Hang electrical cable with plug down to prevent moisture from entering it. CDL Combination Practice Test 1 from www.cris, Fundamentals of Engineering Economic Analysis, David Besanko, Mark Shanley, Scott Schaefer. What is the function of an inversion brake valve? These valves allow the trailer brakes to be applied more quickly than would otherwise be possible. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. This type of jackknife is often called a "trailer jackknife." I think the food is above average with nice vibes. You also have the option to opt-out of these cookies. Regardless of the situation or who I happen to be dealing with I get consistently great service and response from Troy Valve. The trailer hand valve should be used only to test the trailer brakes. 1. you should use the parking brake. 2. of the danger of making the trailer skid. Glad hands are coupling devices used to connect the service and emergency air lines from the truck or tractor to the trailer. Terms | You must check that all shut-off valves are in the open position except the ones at the back of the last trailer, which must be closed. Determine the magnitude and the direction that the current in the upper coil has to have to keep it levitated at the distance 2.00mm2.00 \mathrm{~mm}2.00mm above the lower coil. Spence, Nov 11, 2019 #1 + Quote Reply. The emergency brake system uses parts of the service and parking brake systems to stop the vehicle in the event of a brake system failure. The emergency brakes come on whenever air pressure in the emergency line is lost. All they are is a service brake for the trailer. AIR BRAKES:Air brakes are used in trucks, buses, trailers and semi-trailers. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators . Thank you very much. 6.2.1 - Trailer Hand Valve. These cookies track visitors across websites and collect information to provide customized ads. The trailer hand valve is used to apply the trailer service brakes independent of the towing vehicles brakes. The trailer hand valve (also referred to as the trolley valve or Johnson bar) is a mechanism that works the trailer brakes. This is the preferred type of braking system for these vehicles for several reasons. When I apply the trolley valve it locks all my brakes tractor and trailer. The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. Copyright 2023 OpenTable, Inc. 1 Montgomery St Ste 700, San Francisco CA 94104 - All rights reserved. They provide the air pressure used to operate trailer brakes. You may not notice a major leak in the service line until you try to put the brakes on. 3 What is the purpose of an inversion valve? 3. loaded to full capacity. The function of this valve is to maintain the spring in the brake actuator compressed even though a system failure be sensed and to vent the air from the rear chamber of the brake actuator in an inverse ratio to the air at service pressure supplied to the service brake chamber by the operator through the conventional treadle valve. The trailer hand valve should be used only to test the trailer brakes. Second time here, great good, excellent service, enjoyed it just as much as the first time! 3. The trailer hand valve (also called the trolley valve or Johnson bar) works the trailer brakes. If your vehicle gets stuck on a railroad track, you should We also have areas to host smaller more intimite groups as well with private bar areas and seating. In order for you to receive the best possible offers, please make sure your answers above are accurate prior to submitting. These are air brakes that use compressed air to pressure the brakes and slow down the wheels. Unfortunately, we just cannot give a good rating. Are hydraulic brakes better than mechanical? 1. glad hands Before backing the tractor under the trailer. You should not use the trailer hand valve while driving because 3. Explanation The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. The automatic types are available with electric heating devices. They are: (1) keep the cargo as close to the ground as possible; and (2): The fifth wheel locking lever is not locked after the jaws close around the kingpin; this means: When backing your tractor under a trailer, you should expect: CORRECT ANSWER: It should be used only to test the brakes. of the danger of making the trailer skid. 1. the tractor protection valve control (trailer air supply control) will pop out or go from "normal" to "emergency." The control valve allows you to open and shut the tractor protection valve. In a hydraulic brake system, when the brake pedal is pressed, a pushrod exerts force on the piston(s) in the master cylinder, causing fluid from the brake fluid reservoir to flow into a pressure chamber through a compensating port. 39) is added so that you can apply the trailers brakes independent of the tractor. Which of the following service application valves can be referred to as a trolley valve? Some vehicles have dead end or dummy couplers to which the hoses may be attached when they are not in use. The people at Troy Valve always treat you as though you are their best customer. A. supersonic motion. Information related to the topic What is a trolly brake? 