When setting up your bastardized suspension of a Henry collection of parts... I am wondering if the shackles will go past running vertical at full travel or bottomed out? My 36 and later front spring if compressed until the shackles were straight up and down to reach the 41.750" spread of the shackle mounts will have only compressed 1.5" from it un-tensioned position off the car. Out of the car the stack has a center to center with of 38.5 plus 3" for the combined shackle plates 41.5". My mounts are again at 41.750" the .250" is to tension the spring. I'm lost here?
You need a model t spring with a.quick change to solve your problem. I will be home early from work today and I will do some measurements for you. I will see if I can help solve this issue with Hubba Hubba.
Or what's a typical amount the spring will be too short before you stretch of compress it to fit in the shackles and axle assembly?
I just guess. Make it all fit together without weight, tack it and try it. Throw a five gallon bucket of water and a fat guy(me) in for weight and then see how the shackles look. Not very scientific but it works.
There is no science to it. No way to know exactly how it's going to work because everybody's hot rod will have different parts. Even if you have parts from the exact same car/applications, their use (abuse) may have settled the spring more than the other. You just need to guess and be ready to make adjustments. Start by measuring the stock car the spring came out of, with all the weight on it. Get the spring eye width, the hanger width, the height of the spring, and the weight of that end of the car. If you are going to adjust/change any of those measurements on your use of that spring pack, be ready to make adjustments.
When I started this path I was expecting the 36+ front spring with is reversed eyes, 3" shorter than the stock rear, it's clearly softer than the stock 34 rear spring, and the 46 axles shackles position being at least 2" lower than the 34 axle to give me about 6" lower in the rear. I thought this was alright and in the right direction for my 40s build. Now it looks like if I even had the cliche 36 rear bones where the shackle is lower than the axle, it still wouldn't be enough to get my set up sitting where I want it. Guess I was post to have flattened the rear crossmember too. I actually thought if I did this in advance it would be to low with this "40 front" style spring.
I think you are mixing 2 distinct concepts. The first is the shackle angle which is determined by the length of the main leaf of the spring in relation to the spread of the shackle mounts. The constant is the shackle angle which should be 45 degrees. This allows the shackles to swing outboard as the the spring deflects without binding. The second is the ride height which is the way the car sits and is determined by many factors but in your case (transverse rear spring) the arch of the spring and the mount position as determined by the the rear cross-member. The shackle angle you have is incorrect but can be corrected by a shorter spring main leaf (either changing main leaf or have yours shortened by local spring shop). 45 degree shackle angle requires a 3 inch shorter main leaf and will also lower your car 3/4 of an inch. By the way, what are you building? More information would help in determining the best way to design your setup.
I don't have a shackle angle problem. Everyone knows that 45 degrees is the desired assembled loaded on the ground angle. I will be positioning my mounts at a spot that put the shackles at horizontal installed to the axle assembly with no weight on the spring. What I wanted to know was first what is a normal amount of stretch to install your spring? And if moving through the suspension travel will the spring compress enough to push the shackles out past vertical. I'm just trying to make proper calculations to minimize a improper installation. It seems to me that amount of stretch or tension you have in a transverse spring is going to effect its preload and and obviously it's remaining travel ability or let's say stroke. This "tension" combined with the spring assemblies weight rating or spec will effect your ability to end up at the magic said 45 degree angle with the vehicle loaded and at ride height. Another thing that concerns me is how much do you want to stay away from your spring compressing flat or can it even go negative of horizontal? This is of course if the ride isn't too soft I suppose. I'm trying to build my 32 ford chassis to have a remaining 3-3.5" of stroke after the achieved ride height and proper rake. I have no clue what is a common amount of stroke from say the axle assembly hanging, maybe from jacking the frame up or in laymen's terms "jumping railroad tracks?). This I'm sure varies with each different combination. I mean I don't know if it's 6", 9, 11, or whatever inches of rear suspension movement from unloaded to bottomed out.
just my opinion, you'd have to remove a whole bunch of leaves, before the spring could compress to flat, in normal road conditions. Dropped from 10 feet, yes it would, but axle tubes hitting the C notch would prevent it I'm not a pro builder, and I know what you are dealing with on your 32 chassis. I went through the same 32 learning curve, the hard way.(full fender steel car) I did start out with a bare stock frame, stock rear crossmember, 35 arms grafted to a real wishbone with ball. I used a 2x4 across the back of frame, made all thread J hooks to the spring ends to try to see where the heck I was. It helped, but I know I later had to move the brackets on the rear axle tubes, because...you guessed it...the shackle angle was wrong. All the while I assumed I had a 40 front spring, as I know I never had a 40 rear....but my measures now, make me think it is a 40 rear? good grief my feeling is that if a shop builds the same chassis from same pieces, for the same repro roadster body, then he can get a formula that is copied. we are using whatever used F or R spring we have, and want different ride height requirements, different body weights... what I can say for sure, my son and I spent so much time adding/subtracting different leaves, then roadtesting on our demo course, then getting a soft shock as to not mess up the nice ride...it was worth the trial/error. it rides nice
Some others need to chime in, but I can't see that system as anything to rely on. I suppose, it could be worked with, if you then had to re-arc, or de-arc to get the height you want, get a good ride, etc by the way...your definition of that front spring varies from 36+ to other times as a 40 style front. They certainly are totally different springs. 35 and 36 are same, 37 is different length.
Why are you using the front spring (of unspecified origin) instead of the 34 rear spring you have or had? Often a front spring is stiffer because weight distribution is usually heavier in the front. You have the proper crossmember, spring that matches it and has the correct spring rate for your application. Also you have the correct shackle attaching point spread on the 34 rear to transfer to your later rear.
My 46 axle has(HAD) straight shackle mounts. My spring was pretty tired as my rust belt 34 Tudor was just about dust. The front spring of the same car had multiple broken leaves. I am trying to get the lower for a lakes stance. 32-34 springs are a fortune. Yes I know they tend to be stiffer. There is always removing leaves and spacing to get that stance. My springs are brand new Posies style sliders that I will be hiding with Gaffers tape for that period look. As far as proper spring rate is concerned... Stock tend to be very stiff if they are not clapped out. My car will be very bare bones. Here is the full pack in the back now and another pic with just two to test shackle angle. Here is what I'm building if anyone is foolish enough to not fallow my thread
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