Fan Test (long post with many pics) (1 Viewer)

[Tools R Us]

I was concerned that the lack of the rad etc. would affect the accuracy of the results. Realizing the conditions are not optimized for each fan, the conditions are the same for all fans, so it should basically be apples to apples. My intention was just to see what fan put out the most air and hopefully provide the best cooling for the cruiser. What do you think?

Bill

Fans are optimized to a certain flow, being able to put out big flow numbers without restriction won't do any good for cooling the truck, so the data is useless? The fans job is to develop a negative pressure/vacuum in the shroud to pull air through the radiator, measuring the output of the fan may not tell much, because it's not taking into account air that's recirculating/leaking around the edges of the fan and through the clutch? Measuring the flow pulled from the front side and the vacuum pressure in the shroud would get better data?

The easiest way I see to do it is to put a piece of wood in front that is about two inch larger than the opening in all directions, attach it with about half an inch spacers so the air is pulled in around the edges and put a/some hole/s to use the airflow meter from the front. you may need to adjust the spacers/holes to approximate the airflow to what it is on the truck. Use the locked clutch so the rpm can be controlled.

If you do this I predict that the air flow will become more complicated, you will see backwards flow through the fan clutch and maybe around the edge of the ring shroud fan.

Fans eat air, the more you give them the more power it takes to drive them. The easiest way to test this is with a shop vac, put an amp meter on the power cord and a vacuum gauge on the input, run the vac without a hose, record the vacuum reading and amps, then restrict the flow, the airflow will fall, the vacuum will rise and the amps will fall, if you close the intake, the flow will be zero, the motor RPMs will race, the vacuum will be high and the amps will be the lowest! If you pulled the fan out of it's housing, giving unlimited air, the airflow reading would be the highest, almost no vacuum and the amp reading would be the highest.

This is why the shroud and "seals" are so important, controlling the air so the fan only sees what air is being used to cool the system, any extra air only costs power and overloads the clutch at the expense of cooling. The seal at the shroud, radiator to core support, hood to core support and the tin pan under the radiator all prevent air from recirculating.

The blade tip to shroud interaction is critical, on an nonringed (standard 80) fan the tips of the blades cause a radial airflow that blows against the parallel part of the shroud causing a high pressure turbulent seal between the fan and shroud, the most efficient design would have the parallel "stovepipe" portion of the shroud as long as the depth of the blades. If the blade is set too deep that flow will blow into the shroud and recirculate, if too shallow the flow will blow outside of the shroud, but will leak air back into the shroud. Both setups will produce big airflow numbers behind the fan and require lots of power, won't pull much air through the radiator!

I hope my feeble ramblings make some kind of sense!

 

[Tools R Us]

and the blue (aisin?) is a three speed - does this mean freewheel, low speed (what is the %? 50?), high speed (what is this %- 75% or 100%?) of input?

just what are the numbers, and at what temps do the various steps occur?



PS - I too wish you were my neighbor..... nice setup.

The blue hub Aisin appears to be linearly variable, the hotter it gets the stiffer it gets, no steps and is adjustable.

 

[SamB]

Awesome dude, loving your work

I'd be interested to know how the flow drops as you add things infront of the fan i.e, Rad, aircon, trans cooler, intercooler...

 

[Photoman]

A little more info. I tried testing the airflow on the outside (front of cruiser) as suggested. The airflow was still turbulent and was approx. ¼ that of the inside (motor side) about 7 inches from the fan. A couple of other interesting things. With the SC ringed fan, there was a negative airflow (air flowing to the front of the cruiser) between the ring and the shroud. The air flow at this same gap stayed positive (back to the motor) with the stock fan. Also, on the motor side of the stock fan at the fan edge there was zero airflow. The pics show these more graphically. Weird stuff.

SamB - I will stick the rad and an intercooler in front to test when I get the tach to check RPM's.
Been through Wellington to Picton IIRC. Spectacular country. Spent five weeks there photographing.

Bill

 

[alia176]

Fans eat air, the more you give them the more power it takes to drive them. The easiest way to test this is with a shop vac, put an amp meter on the power cord and a vacuum gauge on the input, run the vac without a hose, record the vacuum reading and amps, then restrict the flow, the airflow will fall, the vacuum will rise and the amps will fall, if you close the intake, the flow will be zero, the motor RPMs will race, the vacuum will be high and the amps will be the lowest! If you pulled the fan out of it's housing, giving unlimited air, the airflow reading would be the highest, almost no vacuum and the amp reading would be the highest.

An excellent point Kevin. In my business, we operate 30-1000 hp blowers and we do the same thing you mentioned. We have huge louvers, that are closed upon startup. Otherwise, trying to start these monster blowers (fans) while trying to move air will result in an overload condition and trip the motor drives.

Now, back to your regularly scheduled program!

Ali

 

[SamB]

SamB - I will stick the rad and an intercooler in front to test when I get the tach to check RPM's.
Been through Wellington to Picton IIRC. Spectacular country. Spent five weeks there photographing.

Yes Wellington to Picton via the Cook Straight Ferry and the Marlbough Sounds!

OT, We took my HDJ81 for it's first off road trip on Saturday around the south coast road that runs next to Cook Straight - spectacular views of the South Island

P.S the factory lockers made a huge difference in places, very pleased to have them

 

[e9999]

nice job.
The jet behind a fan is normally smaller in diameter than the OD of the blades, so it's not that surprising that you'd get essentially zero at the edge. It's bigger before the propeller so the speed there is less.

Without all the extra hardware, the absolute numbers don't mean much but you could compare the effectiveness of different fins at the same rpm.

always great to read your posts!


(see the discussion in one of my recent threads on fan clutch for some numbers and some stuff on the whoosh and why it is likely caused by fluid relocation.)