ID: nht74-2.15

DATE: 03/20/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Kelsey-Hayes Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your February 1, 1974, request for interpretation of the language "maximum temperature of 500 +/- 50 degrees F" appearing in S6.1.8.1 of Standard No. 121, Air brake systems, 49 CFR 571.121.

The language is intended to specify a temperature range within which to conduct the burnishing procedure in the event brake applications cause the hottest brake on a vehicle to reach 500 degrees F. The word "maximum" is inappropriate and will be deleted in an upcoming notice responding to petitions that raised the same point.

Yours truly,

ATTACH.

KELSEY-HAYES COMPANY

February 1, 1974

National Highway Traffic Safety Administration, U. S. Department of Transportation,

Attention: Lawrence Schneider -- Chief Counsel

RE: Request for Interpretation FMVSS-121; Air Brake Systems Docket 73-13; Notice 3 @ 6.1.8.1 Brake Burnish Procedure

Gentlemen:

We would appreciate an interpretation of the following sentence which appears in the above cited section of Standard 121:

"If during any of the brake applications specified in Table IV, the hottest brake reaches 500 degrees F, make the remainder of the 500 applications from that speed except that a higher or lower speed shall be used as necessary to maintain a maximum temperature of 500 degrees F +/- 50 degrees F."

We believe the meaning of this sentence to be that the temperature of a brake may not exceed 550 degrees F at any time during a brake application and that the speed limitations specified in Table IV may be waived to maintain the temperature below 550 degrees F only if the temperature of the hottest brake reaches 500 degrees during any stop.

We are puzzled by the words ". . . maintain a maximum of 500 degrees F +/- 50 degrees F", as the tolerance appears to be inappropriate if our interpretation is correct. Conversely, if the intent is to limit the temperature range to 500 degrees F +/- 50 degrees F once a temperature of 500 degrees F is reached, the word "maximum" is inappropriate.

A prompt reply would be very much appreciated.

Very truly yours,

John F. McCuen -- Attorney

cc: W. T. Birge; D. Renner

ID: nht74-2.16

DATE: 11/14/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Hall and Myers

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your October 23, 1974, question whether the language of S5.3.1(b) and S5.3.2(b) in Standard No. 121, Air brake systems, exempts all liftable, nonsteerable axles from the "no lockup" requirements of the standard. You specifically ask whether a liftable, nonsteerable "tag" axle and "pusher" axle would be exempt if they were both mounted on a vehicle equipped with a single nonliftable, nonsteerable axle or with tandem nonliftable, nonsteerable axles.

The sections in question permit "lockup of wheels on nonsteerable axles other than the two rearmost nonliftable, nonsteerable axles on a vehicle with more than two nonsteerable axles." This language is limited to vehicles which have more than two nonsteerable axles and therefore a liftable axle on a vehicle with only one other nonsteerable axle would not be exempt. Such combination can be found on some intercity buses.

In both of the examples you described the vehicle has more than two nonsteerable axles, and therefore the language of S5.3.1(b) and S5.3.2(b) would exempt the tag and pusher axles from the "no lockup" requirements of the standard. I would like to emphasize, however, that our language is intended to require "no lockup" performance on not less than two nonsteerable axles of any vehicle with at least two nonsteerable axles. We did not contemplate the unlikely configuration of a single fixed axle and two liftable axles which you cite as an example. If a safety problem arises with this configuration, we would consider an amendment of the standard to require "no lockup" performance of two of these axles.

Yours truly,

ATTACH.

ID: nht74-2.17

DATE: 08/12/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Walter Case

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your June 13, 1974, request for approval of your "park-lock" device under the parking brake system requirements of Standard No. 121, Air brake systems, 49 CFR @ 571.121. After a trailer's emergency air supply applies the brakes through the service brake chamber in response to a low service brake air supply, your device locks the brakes in the applied position.

The relevant provision of the standard states:

S5.6.3 Application and holding. The parking brakes shall be applied by an energy source that is not affected by loss of air pressure or brake fluid pressure in the service brake system. Once applied, the parking brakes shall be held in the applied position solely by mechanical means.

The arrangement described would not meet this requirement because the energy source to apply the brakes (the emergency air supply) would be affected by loss of air pressure in the service brake system. For example, any failure in the service brake piston diaphragm would cause a loss of air pressure that would in turn "affect" the energy source that applies the parking brake. The brake chamber housing assembly is an element which is not considered to be part of the service brake system for this requirement.

Standard No. 121 does not specify the design of brake system components. Therefore we neither approve nor disapprove the use of particular components like the "park-lock" device. It may be used in any parking brake system which meets the requirements of the standard.

I would like to point out that the standard becomes effective January 1, 1975, for trailers, and that it does not regulate air brake systems on trailers manufactured before that date.

Yours truly,

ATTACH.

June 13, 1974

Larry Schneider -- Chief Counsel National Highway Admn.

Dear Mr. Schneider:

This is being written at the suggestion of Mr. Sid Williams, made to me during a telephone conversation only a few minutes ago.

I am the inventor of a brake locking device for air brake system equipped trailers. This device which weighs barely two pounds has been pronounced by leaders of the Motor Freight industry as the greatest safety device offered the industry in thirty-five years.

Some eight or so weeks ago, B. F. Goodrich Company examined and tested this brake lock and informed us of their intention to use it on their new safety systems, these being readied for market. This followed careful examination of the requirements for complying with NVSS 121 by both B. F. Goodrich and ourselves.

Our device does not alter the regular braking system in any manner. This brake lock works in conunction with the long required and approved Reserve Emergency Valve and trailer emergency air supply system. With the improved (modulated) RE 4 Valve plus our (Park-Lock) brake holding device, safety involving trailers has been increased many fold whether on the highway, parking lot or at the loading dock.

Should the service brake air supply be broken intentionally or by accident the trailer emergency air supply would take over and bring the vehicle to a stop. In such an instance, the Park-Lock would lock the set brakes automatically when the air pressure dropped to 20 lbs.

