# How to calculate pulleys for a circular saw. In the armature chain

## Pulleys for electric motors with their own hands. How to make a homemade pulley

Standards establish 3 types of designs:

The seating holes come in conical and cylindrical shapes. Standard number of grooves max. 8. In order to reduce the wear of rubber belts, the working surface of grooves is ground.

The basic material used in production is aluminum or dural. They are considered the most optimal, since they have a good level of strength and are the least subject to belt wear. You can find pulleys made of textolite, plastic, plywood, etc.

Equipment / Project. TOKARKA / Pulleys: theory, online calculator, practice. / Calculation of belt pulley diameters for the V-belt. Online calculator.

The motor overhaul work is nearly finished. Calculation of the belt drive pulleys on the machine. A little belt drive terminology.

The basic input data we have are three values. The first value is the speed of the rotor (shaft) of the electric motor, 2790 rpm. The second and third are the speeds to be obtained on the secondary shaft. We are interested in two ratings of 1800 and 3500 rpm. Therefore, we will make a two-stage pulley.

Note! We will use a frequency converter to start the three-phase motor, so the calculated rotational speeds will be reliable. If the motor is started with capacitors, the values of rotor speed will differ from the nominal one in a smaller way. And at this point it is possible to reduce the error to a minimum by making adjustments. But to do this, you’ll have to start the engine, use a tachometer, and measure the current shaft speed.

Our goals are defined, let’s select the belt type and proceed to the basic calculation. For each of the manufactured belts, regardless of type (V-belt, poly-V-belt or other), there are a number of key characteristics. Which determine the rationality of use in a particular design. The ideal choice for most projects is to use a poly-V belt. It is called a polycircular belt because of its configuration, it is a type of long closed grooves located along its entire length. The belt is named after the Greek word “poly”, which means many. These grooves are also called ribs or streams. The number of them can be from three to twenty.

The V-belt has many advantages over the V-belt, such as

• Good flexibility permits operation on small pulleys. Depending on the belt, the minimum diameter can start from ten to twelve millimeters;
• High power transmission and therefore working speeds of up to 60 m/s versus 20 or 35 m/s for timing belts
• The traction force of a V-belt with a flat pulley at a girth angle of over 133° is approximately equal to that of a grooved pulley, and the traction force becomes higher as the girth angle increases. Therefore, for drives with a transmission ratio over three and the small pulley girth angle of 120 ° to 150 °, you can use a flat (no grooves), a larger pulley;
• Due to the light weight of the belt the vibration levels are much lower.

Considering all the advantages of poly-V belts, we will use this type in our designs. Here is a table of the five basic cross-sections of the most common poly-V belts (PH, PJ, PK, PL, PM).

 Designation PH PJ PK PL PM Rib pitch, S, mm 1.6 2.34 3.56 4.7 9.4 Belt height, H, mm 2.7 4.0 5.4 9.0 14.2 Neutral layer, h0, mm 0.8 1.2 1.5 3.0 4.0 Distance to neutral layer, h, mm 1.0 1.1 1.5 1.5 2.0 Minimum pulley diameter, db, mm 13 20 45 75 180 Maximum speed, Vmax, m/s 60 60 50 40 35 Length range, L, mm 11402404 3562489 5272550 9912235 228616764

Schematic designation of poly-V belt elements in section.

A matching data sheet is available for both the belt and the pulley in question.

 Cross-section PH PJ PK PL PM Distance between grooves, e, mm 1,60±0,03 2,34±0,03 3,56±0,05 4,70±0,05 9,40±0,08 Total size error e, mm ±0,3 ±0,3 ±0,3 ±0,3 ±0,3 Distance from the edge of the pulley fmin, mm 1.3 1.8 2.5 3.3 6.4 Wedge angle α, ° 40±0,5° 40±0,5° 40±0,5° 40±0,5° 40±0,5° Radius ra, mm 0.15 0.2 0.25 0.4 0.75 Radius ri, mm 0.3 0.4 0.5 0.4 0.75 Minimum diameter of pulley, db, mm 13 20 45 75 180

The minimum pulley radius is not given by chance, this parameter regulates the service life of the belt. Best if the minimum diameter is slightly larger. For this particular application we have chosen the most common “RK” belt type. Minimum radius for this belt type is 45 millimeters. Once you have that in mind, we’ll also take into account the diameters of the workpieces you have. In our case we have workpieces with diameters of 100 and 80 millimeters. We will adapt the diameters of the pulleys to these.

