasonable substitute for propulsion), we have eliminated LiFe packs from our offerings (the ones that look like bricks). This was due to how easily they were damaged being handled as well as how many would go bad merely sitting on the shelf (+5%). And this was after three different vendors as we switched up thinking the problem was due to inadequate suppliers!
Another way to look at 5% is . . . 1 out of 20 packs! So when I hesitated to reach for one for one of my own models, the die was cast and we took them all off the shelf and over to the recycler. This was 'me' effectively putting about $6000 worth of packs out of my pocket and where my mouth is! Major point being, if I won't use it I sure won't sell it.
Our goto these days are receiver packs constructed with either LiFePO4 cells (A123) or Lithium-Ion (LiIon). This is because both are made with individual cells encased in metal shells, which are more durable and proof against life's little knocks.
Anyway, I have packs built with two receiver leads going to the receiver, a balance connector, and an XT30 (to make charging more convenient and avoid the 5A limit of the Dupont connector). FYI, amongst modelers Dupont ctors are often known as JR type (Hitec, Futaba, et. all based on a 0.10 spacing). With regard to why two Dupont connectors, we have two because;
facilitate using two switches in parallel remember, I hate switches for a reason), and
since each black connectors is rated at 5A each, with two we permit 10A of current to flow to the receiver.
. . . this last is important these days because high performance servos consume lots of current. Note, both of these (and the balance connector) are on 20AWG silicone wire. And the XT30 connector on 16AWG wire. Link to batteries.
Anyway, batteries are a commodity, we (the entire hobby industry added up) don't buy enough cells to justify manufacturers doing anything special for us. I'd estimate we buy less than a millions cells per year from an industry that produces 5 million per day. Point being, nobody gets 'special' cells. That, and building packs isn't rocket science. Proof being so many of us make (or have made them up) ourselves with perfect safety and reliability.
Note, the label has a place for the date. Use a Sharpie and write it in. And another thing, when capacity is down to 80%, toss the pack because you've gotten your money's worth out of it. My 2¢ on the subject.