Thank you so much for this video. I'm relatively new to the hobby, but I love rubber powered models and have built a few planes. I've always been a bit confused on the "formula" for making a proper motor until now. Now I understand weight v. number of strands v. length and how to get there. I just wasn't putting it together from the books I have. Awesome and informative video!!!!
Interesting way of making up a motor. I do it the John O’Donnell way. Knowing how many loops I want I lay it out between two pegs. To even the loops out I waggle my arms like my mother did converting a ball of wool into loops. Not easy to describe. If you’ve ever done “wind the bobbin up” with a grandchild then that’s it. The loops are around your wrists at right angles to your body and the rubber is rolled one way then the other. This takes up slack in the loosest strands till all are equal. I put a drop of cyano on the tails and use a simple one loop knot. I use more than 0.6g of lube.
First of all you have to take your rubber band and suspend different masses and find non linear stiffness coefficient. This is not quite as straightforward and needs some curve fitting. Then you can use the shortening length x stiffness number /2*pi to find the energy.
Hello, I'm Claudio Fabris, I saw and listened carefully to your explanations to make an F1B engine, a category in which I perform in Argentina. In one of the passages of the video I see that in your garage you have a test bench for the rubber motor, my serious question, do you measure the energy of the rubber before or after lubricating it? greetings and good flights
Hi Claudio. I do all non-destructive testing with motors that are unlubricated. That is because based on the tests, I may want to restrand, which is a mess if done with a lubed motor. I put a small amount of lube on the ends of the motor where is pulled. After that they get washed, dried, and lubed. Full back-wound torque/turns tests are of course done with lubed motor, but are destructive.
@@jerryfitch8101Hi Jerry, thank you very much for your response. It would be extraordinary if you made a video on how to measure the energy of the rubber with your machine, I have a manual one but with a friend we are building a mechanic with a load cell and a stepper motor, the only thing missing is the program to do all the steps to measure the energy of the rubber, that's why we could use a video of your procedure. Thank you so much!!
I hope this expert modeler makes a video on ANYTHING he does. 🥰🙏 Please 🙏. Buying storing washing rubber lubricating rubber tying rubber storing rubber freezing rubber I don't know then balsa and then wood. There's unlimited sources for this man's knowledge.... please. ❤❤
To measure motor energy, I connect it to a torque meter, wind it to full capacity (a subject in itself), un-wind while speaking observed torque into the phone at 20-turn intervals. So this is also a manual method. I leave electronic methods to those with the expertise. The energy can then be calculated by summing the energy increments, each one given by the formula e=(2)(pi)(turns)(average torque for the increment). Unfortunately, winding to capacity destroys the motor. There are various non-destructive proxy tests to predict motor energy, but none that I have tried, and I have tried many, are reliable.
For a 14" motor, say 140 in-oz. at 70 F. Higher temps means lower torque. Controlling and monitoring in-tube temp is an inexact technology at present. Carbon tubes can get really hot in the sun and really cold other times, radiating heat into outer space.
Hi Clovis. There is only one source I know of in the world. Google "FAI Model Supply" for information. I am using rubber from a 10 pound box of 1/16" rubber in the video. But they also have smaller quantities.
@@jerryfitch8101 well "about" 420 ... because you are probably going to underwind and then add hand turns and your precision is not high enough to know that it is 424 exactly because there is significant uncertainty in your length measurement and the properties of the rubber from segment to segment in the box .... right? So shouldn't you say "420 +/- 15"??
@@hummingbirdmodelproducts2691 Actually the length measurement is pretty good, 3 sigfigs as shown in the video. What's not in there is the testing process that yields a stretch ratio, which gives me an "effective length". That may be much different from the measured length and about half the time requires restranding the motor. Anyway, the final effective length predicts the turns, all by formula, so I keep all the sigfigs, like 424, and wind to that number. And then ratchet on turns to a torque. And my working theory is that torque to breaking is determined by cross-sectional area, which is hard to measure, but which must be inversely proportional to the actual (not effective) motor length, as restranded or not. And of course affected by temperature. All good stuff to investigate.
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Thank you so much for this video. I'm relatively new to the hobby, but I love rubber powered models and have built a few planes. I've always been a bit confused on the "formula" for making a proper motor until now. Now I understand weight v. number of strands v. length and how to get there. I just wasn't putting it together from the books I have. Awesome and informative video!!!!
Interesting way of making up a motor. I do it the John O’Donnell way. Knowing how many loops I want I lay it out between two pegs. To even the loops out I waggle my arms like my mother did converting a ball of wool into loops. Not easy to describe. If you’ve ever done “wind the bobbin up” with a grandchild then that’s it. The loops are around your wrists at right angles to your body and the rubber is rolled one way then the other. This takes up slack in the loosest strands till all are equal. I put a drop of cyano on the tails and use a simple one loop knot. I use more than 0.6g of lube.
