Regarding the solution of tying up the fan with wire or putting a stick in the fan to get through the water, I don’t think either is going to work. Something is propelling that fan (such as a belt)and what ever that something is it is going to be very upset at a direct intervention to its function. The belt is going to get very hot from the friction. Why not temporarly remove the belt?
Melody’s Botswana Land Rover fan issue- program #727
Tom, Ray: Contrary to your mistaken
impression, people actually do listen to
your show! I didn’t really hear the final
solution you guys proposed to Melody for
the Fan / Radiator issue on her Land Rover.
Vehicles with “fording” packages,
especially the Rover, should have thought
of this potential issue. As you both know
fan blade / radiator clearances are
extremely close in order to maintain the
efficiency of the heat exchange ratio. You
guys are fully aware of the phenominum
of “axial displacement” that occurs in
pumps and fans upon start-up and as the
density of the fluid (liquid or gas)
increases. Water is denser than air, this
pulls the fan blade / shaft forward, toward
the radiator. This condition was covered in
great detail in your combined, Doctoral
Dissertation on Fluid Dynamics and the
Effects on Pump and Fan Design.
My suggestion for the problem is this:
Install a manually operated switch in the
positive wire to the fan and just shut the
fan off before fording the water area. Or,
(and as “cutting edge engineering” as Rover
alleges to be) install a simple float
switch in the fan circuit that would shut
the fan off when the water reached the
determined level. Plus there wouldn’t be
the possibility of leaving the
fan “switched off” like there would be with
a manual switch. Please feel free to use
this reply on the air, send to Melody and
her husband, and to forward to Rover as a
recommended design change.
I always take your recommendations with a
large glass of wine and a cigar. Any amount
of salt just wouldn’t be enough.
Thanks for the show— you guys are great!!!
Dave Schubert–aka Magneto
I would say to remove the engine driven fan all together and replace it with an electric fan mounted on the radiator. This would eliminate a fan being tied down, but would create the problem of an electrical fan being possibly shorted out by water.
Assuming an electrical fan. A floatswitch woudl be OK so long as you are moving relative to the water. If there is no water flow and no airflow, it may overheat.
So we need not only a float switch, but also a flow sensor, with directional capability and logics so as to reverse the direction of the fan depending on the relitive velocities of the Water/Radiator. You might be reversing or stopped with tail against a fast flowing current.
We also need to slow the fan down a bit and not have water sloshing all over the place. So a variable speed drive motor and controls are required.
Alternatively we could do as I saw on a VW bus, the air/oil cooler mounted up hight externally on the side of it, Given it has a snorkle, mount an aux rad up on the snorkle also.
Humvees have a high, horizontal rad do they not.