Interpretation ID: nht74-2.5

DATE: 11/04/74

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

TO: Todco Division

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Todco's September 27, 1974, question whether Standard No. 121, Air brake systems, 49 CFR 571.121, requires a spring brake system on Todco's "Jifflox converter dolly." You describe the Jifflox dolly as a trailer converter dolly which may also be used as a "third axle attachment" on a two-axle truck.

Standard No. 121 applies to vehicles, and specifies separate requirements for trucks, buses, and trailers. It appears that the Jifflox is subject to separate requirements under the standard depending on its use.

If Todco manufactures (Illegible Word) sells the Jifflox for use as a "trailer converter dolly" (defined in 49 CFR 571.3 as a trailer equipped with one or more axles, a lower half of a fifth wheel, and a drawbar), it constitutes a vehicle subject to Standard No. 121. As such it is exempted from the parking brake system requirements (S5.6) and its emergency braking capability is not required to be applied by an emergency source, such as a spring brake, that is not affected by loss of air pressure or brake fluid pressure in the service brake system.

If a truck manufacturer utilizes the Jifflox as an additional axle in the suspension of its vehicle, the truck manufacturer must assure that the truck meets the requirements applicable to it with the Jifflox incorporated in it. This means that, if the truck is manufactured to accept the Jifflox dolly and the truck is rated for a gross vehicle weight rating that depends on inclusion of the axle, the truck must comply with all applicable requirements of the standard with the Jifflox attached. If the truck manufacturer determines that parking brakes are required on the Jifflox axle to meet S5.6.1 or S5.6.2, those parking brakes would have to be applied by an energy source that is not affected by loss of air pressure or brake fluid pressure in the service brake system.

Yours truly,

ATTACH.

September 27, 1974

Richard Dyson -- Chief Council, National Highway Traffic Safety Administration

Dear Mr. Dyson:

This is a second request regarding a ruling on the Jifflox Converter Dolly. This letter is in lieu of our first request of which our copy has been misplaced.

The Jifflox Converter Dolly has been manufactured, sold and licensed as a converter dolly. As stated in F.M.V.S.S.-121 paragraph S.5.8 a converter dolly need not have spring brakes. However, the Jifflox is unique in the fact that it can also be used as a third axle attachment.

In previous conversations with Mr. Sid Williams it has been his opinion that since the Jifflox is sold and licensed as a converter dolly it would be exempt from spring brakes. He reffered us to your office for an official ruling.

Since we deal directly with the truck manufacturers they are obviously concerned with this ruling. They have in fact requested from us an official ruling from your office.

I would think that since the Jifflox is sold throughout the United States, an ammendment to F.M.V.S.S.-121 would be in order. However an official ruling from your office in letter form would suffice.

Since we are a member of the T.T.M.A., I am forwarding a copy of this letter to Mr. Bert Weller, in hopes that research in this matter may be expedited.

If you have any questions regarding this matter, do not hesitate to contact me.

Sincerely

Frank L. Wigand, Eng. Dept. -- TODCO Division

cc: Joseph J. Cunha; Bert Weller