We submit that our brake locking device meets all requirements of NVSS 121 and of particular reference to (e) paragraph of Div. 12-369-26508 which prompted B. F. Goodrich's bringing to our attention they had been informed there was some question about Park-Lock meeting one requirement. The question concerns a brake chamber diaphragm failure.

Conversations with two large Motor Freight Companies (Transcon - E.T.M.F.) answered our inquiry this way: Concerning failure or malfunction of a diaphragm was, according to their records the rarest of their problems. The only maintenance reports are that of slow leaks reported by the driver. Neither Company could recall a burst diaphragm. In the event of such leak there is a warning device in the cab calling such to the driver's attention.

Particular care was given to explain to us that should the service system fail, the trailers system would be activated by the RE 4 Valve and the vehicles would be brought to a stop, even with a leak in a diaphragm.

Should the trailer system malfunction, the tractor system, protected by the tractor protection valve, would provide the necessary braking power to bring the vehicles to a safe stop. Either way, they emphasize, adequate braking is there to bring vehicles to a stop and all that is really needed for safety is a satisfactory brake lock to fit the tried and proven system now in use.

The Park-Lock brake lock has been proven in regular service for over a year. It is small enough to hold in your hand. The device is simple of construction, has three moving parts making for little wear, or requirement of maintenance.

We will appreciate your careful examination and checking out of our claims. The same, we are confident, can be said for the industry who has hailed our safety device.

Sincerely yours, Walter Case -- PARK-LOCK, INC.

ID: nht74-2.18

DATE: 06/07/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Certain-Teed Products Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your April 5, 1974, question whether S5.6.1 or S5.6.2 of Standard No. 121, Air brake systems, requires parking brakes on all axles other than front steerable axles.

S5.6.1 requires "parking brakes on an axle other than a steerable front axle" to have certain static retardation force values. "An axle" refers to any axle other than steerable front axles and therefore S5.6.1 requires parking brakes on all axles other than steerable front axles. A tandem axle consists of two separate axles for purposes of this requirement.

S5.6.2 has no specific axle-by-axle requirements. Its performance standard may be met by any means which hold the vehicle stationary and conform to S5.6.3 and S5.6.4. It should be emphasized that this requirement cannot be met simply be equipping the vehicle with parking brakes which hold to the limit of tractive ability but permit vehicle movement.

Yours truly,

ATTACH.

CERTAIN-TEED PRODUCTS CORPORATION

April 5, 1974

Chief Council -- National Highway Traffic Safety Adm., U.S. Department of Transportation

RE: Federal Vehicle Motor Safety Standards No. 121-Air Brake System Docket No. 74-10; Notice 1

Dear Sir:

We are requesting clearification of Paragraph S. 5.6.1 and S. 5.6.2.

Is the intent of Paragraph S. 5.6.1 to require parking brakes on all axles other than a steerable front axle, and is a tandum axle from the viewpoint of this regulation considered to be made up of two (2) separate axles?

In Paragraph S. 5.6.2, is it necessary to have parking brakes on each axle of the vehicle, or would a vehicle be acceptable if parking brakes mounted on only a portion of the axle were adequate to meet the grade holding requirements.

There appears to be questions in the minds of vehicle manufacturers, who are our customers, as to whether a trailer or a truck and bus with a modulated emergency system would require parking brakes on all non-steerable axles or whether only a portion of the axle requires parking brakes. We would appreciate an early reply to this inquiry.

Yours very truly,

B. D. Sibley -- Chief Product Engineer, Brake Products

ID: nht74-2.19

DATE: 10/22/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Truck Trailer Manufacturers Assoc.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of September 4, 1974, in which you ask several questions regarding the possible manufacture of semitrailers designed to transport people. You state the semitrailers would be pulled by conventional tractors, would have air-operated bus-type side doors, a rear door for emergency exit, seats, handrails for passengers who stand, and windows that open and close. Communication between the passenger compartment and driver would be limited to a horn that the driver can blow and a blinking red light operable by either a passenger or the driver. You ask whether this type of vehicle is legal, whether it is legal to transport passengers in this fashion, and what specific requirements would be required to be built into the trailer.

We would consider the vehicles in question to be trailers under the Motor Vehicle Safety Standards, and consequently subject to the standards applicable to trailers. These standards are Standard No. 108, "Lamps, reflective devices, and associated equipment," Standard No. 106, "Brake hoses" (eff. as to trailers on September 1, 1975), and Standard No. 121, "Air brake systems" (eff. as to trailers on January 1, 1975), at this time. The trailers would, of course, have to be certified as conforming to all applicable standards, in accordance with the Certification Regulations (49 CFR Parts 567, 568).

Many States prohibit the transportation of passengers in trailers, and as a consequence NHTSA requirements for crashworthiness and occupant protection have not been made applicable to trailers. These requirements include those for restraint and seating systems, glazing materials, head restraints, and emergency exits. Whether or not State laws prohibiting the transportation of passengers in trailers would apply to semitrailers of this type would depend upon each State's interpretation of its law, and that information should be obtained from the various states. However, should it become a commonly permitted practice for persons to be transported in trailers, this agency would very likely expand its occupant protection and crashworthiness requirements through rulemaking to apply to these vehicles.

The transportation in interstate commerce of passengers for hire also falls within the regulatory authority of the Bureau of Motor Carrier Safety, in the Federal Highway Administration. We have forwarded your letter to that agency, requesting that it respond directly to you regarding the effect of regulations it administers on vehicles of this type.

Yours truly,

ATTACH.

Truck Trailer Manufacturers Association

September 4, 1974

James B. Gregory -- National Highway Traffic Safety Administration, Department of Transportation

Dear Dr. Gregory:

A member company is currently evaluating the possibility of manufacturing semitrailers which are detachable from the tractor, that are specifically designed to transport people or personnel. These trailers would be pulled over the Federal highways and would be pulled by a detachable conventional tractor. The trailers would be more or less conventional construction with the following basic specifications:

(1) The trailer would have an air operated bus type side door operated off the tractor air brake system.

