There is a bit more too it than that, though you have the basic idea right. A good rule of thumb in choosing the correct size of rubber band is that you should have about as many turns left at the end of the flight as you backed off at the beginning (assuming you are flying in a low ceiling gym and backing off alot). This is the best place to fly because you are in the flattest part of the rubber bands torque vs. turns curve and will have and nice slow climb a good cruise and a long decent. The same torque on differently size rubber bands will fly your plane differently because each will have a different cruise torque. But it is a useful metric when you are comparing two motors of the same size. If they are wound to the same torque and turns they should fly similarly. I can dig up an old torque vs. turns graph if you think it would be helpful.. Am I correct that the two things I need to concentrate most on with the torque meter is the relative breaking point of each size of motor and the torque at which this plane flies level? Second question is will the same torque on different motors fly the plane the same?
Yes, the more times you wind an individual motor= you can put in more winds than the time before,You must also track how many winds you have put on a particular motor. A motor will allow more winds at successive winds when wound to the same peak torque. If you know how many winds a motor has yielded in its first and second winds, you will have a good idea how many will be allowed on the third wind.
Hope this helps.
Yes, always use lube. Armor All original formula.Out of curiosity, was the rubber you were using lubed? If so what kind of lube?
I found the post from last year by jander14indoor and have pasted it below.but also realize that rubber has an energy curve. I've spend considerable time just know looking for a post that describes this but i can't find it. In summary, rubber that is wound close to it's breaking point becomes "tired." Therefore, after the motor becomes "tired" if you keep winding the same nuber of winds on it, you will not get enough the same amount of energy out of it.
Weeeellll, we're back into true but...
OK, thanks. On replacing rubber after every 2 flights. That doesn't seem quite right. It couldn't possibly be that FAI wants to sell more rubber, or could it? However, there must be a point where the rubber is stretched past the optimal elasticity, I think. <SNIP>
FAI is talking about winding motors VERY close to breaking when they say 'tired' after two flights. From my and many others experience this is true. You can even see the effect as such motors will show little edge knicks and other signs of stress. If you are winding well short of max you don't do much damage and you will get many more flights in. Resting motors helps with this, lets those long stretched out chain molecules in rubber reset.
Of course the question arises why is FAI warning about this? Turns out they are trying to help the customer with knowledge, not just sell more rubber. A competitive free flighter (even indoors) WILL wind motors very near max in competition, every time. Why you ask? Because you can get more winds in the motor by winding to near max and unwinding to launch torque than you can by winding to launch torque to start with. More winds is more fuel is longer flights. That's how you win.
One thing I've observed is that many SO flyers have only a few motors from a kit or small bag of rubber so they tend to underwind to avoid breaking the motor. Understandable behavior, but very limiting to flight time. Though conducive to longer motor life.
So, what to do.
First, realize rubber is fairly cheap. At 1.5 gm per motor, you can make 35 +motors from a $13.20 with shipping 1/4 lb (113 gm) box, so get extra rubber. A half pound box for 70 motors is only $19 or so.
Next, learn where you motors break! This is where a torque meter comes in handy as motors break more on torque than winds and you can see how close you are getting. You'll find the max torque is way beyond reasonable launch torques in all but the very tall sites. You can do this with winds too, just not as consistently.
Break in your motors because rubber motors change a LOT on that first wind, even if well below max. Breaking it in allows more repeatable flights for the rest of the motors life. It should be done by winding to 80% or so of breaking torque (some like higher, some just stretch and hold) and held for a while.
Now, wind past your flying torque, but well short of breaking for practice. Learn plane settings, etc. Reuse motor as long as performance doesn't degrade or rubber breaks. Fly an occasional practice flight by winding to 95% or so of max and backing off to flying torque. You'll find you add a significant number of turns.
In competition, do just enough practice flights to get dialed into the site. Do one practice full winds and backoff. For the flights that count, wind as close to breaking as you dare, backoff to launch torque and go. Everytime.
Everyone says how lube allows you to put more winds into the rubber. This is its purpose: to allow you to wind the motor more before it breaks. Has anyone actually tested this though? or has everyone just accepted this as fact without verifing it?Yes, always use lube. Armor All original formula.
Preferably a torque meter, but if not you can make a hook out of some stiff wire and attach it to something like a 3-inch C clamp and clamp that onto a table or the bleachers.alright thanks.
BTW i didnt' trust the owner but i wasn't paying for it so it didn't hurt to get it.
Now my next question is kinda stupid/simple but there's reason behind it.
It is advised that during testing the rubber motor should be wound OFF the plane. This is because it could break and potentially damage the plane. When winding off the plane one side of the rubber is attached to the winder. What is the other side attached to?
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