11 replies to this topic

[ElsieD]

I just read an interview with Duncan Werner, maker of the SideKic. In the interview he indicates that he is thinking of trying to build an affordable chamber vacuum. Anyone know anything about this?

[kryptos1]

Decent discussion going on here:
SideKIC Thread

[ElsieD]

Yes, I know and I have been following that thread. What I am interested in is whether anyone knows anything about the chamber vacuum he talked about in his interview.

[kryptos1]

Duh......read too fast and didn't 'read it'....fire fighting mode at work today. Interested in this as well, the SideKIC works great and has been running for 3 days strong now.

[ScottyBoy]

Just like the Sidekic, he stands to make a lot of money if he can roll out an affordable one...

[dcarch]

It will be possible.

Start out with a tire pump, which is also a vacuum pump, that's about $20.00.

A heat sealer, $20.00?

A box with seal and a clear top, $30.00?

Switches, valves, etc. $15.00?

dcarch

[kryptos1]

Last time I did something like that the prototype and final plastic molds alone were about 3K, packaging can eat $8-12/ea (low end) into the margin, Amazon will want their 15%, hard to get any pricing scale in the beginning in case something goes wrong, etc.... I am curious if someone has broken down one of the nicer high end ones and see if it could be redesigned for afforability

[KennethT]

Part of the problem of a chamber vacuum is designing a "box" that will withstand the high pressure of a decently strong vacuum. Materials significantly strong/thick enough to withstand this pressure at a decent size is not that cheap.

[emannths]

Part of the problem of a chamber vacuum is designing a "box" that will withstand the high pressure of a decently strong vacuum. Materials significantly strong/thick enough to withstand this pressure at a decent size is not that cheap.

Really? A vacuum is at most 1atm/14 psi. It's pretty easy to withstand that, especially in compression, isn't it? I'm sure the polycarbonate of a Nalgene bottle could do it. I think the challenge is to create reliable, low-maintenance pumps and seals.

[Mark Muller]

Part of the problem of a chamber vacuum is designing a "box" that will withstand the high pressure of a decently strong vacuum. Materials significantly strong/thick enough to withstand this pressure at a decent size is not that cheap.

Really? A vacuum is at most 1atm/14 psi. It's pretty easy to withstand that, especially in compression, isn't it? I'm sure the polycarbonate of a Nalgene bottle could do it. I think the challenge is to create reliable, low-maintenance pumps and seals.

The problem gets more difficult/expensive as the size of the chamber increases. This is because the loads increase with the surface area of the chamber. You also lose the help from making the walls curved as the chamber gets bigger, as the curvature of circular walls is inversely proportional to the radius. One more thing is the direction of the loads is such that it wants to buckle the chamber loads - not a problem with a bottle that is pressurized on the inside. For a natural example, check out the thickness of an ostrich egg shell versus a chicken egg.

[mgaretz]

Duncan - look into the possibility of creating an add-on chamber with sealer that uses the vacuum of a Foodsaver or similar that has an external vacuum port. That eliminates the cost of the vacuum pump and I'll bet 80% or more of the target market already owns a clamp sealer. There will be those that say the Foodsaver doesn't pull a good enough vacuum, but again I beleive the target market doesn't want to make watermelon "meat" and really only wants to vacuum liquids for Sous Vide or storage and the Foodsaver is plenty good enough for that.

I'd suggest an external box that holds the entire Foodsaver (elevated) and a mechanical means to press its buttons (so you are not even including a sealer or anything electrical) but that would limit you to certain models that fit. Then again, maybe that would work for many models if you pressed start, closed the box lid and hoped the internal vacuum sensor that ends the cycle and seals would activate correctly. It eliminates the mechanical button pushing and makes it easier to accomodate multiple models/brands of sealer. Might need to make the sealer intentionally leaky so the chamber sees the vacuum, but that coould be as simple as removing one of the gaskets.

Edited by mgaretz, 19 March 2012 - 03:55 PM.

[KennethT]

Part of the problem of a chamber vacuum is designing a "box" that will withstand the high pressure of a decently strong vacuum. Materials significantly strong/thick enough to withstand this pressure at a decent size is not that cheap.

Really? A vacuum is at most 1atm/14 psi. It's pretty easy to withstand that, especially in compression, isn't it? I'm sure the polycarbonate of a Nalgene bottle could do it. I think the challenge is to create reliable, low-maintenance pumps and seals.

The problem gets more difficult/expensive as the size of the chamber increases. This is because the loads increase with the surface area of the chamber. You also lose the help from making the walls curved as the chamber gets bigger, as the curvature of circular walls is inversely proportional to the radius. One more thing is the direction of the loads is such that it wants to buckle the chamber loads - not a problem with a bottle that is pressurized on the inside. For a natural example, check out the thickness of an ostrich egg shell versus a chicken egg.

Right... just to illustrate a little more, if you have a chamber that's 11x15x8 inches, then for one wall (say the 15x8) you'd have 120 square inches, so at 14psi, that would equal 1680 pounds of force that the wall would have to resist against. While the material itself will have no problem (like your nalgene bottle), you'd have to have a very strong wall and joints that will resist buckling under that kind of force.