We have decided to gor for a 120 mm reflector hundreds of posts ago, and now we opt for a pre-collimating lens and a aespheric lens or a hughe TIR optic?
Don’t you think this will make the flashlight “a litte bit” more expensive and, with a TIR lens that big, quite a bit more heavy or (if plastic) more prone to lens-scratches?
It does sound very interesting, but please keep the basics of this project in scope: low cost, easy to manufacture etc………in other words doable.,
But hey, maybe next BLF thrower project can be a massive pre-collimating + aespheric torch? 2Mcd perhaps?
No, you’ve made a good point.
But he already knew it, and so he put a disclaimer in his post saying exactly what you mean.
Though, if he would tweak his design to suit the reflector it would only be some minor tweaks. So not a big deal imo at this point (which is all about outside design)
Alright, I’ve redraw my design so I could run a thermal simulation. Here is the result:
As I said, I’m not sure how accurate it is since this is the first time I did this. However i think this give us a good representation about how it will perform.
This is with a 40watt load distributed along the led shelf. Imaging that the MCPCB will evenly distribute the entire 40 watt load on the shelf.
Thermal convection coefficient is 20W/ (m^2.k), I really dont know what that means but its a good number for natural air convection. (like walking around outside I guess)
Ambient temperature is 300 kelvin around 30 degrees celcius.
I’ve run another simulation with a convection coefficient of 50W/ (m^2.k) and that gives a 20 degrees celcius difference (cooler).
It was just an example to help with realizing that size matters.
Small adjustments of something well balanced won’t be too hard, but keeping the length down helps quite a bit over time.
If you want performance i would say recoil reflector set up.
Problem though, is finding a decent and affordable 5 inch reflector that can take at least 120° from the LED.
So basically it looks like from the thermal simulations that the current design is just enough to keep an XHP35 cool enough to not burn you. Anything more and it will get too hot and need to step down. So we for sure need to keep cooling in mind as night time temps here in Texas can be easily 90f+ which would allow it to get even hotter.
Good info!
As far as the reflector goes, 5AR has not had a design to work with since we do not know what we will be using yet. That said I really like the shape he has come up with anyways, the strong taper to the head just doesn’t do it for me, looks a bit silly IMO.
There will naturally be some redesigns once we find a reflector.
And remember, this simulation is done with a convection coefficient of 30 W/(m^2.k), which is natural convection (almost no moving air/no forced cooling). If you would walk outside that number will increase, and that has a big impact on the results. (increasing the number to 40W reduces the temp by ~5 degrees celcius)
Also the battery tube isn’t part of the simulation, so that increase the mass which will reduce temps slightly.
And finally you hand plays a big role in cooling a light (well only if you’r not waring gloves but in the winter the temps are low enough that it wont have problems).
So I think that the cooling is good enough. Maybe some small tweaks.
It is good enough, I am not saying any major changes but we for sure don’t want any less cooling. The extra fins in 5AR’s last design is about the most I think would be needed.