Let’s start calculating. Let’s show our initial data once again and mark the goals. The speed of the motor shaft is 2790 rpm. Poly V-belt “RK” type. The minimum diameter of the pulley, which is regulated for it, is 45 millimeters, the height of the neutral layer is 1.5 millimeters. We need to determine the optimal diameters of pulleys, taking into account the necessary speeds. The first speed of the secondary shaft is 1800 rpm, the second speed is 3500 rpm. Consequently, we get two pairs of pulleys: the first 2790 at 1800 rpm, and the second 2790 at 3500 rpm. The first thing to do is to find the transmission ratio of each of the pairs.

## Moving parts

Having finished connecting the motor and making sure that it normally ramps up and down, it is allowed to move directly to the device of the circular saw.

Let’s see what movable assemblies, on which the main load falls, we will need:

The drive should work as follows. The motor transmits the rotation to the shaft, on which the small pulley is pressed. A belt is put on the latter, sending the revolutions to the second pulley. Everything seems simple at first sight, but when the installation of the circular saw is carried out, there are many difficulties to be solved.

It is essential that the small pulley is ground. On it are arranged three to four grooves of the transverse type, so that the belt has an opportunity for a good hook.

The belt can not be used from an old washing machine, it is enough to take an analogue from another machine. It should be solid and have teeth.

A disk with a slightly larger diameter is welded to the edge of the big pulley to get a shoulder to prevent the belt from slipping during operation. It is not necessary to sharpen the serrations on this pulley, the grip of the belt will be quite enough.

The shaft holding the circular saw, fasteners in the form of a washer and nut should be reliable, so that at maximum speeds the saw is not deformed and does not jump off, injuring workers. It is recommended to use the shaft and fasteners from a factory-made circular saw.

The procedure for the device of the circular saw is described for the saw with three hundredths of a disk. Many will say that the engine from the Washing machine will not pull such a saw and will stop. But a few rules should be kept in mind here:

Simply put, the saw should not be overloaded and it is better not to run it idle.

## Basic diameters

To calculate the parameters of pulleys, as well as the drive as a whole, different values of diameters are used, so for the pulley of the V-belt transmission are used:

The calculated diameter is used to calculate the gear ratio, and the outer diameter is used to calculate the dimensions of the drive when assembling the mechanism.

For a toothed belt drive Ddp differs from Dnar by the toothing height.

The gear ratio is also calculated on the basis of Drace value.

To calculate the flat belt drive, especially when the rim size is large relative to the profile thickness, often take D.

## Gears

The minimum distance l between the centers of pulleys is lmin = 2 (D1D2) mm, where D1 and D2. diameters of master and slave pulleys in mm respectively.

Coefficient of efficiency is taken as equal to 0,9 (under condition of normal tension and coating of belt working surface with rosin).

Calculation of open flat belt transmission

Diameter of the pulley of the electric motor is usually selected according to a given diameter of the driven pulley.

The diameter of the driving pulley D1 is determined by the formula

where 1,05. belt slip ratio; D2. diameter of the driven pulley in mm; n1 and n2. number of revolutions of driving and driven pulley respectively per minute.

The received value of D1 should be compared with the catalogue data of the corresponding electric motor. Pulley diameter should be equal to or greater than specified in the table below. In individual cases it is permissible to reduce the diameter of the pulley against the catalogue data within a maximum of 10%.

Girth angle of the belt in degrees. calculated according to the formula

Girth angle for flat belts must be at least 150°. If the angle is smaller the distance between the centers of the pulleys must be increased.

Correlation between pulley width and belt width

 Pulley width in mm 40 50 60 70 85 100 125 150 175 200 225 250 300 Corresponding belt width in mm 30 40 50 60 70 и 75 80, 85 и 90 100 125 150 175 200 225 250 и 275

Main parameters of the V-belt transmission

 Name Indicator Minimum distance between centers of pulleys in mm lmin=D2 Maximum linear velocity in m/s 25 Maximum gear ratio 10 Minimum angle of circumference in deg 120 Average transmission efficiency (efficiency) 0,95 Maximum allowable number of belt runs per second 15

V-belt drive compared with flat belt drive for better belt to pulley coupling, less space required in the system, elimination of belt re-beltings, quiet and jolt-free operation.

V-belt drives are particularly cost effective for power outputs up to 40 kW.

Calculation of V-belt drive

Calculation of V-belt transmission determines belt type, pulley diameters, length and number of belts.

