Lockridge Device - Peter Lindemann

[Matthew Jones]

ok so i decided to set and learn how to run a prony brake test running my motor in stock mode to get some output numbers to compare with for when i modify the winding.

below is a picture of the setup and a table of results, the first time i tried to run a prony test awhile ago i used delron plastic to make a wheel of known circumference when i tried the test the plastic got too hot and melted to the leather strap didnt know it untill i hit the power again the wheel didnt let go of the strap and it ripped my 50 Newton spring scale apart. ooops. so i moved on to other things.. this time i used 28lb scales used to weigh fish and a piece of thick aluminum tubing and epoxied a piece of delron in the core and trimmed this down to a 6inch circuference bored and tapped the center to use the threads on the shaft. it spins really nice, no flex if i reef on it up and down with my hand, you have to spin the moter very slowly to see there is a very slight wobble in the wheel. after running a few brake tests the wobble hasnt grown. unfortunately i reached 28amps on the last test so i needed a bigger gauge. the 0 to 100 gauge i have appears to be giving me readings that dont match up with my smaller gauge so i will have to find anouther gauge.

i am wondering is there a point where useing this leather strap method might be unwise (ie will leather stretching yeald bad results) should i switch to a different setup like shown here de Prony brake - Wikipedia, the free encyclopedia useing a wooden arm to pull on a spring scale?

Ya use a 1 foot piece of wood and 1 scale. Makes it real easy to calculate. Tighten it down till you get a certain RPM, then you can do your calculations.
Maybe use a scale that measures in fractions of a pound and up to multiple pounds.


Matt

[Eric]

ok so i decided to set and learn how to run a prony brake test running my motor in stock mode to get some output numbers to compare with for when i modify the winding.

below is a picture of the setup and a table of results, the first time i tried to run a prony test awhile ago i used delron plastic to make a wheel of known circumference when i tried the test the plastic got too hot and melted to the leather strap didnt know it untill i hit the power again the wheel didnt let go of the strap and it ripped my 50 Newton spring scale apart. ooops. so i moved on to other things.. this time i used 28lb scales used to weigh fish and a piece of thick aluminum tubing and epoxied a piece of delron in the core and trimmed this down to a 6inch circuference bored and tapped the center to use the threads on the shaft. it spins really nice, no flex if i reef on it up and down with my hand, you have to spin the moter very slowly to see there is a very slight wobble in the wheel. after running a few brake tests the wobble hasnt grown. unfortunately i reached 28amps on the last test so i needed a bigger gauge. the 0 to 100 gauge i have appears to be giving me readings that dont match up with my smaller gauge so i will have to find anouther gauge.

i am wondering is there a point where useing this leather strap method might be unwise (ie will leather stretching yeald bad results) should i switch to a different setup like shown here de Prony brake - Wikipedia, the free encyclopedia useing a wooden arm to pull on a spring scale?

[Robbush]

Mark,
Those might be a bit more difficult to work with as the first thing to to is pull all the wire off. I can say the motor I found came apart very easily, only two glue spots that broke off easily. I think you could wrap two slots next to each other and also bridge the commutator sections and that could work. Those are some big magnets in that motor.
Peace
rawbush

[Rl2003]

Here is a short video of that motor I have. It was easier that taking
a bunch of pictures. I think this will work well, as I could make the brushes
very narrow and the on time would be very short even at slower RPM's.
If you can see the commutators are long and narrow as well as the
brushes.

Mark

YouTube - VIDEO0016

[Rl2003]

You got a Ferrite/Ceramic magnet inside?
They don't saturate the iron in the case for one. You also have a condition in which one is canceling out the other. The flux that is traveling through the case is taking the shortest path to the opposite pole. That would be the surface of inside of the case down to the next magnet.

If for instance it was one magnet, you might see more magnetization around the perimeter of the magnet.

This is the same reason Bedini always uses Ceramics, they do not saturate the metal the point that the metal changes state, most of the time.

Matt

Yes Matt, They are ceramic. Thanks for the explaination.

Mark

[Matthew Jones]

You got a Ferrite/Ceramic magnet inside?
They don't saturate the iron in the case for one. You also have a condition in which one is canceling out the other. The flux that is traveling through the case is taking the shortest path to the opposite pole. That would be the surface of inside of the case down to the next magnet.

If for instance it was one magnet, you might see more magnetization around the perimeter of the magnet.

This is the same reason Bedini always uses Ceramics, they do not saturate the metal the point that the metal changes state, most of the time.

Matt

[Rl2003]

I have a puzzling question for all you thinkers. These have been boxed
up for almost 50 years in storage, and yet the motor case is not magnetized???
Nothing steel sticks to the out side of the case. It's steel or iron because a
magnet will stick to it, but with those big magnets inside, one would think
there sould be some magnetizum to the case??
Anyway just a side thought.