(2) The trailer would have a rear door for emergency exit that could be operated from the inside.

(3) The trailer would be equipped with seats and handrails for those passengers standing up.

(4) The trailer would be equipped with windows that could be opened and closed.

(5) There would be no communication between the passenger compartment and driver compartment other than a horn that the driver can blow and a blinking red light that can be operated from either the interior of the trailer or the interior of the tractor.

Specifically, is this type of vehicle legal or is it legal to haul passengers over the highway with a detachable semitrailer of this type, and if it is legal what are the specific requirements that have to be built into the trailer?

We would appreciate receiving your thoughts on this matter.

Sincerely yours,

Burt Weller -- Engineering Manager

ID: nht74-2.2

DATE: 03/08/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Certain-Teed Products Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your January 25, 1974, question whether failure of a "common" clampband assembly on the "Camtite" emergency and parking spring brake, which would cause complete loss of air to the service brake system and failure of the emergency/parking brake portion of one unit, would be in violation of paragraph S5.7.2.2 of Standard 121.

The answer is no. S5.7.2.2 requires that failure of components common to the service and emergency braking systems shall not result in a loss of air that causes the parking brake to be inoperable. We interpret "parking brake" to mean the entire parking brake system. The failure you describe would not render the entire system inoperable, because all parking brakes other than the affected unit would remain operable.

This letter will be placed in the public file for the information of other interested persons.

Yours truly,

ATTACH.

CERTAIN-TEED PRODUCTS CORPORATION

January 25, 1974

Administrator -- National Highway Traffic Safety Administration, U. S. Department of Transportation

Re: Federal Motor Vehicle Safety Standard No. 121 - Air Brake Systems

Dear Sir:

We have been questioned by a customer for an interpretation as to the conformance of our CAMTITE emergency and parking spring brake design, as described in the attached brochure, to Paragraph S5.7.2.2., EMERGENCY BRAKING SYSTEM FAILURE, of FMVSS 121. This paragraph states:

"In the event of a failure of a valve, manifold, brake fluid housing, or brake chamber housing that is common to the service brake and emergency braking systems, loss of air shall not cause the parking brake system to be inoperable."

The service brake portion of our Camtite is "sectioned" in white and the emergency or parking spring brake portion in black on the Dimensional Drawing page of the enclosed brochure (SB-102). The clampband (Item #12 on the Parts List page) is common to both the service and emergency/parking brake portion of the unit.

We would appreciate a reply to the question: "Would failure of the "common" clampband assembly during a service brake application which could cause both loss of air and the complete "disengagement" of the service brake pressure side, as well as the total emergency/parking spring brake portion of the unit, be in violation of the intent of paragraph S5.7.2.2. of FMVSS 121?".

Very truly yours,

C. W. Mohr -- Vice President-Marketing

[Graphics omitted]

[Graphics omitted] REPLACEMENT PARTS NUMBER ITEM DESCRIPTION QTY. TYPE 24 TYPE 30 TYPE 36 1 Cylinder Assembly 1 47-31737-9 -- 47-40108-9 2 Piston Assembly 1 47-31797-9 -- 47-40093-9 3 Felt Wiper Ring 1 47-31805-9 -- -- 4 Piston Seal Ring 1 47-31799-9 -- -- 5 Seal Ring 1 36-524615 -- -- 6 Nylon Bushing 1 47-31745-9 -- -- 7 Bulkhead Seal Ring 1 47-31800-9 -- -- 8 Retaining Ring 1 47-31804-9 -- -- 9 Bulkhead 1 47-31747-9 47-31738-9 47-40095-9 10 Machine Screw 1 47-36161-9 -- -- 11 Follower 1 47-31785-9 -- -- 12 Clamp Band Assembly 1 40-31061-9 40-31062-9 40-31063-9 13 Self Tapping Screw 2 47-40012-9 -- -- 14 Diaphragm 1 40-31251-9 40-31165-9 40-31252-9 15 Return Spring 1 47-31258-9 -- -- 16 Non Pressure Plate 1 47-31364-9 47-31267-9 47-40098-9 17 Filter 1 47-31971-9 -- -- 18 Stop Washer 1 47-31974-9 -- -- 19 Snap Plug 1 47-31975-9 -- -- 20 Release Bolt 1 47-31970-9 - 47-40105-9 21 Capscrew 8 46-31656-9 -- -- 22 Spring (Light) 1 41-31920-9 -- -- Spring (Medium) 1 41-31921-9 -- -- Spring (Heavy) 1 41-31922-9 -- -- Spring (Booster) 1 47-40112-9 -- -40101 Push Rod (8.00 Proj.) 1 47-36034-9 47-31986-9 47-40102-9 Spring Locator 1 47-40191-9 -- --

NOTE: The symbol -*- indicates part is identical to part number listed in first column. Parts that differ are listed under appropriate type number. Parts shown are for complete units.

DIMENSIONAL DRAWING REFERENCES

A. AIR INLET ORIENTATION STANDARD 22 1/2 degrees +/- 3 degrees

B. CLAMP BAND ORIENTATION STANDARD 45 degrees +/- 3 degrees C. PUSH ROD PROJECTION (See back page)

D. YOKE CENTER PROJECTION (See back page)

CAMTITE

NOMINAL SPRING FORCES (OUTPUT OF COMPLETE UNIT)

[Graphics omitted]

CAMTITE

SPRING RELEASE PRESSURE NOMINAL RELEASE SPRING TYPE PRESSURE +/- 10% BOOSTER 30 LIGHT (40) 40 MEDIUM (50) 51 HEAVY (60) 62 MEDIUM PLUS 81 BOOSTER HEAVY PLUS 91 BOOSTER

NOTE: FOR EASE OF INSTALLATION ALL UNITS ARE SHIPPED IN MECHANICALLY RELEASED POSITION.

