Heat sink diy

[michäel2]

hi all,
im planing of making a set of heat sink and I'm looking around at the different design one could go with, and that raised the following questions.

first of, is the idea to have as much contact area as possible and as much brass in there, as in brass absorbs the heat and as such the more brass the more heat it can absorb ?
in that case i would go with two round halfs of brass like in the photo below:Screenshot 2015-08-16 19.06.16.jpg

or should i put a bitt more effort in and go with a design that has a few more cuts in its design and as such looks like it can radiate the heat better ?like the one's in this photo ?Screenshot 2015-08-16 19.15.11.jpg

what ever design i will go with it will have to be able to purge as well.

i don't quite know the nitty gritty about how these puppies do there job and i hope perhaps someone here can explain it to me, i have used the search function on heat sink but no price (-:

thanks, mick van aar

[roadrashdave]

I got some stuff from a company FOC recently to build my jig

He sent me these plans to make mine on a lathe.

http://bicyclemanufacturing.co.uk/wp...BML-HS-100.pdf these were downloaded from the link ,cut copy and paste it in your browser and it appears

Cheers

Dave

[Alistair]

You may find this flickr set to be of some help,

https://www.flickr.com/photos/duncan...57632976565126


Alistair.

[Mark Kelly]

Further to Mike's lovely drawing:

There is no appreciable radiation or convection from the heatsink so, unlike most things called that, it is truly a heatsink. Accordingly you want to be able to conduct heat into it and for it to have a high thermal mass relative to the part being cooled. The first is a function of surface area in contact and materials, the second is a function of total volume and again material.

On the first, since steel and especially stainless have fairly poor heat conduction, area will trump material: as long as you use something with decent conduction like brass or bronze you'll be OK. Accordingly, any cutouts or other fancy engineering must serve to improve the contact area by allowing the heatsink to conform to the part being cooled, otherwise they're pointless at best.

On the second, thermal mass (more properly volumetric heat capacity) doesn't vary much between different solids*, again if you stick to brass or bronze you'll be right. As above, cutouts etc mostly serve to decrease the available volume so they need to have a very good reason to be included.


* the range of VHCs for solids is between about 1.2 and 3.6 and the very low ones are things you're not likely to use like bismuth and antimony. For things you are likely to use the range is about 2.4 to 3.6. Copper alloys are at the high end of the range so go with them.

[michäel2]

thanks Mark for the answer i was looking for !
and thanks dave and Alistair (i really like the use of spoke for the retaining rings, i was wondering what i was going to use for them ) for some excellent designs.
i know what ill be doing the next couple of weekends!
this forum has again proven to be an excellent resource !
mick van aar

[Jonathan]

i think you guys are missing one fundamental requirement for most of these commercial heat sinks, the ability to flow argon when welding.

[Mark Kelly]

That was taken as read from the OP:

what ever design i will go with it will have to be able to purge as well.

Argon is too expensive to use as a coolant.

[michäel2]

what are suggesting mark ?

mick van aar

[Mark Kelly]

Sorry if that wasn't clear: it was a response to Jonathan rather than to you.

[Amaro Bikes]

Argon is too expensive to use as a coolant.

¿¿???

Anyone concerned enough as to use heatsinks should be concerned as well as to back purgue. Nothing to do with coolant, but oxygen contamination.

[Mark Kelly]

OK, since I seem to have confused everyone, I'll restate my response to Jonathan's post:

I didn't mention argon because the OP had already stated that back purge was a necessity and because I don't see it as a significant factor in heat transfer: gas cooling the weld zone with argon would be very expensive.

[Amaro Bikes]

Hi Mark

Jonathan answer was important as OP asked for back purgue as necessity, so if heatsinks do not allow for proper argon flow, any of the argon placed inside of the frame won't be able to go through the vent holes (which in most cases are usually placed exactly where the heatsinks are inserted).

so, no matter how good the heatsinks work as cooling system, none of the inserted argon will be able to back purge certain welds (seatstays, chainstays, top tube, downtube), effective back purgue will only be happening on the actual hetsinks contact surfaces (seat tube, Bottom bracket and headtube).