3. do it quickly to ensure that the kingpin is locked into the fifth wheel. Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. The trailer hand valve (also referred to as the trolley valve or Johnson bar) is a mechanism that works the trailer brakes. 1 Year trolley valve or johnson bar: tramvay valfi veya johnson bar: trolley valve or johnson bar terimi iin benzer kelimeler ve anlamlar: andrew johnson: andrew johnson: dubin johnson syndrome: dubin johnson sendromu: johnson: johnson: johnson city: johnson city: johnson grass: johnson imen: johnson, andrew: johnson, andrew: johnson, james . Clean the couplers and rubber seals before a connection is made. Emergency braking systems are required on all semi-trailers by CFR 49 393.43, as it states "Every motor vehicle, if used to tow a trailer equipped with brakes, shall be equipped with a means for providing that in the case of a breakaway of the trailer, the service brakes on the towing vehicle will be capable of stopping the towing vehicle. The type of valve "spits" out water and air each time the governor cycles. If it goes low enough, the trailer emergency brakes will come on. Give the location of the crossing using all identifiable landmarks, especially the DOT number, if posted. However, in the rare case that there is a problem the . The trailer hand valve should be used only to test the trailer brakes. Press in the red button labeled Trailer if a trailer is attached. Staff was very friendly, especially Tony. It's known as a trailer brake up here. Required fields are marked *. The trolley valve should only be used when testing the tailor brakes, and should never be used while driving. 3. the brake handle is too hard to reach. Impractical Jokers Q Hits the Brakes (Punishment) | truTV, What Is A Trolly Brake? Use the dummy couplers when the air lines are not connected to a trailer. A brake is contained within each rear wheel. What is the Johnny bar used for? 2. get away from your vehicle and call 911 or the posted emergency number. Using it while the vehicle is being driven could cause a skid. Loss of air pressure in the emergency line causes the trailer emergency brakes to come on. I give my express consent authorizing TruckersReport and its. Date inspected: Jan. 4. Depending on how hard you press the foot brake or hand valve, the pressure in the service line will similarly change. Every month 400 people find a job with the help of TruckersReport. You should not use the trailer hand brake to straighten out a jack You just studied 25 terms! If your going, Why should you not use the trailer hand brake to straighten out. The tractor protection valve keeps air in the tractor or truck brake system should the trailer break away or develop a bad leak. Total violations: 2. 1-5 Months Which of the following components sets the system cut-in and cut-out pressures? Each tank has a drain valve on it and you should drain each tank every day. EXPLANATION: The trailer hand valve, also called the trolley valve or Johnson bar, works the trailer brakes. Active braking control is possible based on a precise air pressure regulation in a dual-circuit brake system. Never heard it called a johnson bar either! Testing the trailer brakes after hooking up to a trailer. This cookie is set by GDPR Cookie Consent plugin. The emergency line (also called the supply line) has two purposes. Best 16 Answer, What Word Rhymes With Fire? The foot brake sends air to all of the brakes on the vehicle including the trailers. Login to License eXpress | Office Locations | Forms, Access to DOL Services | Privacy | Conditions of Use | Copyright 2023. 6-11 Months Slack adjusters are mechanical links between the brake-chamber push rod and the camshaft on cam type brakes. Movement of the handle disengages each brake. If the air supply in the trailer air tank has leaked away there will be no emergency brakes, and the trailer wheels will turn freely. Sat 10:00 am12:00 am When the tank pressure falls to the "cut-in" pressure (no lower than 85 psi or 590 kPa), the governor allows the compressor to start pumping again.Air Dryer:Today, most vehicles that use air brakes are equipped with an air dryer. First time we sat on the Party Bar side. Do not use it in driving because of the danger of making the trailer skid. These cookies ensure basic functionalities and security features of the website, anonymously. During uncoupling, you should disconnect the electrical cable and Commercial Photography: How To Get The Right Shots And Be Successful, Nikon Coolpix P510 Review: Helps You Take Cool Snaps, 15 Tips, Tricks and Shortcuts for your Android Marshmallow, Technological Advancements: How Technology Has Changed Our Lives (In A Bad Way), 15 Tips, Tricks and Shortcuts for your Android Lollipop, Awe-Inspiring Android Apps Fabulous Five, IM Graphics Plugin Review: You Dont Need A Graphic Designer, 20 Best free fitness apps for Android devices. If for any reason you get stuck on the tracks, get out of the vehicle and away from the tracks. Will continue to go back. One of the most common types of tractor trailer crashes is called a jackknife. Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful. The trailer hand valve (also called the trolley valve or Johnson bar) works the trailer brakes. The friction between the shoe lining and the drum slows the wheel. Required fields are marked *. https://www.edrivermanuals.com/georgia/commercial/combination-vehicle-air-brakes/, https://talk.newagtalk.com/forums/thread-view.asp?tid=328042&DisplayType=nested, https://www.wonkeedonkeetools.co.uk/bars/types-of-large-crowbar-pinch-point-bar, https://en.wikipedia.org/wiki/Johnson_bar, https://en.wikipedia.org/wiki/Johnson_Bar_(locomotive), https://www.mylargescale.com/threads/why-is-it-called-johnson-bar.26378/, https://www.dmv-written-test.com/question/cdl/what-is-the-johnson-bar_YWXb0dPQ.html, https://en.wikipedia.org/wiki/Johnson_bar_(vehicle), https://mappcaster.com/collections/pry-bars, https://www.dmv-written-test.com/question/cdl/when-should-the-trailer-hand-valve-be-used_Vr0J6Zyd.html, https://provia-auto.com/product-category/conventional-brake-control/hand-brake-valve/, https://www.dt-spareparts.com/en/products/product-portraits/product-portraits-detail/portrait/trailer-control-valve/, https://www.true-temper.com/tool/lawn-garden-tools/1160300-72-in-pencil-point-san-angelo-bar/, https://knottbrake.com/how-do-tractor-trailer-brakes-work/, https://www.ontario.ca/document/official-ministry-transportation-mto-drivers-handbook/trailer-brake-subsystem, https://mcqfinder.com/objective-questions/iti/mechanic-diesel/mechanic-diesel-set-1/mechanic-diesel-set-1-hydraulics-and-pneumatics/9, https://encyclopedia2.thefreedictionary.com/brake+control+valve, https://quizlet.com/146795835/subsection-62-test-your-knowledge-flash-cards/, https://www.sciencedirect.com/topics/engineering/hand-valve. The pressure in the service line tells how much pressure the relay valves should send to the trailer brakes. What is the red button in a semi truck? By gradually releasing the air from the connected Tristop or spring brake actuators the hand brake valve enables a controlled deceleration of the vehicle. Truckers: what do you use Johnny Bar for? Ive been in this business for over 31 years and without question Troy Valve is one of the Manufacturers I can always count on. The trolley valve, or trailer hand valve or Johnson bar, operates the trailer brakes on a combination vehicle. It should be used only to test the brakes. Do not use it in driving because of the danger of making the trailer skid. Related searches to What is a trolly brake? Images related to the topicImpractical Jokers Q Hits the Brakes (Punishment) | truTV. EXPLANATION: CORRECT ANSWER: It does not store any personal data. If you disable this cookie, we will not be able to save your preferences. If you use the trailer hand brake while driving, you can cause the tailor to skid. CORRECT ANSWER: When air tank pressure rises to the "cut-out" level (no higher than 135 pounds per square inch, or psi or 900 kPa), the governor stops the compressor from pumping air. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. EXPLANATION: You push it in to supply the trailer with air, and pull it out to shut the air off and put on the trailer emergency brakes. Why should you not use the trailer hand valve while driving? The compressor may be air cooled or may be cooled by the engine cooling system. Never use the hand valve for parking because all the air might leak out unlocking the brakes (in trailers that dont have spring brakes). Do not use it in driving because . For the best experience on our site, be sure to turn on Javascript in your browser. D. the Doppler effect. 10 Most Correct Answers, Professional track Udacity digital marketing project 2 digital marketing, name the coupling device at the end of each air hose. There are two kinds of service brakes, or the brakes that stop your vehicle while driving: In vehicles, there are two types of Breaks, Hydraulic Brake and Air Brake. There is ice and snow, to prevent skidding. Emergency Air Line. The trailer hand valve (also called the trolley valve or Johnson bar) works the trailer brakes. Fri 11:00 am12:00 am In addition to the professional, knowledgeable staff, the products manufactured by Troy Valve are always of the highest quality. In addition to the professional, knowledgeable staff, the products manufactured by Troy Valve are always of the highest quality. They run between each vehicle (tractor to trailer, trailer to dolly, dolly to second trailer, etc.). I Need CDL Training However, the brakes will still apply. This means that every time you visit this website you will need to enable or disable cookies again. What should you do to stop a trailer skid? How does the spring actuated brake system work? At present, we do not have menu information for this restaurant. This website uses cookies to improve your experience while you navigate through the website. Please see their website or wait to visit the restaurant to learn more. Thanks. 