Building the main body of the huller.
3/4" plywood, 4 side walls, two 5" by 9", two 6" by 9" and one 7" by 11 3/4" base, four light duty bearings (BLF201-08G) another two are needed for the hopper , two compression springs , fourteen 1/4 -20 nuts, eight 1/4" 20 by 1.5” long bolts, 1/4" washers, wood screws, handle ( we use Sea Sense replacement winch handle from Eastern Marine),
We recently processed three 1 pound test runs and another small batch of our short grain rice to determine the hulling rate and percent hulled. It takes 2-3 minutes ( 1lb) for the first pass and 1.5 minutes for the 2nd and 3rd passes, we winnowed but did not separate the hulled from un-hulled between the passes. The small batch of 1,181 rice grains had a 1st pass hulling rate of 77%. Yes, they were counted by hand. The video below shows it in action hulling, long and short grain rice. The huller will also de-hull wild rice. I just added a video using wooden rollers covered with 90D urethane sheeting. The fifth video shows a motor powering the table top pinch roller.
The unit consists of two halves and a feed hopper. One half has the handle which is secured to the base and the other has the sprockets and idlers and moves back and forth as the paddy is hulled. The half with the handle is 5” x 9” and the other 6” X 9”. The bottom and inside edge of the 4 sides should be perpendicular to each other.
Establish the location of the bearings:
The location of the clearance holes for mounting the bearings is determined by
1st Draw a vertical line 2 1/8” from the edge of the wood where the roller will be extending over the sidewall by 1/8”.
2nd Create a mark on this line 2 1/2" from the top of the sidewall.
3rd From this mark, create marks on the line for the clearance holes for the bearings, the holes for our bears are 1 1/4" from the center mark.
4th Drill a 3/4" clearance hole for the drive shaft and 1/4" holes for the bearings,
5th Use this sidewall as a template for the over drilling the holes in the other sidewalls, this ensures the location of the holes are identical. The bottom and inside edge of the pieces must be lined up while drilling out the holes. On the inside surface (roller side) create recesses at the 1/4" holes with the 3/4” bit deep enough so the bolt heads holding the bearings don't stand higher than the surface of the wood. Use the images as guides for this work.
6th Mount the bearings using 1 1/2” long 1/4" 20 bolts, use flat washers between the bolt head and the wood besides flat and lock washers at the bearing end. Temporarily mount the rollers with the shafts between the sidewalls and bearings.
7th Identify the side wall which will have the idler sprockets. In this sidewall create a 1/2” hole and a 1/2” wide slot for the bolts which will hold the idler sprockets. The upper hole is centered at 1” from the top and side edges of the sidewall, the 1/2” slot also 1" in from the edge starts at 4 1\2” from the top of the sidewall and extends downward to 5 3/4" from the top of sidewall. One method of making this slot is to drill a 1/2” hole at each end of the slot and then remove the material between them.
Building the spring-loaded gap adjustment system.
The spring-loaded gap adjustment system consists of two 1" right angle braces, a compression spring with a high working load, #10 32 bolt 2 1/2" long, stop nut and corresponding nuts and washers on both sides of the huller. The angle braces are attached to each sidewall between the bearings at the same height from the top. The bolt is fixed in place on one of the braces with a nut, the stop nut is spun onto the bolts, the two halves of the huller are brought together with the bolt passing through the hole of the other brace, the spring is placed around the bolt, install washers and add the final nut. Turn this nut to compress the spring.
Basic Information about using pinch rollers for paddy husking and this paddy husker.
Rollers rotating a different speeds in opposite directions shear off the husk, if the rollers are the same speed there is no shearing and if they are going in the same direction the paddy will not be pulled down between the rollers. To get the rollers rotating in the opposite directions and at different speeds a chain and sprockets are combined. The speed of our slower roller is 50% of the fast roller, we use 11 and 22 toothed sprockets. The rollers are Stoltz RP-57 made of polyurethane. They are approximately 4 1/2" in diameter and 3" wide with a 1 1/8" center hole. Additionally, self aligning mounted bearings are used for easier construction. If the bearings are unavailable sleeve bearings or just holes in the sidewalls for the shafts may be used. We buy the rollers and winch handle from Eastern Marine and the bearings, chain,sprockets, shaft collars, and chain break from the Big Bearing store. The sprockets from Big Bearing have teeth which are slightly smaller than sprockets for higher loads which allows the chain to drop into place easier while operating the huller. The huller is operated with the chain slack so the rollers can move away and together as the rice is hulled.
