# Solid pill/heatsink for Minimag?



## TigerhawkT3 (Oct 2, 2008)

I want to get good heatsinking in a Minimag. I was thinking a solid piece of Cu or Al with a diameter matching the ID of a Minimag, that could be put through the tail and forced up toward the lip of the threaded head area. How effective would that be? Would it be possible or desireable to find some way of getting AA between the pill and the Minimag? Any other suggestions?


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## gadget_lover (Oct 2, 2008)

In theory that works well. The closer the fit between the mag body and the heat sink, the better it will work. The more contact (up to an extent) the better.

In practice, the minimag is not a precision instrument. The bore diameter can and will change from one end to the other. How do I know?  I've had to un-jam slug style heat sinks that got 1/2 way to the head.

Having said that... prep the tube in advance and you will likely end up with good heatsink.

P7 ???


Daniel


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## TigerhawkT3 (Oct 2, 2008)

Cool. Do you think solid Cu would be soft enough to "compensate" for slightly smaller IDs? And what do you mean by prepping the tube?

Where do you get precise sizes of Cu rod? Would it have to be turned piece by piece?

This is for 2S2P MC-E on 2x14500 LiFePO4, BTW.


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## gadget_lover (Oct 2, 2008)

Prepping would be simply making sure that it has a fairly consistent bore. You may need to use a hone it to make sure it's consistent. If not consistent, then at least tapered from the tailcap to the head. 

You just need to make sure the slug makes it all the way down.

The rod can be purchased in many sizes, but getting it in just the right size for a minimag will probably require that you turn the rod to match the id. A mismatch of 10/1000 of an inch will mean it barely touches the side.

Daniel


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## Illum (Oct 2, 2008)

Someone needs to make a 2/3AA sized bar of aluminum or copper with a little neck stick out of the body from the top and allows enough space for maybe a resistor and driven by 14500's :nana:


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## TexLite (Oct 3, 2008)

TigerhawkT3 said:


> Where do you get precise sizes of Cu rod? Would it have to be turned piece by piece?
> 
> This is for 2S2P MC-E on 2x14500 LiFePO4, BTW.


 
I think turning down the heatsink will be the best choice as well.Because,as mentioned,its unlikely you'll find a size thats fits just-right without turning.Round stock comes in standard sizes.And you'll also need a step at the top of the sink.

Copper rod or round stock can be purchased at a number of places,both online and B&M.
McMaster-Carr,http://www.mcmaster.com/
Fastenal,http://www.fastenal.com/
Grainger,http://www.grainger.com/
Online Metals,http://www.onlinemetals.com/

FWIW,I'll be doing a similar project,Mini-Mag,MC-E in series,two 14500 Li-Ion,and a boost converter.I'm planning on using aluminum instead of copper because it will be a Hot-rod anyway,the small mass of the Mini-Mag most likely won't allow for extended runtimes.

The material choice might change though,you guys have me thinking.It will most likely be a month or so before I get everything together.If you haven't got yours together by then,I'll send you a PM,I could cut you one out at the same time.

-Michael


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## will (Oct 3, 2008)

If you knurl the outside diameter of the heatsink it will yield a certain amount of give to get a good tight fit. I have done a numer of press fits using mini-mag bodies. If the fit is too tight, there will be stress cracks in the anodize, barely visible, but there.


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