torture testing the doser revealed a pretty critical issue 🫠

okay if I knew there was this much interest in this i wouldn't have recorded this while propping up my phone on my waterbottle

I hope the new design works cuz if not FUUUUUUUUUUUUUUUUUUUCK

for real.... I have a few last ditch solutions in my back pocket to save this run but they really aren't my favorite >.<

Is there space to put a chamfer on that edge so it can compress the tube over a slightly longer time? Or make the front part of that circle wall a bit wider so it gradually compresses

i went with the first idea! at the end of the video you’ll see i added a fillet

softer rollers could be a option or flexablity in the holder itself would help reduce damage to the pipe and may require less force as its more compliant to the movement at the pinch point

compliance is defo an option, softer rollers would be an elegant solution but the softness of them would need to be experimented. we don’t want them to be so soft that they are unable to fully compress the tubing. i feel that this fillet would be the most cost effective in the short term. compliance in some form (springs come to mind) is a big point of experimentation for any next version though

indeed may i ask how you have calculated the amount of ''squish'' that is required because something that may have been overlooked is trying to squish to the full extermal OD and is fact you only need enough foce to squish the inner diameter as the walls of the tube close the gap

i may have slept on the idea haha i dont even know what is this for? :D

haha this is for a peristaltic dosing pump for reef aquariums! and yes, I took into account only squeezing the inner diameter, that is a total of 3mm inner diameter, meaning the space between the rollers and the wall should in theory be 2mm (1mm walls * 2 sides of the circle being compressed). Though, because of tolerances, wear and such like, I am trying to squeeze a little more than 2mm to give me some margin to prevent losing occlusion and all the fluid draining backwards through the line

Mechanical engineer here. Potential other solution for the torque would be a small gear box to increase the torque slightly.

this is what ecotech does, and it’s possible. the problem is that id need a slim planetary system. the primary reason i went for direct drive is for precision and longevity. the less things that move the less things can break, moreover, backlash can play a role on precision

True true. My original thought was that instead of a radius, you make the wall tangential to the circular path so that as the wheel turns, it gradually comes in mor contact with the tubing.

yes that’s an option, but that would require a pretty steep angle (i think 30 degrees from the lateral line) and means i’d have to put the connectors on an angle too. it’s certainly possible, and at least 1 company does this, but it would require a redesign of the tubing connector section.

Do you 3D print the housing? The finish looks really good

i didn’t! i used a technique called MJF. it’s technically 3d printing in that it’s additive manufacturing with a cnc machine but it’s much better in many ways to traditional fdm printing

Worst case scenario, would reducing the lengths of your spokes help with the issues you're facing? Atm it seems like the issue is that there isn't enough clearance so there's an extremely high amount of resistance during operation

yes! it’s a bit of a last resort option as shrinking the spinner diameter would cut into my occlusion margin. ultimately, the clearance issue is just on that transition so i’m really hoping the fillet will fix it.

why not just get a cheap ots peristaltic?

because taking pre-made peristaltic pumps and essentially flipping them is not really what I want to make, nor can I really compete with the other companies who are already doing that at the scale I could never match. I want to make mid range dosing pumps that are better than the over the counter ones but not outrageously expensive

Hi baby , so for that tubing you could use food grade silicone tubing they are much more flexible and softer

this is 50a hardness silicone tubing! i would use something like 40a if i could get my hands on it, but its hard to find without paying for a custom run

yessssss thats what im here fooooor

I was going to suggest exactly the change you made, so hopefully we're both correct ^.^ maybe strength in numbers can help build some confidence that you aren't totally cooked yet atleast !

Whats this for?

my reef dosing pump i’m draining and selling :))

I'm not a mexhincal anegoneer but would making the roller concave help?