Cheers

[Mark Kelly]

The OP specifically asked about the thermal performance of the heatsinks and stated that purging was independent of the characteristics about which he was asking.

He also stated he'd done a search so presumably he's read this thread.

[Amaro Bikes]

Hi Mark, I have no intention of create any discussion or the like, just trying to help!

OP said "what ever design i will go with it will have to be able to purge as well". You can't separate both functions on a heatsink, they're not independent factors, they have to be able to work both as heat control and argon suppliers for back purgue. It's like lightweight components, they have to be reliable as well, they're not independent and everything gets related, no point of making the lightest fork in the world if it's not reliable, right? So there's no point on making the most cooling heatsink if it does not help effectively placing Argon inside of the frame

cheers

[Jonathan]

I'm not sure I've seen anyone be very concerned with the thermal properties of a heat sink, but everyone I know who welds too is concerned about argon purging and getting it right, especially as the materials get thinner and include stainless and TI.

[michäel2]

Hi Mark, I have no intention of create any discussion or the like, just trying to help!

OP said "what ever design i will go with it will have to be able to purge as well". You can't separate both functions on a heatsink, they're not independent factors, they have to be able to work both as heat control and argon suppliers for back purgue. It's like lightweight components, they have to be reliable as well, they're not independent and everything gets related, no point of making the lightest fork in the world if it's not reliable, right? So there's no point on making the most cooling heatsink if it does not help effectively placing Argon inside of the frame

cheers

i have been puzzling about this as well, i suppose it right to say where there is brass there won't be argon. and indeed heatsink only works when its in direct contact with the material that is being welded.
in that case i perhaps should wonder if its better to just purge and not have a heat sink ?

the aim is to work with stainless for now, titanium later.
thanks, mick van aar

[Mark Kelly]

It is true that where there's brass there won't be argon, but neither will there be air.

If you are really worried, purge the shell then insert the heatsink. Job done.

[Amaro Bikes]

Air is not only on the inserted heatsink place, think of the tubes coming to that tube...

[VertigoCycles]

It is true that where there's brass there won't be argon, but neither will there be air.

If you are really worried, purge the shell then insert the heatsink. Job done.

HUH!? I'll get right on that, let me make sure I have the steps correct.

1. close up BB shell save for an entry and exit hole to allow argon to flow in and out.
2. insert argon line
3. get a coffee
4. remove argon line and whatever I used to plug the shell (eddies and gravity will surely not be in play, right?)
5. hold breath and carefully insert heatsink
6. weld with the knowledge that it's not possible to have lost any argon from the shell, nor any argon that made its way into the chainstays, seat tube and down tube, due to air currents or gravity.

Did I get this right? I can't help but think that I've been wasting so much time and argon over the past nine years.

[Amaro Bikes]

should wonder if its better to just purge and not have a heat sink ?

Mick, if you want to work with stainless and titanium, you might be ok without heatsinks if your heat control is perfect and you use thick wall thickness, but you can't go without purge at all. Heatsinks are not too expensive if you consider the much better quality you'll get on your welds, avoiding overheat, distortion, etc, and if you make them your purge fitting points, you have two functions in one tool, win-win. Paragon's BB shell heatsink/purgue is perfectly made at a very fair price. For headset and seat tube you can make your own or make someone made them for you (I had a super great job made by this Vsalon member Sebaudet ,thanks Seb!)

To me, it's always useful to watch what the experienced people are doing so to learn their process (wich is usually based in long years of experience), there're no shortcuts, sure you'll be able to find your own way on the process, but they're the best living lessons to start with (mixed with your own workbench hours). Watching any of the workshop process pictures from Tig masters like Tyler, Drew, Rody, Sean, Kris, Mike, etc will help you understand what goes where and why, and see what you might need to do the best possible work.
I could never thank them enough for all the information they openly share for anyone to see how does hell's oven get fired. No microwaves here

Cheers