3. coil it to keep it out of the way. Your email address will not be published. 2023 Penn-Troy Manufacturing, Inc. All rights reserved. Gladhands are designed to allow the driver to disconnect without a mechanic or tools. Severs were going by our table and no server ever stopped at our table. What is the purpose of an inversion valve? 5+ Years, Please select ALL of your current, valid drivers licenses. You can find out more about which cookies we are using or switch them off in settings. The service line is connected to relay valves. Air will not be available to release the trailer spring brakes (parking brakes). In most cases, the trailer couplers are colour-coded during manufacturing red for the supply line and blue for the service line (See Diagram 5-2). C. the law of superposition. CORRECT ANSWER: For example, the water can freeze in cold weather and cause brake failure. Made of forged, hardened steel, it has a curved end made from carbon steel. Thanks for the help and great craftsmanship on the project! Went back the next day! Do not use it in driving because of the danger of making the trailer skid. The Key Difference between Hydraulic Brake and Air Brake is that. Explanation The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. "Air brake systems are three braking systems combined: The air brake system: An air brake system uses air as a way to transmit pressure from the driver's control to the service brake. When should you use the hand valve to park a combination vehicle? Will parking brakes apply automatically in all braking systems? CORRECT ANSWER: The tabulated data were collected for this reaction: 2NO2(g)+F2(g)2NO2F(g)2 \mathrm{NO}_{2}(g)+\mathrm{F}_{2}(g) \longrightarrow 2 \mathrm{NO}_{2} \mathrm{F}(g)2NO2(g)+F2(g)2NO2F(g), [NO2][F2](M)InitialRate(M/s)0.1000.1000.0260.2000.1000.0510.2000.2000.1030.4000.4000.411\begin{matrix} \ {[NO_2]} & \ {[F_2] (M)} & \text{Initial Rate (M/s)}\\ \text{0.100} & \text{0.100} & \text{0.026}\\ \text{0.200} & \text{0.100} & \text{0.051}\\ \text{0.200} & \text{0.200} & \text{0.103}\\ \text{0.400} & \text{0.400} & \text{0.411}\\ \end{matrix} A Johnson bar is a hand lever with several distinct positions and a positive latch to hold the lever in the selected position. Hence the term originally was jouncin bar which over the years morphed into Johnson bar. This will release the trailer brakes. When backing under the trailer you should? This valve normally has a red, eight-sided knob that the driver pushes in to open and supply air to the trailer and pulls out to close or when no trailer is attached. A cable connected between the handle and brake linkage disengages the brake shoe, allowing each wheel to freely rotate. JavaScript seems to be disabled in your browser. Every month 400 people find a job with the help of TruckersReport. Movement of the handle disengages each brake. When an engineer changed the reverse lever position to notch up or down he had to hang on for dear life! Press the yellow button labeled Parking while your foot is on the brake pedal. Sun 10:00 am10:00 pm. This cookie is set by GDPR Cookie Consent plugin. The trailer hand valve is used only to test the trailer brakes. Hydraulic brake is also known as Oil break. Lastly, Ill say that delivery commitments are almost always met or exceeded. The water and oil are automatically expelled from a spit valve. trailer hand valve should be used only to test the trailer brakes. A relay valve is an air-operated valve typically used in air brake systems to remotely control the brakes at the rear of a heavy truck or semi-trailer in a tractor-trailer combination. Dueling Parallel Restaurants with 4 Bars, 2 complete full kitchens and 300 Seats inside and out on our mirroring patios. What Word Rhymes With Griffin? The trailer hand valve should be used only to test the trailer brakes. Do not use it in driving because of the danger of making the trailer skid." and this is from another section under Prevent Trailer Skids If your tanks have automatic drains, they will keep most moisture out. What is a trolley valve? Second, the emergency line controls the emergency brakes on combination vehicles. A tractor / trailer typically has two gladhands one for service brakes and another for emergency brakes. Analytical cookies