To calculate the gear must be known:

• transmitted power N in kW;
• number of revolutions per minute n1 and n2 of the drive and driven shaft, respectively;
• approximate centre-to-centre distance l0 in mm.

Belt type depending on transmitted power

 Sketch Belt type Dimensions in mm Transmittable power in kW a h О 10 6 0,37. 3,7 А 13 8 0,8. 7,4 Б 17 10,5 2,3. 18 В 22 13,5 8. 37 Г 32 19 19. 73,6 Д 38 23,5 38. 147 Е 50 30 148 and higher

## A little bit of theory about the construction and application of collector motors

Electric motors of this type can be DC or AC, with series, parallel or mixed excitation (only the first two types of excitation are used for AC).

A collector motor consists of the rotor, stator, collector and brushes. Current in the circuit, flowing through specifically connected stator and rotor windings, creates a magnetic field, forcing the latter to rotate. The voltage is applied to the rotor by brushes made of soft electrically conductive material, most commonly graphite or copper-graphite compound. If you change the direction of current in the rotor or stator, the shaft will begin to rotate in the other direction, and this is always done with the leads of the rotor, so that there is no remagnetization of the cores.

If you change the connection of both the rotor and the stator at the same time, there will be no reversal. There are also three-phase collector motors, but that’s another story.

### DC motors with parallel excitation

The field winding (stator winding) in a parallel excited motor consists of a large number of coils of thin wire and is incorporated parallel to the rotor, the winding resistance of which is much lower. Therefore, to reduce current during start-up of electric motors with power more than 1 kW include a starting rheostat in the rotor circuit. Electric motor speed control in this circuit is performed by changing the current only in the stator circuit, i.e.к. the method of terminal voltage reduction is very uneconomical and requires the use of a high-power regulator.

If the load is small, then an accidental break in the stator winding using this pattern will exceed the maximum allowable speed and the motor can go “off”

### DC motors with series excitation

The excitation winding of such an electric motor has a small number of turns of thick wire, and when it is connected in series in the armature circuit, the current in the entire circuit will be the same. Electric motors of this type are more stable under overloading and therefore are most frequently used in domestic appliances.

### There are two ways to adjust the speed of a DC motor with a series connected stator winding:

• By connecting a regulating device in parallel with the stator to change the magnetic flux. However, this method is quite complicated to implement and is not used in domestic appliances.
• Speed regulation (reduction) by voltage reduction. This method is used in practically all electrical devices. household appliances, tools, etc.д.

### AC collector motors

These single-phase motors have a lower efficiency than DC motors, but because of the ease of construction and control circuits have found the most widespread use in household appliances and power tools. They can be called “universal”, because they are not the only things you can do.к. They are capable of working both with AC and DC current. This is due to the fact that when you plug in the AC voltage direction of the magnetic field and current will change in the stator and rotor simultaneously, without causing a change in the direction of rotation. Reversing such devices is done by reversing the rotor ends.

To improve the characteristics of powerful (industrial) collector AC motors, additional poles and compensation windings are used. There are no such appliances in the engines of household appliances.

## It is necessary to lower the rpm on the electric motor

Welded concrete mixer. Found a 3-phase electric motor 2.2 watt. on the recommendation of “well-wishers” at 950 RPM. Purchased a 500 Microfarat capacitor for a 220. Connected the motor with a pulley through the belt directly to the agitator housing. Launched. and smiled sadly A lot of revolutions sand sticks to the walls. I do not want to change the engine, power is already at a minimum limit because due to 220 volts lost as they say by 30%. Well, it will continue to get lost. And from experience I know that motors about 1 KW are not pulling any more and you have to push them at startup. This engine yet starts itself even with 5 buckets of sand loaded. Also learned that the best way to regulate the RPM is with frequency despite the minus. overheating the engine. Factory frequency converters with all sorts of levelling tricks for my engine start at 6500 p. Expensive. Found in the net schemes even though simple in appearance but for me are incomprehensible ((( Find (and looking for) in the vicinity of the electronics problematic. I live in rural areas. Question:. May be in nature is ready simple schematic diagram on sale from any device for such purposes, which I would buy, bolted and started to work. Help guys. Thanks in advance.

There are three real options. 1. Lowering the frequency of the network is CURRENT. 2. Putting in a mechanical gearbox is HARD. 3. Replace motor. INCREDIBLE.

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Easiest way to put other pulleys. On a smaller motor, on a b.A bigger agitator.(and will spin harder) Electr. Methods are expensive, complicated to build, and unlikely to be feasible in your environment.

