7mm diesel - working roof fan construction

[RobjUK]

Hi,

I'm working on a PRMRP 7mm brass Deltic model.

 

This came with etched brass "fans" for static mounting, which to me just do not really look the part. I'd like rotating fans, but ones that look reasonably in keeping with the prototype.

 

Searching on ebay, I found some 25mm fans with seven blades - not quite perfect, but the visual impression is good. Once I received them, the outer duct diameter was slightly smaller than the Deltic roof opening and did not look right; plus the roof curve meant they were a poor fit.

 

However, the whole blade and motor unit is only held in the outer frame by three thin mounded spokes, They can be cut at the motor hub to separate the motor and blade from the original frame.

 

I've 3D printed some simple ducts, 25.4mm internal diameter to match the roof cutouts and with a 50mm radius curve on the top to fit with the curve of the roof.

With the fans painted an appropriate shade of red, I think the impression is pretty good - though I also think need a finer mesh grid than the one supplied with the kit.

 

Hopefully these can be used with other 7mm locos that have (or should have) roof fans.

 

The fans are 5V, I intend to connect them in series pairs with a resistor to limit the speed to a sensible rate & power them from a function output on the decoder.

 

Photos, plus the .stl for the duct as an attachment. It should be possible to scale this if a slightly different size is needed for different locos.

The parts are only being held in place in the loco body for the photo, there is a lot of other work before it will be ready for them to be permanently installed.

 

FanShroud.stl

Edited April 6, 2019 by RobjUK
Typos

[RobjUK]

The last couple of photos; the overhead shot of the prototype is a screen grab from a youtube video by "ecksfilesbonyuk8".

Link to the fans I bought on ebay: https://www.ebay.co.uk/itm/Gdt-Lüfter-25mm-25x25x7mm-DC-5V-0-2A-Mini-PC-Computer-Cooling-Gehäuselüfter-Fan/322444596348