[Graphics omitted]

PUSH ROD AND YOKE SIZES

PUSH ROD PROJECTION:

Push Rod Projection is the Distance the Push Rod Extends Out from the Mounting Face of the CAMTITE Chamber. When Replacing Service Brakes with CAMTITE Chambers, the Push Rod Projection Length will Remain the Same. CAMTITE Standard Projection Length is 1-3/4" TYPE OF PROJECTIONS PART CHAMBER AVAILABLE NUMBER 24 1-3/4" (Std.) 47-31512-9 24 8" 47-36034-9 30 1-3/4" (Std.) 47-31511-9 30 8" 47-31986-9 36 1-3/4" (Std.) 47-40101-9 36 8" 47-40102-9

Other projections available upon special request.

(Illegible Word) ASSEMBLIES:

CAMTITE Yoke Assemblies are Available and may be Ordered as Complete Assemblies Containing Yoke, Yoke Pin, and Cotter Pin, or the Assembly Components May be Ordered Separately.

For Special Applications Requiring the Yoke to be Applied at Factory the Dimension from the Mounting Surface of the CAMTITE Chamber to Center Line of the Yoke Pin Should Be Specified.

[Graphics omitted] ASSEMBLY DIMENSIONS PART NUMBER 1 2 3 4 D 1-3/ 40360479 1-27/32" 1/2" 9/16" 8" 3" 1-3/ 40360489 1-3/4" 5/8" 9/16" 8" 3" 13/ 1-3/ 40360499 1-7/8" 3/4" 16" 8" 3"

**Figures for "O" Represent Standard Dimension Using Push Rods with 1-5/4" Projection.

ID: nht74-2.20

DATE: 05/13/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: American Trailers, Inc.

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your April 12, 1974, question whether a permanently attached steerable axle on a trailer is required (1) to meet the S5.3.2 stopping distance requirement with no uncontrolled lockup of any wheel above 10 mi/h, and (2) to meet the parking brake requirements for trailer converter dollies or for all other vehicles.

The answer to your first question is yes. The steerable axle(s) of any trailer must meet the stopping distance requirements of S5.3.2 with no uncontrolled lockup of wheels above 10 mi/h.

In answer to your second question, the permanently attached steerable axle you describe is not a separate vehicle which would qualify as a trailer converter dolly. Therefore the axle is simply part of a trailer which must meet the parking brake requirements of either S5.6.1 or S5.6.2. Neither of these options specifies that there be parking brakes on steerable axles, although in satisfaction of S5.6.2 (grade holding), the manufacturer could utilize parking brakes on the steerable axle.

Yours truly,

ATTACH.

April 12, 1974

James B. Gregory -- Administrator, National Highway Traffic Safety Administration

Dear Sir:

We manufacture a complete line of semi-trailers. Among these is a doubles grain trailer setup. In this doubles grain setup the lead trailer is a 24 foot, single axle semi-trailer which connects to the truck-tractor by means of a standard kingpin. The second trailer is a two axle, four wheel type of trailer, 21 foot long, which is connected to the lead trailer by means of a pintle hook-lunette eye attachment. The front axle on the second trailer is part of a dolly, which is steerable, and is permanently attached to the trailer by means of a bolted 360 degrees turntable.

Our question is one of interpretation. Is the front axle dolly a "converter dolly" in the sense that it would be exempt from having "antilock" and spring brakes as outlined in S5.8 of standard 121? Or is it to be classed so that it will require anti-lock and spring brakes? Your expeditious answer as to interpretation is appreciated.

Sincerely, Al Zajic -- Project Engineer, AMERICAN TRAILERS, INC.

Encl:

(Graphics omitted)

LEAD TRAILER

SECOND TRAILER

PERMANENT 360 DEGREES TURNTABLE

ID: nht74-2.21

DATE: 08/12/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: B. F. Goodrich Aerospace and Defense Products

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your June 4 and June 20, 1974, letters asking if a parking brake system which locks mechanically after the brake is applied by any emergency air supply acting through the service air brake chamber would comply with Standard No. 121, Air brake systems. The parking brake provisions require in part:

S5.6.3 Application and holding. The parking brake shall be applied by an energy source that is not affected by loss of air pressure or brake fluid pressure in the service brake system. Once applied, the parking brakes shall be held in the applied position solely by mechanical means.

The arrangement described would not meet this requirement because the energy source to apply the brakes (the emergency air supply) would be affected by loss of air pressure in the service brake system. For example, any failure in the service brake piston diaphragm would cause a loss of air pressure that would in turn "affect" the energy source that applies the parking brakes. The brake chamber housing assembly is an element which is not considered to be part of the service brake system for this requirement.

I would like to point out that the provisions of Standard No. 121 do not apply to trailers manufactured before January 1, 1975.

Your truly,

ATTACH.

June 4, 1974

CHIEF COUNCIL -- U. S. Department of Transportation National Highway Traffic Safety Administration

Dear Sirs:

The following inquiry is submitted to you with regards to telephone conversations with Mr. S. F. Williams on Friday afternoon, May 31, 1974, and Monday morning June 3, 1974.

Will MVSS 121 permit actuation of a mechanically locking parking and/or emergency brake, using air that is applied to the service brake diaphragm?

The air is supplied, of course, from an isolated emergency source.

Yours truly, B. F. GOODRICH ENGINEERED SYSTEMS COMPANY A Division of The B. F. Goodrich Company;

A. J. Burt -- Sales Engineer

CC: S. F. Williams, D.O.T.; R. D. Buehler, B. F. Goodrich, Washington D. C.; C. R. Collins, B. F. Goodrich, Springfield, Virginia

B. F. Goodrich Aerospace and Defense Products

June 20, 1974

S. F. WILLIAMS -- U. S. Department of Transportation, National Highway Traffic Safety Administration

Dear Sid:

Relative to our phone conversation this afternoon, attached is a copy of all the technical information we have concerning the Park-Lock brake.

The Park-Lock people that we talked to in February of this year were Mr. Joe D'Angelo and Mr. Paul Mantle.

