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Root washer improvement

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Topic Type: 
Idea

Our aim is to improve the function, safety and durability, of the existing root washer tool we surveyed at the Farm Hack Intervale meet up. We would also like to reduce the up front cost. We were very lucky to have input from the farmers who use this washer on a regular basis and at high volume. The improvements we propose fit into a few basic categories.

1 Materials The materials used for construction of the main barrel in the existing iteration are wood and formed steel-channel rings. Fabrication of the rings is one of the main expenses adding to the cost. They serve as the tracks into which casters fit and as the main support structure. One suggestion was the use of bicycle rims for this purpose. One concern about this solution was that they would be to small. We were told by the farmers that the wood slats of the barrel wore down and needed replacement. Talk about alternatives to wood led to the idea of using a piece of culvert pipe. If this could be sourced cheaply or salvaged, it could solve both issues at once.

2_Drive Mechanism_ Currently a chain is used to rotate the barrel with protruding bolts serving as gear teeth. In the second iteration, a gear box was added allowing for two speeds and the elimination of a pulley and v-belt used to gear down the motor. Occasionally the chain will jam on the teeth, lifting the whole barrel up and dropping it back down on the casters. This created a safety issue. There was talk of using a toothed timing belt, or fabricating gear teeth rather than using bolts. It seems the best way to go would be a pneumatic drive wheel(s) in place of the casters. This would eliminate issues with the chain and have the advantage of increased friction with increased load, avoiding slipping under heavier loads. Perhaps the flange of the culvert pipe could keep it in place over the drive wheels instead of casters/channel?

3_Work Flow_ Last year a hopper was added with a winch to lift it. The goal was to ease loading and control feed speed. This did not work out as planned and may interrupt work flow and could be dangerous. A hopper with a conveyor belt may be a better option. At times farmers wanted to stop the flow of roots coming out of the washer or just wanted them to stay in longer to wash more. A gate was tried, or farmers would push the roots back up the barrel by hand. The ability to change the angle of the barrel could change the speed that roots exit, or stop them from coming out to wash them longer. A re-purposed jack under the frame could quickly change the angle.

4_Silt_ To do a better job cleaning the roots, bristles could be added to the inside. If they were arranged in a helical pattern they could help advance roots like carrots. Silt must be managed so it doesn't clog drains or gravel. A perforated pipe like the ones used in a french drain could drain water from a catchment where silt can settle. The idea of recycling water was put forward. The problem cited was food security.

acrawford's picture

These are images of the two root washers on the Intervale, in Burlington VT. The first is from Intervale Community Farm, the second is the the Intervale Farm Equipment Co-operative root washer.

jmineau's picture

Has anyone ever experimented with a belt drive. If the motor remains on top, the barrel could be partially suspended by the belt thus providing adequate friction. Also, what motors/gear reducers are you all using?

ccaissie's picture

I'm building one, based on an example of a near identical unit as shown here. The one here has a Baldor GP7405 drive with the chain rig. Looks like a 1" pitch ag chain driven by a 14 tooth sprocket. Motor output (variable) is listed as 68 rpm Right, it does snag on the protruding screws. Maybe without those screws it would slip.

A belt could work, with the drive on a pivot base and a spring for tension. V-Belt like a 5V or a C size would be robust and give enough grip under low tension.

mostlyiguessso's picture

I think you're on to something with the washer being partially suspended by the drive belt. It could have the same result on friction as bottom mounted drive wheel. It would need to be a really strong belt and pulely/drive shaft, the weights can be considerable. It would keep the motor located above to help keep it dry as well. What would receive the belt on the barrel? The bolts as chainring teeth need upgrade for sure.

I also like the idea of using locally harvested wood for the barrel. Locust grows fast and is incredibly rot resistant. A bunch of saplings could be used without any milling, just attach to the rings. The rings would remain a big expense, though.

ccaissie's picture

One issue with using a belt drive is that the forces on the drive output shaft will be increased in order to create enough grip. The shaft will have to drive the belt, AND hold enough tension to grip. As long as this is considered, it's a good idea, but too much load on a marginally designed shaft will shorten its life.

We're building this unit now in Maine, and I'll post more info as it unfolds. We expect to be using it mid August. We're going with agricultural chain. The protruding screws and nuts on the original worked ok to engage the chain, but the shape of them was a problem. I think using rounded acorn nuts will keep them from snagging and causing the mentioned problems. We'll soon find out.

The rings can be rolled locally, and the quote I got was $54 each, which is high, but if they're correctly made, they'll run true and last forever.

The locals are timber framers and we've got some locust stock, so this washer might become a real work of art. If I could find a bronze gearbox....

ccaissie's picture

The folks up here want a root washer as a shared community tool. I've agreed to put one together and this is the only one I've seen up close to date. It is claimed to work well, with some of the comments above noted.

I also wonder if the materials can be upgraded. This one uses Aluminum channel for the structure...durable, but expensive..non-sustainable. How about a rot resistant local wood like white oak or locust? White pine heartwood is pretty good. Cedar is very good. Using a hardwood would increase cost and weight, but would reduce wear issues from the grit/tumbling parts. Maybe a periodic replacement is part of the design. We've got wood.

A drive wheel would work, but needs trial to see if it slips. Top mounted drive stays reasonably dry, but does not benefit from gravity to maintain friction. Needs further tinkering. A combination conveyor drive and barrel rotator is an idea. Odd angles, tho'.

It looks like the variable speed control is a good thing. Motor and controller as shown is about $550.

I don't know about bristles. Maybe available in strips and secured inside?

Great site and project!

Silas Blevins's picture

How about a rot resistant local wood like white oak or locust? White pine heartwood is pretty good. Cedar is very good. Using a hardwood would increase cost and weight, but would reduce wear issues from the grit/tumbling parts. Maybe a periodic replacement is part of the design. We've got wood.

gurjeet

Millard Glass's picture

It could have the same result on friction as bottom mounted drive wheel.

ccaissie's picture

Acorn nuts on drive studs slip occasionally, but do not catch and heave the barrel. Wood frame works well, Hemlock and pine from the local mill. Fixed brackets are used to hold the water distribution pipe, Owner is happy, have requests for more, as they are locally produced, the purchased machine components are very durable and wear parts are easily replaced, sustainable and recyclable. Variable speed drive is essential...could be done with belts, but electronics are easier.

Heron Botanicals's picture

Please read our discovery post in the "idea" section of the pedal powered root washer tool page. We've finally completed manufacture on a stainless steel, re-envisioned drive-train that is robust and capable of meeting all we need to remain a federally compliant production facility. Enjoy, and I look forward to joining to conversation! (http://farmhack.net/forums/bike-powered-root-washer-v-20)

ccaissie's picture

I see that you've got the design restraint of materials choice for specialty crops..is that the big hurdle here?

C

Heron Botanicals's picture

Yes, it's for plants and yes, we had some pretty specific parameters! Please see my response to your original post on the "Tool" side of the house.