omega 1310 coil questions (for recoiling)

[brtvandenbroeck]

Hi all,

I have been breaking my head over how to recoil an omega 1310 motor, replacements are hard to find (or expensive) and I would like to glory of just fixing it myself. I have been doing some calculations about the copper diameter and length, but the results seem strange. I was hoping someone else tryd the same thing before and could help me out.

First of all, the tech sheet says the coil should be 2k2ohm (http://primrosesupplies.com/Swiss Tech Guides/Omega tech Guides/1310.pdf). Given this and the measured dimensions of the broken coil it should be easy to determine the copper diameter, right? however, doing the calculations I come down at 33micron. this seems quite strange as: a) its an unusual value for emamelled copper, 2) under a microscope the copper of the old coil looks just as thick as a 10micron wire I have laying around. So may questions are: does any body know the real diameter I should use? Did I overlook something? Is my math off? The calculations are added below

thanks in advance!best regards, Bert

The math:

# wire radius
r_d = 0.02/2
# coil inner and outer radius
r_inner = 1/2
r_outer = 4/2
# coil lenght
l_c = 10
# cutt through area of wire
A_d = (r_d**2)*3.14
# cutt through area of coil
A_c = (r_outer**2-r_inner**2)*3.14
# volume of coil
V_c = A_c*l_c
# volume of wire inside this coil
f = 0.9069 # maximum circle fill rate (https://en.wikipedia.org/wiki/Circle_packing)
f = 0.8    # a common sense adjustment
V_d = V_c*f
# V_d = 75
# so, the length of the wire
L_d = V_d/A_d
L_dm = L_d / 1000
# and its resistance
R_copper = 1.724e-5 # ohm*mm^2/mm at 20C
R = R_copper * L_d / A_d
# R = 16k5 ohm

# what the optimal diameter would be to achive 2k2
d_opt = sqrt(sqrt(R_copper*V_d/2200)/pi)*2
# --> d_opt = 0.033 mm

# sanity check
# volume of copper by weights measurement of old coil
V_copper = 1000*0.68/8.93
# V_copper = 76 ~ whats been calculated

[transporter]

way to many figures there for me I'm afraid, my mind is a boggle with DLC calculations at the moment, but, is there not another coil from lets say a miyota movement that would fit? I have no idea to be honest just spit balling an idea out there, you known just incase.

[brtvandenbroeck]

Hi transporter, 

Thank you for your reply. I did look for possible replacement, the only one know to fit is the tissue 2100, unfortunately these are rare as wel. I assume others might serve as a donor as well, but would't like to go buying movement after movement for test by trail. But maybe this extends my questions with: are there any other donor movements known?

Regards, bert

[LittleWatchShop]

1 hour ago, brtvandenbroeck said:

Hi all,

I have been breaking my head over how to recoil an omega 1310 motor, replacements are hard to find (or expensive) and I would like to glory of just fixing it myself. I have been doing some calculations about the copper diameter and length, but the results seem strange. I was hoping someone else tryd the same thing before and could help me out.

First of all, the tech sheet says the coil should be 2k2ohm (http://primrosesupplies.com/Swiss Tech Guides/Omega tech Guides/1310.pdf). Given this and the measured dimensions of the broken coil it should be easy to determine the copper diameter, right? however, doing the calculations I come down at 33micron. this seems quite strange as: a) its an unusual value for emamelled copper, 2) under a microscope the copper of the old coil looks just as thick as a 10micron wire I have laying around. So may questions are: does any body know the real diameter I should use? Did I overlook something? Is my math off? The calculations are added below

thanks in advance!best regards, Bert

The math:

