Locked Shaft on Permanent Magnet DC Motor

you're right gringogreg the motor has a worm drive an the shaft and the locking effect must be due to the fact that you can't back drive the worm gear. I will need to use gears that are not worm gears.

I have come across a 12 volt dc reversible gearhead motor with a shaft output speed of only 160 rpm and a gear ratio of 50:1 which gives a motor speed of 6400 rpm. However this may also have a worm drive. The full load current of this little motor is 14 amps. I suppose I am not allowed to give the name of the supplier on this forum as it may be seen as advertising?

I have sent an enquiry to this supplier regarding the drive in the gear train.

I never liked the design of my gate opener. It seemed to be much more complicated than it needed to be. It has a reticulated arm to do the opening and in the end it failed because the cogs in the drive train were slipping when it had the load of the gate on it.

I have been looking for a worm drive about a meter long and I could get the gate opener working again with the motor part I still have and minus all the other gears that were needed with the reticulated arm.

Would somebody know where I could get this type of worm drive?

Long worm drive? Try searching for recirculating ball screw for 3D printer, plasma cutter, etc. The same place may also supply guide rails and linear bearings that may be of use as well.

Jim

The gears on a windscreen wiper invariably use a worm gear. These cannot be used in reverse.

If it does not have a worm in the train then you still have the problem that the motor will exhibit characteristics like a stepper motor in that the poles of the rotor are attracted to the magnets. While this torque is easily overcome direct on the shaft the gearing multiplies this making it act like a brake.

Bad idea. For that motor to induce 12V ac, it will need to be rotated 10,000 rpm. How will you be able to rotate it at that speed using fan blade? I suggest you find low rpm, 12 volts motor or higher voltage the best. Also fan diameter needs to be designed(diameter size) in such away it can rotate the shaft. Air is less dense and compressible than water so diameter size of fan will be more than thrice or much bigger than turbine. You may use this formula #pole = 120*frequency/ rpm, ideal frequency is 50/60hz.

Where do you get the idea that this is about an AC voltage in any way shape or form?

I repeat my question.

And where do you get that idea that this is not about an AC Voltage in any way shape or form?

To quote OP "charge a 12 volt deep cycle battery" why would he want to go AC to convert back to DC?

Jim

Efficiency Dr Watson, efficiency!!

Not forgetting the massive reduction of wear, tear and corrosion on that motor that would also have wrecked it in a relatively short time anyway....

Hi Andy and Jimrat , OP wanted to built a wind generator (of course AC output) out of the DC motor which he is having problem how to make. He already had a solar panel rated 10 watts.

I did just that today;

A small permanent magnet motor that runs off 3v DC. I ran it at 2000 rpm and got 0.0000V AC and 0.25V DC. I have yet to connect to my CRO to look at the sort of output. Maybe that will show me why you expect it will be AC. At least so far my old knowledge tests out as accurate.

Jim

In sewing machines with high speed motors 220V,50Hz how do they reduce speed.

They start by using motors that are not all that high in speed, coupled to mechanisms that are not all that low in speed.

Motor nameplate-HARA,90W,7000rpm,220V,50/60Hz,0.45A,Fenner V belt 3R38 6x375mm (rotating handwheel)

that almost has to be a 220V DC (not AC) motor, panaban. Let me know, I bet you find diodes somewhere near the motor, probably in the little metal box leading from the wall outlet.

I'm still looking for the reference to the OP saying that he wants 12 VAC????

Why?

Speed up gear trains (think clocks) have to be specially designed because friction on the output multiplies on the input, whereas in step down gearboxes friction on the output is reduced on the input. Step down gear boxes can be designed with fewer parts (e.g. worm and gear) without worrying about efficiency, but are not usable in the reverse direction.

I have a calibre 12 volt 12" radiator fan that has a maximum current of 8 amps. However I don't think it is a permanent magnet type as tested be putting metal next to it.

You say that most are permanent magnet types. Could you suggest a few brands that have a permanent magnet? The calibre fan runs at a very high speed and perhaps other radiator fans do also and I wouldn't be able to get enough speed from the fan using wind to generate any appreciable voltage and current. I would have to use gears.

