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Revision as of 12:47, 15 June 2014
A simple homebuilt drag harrow using modern S-tines and a cage roller. This unit was sized for use by a team of small donkeys. The goal was to efficiently utilize the limited draft power in a unit that was easy to build and maneuverable in small spaces.
My goal was to make a drag that was light enough for my miniature donkeys to handle. I realized that S-tines properly mounted at the correct angle move the most soil for a given draft, so I built the drag around standard agricultural S-tines (Danish tines). The biggest challenge was to fabricate a horizontal raise/lower mechanism. I think I came up with a fairly robust system that is not too difficult to build. I have tested it in my garden and I am very happy with how well it works. The unit is super-maneuverable and the cage roller really does a job on the clods.
Project Background
Drag harrows using a rotating raise lower mechanism do not keep the teeth at an optimum angle for easiest penetration into the ground. Basic cultimulchers using S-tines start at around $4,000 and go up from there. The Donkey Drag can be built for less than $500 and can be sized for your exact situation. Once you have a unit with S-tines, there are many different teeth available and the tines are always held at the correct angle for working the soil.
- easier pull and superior ground penetration over c-tine drags
- inexpensive to build using mild steel and stick welding
- can be sized for available draft power
Project goals
A design that is easily built by amateurs, rugged in the field, and effective in weed control, bare fallow cultivating, and seed bed preparation.
Design
The prototype unit was built with primarily 1/8" (.120) metal stock with the flat stock and roller ends being 1/4" stock. The s-tine rails are 2" x 3/16" square tubing, which was definitely heavier than required (should have used 2 x 2 .120 stock). Use .120 for all main members. The main frame is 2 x 3 angle iron with 2 x 3 square tubing cross members. The main frame could be built using 2 x 3 angle all around. There are 2 front cross members on the prototype, but only 1 is needed.
The unit has 2 28" wide tool bars which are mounted 9" apart on center. Overall length is around 42" (need to check). The cage roller should be pushed back as clods can get stuck between the roller and rear cross member as built. The prototype has two front cross members but only needs one that is capable of mounting the front casters. A front mounted crumbler gang was considered but discarded once I realized this would make turning very difficult. The rear cage roller was built on a 1" shaft but a 3/4" shaft should be strong enough at this size. Use turned and polished round stock and ordinary agricultural pillow block bearings to fabricate.
Be diligent welding the two frames. If they are warped in any way the raise and lower will be very stiff due to the geometry shifting. The lift arms are 1 1/2" x 1/4" stock drilled 11" on center. All the lift arm pins are 3/8" bolts. I used grade 8 bolts which are nice in that the threads are very robust when forced through misaligned holes in mild steel. The rear lift arms have a 1 1/2" square tubing cross member, which mounts the raise/lower piston and is necessary to keep everything aligned at different heights.
Cage roller
The cage roller is fabricated with 8" discs with 8 pieces of 1/2" rebar welded in place. This creates a roller which is not round but octagonal. The effect is that the unit is constantly being raised and lowered by 1/2" or so as it moves forward, shaking the teeth and loosening the soil. This effect would be less pronounce with a larger roller size or more rebars being fitted. The cage roller, being not round, also presents some forward resistance on flat ground and makes it less likely the unit will coast into the draft animals' heels. Nevertheless, care should be taken on sloped or hard-packed surfaces. Also, the octagonal rolling on hard ground shakes the drag and makes a unique and disquieting noise that may spook unseasoned animals. Be prepared to hold back and help your team when hitching for the first time. If possible, work in an enclosed environment or do the first hitch on sand or soft ground.
Video walk around
Costs
I spent around $350 on this project using mostly new steel and all new s-tines, bolts, casters, etc. I could have saved a little on shipping with more foresight. I also ordered an extra assortment of teeth for the tines which I may or may not use. So far I am only using the 1" reversible spike teeth.
| item | source | cost |
|---|---|---|
| 5 s-tines with brackets and assorted points | http://www.agrisupply.com/danish-s-tine-shank-standard-duty/p/27804/&sid=&eid=/ | $129.00 |
| 4 swivel casters | http://www.harborfreight.com/4-inch-x-7-8-eighth-inch-rubber-swivel-caster-66361.html | $25.00 |
| assorted .120 steel | https://www.pottingersteel.com/ | $150.00 |
| 1/4" steel discs for cage roller | local shop with plasma cutter | $32.00 |
| 2 1" pillow block bearings | http://www.agrisupply.com/ | $33.00 |
| 1" x 32" polished round stock | local steel supplier | $30.00 |
| TOTAL | $366.00 |
See Help:Tables and Help:Table examples for more.
Discussion
Your discussion.
Next Steps
More testing and use in the field are required to determine the durability of the design.
Conclusions
A good reference point for building your own custom drag at a fraction of the cost of new, and superior to old c-tine style drags.
References
Contact details
Charlie Tennessen https://www.facebook.com/charlie.tennessen