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Finless Bob's Helifreak Tech Room Finless Bob's Helifreak Tech Room - Tips and how-To Videos


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Old 06-11-2006, 11:41 AM   #41 (permalink)
 

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Thanks Bob, very useful mod. Don't know what Align was thinking, probably trying to cut corners to speed up production.
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Old 06-12-2006, 11:26 AM   #42 (permalink)
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Has anyone tried the easier way to just attach the heatsink to the metal plate without removing the tape between the mosfets and the plate ? Because, if it only eventually turned off during flight in hot days, it may be enough to just do it the easy way.
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Old 06-12-2006, 11:36 AM   #43 (permalink)
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the trouble is i beleive the tape to the mosfets is just as inefficient as the sink to shrinkwrap. Align screwed up twice. To realize any benefit from one you've got to do the other.
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Old 06-12-2006, 05:28 PM   #44 (permalink)
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I agree with cudaboy_71 on this one. It might help some, but not enough to make it worth the trouble when for a little more effort it can be done right, the first time you do it.
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Old 06-13-2006, 09:46 AM   #45 (permalink)
 

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Maybe I should have said donít try this at home. I just wanted to get all the lost information back that we could for somebody reading this for the first time. I thought the discussion lost at RR was very good and some of those ideas might be useful in a pinch or on other applications. I was working through problems when I first found the RR thread. It was a great discussion and the first mod I did to the T-Rex. I am sure the thermal epoxy used is the best and I didnít suggest using regular epoxy alone which is plastic and a heat insulator. I donít know how it would compare to heat shrink or air. I just pointed out some viable and tested options. Here is the link for making your own thermal epoxy http://www.overclockers.com/tips683/

In the "lost thread" there was one guy in Australia who couldn't find and thermal epoxy and used thermal paste alone. He got the heat sink to stay in place using the heat shrink. I believe the paste has an even higher thermal transfer than the thermal epoxy. I think the thermal epoxy is a compromise in thermal transfer to achieve adhesion. The non-electrically conductive properties also probably required a compromise in thermal conduction ability compared to those that are electrical conductors. Using thermal adhesive is good for practical reasons in this case and it has some type of epoxy in it, which is a heat insulator and probable reduces its heat transfer ability (a compromise). If you want to go after more subtle things you probably should remove the anodize from the base of the heat sink. It decreases heat transfer by conduction (bad for the glue line) and increases heat transfer by convection (good for the cooling fins) and possibly radiation (especially in black) so I am told. Now they use other colors that are prettier and work almost as well. Also the flatter the surface and the less thermal whatever you use the better. Both the stock heat sink and the one I used were not flat due to the extrusion process. And, yes I flattened the base of the heat sink thus removing the anodize, used a better heat sink with lighter bigger fins, touched off the top of the sims with a mill file (they had some high spots on them), used Arctic Alumina thermal epoxy, and clamped as tight as I thought I could get away with given the delicate parts using a soft clamp. I like those soft clamps in the directions. I also used a piece of soft aluminum to shim for the space where the heat tape had gone instead of bending the joggle into the EMF plate to step up over the switching transistors. That way my longer heat sink could go the full length of the EMF plate and over the switching transistors.

I donít think that any of these things are significant compared to having heat shrink between the heat sink and simís. Seeing now how well it works some of this was overkill but it canít hurt. If I did it again I would probably get the older thermal epoxy used here from BlakeMcBrayer and use the stock sink as it is adequate and looks better. After the mod I ran it then touched the board on both sides with out the heat shrink on and nothing gets hot.

This is a great mod and those are excellent directions! Seems ridiculous that we have to do this. Thanks Bob and thanks BlakeMcBrayer for making the materials available. That is a lot of work.
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Old 06-13-2006, 11:28 AM   #46 (permalink)
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Hehehe Gary... good stuff and thanks for bringing back some of the lost discussion!

Back when we were over clocking Celron 300's and making them 450mhz processors I use to LAP the heat sink, use the best thermal trasanfer compound you could get etc... YES doing all of the above does help thermal transfer!!!! But as you say for this application just the fact of getting the heat sink on the MOSFETS is good enough IMHO......

Thanks again,
Bob
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Old 06-13-2006, 02:18 PM   #47 (permalink)
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I'm still a mostly mild flyer. The heaviest load I can 'safely' put on the 35G ESC is full throttle FFF, which because of the high airflow over the components is not the best way to test the thermal mod, but I've intentionally flown for max loading in the hot sun here recently on a 105į day for a full pack, and when I landed the ESC's heatsink was barely warm to the touch.

Considering that the airflow during hard stationary 3D is still pretty good due to the rotor wash, I think this ESC mod pretty much solves all the temp issues it may have had.
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Old 06-25-2006, 03:14 AM   #48 (permalink)
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GimbalFan,

Thanks for the update on your mod.

How about everyone else? I have been sending out lots of the epoxy kits, but no one seems to be posting the results?
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Old 06-25-2006, 06:56 AM   #49 (permalink)
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Blake, Mine has been doing great also. I haven't put a temp gauge on it but its way cooler than the motor and battery. I'll get a reading today
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Old 06-25-2006, 08:42 AM   #50 (permalink)
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I've been too busy flying to do the mod on my 25 ESC.
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Old 06-25-2006, 02:45 PM   #51 (permalink)
 

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I used the thermal tape which I got from Fry's. I made the Z-bend just like what is shown. Heatsink is barely warm from touch after a 10 min hover. Got the Artic Silver too but I'm worried that if applied, it might touch some of the IC pins.
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Old 06-26-2006, 03:59 PM   #52 (permalink)
 

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is this mod still needed with the new 35X align speed control with 6v bec and the BLUE heatsink?
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Old 06-26-2006, 05:46 PM   #53 (permalink)
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Yes it is....

Bob
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Old 06-29-2006, 11:18 AM   #54 (permalink)
 

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Quote:
epoxy from MG Chemicals that Bob uses in his mod. The smallest bottles of epoxy that can be purchased run any where from $35 to $45 dollars for 450ml.
Hey guys, can I use JB WELD epoxy instead of that MG Chemicals Epoxy?

THX,

Isaac
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Old 06-29-2006, 11:21 AM   #55 (permalink)
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Turbo Boss, you can if you want to burn up your ESC JBweld is conductive!!! in other words no you need thermal epoxy.
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Old 06-29-2006, 06:37 PM   #56 (permalink)
 

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Quote:
Originally Posted by skew
Turbo Boss, you can if you want to burn up your ESC JBweld is conductive!!! in other words no you need thermal epoxy.

Hey Skew, thx for the tip, I have no idea the JB Weld was conductive.

I will check here in my country if I find that epoxy.

THX

Isaac
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Old 07-05-2006, 06:05 PM   #57 (permalink)
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Hmmm, should have stoped modding my ESC while I still was awake

I managed to get some Arctic Silver on/between the pins of the mosfets. Should i worry about this, or is it ok? Kinda hard to take it off again

John
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Old 07-05-2006, 06:11 PM   #58 (permalink)
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If it is the thermal epoxy then that is not conductive but check some of it using an ohm meter to be sure..

Bob
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Old 07-05-2006, 06:16 PM   #59 (permalink)
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It says that it's not electrically conductive but that the compound is very slightly capacitive.

Don't know if that matters or not in this case.

John
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Old 07-05-2006, 06:22 PM   #60 (permalink)
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You should be OK.

Bob
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