Sactownog

6 volt starter turn over slow or fast?

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35 minutes ago, maok said:

 

The below is from this site - https://electronics.stackexchange.com/questions/39387/how-are-current-and-voltage-related-to-torque-and-speed-of-a-brushless-motor

 

In any motor, the basic principle is very simple:

  • rotational speed is proportional to voltage applied
  • torque is proportional to current pulled

A 100 volt motor is a motor that can take a maximum of 100 volts, and a 50 volt motor a maximum of 50 volts. Since the 100 volt motor can take more volts, if all else is equal, it can give you a higher maximum speed.

But the difference in voltage does not affect the torque. To get more torque to go up a hill, you need to supply your motor with more current. A motor that can take more current (and a battery and motor controller that can supply more current) will give you more torque to help you up the hill.

 

I stand corrected.  I'm a mechanical engineer, so don't believe in electricity.  Let me amend my statements to say that 6 volts will turn over an engine very nicely, IF all components are correct, with plenty of torque.  I honestly didn't know...thanks

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2 hours ago, Bloo said:

The starter will have to dissipate over twice the power as heat that it did on 6 volts. You will probably get away with it for a while, maybe not forever.  A 6 volt bulb burns really bright on 12v as well.....

 

The question that needs to be asked is "why is it so hard to start?"

 

2

 

So true, when I rebuild my 6v starter, I noticed the winding leads that are soldered to the armature, had melted....meaning they got hot at some point prior to my ownership...this can only happen by two reasons;

 

1) A direct short

2) A 12 volt generator/battery combination (I called a previous owner and he told me he used a 12v battery at one point, just to get it started a "couple" of times....)

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16 minutes ago, Surf City '38 said:

 

So true, when I rebuild my 6v starter, I noticed the winding leads that are soldered to the armature, had melted....meaning they got hot at some point prior to my ownership...this can only happen by two reasons;

 

1) A direct short

2) A 12 volt generator/battery combination (I called a previous owner and he told me he used a 12v battery at one point, just to get it started a "couple" of times....)

 

Its unlikely it was because a 12 volt battery was used a couple of times. I have been running my '28 Chrysler with a 12 volt battery for nearly  3 years (it was running with a 12 volt battery before I got it as well) and I start the engine more than most.

 

Its the current (amps) that produces the heat in combination with resistance and time, not the higher voltage. Remember, there is less amps going through your starter when powered by a 12 volt battery than a 6 volt battery.

 

The total 'power' (Power = Volts x AMPs ) used is approximately the same regardless if its powered by 6 volts or 12 volts.

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A BAD connection will cause the starter to heat as current flow through each winding has much longer duration than a starter which spins normally.

When I got the Confederate (in my avatar) the engine would barely turn over with a brand new battery.

I found a questionable connection in the hot cable terminal end which connects to the starter.

I removed it and verified it was a lousy connection.

I yanked out the cable from the terminal end, cleaned up things and soldered it.

Now the starter spins the engine as if there were no pistons in it.

Night and day!....... 👍

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5 hours ago, maok said:

Remember, there is less amps going through your starter when powered by a 12 volt battery than a 6 volt battery.

 

The total 'power' (Power = Volts x AMPs ) used is approximately the same regardless if its powered by 6 volts or 12 volts.

 

Lets say you have a 6v starter with .05 ohms resistance (while turning).

 

6volts / .05ohm = 120 amps  (Ohms law)

 

120 amps x 6 volts = 720 watts

 

Now, connect 12 volts to that starter

 

12 volts / .05 ohm = 240 amps (Ohms law)

 

240 amps x 12 volts = 2880 watts

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Yes Bloo you are correct ,2 x the voltage is 4 times the power and can it do a lot of damage to these starter motors , never a good thing to convert to 12 volt.My 6 volt systems after 40 years of service has never failed as long as the battery is charged of corse .