# wire radius
r_d = 0.02/2
# coil inner and outer radius
r_inner = 1/2
r_outer = 4/2
# coil lenght
l_c = 10
# cutt through area of wire
A_d = (r_d**2)*3.14
# cutt through area of coil
A_c = (r_outer**2-r_inner**2)*3.14
# volume of coil
V_c = A_c*l_c
# volume of wire inside this coil
f = 0.9069 # maximum circle fill rate (https://en.wikipedia.org/wiki/Circle_packing)
f = 0.8    # a common sense adjustment
V_d = V_c*f
# V_d = 75
# so, the length of the wire
L_d = V_d/A_d
L_dm = L_d / 1000
# and its resistance
R_copper = 1.724e-5 # ohm*mm^2/mm at 20C
R = R_copper * L_d / A_d
# R = 16k5 ohm

# what the optimal diameter would be to achive 2k2
d_opt = sqrt(sqrt(R_copper*V_d/2200)/pi)*2
# --> d_opt = 0.033 mm

# sanity check
# volume of copper by weights measurement of old coil
V_copper = 1000*0.68/8.93
# V_copper = 76 ~ whats been calculated

I analyzed this a little differently than you.  Essentially, I put my analysis in a spreadsheet and worked it backwards by starting with wire diameter and calculating the total resistance.  I make the spreadsheet after doing a bar-knapkin analysis and I ended up with the same result.

Using 10 µm diameter copper wire, I calculated the total number of turns in one rank of the coil (using your inner and outer diameters).  Then I calculated the total number of ranks using the length of the coil.  Using number of ranks and your fill-rate factor, I calculated the total length of the wire.  Using resistivity of copper (rho) you gave, I calculated total resistance.

I get 10 meters of wire using 10 µm diameter copper wire yields 2.2kΩ.

 

[brtvandenbroeck]

Hi littlewatchshop,

Thanks for the reply! I will try your approuch and let you know my findings.

Kr, bert

[brtvandenbroeck]

Hi littlewatchshop,

Your advice helped! New calcutations say that indeed 10m yield 2k2 and 13m will fit the same volume of the old coil. So i can continue with the 10micron wire!

Kr, bert

[JohnR725]

Another way to find out what the wire is is ask this person and if you get an answer perhaps you could tell the rest of us.

https://timeguy.com/cradek/01594932723

 

 

[LittleWatchShop]

3 hours ago, JohnR725 said:

Another way to find out what the wire is is ask this person and if you get an answer perhaps you could tell the rest of us.

https://timeguy.com/cradek/01594932723

 

 

I sent him an email

[brtvandenbroeck]

Hi all,

Chris thetimeguy was very helpfull in expanding how he measures it and allowed me to share his method here:

"Hi Bert,

The trick to measuring wire diameter is to uncoil a piece of the old
wire, most of a meter is good if you can do it, and measure the
resistance and length.  From that you can easily calculate the
diameter using the resistivity of copper.  You can find online
calculators to do this.  Since the resistance varies with the square
of the diameter this will give you a very good answer, much better
than any optical technique you might try, especially because the
coating thickness on small wire can make up a significant portion of
the apparent diameter.  For thin wire this technique works really
well, and you can easily tell 12 micron wire from 13 micron etc.

I use lots of 15 micron wire and it's nearly an ohm per cm!  Very
easy to measure.

The 1310's wire is much larger than this of course.

There is no reason to believe they stayed the same over the
production of the 1310, so you should measure yours.

Cheers,
Chris

"

Right now I have done just so and concluded I need 30micon wire for the recoil of my watch.

@chris, thanks again!

Kind regards, bert

[JohnR725]

I don't suppose he mentioned were he purchases wire from?

[brtvandenbroeck]

He didn't mention, but I've bought every available 0.01 to 0.05mm wire from alibaba, expecting the diameter to not match exactly the description . I will double check if the resistance is correct before winding. professional sellers only per x kg's, so ordering a lot to test from alibaba is still much cheaper

[rodabod]

Is it open-circuit, and if so, have you tried unwinding some of the outer coils?

[brtvandenbroeck]

strangely the coil short circuited (measured without the rest of the electronics).I did an attempt to unwind/cut a piece (hoping the short would be in that part) and remeasured a few times. At the end not much was left of the coil, so had to take it as a loss.