Lockridge Device - Peter Lindemann

[pault]

First stab at a Prony brake

Below are my early results with a Prony brake. It would be appreciated if someone checked my calculations.

Equipment:

brass shaft attached with set-screw, 0.870 inches in diameter -> 0.2278 feet in circumference

spring fishing scales 0-50lb, lowest reasonable reading 2lb (a 2lb 2oz weight deflects the scale by 2lbs)

leather laces from an old Docker shoe

rope and rope pulley to suspend the scales from the ceiling

oscilloscope to read pulses in msec (instead of tachometer) (2 pulses per rev)

efficiency calculations as per Peter's 1st motor DVD



Readings (volts in, amps in, pounds on scale, msec between adjacent pulses):

1. 12.10V 1.4A 2lb 35msec -> 52% efficiency

2. 12.62V 1.4A 2lb 35msec -> 50.6% efficiency

3. 24.18V 2.3A 2lb 16msec -> 34.7% efficiency

4. 24.10V 2.4A 2lb 17msec -> 31.3% efficiency

5. 36.12V 2.0A 2lb 8.8msec -> 48.5% efficiency

6. 35.98V 2.2A 2lb 8.5msec -> 46% efficiency


n.b. pulling the rig to 2lb caused the motor to slow down considerably, e.g. free run at 36V was 6.2msec, loaded was 8.5msec.

n.b. The fishing spring scales don't leave me very confident with the results. I might need to get better ones or use a different setup. I'm entering new territory, for me, with this - suggestions most welcome.

pt

[Matthew Jones]

Get a chain saw file and reshape the brush's. That might help.
I suspect mine might get a little black over time but there is no noticeable wear anywhere else. But then I haven't taken it apart. It runs fine so no reason too as of yet.
I made my first pony but it cooked the leather belt. I have not tried another since. I have flywheel but I have not had the time to set it up.
I have alot of work coming in at the moment, so I have to take advantage of the "Feast", cause tomorrow it might not be there.

I'll report what I get when I get chance to get it setup and run it all.

Matt

[Web000x]

Matt,

It definitely isn't making a connection between the power and recovery brushes so that can be ruled out as a source of arcing.

That first picture that I posted a couple of posts back showing my commutator damage was a result of a bad connection. There was still too much enamel on the magnet wire connected to a commutator slot. This was causing the inductive spike to discharge one full commutator slot too early so the spike never made it to the recovery brushes.

After I fixed that problem, I still had signs of pitting, but they were not as severe. It is still too much of a problem to ignore.

So you have absolutely no wear on your commutator using this setup?

If you are not seeing any signs of wear, I am thinking that it may be that my brushes are too new. They have not completely worn to the shape of the commutator. The edges on the arc of the brush are still slightly rounded.

How are your flywheel and prony brake coming along?

Dave

[woopy]

hi all

Thank's Penno

yes i think it can be usefull

and my 2 cents in this respect

YouTube - shorting coil test 1 .wmv

good luck at all

Laurent

[Matthew Jones]

3 commutator spots, usually breaks the connection just as it makes connection to the recovery. So there is just a little time off. If they both were making connection to each other your amp draw would go up to probably around 6 amps and you would see above input voltage coming out of your recovery side.

Matt

[Web000x]

Matt,

I figured out why my RPM's were so low and my amp draw so high. I had put the rotor in the wrong way. The 2 degree offset from the commutators had my motor working against the magnets for a brief moment. Now I am getting much better speeds and lower amp draw.

When your commutator breaks the power pulse connection, are your recovery brushes instantly making a connection?

OR

Do they still have the width of the groove between the commutator slots to travel before they make the connection?

I visually checked mine and checked with a multimeter. My commutator does not allow me to break the power pulse and instantly connect to the recovery brushes since there is one width space between commutator slots to overcome. I think this is why I am getting such bad pitting in my commutator. Although it is only for a split second, that transient just jumps out too quickly and is really doing a number on the copper.

I don't think that it is being caused by an arc between the power and recovery brushes. I used a 12 Volt lamp connected to the recovery instead of a battery and still got the pitting going on.

Please let me know how much commutator space you have between the "break and make" of the switch. Until then I'll just keep scratching my head.

Dave

[Matthew Jones]

Hey Matt,
Also, I attached a picture showing my rotor and the commutator section. The commutator section is burning up pretty badly and I only had it hooked up for about 2 minutes.
The recovery brushes don't seem to be spaced correctly without modifying it. Have you checked your commutator to see if the same "pitting" is happening?
Thanks for the help,
Dave

Mine is fine. You may want to unhook the third commutator slot. Since yours is new the recovery and the power brush's might be making a connection and you getting an ARC when they do.
The drawing based on My first good effort. I burnt it up though, something happened I can't remember. So I made another. A bifiliar 240 turns 24 awg with 2 diodes. Same spacing.
It runs alot better.

