The Boys' Bugle

A Christian magazine for boys featuring things of both a spiritual and physical nature.

Sunday, January 06, 2008

More on the centrifuge rotor...

I didn't have any good pictures of the centrifuge rotor on this site before. I still don't have a picture of the rotor all put together when it's out of the centrifuge frame, but I'll post what I have. These pictures where all taken while I took it apart for cleaning the dirt out. My brothers had run about 700 gallons through it the day after I ran it. They didn't heat all the oil over the boiling point. When I drained it, I got 1 to 1 1/2 gallons of water out of it. I was amazed how much water was in it. I was pleased. I like how it's working.

The rotor sitting on top of the centrifuge. I took an almost 30 inch section out of a 9 inch OD oxygen tank and machined the ends square.

The top end plate. Notice the holes where the oil spins out of and the weights added to balance it. There is a nut that clamps the rotor together. There is a groove for the oxygen tank to sit into the end plates. Of course there are line up marks so it can be assembled correctly to maintain the balancing.

The rotor before it's cleaned out with the top end plate, the clamping nut, the oil catching pan, and the top bearing removed. The top bearing is held on with two bolts and the oil catching pan is just sitting in there. It only takes a few minutes to take it apart.

Looking down into the centrifuge frame with the rotor and the hopper for catching the oil removed. The center shaft is still there.

The bottom end plate with drain plugs and the center plate for a baffle and support.

The bottom end of the center shaft. Notice the collar for the bottom end plate to sit on, the bearing surface, and then the smaller part for the motor drive coupler to fasten to. You can almost see the holes where the oil comes out the the shaft and into the bottom of the rotor. Actaully this picture is a picture of my old center shaft that is slightly bent. It's only a few thousands off. Sometimes small things matter.

A picture of the whole center shaft with the top at the top of the picture. This is also a picture of the old shaft and wasn't taken the day I took the rest of the pictures.


  • At 2:14 PM, Blogger Melvin Martin said…

    Here is a letter I recieved and my responce (with some additions) that I thought should be added to this post.

    Hi Melvin,

    I love the centrifuge! Can you post some more design details, please?

    How is the shaft constructed. It isn't all one piece, is it?

    How did you figure the length of the rotor that you wanted? All the
    others I've seen have been much shorter.

    Do the top and bottom plates interlock with the rotor or are they just
    sandwiched together?


    Grant Simmons

    Hi Grant,

    Sorry for taking so long to respond. You probably gave up on me by now. I’ve been occupied with many other things.

    Yes, the centrifuge shaft is many pieces. It was very time consuming to make. It is made of four different pieces. I made the pieces, welded them together, and then finished machining it. The first shaft I made got warped when I welded it, so the second one I machined it to size after I welded it. If I were making another one, I’d make the shaft bigger and use bigger bearings. I used a 25 MM ID radial contact ball bearing for the bottom and a 1.25 inch ID bearing for the top. The shaft is hollow with holes at the bottom to allow the oil to flow through it and into the bottom of the rotor. There is a collar at the bottom for the rotor end plate to sit on and threads at the top to clamp the top end plate to the rotor and bottom plate.

    The other thing I should explain is the bearing mounts. I think it is necessary to allow the bearings to vibrate. Therefore I mounted the bearings to 1” thick rubber that I got from McMaster Car. The weight of the rotor is sitting on four springs.

    I am using a piece of hydraulic hose to connect the motor to the rotor. It works fine. But if the rotor vibrates, it tries to make the motor vibrate too. I think it would work just as good to have belt drive on the outside of the rotor with a spring loaded belt tightener. With belt drive, you wouldn’t need to make a place to fasten the drive motor to the center shaft, but you’d have to loosen the belt to clean the rotor out.

    I used an old oxygen tank for the outside of the rotor. It works fine, but if I were to do it again, I’d buy a piece of hydraulic cylinder barrel stock instead. The cylinder barrel stock is really expensive, but it would be a lot more accurate than an oxygen tank, and therefore be a lot less fuss to balance it. Also it would be a lot less fuss to machine the endplates.

    How did I figure the rotor length? I made it as long as I could conveniently make it. I wanted it as long as possible so the oil would be in there as long as possible to give it more time for the dirt to separate. There may be a reason why others centrifuges are shorter but mine does work.

    Yes, the top and bottom plates have 1/8 (if I remember right) grooves in them for the rotor to lock into. That is for making the ends of the rotor stronger, for keeping the rotor centered, and I have a rubber o-ring in the groove for an oil seal.

    God bless you.


    Into thine hand I commit my spirit: thou hast redeemed me, O Lord God of truth. I will be glad and rejoice in thy mercy: for thou hast considered my trouble; thou hast known my soul in adversities; And hast not shut me up into the hand of the enemy: thou hast set my feet in a large room. Psalm 31:5,7&8 The Boys Bugle is a Christian magazine for boys that everyone enjoys reading. To subscribe, send your address to or The Boys Bugle 156 Newton Rd., Potsdam, NY 13676


Post a Comment

Links to this post:

Create a Link

<< Home