TR2/3/3A TR3/4 Electric Fan Conversion

[deadair]

This topic has been touched on in other threads, but I'd like to focus on some specific questions.

Of those who have converted their TR3/4 to an electric fan:

* Which fan did you select and why?
* Did you go for a push or pull configuration?
* Did the fan solve your cooling problem?
* How many amps does your fan draw?
* Does your generator handle the draw, or did you have
to install an alternator?

 

[TR3driver]

* 12" Hayden (had to go check) - found one on sale for a price I could afford.
* Mounted as a puller
* Since my problem was that the mechanical fan was mangled and removed, the Hayden worked very well.
* Spec says 8.8 amps, measured @ 12.6 volts is closer to 8.0
* In the winter, the generator was inadequate for my purposes even without the fan; so I had already converted to an alternator on my 59 TR3A when I installed the fan.

The 57 TR3 still has a generator; which will just barely keep up with the headlights, etc. Adding 8 amps of draw would mean an 8 amp discharge, any time the fan was on at the same time as the headlights (and wipers or heater would add even more). But since the fan is rarely needed under normal conditions, I think it still might be possible to "get by" with just the generator; assuming you don't get caught in stop-and-go traffic at night for more than an hour or two.

 

[deadair]

Thanks Driver.

Anyone else?

 

[vivdownunder]

I too used a 12" electric fan, but as a pusher. It is virtually unseen behind the grille of the 3A, and cools all the available upper radiator area top to bottom. The mechanical fan came off.

The selected fan has thin blades which don't impede airflow to the radiator very much when not switched on. It runs automatically, but with an over ride switch.

Research indicated a thin blade pusher fan was more efficient than a puller.

I can sit idling in city traffic in 104F summer peak temperature without any overheating worries, other than with the driver !. But I have a fabricated scoop directing air up into the bottom of the radiator too.

The car still has a standard generator giving about 17 amps, and there have been no problems over 12 years running with low beams at night, and the electric fan pulling 8-9 amps. That said, I don't do very much night travel in the TR.

Viv.

 

[deadair]

Thanks Viv,

What brand fan do you use? Do you know how many amps it draws? Seems that the more powerful SPALs draw too many amps for our little generators and I'm now considering an alternator conversion. However, I'd rather not tug too hard on this thread.

 

[Simon TR4a]

Mine is also a Hayden, and mounted as a pusher. I have an oil cooler behind the radiator so it had to go in front. (I don't remember the diameter but I thought 14 inches, it may be 12.)
I turn it on when approaching a traffic congested area, it is not needed at all in normal driving. Current draw is not too bad even though I have an electric fuel pump as well, but I don't usually drive at night. Ammeter shows a slight discharge when the fan is running.

 

[vivdownunder]

Deadair, it's a Made in Japan unit sold as Davies-Craig brand in Australia. 12V - 2250RPM, but the sticker on the housing doesn't tell the amps. Best I know it draws around 9 amps on start up. I've wondered if having it as a pusher means the windage coming though the grille helps rotate the blades, thus lowering power consuption. Same pricipal as a farm windmill. When first kicking in, the ammeter drops about 1/4 of a segment, then returns to neutral when running. It's been trouble free, so I haven't put a multimeter on it.

Viv.

 

[deadair]

I've wondered if having it as a pusher means the windage coming though the grille helps rotate the blades, thus lowering power consuption. Same pricipal as a farm windmill.

That's an interesting theory. Seems plausible.

 

[prb51]

https://i216.photobucket.com/albums/cc138/prb51/DSC01289.jpg

Puller as I had to remove the fan for the R&P although I've used a pusher on the smallmouth prior and it worked fine.
Alternator...fan, halogens, spotlamps etc.
The car did not overheat with the original fan when moving, only at longish stops in 100+ heat ergo the pusher.
No problems with the puller and it only comes on when the car is at a running halt or under heacy load (mountains+heat)

 

[TR3driver]

That's an interesting theory. Seems plausible.

There's no doubt the fan blades turn from the air going through them, the motor will even generate a bit of voltage when cruising with the fan off. But if air is going through the radiator fast enough to spin the fan, you don't need the fan at all, so you're still wasting power running it, even if it's less power than it would draw with the car stopped.

The fan should only be needed when stopped, or moving slowly.

 

[deadair]

https://i216.photobucket.com/albums/cc138/prb51/DSC01289.jpg

Puller as I had to remove the fan for the R&P although I've used a pusher on the smallmouth prior and it worked fine.
Alternator...fan, halogens, spotlamps etc.
The car did not overheat with the original fan when moving, only at longish stops in 100+ heat ergo the pusher.
No problems with the puller and it only comes on when the car is at a running halt or under heacy load (mountains+heat)

Hi prb51,

Is that a SPAL? How many amps does it draw and did you do a generator conversion? I like your radiator! Can't wait to install my Wizard.

 

[prb51]

can't remember who made the fan and Im on the road presently...I've an alternator but it doesn't draw too much....I've shunted the amp gauge so it actually shows about 1/2 the actual usage and it's never reached 30 (60) with the fan, halogens, heater blower etc....

 

[deadair]

That's an interesting theory. Seems plausible.