5th To center the shaft, use an adjustable right angle ruler. Measure with ruler around the roller and adjust the bolts which move the shaft until it is centered (start with the ruler set at 2 3/32”).
6th The final test before adding the epoxy is to spin the roller on a jig made up of two pieces of wood with notches at the top. Make the jig by placing two pieces of wood the same width together and drill a ½” hole at the seam between the pieces.
Place the shaft with the roller within the two half holes in the jig. Place a straight edge near or touching the roller, rotate the roller to verify the gap between the edge and the roller changes very little, if this is not the case, center the shaft better with the bolts. The rollers do have irregularities which cannot be removed unless after being mounted the rollers are turned in a lathe (this is how industrial rollers are made true). Our springs allow the rollers to move helping to compensate for this issue.
7th Once the shaft(rod) is centered in the rollers, the space between the shaft and plywood/roller hole is filled with epoxy or other binding material. We use Devcon 5 minute epoxy or other liquid epoxy, an industrial strength epoxy is not required. On the 1st side the epoxy is added place a small amount of material in the roller hole so epoxy doesn't flow out the other side. The surface of the shaft in the area between the two pieces of wood must be oil free and roughened (a flat is also recommended) before building this.
Stoltz RP-57 (Nov. 2016)
Mounting the huller to the base.
1st At this point the the two rollers should be in place and spin freely within the huller, drive in the set screws on the bearing collars.
2nd Spin the rollers again and make adjustments as necessary for the rollers to spin with very little clearance between the rollers and the sidewalls.
3rd Connect the two halves with the gap setting system with wood screws.
4th Secure the stationary half of the huller (it has the handle) to the base, with the front extending over the base by 2" and the side 1" from the edge. Use 1" corner braces with #6 by 3/4" long round headed screws to attach the sidewalls to the base. As the huller is being secured to the base make sure the roller still spins freely.
5th Move the slide into position be sliding it up into the huller with the back resting on the bolt and the front on the leading of the base. Use a small wood screw to hold it in place.
In 2011 the team at Brill Engineering was asked to develop an inexpensive human powered rice huller by the folks at Breezy Meadow and Orchards in Tinmouth Vermont USA. We've designed two types of hullers, a hand or bicycle rice huller, and a huller driven by a bicycle or a small motor. All the parts for the hand powered rice huller are available on-line or at local stores. This web site contains a video of the human powered rice husker in action, and building instructions. We've received inquiries from around the world (India, Thailand, Malaysia, Philippines, Brazil, Africa and more) about a need for an inexpensive huller which can be built by local craftsman or inexpensive to buy. All are welcome to use these designs to make a rice huller for themselves or manufacture for sale. We also build them individually and sell them. Contact us for pricing and then use the Paypal link or pay with a check.
For additional information, help, or questions please email Don Brill at firstname.lastname@example.org .
jig for spinning the roller and shaft.
Installing the handle.
Install foam between the sidewalls.
Secure 1/2" thick foam padding to one inside edge of the stationary sidewalls, this fills the gap between the sidewalls when the rollers are mounted. The foam padding also acts as a spring pushing the rollers apart so it should not be too highly compressed when the rollers are touching. Make sure the foam is next to the inside surface of the sidewalls because it should squeeze out and contact the rollers when the two halves are brought together. This contact or near contact between the rollers and the foam keeps paddy from falling outside the ends of the rollers.
Install a 1/2” by 2 1/2” long bolt in the fixed position and another within the slot using with nuts and washers for holding the idler sprockets in place. Bolts with the threads which go to the head are best, if not available a spacer will need to be used.
Adjusting the bearing alignment so the rollers spin freely within the huller.