are used to understand how visitors interact with the website. At the very bottom of the instrument panel is a red button, its next to the steering column and is wired all the way down to the upper part of the transmission and rear drive shaft. I Need CDL Training If the information on this translated website is unclear, please contact us at 360.902.3900 for help in your language of choice. Observed ice machine interior deflector with an accumulation of black debris . Save my name, email, and website in this browser for the next time I comment. It should only be used to test the brakes. Pull gently against them in a low gear to make sure the brakes work. Therefore, it is very important for safety that you use wheel chocks when you park trailers without spring brakes. Change your disability or medical designation, Renew your driver license while out of state, Replace your license or instruction permit, Replace your driver license while out of state, Replace your enhanced driver license (EDL), Check the status of a motorcycle endorsement, Medical certificates and self-certification, Register to be a training provider or instructor, Check the status of a driver license or ID card, Occupational/Restricted Driver License (ORL). 3. make sure the ground is solid and can support the weight of the trailer. The trailer is at the right height when: How should you test the tractor trailer connection for security? The people at Troy Valve always treat you as though you are their best customer. LMAO Man i need that slang dictionary for truckers. Cookie Policy | In order for you to receive the best possible offers, please make sure your answers above are accurate prior to submitting. The trailer hand valve should only be used when: A INCORRECT The correct answer is: Testing the trailer brakes after hooking up to a trailer. The control valve allows you to open and shut the tractor protection valve. EXPLANATION: The governor controls when the air compressor will pump air into the air storage tanks. Your email address will not be published. 4 Years 1. radio in for assistance. 2. always use the lowest reverse gear. CORRECT ANSWER: EXPLANATION: In addition, the use of an air brake system allows for the incorporation of an emergency braking system that utilizes parts of the service brake and parking brake systems. 5+ Years, Please select ALL of your current, valid drivers licenses. What is trolley brake on tractor trailer? Why do you need a proportioning valve for panic braking? First, the use of air allows multiple vehicle units to be coupled so that all units have braking capability and so that all of those units' brakes may be controlled from the cab. 2. hang it with the plug down. The foot brake sends air to all of the brakes on the vehicle (including the trailer[s]). 2. always use the lowest reverse gear. The trailer hand valve should be used only to test the trailer brakes. 2. overloaded. Using it while a vehicle is in motion could cause a skid. 43145 Broadlands Center Plaza, Ashburn, VA 20148, Broadlands Boulevard & Claiborne Parkway, Bar/Lounge, Counter Seating, Entertainment, Happy Hour, Late Night, Non-Smoking, Patio/Outdoor Dining, Reviews can only be made by diners who have eaten at this restaurant. explanation The trailer hand valve (also called the "trolley valve" or "Johnson bar") works the trailer brakes. johnson bar or trolley valve are trailer brake handles usually on the right side of the steering collum or up on the dash. The emergency position is used to shut the air off and put on the trailer emergency brakes. Subject: Truckers: what do you use Johnny Bar for? The owners and the chef were born and raised in Puerto Rico. But you should still open the drains to make sure. 5 Which shutoff valves should be open and closed? The service line (also called the control line or signal line) carries air, which is controlled by the foot brake or the trailer hand brake. The trailer hand valve (also called the trolley valve or Johnson bar) works the trailer brakes. Boring, eh? It should be used only to test the brakes. Trailer will be lifted slightly when the tractor backs under it. Before you start to uncouple, you must Images related to the topicAirline Trolley Brake Repair. Using it while the vehicle is being driven could cause a skid. The trailer hand valve (also called the trolley valve or Johnson bar) works the trailer brakes. This business is veteran owned. CORRECT ANSWER: Privacy | The trailer hand valve should be used only to test the trailer brakes. The trolley valve should only be used when testing the tailor brakes, and should never be used while driving. Northern Virginia's Only Premier Wine & Whiskey Bar featuring over 300+ Bourbons & Whiskies, 60+ Wines by the Glass and over 80 Craft Beer Selections paired with Chef Prepared Cuisine. A valve in the aircraft brake system that controls the amount of hydraulic pressure applied to wheel brakes. 