Fuses for Circuit Protection

Indycars

Indycars

Administrator
Staff member

Since I'm considering installing a electric fan, I was concerned about my alternator
output. Which got me to thinking about rewiring the car and fuses and on and on
.....until my mind is just buzzing with new information.

I like most people would think that a fuse is fuse, they are all alike except for their
shape .....well, was I wrong. I found this thread on re-wiring a Chevelle and
this guy is really good. I read all 9 pages, but I'm only posting just one of his posts
about fuses. The rest you can read at the link below.

http://www.chevelles.com/forums/showthread.php?t=300744


OK now for some fan stuff, I'll get back to the distribution issue later. We
had to stop working on distribution as I had run into a fan and fuse issue.

The fuse issue is that the fan in my car, a 16 inch Spal, had been "blowing" fuses
every once in a while. They did not blow to the point that they were open they
were just a higher than normal resistance.

Fuses are rated by current and time. The relationship is I2t (current squared
multiplied by time).

Normal ATO fuses have an I2t of about 1500. Was the Spal stressing the fuse beyond
that point?

I decided to look at my car, Brian's car and a Flex a lite dual fan I had waiting to be
put in my car to replace the Spal. Here are the results.

We took the dual Derale Fan we put into Brian's car and removed one of the two
fans, big points for Derale as the fans are easily replaceable by just removing four
bolts. Very nice!

We discovered that Derale uses Bosch fans, well designed stuff.

Here is the current envelop of the Bosch fan when it starts off the battery, car is
not running.



125A peak current and when we check with the car running the start up current was
145A. This additional current is due to the higher system voltage when the alternator
is running and represents the normal operation of the fan.
The key point is that the I2t of the fan start up is 2,862, way beyond the ATO rating
of 1500. So in Brian's car the 30A ATO fuse on the 25A fan is being over stressed.

Next we compared the Bosch Derale against the Flex a lite, wouldn't buy the Flex a lite
folks (even though I did already).

It was more noisy than any of the others and pushed less air but it did draw less current.
I2t was fine for an ATO fuse.



Even the blade design is not as good as the Bosch or Spal.




Now we are to the single 16" Spal. It has performed really well for a number of years
now, but I don't believe it is enough to cope with real hot days and A/C whch is why
I was looking for a dual fan set up.



The I2t is beyond an ATO fuse also (just).

But none of these are beyond a 30A Maxi fuse, which has an I2t of 4070.

The lesson here is that the big fans our cars need should never be fused with
ATO fuses! Maxi fuses should be used.

I will post more about the fan design contribution to noise and the airflow issue
some time in the future. But first back to getting Brian's distribution right with
the correct fuses!

Ron
Click to expand...

To learn even more about fuses and HOW to use them to protect, check
out this link.

http://www.bcae1.com/fuses.htm
 

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We went through this exercise on Dorian's Supercharged TT.
CS-144 BE BEST.
I CAN BUILD A 1-WIRE OR CONVENTIONAL 200AMP.
USE A CIRCUIT BREAKER RICK.
4-GUAGE CHARGE WIRING MINIMUM.
 
Delco CS144 PUTS OUT 100AMPS EASY AT 2,000RPM ROTOR SPEED.
700 ENGINE RPM IDLE.
 
87vette81big said:
Delco CS144 PUTS OUT 100AMPS EASY AT 2,000RPM ROTOR SPEED.
700 ENGINE RPM IDLE.
Click to expand...

For my requirements it has to be same size or SMALLER in diameter than my 10 SI alternator.

I don't have A/C, radio, heater, windows, seats. Just lights, horn, gauges and MSD ready to run distributor and maybe a single 16" fan that draws less than 20 amps.

 
Indycars said:
87vette81big said:
Delco CS144 PUTS OUT 100AMPS EASY AT 2,000RPM ROTOR SPEED.
700 ENGINE RPM IDLE.
Click to expand...

For my requirements it has to be same size or SMALLER in diameter than my 10 SI alternator.

I don't have A/C, radio, heater, windows, seats. Just lights, horn, gauges and MSD ready to run distributor and maybe a single 16" fan that draws less than 20 amps.
Click to expand...