First of all you have to take your rubber band and suspend different masses and find non linear stiffness coefficient. This is not quite as straightforward and needs some curve fitting. Then you can use the shortening length x stiffness number /2*pi to find the energy.
Hello, I'm Claudio Fabris, I saw and listened carefully to your explanations to make an F1B engine, a category in which I perform in Argentina. In one of the passages of the video I see that in your garage you have a test bench for the rubber motor, my serious question, do you measure the energy of the rubber before or after lubricating it? greetings and good flights
Hi Claudio. I do all non-destructive testing with motors that are unlubricated. That is because based on the tests, I may want to restrand, which is a mess if done with a lubed motor. I put a small amount of lube on the ends of the motor where is pulled. After that they get washed, dried, and lubed. Full back-wound torque/turns tests are of course done with lubed motor, but are destructive.
@@jerryfitch8101Hi Jerry, thank you very much for your response. It would be extraordinary if you made a video on how to measure the energy of the rubber with your machine, I have a manual one but with a friend we are building a mechanic with a load cell and a stepper motor, the only thing missing is the program to do all the steps to measure the energy of the rubber, that's why we could use a video of your procedure. Thank you so much!!
I hope this expert modeler makes a video on ANYTHING he does. 🥰🙏 Please 🙏. Buying storing washing rubber lubricating rubber tying rubber storing rubber freezing rubber I don't know then balsa and then wood. There's unlimited sources for this man's knowledge.... please. ❤❤
To measure motor energy, I connect it to a torque meter, wind it to full capacity (a subject in itself), un-wind while speaking observed torque into the phone at 20-turn intervals. So this is also a manual method. I leave electronic methods to those with the expertise. The energy can then be calculated by summing the energy increments, each one given by the formula e=(2)(pi)(turns)(average torque for the increment). Unfortunately, winding to capacity destroys the motor. There are various non-destructive proxy tests to predict motor energy, but none that I have tried, and I have tried many, are reliable.
How do you stretch it before flight, what length, how long and what parameters are measured?
Thank you for posting this, The rubber band Jedi trick...Very cool. What is the torque you are looking for with this motor?
For a 14" motor, say 140 in-oz. at 70 F. Higher temps means lower torque. Controlling and monitoring in-tube temp is an inexact technology at present. Carbon tubes can get really hot in the sun and really cold other times, radiating heat into outer space.
Hi Jerry, What is or is in the lube you are using? There are a number of beliefs on what to use. Is there a specific brand name ? Thank you.
😳🤯. Do all your friends have inches marked on the floor of their garage? ....... This is my future isn't it??😅
So how's the rubber comparing to the 10/97?
Good morning my friend...a única coisa que seI na sua língua..me fala onde consigo esse elástico( Rubber) aqui nesse país não se acha.
Hi Clovis. There is only one source I know of in the world. Google "FAI Model Supply" for information. I am using rubber from a 10 pound box of 1/16" rubber in the video. But they also have smaller quantities.
GOOD MORNING FRIEND THANKS FOR THE RESPONSE BUT IT TAKED TO SEE OK BUT THESE RUBBERS YOU SELL AND ARE USED FOR AEROMELO YES.@@jerryfitch8101
@@clovisaraujocruz5921 Sorry Clovis, something lost in translation. Post it in Portuguese and I'll let Google Translate have at it.
How many turns can you expect from that motor?
424
@@jerryfitch8101 well "about" 420 ... because you are probably going to underwind and then add hand turns and your precision is not high enough to know that it is 424 exactly because there is significant uncertainty in your length measurement and the properties of the rubber from segment to segment in the box .... right? So shouldn't you say "420 +/- 15"??
@@hummingbirdmodelproducts2691 Actually the length measurement is pretty good, 3 sigfigs as shown in the video. What's not in there is the testing process that yields a stretch ratio, which gives me an "effective length". That may be much different from the measured length and about half the time requires restranding the motor. Anyway, the final effective length predicts the turns, all by formula, so I keep all the sigfigs, like 424, and wind to that number. And then ratchet on turns to a torque. And my working theory is that torque to breaking is determined by cross-sectional area, which is hard to measure, but which must be inversely proportional to the actual (not effective) motor length, as restranded or not. And of course affected by temperature. All good stuff to investigate.
@@jerryfitch8101 would be interesting to see video about motor testing process aswell
Como se fás praconseguir essa liga de borracha
Only this first item short in our country
Motor rubber
Si él puede traducir al castellano