Wheel pairs press-fitting. MODENGY 4002 antiscuffing paste

Wheel pairs press-fitting: process description

Wheel pair is one of the basic elements of a rail (railway) vehicles running gear. It is needed to direct going, to switch between the tracks.

A wheel pair consists of three parts – an axle and two wheels.

While operating, wheel pairs are exposed to enormous loads including shock ones at running onto the rail junctions and other railway bumps.

To provide reliable functioning of a vehicle running gear, the wheels must be tightly fitted to the axle, all elements much rotate as one part. That’s why tension is used to connect the elements.

In order to provide press-fitting (tension), the axle diameter must overdimension the wheel matching site. Tension value directly influences reliability of parts operating.

To form wheel pairs, the cold press-fitting method with hydraulic press is applied.

For the purpose of providing required parameters of surface roughness, axle and wheels undergo mechanical treatment. Next, the parts are cleaned and degreased, one of the wheels is put into the press stand intended for it.

After lubricating, one end of the axle is inserted into the wheel, and the second one is directed to the press plunger. At this stage, special attention is paid to the geometrical axle parts which must not be skewed.

After press-fitting of the first wheel, the axle is turned over, and press-fitting of the other part is done in the identical way.

Control over assembly in a proper way is performed with press-fitting analysis diagrams for each wheel.

The diagram registers the dependence of press-fitting effort on the value of wheel movement along the axle.

In process of diagram analyzing, final effort, tension, conjugation length, and curve shape are controlled. If one of these parameters is unsatisfactory, the wheel pair is considered defective.

Improving efficiency of wheel pairs press-fitting with MODENGY 4002

One of the important factors affecting quality of wheel pair forming, and stability of press-fitting process is the chosen lubricating material.

At wheel pairs press-fitting, a number of issues arise related to higher press-fitting effort, stick-slip motion to occur, contact surfaces damaging. They are caused by higher friction as well as significant differences in coefficients of static friction and of sliding friction, high contact pressure values at low speed of parts moving.

Purpose of a lubricant for press-fitting is to make axle inserting into the wheel hole easier due to friction reduction as well as to minimize efforts jumps while press running, to protect from forming scuffing and other defects on the mating surfaces, from jamming, to exclude parts overheating.

Greases and liquid lubricating materials are not able to fulfill the pointed functions as they separate the rubbing surfaces not effectively enough under conditions of high loads and slow sliding speeds.

The effective way to optimize the wheel pairs press-fitting process is to use pastes, that is the materials with high content of solid-lubricating components.

So, MODENGY 4002 concentrated paste based on molybdenum disulfide with high antiscuffing properties shows great results at forming wheel pairs of the passenger transport vehicles.

At the enterprise manufacturing rail transport vehicles, control wheel pairs press-fitting with applying MODENGY 4002 was held. This paste was tested for the purpose of being used at mass press-fitting of the parts as a substitute for foreign analogues.

According to the report by the inspection committee, at applying MODENGY 4002 paste, press-fitting is going in a regular mode: no scuffing, defects on the axle pre-wheel seat part of the axle, press-fitting efforts jumps were detected.

After 24 hours as the wheel pair has been formed, additional tests were held for the purpose of revealing parts mobility in their connection zone but no shift was detected in course of them.

According to the diagram analysis results of this press-fitting, the committee has delivered the judgement that MODENGY 4002 paste has successfully passed testing, and can be used in the wheel pairs press-fitting process.

Prior using the paste, it is required to stir the content of the container thoroughly up to a homogeneous state.

This product is applied onto clean and dry parts surfaces in a thin layer by rubbing-in movements by using a brush, a spatula, or a rag.

The finely dispersed powder of molybdenum disulfide in the composition of the paste fills the fills in the microroughnesses on the parts surfaces, thus enlarging their area of support and load-carrying capacity. A thin lubricating layer excludes mated surfaces damaging at wheel pairs press-fitting, and makes mounting them easier, stabilizes friction coefficient, and provides wheel pairs press-fitting process stability.