8 Why do you need a proportioning valve for panic braking? There is much less danger of causing a skid or jackknife when using just the foot brake. These parts are described below. The trolley valve, or trailer hand valve or Johnson bar, Explanation The trailer hand valve (also referred to as the trolley valve or Johnson bar) is, The trailer hand valve (also called the trolley valve or Johnson bar), Explanation The trailer hand valve, also called the trolley valve or Johnson bar, is, At the very bottom of the instrument panel is a red button, its, Can Cats Have Dog Greenies? Trucking Jobs in 30 seconds. The burke bar has been lauded as one of the most useful tools for demolition. While driving, your foot brake will send . Do not use it in driving because of the danger of making the trailer skid. Back tractor slowly under trailer to avoid hitting the kingpin too hard, and stop when the kingpin is locked into the fifth wheel. Which answer is correct for the air valves when testing the trailer spring / parking brakes only? Using it while a vehicle is in motion could cause a skid. This is bad for the air brake system. It is very important to keep the air supply clean. The valve will pop out (thus closing the tractor protection valve) when the air pressure drops into the range of 20 to 45 psi. 10 Most Correct Answers, What Word Rhymes With Goddess? This will prevent water and dirt from getting into the coupler and the air lines. Date inspected: Dec. 28. It should be used only to test the brakes. What are the yellow and red button in a truck? 1 How does an air brake inversion valve work? Glad hands are coupling devices used to connect the service and emergency air-lines from the truck or tractor to the trailer. Do not use it in driving because of the danger of making the trailer skid. This is more likely to happen when the trailer is empty or lightly loaded. It should be used only to test the brakes. EXPLANATION: Parallel is truly "Un-Paralleled" Cheers! instructions to enable JavaScript in your web browser. For emergency stops, the stab braking method entails fully applying the brakes until they lock up. These trailers have no parking brake. The trailer hand valve, also called the trolley valve or Johnson bar, works the trailer brakes. Always use the parking brakes when parking. CORRECT ANSWER: Each trailer and converter dolly has one or more air tanks. Rear drum brakes are hydraulic over mechanical in design. Large combination vehicles take longer to stop when they are empty than when they are fully loaded. A turn of the glad hand attached to the hose will join and lock the couplers. EXPLANATION: You will find the answer right below. Service Brake: off; Parking Brake: off; Trailer air supply: in / open; Trolley: applied. The trolley valve, or trailer hand valve or Johnson bar, operates the trailer brakes on a combination vehicle. (Emergency brakes are covered later.). Using it while the vehicle is being driven could cause a skid. Truck drivers call the lever control for air-operated trailer brakes Johnson bars. Which of the following air brake system components functions as a lever? As part of your vehicle inspection test, if your vehicle is equipped with air brakes and has a trailer, you will inspect the air connections between the truck or tractor and the trailer. If the air pressure in the system falls below approximately 70 psi (483 kPa), the spring brakes may begin to drag and if it falls between 20-45 psi (138-310 kPa), will fully apply. 1. empty. EXPLANATION: If the spring brakes dont release when you push the trailer air supply control, check the air line connections. This is not the first time this happened. Jackknife crash: when a semi-truck trailer skids towards the truck cab at a 90-degree angle. When you'd start a train, you'd put the johnson bar "all the way in the corner" and this would allow steam to be admitted to the cyninders for about 80% of the stroke of the piston. Job Listing Rules, I have a 2019 567 Pete. There are two types: TRAILER PARTS SUPERSTORE931 S. Chapel St. Newark, Delaware 19713. Strictly Necessary Cookie should be enabled at all times so that we can save your preferences for cookie settings. works like the foot brake but only for just the trailer and isn't meant for use while driving down the road. Use lowest reverse gear. If you use the trailer hand brake while driving, you can cause the tailor to skid.Explanation The trailer hand valve (also referred to as the trolley valve or Johnson bar) is a mechanism that works the trailer brakes. Never use the hand valve for parking because all the air might leak out unlocking the brakes (in trailers that dont have spring brakes). The product of these two values is expressed as the AL factor. This factor, when multiplied by 60 psi air pressure, is the industry standard for braking calculations.