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Author Topic: Home built fan aspirated radiation shield  (Read 153087 times)

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Offline Breitling

  • Luis
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  • NW Spain
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Home built fan aspirated radiation shield
« on: April 04, 2007, 10:44:12 PM »
Here is my translation. I apologize if it is not as good as it should be, mainly in technical terms. Hope you enjoy it.

It is no news to show another home made tray radiation shield, but this one was thought taking into account some important details. This is the way to get a shield working as it is intended to be. Let's see how to build it, surely some of you may want to make your own.

1.- You need 10 flower pot trays, 20 cm diameter. There's no need for them to be bigger, there will be enough room inside for the sensor. Surely you can get white plastic dishes to avoid the painting, but they use to be thinner than these one. The thicker the more efective shield it will be. Mark three points not too much close to the border, making an equilateral triangle between them. It is better to keep all trays joint together to make the drills, this way you will have a perfect alignment.




2.- You have to make the central cutting on 6 of them. You may want to make a little test to know the cutting extent: trays have to overlap a bit between them, this avoid the horizontal radiation ("A") tho reach the measuring chamber. Looking from below you have to determine the point you reach in direct vision ("B"). A bit far beyont that point you can make the cut ("C"). It is easy to make with a Dremel tool or similar.




3.- Trim with a sharp cutter.




4.- This is the finish we want: clean and smooth.




5.- Here you have the 10 finished trays. #1 is the lower one, with three threaded rods (30 cm) fitted with some nuts and washes. Tray #7 has a different cut, you will see why later. Trays #9 and #10 have another little rod.




6.- From a white painted aluminium tube you have to cut 29 spacers. It is important to make them all of exact length, will avoid later tray misalignments.




7.- Assembling is easy, all you have to do is to put spacer and tray, spacer and try....




8.- Detail of the measuring chamber.




9.- Trays #9 and #10 detail. The additional threaded rod allows you to mount a bracket for wall fitting.




10.- Finish the assembly with some more nuts and washes.




11.- Put the shelf bracket into position. Make sure it is long enough to go beyond the trays border. The assembly is strong, it will admit gale winds.




12.- Fully assembled radiation shield. All trays aligned, same gap between them. This is not only an aesthetic matter, you intend not to leave any gap or hole to radiation. It is worth to take some time on it.




13.- Detail of what you see on picture 2 diagram, and the clue for good results: you don't have to see the measuring chamber in any angle, so radiation can't reach it directly. If you take this care you don't have to build a more complicated design.




14.- Time to disassemble, there's more work to do inside. You have to do the sensor fittings from those pc plates surely you have anywhere. Put them paralell on tray #2.




15.- A small drill, nut and bolt is enough to fit them in place.




16.- Sensor on his final position. This is a WMII sensor but surely you can fit any other in a similar way.




17.- Note tha the sensor is horizontally and vertically centered on the measuring chamber, far from direct tray contact.




18.- Tray #7. The reason why it has a special cut: this is going to be a FARS. All you need is a solar 1 volt motor, a propeller and a 1 volt, 800 mA solar cell. You need to make a central hole for the motor shaft and two small drills for the fitting bolts.




19.- The motor fits upside down on top of #7 tray, propeller at the bottom. We want to aspirate, not blow. The motor is directly on the air flow, allowing a small cooling effect on summer. All possible hot parts have to be above the sensor and in the air flow.




20.- Below you can see the small fitting bolts. They have to be very short to avoid damage inside the motor. They thread direcly to motor case.




21.- Propeller on place. Take care to determine its position and motor polarity. It has to aspire air, not blow it.




22.- Tray #7 in place, Check for enough room between sensor and propeller.




23.- A running test. You can see the solar cell at right. Once finished it will fit on top of the radiation shield.




24.- Dusk sun which is "fuelling" the test in picture above. You need very little radiation to keep the motor working.




25.- Disassemble again, once you made all checks and fits needed. You need to fill the tray lips, water accumulation on them could distrort humidity readings. Make some down slope to get a better drainage.




26.- Lips once finished. Let the filler dry for a day.




27.- Painting job. Take your time to get a good finish. On plastic trays it is recommended to apply a first primer product, then some acryllic paint layers.




28.- The final result: a brilliant white radiation shield, ready to go outside.

