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R69 (and other) field coil repair?
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
Total length - 60.25'
Resistance before unwinding - 0.5 ohms (my multimeter only goes to one decimal)
Resistance after unwinding - 0.5 ohms
I was hoping to see an increase in the resistance after unwinding which would have indicated some shorting between the coil strands, however that was not the case.
Based upon the specs, 60.25' of 19 awg magnet wire should have 0.49 ohms of resistance, which seems close enough to 0.5 ohms to me. I will check the resistance of the new 19 awg magnet wire when I get ready to wind a new coil. I'm printing a winding device on my 3D printer as we speak.
Lessons learned - this coil seems to be OK. The other 3 measure at 0.4 or 0.5 ohms, so they are likely OK as well, though I haven't unwound them to check. It seems like the case of the missing ohms has yet to be solved, or perhaps the literature is incorrect. This is how we learn (haha).
I've ordered an electric 6V voltage regulator, which is probably what I should have done first.
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
- wa1nca
- Posts: 1229
- Joined: Thu Sep 27, 2012 5:15 pm
- Location: Ashfield Ma
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Re: R69 (and other) field coil repair?
1st one 2.2 ohms
2nd one 2.0 ohms
Tommy
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
Mine measured up at 1.8 ohms and, theoretically, a unit should measure in at 2.0 ohms given the specs of the magnet wire used to make it.
Here's a few pictures of the coil winding device I'm 3D printing. I tried to wind the coil in the arced shape necessary to fit into the generator, but that's a bust. I cannot wind it cleanly. I'm going to try to wind it as a disc and then form it to the needed arced shape, next.
This is even harder than I thought it might be.
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
I modified the winder to have a disc shaped spool, rather than an arc. I was never going to be able to cleanly wind the coil in the needed arc shape. I also added a brake. The brake creates drag to keep the wire taught while winding. I decided to pre-cut the length of wire needed and wind it onto a separate spool, rather than coming off the big 1.5 lb, 365 ft. spool. I only need 60.25' for each field coil.
I did a test run on the new spool and was able to come up with a good winding until about 75% of the way through. I accidentally released the tension for a split second and it unraveled a bit. I have some clear varnish coming from Amazon tomorrow and I will use it in the next round to help keep things together. I will only add a little bit of varnish in a few spots after completing each layer of windings. I'm not sure if it will dry quickly enough to be useful. If not, I will have to find something else. Maybe CA glue?
I also printed out a press forming tool to shape the coil from a disc-shape into the needed arc-shape. I'll either use my bench vise or hydraulic press to muscle the coil into the desired shape. The pictures make this a little easier to understand.
So, my plan is to:
- Cover the spool surfaces with car wax, to help with removal of the wound coil
- Wind the coil on the spool and add a little varnish after each layer to help it stick together, but not so much that it can't be formed
- Remove the field coil from the spool and wrap with white field coil tape
- Cover the press tool with wax, then insert the field coil, and press to the correct shape (hopefully!)
- Remove the coil from the press tool and do a final coat of varnish
New improved spool winding tool. This picture was taken after the accidental unwinding occurred. Hopefully each layer will be nice and neat, especially when I use varnish to hold things together, and I'll end up with something very orderly.
Press form to shape field coil into desired arc
Press form with original field coil, for illustration purposes
Press form with original field coil, for illustration purposes. I will put the new coil in this and use my hydraulic press or bench vise to create the needed shape.
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
1) The ID of my spool needs to be enlarged. Even though I took into account that the coil would be wrapped in cloth electrical tape, the ID was still too small to fit onto the metal shoe that holds the coil in the stator body.
2) When forming the coil with the press tool, it springs back slightly. The shoe might take care of that, but I can't yet test because the ID of the new coil is too small to fit onto the shoe. Also, I need to cover the new coil with varnish, which might prevent the coil from being pulled into shape by the shoe. I'm not sure. I might remake the press tool so that the coil bends a little past the desired point and then springs back to it.
3) My coil is slightly too wide and I will make it a bit narrower.
Pictures say 1000 words so....
Old vs. New after coiling
Old vs. New, after wrapping
In the press
Old vs. New after being in the press
Old coil in housing
New coil in housing - didn't bend quite far enough.
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
Here's the new tool set up and ready to press.
Pressed to the maximum amount.
Relaxed/rebounded back after the pressure is released.
And, finally, comfortable sitting inside the generator housing
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- Posts: 100
- Joined: Fri Dec 16, 2016 6:39 pm
- Location: Hollyweird, CA
Re: R69 (and other) field coil repair?
Thanks for the encouragement Chris. I hope to be winding all four coils this weekend. I also have the electronic voltage regulator. I'll update accordingly.