Will the color of an electric unicycle have a big effect on internal temperatures?

[WakefulTraveller]

Dark objects are known to become hotter in the sun. This happens as a result of the high emissivity of dark objects. High emissivity objects will absorb more radiation from the sun's rays. And strikingly enough, high emissivity objects will also radiate heat at a faster rate than low emissivity objects.

When it comes to vehicles left in the sun, the higher emissivity, the higher the internal temperatures. There's this BuzzFeed video that quickly demonstrate the phenomena: https://www.youtube.com/watch?v=ZS95SPm4f2I

 What I'm curious about is if this makes a big difference when actively riding an electric unicycle, and if so, would it then be worth going with a lighter colored EUC to counter these effects and to thereby stand a better chance of preventing overheating from occurring? Or does color taste win out?

[The Fat Unicyclist]

Awesome question! 

And a lighter coloured EUC should absorb less radiation from the sun. But wouldn't the main cause of overheating originate from an internal source? And if that is the case, wouldn't a darker coloured EUC absorb (and then dissipate) that heat more efficiently?

Either way there is one "colour fact" that we know for sure... The red ones go faster.

[Chriull]

One has to differentiate here between infrared radiation and visible light. Absorption of visible light is what defines the color.

The absprbtion over the whole spectrum heats up the material onces exposed to sunlight.

The emsiision/absorption rate at infrared wavelength determines the efficiency to emmit heat to the enviroment. (https://en.m.wikipedia.org/wiki/Black_body)

So the seen color of an object does not have any real correlation with its possibility to emmit heat radiation...

The best material should be "white" for every wavelength but the specific infrared wavelength of "the heat" produced, for which the material should be "black". (Least absorbtion of the sun spectrum but possibility to emmit heat radiation..)

From what i have read so far about heatsink radiation is of lesser importance than convection and there especially the color of the heatsink is in the lower percentage region regarding efficiency... Depends on the specific usage, of course.

in the case of the plastic cover of the wheel for summertime with broad sunshine white is ?a bit? Better - also with the white plastics the wheel will heat up if let lying in the sun in regions where the thermal overheating threshold of the wheel is reached - but it should take longer than with a black wheel... The possible cooling by radiation should imho be quite neglectible - the material imho absorbs much more energy from the sunlight? The only thing that should help in this case is movement to get cooling by the air movement.

some "metalic effect" finishing could/should decrease the absorbtion of heat in sunshine, but one could easily also lock the heat produced by power dissipation inside with such measures...

[Blunzn]

no matter what color you have, don't leave them inside a car on a hot summer day.

somewhere in china ...

[WakefulTraveller]

One of the big reasons that the interior of a car becomes hot when left parked out in the sun has a lot to do with the windows letting in a lot of sun light. The light then gets absorbed by the black upholstery and converted to heat energy. In a cool white car, the heat would escape through conduction. However with a black car, the heat becomes trapped by the hot exterior, and the internal temperatures rise. 

Now fortunately black electric unicycles have a couple advantages over black cars:

1. Windows on EUCs are practically nonexistent with only a few rare exceptions. 

2. EUCs happen to be made of plastic rather than metal. This is beneficial because plastic acts as an insulator more so than a conductor. Therefore, the heat energy will have a harder time passing through. Yet this can be a mixed blessing if there happens to already be built up heat energy that requires an escape conduit. This is where white is at a disadvantage; as white is an even better insulator, it will trap the internal heat more effectively.

It's my hypothesis that a black EUC will have only a slightly higher internal temperature than a white EUC when being actively ridden but not when left out in the hot summer sun to bake.

[WakefulTraveller]

So I purchased a roll of metalized mylar tape tape that I believe will be an excellent thermal insulator. I will give this a try on my black MCM4 and see how it goes. 

http://www.amazon.com/CS-Hyde-Metalized-Acrylic-Adhesive/dp/B003HKRFA8/

I was considering applying thin layers of aluminum tape, which probably would have worked alright, but with aluminum being a conductive metal and all, it's not a great choice. 

[WakefulTraveller]

So far I have covered the entire inside of one of the side covers with the metalized mylar tape. Can someone say whether or not this will actually work as thermal insulation?

I'm sorry for the out of focus photo, the camera on my phone wouldn't focus.

I will try to do some tests later to see if this actually works.

It might be best to now move this thread over to the Mods & Repairs section.

[WakefulTraveller]

Before:

After:

Before:

After:

Overall I'm very happy with this customization. Even if it doesn't really help to keep it cooler, it will make it more visible when I ride home from work after it starts to get dark.

 

[Hunka Hunka Burning Love]

I would think depending on where you live if there's a strong sun and high temperatures that the black shell covering would heat up more than a light coloured shell as it would absorb more light energy.  With the mylar reflective tape inside I'd be concerned it might keep radiant heat energy trapped inside as it all heats up sort of like an oven.  It might work better if the tape was covering the black shell parts, but that's probably not possible to do.  Maybe Plastidipping the outside of the shell covers in white might help more.

[Makoben]

White reflects the heat more than black. It looks like you put reflective vinyl on your wheel, which will help reflect the heat. If it is insulated tape(thick) it may help keep heat in the wheel. The plastic shell is an insulator and helps keep the heat in the wheel. We are talking about two different problems. The first is trying to keep additional heat from the outside from coming in and the second is trying to get the heat that is generated from inside the wheel out. There are other posts on the forum on trying to disapate the internal heat. 

Since the wheel shell is plastic, long term ultraviolet radiation will affect the plastic. Almost any covering paint, vinyl, or metal will help with that. A stock plastic she'll will probably last longer than I will, but who knows in thirty years there may be a classic EU club riding ancient 2015 wheels.

mike