I am not talking about what the motors are capable of. I’m talking about tension forces in the chain as the angle between the chains increases. This happens to be pretty easy to calculate.
To help envision why the force on a chain increases as the angle of the chain increases imagine tying a rope to a bucket of water then lifting the bucket to the height of a door knob. The force (tension) on the rope and the force your muscles need to exert to lift the bucket are each equal to the weight of the bucket.
Now imagine if you pass the same rope through the bucket handle and tie it to a door knob. Stand back holding the other end of the rope with the bucket between you and the doorknob. Keeping your hand at the level of the door knob you could pull the rope and lift the bucket but it would take quite a bit of work to raise a 10 pound bucket even a foot. Try raising the bucket so the handle is at the same height as the doorknob – you can’t do it!! In fact, the force it takes to raise the bucket to that height spikes to infinity. It literally can not be done in our physical world.
The equation to find the force on two cables under load at a given angle is:
F = (m x 0.5) ÷ cos(a x 0.5)
where:
F is the calculated force on each cable
m is the mass
a is the internal angle between the two cables
The dividend:
(m x 0.5) = (20 x .5) = 10
The divisor:
cos(a x 0.5) = cos(145 x .5) = cos(72.5) = .3007058
Divide for quotient:
10 ÷ .3007058 = 33.26lbs (per chain)
The 33.26lbs per chain is based on normal operation and does not account for drag. It is the force on each chain when the sled is in the top center resting position. It also doesn’t account for runaway software that runs a motor until things break or poorly built sleds or crappy wood or anything else.
If you see a problem with my math or can show me how you calculate 66 lbs on each chain I would love to hear it.
Thank you, I know quite well what #25 roller chain is. Honestly I figured someone would probably mention that you can’t fit that shackle through #25 chain, or that even if you could fit it the orientation of the shackle is off by 90˚. I assumed that was clear and that a jumper ring would need to be used. It could be anything really, like a keyring or a piece of wire, heck it could be a stale piece of free range, fair trade, open source, gluten free bread as long as it could withstand the tension!!! Adding a reasonable link between the end of the chain and the shackle (pivot point) will not change the physics.
It may be non-trivial but it doesn’t have to be complicated. A shackle through plywood is quite accurate, especially if people don’t have access to precisely cut and drill 3/16" metal.
What prevents you from doing this with any other linkage design? The bars are all straight, they could all be cut the exact same way. All of the measurements are critical, even the holes on the arms (“horizontal” pieces) right?
I’m not sure if the benefit of having the Top Mounted version out of the way of the router is enough to outweigh the chain attachment point problem (very steep angle at maximum travel) and the compression/tension slop (which results in the router being below the tip of the chain triangle). Maybe it is worth it? Both of those things can be solved. Who knows… I can’t wait until more people with Maslows start building these different designs and testing them!!
I’d try it right now but someone would have to send me a free Maslow first 