Spin the rollers within the sidewalls, the rollers should spin easily or with very little resistance with the rollers nearly touching the sidewalls. Use the self aligning feature of the bearings to evenly align the rollers with the sidewalls. The Big Bearing web site has a video showing how to move the bearings within the housing. On the bearings, drive in one of the collar's set screws at the flat on the shaft, just enough to hold the shaft in place.
Just what is a Self Aligning Bearing? (From the distributor’s web site).
"Our mounted ball bearing units consist of two main components, a single row deep groove ball bearing insert and a cast iron bearing housing. The bearing insert has a rounded outer diameter that when mounted in the cast iron housing fits into the equally rounded inside of the housing. Because both the housing and the bearing have equally rounded contact points the insert bearing will pivot inside the bearing housing to accommodate misalignment of the shaft, vibration of the mounting surface/shaft and variance in the mounting of other bearings down the shaft. The tolerance between the bearing and the housing is so tight that it is not possible to adjust the angle with your hand you must bolt the bearing down or place it in a vice and use a pry bar or the shaft. them similar to the gap created when the rollers are in place."
Also, after a bearing is bolted to the sidewall it can be moved by using the shaft of the roller but you may want to practice using the method above before bolting the bearings to the sidewall.
Building the slide for the hulled rice.
To get the hulled rice to the front of the unit a slide must be made and inserted under the rollers. The front of the slide rests on the base on the handle end of the huller and the other end rests on a bolt towards the top of the of the other end.
1st Position the huller on the base with the sidewalls of the handle end extending two inches over the base edge.
2nd To make the slide cut a piece of the 1/8” thick wood (with a very smooth surface or cardboard) just less than the width of the distance between the sidewalls (3” wide is a good starting point) and 11" long.
3rd Position the slide inside the unit. Hold one end of the slide at the edge of the base and move the other end up within the unit until the surface of the slide is just below the back roller. Draw under the slide on the inside of the hopper drive sidewall,
4th Remove the slide and sidewall then drill a 7/32” hole such that the top the hole is at the line which was just drawn. Drive a 1/4” 20 X 1 1/2” bolt from the outside into this hole.
5th Reassemble the huller and verify the slide can be positioned with the front at the edge of the base and resting on the bolt at the rear. The slide will be installed after the unit is mounted on the base.
Centering a shaft in Stoltz RP-57 rollers.
Instructions for centering a shaft (rod) within the Stoltz RP-57 polyurethane roller. Pictures below of the various parts.
Materials needed: two Stoltz RP-57 rollers, ¾” thick plywood, 1 1/8” drill bit or hole saw, or a method to create an appropriate hole in the plywood, 7/32” drill bit, adjustable right angle ruler, 16 each ¼” 20 by 1.5” long bolts, (hex head bolts are needed so an open end wrench can be used to turn the bolts), and liquid epoxy or other material to fix the shaft to the rollers.
1st Cut four 2 3/8” square pieces from the plywood with a 1 1/8” hole in the center.
2nd If ¼” 20 (1.5 inches long) bolts will be used to center the shafts drill four 7/32” holes centered on each side. Turn the bolts into the holes.
3rd Roughen the walls of the roller holes or cut slots into the wall with a saw before mounting the wood with the four bolts. 4th Center the block with the bolts on the roller and hold in place with screws 1 ½” to 2” long. These instructions are for using ½” id shafts, if using 5/8” or other sized shafts adjust accordingly. The shafts need to be 9” long or longer, they can be cut shorter later for a better look. Roughen and create a flat on the middle 2.5” of the shaft. .
There are various methods of installing a handle, we've chosen to wedge the handle between two shaft collars, then drill a clearance hole completely through the handle and shaft. The handle we use has a slot and the end which we enlarge with a jig saw and metal cutting blade so the handle can be slid onto the shaft.
(BLF201-08G) Big Bearing store.
Installing the sprockets and chain between the two rollers.
The building instructions are separated into three groups, first, mounting and centering a shaft in the Stoltz RP-57 rollers, 2nd, building the main body of the huller and 3rd, building the feed hopper.
Feed hopper construction
The hopper consists of sidewalls, a slide, a gate and a feed roller. The hopper is approximately 7" by 9" and the width of the main huller.
