Radiator Cooling Fans
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My advice is avoid kenlow etc and buy a quality fan from a company that publishes accurate specifications for their fans, T7 is a useful company to look up.
On Friday, 29th August 1991, whilst travelling home to Canvey Island, Essex for the weekend, from RMCS – Royal Military College of Science, on the border of Oxfordshire & Wiltshire, the
Kenlowe electric cooling fan ceased to function. The fan warning light illuminated when activated by either the fan's thermostatic switch or the manual-override switch, but there was no perceptible whirring-fan noise, that would have been easily audible to me, even at motorway driving speeds.
By driving the car at reduced speed and turning on the car's heater with the booster-fan at maximum, I was able to avoid the engine overheating, but the temperature gauge reading remained high. Had this been unsuccessful, I would have stopped en route, to refit the belt-driven cooling fan, which I kept in the boot as a back-up spare, along with various other items.
When I got home and investigated the problem over the weekend, I discovered that the problem lay with the fan-motor, whose carbon brushes had substantially worn down, but I did not have any spares readily to hand. Consequently, on Sunday, 11th August 1991, at a mileage of circa 85,367, I temporarily removed the electric fan and refitted the belt-driven fan, so that I could use the car to return to RMCS later that evening.
In several ways, the
Kenlowe fan motor appeared similar to the Smiths motor associated with the Toledo's factory-fitted booster-fan for the car’s heating & ventilation system. When I stripped down the motor to inspect the carbon brushes, I discovered that the whole brush-holder assembly, including the brown composite (Tufnell I think) base-board, to which the brush-holders are attached, was identical to that of the Smiths booster-fan. A few weeks later I was able salvage one of these from a Triumph Toledo and/or Dolomite at one of the local car breakers' yards. This enabled me to repair and refit the Kenlowe fan motor on Saturday, 31st August 1991, at a mileage of circa 85,918•5.
Noting that I had retro-fitted the
Kenlowe fan to the car at a mileage of circa 24,500 and later suffered fan-motor failure at a mileage of circa 85,367, indicates that the
Kenlowe fan installation had failed after slightly more than 60,000 miles of driving; suggesting that it would probably be wise to acquire a few more spare Smiths brush-holder assemblies, for future replacement during the life of the car, which I did at a later date when they became available.
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Manufacturers tend to specify fan-characteristics under free-air conditions, with no regard given to air-flow restrictions, either on the suction or discharge sides of the fan, so it’s difficult to predict how fans would perform in any given radiator-cooling application. Ideally one would experimentally investigate their performance using appropriate test rigs and instrumentation (something I did with HVAC systems at Haden Carrier’s Group Central Laboratories), but sadly I no longer have access to such facilities!
As a sponsored postgraduate engineering student at CIT – Cranfield during the early-1980s, I spent my vacations working in the Building Services Section, of Haden Carrier’s Group Central Laboratories, where I investigated the performance of a variety of appliances and sub-systems for heating, ventilation and air-conditioning. I was told of a book entitled “The Fan” [of which I have still yet to find a copy!
], which despite its then age, was said to still be regarded as the definitive work on the subject of fan design and performance.
Whilst I was teaching during 1992/93, in the Department of Engineering & Motor Vehicle Studies, at SEECAT – South East Essex College of Arts & Technology, I salvaged the following ancient tome, which was being disposed of, during a major clear-out of old reference books:
John L. Alden, MASME, “Design of Industrial Exhaust Systems For Dust and Fume Removal”, The Industrial Press, 2nd Edition, 1948
Chaper X – Axial Flow Fans, on Pages 199~210, examines the characteristics of axial-flow fans used in a variety of situations, some of which might be considered to be similar in principle to the use of axial-flow fans for automotive radiator cooling, whether it be like the Toledo’s & Dolomite’s factory-fitted, belt-driven fan or the after-market electric fans which are commonly retro-fitted to classic cars, in a bid to improve cooling efficiency in slow-moving congested traffic and avoid power-wasting over-cooling at other times.
The chapter examines three basic varieties of axial-flow fan, described as (a) propeller fan, (b) tubeaxial fan, and (c) vaneaxial fan, of which the first best describes the type of fan used in automotive radiator cooling applications. The description on Pages 199 & 200 reads [including my explanatory notes, prefixed by the abbreviation n.b.] as follows:
Propeller Fan
« The propeller fan consists of two or more blades mounted on a central shaft and revolving within a narrow mounting ring. Figure 102 is a schematic illustration of a typical propeller fan. These fans are usually designed to operate in the range from free delivery to about ½-inch water [n.b. inches water-gauge]. When driven at blade-tip speeds of from 12,000 to 16,000 f.p.m. [n.b. feet per minute] they are capable of operating against pressures of up to 1½ inches but at sacrifice of capacity and efficiency. Moreover, the noise level may become objectionable at these speeds. »
« Because of its pressure limitations, the propeller fan finds its principal application in general room ventilation when mounted in a side wall or roof monitor and discharging directly to the atmosphere. Frequently the arrangement of spray booths or welding booths is such that they can be exhausted to the open air through short and direct piping. »
« When this is possible the propeller fan may be the logical choice. Although there are few suitable applications for this type of fan where more than the simplest duct work is involved, it is without doubt the cheapest fan both in first cost and in power consumption when static pressure can be kept below ½-inch of water. »
Although probably still in common usage within the USA’s HVAC community, static and dynamic / velocity pressures [n.b. static pressure + dynamic / velocity pressure = stagnation / total pressure] expressed in inches of water or inches water-gauge, have largely been super ceded by kPa – kiloPascals.
