I have already designed the circuit board for the Engines and so, hopefully, they will arrive before Christmas. But if you look at the lit engines in the show, the most ideal light source would be a 30-40mm COB Warm White LED. Alas, they with a 50mm aluminum heatsink. There are some that does fit but would require a working voltage between 9v to 12v.
The COB led would illuminate the engines perfectly without any hotspots and more. As for my design, they are just a bunch of LEDs trying to do the same thing. I have also put in an order for the 50mm COB LED as well.
THE TOP HAT LED
In the middle of the AMT clear part, there is a small clear cylinder attached to the disc. This which not only diffuse the lights (after some light sanding) but also helps keep the Engine parts together. If I am going to go ahead with my PCB design, I would need a LED for the middle.
The LED I have in mind is the Top Hat LED. They usually have a very wide viewing angle and are very bright. The same can be said for SMD LEDs but their effective brightness range are mere millimeters.
MOUNTING THE LED
You can fit the 5mm top hat LED easily into the clear cylinder which has an inner diameter of about 6mm. But before that, I will have to cut out a small 13.5mm circle made from draft paper. This paper is excellent as a diffuser but you’d need to place the LED quite a distance away.
It is much cheaper but you’d need to try a few times to get the correct diameter.
On another note, notice the lighting effect of the top hat LED. Most of the engine’s insides are lit. But this is not the effect I want.