There's no doubt the fan blades turn from the air going through them, the motor will even generate a bit of voltage when cruising with the fan off. But if air is going through the radiator fast enough to spin the fan, you don't need the fan at all, so you're still wasting power running it, even if it's less power than it would draw with the car stopped.

The fan should only be needed when stopped, or moving slowly.

That begs the question: Does a rear-mounted fan also spin at speed?

The answer is probably: Yes, but less so.

Which raises another question: Does a front-mounted fan cool better, regardless of the amp draw, at speed?

 

[TR3driver]

That begs the question: Does a rear-mounted fan also spin at speed?

The answer is probably: Yes, but less so.

Unless you are assuming that air escapes between the fan & radiator, seems to me they would be the same. Might even be more, as I believe the fan interferes with the "ram air" effect against the radiator core.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]

Which raises another question: Does a front-mounted fan cool better, regardless of the amp draw, at speed? [/QUOTE]Better than what? On the Stag, I found that a front mounted fan reduced cooling at speed, even when running; over nothing at all. But I only had it in front because there was no room behind, and went back to a mechanical fan ASAP so no further experiments.

 

[trfourtune]

I am sure that the auto makers have investigated this one to death. I would look at a corvette and see how it is done. Making 500+ hp requires an optimal cooling system design and will not be a compromise.

Ducting the fan is probably the biggest factor next to flow capacity. With tight ducting around the fan and radiator, you generate a better pressure differential wich increases flow across the rad. If the fan is in front of the rad, it should be ducted on both sides of the fan-a large area tapering, ducted to the fan then ducted to the rad. If the fan is behind the rad, you still want to duct air to the front of the rad and duct the rad to the fan.
It is a little easier to seal(IMHO) doing it this way (fan behind the rad).

I would like to say that you want to get the largest area in front of the rad ducted to the rad to get the most air forced across the rad. The other significant point i want to make is to get the air coming out of the rad, out of the engine bay. You need the air to flow out of the engine bay easily other wise you will not get flow because of air pressure in the engine bay. We want the engine bay to be a negative or lower pressure than the front of the radiator. Although additional ducts can help (IF in the right location), most of the outflow of air from the engine bay is UNDER the car. By restricting air flow under the car at the front of the car, you will create a better lower pressure behind the radiator which is what you want.

one thing that can help is sealing the top of the rad to the hood/bonnet and adding a flexible air deflector directly under the rad as wide as possible to help generate a low pressure area behind the rad. Basically, you are trying to stop air from flowing around the rad.

If you add vents, the correct place to have them is immediately behind the front wheels or immediatly behind the rad in the hood/bonnet. you do not want vents back near the windsheild, this is a higher pressure area. Opening up the inner fender wells helps air flow out through the fenders. there is a low pressure area at the front wheels.

Of course, most of this is moot when you are standing still at a red light (except the fan ducting).
LOL
Rob

 

[deadair]

Better than what?

The question concerned a comparison between the cooling abilities of a rear-mounted vs. front-mounted fan.

What I'm taking away from this discussion so far is that there isn't much difference. It's more important to focus on how the fan-assisted air is channeled through the radiator.

I would prefer to keep my stock fan to maintain the authenticity of the engine compartment. So, for me, a front-mounted fan is the preferred, if not the optimum, solution. On the other hand, if I have to install an alternator to drive the fan, then all bets are off and I might as well give up on authenticity and focus on functionality.

 

[prb51]

I had a front mountd fan with the stock set up for some years and it worked very well in Az 100 plus heat. I only used it when idling. It did not seem to disrupt airflow at speed as the enginre ran normal temp.
The plus side was tuning, I could idle indef with it on and run normal temp.
I do have a small mouth and that ducting is more efficient than the later intake so do what is necc to force feed the radiator.
I only changed that set up to install R&P so the stock fan had to go and I mounted a puller on my ally rad.

 

[deadair]

I finally got around to my TR3 project. So far, I've rebuilt the carbs, installed a new fuel pump, and installed a pulley conversion kit. Now I'm ready to install a Spal fan and new aluminum radiator. A few questions:

I noticed that the fan temperature probe fits perfectly into the back of my water pump housing, where that square-headed plug is installed. Is this an acceptable place for the probe?

I'm also looking for creative ideas on how to mount the fan to the radiator. The only places I feel safe drilling holes are in the top and bottom mount brackets. The only other alternative is some sort of clamping solution.

 

[vivdownunder]

On the TR3A, first I cut two pieces of 3/4" x 3/4" aluminium angle about 5" long.

These were pop rivetted vertically to each side of the radiator surround so the front of the angle was parallel to the front or the radiator. Height was centred on the fan motor.

Then I made up two "top hat" brackets from about 3/4" wide strip steel that went horizontally across the radiator, and fixed to the face of the angles with small metal threads. Everything was painted matte black.

The fan mounted to the top hat brackets, and wiring taken across to the bodywork using small cable ties.

This fixing allowed a pusher fan to be mounted without interfering with the radiator shroud.

I've seen thin bolts put through the radiator core, but wasn't happy with that type of mounting.

Viv.

 

[martx-5]

...

I'm also looking for creative ideas on how to mount the fan to the radiator. The only places I feel safe drilling holes are in the top and bottom mount brackets. The only other alternative is some sort of clamping solution.

I don't know which model Spal you have, but you can see how I mounted mine with their (Spal's) mounting kit in this thread.