1st. Create the feed roller by wrapping the 1/2" drive shaft with tape (duct tape) 3 inches wide so the diameter of the tape is approximately 3/4" to 7/8" three inches; from a 3 inch wide cloth sanding belt cut enough to wrap around the without any overlap. Use an adhesive ( 5 minute epoxy works) to bond the sandpaper to the tape.
2nd. Drill clearance and mounting holes in the sidewalls for mounting and holding the feed roller and bearings similar to the method used for the main body of the huller. Attach the bearings, slide the shaft with the sandpaper into place between the sidewalls. We use the bearings as guides with the bottom of the bearing even with the bottom of the sidewall and the bolt end even with the front edge of the side wall. Again, use this sidewall as a template for the drilling other sidewall.
3rd Create the gate, slide and supports as shown in the image above. The top of the slide support should be positioned so it is near the mid point of the feed roller with a very small gap between this support and the feed roller. Obviously the width of these parts matches the length of the sandpaper on the feed roller.
4th The top of the back brace is set so the slide rests on it with an angle of approximately 30 degrees. The distance between the sandpaper and the front of the slide is critical. It must be at least 1/2", a bit more is better because if it is too close the paddy will spill over the roller too fast.
5th The hopper is connected to the main body of the huller by resting it on top of the huller with the chain and sprocket mounted. The chain must be slack to allow the huller to slide below it. Set the feed roller so the paddy will drop into the pinch point between the rollers and then determine the length of chain needed. Use two 1" corner braces to attach the hopper to the stationary half of the main huller and add another support extending from the rear of the hopper to the base. Check that the sliding half of the main huller will slide under the hopper, if not adjust accordingly.
At the front and back of the unit add braces, made from the 3/4" plywood, and roller cleaners. Carefully attach braces to the back and front of the huller clearance holes and starting holes will help keep the screws from beign misaligned and moving the sidewalls to the point of interfering with the spinning of the rollers. The top of the brace will hold the roller cleaners so they need to be positioned so the top of the brace is at the center of the roller or 2 1/2" down from the top, the same distance as the bearing center. Use 2" by the width of the huller for the braces. After the braces are attached cut pieces from the 1/8" thick wood that are the length of the inside width of the huller and wide enough to cover the space between the brace and the roller then attached them with a screw.
1st Move the two halves so they are nearly touching.
2nd Install the #35 11 tooth sprocket on the shaft of the roller with the handle, the #35 22 tooth sprocket on the other roller shaft, and the idler sprockets on the 1/2" bolts with the idler on the bolt with the slot near the top of the slot so it can be moved downward to tack up some of the slack. Mount the sprockets so the teeth are towards the sidewall.
3rd Wind the chain such that it wraps around the sprockets and idlers as shown below. The chain is going below the larger sprocket instead on top ( which would be typical) because with the slack in the chain and the longer distance in pulling direction the chain doesn't keep the rollers from moving apart as the rice is being hulled. If you have not worked with chain, pull the chain until one end is at the top of the upper idler then bring the chain to the sprocket and rest it in the sprocket. The link on the left in the image is removed and a connecting link replaces this one. Make sure you ordered a spare or two. 4th Open the gap between the rollers so a hulled piece of rice will just fall through the gap. Slide the lower idler sprocket downward a bit, there must be some slack in the chain. Tighten the set screws in the two sprockets (before tightening create small flats for the set screws because we're not using keyed shafts. The sprockets from the big bearing site have smaller set screws so they don't hold as well as Martin sprockets or other high load sprockets. Create the flats on the shaft now if needed. The chain needs to be as close as possible to the bearings so we mount the sprockets such that it appears they are on backwards but this not the case because we can get the chain about an 3/8" closer to the bearings.
5th Turn the handle and verify the two rollers rotate. By dropping a few hulled and un-hulled rice into the gap while turning the handle, the gap size and spring tension can be adjust until the rice is hulled consistently. The stop nut is used to change the gap between the rollers and the nut on the end adjusts the spring tension. The goal is to set the gap and tension such that the rice is hulled without a lot of force which creates more work for the operator. Also, the two halves should separate by pulling on them by hand. Three things can keep them from separating, the springs are too compressed, the threads on the rod are hung up on the bracket, or the chain is too tight.