I should note that my inquiry to the Chief Council dated June 4, 1974 and copied to you, is meant to be interpreted as a generalized question concerning the use of a service brake diaphragm. The "mechanically locking parking and/or emergency brake" was not meant to refer specifically to the "Park Lock" device, but any general device which would require actuation by emergency air applied to a service brake diaphragm, and then mechanically locking once the actuation stroke is completed.

Yours truly,

A. J. Burt -- Sales Engineer, Highway Products

CC: R. D. Buehler -- B. F. Goodrich, Washington, D.C.; C. R. Collins -- B. F. Goodrich, Springfield, Virginia

Park-Lock

(Illegible Word) PARK LOCK?

Park Lock is an Automatic Brake Holding Device that holds your brakes, once applied . . . A New Friend to the Trucks.

WHAT DOES PARK LOCK DO?

Park Lock prevents trailer roll offs; climinates wheel chocking; prevents release of brakes when service system air pressure is below safe operating level.

HOW IS PARK LOCK APPLIED?

In emergency conditions, such as loss of air, the Relay Emergency Valve applies your brakes. . . As the air leaks off, Park Lock gently applies, automatically, and holds your brakes by mechanical means.

HOW IS PARK LOCK RELEASED?

There are two ways to release Park Lock.

1. With the application of air, Park Lock releases automatically.

2. By mechanical means. No special wrench is required. Pliers, screw-driver or coin can be used.

IS PARK LOCK SAFE?

Park Lock is a true safety device. Any child can dismantle it without danger (no explosion hazard).

DOES PARK LOCK WORK ON EQUIPMENT PRESENTLY IN USE?

(Units in service prior to S-121 and September 1, 1974)

Park Lock can be installed on all trailers, new and used. The Relay Emergency Value and air tank, currently on all trailers, applies your brakes. Park Lock holds your brakes mechanically, thus preventing trailer roll-offs.

IS PARK LOCK DURABLE?

The Park Lock casting is made of especially treated aluminum, for long, tough wear. Park Lock has four movable parts that include a special brake rod. Park Lock is mounted on your present brake chamber and plumbed into the Relay Emergency Value. Installation is easy and simple. The Park Lock weighs about two pounds.

PARK LOCK AND S-121 (After September 1, 1974)

Park Lock passes all requirements under S-121, pertaining to both parking brakes and emergency brakes for your trailers. It is used in conjunction with a Relay Emergency Value and air tank (same tank used under S-121 to release the spring brake).

Park Lock works in conjunction with your New Anti-Skid Braking System and allows you to come to a complete anti-skid stop. This is accomplished by plumbing the air (emergency mode) back through the anti-skid computer valve.

Park Lock can be released from the tractor cab by the same method used to release the spring brake. As required by S-121, Park Lock has a manual release that can be released from the unit.

HOW DOES PARK LOCK SAVE YOU MONEY?

Park Lock eliminates trailer roll-off accidents. This will reduce insurance claims. . . thus reduce insurance premiums.

Park Lock virtually eliminates replacement costs. There are few moving parts.

The sole function of Park Lock is to hold your brakes, once applied; therefore there is virtually no wear on the units.

Park Lock requires very little maintenance, which eliminates down time.

Park Lock eliminates wheel-chocking and need for expensive chocks, chains, and locks.

Park Lock protects your landing gears. No more damage to the landing gear caused by hooking the tractor to the trailer, running fork lifts into the trailer while loading, etc.

(Illegible Words) FIND OUT MORE ABOUT PARK LOCK?

For more information about Park Lock write or call

PARK LOCK, INC. 8240 C Moberly Dallas, Texas 75272 (214) 381-2237

(Illegible Text)

(Graphics omitted)

INVENTORS

Woller Case William F. Benefield to and communicating with said first bore, the said brake actuating red having a series of rack teeth transversely thereof and operatively extending through said first bore and connected at one end to said power element and connected at its opposite end through a linkage to said brake crank and a spring biased pawl rod in said second bore and a salenoid coil connected into the electrical system of said vehicle and embracing said pawl rod whereby, which said salenoid coil is energized, the pawl rod is operated to (Illegible Word) the rack teeth on said brake actuating rod and restrain the same in position to set the brakes.

2. In a brake getting mechanism, as described in claim 1, the said spring actually biasing the pawl rod in retracted position to (Illegible Words) said pawl rod being extended to engage said brake actuating rod by said solenoid against the tension of said spring.

3. In a device as described in claim 1, and a collar on said pawl rod for adjusting the tension of said compression spring.

(Illegible Line)

UNITED STATES PATENTS

(Illegible Table)

GEORGE E. A. HALVOSA, Primary Examiner

UR Ct. XR 74-503; 192-3; 188-163

ID: nht74-2.22

DATE: 06/12/74

FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA

TO: Southern Railway System

TITLE: FMVSS INTERPRETATION

TEXT: In your letters of January 10, 1974, and May 17, 1974, you have asked if a trailer would comply with S5.8 of Standard No. 121, Air brake systems, ("have a parking brake system. . . when the air pressure in the supply line is at atmospheric pressure") if its parking brake system contained a valve that allows manual release of the parking brake with the supply line at atmospheric pressure but automatically resets itself when the supply line is pressurized, so that the parking brake system operates as specified by S5.8. Such a valve would permit limited motion of trailers on flat cars to cushion shock experienced during transit.

Such a valve does not appear to conflict with the intent of S5.8 that the parking brake system apply when the supply line is at atmospheric pressure. The requirement is not intended to interfere with intentional manual release of the parking brakes after automatic application has occurred. The danger of inadvertent disablement of the parking brake system during subsequent highway travel is avoided by the automatic features which would return the system to normal operation as soon as the trailer is connected to a source of air pressure, i.e., a tractor.

Sincerely,

ATTACH.

May 17, 1974

Richard B. Dyson -- Assistant Chief Counsel for Regulations, National Highway Traffic Safety Administration, U. S. Department of Transportation

Dear Mr. Dyson:

Please refer to my letter dated January 10, 1974, and I also refer to my telephone conversations of May 17 and earlier with Mr. (Illegible Word) of your office, concerning the problems created for trailers to be used on railroad flat cars by the new requirements for parking brakes.

