Interpretation ID: nht74-2.13
DATE: 09/30/74
FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA
TO: Nabors Trailers, Inc.
TITLE: FMVSS INTERPRETATION
TEXT: This responds to your August 21, 1974, question whether a "logging pole trailer", which consists of a beam to which an axle-mounted bolster can be clamped at different points to accomodate different log lengths, qualifies as a heavy hauler trailer as that term is defined in Standard No. 121, Air brake systems:
"Heavy hauler trailer" means a trailer with one or more of the following characteristics:
(1) Its brake lines are designed to adapt to separation or extension of the vehicle frame; or
(2) Its body consists only of a platform whose primary cargo-carrying surface is not more than 40 inches above the ground in an unloaded condition, except that it may include sides that are designed to be easily removable and a permanent "front-end structure" as that term is used in @ 393.106 of this title.
This also acknowledges receipt of your September 5 and September 17, 1974, letters on the same subject.
The logging pole trailer you describe is a heavy hauler trailer, and as such, Standard No. 121 does not apply to this trailer until September 1, 1976. The beam or "reach", together with the bolster, constitutes the frame of the trailer, and the brake lines are designed to adapt to extension of the bolster element along the beam.
This arrangement differs from the standard highway van which has a one-piece frame with an adjustable tandem axle. The purpose of this sliding arrangement is unrelated to an extension of the frame itself to accomodate the transportation of heavy or oversize loads.
Yours truly,
ATTACH.
NABORS TRAILERS, INC.
Sept. 17, 1974
Sidney Williams -- National Highway Traffic Safety Administration
Dear Mr. Williams:
It should be of interest and concern to the National Highway Traffic Safety Administration that we have not had the sight nor the specifications nor the price of a brake equipped axle assembly that can be certified to meet the requirements of Federal Motor Vehicle Safety Standard 121. We are wholly dependent upon the one source for our brake axle assemblies. From that source we have been told that they have encountered one delay after another in their program to develop and test brakes that will meet the new requirements. Their best hope now is that by the end of October they will be able to give us technical information and sometime in November they will be able to begin shipping certifiable brakes.
The same situation prevails with respect to wheel and drum assemblies. Our supplier of drums have told us that they are conducting tests now and that they should be able to tell us in November what drums will be required for compliance with the new Safety Standard.
You can guess from this information the predicament in which we find ourselves when trailers that we put into production in December scheduled for completion in January will be required by law to be in compliance with SS 121. We are certain that there are many other trailer manufacturers who are dependent upon the same sources of supply that we are who are in the same predicament. There may be other sources of supply for brake axle assemblies and for wheels and drums who are ready to describe and certify their products to meet the new Safety Standard, but we, for one, could not at this time get in schedule with new suppliers.
Sincerely yours, B. H. Smith -- President
NABORS TRAILERS, INC.
Sept. 5, 1974
Sidney Williams -- National Highway Traffic Safety Administration
Dear Mr. Williams:
On November 15, 1973 I sent a collection of our pole trailer catalogs and of photographs of logging pole trailers in service to the Truck Trailers Manufacturers Association in Washington. I thought that these had been sent over to your offices. Perhaps they never did get there. My letter went to Mr. M. L. Higgins who at that time was handling these matters for TTMA, and very shortly after that he resigned and Mr. Burt Weller took his place.
With this letter I am sending you two each of our Catalog 196 and our Form 198 describing our standard types of pole trailers.
The logging pole trailers described in Catalog 196 are those about which we are primarily concerned with respect to MVSS 121. Those trailers are designed and used exclusively in logging operations and move logs from the woods to the saw mills or to storage areas. Logging pole trailers are subjected to unbelievably difficult conditions, or at least unbelievable to those who have never witnessed difficult logging operations. Maintaining brakes and lights on logging pole trailers when the very minimum of equipment is used is difficult and often impossible. When the hardware that is required for compliance with MVSS 121 is added to braking equipment as now being used, the difficulties of maintenance will be multiplied and the likelihood that the brakes will be kept operational is reduced.