You may want to also try adding more turns to yours.
80 turns of 24 has 2 ohms of resistance. At 48 volt I would a surge of 24 amps.
80 turns of 23 has 1.6 ohms. At 48 volt you'll get surge of 30 amps.
So you can see 23 - 24 might make the difference in the.
I'm not going to calculate the step up voltage coming out the back of that thing but follows a similar pattern. Also draining the coils with current present which is probably whats happening leads to Inrush currents showing up on every rotation.

Cut one slot loose and see how it acts. Use 100 ft of wire which is 2 ohms and see how it acts. And get some fast diodes from Digikey or some one, Radio shack is over charging you.

Matt

[Web000x]

Alright I wrote it all. The schematic, the details of the parts, the brush wiring, and the motor outline.
You can cut and paste from below or get link here. Motor Details



Any questions or improvements let me know.

It not going to rain tomorrow so I'll be building something to test the the torque. So most likely I won't be around during the day, I'll be in the shop.

Enjoy
Matt

Hey Matt,

I ordered two of those Razor scooter motors that you have an abundance of. I just finished wiring it up today and took it for a test run.

I have wired it up exactly like you post in your diagram. I used 23 AWG instead of 24 and could only comfortably fit about 55 "z-pattern" turns. I remember a post back where you said that you had 240 + turns on yours. 23 AWG is not much bigger than 24 AWG. How did you fit all of that wire on there?

My motor draws about 2 amps at 48 volts. It doesn't spin very fast maybe 1000 RPMS. I'm using a 1N5404 diode which is a little sluggish but shouldn't account that much of the poor performance.

Also, I attached a picture showing my rotor and the commutator section. The commutator section is burning up pretty badly and I only had it hooked up for about 2 minutes.

The recovery brushes don't seem to be spaced correctly without modifying it. Have you checked your commutator to see if the same "pitting" is happening?

Thanks for the help,

Dave

[penno64]

Hi All,

I posted this in the BFW thread as well.

Are we barking up the wrong tree -

You guys should seriously have a look at this -

https://sites.google.com/site/altern...coils-circuits


Harti posted at OU -

FUELLESS CAR PROTOTYPE by ISMAEL MOTOR

FUELLESS CAR PROTOTYPE by ISMAEL MOTOR


Regards, Penno

[FRC]

Way to go Brian

I found an easy way to pulse charge batteries (desulfator) that plugs into the wall and I can adjust from 30ma to 7amps output.

I know this is off topic. But this sounds interesting. Could you elaborate ?

FRC

[n84dafun]

Way to go Brian

How much does your flywheel weigh?
If you could find a bigger diameter flywheel of the same weight as the one you have it would work even better, IMHO.

I haven't done much lately with this project, but will get back to it soon. I found an easy way to pulse charge batteries (desulfator) that plugs into the wall and I can adjust from 30ma to 7amps output.

Keep up the good work and keep us posted.

Mark

Thanks Mark,

The flywheel weighed in at 50 onces (3.2 lbs). I have other bigger flywheels I can try out and there's enough room and chain to fit a larger one. I'm trying this smaller flywheel first for safety reasons. I don't know the exact math but I guess a larger diameter flywheel stores energy better than a smaller diam fw of the same weight.

Brian

[Mark]

Way to go Brian

How much does your flywheel weigh?
If you could find a bigger diameter flywheel of the same weight as the one you have it would work even better, IMHO.

I haven't done much lately with this project, but will get back to it soon. I found an easy way to pulse charge batteries (desulfator) that plugs into the wall and I can adjust from 30ma to 7amps output.

Keep up the good work and keep us posted.

Mark

[n84dafun]

Is your flywheel a generator also?

Or, is one of the motors a generator and one a motor?

Tj

Tj,

The flywheel on the top of the photo is not a generator, just a flywheel made from a metal disc that is 4 inch in diam and 1/2 inch thick sandwiched between two grinding wheel of the same dimensions. The motor on the right is the modified pulse motor, and the left motor is the unmodified motor/generator.

-brian

[tjnlsn255]

Is your flywheel a generator also?

Or, is one of the motors a generator and one a motor?

I look forward to pictures of your finished project and tests....

I just got my first 280 watt scooter motor and am winding the coils for my generator.....

Is anyone working on a pulse system that is not a commutator for the motor?

Hopes and Dreams....

Tj

[n84dafun]

Got all the parts, including #25 chain and 13 teeth sprocket. The motor and generator sprocket is 11 teeth, so the flywheel will be spinning a little slower. Just need to put it all together and start testing.

-brian