A Different Approach To "Electric" Fan

[Gary Lewis]

.... How much power does it take to turn the fan?

It takes -at minimum- that much to couple the fan to the shaft... on top of that.

I don't know about electro-viscous clutches, or if you were talking specifically about that type of clutch or if you were talking more generally.

But more generally, the power required to clutch in a load is usually much lower than the power to actually turn the load. It's still an adder to the whole system. As you say, turning a fan takes the power to turn the fan regardless of how (or whether) you clutch it. And if it's a clutch that requires power to operate you have to add that power requirement to the system (and the systemic losses to generate that electric power in the mechanical alternator).

But that clutching power isn't necessarily that high. Take the clutch between an engine and a manual transmission. The spring in that clutch doesn't need to be all that strong to transmit the torque of the engine. It's still small enough that you can compress it with your leg, and there's no way your leg can do what the engine is doing. And the wrap-spring clutches that my company makes take a flat amount of power to energize no matter what load they are being asked to transmit.

Again, I don't know electro-viscous clutches. I imagine that (unlike wrap-spring clutches) they do require more power to transmit more power. But they probably don't require as much power to operate as they are transmitting. It's an adder, but not a (more than) doubler of the required power.

The electric part of the electro-viscous clutch is just a valve to allow the silicon fluid into the clutch. That's the difference to a mechanical-viscous clutch where the bi-metal spring opens and closes the valve. So I'm thinking it isn't much power at all if that spring can do it. But I really don't know.

[ArdWrknTrk]

.... How much power does it take to turn the fan?

It takes -at minimum- that much to couple the fan to the shaft... on top of that.

I don't know about electro-viscous clutches, or if you were talking specifically about that type of clutch or if you were talking more generally.

But more generally, the power required to clutch in a load is usually much lower than the power to actually turn the load. It's still an adder to the whole system. As you say, turning a fan takes the power to turn the fan regardless of how (or whether) you clutch it. And if it's a clutch that requires power to operate you have to add that power requirement to the system (and the systemic losses to generate that electric power in the mechanical alternator).

But that clutching power isn't necessarily that high. Take the clutch between an engine and a manual transmission. The spring in that clutch doesn't need to be all that strong to transmit the torque of the engine. It's still small enough that you can compress it with your leg, and there's no way your leg can do what the engine is doing. And the wrap-spring clutches that my company makes take a flat amount of power to energize no matter what load they are being asked to transmit.

Again, I don't know electro-viscous clutches. I imagine that (unlike wrap-spring clutches) they do require more power to transmit more power. But they probably don't require as much power to operate as they are transmitting. It's an adder, but not a (more than) doubler of the required power.

Electro vicious clutches don't have a mu, like a friction material

They're really not that far different than the fluid in a thermal clutch full of iron filings or something.

Typically

I'm not sure what this one is like

It might have a solenoid that just blocks rotation

At least then no energy is getting turned into heat.

All these things, add up to inefficiency in the system

Turning motion into electricity, electricity back into motion, the control system to switch that electricity on and off thousands of times a second...

You know, thermodynamics

[ArdWrknTrk]

Electro vicious clutches don't have a mu, like a friction material

They're really not that far different than the fluid in a thermal clutch full of iron filings or something.

Typically

I'm not sure what this one is like

It might have a solenoid that just blocks rotation

At least then no energy is getting turned into heat.

All these things, add up to inefficiency in the system

Turning motion into electricity, electricity back into motion, the control system to switch that electricity on and off thousands of times a second...

You know, thermodynamics

"Vicious". 🤣🤣🤣🤣

(Killers)

[ArdWrknTrk]

The electric part of the electro-viscous clutch is just a valve to allow the silicon fluid into the clutch. That's the difference to a mechanical-viscous clutch where the bi-metal spring opens and closes the valve. So I'm thinking it isn't much power at all if that spring can do it. But I really don't know.

Look at where else we have by bimetallic springs

Chokes, gauges, the old thermostat in your house.

Maybe a grandfather clock?

But in that case it's your key that distorts the spring.

Still stores a bunch of energy though.

With a thermal fan clutch, it's the heat pouring off the radiator that provides the energy to switch the fan on and off

It's a loss that's already built into the system, instead of something additional you're piling on

[85lebaront2]

Jim - It think it would "only" take 20 ft with the heft of that 460.

Bill - I agree that the longer-stroked 400 would probably have done the job if they'd put a bit of work into it. Like you said, a cam and a 4bbl would have made a huge difference, especially if they'd put a straight-up timing set in it. (I know you are going to tell us about their cheating and its consequences, so I set you up for that. )

As for the clearance on the radiator, I can't easily measure it the way you did but I do measure 2" between the front of the fan and the rear of the 4-core radiator on Big Blue. So if someone found an electro-viscous fan clutch that is less than 1" thicker than the mechanical-viscous clutches we are using then we could see if we could figure out how to adapt it. And have the EEC-V ECU's control it.

