The branches remaining after trimming trees are rather inconvenient waste. Heaped up in a heap, they take up a lot of space, and you can’t put branches into the oven right away, you have to chop them with an ax for a long time. It’s a pity to make a fire and just burn it in the garden. A suitable option for a zealous owner is to make a chopper with your own hands to process them into wood chips. And she will find a use - at least burn in the boiler, at least use for compost. We are interested in the design of homemade crushers, since the prices of factory units are not comparable with the volumes of wood processing in ordinary private households.
Varieties of garden shredders
As soon as they do not call chippers used for crushing wood waste. Chipper, wood chopper, shredder, chip mill - this is not a complete list of names. Despite such a variety of terms, the arrangement of the various units is almost the same. Any crusher consists of the following elements:
- steel frame, where all parts and mechanisms are attached;
- the main drive is an electric motor or a gasoline (diesel) motor with a power take-off shaft;
- cutting mechanism;
- main gear (usually belt);
- protective cover;
- 2 bins - for feeding wooden sticks and unloading wood chips.
In fact, homemade branch shredders are divided into varieties only by the device of the cutting mechanism, the remaining elements differ only in size. If you carefully look at the drawings of the crushing part published on the Internet, you can distinguish the following popular solutions:
- In the middle of the shaft, 2-3 dozen circular saws are mounted, equipped with hard alloy teeth.
- The design repeating the device of a jointer on a circular machine. Longitudinal grooves are made on the shaft (from 2 to 6 pcs., Depending on engine power), where chopping knives made of carbon steel are fixed. The branches are chopped at a 90 ° angle to the knives.
- Disc grinder for wood, where the knives are attached to the plane of a steel circle mounted on a shaft. Here the branches must be fed at an angle of 30–45 ° to the surface of the disk, which is ensured by the design of the loading hopper.
- Chipper with two shafts that rotate synchronously. The cutting edges of the knives mounted on the shafts converge at one point during rotation. Due to this, not only crushing occurs, but also self-tightening of branches after capture. Wood supply - perpendicular to rotating knives.
Note. To increase the torque and cutting force in garden shredders, a flywheel mounted on the free end of the shaft is used. An exception is a disc grinder for branches, where a heavy metal circle with attached knives serves as a flywheel.
To process thick branches and branches for firewood, you can make a mechanized cleaver. Variants and drawings of the machine are presented in our other instructions.
Production manual
First of all, it is necessary to understand that without the skills of metalwork and welding and the corresponding tool, you can not even make a simple wood chopper from circular saws. In addition, for the manufacture of shafts and housings for bearings you will have to go to a turning workshop, unless you can find a ready-made assembly from an old machine. The whole process is conditionally divided into the following stages:
- Choosing a shredder design.
- Selection of the engine for the drive and the calculation of the final drive.
- Billet of metal and parts to be turned on a lathe.
- Frame assembly.
- Installation of a drive, a cutting mechanism and a belt drive.
- Mounting the protective cover and hopper.
Note. We talk about belt transmission as the easiest to manufacture and safe to use.In the event of any accident or overload, the belt will slip or slip off without any consequences. What can not be said about the hard link through the circuit (gear).
As for the choice of design of a homemade branch grinder, here the recommendations are simple:
- an aggregate of circular saws is the best option when you need to get small wood shavings with minimal cost;
- if you plan to grind branches of small diameter into a larger fraction, then a cutting mechanism such as a jointer is suitable;
- when in large quantities it is necessary to chop branches up to 5 cm in size, it is better to make a disk crusher.
For reference. Small shavings and chips are often used by gardeners to make compost and mulch. It is also possible to produce fuel briquettes from it for heating a country house.
When the type of chip cutter is selected, you can begin to procure parts, materials and equipment. But first of all it is necessary to fulfill ...