Give me tonight & tommarow to think about the bst alterbator to meet your Specs rick
 
Delco CS130 would work OK.
But I don't like them.
American made ball bearings no longer available for the.
Just China.
Putting all your faith on super cheep ball bearings.
I have had them faul on the 1987 Corvette Convertible.
Foynd Japebeese rear bearung. Been Ok
 
If you don't mind putting a little Ford back into the T-bucket.......
Ford 3G or 4G alternator may fit the bill nicely.
200Amps or close available.
About 10si size. 6inch frame.
Used one on a friends 1970 Macl 1 351 Cleveland Mustsng.
High Amp Flexlite electric fan used.

Have to research.
Your welcome to also Rick.
 

It also has to mount in the same place and still line up with my other pulleys. A small spacer behind the alternator where it contact the engine mount might be Ok.

My pulley ratio looks to be 2.2:1, if my idle speed is 850 RPM, then the rotor speed will be 1870 RPM. The output at idle will be the most critical for me for the cooling fan to have the greatest output. Alternator output at cruise will be much more than I need, it's cooling at idle that I'm most concerned about with only a 2500 CFM fan.

I still have to get the car on the ground and see what my oil pan to ground clearance is, that's going to effect everything I'm trying to decide on right now. For instance if the engine has to come up, then maybe I won't need a new alternator. OR taller tires might do it, so I would still need a better alternator. I just got my new spring shackles and spring pivots, so I should have some kind of idea tonight.



 

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Give me time to research for You Rick.
Long story short. They have taken all the good parts away & given us China junk.
I don't want to let you down with inferior junk.
Like me. Only best will do.
 
I like the Ford 3G Alternator as a possible upgrade for the T-bucket Rick.
I can build it as a 1-wire unit.
Use Premium parts & Ball bearings.
Ford Renegade 5.0 Racers use them.
Proven tough. They turn 8,000-9,500 RPM's through the traps.
Internal fan unit. Clean looks.
I think its a Delta wound stator design.
Up to 200amps charge current available.
125 amps idle charge current.
2,000 RPM Rotor speed.
Stock its an A circuit design.
GM is a B circuit.
1-wire conversion solves electrical compatibity issues.
 
Measure up a 3G this weekend. Compare to old Delco 10si your using now.
Get back to you Rick.

Brian
 
Is there any extra room on the T-bucket Rick for a slightly larger diameter Altetnator Rick.?
Two different 3G Alternator cases made.
Small case. And large case. Large case is the Potential high amp unit. Supply plenty of current at idle with cooling fan on. Headlights, MSD distibutor, ect.
Any room to move adjustable arm ?
 
The only way to get high charging amps at low engine idle speed is to use an Alternator with a large diameter rotor. Means bigger housing case.
High amp large case 3G like a Delco CS144 .
But even better low speed charge amps output.
Bigger rotor induces a much stronger Magnetic Flux lines across Stator assembly.
 

Now that I have found the perfect length V-Belt maybe some. I have to
put this belt on the water pump pulley and then slide it onto the water
pump shaft. It's somewhat tight then, so I don't need much adjustment.

But with a different alternator, that could all change I suppose. Can you
tell me how much bigger in diameter?

 
I have a few old 1970's 10SI alternators around the house.
I have to locate a used 3G large case alternator for You.
Should not be too hard. Find it Saturday morning.
Measure up. About 1987-91 Vintage. 5.0 Mustang & 460ci V8 full sizr e Ford truck.
I don't want to quote dimensions I found online.
Just looks larger than 10si by 1/2" or so.
 

Do you really think I need that much output to power my TBucket at idle ???

I just got the car on the ground and I only have 2-1/2 inches of oil pan to ground
clearance. So I might need to raise the engine slightly, which will reduce the space
available to adjust the alternator.



 

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The current pulley ratio of 2.2:1 and a Delco CS130 would be marginal charging output at idle in my experience.
They tend to run very hot all the time when loaded down.
Burn your hand 250-300 F hot..
Could use but may crap out premature.
Its not like we live 5 miles apart. Run you another alternator Or make on the spot repairs.

I figure a 3,000 cfm fan will use 40-50 amps current. Ignition 6 amps.
Electric fuel pump 8 amps.
Headlughts & taillughts 20 amps.
Guages 2-5 amps.
76- 86 amps possible load at night driving.



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