« Last Edit: January 26, 2011, 09:34:18 PM by Breitling »

Offline carterlake

  • Tom Chaplin
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Re: Home built fan aspirated radiation shield
« Reply #1 on: April 05, 2007, 11:58:33 AM »
Very professional looking!

WD; Davis VP2 6153; Quickcam for Notebooks Pro; Boltek w/ Nexstorm; GRLevel3; Live NOAA radio

Offline mikeym

  • Posts: 1,117
  • Thornhurst, Pa USA
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Re: Home built fan aspirated radiation shield
« Reply #2 on: April 05, 2007, 01:12:32 PM »
Yes, very nicely done. The instructions are GREAT. Thanks

Cheers

 :D

MikeyM
http://mikeymsweather.com/

Another VERY Happy WD user
Shuttle XS36v4 8 GB RAM
Davis Vantage Pro 2 wireless w/ Davis solar sensor
Laser Snow Depth Sensor LR4/Fluke 414D working in WD thanks to Brian

Bashy

  • Guest
Re: Home built fan aspirated radiation shield
« Reply #3 on: August 19, 2007, 09:26:43 AM »
Hi Breitling

Thank you ever so much for your hard work and posting it here.
I am definitely going to attempt to make this, I am DIY illiterate but from your instructions
i feel i can confidently make a good bodge job of it ;)
I have a few questions at present, if i may? as i would like to get this near as damn it to yours :)

  • what is the diameter of the 4 threaded rods?
  • How long is the little threaded rod?
  • how big are the spacers, Diameter and length?
    (my saucers are 32cm diam x 5cm depth, spacers = 5cm or 4cm, i think 4cm?)
    (the 20cm saucers only have 3cm depth, that is not enough is it?
  • Does the tube have to be aluminium or can it be a white plastic tube?
  • Whats the diameter of the fan?
-
-
I have found this kit (basic, lower image) Is this motor too powerfull or OK?

I take it, once completed i will be able to locate this anywhere, i.e. it don't matter if in direct sunlight?
« Last Edit: August 19, 2007, 12:54:32 PM by Bashy »

Offline Breitling

  • Luis
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Re: Home built fan aspirated radiation shield
« Reply #4 on: August 21, 2007, 07:34:47 AM »
Hi Bashy....

Fell free to make any question about this shield building. I'll try to help you. Units in metric, sorry.

what is the diameter of the 4 threaded rods?

5 mm. diameter. The three main rods are 30 cm long. The small one is about 10 cm. long.

Quote
how big are the spacers, Diameter and length?
(my saucers are 32cm diam x 5cm depth, spacers = 5cm or 4cm, i think 4cm?)
(the 20cm saucers only have 3cm depth, that is not enough is it?

I have made the spacers from a 9 mm inner, 13 mm. outer diameter tube. Length is 21 mm. The key to make the shield work properly is what you see in pic #2. I think 3 or 3.5 cm are enough for 32 cm saucers.

Quote
Does the tube have to be aluminium or can it be a white plastic tube?

Plastic should work as well.

Quote
Whats the diameter of the fan?

The fan and solar motor is exactly the basic kit you've found from Maplin. It is pretty enough for this purpose. You dont need a strong current, just a tiny constant airflow. Tip: you'll have to seal a bit the solar cell.

Quote
I take it, once completed i will be able to locate this anywhere, i.e. it don't matter if in direct sunlight?

Yes, wherever you want. Mine is working side by side with another Davis shield at full sunlight. Readings are the same.

Bashy

  • Guest
Re: Home built fan aspirated radiation shield
« Reply #5 on: August 21, 2007, 03:33:37 PM »
Thank you Breitling for you most informative follow up for me, I will hopefull try it this weekend, shop stock permitting :)

Offline Phil Holmes

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  • Great Bealings, Suffolk, UK
    • Phil Holmes' website
Re: Home built fan aspirated radiation shield
« Reply #6 on: August 21, 2007, 04:45:50 PM »
I've been thinking about this, and wondering whether there isn't an easier way of doing this without all the cutting, filling and painting, and I've come up with this:

http://www.headcook.co.uk/kaiser-tinplate-loose-base-quiche-15cm-p-331.html

My first question would be whether anyone knows whether there would be a disadvantage of using silver metal as opposed to white plastic?  Otherwise, you could use these for the layers of the pagoda with no need to cut the centres out, and no need to fill the lips.

Whadya think?

