Hub thread pattern

[NPC59D]

Hello chaps

A quick question for you, relating to the original thread pattern on 427 hubs.

What was originally specified back in period; was it Rudge Whitworth, or something else, such as 2 3/8?

Any answers would be much appreciated.

Lee

[Dan Case]

Cobras, 427 Cobras, and 289 Sports all use the same center lock nut thread "size". The average I have measured on a collection of used and new old stock hubs covering all three chassis types is a minor diameter around 2.17" and a major diameter around 2.332" and threads cut at a 55° angle.

Halibrand Engineering supplied three wing center lock "knock off" nuts in forged and heat treated steel and aluminum versions for new 427 Cobras that were stamped "55" presumably to notify mechanics were type threads, by angle of cut, the hubs and or nuts had.

[NPC59D]

Thank you Dan; that's very much appreciated!

best regards from England.

lee

[MAStuart]

Dan do you know if the hubs and knock off nuts made today conform to this thread size and angle?

[strictlypersonl]

We've been using the same original wing nuts (Halibrand/Trigo) on our cars for 35 years. Even the Vintage Wheel wing nuts will interchange pretty well.

[Dan Case]

Originally Posted by NPC59D

Thank you Dan; that's very much appreciated!

best regards from England.

lee

You are welcome.

[Dan Case]

Originally Posted by MAStuart

Dan do you know if the hubs and knock off nuts made today conform to this thread size and angle?

I do not know, I have only measured original AC Cars made hubs. I had started drawings to have some front hubs made to the original design for my red car as a former owner had damaged them more than I wanted to use. Before I finished the drawings a pair great used original hubs became available so I bought them and stopped working on the drawings. The newest KOs I have were made by Halibrand circa 1969-70. Most of the KOs I have were made before the aluminum forging company name changed mid summer 1968.


New old stock AC Cars made hubs and new old stock Halibrand made nuts 1964 early 1968 nuts have a very snug fit thread wise. Used parts have quite variable fits.

[LMH]

Cobras use 42MM series hubs with 8 TPI on the knock-off thread. Not sure what modern adapters use for thread. Could also be different depending on manufacturer for modern adapters.
Larry

[Dan Case]

Originally Posted by LMH

Cobras use 42MM series hubs with 8 TPI on the knock-off thread. Not sure what modern adapters use for thread. Could also be different depending on manufacturer for modern adapters.
Larry

Like many “Cobra” subjects, hubs is not a real straight forward one.

CSX2601 and CSX2602 (Daytona Coupes) dropped the splines as did 427 Cobras. "42 mm splines" returned for 289 Sports.

There were street car splined hubs, street car rear splined hubs in a stronger alloy, street car splined hubs converted to pin drive, race car hubs with splines drilled only for six pins, race car rear hubs made of a stronger alloy splined but drilled only for pin drive, 427 Cobra hubs short and long, and 289 Sports hubs that were splined.

Front hub forgings could be machined into just about anything. Rear hub blanks could be machined into almost anything. They all used the same center lock nut thread system.

I have used samples of most and new old stock of one of the rear street Cobra versions. When I started studying front hubs I was quite surprised that Cobra, 427 Cobra, and 289 Sports were all done differently and are not by themselves bolt off bolt on interchangeable. Rear hubs also don’t exactly interchange between Cobras and 427 Cobras. I have a rear 289 Sports hub but I have yet to by feature and dimensionally compared it to Cobra and 427 Cobra versions.

[CompClassics]

On the "55" stamped original production line knock-offs the "55" indicated the thread pitch. Dan made reference to a manufacturer change, it was from Harvey to Alcoa, I believe Alcoa bought Harvey.

[Dan Case]

Originally Posted by CompClassics

On the "55" stamped original production line knock-offs the "55" indicated the thread pitch. Dan made reference to a manufacturer change, it was from Harvey to Alcoa, I believe Alcoa bought Harvey.

Correct X2

As far as I know Halibrand made KOs were not stamped with 55 until 427 Cobra street car completion started. Speculation on my part is that parts for GT40 MKIIs might have been on hand by that time???? Cobra race car owners don't want the stamp while 427 Cobra owners do. Did you know that it was not rare for CSX33xx cars to be delivered with steel nuts on one side of the car and aluminum ones on the other side? (Circa 1969 Halibrand released a new steel nut with rounded ends on the wings. Guess where I see them most? On CSX33xx cars. I just cannot help but wonder if owners / dealers took the opportunity to have all four nuts on late cars the same design and material? Interesting to think about since some cars didn't get sold new until 1969. That gets to the issue of what "original" means to different people. Was "original" for many details, as cars left for delivery to a dealer or after dealer preparation for the first buyer.) Details, details....

Also GT40 MKIs converted from wire wheels have the same thread. GT40 MKII and MKIV have different threads and were normally dyed red or blue depending on direction of threads.

I have collected samples used or nos of every brass, cast steel, forged steel, and forged aluminum straight arm, forged aluminum curved arm, KO AC Cars, Shelby, Holman-Moody, FAV, or Kar Kraft used between the first street Cobras and last GT40 MKIV except the steel ones used on most 427 street Cobras. I have found some but each time a 427 Cobra owner pleaded to get “the last part” they were after. I have recorded which Cobra, 427 Cobra Comp car, MKI, MKII, and MKIV the used ones of those types came from. I have a front from a Daytona Coupe removed in 1968 but I have forgotten the chassis number and have not yet tried to figure it out again. I have a set of wire wheel nuts for a GT40 MKI but the chassis number has been lost to time.

Original wheel hubs and center lock nuts is a very complicated subject!

[Kit Coyle]

Will the "55" thread pitch steel knock off fit on a "60" pitch ERA six pin hub? Are
the hub, wheel and knock off bevel angle the same ? When did Halibrand
make the forged aluminum spinners with the small word "Halibrand" on each
of the three ears? I have the P.S. Engineering FIA wheels and the aluminum
"Halibrand" spinners as supplied by ERA.

[Dan Case]

Originally Posted by Kit Coyle

Will the "55" thread pitch steel knock off fit on a "60" pitch ERA six pin hub? Are
the hub, wheel and knock off bevel angle the same ? When did Halibrand
make the forged aluminum spinners with the small word "Halibrand" on each
of the three ears? I have the P.S. Engineering FIA wheels and the aluminum
"Halibrand" spinners as supplied by ERA.

Question 1: Me, I have no idea. I work only with the original designs and specifications.

Question 2: 1963-67 A) Probably as close as Halibrand Engineering could, they made the wheels and racing KOs. Putting machinist dye on one or the other and running them together shows a pretty good broad interaction. B) Depending on car type and wheel type the Shelby race team used nuts with two different size tapers over the 1965-67 time frame that I know of. Lots of factors come into consideration including but may not be limited to wheel design, wheel hub thickness, diametric “size” of the threads, hub length, and how many thread turns were on a given hub.

Question 3: As far as I can tell the aluminum blanks forged by Harvey Aluminum and the forged steel blanks of undetermined origin (which the Halibrand name in each wing) came out in either late 1963 or early 1964. I have not found either part’s original drawings. The Shelby race team previously used small cast steel KOs supplied by Ted Halibrand that had no markings on them except an X-ray inspection approval ink stamp when brand new. The cast steel parts with short arms were not tough enough for the big metal hammers race teams typically used; the arms broke off. I looked at one unrestored Cobra racer with cast steel nuts decades ago with two arms of three missing at one front corner.

Note 1: Over the past few decades several individuals or companies have created aluminum, steel, and stainless steel KOs marked with the Halibrand name. Just having “HALIBRAND” text on a part does not mean it was made by any version of the Halibrand company. Indeed, there are some rather fragile cast aluminum KOs out in public marked as being Halibrand.

Note 2: There are numerous genuine 1960s parts produced by Halibrand around in forged steel and aluminum that have been polished and or polished and chrome plated where the HALIBRAND text was removed during polishing.