That’s probably a bit above my pay grade to answer…
I don’t know what the correct answer to solving the bed drop is, But at some point the lengths you go have to make sense all around.
it seems the most cost effective solution would be the e-brake ( if a reliable one can be made) or the constant force springs, or a combination of the 2 if necessary.
maybe it is to use a titanium plate and move the steppers to the frame and then the weight won’t be an issue. Either way it is challenging problem.
Anything you do to ‘harvest’ the energy will result in less braking torque.
Just shorting the motor coils will produce the highest torque opposing the fall.
I’m 100% confident that the e-brake can be easily designed and made and should be about as reliable as possible. It’s really just nailing down the criteria to trigger the brake and making sure that this covers enough situations as to be reasonable.
Just basing it off Vmot and the enable line is probably enough to catch the majority of situations with close to 100% reliability.
That was for all three combined, not a single stepper.
Not doing both. Those pulley sets are not cheap, it is cheaper to switch to wobble protection if that was the case.
I agree.
We will see if the klipper macro pans out at all, that would mean we only deal with power failure.
Sorry, Wobble prevention, e-brake, or constant tension spring.
I would have expected the tooth radius to be the important ratio, in which case 80:20 translates to 4:1
I just happen to have a few 252mm looped belts here, they were supposed to be for a diffeent project… but now I’m curious…
I won’t pretend like I’m an expert in this, so someone can correct me if I’m wrong/misremembering…
Gear reduction is only related to speed.
Speed and torque are inversely related.
Torque is based on the moment force, in which the radius of the pulley is what drives the reduction ratio
Now that being said, I do find it odd that the tooth count ratio and the circumference ratio are different, but I was just going off of drawings in one of the listings.
A safe bet would be to just assume 4x based on the tooth count, but I would assume for proper calculations, an engineer would be asking for the radius of the pulley.
I do think that is what matters, the radius is probably 4:1 if you get the exact tooth midline.
Man you guys are making my head hurt. 
I bet that’s why they do the gantry instead of the bed. I can’t imagine a 350x350 3/8” MIC6 bed and heater being light at all. But I could see 5 lbs being plenty to hold the gantry up
Everyone is making it more complicated than it is. The pulley tooth count is what matters. The belt is a constant, and the pulleys have matching teeth cutouts. The mechanical ratio is tooth count to tooth count, The radius of the pullies are driven by the tooth count and shape.
Another way of saying that is that each revolution moves each pulley a specific number of teeth. Always. (Unless you don’t have tension and the belt skips or other failures)
I really think the simplest thing is to design a suitable and simple e-brake circuit. That could be in a carrier module to support legacy boards (e.g. SKR or early jackpots) or built into future versions of the jackpot as a standard feature.
agreed!
Are we allowed to be of topic in this thread?
I’m honestly suprised vendors are still making boards that can be killed by back driving steppers.
What we are finding is you still can kill it, but it takes a lot more. JJ’s printer can handle a little more than 8lbs dropping on three steppers, but 12 gets it over the top. So the chip can probably handle one stepper no problem, probably even 2, that third one is just taking it over the top.
Thank you!! Shows how much of our current weight is the steppers.
Okay so I actually weighed one of mine last night as well. I got about 3 lbs for a 200x200 V4 bed assembly still on the printer. When weighing everything separately, I got between 4-5, so in my mind the 3 rails and the 3 steppers’ friction/detent hold more than 1 lbs, less than 2.
Does your small bed drop when power flashes? or is it just a slow decent?
I really need to pull mine off and do something different with that bottom plate. Either cut a bunch of weight out of it or just remake it out of MDF. See what kind of difference that has
The constant tension springs are great, but they are HUGE. I still haven’t found a good way to install them that will be out of the way of everything and be in a good spot to actually work.
Pretty fast, I def start to get power.
Carbon Fiber! Might as well wait now and just build the new one.
I have some here that are like 7lbs pull and they are about the size of a quarter I think. I’ll try to find them they were for a project a long time ago.
Yeah that’s defiantly not what I got LOL. That’s what I get for ordering at midnight and only looking at the weight and not the other specs lol
Okay, initial post, some of this might change but they have been here so long they have dust on them. Sorry ORob!
