A sleeve should be used when pressing a bearing onto a shaft or into a housing For hot mounting, care must be taken to not overheat a bearing.

Bearings are limited in maximum temperature by the metallurgy of the rings as well as by use of any non-metallic components such as nylon cages or rubber seals. A good general rule of thumb is to heat bearings to a temperature 150 F greater than shaft temperature. This is sufficiently warm to allow the bearing to slide over the shaft while not hot enough to damage any components. In any case, do not heat open bearings above 250 F.

When installing heated bearings, the bearings should be pressed against the shaft shoulder and then the locknut installed and clamped against the bearing. As the bearing cools, it will shrink both radially (creating the interference fit on the shaft) and axially (potentially causing it to pull away from the shoulder). As the bearing cools, the locknut should be further tightened using an impact spanner wrench or, for small bearings, a regular spanner wrench, to keep the bearings tightened against the shoulder.

BearingInstallation Tool

• Application of the asymmetric tooth gears in the most loaded 2nd and 3rd spur gear stages of the main helicopter gearbox allowed to reduce contact stress by 9% and 6% accordingly and reach acceptable drive flank durability without increase of major gear dimensions. • Requirement of the non-ground tooth root fillet did not permit us to utilize its profile optimization [3] and, as a result, the bending stress reduction provided by asymmetric teeth is not significant. • Replacing the originally used spur symmetric tooth gears for the gears with asymmetric teeth allowed us to utilized more powerful and fuel-efficient turboshaft engines without a complete redesign of the helicopter gearbox. • As has been demonstrated by the similar type of symmetric and asymmetric gear comparative testing [4], the actual load capacity difference provided by asymmetric gears could be noticeably greater that analytically predicted. • Asymmetric tooth gears require the dedicated cutter (hob) for each of mating gears, which could be considered as limitation for their wider applications.

SKF wheelbearinginstallation instructions

Once the bearing is cooled, the locknut should be removed, the lockwasher placed against the bearing and the locknut reinstalled against the lockwasher. The locknut should be tightened until it is in intimate contact with the washer and the bearing is tight against the shoulder and then the appropriate lockwasher tab bent down into the locknut slot.

For bearings that have closures and are greased for life, 210 F is recommended as a maximum temperature so the 150 F difference over shaft temperature may have to be reduced somewhat for greased for life bearings. While ovens, hot plates and oil baths work, the simplest method to heat a bearing is with an induction heater.

Carlos Mousadi, Regional Commercial Leader at GE Vernova, shares how the company is supporting the Dominican Republic’s energy transition to renewables and natural gas.

Making sure the bearings are drawn hard against the shoulder is especially important for paired angular contact ball bearings. If the rings are not clamped tightly between the locknut and the shoulder, too much axial clearance may exist. When tightening the locknut with an impact spanner wrench, blows on the spanner will give a dull sound until the rings are in intimate contact. Once all of the components are tightly against each other, blows against the spanner will produce a ringing tone. This tone change indicates things are sufficiently tight.

Bearinginstallation methods

Prior to heat treatment, the gear teeth were machined, leaving the grinding stock about 0.20 mm on the tooth flanks and providing final root fillet profile. Non-ground tooth root fillet remains residual compressive stress after heat treatment, which increase tooth-bending strength. This required the gear hobs with a protuberance. However, due to the low number of pinion teeth of the 2nd and 3rd stages, these hobs could not provide the required tooth root fillet surface finish that reduces local stress concentration and crack initiation probability. This happens because the fillet surface of lower-number tooth gears is generated with fewer cuts than one for gears with greater number of teeth. In order to solve this issue, the pinion flanks were machined with conventional hobs (without protuberance) and then, before gear heat treatment, the pinion root fillets were ground. The 2nd stage pinion tooth profiles before and after heat treatment are shown in Figure 2.

• Fe – base material • C – 0.13-0.19% • Si – 0.17-0.37% • Mn – 0.50 – 0.90% • Cr – 2.65-3.25% • Ni – 0.4- 0.8% • S – <0.025% • P – <0.025%, Cu – < 0.30%.

About 25% of one of the engine power is used to drive the tail propeller through the spur gear z7 and the bevel gears z8, z9. The original bevel gear pairs had sufficient load capacity to withstand increased power of new engines and were not required any modernization. The 2nd and 3rd stage spur gears had to be redesigned to reduce contact stress level and to achieve sufficient tooth flank surface durability.

Klaus Brun and Rainer Kurz discuss root-cause analysis—what it is, its methodologies, and why it’s so important to managing turbomachines.

One such application of asymmetric gears in the turboprop engine gearbox is described in “Application of Gears with Asymmetric Teeth in Turboprop Engine Gearbox” [1]. In that instance, the gearbox was developed from scratch for new engine and new aircraft. However, there are cases of upgrading existing aircrafts with more powerful engines that require higher load capacity gearboxes. One of such case is described in this paper. The paper also presents design and performance data of modernized asymmetric gears in comparison with original symmetric gears.

How toinstall bearinginto housing

For small bearings, defined as bearings with outer diameters of 4 inches or less, the bearings can be cold mounted. Above that size, heating the bearings is recommended. When cold mounting, force must be directed against the ring with the interference. Typically this means pressing against the inner ring because the bearing usually is mounted with an interference fit on the shaft.

Force may be applied using an arbor press or an impact sleeve and hammer. No blows should be directed to the bearing itself. Rather, a sleeve should contact the bearing and blows be directed against the end of that sleeve. Use of a dead blow hammer is also suggested.

This article contains excerpts from the paper, "Bearing Maintenance Practices to Ensure Maximum Bearing Life" by Brian P Dahmer of SKF USA.

The process is quick, accurate, repeatable and safe. Make sure operating instructions and warnings are followed because induction heaters create a strong magnetic field which can be a hazard. When heating bearings, it is critical to use an induction heater that has a demagnetization cycle built in. During the heating process, the bearing is magnetized by the induced current. If that magnetic field is not eliminated, the bearing will attract all ferrous debris in the oil. Usually the heater’s demagnetization cycle operates just before the heater shuts off so the full heating cycle must be completed before the bearing is removed from the heater and installed.

Sphericalbearinginstallation

Klaus Brun and Rainer Kurz discuss root-cause analysis—what it is, its methodologies, and why it’s so important to managing turbomachines.

The heat-pump system uses Rhine water as its energy source and operates with a natural refrigerant in a closed-loop system.

How toinstallabearingon a shaft without a press

Application of asymmetric tooth gears for aerospace propulsion drives allows for considerably increased power transmission density, potentially increasing their load capacity and reducing size and weight. However, there are not many practical implementations of such gears.

During this episode, the Myth Busters break down the many terms associated with degradation, what components degrade, how it can be measured and minimized, and more.

• Drive flank pressure angle should not exceed 32o to limit the maximum radial load and keep original bearings; • Minimum drive flank contact ratio is 1.3; • Minimum tooth tip thickness is 2.3 mm for the 2nd stage gears and 3.1 mm for the 3rd stage gears to avoid the harden through tooth tip; • Minimum coast flank pressure angle in the 2nd stage is 20°, because the coast flanks of one of the gearbox branches are used to transmit torque to the tail propeller; • The tooth root fillet is not ground after heat treatment. Its profile should not interfere with the grinding wheel trajectory.

SKFbearingInstallation and Maintenance Guide PDF

During this episode, the Myth Busters break down the many terms associated with degradation, what components degrade, how it can be measured and minimized, and more.

In this episode of the TurboTime podcast, Daniel Tegtmeier, Director of EthosEnergy’s Performance Center, talks about remote operations and monitoring.

Prior to heat treatment, the gears of both the 2nd and 3rd stages were machined with the protuberance hobs. The 3rd stage gear tooth profiles before and after heat treatment are shown in the Figure 3.

After the tooth cutting, the gears are carburized and heat-treated to achieve a tooth surface hardness of 59-60 HRC with a case depth of 1.2-1.4 mm. The core tooth hardness is 34-42 HRC.

The heat-pump system uses Rhine water as its energy source and operates with a natural refrigerant in a closed-loop system.

