When I agreed to step into the Safety job for the Orange Empire Regional Group of the HCCA recently, I didn’t plan to make this column a report from personal experience, and I hope it won’t be in the future.



This happened at less than 10 mph, as the car was being towed on all fours, and the wheels didn’t return forward after a tight U turn. The wheel was dragged a total of less than 50 feet that way, on dry pavement, then dirt and gravel, and then a shock load as it hit dry pavement again.

This failure should not have happened; wheels need to be stronger than this. It could just as easily happen in a hundred other ways; for example, turning a corner going downhill, and slipping in gravel, then hitting dry pavement, or a bump or hole. Even assuming 1G traction from the tire, the dragging load was only about 500 lb. at an angle of about 35 degrees.

When I bought these wheels two years ago, the seller told me the spokes had been made about 20 years before by the late Frank Watts. They had been stored, and never used. Only after I had invested a lot of work in them was I told by another person, "Frank used only white oak." Before that, I hadn’t even dreamed that spokes would be made of anything but hickory. Now I know for sure what I feared at the time; I should not have used these wheels. Wishful thinking was stronger than common sense. However, since that time I’ve driven over 10,000 miles on these wheels, and towed them hundreds of miles more. I had just never hit their limit.

This is on CalimersWheelShop.com and was taken from a book written in the brass era:
“The wood of choice for auto wheels in America is hickory. Hickory is the primary wood used for wheels because it is strong and flexible. Some other woods are stronger or harder, but the combination of strength, toughness, yet flexibility has not been found in any other hardwood. Wheels require such a wood to last. Oak is not used in auto wheels because it can shatter across the grain.”

One of the seven oak spokes that broke:

I’ve found four outfits who say they rebuild wheels with only hickory: Calimer's Wheel Shop, Jim Kanne (503)638-5275, Vintage Wheel Shop (209- 533 0468), and Johnson's Wood Wheels. On the other hand, the individual spokes available from the major Model T vendors are all said to be oak. I’ve been told oak is used, “Because these old cars don’t get driven very much or very fast. Besides, hickory is harder to work with, and tools won't last as long. Also, hickory costs more.”

10 mph is not fast, friends.

The MTFCI has quite an active Forum, to which I have been sharing this experience, and learning from others. This came from John Regan: “On the Ford drawing for the spoke used on demountable wheels (F/N 3421-BR) they call out a load test for all spokes that props them up on 2 pillars 6-1/2" apart and applies a load midway between them. At this midway point each spoke must stand an average pressure of 2500 lbs with 2000 lbs min pressure. I suppose that to mean that all the spokes must pass 2000 lbs and half the shipment must meet 2500. That is more than 5 times your load estimate, Ralph. Hickory is the only wood specified. They were strong little buggers. The machines I found at the patent office for wood bending talked about making spokes too, and they always talked about using "split" wood which I am sure meant that they split the wood before sorting it into blanks for turning into spokes. Since wood would split along the grain it insured that the spokes would be "straight grained" and strong.“

The test rig I made, emulating the Ford test.
That’s a 0-50 lb scale on the left; pressure on the spoke is calculated.

The spoke began cracking at 900 lb in a test I made equivalent to the Ford test mentioned above. Major failure was at 1,000 lb. What is maybe even more important was the lack of bending before breakage. A shock load is easily much higher than a static test such as this. Oak spokes cannot absorb shock the way hickory does, and red oak is probably worse than white oak.

Ford bought or made about 700 million wood spokes for new Model Ts, plus millions more for replacements. From known archives, every one of that near billion spokes was hickory. If hickory was the only wood good enough for Ford, we shouldn't be using anything else.

Watch this space for a new, improved test using the car as the test load.

While I’m on the hunt for a set of hickory spokes, or complete wheels, I’ll go back to the #4 Houk wire wheels that have been trouble-free for over 50,000 miles on my Model Ts. The remaining spokes I have may end up in an oaken banister staircase as part of my planned garage addition. The risk of using or selling them is just too great.

How can you be sure the spokes on your car are hickory? Hickory has a much closer grain than oak, and it has color variations from blonde to medium gray (taupe?) Red oak has large pores and has more consistent color than hickory, so it makes a prettier wheel when it has a natural finish. White oak is somewhat better for spokes than red oak, but is still unsatisfactory.

Hickory

. . . Red Oak

White Oak . . .

For details on these woods, click on CC Doors

If a car is only garage furniture, then oak is ok.

Ralph Ricks 19 Nov ’03 . . . Rev. 6: 3 Dec ’03

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