Engine selection and belt drive calculation
Drive power is an indicator on which the thickness of the branch you can process on a do-it-yourself crusher. Here are some tips for selecting an engine:
- An electric motor with a power of 2.5-3.5 kW, a minimum of 2 kW, is ideal for your purpose. A 1.5 kW motor can be used to assemble a chopper for grass and small branches.
- The power of a gasoline or diesel engine should be 5-6 liters. with. Such are put on household motor-blocks and mini-tractors.
- It makes no sense to buy an electric motor of too much power, unless such one lies idle in your barn. He will use up the amount of electricity that does not correspond to the work done.
Note. The number of revolutions of the electric motor does not play a big role, since we get the necessary speed of rotation of the knives due to V-belt transmission.
In order for your tree shredder to confidently chop branches, the knife shaft must be informed of a speed of not more than 1500 rpm by selecting the diameter of the driving and driven pulley. Crucial here is not the speed of rotation of the knives, but the developed torque (force). The distance between the pulleys and the length of the belt also does not play a big role. Unless the belt is too long, it reduces transmission efficiency and is less stretchable.
Calculation example. There is an electric motor at 2800 rpm, which must be put on the crusher. The best solution is to halve the shaft speed to 1,400 rpm. Then the pulley diameters will differ by 2 times. For example, the size of the driving pulley is 100 mm, then the diameter of the driven (standing on the working shaft) will be 200 mm.
Tip. When ordering a turner pulleys for V-belt drive, it will not hurt to think about the future. It is better to make pulleys on 3 or 4 streams so that the speed on the working shaft can be changed by changing the belt. Then the chopper can be adjusted to various working conditions, for example, for crushing stalks of corn, sunflower, grass.
Preparation of materials
The best way to save money on making a chip saw is to find the right materials in the household. The following types of metal rolling are suitable for assembling the frame:
- single equal-angle corner with a width of 50 to 63 mm;
- 2 corners of 35 mm each, welded in a “box";
- profile pipe 40x40 mm in size;
- channel number 6.5-10;
- round pipes with a diameter of 32–48 mm.
The motor is mounted on a steel sheet with a thickness of 10 mm and dimensions corresponding to the distance between the mounting holes on its flange (with a margin of 30-50 mm on each side). For belt tension 2 types of devices are used:
- The holes in the plate for mounting the engine are made oblong so that it can be pushed back and fixed with bolts.
- The plate is installed at one end on the hinge, then the belt is pulled by the weight of the electric motor. On the other hand, it is fixed with nuts on the studs, as shown below in the photo of a homemade grinder.
To make the simplest design of a shredder, buy 20-25 circular saws with carbide tips and as many spacer washers with a diameter of 20 mm. This will give you a working part with a width of about 80 mm, which, if desired, can be increased or decreased by adding or removing saws.
Note. The thickness of the teeth of the circular saw is greater than the steel base, so you can not fasten the tools close to each other. To compensate for the width of the teeth, washers are used that are placed between the saws.
The shaft driven by the belt must be turned on a lathe from a steel rod. But before making this part, find 2 bearings under whose seating size the shaft will be pierced. You will also have to make bearing housings with mounting flanges. Sometimes they can be bought ready-made in the secondary market or in specialized stores.
Tip. As an option, you can use the rear axle bearings with a landing diameter of 25 mm from the classic Lada models, and use the finished stud with nuts as a shaft.
To install circular saws on the shaft, you need to cut the thread. As a flywheel, use a circle of steel 10 mm thick or more or a large pulley from some agricultural machinery. You will also need a steel base plate for branches, playing the role of a counter-knife. Cut it out of a sheet with a thickness of at least 10 mm.
If you have chosen the design of a chopper with chopping knives, then you can take the drawing of a knife shaft for the jointer as a basis. Just change the axle diameters in it, where you need to press the selected bearings. It is better to reduce the width of the working part to 100 mm, because you are not going to put whole logs into the crusher. Chippers for knives are usually made on a milling machine from automobile springs.
