This is called "self lapping" 24 air is older. You have to move the handle to the right to exhaust the air and watch the equalizing reservior level fall. When you reach the desired brake pipe pressure you have to stop the exhaust as in "lap" the handle and then the brake valve will maintain that pressure.
There are some other differences but this is the biggie. Also, a variant is the 24RLMC1, the RL meaning "road locomotive", and MC meaning "maintaining conversion", which eliminates the need to manually "lap" or close off the air at the desired brake application setting. OH MY This is truly part of the art of being an engineer.
Most of the 6 automatic brake valves were modified with a stop welded in the "full release" position to keep the handle from being moved past "running" and overcharging the brake pipe. Many times when dumping side dumps the extra pressure was desireable and one only needed to adjust the feed valve to accomplish what the "full release" did before it was blocked off. The 26 system is a real improvement in that all of the pressure is maintained by "O Rings" rather than the lapped surfaces on the older 6 and 24 equuipment.
The inspection period is also increased to basically 3 years as opposed to two years on the older equipment. There are basically two different 26 systems for switchers at least ; the 26L for new installations and the 26NL which uses the existing 6 reservoirs. I'm not in front of my schematics or I could be more definate. Dick Samuels www. Isn't that interesting? My experience with brake valves was with San Francisco's old streetcars. Just about all had simple valves that operated like a To add air to the brake cylinder or reduce it, the motorman moved the brake handle back and forth frequently, moving small bits of air at a time.
The control systems comprise diaphragms and springs arranged in a series of complex valves and passages within the steel valve block. Distributors with all these features will normally be provided on passenger trains or specialist high-speed freight vehicles.
Two Pipe Systems A problem with the design of the standard air brake is that it is possible to use up the air in the auxiliary reservoir more quickly than the brake pipe can recharge it. Many runaways have resulted from overuse of the air brake so that no auxiliary reservoir air is available for the much needed last application.
The problem can be overcome with a two-pipe system as shown in the simplified diagram below. This is simply a supply pipe running the length of the train which is fed from the compressor and main reservoir.
It performs no control function but it is used to overcome the problem of critical loss of pressure in the auxiliary reservoirs on each car. A connecting pipe, with a one-way valve, is provided between the main reservoir pipe and the auxiliary reservoir. The one-way valve allows air from the main reservoir pipe to top up the auxiliary reservoir. The one- way feature of the valve prevents a loss of auxiliary reservoir air if the main reservoir pressure is lost.
Another advantage of the two-pipe system is its ability to provide a quick release. Because the recharging of the auxiliaries is done by the main reservoir pipe, the brake pipe pressure increase which Two pipe systems have distributors in place of triple valves. One feature of the distributor is that it is designed to restrict the brake cylinder pressure so that, while enough air is available to provide a full brake application, there isn't so much that the brake cylinder pressure causes the blocks to lock the wheels and cause a skid.
This is an essential feature if the auxiliary reservoir is being topped up with main reservoir air, which is usually kept at a higher pressure than brake pipe air. Needless to say, fitting a second pipe to every railway vehicle is an expensive business so it is always the aim of the brake equipment designer to allow backward compatibility - in much the same way as new computer programs are usually compatible with older versions.
Most vehicles fitted with distributors or two-pipe systems can be operated in trains with simple one-pipe systems and triple valves, subject to the correct set-up during train formation. Self Lapping Brake Valves Self lapping is the name given to a brake controller which is position sensitive, i. The closer the brake handle is to full application, the greater the application achieved on the train.
The brake valve is fitted with a This type of brake control is popular on passenger locomotives. Other Air Operated Equipment On an air brake train, the compressed air supply is used to provide power for certain other functions besides braking.
Comment The air brake system is undoubtedly one of the most enduring features of railway technology. It has lasted from its initial introduction in to the present day and in some places, still hardly different from its Victorian origins. There have been many improvements over the years but the skill required to control any train fitted with pure pneumatic brake control is still only acquired with long hours of practice and care at every stage of the operation.
It is often said that whilst it is easy to start a train, it can be very difficult to stop it. It is purely compressed air brake system known as independent brake system. Valve has three positions i. Quick release, release and application. Purpose of this system Independent Brake System is designed to apply and release brake on locomotive. When locomotive is moving itself Independent Brake is applied. This system is introduced to run air brake train. Air Brake system can sustain better brake power and can haul a long train.
System is designed for Locomotive brake application during train brake application through A9 handle. This is known as synchronising brake system also. Description of loco brake system The SA9 Valve handle is kept normally in release position right side. MR air is always available at port no.
When handle is brought in application potion left side than SA9 port 30 connects port 20 and starts supplying pilot air to C2- Relay air valve. The pilot air passes through MU2B Valve port no. See the line diagram of loco brake system. The pilot air pressure depends upon the handle position, at maximum it The C2-relay air valve actuates after getting pilot air and connects MR pressure to brake cylinders of locomotive through port no.
