Fan Design / Bearing Information
Fan Design
Each 92mm, 7 blade fan use on Igloo is rated to spin at constant 1400 rpm. At this speed it can move over 21.18 cubic feet of air per minute and is rated at ultra low 15.2 decibels
What is interesting is the fact that GlacialTech opted for a 4 pin fan connector. I find this curious as this is a constant speed fan that can not take advantage of either PWM or Voltage changes. The easiest and likeliest answer is that it was cheaper for GlacialTech to spec one connector for both the “PWM” and “Silent” models of the Igloo. In any case, if your motherboard does not support 4 pin headers (such as older 939 systems) it does not matter. Let the extra pin “hang over” the edge, as it is not like that 4th pin actually does anything.
As for construction, GlacialTech opted for “Superred” Cheng Home Elctronic Co. Ltd CHB9212ABS-A low profile fans. These fans are made from light black plastic with standard 92mm mounting holes and a full frame design. In a nutshell these fans look like a regular 92mm fan except they have a thinner profile and thus the fan blades have a shallower profile as well. This also means that unlike the stock cooler with its “frameless” design air can only be channeled in from above the fan. This has the potential for creating more air turbulence, and thus more noise. This is something that you most certainly do not want on a CPU cooler with the term “silent” in its name.
The 5750 uses standard 92mm x 20mm 1B1S bearing fans so if the fans included do not meet your needs or you want PWM fans that have a higher rpm (yet can idle even slower) it should be relatively simple and straightforward to replace them. Of course you will have to splice the two fans into one connector but that too is a fairly straightforward proposition.
Rather that rely on MTBF numbers, an easier and better way to get a “feel” for what the manufacturer thinks is the real length of time a product should last is too simply look at the length of warranty provided. The length of warranty has been calculated to be long enough so that customers feel secure in purchasing it BUT still short enough that it will be “out of warranty” when most fail. Taken for what its worth, GlacialTech’s Igloo 5750 comes with a 1 year warranty.
Bearing Information (The 1B1S Bearing Explained)
Before continuing I would like to explain exactly what 1B1S or “1 ball, 1 sleeve” really means, and why it is a less than optimal long term solution for a silent cooling solution.
As I am sure you are all aware a computer fan is nothing more than a regular old “axial fan” that has been with us long before electricity was discovered, just on a smaller scale. This type of fan relies on a spinning shaft with blades to force air past itself in a parallel orientation. The easiest way to think of how they work is to imagine the axle of you car. The axle transfers the energy of your “engine” to your wheels, which in turn spin and move the car. In this case the engine is magnets mounted on the axel and around it. Electricity causes the magnets to have the same N/S pole orientation (which reverses themselves very quickly, yet always in sync with each other) which in turn causes them to repel each other, this creates a spinning force which intern rotates the blades on the end of the axel.
As with any moving mechanical parts you need a way to reduce friction and keep the axel (or Rotor in our case) from seizing or even welding itself to the sides of the shaft. This is where bearings come in. For the sake of our discussion, lets us keep it simple and say that there really are only two main types of bearings: “Sleeved” and “ball bearing”. In both types of design the bearing surface is stationary and only the Rotor/axel spins.
Sleeved Bearing Design
In a sleeved bearing design the Rotor (or axel) is nearly literally surrounded by a sleeve of metal, and there is the potential for contact between the bearing and the Rotor for almost the entire circumference of the Rotor axel. This porous metal (almost always bronze) is impregnated with lubrication, and the space between the sleeve and the Rotor is also packed with lubrication. The rotation of the Rotor causes a thin film to quickly build up between it and the bearing; thus reducing metal to metal contact to almost zero for the entire length of the bearing. It is for this reason that sleeve bearings are extremely quite and stay quite almost up to the point of failure. Their noise is best described as low pitched hum (think of a muted bass guitar’s low note hum).
