In my Land Rover starter motor, the field coils are wrapped in cotton tape. I see that Egyptian cotton tape is sold for this purpose, but I am told I could use rubber tape. Will this interfere with any magnetic field? Why did they use cotton tape?
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1\$\begingroup\$ Rubber tapes will probably degrade in less than 30 years. In a Landrover, that could be a bit of a problem. \$\endgroup\$– user16324Commented Mar 12, 2018 at 19:06
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2 Answers
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They used the cotton tape as it has good resistance to oil for one and temperature for another.
It will not affect the magnetic field - efficiency was not highest on the design priority list...
Also, some "rubber" based tapes can expand with oil contamination so be careful what you use.
answered Mar 12, 2018 at 15:27
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\$\begingroup\$ Thank you for that, as it is important that the field coils do not short out on the outer casing I would have thought that insulation tape would have been a better bet, in my case rust inside the case has decayed the cotton tape quite badly, hence the short, surprised that the magnetic field in not affected with rubber tape, Live and learn! \$\endgroup\$– plonkerCommented Mar 13, 2018 at 21:29
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\$\begingroup\$ It is also important that the field coils don't short between each other as well.... \$\endgroup\$ Commented Mar 13, 2018 at 22:47
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\$\begingroup\$ I do not understand, The field coils are connected to each other at one end, there are four coils in the motor, and three of them are connected?How can they short? \$\endgroup\$– plonkerCommented Mar 14, 2018 at 23:20
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Use Kapton tape. It is thinner, inert to oil and good in high temp applications. As it is thinner, your coils are closer to the core and create a stronger field.
