[RickyBoy]

[dashpuppy]

Originally Posted by RickyBoy

I like it, how do you find the visibility in the sky ? Any more pics of the inside and wiring ?

[RickyBoy]

Very easy to see, I will take some pics of the inside

[Luke352]

Hi Guys,

First post on these forums. I normally just view the build threads on here as you Canadians do some amazing builds.

But something in this build had me a bit concerned, if it's been done and worked before then fine, but it's not something i'd personally do.

That is the complete removal of any form of heatsink from the ESC Fets. As i'm sure you're aware thermodynamically air has very poor heat transfer properties, which is why heatsinks are used in the first place. They have two purposes one is you are giving the heat somewhere else to go quickly by giving it a large piece of alloy to transfer to which has very good performance at removing heat. A heatsink will be much better at removing heat quickly. Secondly and probably more importantly you are making a much larger surface area for any air to transfer heat from.

You've taken away any form of heat sink, and probably reduced the surface area for the airflow to act on down to less than a tenth of the surface area with the heatsink fitted.

There is a reason all the ESC's that come fitted with fans actually still have a heatsink. Airflow acting directly on Fets is a very poor form of heat transference.

The fact that this is a 300a ESC but using only about 150a from what has been written here is probably helping keep temps down. But personally if I wanted to reduce weight I would have used a lighter heatsink for instance one with a thinner baseplate and maybe shallower fins, or you could machine the current baseplate thinner and lower the height of the fins and still fit the fans.

If this type of setup has been done before and worked without issue then it's an education for me that this will work. But thought I should say something, if only to ease my conscience, if something did go wrong. Please don't take it as criticism, but more an observation.

I love seeing your builds TBrum!

[TBrum]

Hi Luke!! Thanks for the post!! Makes a ton of sense to me.

This combo hasn't flown yet, but hopefully Peter will get it airborne in the spring. I'll be interested to see if he has any issues. Perhaps putting a metal plate over the FET's within that enclosure (and keeping the fans in place) would be a better solution?

Trev

[dashpuppy]

Originally Posted by Luke352

Hi Guys,

First post on these forums. I normally just view the build threads on here as you Canadians do some amazing builds.

But something in this build had me a bit concerned, if it's been done and worked before then fine, but it's not something i'd personally do.

That is the complete removal of any form of heatsink from the ESC Fets. As i'm sure you're aware thermodynamically air has very poor heat transfer properties, which is why heatsinks are used in the first place. They have two purposes one is you are giving the heat somewhere else to go quickly by giving it a large piece of alloy to transfer to which has very good performance at removing heat. A heatsink will be much better at removing heat quickly. Secondly and probably more importantly you are making a much larger surface area for any air to transfer heat from.

You've taken away any form of heat sink, and probably reduced the surface area for the airflow to act on down to less than a tenth of the surface area with the heatsink fitted.

There is a reason all the ESC's that come fitted with fans actually still have a heatsink. Airflow acting directly on Fets is a very poor form of heat transference.

The fact that this is a 300a ESC but using only about 150a from what has been written here is probably helping keep temps down. But personally if I wanted to reduce weight I would have used a lighter heatsink for instance one with a thinner baseplate and maybe shallower fins, or you could machine the current baseplate thinner and lower the height of the fins and still fit the fans.

If this type of setup has been done before and worked without issue then it's an education for me that this will work. But thought I should say something, if only to ease my conscience, if something did go wrong. Please don't take it as criticism, but more an observation.

I love seeing your builds TBrum!

tbrum and i got into that already, i'm not to sure if it's going to survive either! It might, personally id have some kind of telemetry temp setup to monitor it for the first few flights and see..

[Luke352]

Originally Posted by TBrum

Hi Luke!! Thanks for the post!! Makes a ton of sense to me.

This combo hasn't flown yet, but hopefully Peter will get it airborne in the spring. I'll be interested to see if he has any issues. Perhaps putting a metal plate over the FET's within that enclosure (and keeping the fans in place) would be a better solution?

Trev

Hi Trev, yes a Metal/alloy plate held down against the Fets would be much better then just fans, a plate alone will at least double the surface area since it will fill all the space between the fets as well. It will also pull heat away quickly during power ups for takeoff and fast passes, airflow just won't pull away the heat quick enough from the fets alone.

Originally Posted by dashpuppy

tbrum and i got into that already, i'm not to sure if it's going to survive either! It might, personally id have some kind of telemetry temp setup to monitor it for the first few flights and see..

It's nice to know i'm not the only one concerned. I would be doing some decent power runs on the ground, well for as long as you are comfortable with motor temps. Since the motor will likely get very hot doing ground power runs for any significant time. The ESC since you have a fan setup may or may not have a significant change between ground and flight with temps.

I was just looking on digikey for suitable low profile and weight heatsinks. http://www.digikey.com/product-searc...=0&pageSize=25

I like the look of the low profile ones with splayed cooling fins like the BlueIce series, you could potentially remove the outer fins to get the width down slightly. Some of those heatsinks have very low profiles and will also be very light.

[dashpuppy]

Originally Posted by Luke352

Hi Trev, yes a Metal/alloy plate held down against the Fets would be much better then just fans, a plate alone will at least double the surface area since it will fill all the space between the fets as well. It will also pull heat away quickly during power ups for takeoff and fast passes, airflow just won't pull away the heat quick enough from the fets alone.




It's nice to know i'm not the only one concerned. I would be doing some decent power runs on the ground, well for as long as you are comfortable with motor temps. Since the motor will likely get very hot doing ground power runs for any significant time. The ESC since you have a fan setup may or may not have a significant change between ground and flight with temps.

I was just looking on digikey for suitable low profile and weight heatsinks.

I like the look of the low profile ones with splayed cooling fins like the BlueIce series, you could potentially remove the outer fins to get the width down slightly. Some of those heatsinks have very low profiles and will also be very light.

I have boxes of heat-sinks, and they are also very cheap on ebay too, just a nice piece of extrusion would be perfect, then cut to length.

[Luke352]

Originally Posted by dashpuppy

I have boxes of heat-sinks, and they are also very cheap on ebay too, just a nice piece of extrusion would be perfect, then cut to length.

Oh agreed, but that is basically what was fitted. I was just showing some examples of what is available if he was looking for low profile and weight.

[Steve N.]

Originally Posted by smchale

Peter,
I think you need to invent the first heat resistant CLEAR bypass and cover!

I was just reviewing this thread, and came across this. Nicolas from Belgium (SpiderJets on RCU) has already beat you to the punch. He makes a transparent Bypass with hi-temp Lexon.