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18 hours ago, Sactownog said:

I have not changed to negative ground. it is still a positive ground system. 

now that I read all of the comments, I will add some grounds. my positive (negative or black wire) will go to Starter bolt on top where peddle engages starter, my negative goes to the top of the transmission behind shiffter. 

 

the other negative I will run from where the Starter bolts to the Bell housing to the frame somewhere. 

 

should I run another ground somewhere else?  

The threaded post on the starter is insulated from the starter case. The starter case is NOT insulated from the transmission, bell housing, engine, frame or body. So negative cable to the threaded post, positive cable to the starter case, transmission, bell housing, engine, frame or body.

 

If you touch your negative cable from your battery to any of these, the starter case, transmission, bell housing, engine, frame or body, you will get a spark or worse such as a burned wire if you are truly positive grounded.

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12 hours ago, Bloo said:

 

Lets say you have a 6v starter with .05 ohms resistance (while turning).

 

6volts / .05ohm = 120 amps  (Ohms law)

 

120 amps x 6 volts = 720 watts

 

Now, connect 12 volts to that starter

 

12 volts / .05 ohm = 240 amps (Ohms law)

 

240 amps x 12 volts = 2880 watts

 

And yet you need bigger cables with a 6 volt battery. How could this be Bloo?

 

Your use of Ohms laws is fine when the motor is not moving but when the motor moves it becomes a dynamic electrical circuit with back EMF affecting the circuit. So its complicated. Someone with a higher pay rate can explain it better than I can.

 

I used the power equation in my earlier post because its simple. The engine requires the same amount of power (actually its probably slightly more with the 12 volts because of the faster spin speed causing some more friction) to turn it over regardless of the battery voltage.

 

Regarding the heat generated, you have to take into account 'TIME', a starter motor only spins for a few seconds at the most, hence the reason why they don't have a cooling fan built-in, unlike an alternator/generators. With a reasonably tuned engine, starter motor does not get hot enough because it is only spinning for 2-3 seconds at a time. If you have a badly tuned engine then yes, heat will cause issues inside the starter motor, but this is regardless of the voltage, specially if the starter gets stuck in the flywheel gears.

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39 minutes ago, maok said:

 

And yet you need bigger cables with a 6 volt battery. How could this be Bloo?

 

You need the same amount of watts (power) to turn the engine over at a given speed. If you use a starter designed for 12 volts, you only need half the current, and therefore smaller wires.

 

 

 

Edited by Bloo (see edit history)
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An interesting experiment would be to place a DC clamp meter (on the amps setting) around the starter motor wire with 12 volts and 6 volts batteries.

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OK, so let me ask you this, my Ground goes from the top of the battery to the top of the transmission where the sifter is located. There are bolts that hold on the sifter cover to the transmission. that is where my ground was and is currently screwed onto. 

 

I have been told this is where the Ground wire belongs on my car. 

 

I have also been told that it would be a good idea to run multiple grounds from the frame to the engine up front. 

 

PLEASE TELL ME, is the current ground enough, and should I run a ground from engine to frame up front?  

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16 minutes ago, Sactownog said:

OK, so let me ask you this, my Ground goes from the top of the battery to the top of the transmission where the sifter is located. There are bolts that hold on the sifter cover to the transmission. that is where my ground was and is currently screwed onto. 

 

I have been told this is where the Ground wire belongs on my car. 

 

I have also been told that it would be a good idea to run multiple grounds from the frame to the engine up front. 

 

PLEASE TELL ME, is the current ground enough, and should I run a ground from engine to frame up front?  

This is the way it is on my '31 and it works great....notice the ground on the transmission.

1931 DH6 frame.jpg

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37 minutes ago, keiser31 said:

This is the way it is on my '31 and it works great....notice the ground on the transmission.

1931 DH6 frame.jpg

 

Same as my '28.

 

But the Firestones on my '28 don't have enough grip to drive sideways on walls....😁

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2 hours ago, Sactownog said:

 

PLEASE TELL ME, is the current ground enough, and should I run a ground from engine to frame up front?   