On the inside of Catalog 196 you will see good views of the rear assembly of our two popular models, the Logmaster and the SPR. These two trailers are identical in capacity and in usage, and the two models are built simply because some loggers like one type and some like the other. In both models you will see that the rear bolster sits on a frame that sits on the two-spring suspension that sits on the axles. A pole or drawbar connects the front bolster assembly to the rear assembly. The rear assembly can slide along the pole to change the distance between the front and rear bolsters to accommodate various log lengths. If you look closely you will see that the rear assembly is locked into place on the pole by means of clamping collors around the coupling pole ahead of and behind the rear assembly. Also, for safety purposes a pin is dropped through the pole at the rear to avoid the possibility that the trailer might slide off the pole.
You will see in the illustrations that the two hoses for the brakes and the cable for the lighting on the rear assembly are connected to the truck or to the front bolster assembly at the front and are connected to the rear assembly at the rear with quick detachable couplings. You will see that when the distance between the bolsters is relatively short these brake and light lines must be coiled up and supported by the pole. If the trailer should be extended in length, the full length of these lines would be required. It is a characteristic of these trailers that the brake lines are designed to adapt to permitting the distance between the front and rear bolsters to contract and to expand.
Another common practice in the use of logging pole trailers is to load the rear frame assembly on the back end of the truck when the trailer and truck are being carried unloaded back into the woods. This practice is for both economic and safety reasons. When the rear assembly is loaded on the truck the brake lines must be disconnected. Also, no part of the brake system can extend below the bottom of the axles because the axles must rest on the truck frame or on the runners that are put on the truck frame to carry the trailer.
When you look closely at these pictures of these logging pole trailers you will observe that the space between the axles and the load-carrying bolster is limited and is filled with equipment with current types of brakes. The trailers shown have only one air reservoir. In order to comply with MVSS 121 another larger air reservoir will have to be added. There simply is no place to put it on these logging pole trailers without interfering severely with their intended usage. If in addition to this other air reservoir we must add spring-loaded power chambers and the valves and logic boxes and electrical connections required for the anti-skid brake system, it is up to now inconceivable to us how to add that hardware in such a way that it could reasonably be expected to stay on the trailers when they are used in the log woods.
The Models TP and TPC Pole Trailers illustrated in our Form 198 are designed and used primarily for hauling pipe and poles and reinforcing rods and long steel beams and other, long and self-supporting objects. The same difficulties in adding the anti-skid brake equipment and the spring loaded power chambers apply to these trailers as to the logging pole trailers. However, since these two models are used primarily on improved roads the difficulties of maintaining the equipment would not be as great. Trailers of these two models constitute no more than perhaps 50 units a year for us. They do have the same characteristic of logging pole trailers in that the brake lines are designed to be adapted to permitting the distance between the front and rear bolsters to change. There would be the same difficulties on these trailers in getting the speed of brake application and release that there would be on other pole trailers.
I can understand the difficulty of writing an exemption for any one class or category of trailers without letting the exemption be subject to unintended interpretations. However, it has seemed to me since we first became concerned with the problems of MVSS 121 that pole trailers as defined in Part 371.3 of the Federal Motor Vehicle Safety Standards could be exempted without any reasonable misunderstandings. Pole trailers as defined in Part 371.3 were exempted from the requirements of MVSS 108 and have been exempted from certification requirements. I have not understood why they could no also be exempted from MVSS 121, and I think that their categorical exemption would be beneficial rather than detrimental to the highway safety program. I have made all of these statements previously in letters to the National Highway Traffic Safety Administration and to the Truck Trailer Manufacturers Association.
We appreciate very much your consideration of our problems and I thank you again for your telephone call on September 3rd in response to our letter of August 21st.
If it might be helpful to giving you and others concerned a better understanding of our problems, which we think are shared by many others, I would be willing to come to Washington for a conference.
Sincerely yours, B. H. Smith -- President
Enclosures
NABORS TRAILERS, INC.
August 21, 1974
Sidney Williams -- National Highway Traffic Safety Administration
Subject: FMVSS 121 - Air Brake Systems, Docket #74-10, Notice 5
Dear Mr. Williams:
We are unable to determine from the subject Notice 5 and from the discussions and considerations that preceded it whether or not it is the intention of NHTSA that Logging Pole Trailers be considered "Heavy Hauler Trailers" within the definition of that category.
In one way of looking at it nearly all Logging Pole Trailers come within Characteristic (1) of the definition because the brake lines are designed to adapt to permitting the rear frame assembly of the pole trailer to slide on the pole or drawbar and thereby to adapt to extension or contraction of the effective length between the load bearing members. In another way of looking at it, pole trailers would not come within Characteristic (1) because there is no actual separation or extension of the vehicle frame. Actually, in pole trailers there is no frame as such connecting the front and rear load bearing members.
The one consistent and definitive characteristic of pole trailers, as we understand them, is that they consist of a front bolster that rests on the towing tractor and a rear bolster that rests on the trailer suspension and axles with the two connected with a pole on which the rear assembly can slide forward and backward.
In some logging operations the length between the front and rear bolsters is changed frequently, maybe daily. In some operations the length between the bolsters is changed only as the species or types of logs being hauled change. In some operations, on every unloaded trip the rear assembly is moved forward on the pole and is loaded on the truck to be hauled back into the woods. Since logging conditions and practices require different effective lengths between the front and rear bolsters and different problems with respect to the brake lines, practically all of our Logging Pole Trailers are rigged out with quick disconnectors for the brake and light lines at the rear assembly, and to that extent the rigging is similar to that on extendable platform trailers. The difficulties of maintaining good air line connections and unrestricted flow of air are certainly as great on pole trailers as on extendable frame trailers.
There are other inherent problems in applying and maintaining brakes on Logging Pole Trailers that in our opinion should be considered before there is a requirement upon trailer manufacturers to add anti-skid devices, spring loaded power chambers, dual or triple air reservoirs, and the other hardware that goes with the system. For example, up to now we have not been able to devise a way to put spring loaded power chambers on the axles of Logging Pole Trailers without swinging them under the axles. We definitely do not have sufficient clearance for putting the spring loaded power chambers over the axles with the suspensions and construction that we are using now. To put the (Illegible Word) chambers under the axles on pole trailers that are destined for the logging woods is, in our opinion, impracticable. The operators will not be able to keep the power chambers in place. The net result will be that they will knock them off or take them off the trailers and run the trailers without brakes. We run into similar but not insoluble problems with respect to installing additional air reservoirs and all of the other wiring and hardware required in an anti-skid system, but the trailers will have to be redesigned, they will be made substantially more expensive, and they will be less suited to their purpose.
Opinions have been expressed that we should simply assume that the definition of Heavy Hauler Trailers does embrace Logging Pole Trailers and that we should bother ourselves and our customers no more about the problem. We are not willing to leave it there because we cannot afford to be found in violation of the law and to be required to go back and add equipment which we did not furnish when the trailers were built. If we must put the anti-skid equipment on Logging Pole Trailers we must be getting ready for it in our designs and in our production methods, and we must be preparing our customers for the added cost and for the maintenance problems that will be inevitable.
Pole Trailers make up hardly more than 1% of the truck trailers that are manufactured. According to the Bureau of the Census Industrial Report for May, 1974, 189 pole trailers were shipped in May 1974, 214 in April 1974, and 177 in May 1973. For ourselves, the total volume in pole trailers is less than 300 units per year, but that is a substantial portion of our total volume and we are one of the largest suppliers of such trailers to the Southern lumber industry. Could you tell me exactly where we stand with respect to Logging Pole Trailers and MVSS 121?
Sincerely yours, B. H. Smith -- President