Heat transfer in divelight head

[patrickDM]

Hi all,

After using a commercial (modded) canister primary (Halogen) for many years, a I was thinking of re-using the battery-canister \\
and hook it up to a LED head ...

I got a ALU head with suitable dimensions from Alunatec, a 7XPG-R5 module, a MaxFlex6 driver, and a (prolonged signal)
Piezo to operate it.

Although I had some initial ideas to cool the LED array & driver using Aluminum profiles, non of these worked out (mechanically).
So, I'm in desperate need for some advice & new ideas on how to mate the LED/Driver support with the ALU housing (which
would provide the best cooling when submerged).
The inner-diameter of the housing is 50mm ...





Has anyone tackled a similar problem, and succeeded in getting appropriate cooling/heat
transfer to the external housing ?

Thanks & greetz

Patrick

[jspeybro]

If you have (access to) a lathe, you can turn a 50mm diameter piece of alluminium that nicely fits in this housing and has the right height. This has worked for me on a greenforce HID head.
If you don't have a lathe, you might be lucky that alluminium rods of 50mm fits nicely (here in europe, 50mm is a standard size). It will then be a matter of getting it flat and the right length and bore it out a bit on the backside to provide space for the driver.

[patrickDM]

Hi jspeybro,

Thanks for your suggestion ... Unfortunately I do not have access to a lathe, but
I can always look for a workshop ... Aren't there some practical issues though with
this approach ?... I.e. there's no easy way to adjust the height ... once the heat-sink
is pressed-in, it will be very hard to remove again (if possible at all) ... and for sure
some channels will need to be drilled to allow the wires through ... but that's only
a minor problem.

Thanks & greetz

Patrick

[Codiak]

Rather then press fit you could use jbweld, at least this way you could adjust it a bit.

Where are you located?

[little nick]

Hi jspeybro,

Thanks for your suggestion ... Unfortunately I do not have access to a lathe, but
I can always look for a workshop ... Aren't there some practical issues though with
this approach ?... I.e. there's no easy way to adjust the height ... once the heat-sink
is pressed-in, it will be very hard to remove again (if possible at all) ... and for sure
some channels will need to be drilled to allow the wires through ... but that's only
a minor problem.

Thanks & greetz

Patrick

Have a local machine shop turn something for you. You can calculate the length you need - so the optics fit in.
You don't want an interference fit - just a push fit so you can slide it out as required. I use the cable to push the heat sink out (does not damage any joints - as it has a strain relief joining the sink to the cable.

[patrickDM]

Ok, thanks for the help & suggestions ... I will contact some local shops & see what they can make.
I will post some pictures once complete.

Cheers

Patrick

[350xfire]

You could always thread the insert and the body and screw in the insert.

[patrickDM]

I guess that would work, although I'm not that sure if threading the inner of the 50mm dia housing would be very feasible ... it's
somewhat deep(er) inside the head.
I have a solution in my mind, I'll post some pictures if I find a CNC shop to make it ....

[Codiak]

I guess that would work, although I'm not that sure if threading the inner of the 50mm dia housing would be very feasible ... it's
somewhat deep(er) inside the head.
I have a solution in my mind, I'll post some pictures if I find a CNC shop to make it ....

If your US based and can't find a local shop ping me.

[patrickDM]

Ok, thanks for the heads-up ... I'm located in Belgium.

[Codiak]

Ok, thanks for the heads-up ... I'm located in Belgium.

Shipping time and cost would suck ;-)

[jspeybro]

Patrick, I live in Brussels :-) and have a small lathe, so I might be able to help you. If the inner diameter is really 50mm, I would need to go and get some alluminium though (I don't have a 55mm rod to start from at the moment). PM me if you are interested.

Johan

[Delphinus]

Will you use a colimator or reflector or that one is for video?

[betti154]

Hi jspeybro,

Thanks for your suggestion ... Unfortunately I do not have access to a lathe, but
I can always look for a workshop ... Aren't there some practical issues though with
this approach ?... I.e. there's no easy way to adjust the height ... once the heat-sink
is pressed-in, it will be very hard to remove again (if possible at all) ... and for sure
some channels will need to be drilled to allow the wires through ... but that's only
a minor problem.

Thanks & greetz

Patrick

It's low tech, but I've used excess cable pushed into the back I the housing through the gland to control where the heatsink fits. A snug slip fit is all you need with some thermal grease so don't worry about it getting stuck in. Worst case push it out from the back via the gland hole.

[betti154]

Where did you source the alunatec head from?

[Delphinus]

Sometimes Goolgle helps

http://www.alunatec-shop.de/

O bought one from him long time ago and they are simple but have good quality.

