Technical Model A rear spring questions (updated with final pic)

All,
I am trying to sort through a rear suspension problem on my AV8 (30 coupe).
I did not build this car I am just working from the front to the back sorting problems in order of severity.
the current problem is that the spring shackles are at 90* at rest and the bottom of the spring is very close to the top of the hairpin mount. (see pics below of my nightmare)
The rear member is from a 51 Ford F1 and I am trying to determine what spring was used for this rear suspension and if my problem is a worn out spring, to many leaves removed, other...
I was told by the PO that a 30-31 spring was used and possibly there was a leaf or two removed.
Looking at pictures of a 30 reverse eye spring it would appear that the arch is greater than the one that is in my car.
My questions are:
How many leaves are in a stock 30 rear spring? Mine looks to have 6, maybe 7, it is still in mounted so it is hard to tell for sure.
Does anyone have a measurement of the distance between the bottom of the leaf pack and the line that runs between the reverse eyes when the spring is installed and the weight of the car is loading the spring?(see my drawing for the measurement i am looking for) mine is about 9" and the spring seems pretty "de-arched" from what a stock spring looks like out of the car.
In another thread about rear springs @HotRodWorks Said that the standard rear spring eye mounts are 49.5" apart. Mine are ~47". Posies sells a 46.5" spring but I want to make sure that I am not going to raise the rear of the car more than an inch or two using the Posies spring.
Sorry for all the questions, I suffer from Cluster Headaches so I have had plenty of time laying awake in bed to over think this stuff.
Chappy

20190222_075742 by Chappy444 posted Feb 22, 2019 at 7:58 AM

20180430_212729 by Chappy444 posted Feb 22, 2019 at 7:51 AM

20180430_214107 by Chappy444 posted Feb 22, 2019 at 7:51 AM

20180430_213123 by Chappy444 posted Feb 22, 2019 at 7:51 AM

20180603_114501 by Chappy444 posted Feb 22, 2019 at 7:51 AM

 

Ask at the fordbarn.com web site or the earlyfordv8.org web site. I sure someone there can help you out.

 

I'm not clear as to what exactly the problems are. You've not for instance said it rides like crap.

Problem 1. Shackle is near vertical - is that a problem in itself as it's not at the ubiquitous 45 degrees?. Does the spring actually hit the spring perch? If not is there really a problem? There are some that don't necessarily subscribe to the 45 degree deal, so that's arguably not a problem. If there is interference a shorter spring would fix it. Or maybe some careful and not excessive clearancing of the spring perch.
Problem 2. Spring is close to the hairpin. Do they actually meet? If not again is there really a problem? If they make contact, hhmmm.

Assuming the spring is in useable condition and seeing as you have plenty of room toward the brake backing plate, I think revised spring perches giving clearance for the shackles and a little lift to clear the hairpins would be the easiest fix. two birds, one stone. Simple fabrication.

Sorry, I don't know the answers to your exact questions!


Chris

 

Hey Chappy
your perches on the axle are likely to close together to get the spring to stretch.
the perches where the shackle goes thru should be close enough to the wheel cylinder
to make it a headach to get at them LOL, See the house of fab mount for this set up .
I believe whatever the measurement between the perches is , the spring should be 5 inches shorter
uninstalled .

 

How much space between the bottom of the spring and that hairpin mount?

If there is a few inches of clearance before the axle hits the spring, I'd just have a local spring shop make a new main leaf that's about 4 inches shorter. If there is only an inch or so, you are likely to need the hairpin mounts modified. That being the case I'd also make new mounts for the spring at the same time and then you could probably keep the existing spring.

 

Actually, looking again at your first pic (not the diagram) in full screen it looks like it's possible that the spring eye is solid up against the spring mount already.

Chris

 

Chris,
Yes it rides like crap,
yes the shackle hits the perch
yes the spring is too close to the hairpin mount (about 1") and shows evidence of contact.

i am assuming the spring is not in useable condition as it may be 90 years old, or modified, or to long, or... (that is why i was asking the question about measurements, etc.)

ripping the rear out of the car, cutting off the spring perches, cutting new perches, and welding them back in may be simple fab for some folks, (BTW would i need to pull the wheel bearings and seals out of the rear before i go welding that close to them? will all that heat mess them up?) but for me, in my one car garage with a 115v mig welder and not trusting my life to my welding abilities... this becomes more than simple fabrication.....

i was hoping that getting a new, shorter spring, like the Posies 46.5" perch center reverse eye spring would solve this problem without having to do a bunch of fab work. There is a new rear in my future plans for this car but unless someone is giving away QCs today I have to work with what I have and within my budget for now.

thanks for the input.
Chappy

 

There is nothing wrong with that set-up that a complete redesign wouldn't cure.

One thing I saw in the first photo is that the frame lip over the spring appears to have been bent up for clearance. Also, it appears to have a couple of rust lines on it where the spring may have been hitting.

