Centrifuge...

[AdeV]

I've finally sorted out a source of free used veg oil.... which means I will soon need to be centrifuging said oil to make nice clean oil for the Lister...

Being a cheapskate, I planned to make my own. I'm thinking of using an old car brake drum as the rotor - but it's cast iron & I know CI is not so good under expansion forces. I reckon that, assuming a car with 36" diametert wheels including tyres, at 150mph, the brake drum would be doing around 1400rpm. But I want to drive it at >2500rpm... will it hang together, or should I make one out of aluminium instead?

Cheers!
Ade.

[Jens]

What I would think about is that I have to contain shrapnel with the outer casing. It would be a pretty massive/heavy unit if you start with a heavy rotor.
Another thought - will a brake rotor be balanced enough for this new operation? It only requires a crude balancing for the car. I don't know the answer, I am just throwing things out ....
I ended up buying the rotor and building the rest.

[AdeV]

What I would think about is that I have to contain shrapnel with the outer casing. It would be a pretty massive/heavy unit if you start with a heavy rotor.
Another thought - will a brake rotor be balanced enough for this new operation? It only requires a crude balancing for the car. I don't know the answer, I am just throwing things out ....
I ended up buying the rotor and building the rest.

The explosion thing was what I was worried about. Wondering about welding a steel band around the rotor...  Balancing might be less of an issue than you think, I'm saving up for a crankshaft balancer at the moment, I'd be able to balance it on that...

[Thob]

I've thought about welding up a short section of steel pipe to a steel plate, along with the coupling at the bottom to the motor shaft and a second steel plate with a large hole in it for the top.  Yes, it's going to have to be balanced, but 3600 RPM isn't really all that high in my mind.  I've static balanced a couple of items and they ran very smooth.  I also plan to balance by "adding on" rather than "taking off" - i.e. welding beads onto the "light" side rather than grinding off the heavy side.  You can use a few magnets added at various places to get an idea of how much material needs to be added.

[mike90045]

welding a steel band around the rotor.

That would hold the pieces together for a while, but I suspect the parts not welded firmly, will still detach, the rig gets way unbalanced, and we read the rest in the papers.  +2,000 rpm is pretty dense energy

[Jens]

The explosion thing was what I was worried about. Wondering about welding a steel band around the rotor... 

As you mentioned, a brake drum is made from cast steel. It is then heat treated. I would be very careful welding anything to it where the result could be a change in the physical structure of the steel. I am thinking that small spot welds are probably ok but large beads would be a no no ...
Thinking about the base question a bit further, a brake rotor also needs to withstand the expansive forces of the brake shoes and I think it always has a re-enforcing rim on the open end .... maybe do a test run at something like 1.5 or more times of your target speed from a safe distance and if it works call it 'good enough'. I wouldn't be comfortable with that but you might be ...

[billswan]

Jens

You mentioned you built one. What did the store bought bowl cost? Do you have a Brand name possibly?

In the last few days I have come to the conclusion that a centrifuge might be needed as some of the WMO that I collect for my waste oil furnace can be real crap. Most guys I get it from do real well keeping the garbage out but I just picked up a 80 gallon batch that has some real fine debris in it that will plug up a diesel fuel filter way to fast.

Billswan

[bschwartz]

I've had GREAT success with a dieselcraft centrifuge.  I powered my first unit with a carbonator pump from flea-bay.  I also have a dieselcraft copy that works just as well.  Thousands of gallons of WVO has paid for all my parts many times over.

You might save a bit of money making your own centrifuge, but it will cost you a bunch of time and stress (will this thing blow up?!?!?).

A reasonably priced setup could be made with parts like this:

http://www.ebay.com/itm/MCCANNS-E400397-CARBONATOR-SODA-CARBONATION-PUMP-1-3-HP-MOTOR-/380795181981?pt=LH_DefaultDomain_0&hash=item58a9295b9d

http://www.ebay.com/itm/65-GPH-CENTRIFUGE-for-WVO-OIL-and-BIODIESEL-/121057829074?pt=LH_DefaultDomain_0&hash=item1c2f9be0d2

A gear pump will last longer, but for a cheap way to start and see if centrifuging will work for your application, these will work.

[Jens]

I started with a Dieselcraft clone (or the original that the Dieselcraft was copied from) It was a centrifuge in an over-the-road transport truck. It was the same size as the largest Dieselcraft. I ran it with a 3 Hp motor and a gear pump at something like 120 PSI. It's been a long time and my brain doesn't retain the details all that well but the net effect was nice looking veg oil that would plug up a very large diesel fuel filter after about 40 gallons had run through the filter. The filter was 5 micron and the filter element enclosed maybe about 1.5 litres of volume - it was a VERY large pleated filter. (Racor 1000 series)
I am not sure but I don't think the filters looked plugged but they definitively were.
The next iteration for filtering used the upflow method. The output of that was about the same quality as the fluid powered centrifuge.
My last and final filtering effort was with a motor powered centrifuge and although the output looked like all the previous stuff, the filter never plugged again.