 

The current one (like Keiser's pic) is good enough for the starter. Those are the only heavy wires you need. The third heavy cable is only used on cars where the ground cable goes to the frame (not like yours).

 

The rest of the car does need to be grounded somehow, but if most or all of your lights and gauges work good it probably already is. It couldn't hurt to add one, but it wouldn't need to be a big wire like the battery cables. It might brighten things up a little, but wont make any difference on the starter. You have that covered.

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3 hours ago, maok said:

An interesting experiment would be to place a DC clamp meter (on the amps setting) around the starter motor wire with 12 volts and 6 volts batteries.

 

I could try it later, when I get home.

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2 hours ago, keiser31 said:

This is the way it is on my '31 and it works great....notice the ground on the transmission.

1931 DH6 frame.jpg

 

What are we looking at....please tell me this is a photo shot taken from the top looking down, and that the oil filled engine/trans/diff is not sitting on its side....

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I think it is on its side, but I expect there are no fluids in it yet. Maybe they didn't yet have cameras that worked looking down.

 

The Mitsubishi Trucks NZ Manager ordered a truck to be sent from the factory dry, for their clever display. The factory queried it several times before they sent a dry truck. They displayed it in Wellington upside down directly above another truck the same, with the punch line being something like "No matter which way you look at it, Mitsubishi trucks ......"

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Car:

1936 Pontiac Master Six, 208cid, 6cyl, 6.2:1

 

Battery 1: Pacific Power Group 1 6 Volt.

Cranking Voltage: 5.545 Volts

Cranking current: 170 Amps

Watts: 942.65

 

Battery 2: Optima Red Top Group 25 12 volt.

Cranking Voltage: 10.731

Cranking Current: 174 Amps

Watts: 1867.02

 

This car already cranks fast on 6 volts. On 12 volts, it sounds ridiculous.

 

J6XFpPt.jpg

 

X2ckdEh.jpg

Edited by Bloo (see edit history)
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the wire gauge I got for Positive and Negative on my 33 6volt is (1 Ga) wire. should I go get some larger wires made or will 1ga be large enough? 

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9 hours ago, Bloo said:

 

You need the same amount of watts (power) to turn the engine over at a given speed.

 

 

 

Thanks for doing the test Bloo, I don't have a 6 volt battery. I think your results to some degree confirms your statement above. I obviously did not correlate the higher speed to the high power transfer.

I guess we are trying to determine if the starter is being damaged

 

Now the questions are;

     1. Where does that extra power (wattage) go, spinning the starter and hence engine to a higher speed, or heat, or a combination of            both?

     2. And does it do damage to the starter?

 

 

 

 

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7 minutes ago, maok said:

 1. Where does that extra power (wattage) go, spinning the starter and hence engine to a higher speed, or heat, or a combination of            both?

 

I don't know. I think both. A stalled motor draws gobs of current, so I guess since the motor spins faster, it draws less current than the math suggests? The current was about the same, so the wire inside should be happy as long as the waste heat doesn't get out of hand.

 

13 minutes ago, maok said:

 2. And does it do damage to the starter?

 

I guess it could, but people have been getting away with using 6 volt starters on 12v conversions for years, and just being careful not to crank too long. It looks a lot less bad than I expected..

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Bloo, was your meter set to record maximum current draw? If so, I suspect that maximum would be at the start when the starter is being accelerated then the current would drop to a settled level. I guess when starting an engine the starter would only be operating at maximum current draw any way.

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No, I just let it stabilize and snapped the picture. Maximum current would be just for an instant I think until the starter began turning.

 

I was cranking the engine (with the ignition shut off so it wouldn't start), so I think the numbers are valid. There would be variations as each compression stroke passed, and that could be seen on a scope, but this probe is way too slow for a scope.

Edited by Bloo (see edit history)
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