Mark P.

[Rl2003]

Just Two very large magnets. They are 4 inch's long and .625 thick. The ID of
the motor housing is 4.25 inch's. There is about a 1 inch gap on each side
between the magnets. It seems that there is a S and N facing in. The
cool thing is if I hold a 1" long neo (rod) magnet near the edge, as if you
where putting it into the motor case, I can twist the magnet around. If I put my
fingers with the magnet (tightly) into the middle of the case, it is very very hard to twist.
The field between the two magnets is very strong. Especially in the middle.
I will try to post some pictures tomorrow so you can see what I an trying to
describe.

Mark P.

[Robbush]

They should work, how many magnets are in the case?

[Mark]

Sounds like an awesome motor Mark P. Is it a permanant magnet motor and if so do you know how many magnets are in it?

[Rl2003]

Hello everyone,
I have followed this thead from the start, but have been busy
with John B's GT3 replication. But ever since I heard Peter L.
at the conference, I have had this hook in my lip. (Ive been caught by the bug,
for those who may not understand that.) I even bought what ever DVD
he had left there, and watched it on my long flight home.
I have these motors that where made by Honeywell back in the 60's.
1/2 HP 1200 RPM 12VDC PM motor. I believe the label says 42 amp.
I don't see a . in there (4.2??) and they have 28 commutator segments.
These where top dog motors back then, and some where re-wound to run
at 10VDC. They are a little bigger than a starter motor for a pick-up truck.
But they have a long SS shaft to connect a gen. or flywheel.
So my question is, will these work for what we are trying here??

Mark P.

[Robbush]

setup

Yes one coil is from slot 1 to slot 7, the second coil is from slot 4 to slot 10. It sounds like the commutation is right, it fires when the coil is in center of the two pole magnets. I plan on adding a degree wheel to the flywheel to record actual settings. Thanks for all the input.
rawbush

[pault]

The motor I am using was rated for 12volts and 9 amps continuous. It came from a coolant exchange machine. It has a 12 segment rotor and 2 magnetic poles. The slots in the rotor are centered with 12 commutator segments. The timing is set to pulse the coil when it is in center of the two poles, were should the rotor be when pulsed? Also I can only change rotation by flipping the run battery connection.
Peace rawbush

You have one coil, wound from slot #1 to #7, right? The run brushes should fire when slots #1 and #7 (containing the coil) are dead center of the magnets.

You must be sure that the armature is spinning in a direction such that the run brushes fire, then one commutator later, the recovery brushes engage. There is only one direction for which that happens.

Correct, the run brushes should completely disconnect before the recovery brushes connect (with as little time / distance between these events as possible).

pt

[n84dafun]

One Pulse per Rev - No diode in rotor

Here's an image of my write-up of my system. At 36V I was able to get around 6000 rpm at around 1 to 1.5 amps with 3 segments. The resistance of my zig-zag coil was around 1 ohm. I used my oscilloscope to estimate rpm's. I went back down to 2 segments as the write up indicates because my motor got hot after several minutes of running...maybe because I wasn't recovering the spikes through a battery, just left it open.

I did notice a slight decrease in speed when I shorted out the recovery leads. I thought the diodes prevented this slow down, maybe because I have the overlap of commutator between the run and recover brush.

I should be getting my second motor tomorrow (Mon). It's the same motor so I can compare the two.

The disadvantage between this setup and Matt and Mark's is that you have to move the brushes around. However, you don't need diodes in the rotor. I was running my previous setup with two diodes and was getting two pulses per rev, but it had a lot of vibration.

Caps on the recovery was above power supply voltage, about 40V with 36V power supply. This setup does not work with my variable power supply, only with my 7.5 Ah batteries.

BTW, when I used 1 segment between the brushes, the recovery voltage on the caps are usually below the supply. Maybe because the spikes aren't being captured in time when the disconnect and the reconnect time is even a fraction of a millisecond off. That's why I like the overlap and use two commutators segments.

-Brian

[pault]

some results

I installed a 10A panel meter (my mistake was using a fused multimeter, earlier) and got some more batteries.

At 12.54V, the ave current is 3.5A (analog meter), 4,285 RPM (calculated from 'scope trace).

At 25.5V, the ave current is 4.4A, 7,895 RPM. The -ve pulses on the recovery brushes are about -30V, 0.6-0.8 msec wide. There is certainly a big jolt of current at startup - the meter pinned itself for a moment, then settled back down.

@Matt - when you did voltage tests, did you load / slow the motor down or did you let it free run unloaded? I want to be sure that I'm testing correctly, before stepping up the voltage to 36V...

pt