However, since there must be a small gap between the Rotor and the bearing surface the lubrication does have a tendency to outgas or evaporate under normal use. When the lubrication is gone so it the friction reducing effects of the bearing. This is when sleeves become very noisy very quickly, worse still is the fact that the majority of the lubrication has to be of an thin oil to achieve the goal of its design. Because it is thin oil and not a “grease” it does not last as long as a ball bearing design which relies on more “grease” based lubrications. Worse is the fact that it is not a feasible proposition to refill them as the Rotor and bearing are not an end user replaceable part. However, this design is a very durable design that is more shock resistant than ball bearing designs. This is due to the fact that there are no small delicate springs to be damaged. Anything that can damage the sleeve also causes catastrophic failure of the fan. Their biggest weakness is the fact that they should only be mounted w/ the Rotor in a horizontal orientation, any other orientation and gravity works against the principles of the thin oil layer, making lubrication (pardon the pun) spotty at best.
Double Ball Bearing Design
What the number preceding “ball bearing” refers too is not the number of balls but the number of “races” or rings of ball bearings a true ball bearing design has. In a true ball bearing design there is two of these rings of ball bearings working together to stabilize and reduce friction of the Rotor. One is on the “inner” or bottom edge of the Rotor and the other is on the “outer” or top edge of the Rotor. These races of ball bearings are the only two points of contact between the shaft of the fan and the Rotor. What this means is that while the bearing surface is smaller than that of a sleeved design, the amount of stress is greater. These two small points of contact are all that keep the Rotor from becoming unstable and slamming into the side of the shaft. Due to the inherent nature of the design ball bearings to produce more noise than sleeved bearings from the begging and they do get nosier as they age.
This is caused by the fact that it has multiple small spinning balls that are being held in place by tension, so you not only have the main bearing surface friction to deal with it also has to deal with the spring to ball friction as well. This additional friction causes additional noise. This of course is an oversimplification of the flaws of the ball bearing design. However, take my word for when I say that a sleeved bearing produces not only less noise, but the noise it does produce is not as noticeable or annoying as ball bearing noise (think high pitched electric guitar vs bass guitar).
Ball bearings not only produce more noise they are also a lot more delicate than their sleeved counterparts. This is because the springs and ball themselves are extremely small and have to be precisely in alignment for them to work. A ball bearing fan can receive shock that will not damage the exterior of the fan but will damage the bearing raceways.
Please do not get me wrong, ball bearings due have their positive aspects. The biggest of which is that can take higher temperatures, which would kill a sleeved bearing. This is mainly due to the fact that they are a sealed bearing meaning that they can have thicker lubricants that are more resistant to burn off. Add in a longer life expectancy, and the fact they are not as sensitive to mounting orientation and you do have the makings of a fairly nice fan design, albeit, a louder than necessary one.
1 Ball, 1 Sleeve Bearing Design
Recent innovations have made not only sleeved bearings more durable, but they also have made ball bearings quieter. Unfortunately the “1 ball, 1 sleeve” design is neither a new design nor an improvement over either of the others. In a nut shell this design seems as if it was designed by a committee. On paper it should have some of the added durability of a ball bearing design, and it should have some of the noise reducing properties of a sleeved design. However, the real world is not a paper world and in the real world that committee did get some things right and some things wrong. In the real world the 1b1s design does have a lifetime similar to a true 2 ball bearing design. They are also slightly more heat resistant (still below 70c) and shock resistant (depends on where the shock occurs…ball bearing “end” vs “sleeved” end). They are also less sensitive to orientation and are in fact just as good as a true ball bearing design in this area. However, in my opinion in the only area worth improving on is that of noise, here they not only got it wrong, they got it completely wrong. In this one important area, 1B1S’s are not only louder than sleeved, they can be even louder and even more whinny then 2 Ball Bearing designs and just like 2BB’s they get worse as they age (think badly tuned high note on a electric guitar vs. a classic Fender Stratocaster). Not exactly a great tradeoff in my opinion.
To understand what 1B1S is, one simply has to look at a diagram of it. It becomes quite clear that all the 1b1s design team did was to cut both a ball bearing shaft and a sleeved shaft in half and meld the two together. Literally, one surface area (usually the outer race way) is a ball bearing design and the other half is a bronze sleeved bearing. In the end, 1B1S’s do have their own pro’s and con’s but what on earth made GlacialTech decide on this design when they wanted to make a “silent” heatsink? It is certainly not playing to its strengths, and the only logical reason we could think of was the fact that 1B1S’s designed fans are cheaper than 2 ball bearing fans. This is one area where you should not cut corners, especially if you are trying to cater to a fanatical market niche like the “Silent PC” crowd!