I used coated laundry line to make my grid and placed them about 3-4 inches apart, which has worked ok for me. I linked to a page with a video that has my barrel bin on it.

Here is a link that might be useful: link to video with my barrel bin

YMMV and MOMC, Your Milage May Vary and My Opinion May Change, but I am seeing a 9X9 opening getting ummm constipated, even with a hand tool to do flow through surgery to free the material. In my opinion and very limited experience, the material I add (whole, un choppped, frozen or nuked) quickly packs to the sides and like "The Carrot Seed" just won't come out. And I certainly did not change from bin to flow through to deal with vermicompost constipation. I wanted the magic of self harvesting, worm and cocoon free, castings.

From what I am seeing I see no reason why a yard by 8 yard wide flow though would need any grate. That stuff just sticks to the sides and ain't sinking.

"One of these things just isn't the same." My experience does not match others. But it is what I am seeing and experiencing.

I do hope soon I will like others have a sensible grate size of three inches and behaving vermicastings that fall through on its own. I am posting a picture of Issac Newton for my wicked gravity defying vermi to view.

Let it dry out a bit. Wet castings are a sticky mess just like any other wet poo.

When it dries, it becomes more crumbly and then starts to drop out by itself.

Hi All; A flow thru system does not self harvest. It is designed to hold the castings above a false bottem until the operator does the harvesting when the bin needs more feeding room on top. The harvested castings area is also the air input area of the system. The castings need to be held above this space until all the worm activity is done in the castings.

If it were a system that the castings just fell when ever the system was disturbed by worm activity or human activities within the bin it would not be a flow thru system it would be a drop out system.

The term flow thru refers to the air flowing up thru and the food and bedding flowing down thru as processing takes place.

The spacing of the grid bars that I used was 2.5" and the barrel system I made is working as designed. I use a small hand tool to scrape the castings from above the grid grate bars. The tool I use is a three pronged garden tool.

I made part of the bin yesterday, using 6 bars across the bottom and one going the other way. I still need to add "agitators" and handles to the bars. Imagine a foosball table for the concept.

Excellent information and advice.

In my dreams there is a self harvesting drop out system. I am working towards it. Or maybe to harvest I walk by and give the side of the system a big waaap with my palm and the finished compost magically falls out for me. That is what I want.

My FT system is working well at present. I harvested a bucket (10 litres) of castings today just by using a shovel in the access hole. It sure beats bending down and scraping! I just checked, and already some more has fallen in the hours since I harvested.

As an excercise, I went through the bucket of castings and found about 30 - 40 worms and a few cocoons, probably not enough to justify the time spent. I decided to put them back in, as they can keep working the castings until I am ready to use them, which will also help stop them going smelly as they dry out a bit more.

My defnition of FT is that raw material goes in the top, and the finished product comes out the bottom. Simple as that.

I would love someone to prove that they can get air to flow through what is essentially 2 feet of mud.

The open area at the bottom does increase the surface area exposed to air, and worms working the bottom probably cause a bit of added aeration, but I really don't see a system of air galleries from top to bottom that would be required for air to flow.

If this forum software wasn't so weird, I would add some photo's.

""when you cranked it or pushed it back and forth""
I'm not sure you would be able to do that manually because it does get very heavy.

""I walk by and give the side of the system a big waaap with my palm""
You give too many waps and the herd might just take off, lol.

I figure my FT is a "DD" because the VC keep dropping down, especially at the sides. Then I put an alu roasting pan in the catch area and I also have a light shining into that space because of finding sooooo many worms with the falling VC. There is minimal VC in the roasting pan and I do not see any worm down there so far. I guess the reflection of the light by the alluminum deter them from coming down. I will give you an update when I harvest.

""can get air to flow through what is essentially 2 feet of mud""
If you have mud in there, your FT (or DD) is too wet.
Even when I got leachete, the VC was NEVER muddy.
So, add more shredded paper/cardboard.

I think what Random refers to as "mud" is the same thing that I do- dense dark brown moist muck. All my bins have it in the bottom and that is where the majority of the worms seem to be so I'm thinking the moisture isn't a problem.

I've thought about a flow thru but then i think that if I still have to separate worms, what is the real advantage? I tend to use my castings all at once..I add them to regular compost to make potting soil and ammend my container plant soil.. I doubt I will ever have a large enough worm operation that I will be using the castings in the garden. I don't really want worms in my houseplants.

A YouTube video of a harvest in an OSCR bin with turning harvest bars.

As you can see its an easy setup. He just put bolts through the bars. If i remember right the bolts stick out both sides of the bar about 1 1/2 to 2 inches. And each bar has a blot secured through it about 8 inches apart. The bars are set into the bin so that the bolts are staggered away from the bolts on the next bar. Half way between two on the first bar. That way there are bolts on 4" centers.

Part one is posted on the optional link
And part 2 http://www.youtube.com/watch?v=0b-eUfcI8u0

Here is a link that might be useful: The Strawberry Store Oscr first harvest

A harvesting mechanism so ingenious in its simplicity, it will make you smack your forehead and say, "Duh, why didn't I think of that!" (Didn't someone say that in another thread?)

I used 1/2 inch PVC and deck screws. Since my bin is made of flimsier materials, I had to frame the mechanism with 1/2 inch PVC. The frame will be an obstruction to the falling VC, but I think it will still work OK. I have T's on the end of each pipe, so I can turn them by hand. The pipes are on 4 inch centers. Now that my secret mechanism is no longer a secret, maybe I'll post pictures.

I have not done my first harvest yet, so I don't know how well it will work.

I don't know how you would do this in a round bin. Since the bin is smaller on one side of the bar than the other, I don't know how you could space the fingers on each bar. You would want to scrape as much as you can on one side, without them getting hung up on the other side.

I was thinking of using something curved but hollow, like eye hooks. A flat paddle seemed like it would be too difficult to push through dense casting and a straight bar like a screw seemed like it wouldn't disturb things as much.

Since my bars will be able to also slide back and forth across the bottom of the compost, I am hoping I won't have any dead spots.

I have a flat paddle attached with screws every inch. The material the flat paddle is made from is not very strong. If it breaks, I still have the screws.