WVD EMD 52" Q-Fan + Dynamic Brake Fans

[Wutter]

WVD is proud to announce a new product to our lineup of etched parts!

For the longest time we've been waiting for a re-release of the Atlas Q-Fans, so we set out to design our own from scratch, but we thought why not make a more accurate product while we're at it. Special thanks to @kondor for this design.

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You might be asking, why do these frets have 12 blades? The prototype Q-Fan has 12 mounting locations on its hub for blades but the fan motor is only powerful enough to spin up to 9 blades. Railroads use a variety of different blade configurations, which this etching allows you to do. There are some prototype pictures in the instruction manual attached, but it is best to find pictures of your prototype for blade configuration specifics.

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You can remove the blades you don’t want by bending them up and down until they break off, and then slightly angle the blades that you are keeping to give the fan blades some depth. The outer diameter of the fan blades may need to be trimmed slightly, depending on how thin the fan housings were bored out. The thinner the fan housings, the better the fan grills will look on top of the thin wall.

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The full instruction manual of how to assemble these can be found here:
https://tinyurl.com/p34n9ebb

The listing is now live on eBay and can be found here:
https://www.ebay.com/itm/255087271824

And finally some finished pilot models of these fans installed:

Conrail SD70MAC
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Conrail SD80MAC

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[Ed Kapuscinski]

That's hot.

[jpwisc]

Brilliant! A well needed product!

[Angus Shops]

Just curious, but wouldn’t a fan with an unequal distribution of fan blades be unbalanced and vibrate viciously?

[Wutter]

Just curious, but wouldn’t a fan with an unequal distribution of fan blades be unbalanced and vibrate viciously?

I'm not sure to be honest, but I would guess maybe that the RPM the fans are spinning at are low enough that it doesn't affect operation? From my research it seems like these fans operate at speeds under 1800rpm.

Most of the blade configurations are symmetrical, the only commonly used config that is not, is the 5 blade. I have not seen a 7 blade yet, but if you have pictures, please feel free to share! I watched a lot of hours of drone footage but was rarely able to get clean shots of blade configurations, so I would be happy to add any photos to the instruction manual as reference and give credit.

4 blade: (CEFX SD90MAC and CP SD70ACU rebuilds)
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5 blade: (NS SD70ACC, SP SD70M, UP SD70M)
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6 blade: I think these are actually 48" vs 52" but they are definitely Q-fan style with the motor hub mounted from the top plate) CSX SD50, UP SD60M
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8 blade: Can't find the CR SD70MAC picture for some reason, but I remember seeing this which is one of my pilot models I built up (also SCAX F59PH)
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9 blade: I know this picture is small and hard to tell but you can see that the blades are arranged in groupings of 3 (NS SD60E, NS SD70M)
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This is probably the best single drone video I've found so far, you'll see 4, 5 and 9 blade fans on these NS locomotives here:

[Lemosteam]

The manufacturer of the blades, in any blade configuration, would always balance on the blade's axis to prevent bearing failure, even if every blade were there and regardless of potential RPM.  Manufacturing and material variability necessitates it to prevent durability failures.

Brilliant design.

[GaryHinshaw]

Thank you for offering this @Wutter !  I've been waiting for Atlas to rerun these, but you have solved that problem and improved the product to boot.* 

RE balancing: it is indeed a clever arrangement that relies on the fact that sin(30°) = 1/2.  12 equally-spaced blades will be spaced by 30 degrees around the circle, like the hours on a clock face.  So 3 blades can be balanced by spacing them 120 degrees apart like an equilateral triangle.  The following balanced configurations are all possible (where the labelling refers to hours on a clock face):

12 blades: 12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
10 blades: 12, 1, 2, 4, 5, 6, 7, 8, 10, 11
9 blades: 12, 1, 3, 4, 5, 7, 8, 9, 11
8 blades: 12, 2, 3, 4, 6, 8, 9, 10
7 blades: 12, 1, 4, 5, 7, 8, 11
6 blades: 12, 2, 4, 6, 8, 10
5 blades: 12, 3, 4, 8, 9
4 blades: 12, 3, 6, 9
3 blades: 12, 4, 8
2 blades: 12, 6
0 blades:             

The only unbalanced configs are 1 and 11.

* If these do well, and if you ever need to do another run, might I suggest back-cutting some material from the base of each blade so that 1) it's easier to remove unused blades, and 2) easier to cant the remaining ones?

[Wutter]

5 blades: 12, 3, 4, 8, 9

* If these do well, and if you ever need to do another run, might I suggest back-cutting some material from the base of each blade so that 1) it's easier to remove unused blades, and 2) easier to cant the remaining ones?

I had really to wrap my head around how the 5 blades was balanced since it looks so weird, but I guess independently the center of mass of a 3 blade, and the 2 blade when combined, stays perfectly in the center axis of rotation.

I will definitely do another run if these sell out; regarding the concerns about undercutting the edge of each blade, it's actually really easy to break unused blades off ( bending 3-4 times up and down from +90° to -90° and they come right off) The material is 0.1mm 304SS, so it doesn't take much repeated metal fatigue to break them off cleanly, the ones I posted were done this way with no cutting of the full thickness material, and also no post process cleanup with a file or anything, they just break off cleanly. I think leaving the blades full width at the base also keeps them stronger when canting their angle, versus having a necked down area.