Thermoforming a shallow cone in the bottom of a poly drum

[FuelMaker]

I had an idea for heat forming a shallow cone in the bottom of my new HDPE drums and I'd like to bounce it off the experts here.

The idea is:

- Make a sand tray and form a shallow cone or bowl in wet play sand.
- Set the drum over the hollow.
- Pack more wet sand an inch or two up the sides.
- Heat up veggie oil to exactly 275F (260-280 is supposed to be the optimum forming temp).
- Pour an inch worths of hot oil in a funnel down through a pipe (to avoid splashing the sides).
- Remove pipe/funnel and watch the bottom soften and sag down into the hollow.
- When its finished forming to the hollow drop an icecube or four into the oil (covering the drum mouth to avoid the spatters from the boiling oil/water)
- Let it cool down to room temp
- Clean and install a stainless 2" drain bulkhead fitting at the lowest point.

I'm thinking as soon as the plastic touches the wet sand it'll cool below its sagging temp, and the wet sand up the sides should keep the sides from softening and collapsing the drum. I'm hoping that even though the oil would cool down a bit the moment it touches the cool plastic it wouldn't go below 260F.

I was thinking of using hot air or a torch but I couldn't think of a good way to keep from spot overheating and the heat getting to areas where I wouldn't want it. Then I thought of the oil as a way to have exact temperature control and keep the heat only where I want it.

Of course since the bottom wouldn't be flat any more the drum would need a support stand to hold it and the drain pipe.

Thoughts? Anybody able to poke holes in the idea?

Thanks!

[FullySilenced]

Well make your forming cone out of something that is air tight pull a vacuum on the bottom of the drum and then add your hot oil... suck that puppy down to the form....

[FuelMaker]

Heh, I'll might try that if just the hot oil doesnt work. I also thought of pouring in 280F sand after the oil to force the plastic down into the mold if it doesnt want to move on it own.

I'll let you know how it works out.

[Badmotivator]

One more idea. Make a funnel shape out of cheap sheet metal that is the same diameter as the bottom of your bucket and has the pitch that you want your bucket bottom to end up with. Put it down into your bucket, and then run a hair dryer or heat gun on it. Every once in a while push straight down with a stick.

The steeper the pitch you choose, the thinner the plastic will end up. Careful there.

[soy_boricua]

Pardon my ignorance but what is the cone shape for?

[Worm_Drippinz]

I'd bet he wants to make a "conical" fermenter.


It's going to have to be perfect to get the bulkhead just right.


I don't see the wet sand method working.


If you have access to vac molding equipment you should know better.

I have a friend that works for club car making accessories and I have access to millions in gear.


Never thought of making my own. Seems like to much trouble.

I'm with using the professional equipment %100 as bad said and figuring out the mold of you have the equipment.


That in a sense seems like a no brainer instead.

[FuelMaker]

Because I want a full drain fermenter, and the commercial polypro cone bottom 55 gal tanks start at $300 (including shipping) and go up from there, and I got my square HDPE screw top for 40 bucks and it was local. And making my own is fun - I'm a tinkerer by nature.

I think I'm probably going to combine the sand mold with the vacuum forming. The sand lets me mold the shape easy and exactly how I want it and the vacuum ensures it gets pulled down into the mold. I'm also going to mix in some diluted PVA glue in the sand and let it cure so it's a rigid mold, expose a 4 inch wide circle on the sand tray plywood, drill a bunch of 1/8" holes in it and hook up the shop vac to the underside of the sand tray.

I'll use modeling clay to seal and support the tank rim at the mold junction

I don't need a deep or steep cone, just enough that it'll completely drain.

Example pics (not mine):

[Badmotivator]

This sounds fun! I think what you're doing sounds cool and I'd love to see what you come up with.

[shadylane]

I'm too cheap to buy a conical fermenter also.
So I'll be watching to see if your successful.

[FullySilenced]

Well make your forming cone out of something that is air tight pull a vacuum on the bottom of the drum and then add your hot oil... suck that puppy down to the form....


I am sure i suggested something that would work for you.... but...

Happy Stillin

FS

[Worm_Drippinz]

I was thinking on this more last night.



If you do try the heated oil, try using a wood dowel to push the heated plastic bottom down that's bigger in diameter than the fitting you want to install.

That I think that will work and it won't have to be perfect.

[NineInchNails]

I know this is an old topic, but I'm really curious to know if anyone has successfully done this.

I'm thinking about trying this, but I'm a bit skeptical as to whether I could achieve enough of a cone to be effective enough to make this worthwhile.

I'm considering making a 2x4 or plywood jig to hold the top of the drum and use a 2x4 with a round plywood disk to force the bottom of the drum straight down.

[Jack C]

Well I would be really interested to see if it worked. If you try it please let us know.

[seabass]

Only one way to find out. I think you'd unevenly thin out the plastic though. I doubt the material is thick enough to allow for that much stretching. Worth a try though if you have an extra barrel lying around. You'd have to make a base for it though.

[NineInchNails]

I certainly will post pics if I do this. Drums are pretty tough and should be able to lose a bit of thickness. I do have a couple extra drums that I have cut the top off of already so I will probably try it with one of those first. I should be able to recapture the oil so it can be reused on the next one.