When repairing the piston group of the engine, difficulties arise with the installation of pistons - the rings protruding from the grooves do not allow the piston to freely enter the block. To solve this problem, piston ring mandrels are used - learn about these devices, their types, design and application from the article.
Purpose of piston ring mandrel
The mandrel of the piston rings (crimping) is a device in the form of a tape with a clamp designed to drown the piston rings in the grooves of the piston when it is mounted in the engine block.
Repair of the piston group of the engine is rarely complete without removing the pistons from its block. The subsequent installation of pistons in the cylinders of the block often causes problems: the rings installed in the grooves protrude beyond the piston and prevent it from entering its sleeve. To solve this problem, when repairing the engine, special devices are used - mandrels or crimps of piston rings.
The mandrel of the piston rings has one main function: it is used to crimping the rings and drowning them in the grooves of the piston so that the whole system freely enters the cylinder of the block. Also, the mandrel acts as a guide when installing the piston, preventing it from skewing, as well as preventing damage to the rings and mirror of the cylinder.
The mandrel of the piston rings is a simple but extremely important device, without which it is impossible to repair the piston group and other engine systems. But before you go to the store for a mandrel, you should understand the existing types of these devices, their design and features.
Types, design and principle of operation of piston ring mandrel
Today's crimps can be divided into two large groups according to the principle of operation:
● Ratchet (with ratchet mechanisms);
● Lever.
They have significant design differences and a different principle of operation.
Ratchet mandrels of piston rings
These devices are of two main types:
- With ratchet mechanism driven by a key (collar);
- With ratchet mechanism integrated into the lever-driven handle.
The most widely used are crimps of the first type. They consist of two main parts: a crimping steel belt and a ratchet mechanism (ratchet). The basis of the device is a tape with a width of several tens of millimeters to 100 mm or more. The tape is made of steel, it can be heat treated to increase strength, it is rolled into a ring. On top of the tape is a ratchet mechanism with two narrow ribbons. On the axis of the mechanism there are drums for winding tapes and a gear wheel with a spring-loaded pawl. The pawl is made in the form of a small lever, when pressed, the ratchet mechanism is released and the tape is loosened. In one of the drums of the tape, an axial hole of square cross-section is made, into which an L-shaped wrench (collar) is installed to tighten the tape.
There is a variety of ratchet belt mandrels for working with pistons of great height - they are equipped with a double ratchet mechanism (but, as a rule, only with one gear wheel and pawl) driven by one wrench. The height of such a device can reach 150 mm or more.
In any case, mandrels of this type, due to their design, are universal, many of them allow you to work with pistons with a diameter of 50 to 175 mm, and mandrels of increased diameter are also used.
The ratchet mandrel of the piston rings works simply: when the ratchet axis is turned by the collar, the gear wheel is rotated, along which the pawl freely jumps. When stopping, the pawl collar rests against the tooth of the wheel and prevents it from moving back - this ensures the fixation of the mandrel and, accordingly, the crimping of the rings in its grooves.
Crimping with a handle in which a ratchet mechanism is built into has a similar device, but they do not have a collar - its role is played by a built-in lever. Typically, such devices have a narrow belt, they are designed to work with motorcycle and other low-volume power units.
Mandrel of piston rings with key (wrench)
Ratchet piston ring mandrel
Lever mandrels of piston rings
● Tapes with crimping with pliers or other tools;
● Tapes with crimping with a special tool - ticks, including ratchet;
● Tapes with crimping with a built-in lever with a locking mechanism and the ability to adjust to the diameter of the piston.
The most simple crimping of the first type is: usually these are open rings made of relatively thick metal with two sides or loops at both ends, which are brought together with pliers or pliers. Such mandrels are unregulated, they can only be used with pistons of the same diameter, and in addition, they are not very convenient to use, since they require constant retention of pliers or pliers until the piston is fully installed in the sleeve.
The mandrels of the second type are more perfect, they are also made in the form of open rings, however, special pliers are used for their screed with the possibility of fixing in any particular position. Such crimps do not require constant application of effort to the mites, therefore they are more convenient and easy to use. Usually, devices of this type are offered in the form of kits with several mandrels of different diameters.
Lever piston ring mandrel
Correct selection and application of piston ring mandrel
The choice of piston ring mandrel must be made based on the characteristics of the pistons and the work that has to be performed. If only one car is being repaired, then it makes sense to choose a simple crimping with a ratchet mechanism or even with a plier clamp. If the installation of pistons is carried out regularly (for example, in a car repair shop), then it is better to give preference to the same universal belt mandrels with a ratchet mechanism or a set of mandrels of various diameters. It should be understood that for large automobile pistons it is better to use wide mandrels, and for motorcycle pistons - narrow.
For purchase for professional use, complete sets of tools for repairing piston groups can be an interesting option. Such kits may contain various mandrels for piston rings (both tape and ratchet mites), ring pullers and other devices.
Working with the mandrel of piston rings is generally simple, it comes down to several operations:
● For convenience, install the piston in a vice, lubricate its grooves with rings and skirt well with oil;
● Place the rings in the grooves in accordance with the recommendations - so that their locking parts are located at a distance of 120 degrees from each other;
● Lubricate the inner surface of the mandrel with oil;
● Install the mandrel on the piston;
● Using a wrench, lever or pliers (depending on the type of device), tighten the mandrel on the piston;
● Install the piston together with the mandrel in the cylinder of the block, use a mallet or hammer through the gasket to carefully knock the piston out of the mandrel into the cylinder;
● After the piston is fully integrated into the cylinder, remove and loosen the mandrel.
Set of piston ring mandress
When working with the mandrel, it is necessary to carefully tighten: if the crimping is too weak, the rings will not fully enter the grooves and will interfere with the installation of the piston in the liner; With excessive crimping, the piston will be difficult to knock out of the mandrel, and in this case, the mechanism of the device may break.
With the correct selection and use of the piston ring mandrel, the assembly of the engine after the repair of the piston group will require minimal time and effort.
Post time: Jul-11-2023