Trimming

[InfiniCuber]

I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness. I am securing the loop using a square knot and a very small ammount of gorilla super glue to ensure that the knot does not come undone. Is it normal to have motors break this often or am I doing something wrong?

From my experience, rubber bands will break relatively often, just perhaps not as often as you are experiencing. Are you using lubricant for your rubber?

Yea we use armour all as a lubricant and we apply it before every flight.

Alright that's good, sometimes leaving the rubber soaking in it for a bit helps too. I would personally make some test rubber bands, and then test what their breaking point is in regards to torque. Then when winding for a flight, wind only to about 80% of that, and this data should help you not break your rubber.

[jander14indoor]

Where are your motors breaking? How and where do you store your motors? How hard are you winding, is it close to breaking?

The motors don't last forever.

What is a reasonable life.
Winding hard (>95%)with well kept motors, a couple of flights is considered good.
Winding 80% with well kept motors, 5 flights is on the low end, 10 reasonable, 15 plus not too rare.
Not well kept, you might not get one wind to the torque you expect.

Things that shorten life.
Winding HARD(90% plus of max torque, more is worse on life). Of course if you want to win you'll need to wind hard in competition and at least sometimes in practice.
Not keeping them clean, try not to drop them on the floor for example.
Storage temperature, heat is bad.
UV Light, these things don't like the sun.
Some chemicals. Particularly some plastic bags off gas nasty chemicals. Archival quality bags or paper envelops are best. Ozone is bad and common around electric motors. Some places in your house may have an excess of Ozone.
Anything hard or sharp while winding. I don't like glued knots myself for that reason. I use the double overhand knots as I find them easy to adjust and I've never had one slip. But I know some people are successful with them.


Regards,
Jeff Anderson
Livonia, MI

[someusername]

Where are your motors breaking? How and where do you store your motors? How hard are you winding, is it close to breaking?

The motors don't last forever.

What is a reasonable life.
Winding hard (>95%)with well kept motors, a couple of flights is considered good.
Winding 80% with well kept motors, 5 flights is on the low end, 10 reasonable, 15 plus not too rare.
Not well kept, you might not get one wind to the torque you expect.

Things that shorten life.
Winding HARD(90% plus of max torque, more is worse on life). Of course if you want to win you'll need to wind hard in competition and at least sometimes in practice.
Not keeping them clean, try not to drop them on the floor for example.
Storage temperature, heat is bad.
UV Light, these things don't like the sun.
Some chemicals. Particularly some plastic bags off gas nasty chemicals. Archival quality bags or paper envelops are best. Ozone is bad and common around electric motors. Some places in your house may have an excess of Ozone.
Anything hard or sharp while winding. I don't like glued knots myself for that reason. I use the double overhand knots as I find them easy to adjust and I've never had one slip. But I know some people are successful with them.


Regards,
Jeff Anderson
Livonia, MI

Thanks for the information, I think the most likely thing may be winding too hard, but 1500 on a .094 seems low to me, but I also haven't looked into the breaking point of it either like Infinicuber mentioned. As far as overhand knots go, I'm not a fan of using them because the shape they make tends to get caught on my motor stick, which gets annoying at times.

[jander14indoor]

Put the knot at the rear hook and you won't have any problem with catching on the motor stick.

Are you winding to torque or turns? Torque is more accurate and consistent.
If you are winding to torque, look back at my posts where I discuss how to test motors and interpret the results. You really should know what the breaking torque of your motors is.

To avoid breaking when winding competition motors, inspect them carefully along the length. Look for knicks and cuts in the edges, don't use or depend on motors with such damage.
Oh, and you should break-in competition motors. Look around this sites archives for additional discussion, but a motor stores energy best after being stretched slowly to a significant portion of its capacity once. You may have noticed you get the best flights out of motors on the second or third flight if you don't break your motors in. If winding hard, you'll see a lot of fall off or breakage beyond the third flight or so.

Jeff Anderson
Livonia, MI

[fifty_missions]

.094 Rubber-

This is a pretty large cross section and at this loop size (to meet the 2 gram rule) makes for a motor than does tend to break after 1300+ winds. Be very consistent with following your procedures with your motors and treat them like human muscles. They get very tired when you max the winds. Rotate the motors between high torque flights and mark your bag or envelope for each "high torque" flight. Let the motors relax a good ten minutes or more before putting them through more stress. This procedure and those as described by Jeff Anderson should help prolong the life of your motors.

Good Luck,
50 Missions

[torqueburner]

I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness.

Earlier this year, we wanted to establish the breaking point for a new batch of rubber we had received. We used a 2.01 gram loop, cut to "0.095" as marked on a Harlan stripper, which resulted in a loop length of about 15 inches. (we used this one, as it finished a bit over 2g)

This loop had been wound once to a torque of 1.0 in-oz to break it in, our usual procedure. On the second wind, it took 133 X 15 = 1995 turns, and reached a maximum torque of about 1.9 in-oz., at which point it broke. So 1300 turns seems a bit low, though perhaps the breaking point will drop if the loop has been wound hard a number of times.

One other factor that occurs to me is how much you stretch it out as you wind. If you don't stretch out far enough, the rubber will form knots that decrease its ability to maximize turns at a particular torque.

[retired1]

2 g of .094 should give a loop of 15 to 16 inches depending on orings used. That should give at least 1500 winds and not break.
Check your lube. Check the bands for nicks or scalloped edges. Pre stretch the rubber. Back up 6 or more feet to start winding.

[someusername]

2 g of .094 should give a loop of 15 to 16 inches depending on orings used. That should give at least 1500 winds and not break.
Check your lube. Check the bands for nicks or scalloped edges. Pre stretch the rubber. Back up 6 or more feet to start winding.

I made the new rubber with no glue on it, so maybe that will fix the problem. On the issue of stretching rubber, I do stretch it about 3x its relaxed length, but I don't see how I would stretch it 6 feet. Wouldn't that damage the propeller?

[Chris_L]

Is there any way you could wind off your plane and then attach the wound motor to both the propeller and the rear hook? This could be done on a torque meter or something else. This would make it a lot safer just in case something were to happen with your plane. And you could stretch the motor out as much as possible which would help to add winds to the motor.

[torqueburner]

Is there any way you could wind off your plane and then attach the wound motor to both the propeller and the rear hook? This could be done on a torque meter or something else.

You can make a winding stooge that mounts the torque meter at one end, and has a dock for the winder at the other. Clamp this down, and you can stretch the rubber way out, then bring it in towards the meter near the end of the wind. When nearly finished, you can dock the winder to put on the last few turns before backing off. The one shown has a nail that acts as a brake. Pull it out to hold the winder handle in place while you are transferring the motor to the plane. (Even if you had no torque meter, you can use this to wind off of the plane.)

Winding Stooge.pdf

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