The brake cylinder pressure depends upon pilot air pressure, supplied into C2-Relay chamber through port no. For full brake application SA9 handle is moved to maximum travel position. When SA9 handle is placed in release position, loco brakes are released. How MR air is reduced to 3. SA9 Brake valve handle is normally kept in release position. Loco brake can be applied through SA9 Valve handle.
It can be applied any desired pressure between the minimum and maximum. This pressure will be automatically maintained in the locomotive brake cylinders against normal leakage from them. The locomotive brake can be graduated on and off with either the automatic A9 or the independent brake valves SA9. It is always possible to release the locomotive brakes with the SA9 valve. Additional C2- In this position brakes are found released position.
When A9handle is moved to application zone, B P pressure drops through Add. C2-Relay valve, port 3 is connected to exhaust. In this condition brakes are applied. Brake release When A9 handle is moved to release position, Add. Purpose of the system Feed Pipe system is introduced to reduce the release time after brake application in air brake trains. Air reaches directly to feed valve through cut-out cock. A-9 Automatic Brake Valve The A-9 Automatic Brake Valve is a compact self-lapping, pressure maintaining Brake Valve which is capable of graduating the application or release of locomotive and train brakes.
It also maintains air pressure drop in the system according to its handle position. Construction The A-9 Automatic Brake valve consists of a self-lapping regulating portion, which supplies or exhausts the brake pipe pressure, and a vent valve which is actuated only when the brake valve handle is placed in Emergency position for the purpose of venting brake pipe pressure at an emergency rate.
The self-lapping portion is actuated by regulating cam dog 3 on the brake valve handle shaft 32 which controls the supply or exhaust of brake pipe pressure.
The vent valve 19 is actuated by special cam dog 23 attached to the brake valve handle which is operative only in Emergency position of the brake valve handle.
There is an inlet valve assembly along with double ball check valve, which moves up and down, when handle moves. Operation Charging The A9 automatic brake valve handle is kept at release position normally. The regulating cam dog 3 holds the inlet and exhaust unit at farthest down ward position. While the regulating valve spring 12 will cause the double ball check assembly 5 to be seated at the exhaust valve and unseated at the inlet valve see diagrammatic.
Main reservoir air is supplied at port No. This air in port 5 is also ported through a choke passage to the face of regulating valve diaphragm 9. When the pressure on the face of the regulating valve diaphragm 9 overcomes regulating valve spring 12 tension, the regulating valve diaphragm assembly moves down ward and allow the inlet valve spring to seat the double ball check assembly at the inlet valve seat.
The A-9 Automatic Valve resumes a lap position. Application The inlet valve assembly will carry the double ball check assembly with it. This movement will unseat the double ball check valve at exhaust valve seat, thus allowing brake pipe air to flow to exhaust. With the reduction of pressure on regulating valve diaphragm 9, the regulating valve spring 12 will cause a movement of the diaphragm assembly toward the inlet valve and the double ball check valve assembly will be seated at the exhaust valve seat again.
The brake valve is to assume a lap position. Pressure drop in- Minimum reduction This movement will cause the double ball check valve 5 to be unseated at the inlet valve. Main reservoir air will then flow through the inlet valve to port No. When the force have equalized across the regulating valve diaphragm 9, the double ball check assembly 5 will again seat at the inlet valve due to the force of the inlet valve spring and the brake valve will assume a lap position.
Thus it can be seen that the brakes can be graduated off in proportion to the brake valve handle movement from an application position toward release position. Emergency position When the brake valve handle is moved to emergency position, the brake valve will perform all the service operations. In the emergency position, the emergency cam dog 23 is actuated through special cam dog 23 to open vent valve 19 and allow brake pipe air to be vented at an emergency rate.
Release after an emergency is the same as previously described under release after service. The SA-9 Brake Valve has three positions: quick release, release and application. It is supposed to maintain graduated application and release according to its handle position. Construction The SA9 Independent Brake Valve consists of a self—lapping regulating portion, which supplies or exhausts air pressure for piloting the graduated application or release of brake cylinder pressure on the locomotive.
This brake valve also includes a quick release valve. Both the self-lapping regulating portion and quick release valves of the SA9 Independent Brake valve is actuated by cams attached to the brake valve handle stem. It has regulating valve spring 12, which regulates supply pressure. Exhaust valve spring 7 regulates the movement of exhaust valve. Inlet valve spring keeps Quick release valve 17 keeps port no.
Operation Charging In the release position of the brake valve handle, the inlet valve, due to the spring tension of exhaust valve Sparing 7, is positioned at its farthest travel from the regulating valve diaphragm assembly. Which will unseat the double ball check valve at the exhaust valve while being seated at the inlet valve by the inlet valve spring. With the exhaust valve open, there is no air pressure in the independent application port no.
Main reservoir air is supplied through port 30 in the pipe bracket and a strainer to the spring chamber of the inlet valve where it is blanked. Vacuum pressure in the vacuum brake pipe is supplied through port No. Vacuum reservoir pressure coming from the control valve is supplied through port No.
Application When the brake valve handle is moved in to the application zone, the regulating cam dog 3 on the brake valve handle shaft 24 forces the inlet valve assembly towards the regulating valve diaphragm assembly and causes the double ball check valve to seat at the Main reservoir air is also ported through a choke passage to the face of the regulating valve diaphragm 9.