[betti154]

I did google first but nothing came up on iPhone.

Thanks for link.

[lucca brassi]

under DIY STORES ? maybe ?

[patrickDM]

Hi all ..

Sorry for not replying the questions earlier, and thanks for the offered help & tips ! ... somehow I stopped receiving mails notifying me about new entries
in this thread
Indeed, I got the head from Alunatec .. The quality seems pretty good (although I'm yet to take the housing under-water) ..
I also contacted them about a heatsink-solution I designed (basically, an expanding slug), and the parts are currently under way ... I'll post some pictures
once they arrive, and some follow-up for the completed head.

Cheers & thanks, Patrick.

[patrickDM]

Forgot to reply to Delphinus question ... I'll be using a Polymer Optics lens assembly, the 12degree version



I also have the Kathod 10 degree lens, but from what I've read in other threads, it seems the bundle is nowhere near that
figure (could well be the same for the Polymer Optics though).

Cheers Patrick

[DIWdiver]

I used the Polymer Optics lenses in my light. I was very disappointed in the beam quality - lots of rays and other irregularities. They aren't too bad when 6 of them are combined, but not at all what I expected. My next light will have an Ahorton aspheric.

[patrickDM]

Hi DIWdiver, thanks for the tip ...

I guess an aspherical lens would indeed be better, but in that case (i.e. with the alu-housing I'm using) I would need
to find one (or have one made ?) with a correct sized flat bevel ...
the bevel should also have a reasonable thicknesss (max intended diving depth 80-100m + safety factor).
Any ideas where to find such designs ?

Cheers

Patrick

[DIWdiver]

Actually, you need to put a flat plate in front of the aspheric, and that should be what is depth rated. The aspheric should not see pressure.

[patrickDM]

Ha, ok, understood ... for this particular head it won't be an option then ... with the designed-heatsink (hope to receive it later today) there's no
sufficient space to place the aspheric at the correct focal length.

[patrickDM]

Just a quick update on the heat-sink I designed ... The o-ring keeps the assembly together, and tightening the hex-bold increases the diameter of the slug, allowing
a (very) snug fit. Note that the heat-sink is still missing the mounting-threads for the led assembly & the holes for the supply-wires.

Cheers Patrick

[350xfire]

The bad thing about that is that you will have localized hot spots. The middle LED may fail since it may run hotter due to the hole below it. Also, because you have no really good contact with the wall of the head, the heatsink will eventually be saturated with heat that cannot escape.

Cool idea though.

[patrickDM]

Hi 350xfire ... thanks for your feedback ...

I'm indeed a bit worried about the hotspot in the center, but I'm still hoping the alu-pcb will be able to even this out a bit ....
the hex-nut is flush with the rest of the heatsink (at maximum diameter) so the non-covered area is pretty small ... but it's there nevertheless.
The contact though with the wall is pretty solid ... the o-ring is just there to keep everything together ... once the bold is tightened (and the HS diam. can
increase beyond the inner-diameter of the housing per design), the o-ring is fully compressed in its groove, and there's full (except for the grooves off-course)
metal-to-metal contact (including cooling-paste).

Cheers

Patrick

[dexter9]

don't you have enough space inside for the batteries? it looks big.

[patrickDM]

No, it's not that big (maybe just seems like that in the pictures)... total length of the head is 7.5cm ... inside-depth (i.e. behind glass) is only 5cm ... the heast-sink is
approx. 2cm thick ..
The rest is taken up by the led-assembly, lens, driver, and leaving some space to work with (supply-cable, piezo-cable).

[lucca brassi]

Good work ! - nice heat transfer , but middle led should be OFF , OR you have to put in middle cooper cork instead instead of that tube (same thing as Intel processor heatsinks .

Don't worry abour wires , you could drill hole somewhere between leds where is no Cu trace on AlPCB. Important at leds is that they have good thermal transfer in range of few milimeters from semiconductor joint ..... Al PCB also even more distribute heat equally but not to heat neighbours leds.

When wou made next time heatsink like that ...it is very good design , but you don't need to cut segments through , enough is only 1/2 - 2/3 max of cylinder only to transfer and distribute heat equally . Be sure that heatsink is inverted U hollow shape not full . (you don't want to collect and store heat in mass (Q=m*cp*dT ; A=Q*t)
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OOT : (I work with some very special welding machines (hot stacking ) these days at work , I'll put energy of 2500W @ 1000A @ 55ms (constant power mode) in segments with cca 1g turned with enlameted wire 0,22mm (1turn/2turn ) whole thing have diameter 15mm and high 6mm with 6 these segments.
(carbon commutators - that on picture is big and heavy one
Point of that is that with special approach it is possible to transfer pretty quick .