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updated readme to include updated BOM

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laura 2026-06-19 10:50:06 +00:00
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@ -41,11 +41,17 @@ Price per order/number of units|price per unit|
* 10,79€/5 = 2.16€
* 9,67€/5 = 1.94€
* 3,11€/5 = 0.63€
* 32,99€/5 = 6.60€
=11.32€/unit = 13.12USD < 14USD (as of writing this)
* 22,99€/5 = 4.60€
=9.32€/unit = 10.68USD < 14USD (as of writing this)
and youd be left with with 60 dowel pins ("worth" 5.80€) and 875g of PETG (worth 28.86€). This is PPU particularly high because of the expensive filament used in the calculation.
I think a fair cost assesment is somewhere inbetween the two, since most people will have some filament, and so the 6.60€ per valve of filament are a bit over the top. I think the average maker would probably spend around 5-6€ per valve.
I think a fair cost assesment is somewhere inbetween the two, since most people will have some filament, and so the 6.60€ of filament per valve of filament are a bit over the top.
* 10,79€/5 = 2.16€
* 9,67€/5 = 1.94€
* 3,11€/5 = 0.63€
* 22,99€*25*5/1000 = 0.58€
=5.30€/unit = 6.08USD < 14USD (as of writing this)
a
## Performance Assesment/Concerns/Room for improvement
I have not had the opportunity to test maximum holding and closing pressure, nor how many close/open cycles it can handle. I hope to get around to running those tests in the final week before the submission deadline. [The only test I've managed so far](https://chaos.social/@la/116727325081926518) was me blowing into the tube with the other end in a glass of water, to see if it closes and seals agains my lung pressure.
@ -55,4 +61,4 @@ I am particularly concerened with the requirement in the contest brief, requirei
I belive my valve is likely to hold a seal at those pressures given that the servo sees none of that force, it's directly pushed into the housing. I am however woried that it might not manage to close against that kind of pressure.
And, wear wise, the entire valve has no roller bearings. It runs entirely on dowel pins in drilled out holes. This works pretty well, but I could imagine some of those holes deforming or wearing over time, especially when running unter pressure and thereby bigger forces. I am particularly worried about the pivots of the bell crank, which take the forces of the sqished tube directly.
The second worry point for wear is the tube itself. Because of the top-dead-centre design aproach the pin rubs along the tube quite a lot. This, I imagine, could wear the tube itself down over time. Some lube would certainly go a long way there, but adding a roller bearing to the contact side of the bell crank would eliminate the problem entirely. Same would be the case for the pivot holes. This would increase the BOM by about 3-4€, which arguably would be worth it. I will have to test if the wear gets to be a problem in the first place, and then, if it turns out to be worthwhile I might add a variant of the design which solves this problem using 682 bearings (which I have, just in case, ordered already)
The second worry point for wear is the tube itself. Because of the top-dead-centre design aproach the pin rubs along the tube quite a lot. This, I imagine, could wear the tube itself down over time. Some lube would certainly go a long way there, but adding a roller bearing to the contact side of the bell crank would eliminate the problem entirely. Same would be the case for the pivot holes. This would increase the BOM by about 3-4€, which arguably would be worth it. I will have to test if the wear gets to be a problem in the first place, and then, if it turns out to be worthwhile I might add a variant of the design which solves this problem using 682 bearings (which I have, just in case, ordered already)