Maximum Turns
There is a formula for ESTIMATING the maximum turns a motor will take before breaking.
T = LKt/sqrt(S)
T – turns
L – length of motor
Kt – empirical turns coefficient
/ – divide
sqrt(x) – square root of x
S – cross section of motor
Cross section of motor is the product of number of strands, strand width and strand thickness.
S = nwt
n – number of strands
w – width of strand
t – thickness of strand (Modern Super Sport rubber nominal thickness is 0.042″)
Kt will be different for different batches of rubber. It can vary some within a batch. It will vary with temperature. It will vary with your lubrication and winding practices. It is established through testing. Make up and wind test motors in your usual way at standard temperature, record the breaking turns and calculate values of Kt from Kt= Tsqrt(S)/L. With lengths in inches, a value of 10.5 is a safe default for modern Tan rubber. You may find values as low as 9 or as high as 13. If you need a more precise value, you must test your own rubber.
You should not use this number to decide when to stop winding your motor. It is an ESTIMATE to be used as a guide for when to pay close attention to the motor. As the motor approaches its maximum torque it will become less flexible. You can sense this by stopping your winding, letting the motor cool and giving gentle tugs on the motor. When the motor becomes very stiff it is time to stop winding. Knowing when to stop winding is a matter of judgement borne of experience. Motors that have been used may break sooner than expected. Motors that are wound fast will break sooner than expected. Motors that are allowed to cool by slowing the winding, especially at the high end, will take more turns.
Breaking Torque
There is a formula for ESTIMATING the maximum torque a motor will take before breaking.
Q = KqS^1.5
Q – torque
Kq – empirical torque coefficient
S – motor cross section
^1.5 – exponentiation to the 1.5 power
Most calculators have an x to the y button where you enter S, push the button, enter 1.5, press =. A number to the 1.5 power is the same as to the 3/2 power. This can be calculated by multiplying the square root of S by itself three times.
Cross section of motor is the product of number of strands, strand width and strand thickness.
S =nwt
n – number of strands
w – width of strand
t – thickness of strand (Modern Super Sport rubber nominal thickness is 0.042″)
Kq will be different for different batches of rubber. It can vary some within a batch. It will vary with temperature. It will vary with your lubrication and winding practices. It is established through testing. Make up and wind test motors in your usual way at standard temperature, record the breaking torque and calculate values of Kq from Kq = Q/S^1.5. If you need a more precise value, you must test your own rubber.
With torque in gram centimeters and lengths in inches, a value of 100,000 is a safe default for modern Tan rubber. With torque in inch ounces and lengths in inches, a value of 1,400 is a safe default for modern Tan rubber.
You should not use this number to decide when to stop winding your motor. It is an ESTIMATE to be used as a guide for when to pay close attention to the motor. As the motor approaches its maximum torque it will become less flexible. You can sense this by stopping your winding, letting the motor cool and giving gentle tugs on the motor. When the motor becomes very stiff it is time to stop winding. Knowing when to stop winding is a matter of judgement borne of experience. Motors that have been used may break sooner than expected. Motors that are wound fast will break sooner than expected. Motors that are allowed to cool by slowing the winding, especially at the high end, will take more torque.
Daha basit hesaplar göstermelisiniz.
Örneğin lastiğimiz 1mmX3mm ve uzunluğu 250mmX2 ve bir ucu bağ atılmış pozizyonda ;
850 makine ile sarim baraj lastik kopuyor fakat elde makara ile sarim 1250 ve üzerine çikabiliyor yani soğuk sarim.
Soru: 1mmX3mm lastik soğuk sarım elde makara ile dönüş sayısı maximum kaç olacaktir.
Google Translate says this is Turkish and gives this:
You should show simpler accounts.
For example, our tire is 1mmX3mm and its length is 250mmX2 and one end is bonded;
With the 850 machine, the winding dam tire breaks, but with the hand reel, the winding can go up to 1250 and above, so cold winding.
Question: What will be the maximum number of turns with a 1mmX3mm rubber cold winding reel.
I take it that ‘tire’ means ‘rubber’.
Hi,
Very interesting formula, I suggest adding some examples to be clearer.
My rubber is 700 mm X 3 mm X 1 mm before loop, so :
1- L will be 350 mm ? or 700 mm.
2- If one loop, S will be 2 X 3 X 1 ?
What is the correct answer ?
A- T = 350 X 10,5 / sqrt(3 X 1 ) = 2121 turns
B- T = 700 X 10,5 / sqrt(2 X 3 X 1) = 3000 turns
C- T = 350 X 10,5 / sqrt(2 X 3 X 1 ) = 1500 turns
D- T = 700 X 10,5 / sqrt(3 X 1) = 4243 turns
Thx
C is correct. The length of the motor is the length of the loop, which is half the length of the single strand. The cross section of the loop is twice the cross section of the single strand.