I have a '47 Desoto convertible that has been converted to 12 volt. Can I use the the 6 volt top motors if I take it easy a bit at a time, or do I have to to go through the hassle of rewiring the motors? I might raise the top 3 times a year.
Are these motors coupled mechanically or do they drive hydraulic pumps? If hydraulic, you can probably run them on 12V safely. If mechanical, I'd hesitate to run them on 12V because of the increased speed which may cause issues in the top linkage. If there's two motors, you could wire them in series, each would then get 6V, but make sure the wire size is adequate for the load.
I'd put a 12v top motor in it and be done with it. I know where a brand new one is and can find out the cost if you want. Belongs to a friend that I work for. My only experience with a top motor was changing out one in a 54 Chevy. Used one from the wrecking yard. The motor powers a pump. Yard owner told me in all his years he never had a bad motor. The pump would get dirty and you opened it up and cleaned it. He was good enough to show me the way to do it.
Wiring in series only works if they are the same size, run at the same time, under the same load... I'd probably rely on electronics, and build a simple circuit based on a 555 timer and a power transistor to switch the power to the motors on and off at a relatively high frequency. If you give them 12V for 50% of the time, they'll run as if on straight 6V. The method is called pulse width modulation, PWM, the light dimmer in your house does basically the same thing. Works fine for motors, incandescent/halogen light bulbs and similar simple things, but not for electronics such as radios.
I assumed they run at the same time. It's not a hydraulic top, so he's probably got one motor operating a screw on each side rather than a hydraulic ram on each side. If that's the case, wiring the motors in series would be the simplest solution.
Yes there is one motor on each side. Another thing, it was positive ground. Does that make any difference?
Get an adjustable carbon pile resistor from a battery tester, and wire it into the circuit. Then you can keep your 6V motors, and adjust their speed by turning a knob. https://www.ebay.com/itm/Atlas-carb...722236?hash=item2cab132f3c:g:wDEAAOSw5L9XD9uR
Positive ground won't matter, but you'll probably have to flip the motor leads to get them to go the right direction according to the switch. How many/what kind of motor leads you have will matter though; if they're two-lead with no local ground, the wiring will be fairly simple. If they're three-lead or two-lead with a local ground (one wire for up, the other for down, one ground) it will get a bit more complicated as you'll have to series the ground connections which may require some mods to isolate the grounds. I won't recommend using a resistor as that will double the circuit load.
A resistor in series is a (relatively) bad method to reduce voltage to an electric motor. When the motor starts and any other time rpm is low and/or load is high, it draws much higher current than when running at normal rpm, and normal/light load. The resistance chosen to give it 6V at normal speed and load may only give it 1 or 2V when it's (supposed to) start. At that low voltage it will be very weak and makes a sluggish start, if it starts at all. Locked up with current going through it, it may burn out if not turned off. Something that gives out a (more or less) regulated voltage is much better.
I ran the one in my 48 Pontiac for 20+years, [disconnected the hydraulics after unrelated leak didn't like the thought of all that brake fluid spraying around] the system on the Pontiac was just a 6 volt starter motor connected to the pump it worked great just twice s fast as stock. putting the top up and down manually isn't hard just keep pivots lubed
The Jalopy Journal