When the pressure on the face of the regulating valve diaphragm 9 overcomes the force exerted by the regulating valve spring 12, the regulating valve diaphragm assembly will move down word.
This will allow the inlet valve spring to move the double ball check assembly to the inlet valve seat, thus the brake valve will assume a lap position. Release after application When the independent brake valve handle is moved toward release position, the regulating cam dog 3 allows to move the inlet valve assembly up word, carrying the double ball check valve assembly with it, thus unseating the exhaust port while inlet valve remaining seated at the inlet valve seat.
A graduated release of brake cylinder pressure will be there, in proportion to the movement of the brake valve handle. At the same time, pressure will be released from top of the diaphragm.
When the forces across the regulating valve diaphragm 9 have equalized, the double ball check valve assembly will be seated at both the inlet and exhaust valve seats, and thus the independent brake valve will again assume a lap position. When the independent brake valve handle is placed in the quick release position, the release valve cam 19 positions the release spool valve 17 to connect vacuum control reservoir port 7 to vacuum brake pipe port 1.
Since the automatic brake application is in effect on the train, the vacuum pressure in the vacuum control reservoir will be greater than that of vacuum brake pipe, thus the vacuum control reservoir will be Permitted to equalize with the vacuum brake pipe. This will cause the proportionate brake valve to assume a release position and subsequently cause the release of the brake cylinder pressure on the locomotive.
The equalizing of the vacuum control reservoir and vacuum brake pipe will have no effect on the VA1—B control valve, thus the vacuum train brakes will remain applied. F-1 Selector Valve The F-1 Selector Valve performs the function of commanding the brake equipment on the locomotive to lead or trail position of the adjacent locomotive and ensures operation of brakes in the trail locomotives when initiated from the lead locomotive. Objective The C2-Relay valve maintains 3.
Operation Application While supply air pressure present in port 1 and no air pressure present on control diaphragm 36, both supply valve 6 and exhaust valve 23 will be seated by the respective springs. Assume that air pressure is admitted to the control port 2 of the valve. This pressure will be delivered to the upper side of diaphragm 36 causing it to move downward, carrying diaphragm stem 20 with it.
During this movement, the diaphragm stem will contact the differential type supply valve 6 and unseat it by compressing supply valve spring 5. Supply air from port 1 will then flow past the unseated valve to the delivery port 3 where it is piped to the brake cylinders. Supply air also flows through a choke in the exhaust valve to the underside of the control diaphragm When the pressure under the diaphragm is substantially equal to the control pressure on top of the diaphragm, the diaphragm assembly The relay valve will maintain this delivery pressure against leakage.
In the case of a reduction in delivery pressure, the high pressure on the upper side of diaphragm 36 will cause movement downward, repeating the application cycle and restoring the delivery pressure to the desired valve. Release When the control pressure to the valve is reduced, the high pressure on the underside of diaphragm 36 will cause it to move upward, carrying stem 20 with it.
During this movement, the shoulder on the diaphragm stem will contact differential type exhaust valve 23 and unseat it by compression of spring Air from the delivery port will then flow past unseated exhaust valve 23 to atmosphere, reducing the pressure in the brake cylinders. When the pressure has been reduced to balance the pressure in the diaphragm, the diaphragm assembly will move back to its initial position and exhaust valve 23 will seal, aided by spring 27, thus cutting off the flow of brake cylinder air to exhaust.
If the control pressure is completely removed from diaphragm 36, the valve will completely exhaust the delivery pressure to the brake cylinders. The MU- 2B valve is a two-position valve with a pipe bracket.
It is used in multiple unit service. The MU-2B valve pilots the F-1 selector valve. It is a device that enables equipment of one locomotive to be controlled by equipment of another. It also controls the movement of the VA1 release valve. In trail unit brake application valves are isolated through this valve.
Construction MU2B Valve has two positions, which works as a spool valve. It has number of port connections. Port 13 and port 3 are connected as a means of providing the passage to charge the brake pipe from the automatic brake valve. Port 30 connected to the F1 selector valve provides the connection for a supply of MR air that positions the F1 selector valve when the locomotive is used as a trailing unit.
Ports 2, 3, and 20 are blanked at the MU-2B valve. Port 53 is connected to exhaust at the MU- 2B valve. Main reservoir piped to port 63 is connected to port 30, which in turn, positions the F-1 selector valve of trail position operation. At the F- 1 selector valve, brake cylinder equalizing pipe air, port 14, is connected to ports 16 and 20, both of which are connected through a double check valve and thus to the control port of the relay valve.
This provides a passage for air emanating from the lead unit during a brake application. NOTE: In our experience, there are wide variations in airbrake systems. Some railroads ordered custom versions, the systems sometimes changed during production, and field changes were made during locomotives' lifetimes. The information here is for guidance only and should not be considered as gospel. Unfortunately, the idea was impractical.
The amount of time involved is just impossible for me to invest. If you are looking for this info, I suggest you start searching for the books on ebay , which is where I located almost all of them.
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