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Read also: Roller quick cutter for cutting glass

No money? The shovel and trough are not expensive.

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I don’t know what TC’s revs are, but sand sticks to the walls in brand name stirrers too. I just pour water first, then crushed stone, then sand, and finally cement a certain angle. And nothing sticks.

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You’re doing the right thing. This sequence speeds up and improves mixing, but does not guarantee residual sticking on the walls of poorly mixed mortar. Which is guaranteed in my case.

The shovel and trough are already there. But there’s also a desire to keep my back healthy, as well as a little understanding that you shouldn’t put equipment on this iron that would make it unnecessarily expensive.

Pulleys to put already a problem because the axis of the vessel was not provided a place for them, the belt is put from the engine directly on the vessel. Making a separate reduction band from 2 extra pulleys is also problematic. there is virtually no room for it. The engine already has a small custom pulley on it. about 70mm in diameter.

Last edited by FAI4;10.08.2012 в 23:04. Reason: Added post

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You are confused. A 10 bucket concrete mixer is freely driven by a 180watt 1 phase motor from a washing machine. You just need to get the reduction right. The easiest and most reliable, is to find a gear wheel from a ZIL flywheel and a gear from a bendix and make another gear based on two pulleys. The pulley on the engine should be as small in diameter as possible to relieve the motor. If you’re interested, I can take all the measurements off my stirrer, but not until tomorrow. It’s too late now.

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There are three real options. 1. It is WAY too expensive to reduce the mains frequency. 2. Putting in a mechanical gearbox is WORSE. 3. We don’t want to replace the motor.

A simpler solution has not yet been found. My logic prompts me that if the factory frequency converter costs about 6-7 thousand euros, I’ll do my best to keep this one.р., then a very simple diagram in a plastic box should be at least 2.5 cost less. 2. About the mechanics I said above. 3. I will do my best to keep this particular engine, which I think is good.

## Calculation of pulleys. Calculation of pulley diameters for the V-belt. Online calculator How to calculate the pulleys for the circular saw

Works on electric motor overhaul are coming to the end. Proceed with the calculation of the pulleys of the machine belt transmission. A little belt transmission terminology.

The main input data we have will be three values. The first value is the speed of the rotor (shaft) of the electric motor 2790 revolutions per second. The second and third are the speeds to be obtained on the secondary shaft. We are interested in the two ratings of 1800 and 3500 rpm. Consequently, we will make a two-stage pulley.

Note! To start the three-phase electric motor we will use a frequency converter, so the calculated speeds will be reliable. If the motor is started with the capacitors, the values of rotor speed will differ from the nominal one in a smaller way. And at this stage it is possible to reduce the error to a minimum by making corrections. But to do this, you need to start the engine, use a tachometer, and measure the current shaft speed.

Our objectives are defined, we pass to the choice of belt type and to the basic calculation. For each of the belts available, regardless of type (V-belt, V-belt, poly-V-belt or other), there are a number of key characteristics. Which determine the rationality of the application in this or that design. The ideal option for most projects is to use a poly-belt. It is called a polycircular belt because of its configuration, such as long closed grooves along its entire length. The name of the belt comes from the Greek word “poly,” which means many. These grooves are also called by other names. ribs or streams. Their number can be from three to twenty.

V-belts have many advantages over V-belts such as

• thanks to good flexibility it is possible to work on small-sized pulleys. Depending on the belt, the minimum diameter can start at ten. twelve millimeters;
• high traction capacity of the belt, hence the operating speed can reach up to 60 meters per second, compared to 20, maximum 35 meters per second with the V-belt;
• The grip force of a V-belt on a flat pulley at a girth angle of over 133° is approximately equal to that of a grooved pulley, and becomes greater as the girth angle increases. Therefore, for drives with ratios greater than three and a small sheave girth angle of 120° to 150°, a flat (no grooves) larger sheave can be used;
• Vibration levels are much lower due to the light weight of the belt.

Considering all the advantages of the poly-V belts, we will use this type in our designs. The table below shows the five basic cross-sections of the most common poly-V belts (PH, PJ, PK, PL, PM).

 Designation PH PJ PK PL PM Rib pitch, S, mm 1.6 2.34 3.56 4.7 9.4 Belt height, h, mm 2.7 4.0 5.4 9.0 14.2 Neutral layer, h0, mm 0.8 1.2 1.5 3.0 4.0 Distance to the neutral layer, h, mm 1.0 1.1 1.5 1.5 2.0 13 20 45 75 180 Maximum speed, Vmax, m/s 60 60 50 40 35 Length range, L, mm 11402404 3562489 5272550 9912235 228616764

Schematic diagram of a poly-V belt in sectional view.

