Fabricator is right, these things can be scary when you understand the equivalent mass that gets stored up in the rotor when filled and at full speed; it can easily run into 100,000+lbs equivalent.

None the less,
Dkenny it seems to me your idea has merit, if the youtube guy can use just plain old wood then fiberglass reinforced multi-ply wood should work very well at the RPM's you are suggesting. Just build a good blast/oil-collection container just in case there ever were an "issue"

I was..at the moment I'm thinking a double containment..first 3/4 plywood the second either 1/2 plywood with a gap between the 2 or place the whole thing inside a steel drum..I like the steel drum best but haven't worked out all the details...

-dkenny

I bet even 1 layer of 1/2" ply is way stronger then a flimsy 55g drum.
Jon

quote:

I bet even 1 layer of 1/2" ply is way stronger then a flimsy 55g drum.

Yeah, when you think containment like this, like stopping projectiles, you have to think absorption and dissipation of energy, not strength. A steel drum with some insulation and then a wire mesh around it would be pretty effective. Fluid tight in the drum, dense insulation to absorb and strip energy from a projectile, and a steel mesh to catch and stop the final bit of momentum through stretching.

Good points Ryan.
Have you spent much time thinking about target building?
Jon

so does depend on projectile..I have seen an arrow shot from a compound bow go right through a 3/4 sheet of OSB..

I'm still trying to work out how to verify the balance..I know I can make it round and run true but that's not the same as balanced..I can spin it fast on the lathe..this isn't as bad as it sounds if if out of balance.I had the lathe move and had a piece break off..just spin and moved..no major damage.

maybe just buying the rotor is the safest choice..but I want to try..

-dkenny

You could take it to a tire shop and have them throw it on the balancer. If they can attach it to it...
Too bad your not closer, my neighbour is a mechanic and has in own business complete with a nice new Snaped On tire balancer...
Jon

quote:

Originally posted by dkenny:


I'm still trying to work out how to verify the balance..I know I can make it round and run true but that's not the same as balanced..
-dkenny

Its not, but it does get it pretty close, dont buy a rotor, try making the one you have been talking about; Ive been looking forward to seeing your finished piece.

Run it up to 3600 rpms, and put a little water in it, you will know immediately if it is out of balance, I believe it is likely impossible to build a fuge this way, the inner wall MUST be perfectly concentric to the motor shaft, even a few thousandths of an inch will give you slight cam shaped effect, the liquid will be thicker in the off center region and cause a dangerous out of balance condition.
I can't see wood being suitable to this application at all, any movement of your bowl to motor mounting holes, (and there will be) will be pretty much catastrophic.

Normally I would agree but there is a vid on youtube of a fellow using wood at 3500RPM without any issue. Dkenny is talking about using the same idea and fiberglass reinforcing the rotor while at half the RPM.

If cut out properly on a lathe it should be dead center.

The water idea is a good one. We also ran an indicator on the outside of my steel rotor to check for any possible out of round on it.

The outside is really not the important place, the fluid runs on the inner diameter, you can balance a fuge bowl until it is absolutely perfect, but, balance will not indicate a inconsistency in the concentricity of the inner diameter and the motor shaft center, this situation will balance when dry, however, when the bowl is filled with liquid it creates and entirely different balance situation, a very small inconsistency will be magnified several hundred time by the rpms involved.
Reducing the rpms is counter to what you are trying to do with a fuge, I'm not sure 1800 rpms would even be worth the trouble.

quote:

Originally posted by fabricator:
The outside is really not the important place, the fluid runs on the inner diameter, you can balance a fuge bowl until it is absolutely perfect, but, balance will not indicate a inconsistency in the concentricity of the inner diameter and the motor shaft center, this situation will balance when dry, however, when the bowl is filled with liquid it creates and entirely different balance situation, a very small inconsistency will be magnified several hundred time by the rpms involved.
Reducing the rpms is counter to what you are trying to do with a fuge, I'm not sure 1800 rpms would even be worth the trouble.

When cutting the rotor the outside and inside are cut one after the other, basically the interior diameter should be near the same as the exterior cut. If the indicator shows an out of round on the outside, it would be safe to assume there would be a corresponding out of spec on the inner wall.

Also if the motor shaft is out of center then it would have a proportional out of center to the inside diameter. Now of course this all assumes you have a good lathe and know how to use it properly.

1800 RPM might not be the ideal speed, but would still push some pretty hefty G's. GPM drops, but would still be fine for any homebrewer.

Keep in mind that a 10" rotor at that speed will still produce nearly 900 Gs, not too shabby and not far off from the very popular 'simple centrifuge'.

You are absolutely right about keeping everything spot on, these units can be very dangerous with even a slight out of round. If one side of the rotor held even just 1 ounce extra of fluid that equates to a 200lbs+ out of balance on my unit.

This becomes even more apparent when you take into account that the 200lbs+ out of balance is rotating 60 times per second. This can wear out even the toughest bearing sets in no time and can cause catastrofic failure.

In other words (attn Dkenny) you might want to wear a cup for the first test

fabricator,
that's what the epoxy is to help with..alteast keep the oil from soaking into the wood. it should also make it stronger. since I using plywood it should be easier to get to round. I know turning a wood bowl the grain can make it difficult to get round.

If I hadn't gotten sick I might have this done..I just need 2-3 more layers of 3/4 ply wood for the base. I'm not putting a top on it yet. the top will another layer glue to the top and turned with the whole mess..I have a fixed plate that I'm going to screw to the bottom for turning. this will all me to put it back on the lathe as needed

I plan on sharing the results..maybe to encourage/discourage other from trying.

-dkenny

Dkenny, you get anywhere on your rotor yet?

I have it all glued and the outside turned..turning dry plywood it hard and slow.

-dkenny

I have turned the inside..

it took a while..
still out of balance..but at 3K+ rpm..on the lathe..it was OK..now if I had an extra lathe I wouldn't worry about it..not at all..

so I mixed up some epoxy, techincaly polyester resin, and poured in on the inside..spun the rotor..at the moment its drying. I might add another layer..either way..this should balance the unit. like a washing machine..i'd like to add some with fiberglass to the outside..but I'll see how this is doing first..

Ideally a DC motor would be best since one could vary the speed for the the best balance..just a thought..not to mention the slow start up..


-dkenny

You can actually get a really cool speed controller for AC motors as well.
The one I'm testing from WVO Designs has one and I can vary the speed from 150 RPM's clear up to 6,000 RPM's just by rotating the dial.

I shot some video of it in action.
http://www.youtube.com/watch?v...feature=channel_page

It comes from DirectLogic.

There are lots of ac speed controlers available, the ones for motors up to 3-4hp are usually fairly inexpensive.

Graydon, that is one pretty centrifuge

6000RPM!?! That little sucker has to be pushing some serious G's!

How much is the motor controller? I plan to add one to both my prototype and new centrifuge, it can be a good way to reduce motor HP since it can be 'soft' started. Ive been running a 3/4hp on the 10" at 3450RPM and boy is that thing getting worn out.

I have to use a buffing wheel with a rubber disc to spool it up to half RPM before plugging it in, it would never be able to start on its own

The one that's with my motor is from Automation Direct and is a GS1 Series Drive.
http://www.automationdirect.co...ng/Catalog/AC_Drives

I'm not sure which exact model it is though.

I love using it though. It's a heck of a lot of fun to vary the RPM's.
I shot a bunch of video the other day that shows centrifuges in action that I'll be posting shortly.

-Graydon