Now some people may say that I shouldn't have bothered with a 5 micron filter and that 10 or 15 microns would have been fine .... what can I say ,,,

[Jens]

Jens

You mentioned you built one. What did the store bought bowl cost? Do you have a Brand name possibly?

In the last few days I have come to the conclusion that a centrifuge might be needed as some of the WMO that I collect for my waste oil furnace can be real crap. Most guys I get it from do real well keeping the garbage out but I just picked up a 80 gallon batch that has some real fine debris in it that will plug up a diesel fuel filter way to fast.

Billswan

I believe the bowl came from these people:
http://www.wvodesigns.com

I run it with a 3 phase motor for controlled acceleration and deceleration as well as a very large speed range. I also have one of their pre-heaters on it although it is quite different from what they show now.

[bschwartz]

I just don't seem to clog filters Jens....
I wonder if our centrifuging methods were different.

I put about 50 gallons in a drum,
Heat it to 180 degrees F
Turn on the centrifuge and allow oil to be sucked by the pump from the bottom of the barrel,
through the centrifuge, and then dumped back in the top of the open barrel.
As I am powering my setup from my witte generator (running WVO), energy isn't a concern.
I allow the looped oil to clean for approximately 24 hours.  YES 24 hours.  That may be why my filters don't clog.
OR..........
Maybe I just get better (cleaner) oil from my restaurant then you, and my centrifuging is overkill.
I just know that I've run thousands of gallons in my vehicles, and I change fuel filters about once or twice a year.
The only time I've had to change a known filter clog was when I got a bit of hydrogenated oil that was too thick when it cooled down.

[AdeV]

The explosion thing was what I was worried about. Wondering about welding a steel band around the rotor... 

As you mentioned, a brake drum is made from cast steel. It is then heat treated. I would be very careful welding anything to it where the result could be a change in the physical structure of the steel. I am thinking that small spot welds are probably ok but large beads would be a no no ...
Thinking about the base question a bit further, a brake rotor also needs to withstand the expansive forces of the brake shoes and I think it always has a re-enforcing rim on the open end .... maybe do a test run at something like 1.5 or more times of your target speed from a safe distance and if it works call it 'good enough'. I wouldn't be comfortable with that but you might be ...

Hmm, true, the brake pads would push out at, potentially, quite a considerable pressure.... that does make me feel better about things. Also, cast steel you say? I thought they were cast iron (which has problems with tension forces), cast steel should take the tension of being spun at high speed with no problem.

I do plan to build an enclosure (obviously), I can probably get some 5mm (3/16") steel which should contain any shrapnel. Drive speed would be whtever the motor runs at, I don't really want to have to make a gearbox too... I can test the drum I've got on the lathe to see if it's iron or steel. Balance weights would be mechanically attached (drill/tap and affix by screw an oversized lump of steel, which I can then cut down to balance).

[Jens]

The drum will machine as cast iron because of the heat treatment.
I don't recall where I read that it is cast steel but I recall melting a drum, recasting it as something else and having an un-machinable lump of steel on my hands that ate carbide inserts as if they were snacks.
It also makes sense when you think about the use a brake drum is put to.

[vdubnut62]

Hmm, I thought they were steel with a cast iron inner wear surface. Just think about the thin outer face that slides over the wheel studs and axle, it's thin, soft and will bend.
Model A Ford drums machine like solid steel.
Ron.

[fuelfarmer]

I never used a multiple pass CF, but I do not like the idea of running clean oil back into dirty oil until you get most of the dirt. How long, or how many passes would you filter dirty water using this method before you would take a drink?

Having said that, the classic open bowl CF is not that good either. To get a good cleaning job you need to control how and where the oil enters the bowl. I spent some time playing with an open bowl to see if I was getting some visible particles splashing out of the bowl, or was the oil not staying in the bowl long enough. Turns out splashing and low retention time were both problems.

Here are some youtube clips that will show what I am talking about.

http://www.youtube.com/watch?v=1X7Lr-gdxZY

http://www.youtube.com/watch?v=DIZT-jmyphs

In this clip the feed cone system is an older style. Even better feed systems are available now from Simple Centrifuge and other suppliers. I just happen to like the guys at Simple Centrifuge and I think they were the first to offer the feed cone.   

http://www.youtube.com/watch?v=fTOUHf87uHY

Building your own can be done. But it is not as easy as it would first appear.