Home built fan aspirated radiation shield

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.

Very professional looking!

Yes, very nicely done. The instructions are GREAT. Thanks

Cheers

:smiley:

MikeyM

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 :wink:
I have a few questions at present, if i may? as i would like to get this near as damn it to yours :slight_smile:

  • what is the diameter of the 4 threaded rods?
  • How long is the little threaded rod?
    [li]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?[/li]
  • Does the tube have to be aluminium or can it be a white plastic tube?
    [li]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?

Hi Bashy…

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

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

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.

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

Plastic should work as well.

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.

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.

Thank you Breitling for you most informative follow up for me, I will hopefull try it this weekend, shop stock permitting :slight_smile:

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?

Wouldn’t the metal radiate heat? I think the reason they use plastic and wood for the enclosures is to minimize the heat signature.

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.

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

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…

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 :?

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.

Yeah, i spose the only way to find out is to set it up and see how it is :slight_smile:

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

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:

Hi peeps

After three days its finished (apart from the fan, will be added when it arrives)



I still think that when the fan arrives and i start to fit it, i may need to add another
saucer due to the height of my sensor, I also had to lay the sensor on its side due
to fitting issues but its in there with plenty of space around it. (WMR928NX sensor)

Also as the bottoms of my saucers are concaved and water would sit in there, i had
to find a quick way to fill it (i wanted to get it finished today) I used candle wax, I
heated it up in a tin on the gas hob, once melted to a consistency like water i just
poured it on the saucer bottom and let it cool, then finished off the paint that i had
left.

Ok granted it dont look the best but i thought that after 2 days of trying to fill the lips
i had best do something about the lid lol
As for the bracket its strong but thin, so the RS sways a little in a good wind, I may
stabilize it when i get round to actually sorting a more permanent spot for siting the
sensors.

An important note for anyone wishing to give this a go

Good preparation will improve the fitting of the parts and the end product.
I thought i did a good job on the preparation but when it came to painting i was so wrong.
Make sure you use a flexible filler, Sand (no less than 800 grit) all the saucers to a smooth
finish, I would highly recommend a flexi bond as the base coat, this helps the adhesion of
the primer (i forgot and when i caught 1 of the saucers it peeled a little)

I may even do it again next year and try to get it a little tidier next time lol

Thanks Breitling for idea and walk through that made it all possible :slight_smile:

Nice looking Bashy. Now time to check your temp data. Let us know.

Sorry for the late reply, i wanted to get an idea of what it was like…

Without the Fan (should be here Wednesday) it is reading about 3oc above
what it actually should be (this is only when the sun is out)…

I bought one of them garden thermometers, the one where it has a 2, a min and a max
with internal sliders (from wilkos). When the sun was gone yesterday evening i compared
readings and there was about 1oc on my OS, in other words the manual gauge
was reading 1oc below my unit. I dont know if this is out or my unit is out.

I have an ornament from Fuerteventura with a thermometer on it, i will take that out now
and see what they all say in an hour or so…

I will be back…

Hi,
Don’t think you can compare a thermometer from Wilkos with your OS one.
Have you thought about getting an additional OS thermometer sensor?
That’s probably the best way to test. :slight_smile:

Hi Clanger

I have 4 temp gauges out there at present, all in the shade away from any heat source.
I think the temp is pretty steady now, readings are:

Electrisave: 23.0oc Humidity 52%
OS internal: 21.7oc humidity 58%
Dolphin: 20.0.0oc
Wilkos: 19.0oc

Main sensor in the Radiation shield (without fan) no sun is 19.3oc humidity 58%

So the closest sensor is the Wilkos 1 lol