A pressure of 1 Bar = 1 Atmosphere = 100 kPa, is the measure of standard atmospheric pressure at sea level and will support a column of water about 32 feet high, in the form of a Fortin barometer.
Recalling one's secondary-school science lessons, practical Fortin barometers for measuring atmospheric pressure in the laboratory, contain liquid-mercury rather than water, because mercury has a density (kg/m³) which is 13•6 times greater than that of water, so the approximately 760 mm high column of liquid mercury in the barometer, is 13•6 times shorter than a column of water would be. It was Toricelli, an Italian scientist, who first devised a practical, portable barometer using liquid-mercury, which led to his discovery that atmospheric pressure decreased with altitude.
To put this in perspective, the pressure (Pa = N/m²) exerted by a column of liquid, is equal to the product (i.e. multiplication) of liquid density (kg/m³), gravitational acceleration (9•81 m/s²) and liquid-column height (m). Given that the density of water is 1000 kg/m³ = 1 tonne/ m³ and 1 inch = 25•4 mm = 0•0254 m, then 1 inch water-gauge = 249 Pa = 0•249 kPa.
Hence in round numbers, ½-inch water-gauge = 125 Pa = 0•125 kPa and 1½-inch water-gauge = 375 Pa = 0•375 kPa
Recalling further that 1 Bar = 100 kPa = 14•7 psi, then 1-inch water-gauge = 0•0366 psi
These are small air pressures, for which one needs to use a micro-manometer, of which an incline gauge filled with a relatively low-density liquid like paraffin, is one example I commonly used in my HVAC work at Haden Carrier.
Pages 207, 208 & 209 of the book reads [including my explanatory notes, prefixed by the abbreviation n.b.] as follows:
Fan Characteristics
« The characteristic curves of Figure 110 are typical of axial flow fans. The pressure-volume curve shows how these relationships change as flow decreases from the condition of free delivery to that of no delivery. Starting at the free delivery point (the base line), the pressure rises as the volume decreases until what is known as the stalling point is reached. This is the point at which the flow lines begin to depart from the inlet side of the blade surface and is the region in which eddies and vortices begin to form. It corresponds to the stalling or “burbling” point of an aircraft wing whose angle of attack has been increased until a loss of lift occurs. »
« As might be expected, the region between the stalling point and the no-delivery point constitutes an undesirable operating zone. The stalling dip is a symptom of instability and the sudden rise of the noise level which accompanies it is an infallible sign of serious flow disturbance. It is evident the system characteristics must be matched with the fan characteristics lying to the right of the stalling point. It is this feature of axial flow fans which makes their application to systems of fluctuating characteristics somewhat more critical than the application of centrifugal fans [n.b. the Triumph Toledo’s & Dolomite’s heater-booster fan is a centrifugal fan]. »
« In Figure 111 are plotted the pressure-volume curves of four axial flow fans of different types [ n.b. four types in order of increasing static-pressure capability: (i) propeller fan, (ii) tubeaxial fan, (iii) 1-stage vaneaxial fan, and (iv) 2-stage vaneaxial fan] but of the same diameter and speed. The four performance curves are of the same basic shape although the stalling dip becomes more pronounced in the higher pressure fans. The parabolic lines representing system characteristics, intersect the pressure-volume lines of each fan at the design point or point of highest efficiency. »
This description of axial-flow fan operating characteristics, might not be very intelligible or sufficiently detailed for one to properly select an appropriate fan with any confidence, but it should demonstrate that there is a great deal more to fan selection, than simply comparing the maximum air-flow delivery rates (i.e. free delivery, volumetric flow rates) of any given fan, and that one ideally needs to know something about their pressure-volume characteristics and the static & dynamic pressure conditions in which they will be required to operate.
https://www.tcf.com/wp-content/uploads/ ... E-2000.pdf
https://pdhonline.com/courses/m213/m213content.pdf
https://www.axair-fans.co.uk/news/under ... -fan-laws/
https://www.axair-fans.co.uk/all-techni ... an-curves/
https://www.scy-fan.com/what-is-the-fan ... ics-curve/
I really must try to get my hands on a copy of that book entitled “The Fan” or a more up-to-date equivalent!