Attached is a memorandum dated May 17, 1974 from Southern Railway's Assistant Vice President - Engineering & Research C. E. Webb, explaining why there is a need for a parking brake system on a trailer which will allow it to move longitudinally along a flat car for a short distance during impact. Read literally, Section S5.8 of the new regulations would require a trailer to be equipped with a parking brake designed so that the trailer would be incapable of this short longitudinal movement on impact. Mr. Webb in his memorandum proposes parameters for a device, to be developed by the manufacturers and approved by DOT if necessary, which would achieve the purpose of the new regulation when the trailer was in over-the-road use, while at the same time meeting the need for a means to "cut out" the parking brake when the trailer is on a rail car. Mr.

Webb envisions a fail-safe device. I might add that by proposing the device described by Mr. Webb, Southern intends to take no exception to a change in the rules which would be more liberal, that is, allow devices to be put on trailers that would also allow the manual disabling of the parking brake in other situations where it may be desirable, e.g., in freight yards during hostling.

As I said in my January 10 letter, we believe @ 5.8 does not forbid installation of a device like that described by Mr. Webb. However, in order to interest manufacturers in developing the device, we feel it important that your agency indicate that it would be proper and permissible under your regulations. Therefore, we would appreciate receiving advice from you to that effect, if that is the view of your agency.

Thank you.

Yours sincerely,

William P. Stallsmith, Jr. Senior General Attorney -- SOUTHERN RAILWAY SYSTEM

ID: nht74-2.23

DATE: 09/24/74

FROM: AUTHOR UNAVAILABLE; James B Grefory; NHTSA

TO: Midland-Ross Corporation

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Midland-Ross' February 8, 1974, petition for an amendment of S5.1.2.1 and S5.2.1.2 of Standard No. 121, Air brake systems, to establish separate air reservoir volume requirements for several brake chamber types generally available in the air brake component market.

The standard presently requires air reservoir volumes to be a multiple of the vehicle's brake chamber volumes. Midland-Ross also requested that S5.1.2.2 and S5.2.1.3 be amended to require that a reservoir withstand hydrostatic pressure five times greater than stated on its label without rupture, or permanent circumferential deformation exceeding one percent. The standard presently requires that an air reservoir withstand internal hydrostatic pressure of five times the vehicle compressor cutout pressure or 500 pounds, whichever is greater. The pecition also requests modifications of the trailer test rig, which were made in a recent amendment of the standard (39 FR 17563, May 17, 1974).

You suggested that our requirement for air reservoir volume as a multiple of brake chamber volume will encourage installation of smaller equipment and thereby create a safety problem. We cannot agree, in view of the standard's stopping distance requirements which in effect mandate the installation of high performance components. Indications to date are that manufacturers have in fact not reduced brake chamber volumes. A certain degree of chamber stroke standardization may occur, which the NHTSA views as favorable. For these reasons your request is denied.

With regard to the air reservoir pressure requirements of S5.1.2.2 and S5.2.1.3, you argued that a reservoir manufacturer is unable to establish the required strength of his product because he cannot control the compressor cutout pressure of the vehicle on which the reservoir is installed. It should be understood that the standard is not an equipment standard with which Midland-Ross must comply, but a vehicle standard with which the vehicle manufacturer must comply. We have determined that the reservoir should be designed to manage the pressures to which it might be exposed on the vehicle on which it is installed. The vehicle manufacturer is able to establish a compressor cutout pressure (on powered vehicles, and, based on that value, order the appropriate reservoir to meet the requirement. It is evident that commercial considerations will standard compressor cutout pressures on reasonable range of available reservoir strengths. Midland-Ross as a manufacturer of reservoirs is free to establish a range of reservoir strenghts, and label the reservoirs as described in your petition. For the reasons cited, however, your petition to mandate this is denied.

We agree the requirement that a reservoir "withstand" a certain pressure can be further specified, and we are considering a proposal to do this in the future.

At this time the NHTSA has adopted the SAE Standard No. J10a, which specifies that there be no rupture or permanent circumferential deformation exceeding one percent.

Sincerely,

ATTACH.

PETITION FOR RECONSIDERATION

FEDERAL MOTOR VEHICLE SAFETY STANDARD 121 DOCKET 73-13 NOTICE #3

BY POWER CONTROLS DIVISION MIDLAND-ROSS CORPORATION

M. J. Denholm Director of Engineering

February 8, 1974

Midland-Ross regrets to find that several of the proposals issued under Notice 1 of Docket 73-13 have not been incorporated in the rule issued under Notice 3 of the Docket.

The purpose of this petition is to request reconsideration of outstanding petitions and comments not yet resolved or acted upon from previous notices. In addition, we wish to offer additional information to supplement our comments on Docket 70-16 and 17, Notice 3, and the petition for reconsideration of Docket 70-17, Notice 4.

Taking the sections as they appear in FMVSS 121 as amended by Docket 73-13, Notice 3, we ask for your consideration of the following:

S5.1.2.1

S5.2.1.2

On March 23, 1972, we petitioned for consideration of this section of Docket 70-16 and 70-17, Notice 3.

Quote: "The combined volume of all service brake chambers at maximum travel of the pistons or diaphragms" requires definition in that volume can be measured in more than one way resulting in significant variation in result. For example: Displacement determined by pressurizing a chamber hydrostatically to 5 psig would result in approximately 10% less volume as compared to that indicated when the same chamber is pressurized to 100 psig hydrostatically. The hydrostatic pressure would be applied using an incompressable fluid; the volume of fluid displaced being the measure of the chamber volume. We recommend the standard be revised to read as follows:

'S5.1.2.1 . . .the combined volume of all service brake chambers at maximum travel of the pistons or diaphragms when measured with 5 psig applied to the chamber.' This will eliminate the possibility of a dual standard when determining compliance."

On August 14, 1973, we petitioned again for reconsideration of this section of Docket 70-17, Notice 4; and again on July 11, 1973, against Docket 73-13, Notice 1.

Quote: "The requirement under both these sections is restrictive and not necessarily in the public interest. For example, Midland-Ross Type 30 service chambers provide 2.75 inch stroke where units of other manufacturers are as low as 2.5 inch. The long stroke provides a desirable margin for poor brake adjustment. We believe this advantage will render our product non-competitive. To become competitive a reduction in stroke, with the attendant reduction in reservoir capacity requirement will be necessary. We feel, in light of recent experience with designs to meet FMVSS, 121, Notice 4, that this is arbitrary and an unnecessarily expensive retrograde step, caused by the wording of this section. In addition, chamber displacement varies dependent upon the applied pressure.

"This is caused by ballooning of diaphragms as pressure is increased. It should be noted that a three or four axle rigid truck would require significantly larger reservoirs under this rule than would a two-axle tractor designed to tow two or three trailers. Taking into account these three factors, it is recommended that S5.1.2.1 and S5.2.1.2 be reworded as follows:

'S5.1.2.1 The combined volume of all service reservoirs and supply reservoirs shall be at least the value obtained by the following product: Buses, and tractors and trailers designed to tow air-braked vehicles:

(12) x (115%) x (Combined volume of all service brake chambers)

Trucks not designed to tow other air-braked vehicles: (8) x (115%) x (Combined volume of all service brake chambers)

The combined volume of all service brake chambers is that volume obtained at maximum travel of the pistons or diaphragms with 100 psi hydrostatic pressure applied to the chambers with the brakes adjusted as specified by the vehicle manufacturer for new, unburnished brakes.

'S5.2.1.2 The total service reservoir volume shall be at least the value obtained by the following product: (8) x (115%) x (Combined volume of all service brake chambers)

The combined volume of all service brake chambers is that volume obtained at maximum travel of the pistons or diaphragms with 100 psi hydrostatic pressure applied to the chambers with the brakes adjusted as specified by the vehicle manufacturer for new, unburnished brakes."

No action has resulted from any of these petitions. We feel both arguments are still valid. We would like to add additional argument to that furnished on August 14, 1973, as follows:

An optional method of determining reservoir volume would consist of using an established minimum working volume for each standard size of service chamber. The minimum working volume would then be used to compute the reservoir requirement in the manner stated in the standard. Using this approach, the need for the changes recommended on March 23, 1972, would be eliminated also. We therefore recommend the S5.1.2.1 be reworded as follows: S5.1.2.1 The combined volume of all service reservoirs and supply reservoirs shall be determined by adding the volumes specified in Table V, Column 1 for each air-operated service brake actuator.

S.5.2.1.2 shall read:

S5.2.1.2 Total service reservoir volume shall be determined by adding the volumes specified in Table V, Column 2 for each air operated service brake actuator.

TABLE V Reservoir Volume Required Per Actuator * Column 1 * Column 2 Actuator Trucks-Buses Trailers Type 9 Diaphragm 240 cubic inches 160 cubic inches Type 12 Diaphragm 300 cubic inches 200 cubic inches Type 16 Diaphragm 528 cubic inches 352 cubic inches Type 20 Diaphragm 612 cubic inches 408 cubic inches Type 24 Diaphragm 732 cubic inches 488 cubic inches Type 30 Diaphragm 1056 cubic inches 704 cubic inches Type 36 Diaphragm 1464 cubic inches 976 cubic inches

*Piston or Rolling 12 x volume at max. 8 x volume at max.

Diaphragm working stroke working stroke

The above revisions to S5.1.2.1 and S5.2.1.2 are requested due to the variation in design of diaphragm type service brake chambers. These chambers are of generally similar construction, but because of manufacturing tolerances and slight differences in stroke length, their maximum volumes are different by a few percentage points. The current reservoir volume requirement based on maximum displacement encourages the use of small volume chambers (to reduce required reservoir volumes). In use, however, these small volume chambers provide less reserve than larger displacement units. This is true because the larger displacement units generally have slightly longer operating strokes. This additional stroke is a safety advantage in event that brake drums expand from heat buildup or shoes are allowed to wear without brake readjustment.

The chamber volume differences caused by variations in maximum stroke length are not significant to a vehicle in normal operation. This is because either chamber design would require the same amount of air to operate a properly adjusted brake; either unit when stroked to the same distance (any value short of maximum stroke; would displace nearly the same volume of air. Chamber volume requirements per brake application would be the same for either chamber design unless the stroke exceeded the maximum stroke length of the short stroke chamber. In that case, (abnormal situation) the long stroke chamber would require more air than a short stroke unit but would produce brake torque to stop the vehicle. The short stroke unit would be stopped internally without producing brake torque.

If S5.1.2.1 and S5.2.1.2 are not revised, market pressure will force redesign of long stroke chambers to limit stroke (and maximum volume). This could be carried to an extreme whereby the redesigned chambers would have even shorter strokes than current chambers. This type unit would then have economic advantages that would encourage their use; but they would actually be inferior to current chambers from a safety point of view.

The chamber volumes proposed in Table V were arrived at by applying the current requirement of 12 times chamber volume at maximum stroke (eight times for trailers) to the maximum volume of the truck industry's most common air brake chamber. These values do not represent a change in the spirit of the law, only in its detail. The original method of determining reservoir volume would be retained for piston actuators or other devices whose stroke and displacement have not become standardized in the industry.

S5.1.2.2

S5.2.1.3

On March 23, 1972, we petitioned for reconsideration of both of these sections of Docket 70-16 and 70-17, Notice 3.

Quote: "The requirement that the reservoirs under both of these sections should 'withstand' an internal hydrostatic pressure is nondefinitive and open to interpretation. In addition, manufacturers of air brake reservoirs are not necessarily in a position to determine what the cutout pressure of the compressor will be for a particular reservoir application prior to design and development of the reservoir as required under Paragraph S5.1.2.2. In addition, there is a significant inconsistency between the requirements for reservoir strength on a truck or bus and those for reservoirs used on a trailer as both reservoirs on a combination vehicle would be pressurized by the same compressor to the same pressure levels. It would appear reasonable, in the interest of safety, to adopt a common standard. It would also appear to be advisable to use a standard which is both proven and perfectly acceptable based on long periods of experience. It is therefore recommended that Paragraphs S5.1.2.2 and S5.2.1.3 be revised as follows:

'Each reservoir shall be capable of accepting a hydrostatic pressure of not less than five times the reservoir rated working pressure for a minimum of one minute. When subjected to this pressure for this time period there shall be no rupture or permanent circumferential deformation exceeding 1%. The reservoirs meeting this requirement must be permanently identified for rated working pressure."

On August 14, 1973, we again petitioned for reconsideration of these sections of Docket 70-17, Notice 3. Comments were also made on Docket 73-13, Notice 1.

Quote: "The requirement that the reservoirs under both of these sections should withstand an internal hydrostatic pressure is nondefinitive and open to interpretation. In addition manufacturers of air brake reservoirs are not necessarily in a position to determine what the cutout pressure of the compressor will be for a particular reservoir application prior to design and development of the reservoir as required under Paragraph S5.1.2.2. In addition, there is a significant inconsistency between the requirements for reservoir strength on a truck or bus and those for reservoirs used on a trailer. Both reservoirs on a combination vehicle would be pressurized by the same compressor to essentially the same pressure levels. It would appear reasonable, in the interest of safety, to adopt a common standard. It would also appear to be advisable to use a standard which is both proven and perfectly acceptable based on long periods of experience. It is therefore recommended that Paragraphs S5.1.2.2 and S5.2.1.3 be revised as follows:

'Each reservoir shall be capable of accepting a hydrostatic pressure of not less than five times the reservoir rated working pressure for a minimum of one minute. When subjected to this pressure for this time period, there shall be no rupture or permanent circumferential deformation exceeding 1%. The reservoirs meeting this requirement must be permanently identified for rated working pressure.'

Note: This recommendation reflects the current SAE Standard Practice (SAE J10b) in regard to reservoir certification and therefore should provide clarification without creating unnecessary hardships."

An additional point which was not specifically made in the two petitions quoted from relates to manufacturing practice and product application.

As a major reservoir manufacturer, Midland-Ross produces all reservoirs for air-braked vehicles in one of three diameters. Each diameter is engineered from differing material thicknesses to withstand a predetermined working pressure. Usually this is 150 psi. When reservoirs are supplied to the industry we have no knowledge of the compressor cutout pressure. The compressor cutout pressure is usually adjustable in service. A situation over which the reservoir manufacturer has no control. By establishing a maximum rated working pressure for the reservoir to be marked on the unit, the user then has direct knowledge of the limit to which the compressor cutout pressure can be safely adjusted. We feel that adopting this method would result in better understanding on the part of the user as this has been the standard used historically. It would eliminate the need to re-educate operators and provide a sounder basis for economic reliable manufacture and application of air brake reservoirs.

S5.3.3

S5.3.4

On March 23, 1972 we pointed out in our petition for reconsideration the inadequacies of the test standard shown in Docket 70-16 and 70-16, Notice 3, Figure 1. Partial response to this petition was exhibited in Docket 73-13, Notice 1, S6.1.12.

Docket 73-13, Notice 3, essentially returns to 70-17, Notice 3 level, thus effectively ignoring our original petition and also our comments on Docket 73-13, Notice 1, submitted to the Administration on July 11, 1973.

We ask for consideration of our updated proposal as follows:

S5.3.3 Brake actuation time. With an initial service reservoir system air pressure of 100 psi, the air pressure in each brake chamber shall reach 60 psi in not more than 0.25 second measured from the first movement of the service brake control. A vehicle designed to tow a vehicle equipped with air brakes shall be capable of meeting the above actuation time requirement with a 50-cubic-inch test reservoir connected to the control line coupler. A trailer shall meet the above requirement with its brake system connected to a trailer timing test rig as shown in Fig. 1 which meets the requirements of S5.3.3.1 and S5.3.3.2.

S5.3.3.1 The following should be added:

"The trailer test rig shown in Fig. 1 shall be constructed such that the pressure in a 50 cubic inch test volume connected to the control coupling is raised from zero to 60 psi in .063 second minimum when tested on the test rig. Time shall be measured from the first mechanical movement of the device controlling air flow to the control coupling."

S5.3.3.2 The following should be added:

"The trailer test rig shown in Figure 1 shall be constructed such that the pressure in a 50 cubic inch test volume connected to the control coupling is exhausted from 95 to 5 psi in .220 second minimum when tested on the test rig. Time shall be measured from the first mechanical movement of the device controlling air flow from the control coupling.

Figure 1 should be revised as shown:

(Graphics omitted)

S5.3.4 Brake release time. With an initial brake chamber air pressure of 95 psi, the air pressure in each brake chamber shall fall to 5 psi in not more than 0.50 second measured from the first movement of the service brake control. A vehicle designed to tow another vehicle equipped with air brakes shall be capable of meeting the above release time requirement with a 50-cubic inch test reservoir connected to the control line coupling. A trailer shall meet the above release time requirement with its brake system connected to the test rig shown in Fig. 1 and which meets the requirements of S5.3.3.1 and S5.3.3.2.

The above changes to Section S5.3.3 and Figure 1, and additions to S5.3.3.1 and S5.3.3.2 are recommended in an effort to more completely define the TRAILER TEST RIG. Until this rig is defined, uniform timing will not exist on trailers built to FMVSS 121. The original Figure 1 was designed to duplicate a tractor. It did this but as a test instrument it is inadequately defined. The air delivery performance of this device (as well as the tractors it was modeled from) will vary significantly. This is unacceptable when proof of vehicle compliance to the standard depends upon tests made with this unit. The proposed Figure 1 is a black box with narrowly defined performance characteristics. Devices built to this requirement will undoubtedly exhibit performance variations when tested against one another, but their level of consistency will far exceed that obtained by a unit in the standard which is only partly defined.