For both the belt and the mating pulley there is a corresponding table with the specifications for making pulleys.

 Cross section PH PJ PK PL PM Distance between grooves, e, mm 1,60±0,03 2,34±0,03 3,56±0,05 4,70±0,05 9,40±0,08 Total size error e, mm ±0,3 ±0,3 ±0,3 ±0,3 ±0,3 Distance from the edge of the pulley fmin, mm 1.3 1.8 2.5 3.3 6.4 Wedge angle α, ° 40±0,5° 40±0,5° 40±0,5° 40±0,5° 40±0,5° Radius ra, mm 0.15 0.2 0.25 0.4 0.75 Radius ri, mm 0.3 0.4 0.5 0.4 0.75 Minimum diameter of pulley, db, mm 13 12 45 75 180

## Calculation of pulleys. Calculation of belt pulley diameters for poly V-belt. Online calculator How to calculate the pulleys for a circular saw

The main input data we have are three values. The first value is the rotor (shaft) speed of the electric motor 2790 rpm. The second and third are the speeds to be obtained on the secondary shaft. We are interested in two ratings of 1800 and 3500 rpm. Consequently, we will make a pulley two-stage.

Note! To start the three-phase motor, we will use the frequency converter so the estimated speed of rotation will be true. If the motor is started with capacitors, then the rotor speed values will differ from the nominal speed by a smaller amount. And at this stage it is possible to reduce the error to a minimum by making corrections. But to do this, you will have to start the engine, use a tachometer and measure the current speed of rotation of the shaft.

Our objectives are defined, we proceed to the selection of the type of belt and to the basic calculation. For each belt manufactured, regardless of type (V-belt, poly-V-belt or other), there are a number of key characteristics. Which determine the rationality of application in a particular design. The ideal option for most projects is to use a multi-ribbed belt. The poly-V belt is named due to its configuration, it is a type of long closed grooves located along its entire length. The name of the belt comes from the Greek word “poly” which means many. These grooves are also called. Ribs or grooves. The number can be from three to twenty.

Poly-V-belt has many advantages over V-belt, such as:

• good flexibility makes it possible to work on small-sized pulleys. Depending on the belt, the minimum diameter can start at ten. twelve millimeters;
• The high traction capacity of the belt and therefore the working speed can reach up to 60 meters per second, compared to 20, maximum 35 meters per second with a V-belt;
• The traction force of a poly-V-belt with a flat pulley at an angle of girth over 133° is approximately equal to that of a pulley with grooves, and as the girth angle increases, the traction force becomes higher. For drives with a transmission ratio greater than three and a small pulley girth angle of 120° to 150°, a flat (no grooves) larger pulley can therefore be used;
• Due to the light weight of the belt the vibration levels are much lower.

In view of all the advantages of the poly-V belts, we will use this type in our designs. The following table lists the five basic cross-sections of the most common poly-V belts (PH, PJ, PK, PL, PM).

 Designation PH PJ PK PL PM Rib pitch, S, mm 1.6 2.34 3.56 4.7 9.4 Belt height, H, mm 2.7 4.0 5.4 9.0 14.2 Neutral layer, h0, mm 0.8 1.2 1.5 3.0 4.0 Distance to the neutral layer, h, mm 1.0 1.1 1.5 1.5 2.0 13 20 45 75 180 Maximum speed, Vmax, m/s 60 60 50 40 35 Length range, L, mm 11402404 3562489 5272550 9912235 228616764

Sectional views of a poly-V belt.

For both the belt and the mating pulley there is a corresponding table with the specifications for making pulleys.

 Section PH PJ PK PL PM The distance between the grooves, e, mm 1,60±0,03 2,34±0,03 3,56±0,05 4,70±0,05 9,40±0,08 Total size error e, mm ±0,3 ±0,3 ±0,3 ±0,3 ±0,3 Distance from pulley edge fmin, mm 1.3 1.8 2.5 3.3 6.4 Angle of wedge α, ° 40±0,5° 40±0,5° 40±0,5° 40±0,5° 40±0,5° Radius ra, mm 0.15 0.2 0.25 0.4 0.75 Radius ri, mm 0.3 0.4 0.5 0.4 0.75 Minimum pulley diameter, db, mm 13 12 45 75 180

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