T7 Design in or near Exeter, have quite an extensive selection of nice looking radiator cooling fans, but they also seem rather expensive, not including the mounting hardware and other components.
T7 Design Ltd, Unit 4, Clyst Units, Cofton Road, Marsh Barton, Exeter, EX2 8QW, UK
Tel. +44 (0) 1392 423 390
Fax. +44 (0) 7595 975 777
E-mail:
info@t7design.co.uk
https://www.t7design.co.uk/
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Manufacturers tend to specify fan-characteristics under free-air conditions, with no regard given to air-flow restrictions, either on the suction or discharge sides of the fan, so it’s difficult to predict how fans would perform in any given radiator-cooling application. Ideally one would experimentally investigate their performance using appropriate test rigs and instrumentation (something I did with HVAC systems at Haden Carrier’s Group Central Laboratories), but sadly I no longer have access to such facilities!
In the technical specifications for the SPAL fans, T7 Design quote maximum air-flow rates, which as I had surmised, fundamentally refers to the air-flow rates that are obtainable under free-air conditions.
https://www.t7design.co.uk/products/rad ... -fans.html
SPAL Radiator Fan - 13.8" (350mm) Push VA08-AP71/LL-53S | £168.00 = £140.00 + VAT
https://www.t7design.co.uk/spal-radiato ... l-53s.html
SPAL Radiator Fan - 13.0" (330mm) Pull VA13-AP70/LL-63A 1718cfm | £129.00 = £107.50 + VAT
https://www.t7design.co.uk/spal-radiato ... l-63a.html
SPAL Radiator Fan - 12" (305mm) Push VA10-AP70LL-61S 1292cfm | £120.00 = £100.00 + VAT
https://www.t7design.co.uk/spal-radiato ... l-61s.html
Surprisingly, whilst researching SPAL radiator cooling fans, I also stumbled upon electrical engine-coolant pre-heaters made by Calix, which also featured on the website of T7 Design in or near Exeter.
https://www.t7design.co.uk/
https://www.t7design.co.uk/engine-heating.html
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A word about airflow and possible stalling fans. There is a design flaw in nearly every water cooled car that trumps every best effort by manufacturers (or US) at providing good airflow through the engine bay. That being the fact that there is a vertical bulkhead behind the engine that, along with closed bonnet above and solid flitches to either side, effectively acts like a cul de sac, stopping the airflow through the engine bay dead in it's tracks. In our configuration with the rad at the front of the car, it's almost inevitable.
The ONLY exceptions I can think of are the BMC mini, 1100, 1300, Maxi and 1800 where air comes into the engine bay through the grille, hits the bulkhead and o/s flitch and bonnet (and engine) and gets an exit by passing through the rad and out though a convenient vent in the N/S flitch. This is a LOT more efficient, the air is not heated by the rad until it's almost out of the bay and the engine has COLD air direct from the grille passing over it rather than hot air already heated by the radiator, inspired work from Issigonis. This system actually uses the pressure build up in the engine bay to it's advantage, because of this, these cars need relatively smaller radiators.
Short of relocating the rad in a similar fashion, which might be very tricky, I recommend a decent batch of louvres at the rear of the bonnet, it gives all that pressure somewhere to go whilst driving and allows the built up hot air under the bonnet to dissipate harmlessly upwards when stationary in traffic. A couple of beneficial side effect of louvres are that the carburettor(s) stay cooler, less chance of fuel vaporisation with ethanol added fuels and the windscreen clears quicker on icy mornings from hot air being pushed up through the louvres onto the screen when driving.
Steve
I suspect that post-vintage, RWD car designers / stylists, hoped that warm air entering the engine bay, would exit via the transmission tunnel at the rear of the engine bay, beneath the bulkhead.
I recall that many vintage cars, with two-piece, central, longitudinally-hinged bonnets, had louvred slots in the vertical sides of said bonnets, which I surmise served the purpose you describe. I am told that at least some relatively-modern, high-performance cars, also feature such louvres, in the horizontal, front-hinged or rear-hinged bonnets.
Not being a sheet-metal worker by either training or experience, I am unsure how one would cut & shape, either internal or external louvres, in an existing Toledo or Dolomite bonnet, but I suspect there might be a special tool designed for the purpose. One would need to locate these louvres, so that rain-water did not drain onto any vital electrical or ignition-system components.
It would be interesting to somehow measure, the air-flow rate into the engine bay of a Toledo or Dolomite, before and after the addition of louvres! I can think of various ways in which this might be done, if one had access to the appropriate facilities, which ideally would include an automotive wind-tunnel!
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The bottom short radiator brackets are different on a Toledo , they angle up towards the radiator.
When you say that the Toledo’s bottom radiator-brackets are different, do you mean they are different from those of the Dolomite 1300 or the Dolomite 1500 or both?