Offline NorCal Dan

  • Dan - KJ6RGX
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Re: Home built fan aspirated radiation shield
« Reply #7 on: August 21, 2007, 06:38:48 PM »
Wouldn't the metal radiate heat?  I think the reason they use plastic and wood for the enclosures is to minimize the heat signature.

Offline niko

  • syzygy
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Re: Home built fan aspirated radiation shield
« Reply #8 on: August 21, 2007, 08:38:20 PM »
Yes, a thermally insulating material will minimise the heating of the inside. The other problem with those pie tins is that the sides look pretty much vertical, what you want is a sloping edge so that there is some clearance between layers.

Bashy

  • Guest
Re: Home built fan aspirated radiation shield
« Reply #9 on: August 24, 2007, 07:10:51 PM »
Just to keep you updated on my progress, in case you was wondering lol

I have bought:

1 x 1 meter x 6mm of threaded rod 1.00
12 x nuts and washers 0.56
10 x 27cm x 3mm saucers 4.50
1 x 2 meters of plastic tube 0.85
1 x large bracket 0.49
1 x Box of filler 1.69

I have actually started already, I have filled all the saucers, what a mess i got into and the saucers
as you can see :oops:



I have cut the rod into 3 x 30cm and 1 x 12cm (there was a bit spare lol)
I have cut the 29 3cm spacers but as the dimensions of the saucers have changed so might the spacers
i will await your confirmation on this one?




I have also had to paint the bracket as it was grey and i preferred white :)
I cannot do anymore tonight as i need to wait for the filler to set, So in the morning i will do the cuts on the
saucers, prep them and then paint them.

As for the fan, this will have to wait untill it turns up, although it will be ready to just put in.
I am looking forward to seeing the end product :)

Offline munrobaggins

  • Posts: 1,973
  • 38 mls NE Inverness UK
Re: Home built fan aspirated radiation shield
« Reply #10 on: August 24, 2007, 07:55:12 PM »
I'm impressed...Maybe I should make one myself for my WS2310 Hygro etc...mmm...you've got me thinking...particularly as I saw the solar/fan unit in Maplins the other day.. :roll: :roll: :wink: s'pose I'd better find the best source for the dishes..

Bashy

  • Guest
Re: Home built fan aspirated radiation shield
« Reply #11 on: August 24, 2007, 07:59:26 PM »
Wilkinson's (Wilkos) is the best source that i could find and i spent a whole night searching the net!!!

I have made 1 booboo so far, i forgot to drill the holes before i filled the lips #-o, so no i have made it a little
hard for myself, I will have to see what i can do after i have sanded it down :?

Offline Breitling

  • Luis
  • Posts: 1,192
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    • Meteo Aerolugo
Re: Home built fan aspirated radiation shield
« Reply #12 on: August 24, 2007, 08:43:54 PM »
I have cut the 29 3cm spacers but as the dimensions of the saucers have changed so might the spacers
i will await your confirmation on this one?

Don't worry. The problem arises if they are too big. In that case all you have to do is cut a bit more each one.

Keep us updated. Good work by now.

Bashy

  • Guest
Re: Home built fan aspirated radiation shield
« Reply #13 on: August 24, 2007, 08:47:35 PM »
Yeah, i spose the only way to find out is to set it up and see how it is :)

I am sure there will be an update tomoz all being well 8)

Bashy

  • Guest
Re: Home built fan aspirated radiation shield
« Reply #14 on: August 26, 2007, 06:24:01 PM »
Ok not so much an update but a pointer to anyone else wishing to give this a go....

When filling the lip, for gods sake use a flexible filler or use mastic, not silicon as this
will not bode well when painting.....

The reason for me mentioning this is due to the fact its taken me 2 days to fill, sand
and paint. I used a standard filler and every time it dried and i sanded them they cracked
or came away from the outer rim, i have filled and sanded 3 times now, 3rd time i used
the flexible filler, this was also a pain as i had already filled with standard stuff, I should
have started all over again.....

So, i have now managed to bodge job them and paint them, using 1 can of primer and 3
cans of white gloss, i had to fire the paint on thick and fruity to try to fill and cracks
that i could fill...actually it got to the stage where i kept saying to myself "that will do
there good enough
" and hoped that the paint will cover any discrepancies lol
boy was i wrong....

So to cap off, Make sure you use a decent flexible filler and get the sanding as smooth
as you can, will make for a nicer finish....I know i will have to do mine again in a years time lol :oops: