A double-hung window consists of two sashes: an upper, outside sash that moves down and a lower, inside one that moves up. A pulley and weight sys-tem or balances located in the jambs control the movement of the sashes. Double-hung windows may be made from wood, aluminum, or vinyl.

As a wood window sash ages, it may begin to misfit its frame, or the system controlling sash movement may break down. Some common window problems and their solutions are discussed below. Instructions for removing wood sashes and replacing a window’s balance system appear.

Metal and vinyl windows seldom require repairs. To keep them oper-ating smoothly occasionally clean the channels with very fine steel wool and coat them with silicone spray

A Double-hung Windows

Correcting ill-fitting sashes
Wood double-hung window sashes that don’t fit or don’t move correctly are annoying. Often, a simple sash or stop repair can restore the window to good working order. If none of the simple re-pairs described below works, you’ll need to remove and reposition the
stops (see facing page).

Freeing a stuck sash. If a sash is temporarily stuck because moisture has swelled the wood, a change of weather may correct it. For a sash that’s paint-bound, use one of the
methods shown on the facing page.

Freeing a tight sash. If a sash moves reluctantly the sash channels may need to be cleaned and lubricated or even widened (see facing page). If the sash itself is too wide, you may
need to sand it down or, in severe cases, plane it.

Correcting a loose sash. A sash that rattles and lets in unwanted air is too loose. Often, installing spring-type weatherstripping can correct the prob-lem.

If the gap isn’t too wide and the stop is nailed rather than screwed, you can move the stop slightly without actu-ally removing it. Score the paint be-tween the stop and jamb and place a cardboard shim between the stop and sash. Holding a block of wood against the stop to protect it, hammer toward the sash along the length of the stop until the paint breaks and the stop rests against the shim. Secure the stop with finishing nails.

If you need to remove and re-position the stop to correct a wide gap, see the instructions on the facing page. Tightening sash joints. If a sash’s joints are loose, you’ll have to remove the sash from the frame. Clean the joints; then repair the frame as shown.

Repairing window balance systems
If a sash refuses to remain open or closed, or if it jams in one position, repair or replace the balance system. Your windows may have a traditional weight and pulley balance system like that shown above, or a more modern spiral-lift, tension-spring, or cord balance system. Instructions for repairing and replacing balances appear.

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Three Ways To Free A Paint-Bound Sash

Three Ways To Loosen A Tight Sash

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Epositioning The Stops

Broken Balance Systems

When a window’s balance system is broken, the window will not remain open or closed. The repair depends on the type of system-pulley and weight, spiral-lift, tension-spring, or cord -
used in the window.

To repair or replace a balance system, you’ll have to remove one or both sashes (see below). If just the lower sash is affected, remove only that one. If the repair involves the upper sash, remove both. Be sure to take off any interlocking weatherstripping before
removing the sash.

Pulley & weight system
Pulleys and weights traditionally operate double-hung windows. The weights are suspended on cords or chains located behind the side jambs. If you’re replacing a broken cord, it’s a good idea to replace all the cords in the window at the same time, preferably with long-lasting chains, as shown below. To replace a defective chain, fol-low the instructions for cords. Before detaching the old chain, be sure to im-mobilize the weights on each side by drawing up the chains until the weights touch the pulleys. Slide a nail through a link at each pulley to hold the chains in place; then detach the chains from the sash. Once the new chains are in place, replace the upper sash, parting strips, access plates, bottom sash, and stops, in that order, checking the operation of each sash as you go.

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Removing Wood Sashes & Replacing Cords

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Spiral-lift system
In a spiral-lift balance system, a spring-loaded spiral rod encased in a tube rests in a channel in the side of the stile. The top of the tube is screwed to the side jamb; the rod is attached to a mounting bracket on the bottom of the sash (see illustration below). Each sash has two such units.

Adjusting the tension. With a spiral-lift balance, adjusting the spring tension may be all that’s needed to make the window operate properly If the sash tends to creep up, loosen the spring by detaching the tube from the sash channel and letting the spring unwind a bit. If the sash keeps sliding down, turn the rod clockwise a few times to tighten the spring. If this doesn’t help, you’ll need to replace the unit.

Replacing the unit. To remove a broken balance, pry off the stop on the affected side (page 55) and unscrew the tube where it’s fastened to the top of the side jamb. Let the spring unwind; then raise the sash 6 to 8 inches and angle it out of the frame. If the rod is
attached to the bottom of the sash with a detachable hook, unhook it; support the sash in a raised position with a wood block, and unscrew and remove the mounting bracket.

Position a new tube in the channel and screw it into the top of the side jamb. Pull the spiral rod down as far as it will go and turn it clockwise about four complete turns to tighten the spring. Let the rod retract into the tube far enough so you can fasten the mounting bracket to the bottom of the sash. Replace the sash.

Check the movement of the sash by sliding it up and down, and adjust the tension as described at left. Once the window is operating properly reposition the stop (page 55).

Tension-spring & cord systems
In a tension-spring balance system, each sash is operated by two balance units with spring-loaded drums inside; the units fit into the side jamb near the top. A flexible metal tape hooks onto a bracket screwed into a groove in the sash.

A cord balance system, not shown here, is a variation of the tension-spring system. Two spring-loaded reel units fit into each corner of the top jamb. Nylon cords connect the units to each sash; plastic top and side jamb liners conceal the working parts.

Replacing the unit. If any part of a tension-spring or cord balance system breaks, you’ll have to remove the unit and install a new one.

To remove a tension-spring unit, remove the stop on the affected side (page 55) and ease out the sash. Un-hook the tape from the bracket and let it wind back on the drum. Remove the screws from the drum plate and pry the unit out of the jamb pocket.

Insert the new balance into the jamb pocket and secure it with wood screws. Using needlenose pliers, pull the tape down and hook the end to the bracket on the sash. Replace the sash, check its operation, and reposition the stop (page 55).

A cord balance unit is replaced in the same way as a tension-spring unit. You’ll need to remove the jamb liners in order to remove the sash and then pry out the balance unit from the top jamb.

Replacing A Spiral-Life Unit

Replacing A Tension-Spring Unit

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Distributed Forces

The most common distributed forces acting on a body are parallel force
systems, such as the force of gravity. These can be represented by one or
more concentrated forces to facilitate the required analysis. Several basic
cases of distributed forces are presented here. The important topic of stress
analysis is covered in mechanics of materials.

Center of Gravity

The center of gravity of a body is the point where the equivalent resultant force
caused by gravity is acting. Its coordinates are de?ned for an arbitrary set of
axes as

(1.2.14)

where x, y, z are the coordinates of an element of weight dW, and W is the
total weight of the body. In the general case dW = ? dV, and W = ?? dV,
where ? = speci?c weight of the material and dV = elemental volume.

Centroids

If ? is a constant, the center of gravity coincides with the centroid, which is
a geometrical property of a body. Centroids of lines L, areas A, and volumes
V are de?ned analogously to the coordinates of the center of gravity,

For example, an area A consists of discrete parts A₁, A₂, A₃, where the
centroids x₁, x₂, x₃ of the three parts are located by inspection. The x
coordinate of the centroid of the whole area A is x  obtained from
Ax = A₁x₁ + A₂x₂ + A₃x₃.

Surfaces of Revolution. The surface areas and volumes of bodies of revolution
can be calculated using the concepts of centroids by the theorems of Pappus
(see texts on Statics).

Distributed Loads on Beams

The distributed load on a member may be its own weight and/or some other
loading such as from ice or wind. The external and internal reactions to the
loading may be determined using the condition of equilibrium.

External Reactions. Replace the whole distributed load with a concentrated
force equal in magnitude to the area under the load distribution curve and
applied at the centroid of that area parallel to the original force system.

Internal Reactions. For a beam under a distributed load w(x), where x is
distance along the beam, the shear force V and bending moment M are
related according to Figure 1.2.25 as

FIGURE 1.2.25 Internal reactions in a beam under distributed loading.

Other useful expressions for any two cross sections A and B of a beam are

Example 7 (Figure 1.2.26)

FIGURE 1.2.26 Shear force and bending moment diagrams for
a cantilever beam.

Distributed Loads on Flexible Cables

The basic assumptions of simple analyses of cables are that there is no
resistance to bending and that the internal force at any point is tangent to the
cable at that point. The loading is denoted by w(x), a continuous but possibly
variable load, in terms of force per unit length. The differential equation of
a cable is

where T_o = constant = horizontal component of the tension T in the cable.
Two special cases are common. Parabolic Cables. The cable supports a load w
which is uniformly distributed horizontally. The shape of the cable is a
parabola given by

In a symmetric cable the tension is

Catenary Cables. When the load w is uniformly distributed along the cable,
the cables shape is given by

The tension in the cable is T = T_o + wy.
Friction A friction force F (or ^, in typical other notation) acts between
contacting bodies when they slide relative to one another, or when sliding tends
to occur. This force is tangential to each body at the point of contact, and its
magnitude depends on the normal force N pressing the bodies together and on
the material and condition of the contacting surfaces. The material and surface
properties are lumped together and represented by the coef?cient of friction ?.
The friction force opposes the force that tends to cause
motion, as illustrated for two simple cases in Figure 1.2.27.

FIGURE 1.2.27 Models showing friction forces.

The friction forces F may vary from zero to a maximum value,

F_max = ?N (0?F?F_max)

depending on the applied force that tends to cause relative motion of the bodies.
The coef?cient of kinetic friction ?_k (during sliding) is lower than the coef?cient
of static friction ? or ?_s; ?_k depends on the speed of sliding and is not easily
quanti?ed.

Angle of Repose

The critical angle ?c at which motion is impending is the angle of repose,
where the friction force is at its maximum for a given block on an incline.

So ?_c is measured to obtain ?_s. Note that, even in the case of static,
dry friction, ?s depends on temperature, humidity, dust and other contaminants,
oxide ?lms, surface ?nish, and chemical reactions. The contact area and
the normal force affect ?_s only when signi?cant deformations of one or both
bodies occur.

Classi?cations and Procedures for Solving Friction Problems

The directions of unknown friction forces are often, but not always,
determined by inspection. The magnitude of the friction force is obtained from
F_max = ?_sN when it is known that motion is impending.
Note that F may be less than F_max. The major steps in solving problems
of dry friction are organized in three categories as follows.

Wedges and Screws

A wedge may be used to raise or lower a body. Thus, two directions of motion
must be considered in each situation, with the friction forces always opposing
the impending or actual motion. The self-locking
A. Given: Bodies, forces, or coef?cients of friction are known. Impending
motion is not assured: F ? ?_sN.
Procedure: To determine if equilibrium is possible:
1. Construct the free-body diagram.
2. Assume that the system is in equilibrium.
3. Determine the friction and normal forces necessary for equilibrium.
4. Results: (a) F < ?_sN, the body is at rest.
(b) F > ?_sN, motion is occurring, static equilibrium is not possible. Since
there is motion, F = ?_kN. Complete solution requires principles of dynamics.
B. Given: Bodies, forces, or coef?cients of friction are given. Impending
motion is speci?ed. F = ?_sN is valid.
Procedure: To determine the unknowns:
1. Construct the free-body diagram.
2. Write F = ?sN for all surfaces where motion is impending.
3. Determine ?s or the required forces from the equation of equilibrium.
C. Given: Bodies, forces, coef?cients of friction are known. Impending
motion is speci?ed, but the exact motion is not given. The possible motions may
be sliding, tipping or rolling, or relative motion if two or more bodies are
involved. Alternatively, the forces or coef?cients of friction may have to
be determined to produce a particular motion from several possible motions.
Procedure: To determine the exact motion that may occur, or unknown
quantities required:
1. Construct the free-body diagram.
2. Assume that motion is impending in one of the two or more possible ways.
Repeat this for each possible motion and write the equation of equilibrium.
3. Compare the results for the possible motions and select the likely event.
Determine the required unknowns for any preferred motion.

Wedges and Screws

A wedge may be used to raise or lower a body. Thus, two directions of
motion must be considered in each situation, with the friction forces always
opposing the impending or actual motion. The self-locking aspect of a wedge
may be of interest. The analysis is straightforward using interrelated
free-body diagrams and equilibrium equations.
Screw threads are special applications of the concept of wedges. Square
threads are the easiest to model and analyze. The magnitude M of the moment
of a couple required to move a square-threaded screw against an axial load P is

M = Pr tan(? + ?)

where  r  = radius of the screw
? = tan¹ (L/2?r) = tan1 (np/2?r)
L  = lead = advancement per revolution
n  = multiplicity of threads
p  = pitch = distance between similar points on adjacent threads
? = tan¹?
The relative values of ? and ? control whether a screw is self-locking;
? > ? is required for a screw to support an axial load without unwinding.

Disk Friction

Flat surfaces in relative rotary motion generate a friction moment M opposing
the motion. For a hollow member with radii Ro and Ri, under an axial force P,

The friction moment tends to decrease (down to about 75% of its
original value) as the surfaces wear. Use the appropriate ?s or ?k value.

Axle Friction

The friction moment M of a rotating axle in a journal bearing
(sliding bearing) is approximated (if ? is low) as

M = Pr?

where  P  = transverse load on the axle
r  = radius of the axle
Use the appropriate ?_s or ?_k value.

Rolling Resistance

Rolling wheels and balls have relatively low resistance to motion compared
to sliding. This resistance is caused by internal friction of the materials
in contact, and it may be dif?cult to predict or measure.
A coef?cient of rolling resistance a is de?ned with units of length,

where  r  = radius of a wheel rolling on a ?at surface
F  = minimum horizontal force to maintain constant speed of rolling
P  = load on wheel
Values of a range upward from a low of about 0.005 mm for hardened
steel elements.

Belt Friction

The tensions T1 and T2 of a belt, rope, or wire on a pulley or drum are
related as

T₂ = T₁e^?? (T₂ > T₁)

where ? = total angle of belt contact, radians (? = 2?n for a member wrapped
around a drum n times).
Use ?_s for impending slipping and ?_k for slipping.
For a V belt of belt angle 2?,

T₂ = T₁e^??/sin?

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By : E-book Mechanical_Engineering_Handbook

Caulking compound helps keep air, moisture, and insects out of your house and costly heated and cooled air in-side. But caulking eventually dries out and requires renewal, so always check for cracked, loose, or missing caulking as part of your spring and autumn maintenance inspections.

The different types of caulking compound, the areas around your house that require caulking, and the
application techniques are discussed below.

Types of caulking. The five basic types of exterior caulking are elas-tomers, butyl rubber, acrylic latex, non-
acrylic latex, and oil base. The chart on page 25 lists the characteristics of each. When making your choice,
weigh price against each compound’s expected lifetime and consider the kinds of materials to which the caulking must adhere.

Caulking comes in four forms: as disposable cartridges for use with a half-barrel caulking gun, in a can for
application with a full-barrel caulking gun or a putty knife, in a small squeeze tube, and as rope caulk. The
half-barrel caulking gun fitted with a cartridge is the most popular dis-penser, since it’s the easiest to use for applying an even bead of compound. Use rope caulk as a temporary filler for very wide cracks or jointsit may not adhere for very long.

CAUTION: Before you buy any caulking, read the label; Some types won’t work in cracks or joints less than
1/4 inch wide; others work well only in narrow cracks. Take note of any pre-cautions and follow the directions when you’re using the product. Where to caulk. Generally you’ll need to caulk in areas where different sur-faces meet. Here are some of the places requiring caulking:

On the roof where one flashing meets another flashing, between flashing and a roof or dormer sur-
face, and where a chimney flue, plumbing or electrical pipe, attic fan, or skylight protrudes through the roof surface.

On the siding where the siding and .trim meet at corners; around window and door frames; between badly fitting pieces of siding; where pipes, framing members, and other pro-trusions pass through the siding;
and where the siding meets the foun-dation, patio or deck, or any other different part of the house. It’s also a good idea to examine interior window and door frames, es-pecially between sliding door or win-dow tracks and the sill or jamb.

Applying caulking. Before you can apply new caulking, you’ll have to re-move the old or damaged sections.
First, dig out or chip off all of the old caulking with a putty knife, old screw-driver, or scraper. Then brush the area with a wire brush to remove debris and wipe the surface with a cloth soaked in the appropriate solvent for the type of caulking you’re removing. Before applying the new caulking, check the label to see if you need to prime the surface. Plan to caulk on a warm, dry day when the temperature is between 50? and 70?F In hotter weather, refrigerate the caulking for an hour or two before use so the com-pound won’t run.

Directions for using a half-barrel caulking gun appear below. It may take a bit of practice to get the bead of caulking to flow evenly Start by holding the gun at a 45? angle to the surface; then, moving the gun across the surface, squeeze the trigger to keep the caulking flowing smoothly Make sure the compound fills the crack completely and overlaps adjoining surfaces evenly If the crack is deep, apply two beads. If you’re using rope caulk, simply unroll the amount you need and use your fingers to stuff it into the crack.

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Using A Half-Barrel Caulking Gun

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Controlling Moisture In A Basement

The most common basement prob-lem a homeowner faces is water. The problem can range In seriousness
from damp walls and floors to water gushing out of a crack. The source may be simply humid air condensing on cool surfaces or ground water finding its way through your basement’s walls or floor. Before you can correct the problem, you’ll need to determine the source of the water.

Where’s the water coming from? If you can see water flowing out of a crack in a wall or floor, you know that the source is ground water. In the absence of such obvious evidence, you’ll have to make a test to deter-
mine whether the dampness In your basement is caused by condensation or water from the ground.

Cut two 12-inch squares of plastic sheeting or aluminum foil. Tape one to the inside of an outside wall and one to the basement floor (make sure the surfaces are thoroughly dry). After two or three days, remove the plastic or foil and examine the surface that was next to the wall or floor. If it’s dry, the culprit is condensation; if it’s wet, it’s a sign that ground water is seeping through the wall or floor.

Reducing condensation
When the basement air is humid, the moisture in the air may condense on cool surfaces, such as cold water
pipes, concrete or masonry walls, or a concrete floor.

Though you can apply a coating (see facing page) to reduce conden-sation, it’s best to lower the air’s humidity, using these suggestions:

Improve ventilation by opening basement windows or installing an exhaust fan (page 185) In the
basement.

Raise the temperature in the basement.

Vent moist air from a clothes dryer to the outside.

Install a dehumidifier in the base-ment area.

Insulate cold water pipes and basement walls.

Common Causes Of A Wet Basement

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Controlling ground water
When water collects next to a founda-tion wall or when the water table (the water level under your property) is higher than your basement floor, hydrostatic pressure can force water through joints, cracks, and porous areas in concrete walls and floors and through cracked or crumbling mortar joints in masonry walls. Poor con-struction practices clogged or non-existent footing drains, poorly applied or nonexistent waterproofing on the foundation, through-the-wall cracks, and improper grading often are the cause.

Correcting any of these problems is a major job that requires digging out the foundation to the bottom of
the footings. Though this may well be the most permanent repair, first try the remedies that follow. If they don’t work, then you’ll have to contact a foundation engineer or contractor for a more lasting solution.

CAUTION: If you see horizontal cracks in a wall that’s bowing inward, long, vertical cracks wider than 1/4
inch, or a crack that’s getting wider (measure it periodically), you have a structural problem. Contact a soils or foundation engineer at once. Exterior remedies. Roof and surface water collecting next to the foundation
may be causing the dampness in your basement. Make a careful inspection outside, using the following checklist, and correct any problems you find.

Gutters and downspouts should be clear and should direct water away from the foundation. To clean gutters and improve drainage at downspouts, see pages 36-37.

Proper grading around the house the ground should drop 1 inch per foot for the first 10 feet away from the foundation walls is essential to ensure good surface drainage.

Planting beds next to the foundation should not allow water to collect or pool there.

Window wells around basement windows should be free of debris, have good drainage, and be prop-
erly sealed at the wall. Interior remedies. These simple inte-rior repairs may alleviate or cure your water problems:

Apply a coating to the wall. Most coatings are painted on, though some are plastered on with a trowel.
Except for epoxy coatings, all are cement-base products with various additives. Epoxy does the best job. Look for coatings at home improvement or masonry supply centers.

Patch cracks in walls and floors with Portland or hydraulic cement patching compound. Hydraulic cement expands and dries quickly, even in wet conditions. Cracks wider than 1/8 inch should be undercut chiseled out so the bot-tom of the crack is wider than the top (see illustration at top left). This will prevent water pressure from popping out the patch.

Chisel out a groove along the wall if water is entering through a floor/wall joint. Fill the groove with
hydraulic or epoxy cement and cove (form in a concave shape) as shown below.

Chisel out cracked mortar joints in masonry walls and fill them with hydraulic or epoxy cement. Water that comes through cracks in a concrete floor or through the joint between the floor and wall is caused by hydrostatic pressure. In addition to those described above, remedies in-clude installing drains under the floor, adding a sump pump, or laying a new floor over a waterproof membrane placed on the old floorall jobs for professionals.

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Patching A Crack

Patching A Floor/Foundation Joint

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