4' x 4' x 8" Router Build

[JonnyFive]

The 50N loading in which direction.?

I'm referring to the reaction force of the machine pushing the cutter through the material so could be in any direction depending on which way the router is moving. My only reference point is using a hand router and it doesn't fell like it needs 50N to push the router along. I'm talking about the cutting force as shown on this diagram:

two pieces of 120 x 80 arranged in an L shape gives much stiffer gantry with lower vibrations than single 160x80

Do you mean 120 x 60? I can't find 120 x 80. I have run the calcs on the L section and I'm amazed how much difference it makes - you've convinced me! Do you have any examples of the machines you've made, I'd love to see them.

Cheers