1. A.S. Novikov, A.G. Paikin, V.L. Dorofeyev, V.M. Ananiev, A.L. Kapelevich, “Application of Gears with Asymmetric Teeth in Turboprop Engine Gearbox,” 10th International ASME Power Transmission and Gearing Conference, September 4-7, 2007, Las Vegas, Nevada, USA. It was also published in Gear Technology, January/February 2008, 60 – 65. 2. E. B. Vulgakov et al., Aviation Gearboxes, Handbook, Mashinostroenie, Moscow, 1981 (in Russian) 3. A.L. Kapelevich, Direct Gear Design, CRC Press, Taylor Francis Group, 2013 4. F.W. Brown, S.R. Davidson, D.B. Hanes, D.J. Weires, and A. L. Kapelevich, “Analysis and Testing of Gears with Asymmetric Involute Tooth Form and Optimized Fillet Form for Potential Application in Helicopter Main Drives,” AGMA Fall Technical Meeting, Milwaukee, Wisconsin, October 18-19, 2010, (10FTM14). It was also published in Gear Technology, June/July 2011, 46 – 55

Carlos Mousadi, Regional Commercial Leader at GE Vernova, shares how the company is supporting the Dominican Republic’s energy transition to renewables and natural gas.

The original spur gears were designed traditionally using the preselected basic rack and its addendum modification (X-shift). The modernized spur gears with asymmetric teeth were constructed using the Direct Gear Design® method [3].

Final gear machining includes tooth grinding and honing. Asymmetric gears require special setup for both these operations.

The gear blanks’ position during machining must provide the asymmetric teeth pointed in certain direction (clockwise or counterclockwise). Otherwise, the drive flank of one gear will be positioned in contact with the coast profile of the mating gear, which makes assembly impossible.

How toinstallbearings on a shaft

Research and development of asymmetric tooth spur gears for modernization of the light multipurpose helicopter gearbox has amplified its load capacity to utilize more powerful turboshaft engines.

The compound gear that contains the 2nd stage gear and 3rd stage pinion is shown in Figure 5. In this compound gear, the 2nd stage gear is driven and the 3rd stage pinion is driving. For the asymmetric version of compound gear (Figure 5b) this means that asymmetrical directions (tooth inclinations) of those gear and pinion be opposite and in relation to gear rotation direction. This is critical for a proper gearbox assembly.

In this episode of the TurboTime podcast, Daniel Tegtmeier, Director of EthosEnergy’s Performance Center, talks about remote operations and monitoring.

A light multipurpose helicopter was upgraded with new turboshaft engines that required modernization of the main gearbox to boost its load capacity within existing size, weight, and lifetime limitations, keeping sufficient safety factors and reliability. This task was solved by implementation of spur gears with the asymmetric tooth profiles in the most loaded second and third stages of the gearbox.

While torque specifications are published for locknuts, they can be difficult to apply because specific thread tolerances, roughness and lubrication (or lack thereof), will change locknut torque substantially. There is an upper bound for what axial clamping force should be applied to a bearing. This maximum axial clamping force is equal to ¼ of the static capacity (Co) for the bearing. Any greater clamp force may deform the rings changing internal load distribution and contact pressures thereby reducing life.

Power from two turboshaft engines is transmitted by the turbine shafts 1 through the bevel gears z1, z2 and then the spur gears z3, z4, and z5 to the bull gear z6 connected to the main propeller shaft 2.

Under its updated designation, MILES will design and develop new commercial liquefied CO2 carriers and provide functional design for alternatively fueled ships.

Under its updated designation, MILES will design and develop new commercial liquefied CO2 carriers and provide functional design for alternatively fueled ships.

Installing new bearings is a critical step in maximizing bearing reliability. If the bearings are incorrectly mounted or damaged during installation, life will be shortened. Therefore, use of sound proven techniques is critical.

Geometry of asymmetric teeth does not allow using the traditional Lewis equation to define the tooth bending stress. The FEA subroutine integrated in the Direct Gear Design software was used for comparison of symmetric and asymmetric gear tooth bending stresses. Examples of the finite element mesh and stress isograms are presented in Figure 4.

The correct tools should be used for all of these activities. Attempting to use a drift or piece of bar stock may succeed in tightening the locknut but there is a risk of damaging the nut and/or the bearing. Additionally, small pieces may break off of improvised tools and these pieces could enter the bearing and cause damage during operation. Lastly, a torch should never be used to heat the bearing prior to installation. Such direct heat will permanently damage the heat treatment of the bearing and shorten life.