To assemble a disk type chipper, in addition to the shaft with bearings and knives, you will need:
- a steel circle 15–20 mm thick with a diameter of 40–50 cm (depending on the power of the electric motor);
- sheet metal of at least 5 mm on the casing, whose front wall serves as a counter-knife;
- the same, 1-2 mm thick for welding the hopper;
- M12-16 bolts with nuts for fastening.
The cutting device of a disk grinder with a knife mount is shown in the drawing:
Frame manufacturing
Regardless of what type of crusher you have chosen, you need to make a foundation for it - a bed, where the drive and the chopping mechanism will later be installed. Weld it from corners or pipes, using the following recommendations:
- Pick the height for your height so that it is convenient to lay branches in the hopper.
- The design must be stable. Therefore, make the frame width not less than 500 mm, the length is arbitrary.
- Stiffen the frame by welding between the uprights of the cross member.
- For convenient movement of the unit to the frame, it is advisable to attach a pair of wheels and weld the handle.
Consider where you are going to put the electric motor. For a chopper made by hand from circular saws, the recommendation is this: put the motor in the alignment of the frame so that it does not protrude beyond its dimensions. The same applies to other types of crushers.
Chopper assembly
To begin with, we will assemble a chip cutter from a package of circular saws, observing the following order:
- Assemble the saws on the shaft by laying washers between them and tightening with nuts on both sides.
- Press the bearings onto the shaft and then into the outer housings. Bolt the latter to the frame, after making holes in it.
- Place a pulley and a flywheel on the ends of the shaft, and secure them securely.
- Close to the saw teeth set a steel plate - a counterknife.
- Install the electric motor and final drive, tighten the belt well.
Tip. Before assembly, be sure to lubricate the bearing cages by removing the plastic covers. Set the saws so that the tooth profiles do not match.
It is better to fasten the counter-knife not by welding, but by bolts through oval-shaped holes.The point is to adjust the gap between the edge of the plate and the working teeth, which allows you to change the size of the chips in small limits. The direction of rotation of the saws is “toward you”, that is, the teeth should “run” onto the counter-knife.
After assembling the parts, fabricate and install a protective cover made of thin metal, and in front - a receiving hopper. The sizes of these elements are arbitrary, the main thing is ease of use and safety. At the end, connect the unit to the mains with a power cable through a 25 A circuit breaker.
The assembly of the knife crusher is carried out in the same order, only at first you need to install and fix the knives in the grooves of the shaft. There is one subtlety here: the stronger the cutting edges protrude beyond the shaft surface, the larger the chips will be at the output. The hopper is welded so that the branches are fed at an angle of 90 ° to the cutting mechanism. How to do this correctly is shown in the video:
Tip. The unit can be improved if you make an additional tightening device. It is necessary to make the second shaft smaller, weld metal strips along it and connect it to the main mechanism through a belt or chain drive. The speed of the tightening shaft must be reduced, otherwise the branches will begin to beat hands during loading.
In the manufacture of a disk chopper of branches there are also no special tricks, it is enough to follow the drawings and securely fasten all the nodes. The only moment: in the manufacture of the outer casing, try to make the front wall along which the knives rotate thicker, and the gap between them smaller. Otherwise, the flexible thin sticks the mechanism will tighten inward and wind on the shaft.
The back wall of the casing must be well attached to the bed at least 4 points, for which you will need to weld additional brackets, as shown in the assembly drawing.
Conclusion
The most difficult operation in the manufacture of a garden shredder is turning the shaft and milling the knives from the spring, which you can not do with your own hands. You will have to pay for this service, unless there are a couple of metalworking machines in the household. The task will be simplified if you manage to find the drive assembly, for example, from an old circular saw.
Another option is to use the circular itself for crushing the branches by installing a working mechanism for cutting on its drive. Again, the shredder can also function from the motor block engine, you just need to make the belt drive correctly.