# Heatsinks: let's see 'em!



## rustola (Jan 15, 2008)

For those of you using heatsinks when you weld... what do you use?

- homemade or bought?
- backpurged or no? if so, how?
- best material?

After getting a major workout reaming out the seattube and chasing the BB threads on my first frame, I'm very much wanting to use some heatsinks on the next one to minimize distortion. Most likely wanting to make my own - I've got access to a lathe and a mill, though I'm kind of a hack machinist and not really capable of anything too advanced. 

I've seen pvd's page on his wiki, but what are other people using?

rusty


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## pvd (Jan 4, 2006)

I use a bb sink that i purchased from paragon that includes a purge and one for 27.2mm seat ream that i made for myself without purge.

Heat sinks are the sh!t. They make the st and ht so much nicer in the end. much better for any bike.

paragon bb:









pvd st:


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## rustola (Jan 15, 2008)

Just in case anyone else is interested in this, I also found these heatsinks by James Morikawa. Similar principle to pvd's home made ST heatsink.

PVD, did you just turn copper round stock then cut in half to make yours?


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## pvd (Jan 4, 2006)

yup.


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## rodar y rodar (Jul 21, 2006)

Does brazing mess with the insides of the tubes much, or are they mostly just for welding?


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## Walt (Jan 23, 2004)

*Not so great for brazing.*

They suck up WAY too much heat if you're brazing and make it impossible to get your joint up to temp - or at least that's what I'd tend to think. Heat sinks are mostly a TIG thing, as far as I know.

-Walt



rodar y rodar said:


> Does brazing mess with the insides of the tubes much, or are they mostly just for welding?


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## TacoMan (Apr 18, 2007)

rustola said:


> Just in case anyone else is interested in this, I also found these heatsinks by James Morikawa. .


Those are made from steel tube. It is better to use a dissimilar material like copper or brass otherwise if you melt through it is going to weld itself together.

It is not so much that they are heatsinks, but rather rigid plugs to keep the tubes from going egg shaped. I find the headtube itself is already a heatsink, so I use short plugs at each end to keep it round. You don't want one tube much colder than the other or you won't get a good weld, it is even more important with heat-treated tubes.

A heatsink works well when you are joining a thicker tab to a thin tube to prevent the tube from overheating and burning through. I like to use full-length sleeves in the seat tube and when making stems. They also prevent lumps from forming inside the tube.

My other business uses lots of heatsinks  
Heatsink Cases.


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## coconinocycles (Sep 23, 2006)

Walt said:


> They suck up WAY too much heat if you're brazing and make it impossible to get your joint up to temp - or at least that's what I'd tend to think. Heat sinks are mostly a TIG thing, as far as I know.
> 
> -Walt


yup. what he said. i would highly recomend a st sleeve to minimise brazing distortion and increase frame longjevity steve.


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## swift (Apr 3, 2007)

coconinocycles said:


> yup. what he said. i would highly recomend a st sleeve to minimise brazing distortion and increase frame longjevity steve.


As in; another length of tube, reinforcing the ST? ...Around the TT junction, I imagine?


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## coconinocycles (Sep 23, 2006)

swift said:


> As in; another length of tube, reinforcing the ST? ...Around the TT junction, I imagine?


yes. on the top of the st where you would normally have to ream the distortion out to slide the st in. one of my pet peeves is the failure of perfectly good frames due to cracking from the st slot/hole, tt/st or esp. st/ss junctions........there's alot of pics of them on both my web page gallery and my blog...........maybe someone can tell me how to link them to my posts...........i graduated high school when there were metal shops, not computer programming classes.......steve.


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## swift (Apr 3, 2007)

*warning: pretty much off topic*

I think the ST reinforcement is a great idea! You're absolutely right about it being an area prone to failure on a conventional frame. Do you have any 'rule of thumb' as to how long you make it? Thanks for the insight. :thumbsup:


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## coconinocycles (Sep 23, 2006)

swift said:


> I think the ST reinforcement is a great idea! You're absolutely right about it being an area prone to failure on a conventional frame. Do you have any 'rule of thumb' as to how long you make it? Thanks for the insight. :thumbsup:


on most of my frames {except for the mega-stout 1.25" st ones, those are 4.5"} they are 3 7/8" long, with 1.75" of st above the top of the tt. i build bikes with lots of standover, so i make sure the st mast is well supported. i'll highlight the manufacture of st sleeves on my blog in the next build {today or tomorrow} so stay tuned. i'm glad to try to show aspects of building on my blog if folks leave comments there asking specific requests on what you wanna see. again: www.coconinocycles.blogspot.com glad to help, steve.


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## EnginCycles (Dec 21, 2006)

i use the heat sinks for welding and made these little buggers for brazing. they are heat sinks for the outside edge only. it helps when you are toe nailing the stays to the outside edge of a BB and when your TT is rather close to the top of the HT. they take very little to get up to temp and seriously help prevent any ovalizing when brazing. i clean them with a scotch brite before brazing (not so clean however that the brass will stick to it) and have had the chain stay really close and still the brass stopped at the edge of the BB shell.

__
https://flic.kr/p/2075942293

-drew


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## rustola (Jan 15, 2008)

*More heatsink pics*

Here's some photos of heatsinks I took at nahbs this weekend. First two are the exploded version of the Paragon BB heatsink as in PVDs post above. Sorry a little hard to make out, but very very sweet, I plunked down the cash for this one. Second two are backpurged seattube heatsinks made by Sputnik tool. Machined out of bronze and split into thirds, with a drilled out allthread running down the middle that hooks up to gas. Also available with a quick-connect gas adaptor. Gonna try to make one of these myself, but I'm sure it won't be darn near as pretty.


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## Loretta (Sep 28, 2004)

coconinocycles said:


> yup. what he said. i would highly recomend a st sleeve to minimise brazing distortion and increase frame longjevity steve.


In complete agreement on this. A simple piece of 4130 as a sleeve is a great little insurance policy on a high failure area of a frame. Plus, you have a great opportunity to carve on it and make it all purty 'n such.

Steve, I think you mentioned in another thread that you silver braze the sleeve and then use brass for the seat stays. Do you have any issues with over cooking the silver during the brass brazing?  If for no other reason than precaution, I use silver for both the sleeve and the SS/ST junction.

Tim


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## TacoMan (Apr 18, 2007)

I don't use a sleeve, but rather a custom two-piece seat tube welded together. The top section is a thick wall tube about 3" long bored to the post dia. with a step machined in it. The step slips into the double butted lower tube and fuse welded. Works great, real clean and gives a good solid area to weld the seat stays, top tube, and seat clamp.


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