Probably easier to get a surplus stepper motor I was told that they make good generators.I sold 10 or 11 of them for that purpose with no complaints. I believe they have to be Permanent Magnet Motors.

30 watts from a small domestic fan?

Don't hold your breath. It would take gale force winds!

read the article properly GW. I will use gears at the input so that the much slower speed of the fan will be amplified at the output which is the motor of the small domestic fan.

For instance if the motor has a speed of 6000 rpm at 12 volts and a gear ratio of 60:1 then you only need 100 rpm from the fan that is driven by the wind. It is much easier to find motors that run at high rpms than ones that run at low rpms. I think they are there but they are also very expensive so you are better off using gears.

Why is GW better off? I thought you were building it, not GW.

Confused of Nouvions.

google "available power from wind turbine equation"

fans are not good blades for a wind generator.

http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCYQFjAA&url=http%3A%2F%2Fwww.raeng.org.uk%2Fpublications%2Fother%2F23-wind-turbine&ei=t8qmVMiiGYGzoQS654L4Aw&usg=AFQjCNEE5N2BBqtQKuUhl5YJitE7ZIbnLA

I estimate with a .5m small fan with an optimistic max conversion efficiency of 10% you will need around 60km/hr wind. Gear boxes will also bite into your efficiency, in your sizes they are probably only 80% efficient.

Have a good day.

No Andy Germany there are no brushes in the dc motor I have. It is a permanent magnet type and brushless. I haven't seen a brush motor for ages. I thought they were terrible motors and the brushes wore out too fast and then were difficult to replace. I think they are pretty well antiques now aren't they?

I like your suggestion for using a car alternator. I thought previously they were out of the question as a generator because there is no permanent magnet. But your suggestion of replacing the rotor coils with a permanent magnet sounds good to me. I will certainly try it but I can't use the videos on YouTube because my downloads from my satellite connection are too slow and I still prefer text and plenty of good diagrams. Any suggestions on how to do this from another source as it does sound difficult to do.

Thanks again for the suggestion.

An automotive alternator is a good idea for a couple reasons. The older larger one with more iron like the old chrysler units have high quality enough to produce higher voltages, but a caution when raising the voltage, the core saturation must be watched. As the rpm and base frequency within the alternator increases the saturation goes down. Don't get rid of the electrically energized field winding, use it to your advantage. You will have to obtain a regulator that has capabilities to regulate volts per hertz. This will give you some things to google. The old Chrysler units are dirt cheap at pic-a-part type junk yards and are used on many wind generators. They actually put out a 3 phase voltage which rectifies well, but you will need to use an external rectifier if you regulate above 12 volts nominal. Some of the newer GM alternators are 3 phase also but are more expensive.

The other choice is many of the motor used on excersize machines. These are permanent magnet and most do not have worm gear drives. These can be had relatively cheaply also as other items on the machines wear out faster than the motors, particularly the human exercizer.

Look for such infos yourself, but finding the right sized round magnet may be the biggest problem.

It needs to fit where the rotor coils were and touch the top and bottom "fingers", but keeping the fingers apart at the approximately same distance they were with the original coils. This is important!!

Get a friend to download the YouTube videos and burn them on a CD/DVD maybe?

One idea that you may have overlooked: (1) remove gears completely from your motor - as previously stated large gear ratios esp. with worm drive do not drive in reverse well at all. (2) install a very small radius hub with sticky wheel on it at the motor shaft, (3) install a large radius wheel on the fan hub, (4) build a small frame to hold the motor shaft wheel against the fan shaft wheel. If the radii are in a 60:1 ratio your should have all the speed to you need to drive the new generator. Hope this works out for you.

Putting a fan blade on a gear motor combo even with the correct type of gears and an easy reduction, there is too much drag / friction in the gearbox to actually be efficient unless it was being turned by a very high force wind.

I tried that experiment when I was a very young boy, trying to power my toys with a fan blade connected to a small DC motor. The only way I got any voltage / power from the motor generator, was to hold it in front of a portable house fan or use my dads air compressor to spin the generator. Not a very good trade off using 120 VAC to try to power a 6 VDC toy car.

For wind to be efficient, you need a large blade that will catch the wind or use the "Squirrel Cage" type. I think Jay Leno uses those on his shop. Here is a picture: