Dimensions for Rudge-Whitworth 72 mm splined hubs???

[Gary_Ash]

I want to use Rudge-style wire wheels with knock-off spinners on my project to build a replica of a 1932 Studebaker Indy car. Because the front spindles are large in diameter, they take large bearings and cups, which has driven me to the 72 mm size of hubs and wheel centers. I can find people to build the wheels [for a price], but no one seems to have a drawing for the proper dimensions of the splined hub that the wheel goes on. I'm looking for dimensions taken from drawings or real parts. The 72 mm size seems to be rare. The people who actually sell some hubs of various sizes seem reluctant to share even basic dimensions. Because of variations in bearing sizes, brake drums, and wheel offset, splined hubs are made to designs unique for each car, and the front ones are different from the rear ones. And, the right and left sides get right and left threads for the spinners. Bolt-on hubs, particularly the current Dayton style, are a little more generic, but I didn't find any that would fit, and I still have to make hubs anyway. Wheels will be 18" x 4" wide with 70 spokes. Tires are 6.00-6.50/18 front and 7.00/18 rear, probably the new-style Excelsior radials.

While currently most of the hub and wheel parts are made in Europe or Asia using metric dimensions, you can bet that the Rudge people used inch sizes for everything when these were developed about 1908-1912. In particular, the spline circular pitch is 0.1 inch. Thus, the 72 mm hubs with 112 splines have a base circle of circumference 112 x 0.1 = 11.2 inches or a base circle diameter of 3.565". The individual splines are about the shape of a 60-degree thread with the tips and roots filleted to .016" radius, rather than sharp edges. The splines undulate up and down from the base circle. The resulting outside diameter is 3.62" or 91.9 mm and the root diameter is3.51" or 89.2 mm. The splines are something like 43-55 mm long, depending on who you ask. The wheel center has a mating spline, and it slides on until it seats on a 60-degree cone at the inside end. The outside of the hub has 3.5"-8 tpi thread for the spinner, and I think it is supposed to extend about 1/2" beyond the hub. I think there is supposed to be a ~10 mm gap between the threaded section and the splines and also between the splines and the start of the cone seat, but this isn't certain. Most of the dimensions I have came on a tattered copy of a page from a July, 1974 car magazine of unknown name in an article by Alec Ulmann - I wish I had the rest of the article.

I'm trying to be sure that I have hubs machined so that the wheels seat on the cone and spinner tightens it down correctly while centering the outer end. I think the big Bentleys from the 1920's and 1930's used the 72 mm size, maybe some U.S. cars. Does anyone have these dimensions for a 72 mm hub?

Edited January 18, 2014 by Gary_Ash (see edit history)

[DavidAU]

Have you had contact with these people. They may be able to help

http://www.vintagerims.com/Splined_Hubs_Vintage_Rims.html

[Gary_Ash]

Yes, Gary Morton at Vintage Rims in New Zealand is very helpful and knowledgeable , but he didn't have the spline dimensions for the 72 mm hubs. I suspect he makes the rims for many of the other wheel suppliers.

[DavidAU]

I dont know if this is any help to you but following is a sketch of a 62mm hub with the long spline that is on my Metallurgique. I did this some years back when

I was looking for wheels.

A photo of it also. (Sorry I dont have cad on my computer.)

The other photo is a 100mm hub on my 31 Rolls which I can give you measurements on if they are any use. The spline is 50mm long.

Edited January 20, 2014 by DavidAU (see edit history)

[Gary_Ash]

David:

Thanks for the photos and sketch. I am a bit confused because the splines on your cars look square and I thought the splines were V-shaped based on an article by Alec Ulmann back in 1974. Here is the only page that I have from the article, maybe someone will recognize it and have saved a copy for 40 years. Your dimensions, and the ones listed on the web sites of various wheel vendors, are different than the ones in the Ulmann article, but there do seem to be many variations on the theme. The 20 mm dimension for the length of the conical seat is very helpful as a guide.

I have ordered an extra wheel center so that I can examine it in detail before sending in the machining drawings for the hubs; it should be here in a few days. I have been told that hubs made in Europe use EN8/080M40 (= USA type 1040) or EN24 (=USA type 4340) steel. I'm planning on using 4140, normalized before machining, heated, quenched, and tempered after machining. The 4140 is a standard chrome-moly alloy with high strength and good machinability in the normalized state.

[bill pritchett]

Gary, just a thought. Since you mentioned the article above, you might try the AACA Library, you never know. They certainly have a lot of articles like that I would think.

[DavidAU]

Gary, The Metallurgique splines are V shaped and the Rolls-Royce ones are square.

[Gary_Ash]

Bill: As a matter of fact, I just sent the library an email with a research request. I wonder if that article appeared in the AACA magazine. I did ask that they check the 1974 volume of Antique Automobile. If it wasn't in the AACA magazine, they may still be able to find some info for me. Good suggestion!

[Guest Commodore]

I found the article by Alec Ulmann appeared in the Veteran Motor Car Club of America (VMCCA) publication "The Bulb Horn" Volume XXXV 1974 Number 4 Page 34. This information comes from the 1974 index. No copy of the article.

[Gary_Ash]

Wow, Commodore, that was some good searching! Now I just have to find a copy. However, based on the one page I do have that has the chart of some dimensions, they don't agree with what some vendors are offering. I am anxious to get a copy of the article because it will help to provide some more background. I sent off an email to the editors of the "Bulb Horn" requesting a copy.

The wheel center I ordered arrived today, made it from England to here in about 36 hours. It will be perfect as a gauge to check the machined splines. It looks like it was machined from bar stock and the splines broached on the inside. It's 8.25" o.d., 5.5" tall, 0.2" wall thickness, weights about 5.5 lbs. The photo of the grooves is a little deceptive because it exaggerates the groove depth since it shows where the grooves intersect a tapered surface. It's quite a piece of machining. I believe that it was made in India.