Has anyone ever come across a formula for calculating the spring rate of quarter elliptical leaf springs? I found some talk of it while searching the internet but no clear answer to yes this one works. I'm trying to figure up the different spring rates depending on which leaf I remove
Perhaps a better question is what is a good spring rate for the normal buggy spring in the first place, for any given weight on the front wheels? Ever seen any posted in catalogs? Then find out what each 1/4E should be from that?
What kind of a formula are you looking for? According to the Eaton Spring website the spring rate is simply the amount of weight it takes to deflect a spring 1”. Sounds pretty straight forward. Sent from my iPhone using The H.A.M.B. mobile app
I have messed around with that formula but it seemed weird it didn't account for the different lengths of each leaf. I guess I'm over thinking it and the length doesn't matter. I had heard it wasn't as easy as just dividing a regular leaf spring in half Just don't have anything to measure the weight with.
I will play with the formula on the tbucket forum a little more. Just trying to get an idea of how many leaves I should remove for the car since I can't drive it at the moment
So based on that formula the speedway quarter ellipticals require the following weight in pounds to move the spring 1 inch... 5 leaves 679.84 lbs/in 4 leaves 543.87 lbs/in 3 leaves 407.90 lbs/in 2 leaves 271.93 lbs/in 1 leaf 135.96 lbs/in I have a rough idea of the weight of the car but not the front rear split so I will see if I can find someone with some scales or get it to the track/truck stop
On the front of my '27 T I took two Model A type front leaf springs and cut them about 1 1/2' past the center bolt. I think I used 4 or 5 of the longest leaves. They were 1 3/4" wide by 1/4" thick. If the Speedway leaves are thicker you would probably need fewer leaves. The beauty of leaf springs is that you can add or subtract leaves to get the ride you want without buying whole new springs. My front quarter elliptics were stationary mounted but the rears were on adjustable pivots like Speedway/Posie's are. My T rode great, very smooth and stable.
L is the length (horizontal component?) of the longest spring. Try using the automatic formula in the link below to check your calcs. I'll be using 1/4 ellipticals all around, so this is great info to know. https://therangerstation.com/how-to_pages/leaf_spring_rate_calculator.shtml
my leaves are the same dimensions so similar setup. Glad to know you liked the ride! Any idea how much your T weighed. Last time we weighed mine it was 1600lbs
I'm thinking that link may be for regular leaf springs as all of my numbers were 34% less than the calculations it gave for the number of leaves. I'll reach out to Posie's and see what numbers they give or if they have a formula and report back.
I made the rear 1/4 elliptic suspension for the deuce lakester Dale Grau is building. I took a 33 inch rolled and tapered 1 3/4 wide front spring from Posie, cut it in half, re drilled the spring bolt holes. built my own front brackets, attached the spring to the rear with shackles and held the rear in place with ladder bars. The spring rate was just a guess based on the 1/4 elliptic set ups I'd used from Posie and a deuce roadster with a similar setup I built in 1983 that's got over 150,000 on it.
I never weighed it but I would guess it was 2000# or less. It was a boxed Model A frame with a 283/th350, 8” ford rear, and a glass 27 T body. It was like a big go kart but with suspension. I tried back then to science out the spring rates but without knowing the finished weight of the car and the weight bias you are still shooting at a ballpark figure. The logic I used was based on what a typical T bucket used for springs, the length of the actual flexing part and the number/size of the leaves. I attached the springs to the axle as close to the stock Ford spring perch width as I could. I worked out fine, I would certainly do it again. Sent from my iPad using The H.A.M.B. mobile app
So I heard back from Posie's but they wouldn't give me any spring rate numbers or dimensions of their springs ( they have a light duty set and heavy duty set) but for my setup 1800lb with straight six he suggested... "The light weight springs are typically used when running a 4 cylinder engine or something similar in weight. The rear applications always get the heavy version springs. With this setup, if the front was found to be lighter in weight the spring could be adjusted by removing the short leaf." So I guess I will take it for a spin after I get my new radiator sorted out with and without the short leaf on the front and see if one seems better
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