You can sorta see that 2" clearance here:

Gary, it wasn't so much cheating AKA VW as it was an almost impossible balancing act to get a Ford 400 to idle smoothly and meet the HC and CO standards. Idle screws would generally end up almost falling out to get one to idle right.

If I remember Ford fudged the results to get the 400 certified as the 390 was dropped after 1976 in trucks. If Ford had put an air pump on them, they probably would have run better in stock form. I do see some did.

[Gary Lewis]

Gary, it wasn't so much cheating AKA VW as it was an almost impossible balancing act to get a Ford 400 to idle smoothly and meet the HC and CO standards. Idle screws would generally end up almost falling out to get one to idle right.

If I remember Ford fudged the results to get the 400 certified as the 390 was dropped after 1976 in trucks. If Ford had put an air pump on them, they probably would have run better in stock form. I do see some did.

I wonder if the intake and head passages had something to do with the idle issues. Those passages are huge even on the 2V heads, which are shared with the 351C, and surely caused fuel to drop out of suspension at low RPM.

You may remember my story, but I had Windsor and Cleveland/M-Block 2V heads stacked side by side upstairs in the shop and Branden/Bruno2 came over to get the Windsor heads. He came down with the 2V heads and when I showed him the difference to the Windsors he was appalled at how small the passages are on the Windsors.

Knowing how the EFI lower plenum doesn't work well with a carb on a 460, I can imagine that the larger passages on the 400 wouldn't be conducive to idling and low-end power either.

[ArdWrknTrk]

[85lebaront2]

I wonder if the intake and head passages had something to do with the idle issues. Those passages are huge even on the 2V heads, which are shared with the 351C, and surely caused fuel to drop out of suspension at low RPM.

You may remember my story, but I had Windsor and Cleveland/M-Block 2V heads stacked side by side upstairs in the shop and Branden/Bruno2 came over to get the Windsor heads. He came down with the 2V heads and when I showed him the difference to the Windsors he was appalled at how small the passages are on the Windsors.

Knowing how the EFI lower plenum doesn't work well with a carb on a 460, I can imagine that the larger passages on the 400 wouldn't be conducive to idling and low-end power either.

Back in the early days of the Boss 302 program, Shelby-American was asked to work on the engine's performance. Shelby's engineers found that the ports on the Boss heads really started working around 10,900 rpm. They reduced the port area to 1/4 size, lost 2000 rpm off the top of the power band and added 5000 on the lower end.

We had a Ford parts manager in Hampton who ordered in a Boss 302 crate engine for his late model sportsman, running at our local 3/8 mile track. His was a Fairlane, everyone else was running Chevelles, so he was at a 48 cid disadvantage. all were running 5:38 rears. He had a "cross boss" intake with a single in-line top and an 850 cfm Autolite in-line carb. First thing I got him to do was go to a 6:14 rear, second I hand made some jets from smaller sizes he had in stock, from 0.110 to 0.130 in 0.005 increments. we went out Wednesday night for a practice session. Interesting experience hanging onto the roll cage as he went around the track.

Friday night, we're in the pits (my GT350 was rather noticeable). He qualified outside pole, race started and he almost spun out on the start the car had so much more power. If I remember the French car boys found a way to get the setup banned (standard Chevy policy, if you can't beat them, ban them).

[85lebaront2]

[Gary Lewis]

Back in the early days of the Boss 302 program, Shelby-American was asked to work on the engine's performance. Shelby's engineers found that the ports on the Boss heads really started working around 10,900 rpm. They reduced the port area to 1/4 size, lost 2000 rpm off the top of the power band and added 5000 on the lower end.

We had a Ford parts manager in Hampton who ordered in a Boss 302 crate engine for his late model sportsman, running at our local 3/8 mile track. His was a Fairlane, everyone else was running Chevelles, so he was at a 48 cid disadvantage. all were running 5:38 rears. He had a "cross boss" intake with a single in-line top and an 850 cfm Autolite in-line carb. First thing I got him to do was go to a 6:14 rear, second I hand made some jets from smaller sizes he had in stock, from 0.110 to 0.130 in 0.005 increments. we went out Wednesday night for a practice session. Interesting experience hanging onto the roll cage as he went around the track.

Friday night, we're in the pits (my GT350 was rather noticeable). He qualified outside pole, race started and he almost spun out on the start the car had so much more power. If I remember the French car boys found a way to get the setup banned (standard Chevy policy, if you can't beat them, ban them).

Right, the 4V heads had even larger passages than the 2V, and until the R's were way high you had nothing. But when you got it up there you'd better hang on!

Anyway, that's a neat remembrance. I'll bet it was fun!

I was playing with bow tie engines with W-shaped valve covers & a WCFB at the time. Didn't rev very high, but sure had torque. Rear gearing had to be about 3.08 given the tranny out of a Chevy 6 with a low 1st gear, but it would roll.