Here is what I would suggest for very little cash outlay. (1) Take something marked with the length of the shackle (center to center) and hold it at 45* from the shackle top pivot point and measure how much shorter the spring would have to be to fit that. Then take the spring to a local spring shop and have them roll new eyes on it at the new length. Advantage here is that your mainleaf fits the arch of all the other leafs and you are dealing with it in its loaded state. You may have to shorten other leafs also.
(2)Buy longer "U" bolts and and make spacers to go between the spring and frame and to go between the frame and spring clamp. This will give you more clearance between the hairpin mounts and the spring and the ends of the spring and the frame. You said you could live with an inch of change in ride height but I would start at 1/2 inch but buy "U"bolts that would accommodate 1 inch.

Edit: Upon further review the spacers won't gain any more clearance over the hairpin mounts. Though changing the angle of the shackles may gain a few fractions.

 

are you saying that the distance between the spring eyes is the same when the spring is installed in the car with the load applied as when it is out of the car with no load applied?

couldn't i just jack up the center of the frame at the back until the shackles are at 45* then measure and buy a spring that has that installed measurement?

Which brings me back to the posies spring... the catalog has a description as follows...
Narrow Width Model A Spring - 46-1/2" Perch Centers Part# 29-31R-C SuperSlide Rear Spring – Lowered Reverse Eyes
my perch centers are at ~47" i would have to assume that Posies would have engineered the 45* shackle angle into the spring width if they are quoting spring perch width measurements.
Chappy

 

No, a semi-elliptical spring gets longer with a load applied.

I don't see why that wouldn't work. My suggestion was a way to measure how much length to remove if you were going to shorten the spring that is in there now. (A spring with a known ride height.) The spacers were a way to gain additional clearance from the spring to the frame.

Rather than make an assumption I would make a phone call to Posies. I would also ask how tall the spring is from the eye centers to the top of the spring center when installed to compare to what exists now to get an approximation of any change in ride height.

 

You have several symptoms of problems there
Find a solution that corrects them all
The spring hitting the radius rod brackets will be next

 

Your main leaf is too long, I would go to a spring shop and have them shorten the main leaf to your desired dimensions.

 

Measure perch hole to perch hole
Subtract 5 inches and that is the spring length you need . Reversing the eyes will put the spring closer to your hairpin bracket .
The perch brackets sold here will also just bolt on . Just sawzall the old brackets for now .
I suspect getting the spring mounted properly will also cure your hairpin problem

 

Not sure how much help this might be but here's some measurements off my 32 coupe project that's a nearly complete car.

It has a SoCal Model A rear spring - they're 8 leaf, 2 1/4" wide, and SoCal say they're narrowed 3". Bit difficult to get precise measurements easily as there's a Champ qc in the way! So as best as I can see my perches are 44" apart, the fully loaded spring eyes are 42 1/2" apart (they're not 45 degrees but not vertical either) and the centreline of the spring eye to the top of the crossmember is 12". Given that the SoCal and Posies springs are, I'd expect, rather similar, that spring height over the centreline might be of some relevance to your questions?

My setup has yet to see the road but with my 250+ bouncing right on it it has a good feel to it. It's sat like that for quite some time now but I expect some settlement once the spring has been in proper service for a while.

Chris

 

Thanks everyone for the help.
My spring peach center are 47" apart
When I lift the body untill the shackles are at about 45*, the spring attachment ends of the shackles are 45.75" apart.
One last question.....
Has anyone ever successfully replaced the rear leaf spring with the rear end still mounted in the car? I have access to the top via removable trunk floor...but dont know if I will have enough room to disassemble/reassemble spring pack.
Thanks
Chappy

 

For hairpin clearance, buying a non-reverse eye spring would increase that distance at the cost of a ride height increase equal to the diameter of the eye. That would also put the outer end of the spring closer to the frame.

 

Well, I pulled the rear today and it is a 10 spring pack!
Below is a pic of the shackle angle out of the car. Seems like 10 leaves shouldn't settle as much as this one did.
This is my first model A so I am not sure what it should look like out of the car.
Thoughts???
Thanks
Chappy
Out of the car...

In the car...

 

Another update,
I was getting ready to take the spring pack apart so I could remove the last leaf from the shackles and I lifted up on the spring pack and both ends of the spring moved up and down. In other words it is at "rest" and there is play in the shackles.
I thought the main leaf had to be "stretched" on to the shackles?
Am I missing something here?
Thanks
Chappy

 

Chappy, looks like your new main leaf is too long. Yes, all ford buggy springs should have a preload on them.

 

a 'SPRING PERCH' could now be welded in there, onto the rear crossmember, placing the 'A' spring 4" behind the crossmember. Perches welded onto the rear of the housing would locate the spring away from the rear hairpin brackets. (behind them)
A 10 leaf spring may have been from a 4 door sedan or a pickup. Roadsters had 5 or 6, Coupes 8, I believe. If you take this course of action, DO remove axles and seals from the housing; brackets are available from various sources, but they may vary in length...they can be trimmed to fit. 4" rearward is what I'd shoot for, to avoid an excessively long perch off the crossmember. (gussets are highly recommended)
Model A spring characteristics differ from the desired 'T' springs: The angle of the 'A' differs from the relatively 'flat' 'T'. The 'T' doesn't stretch out 'incalculably' when weight is applied.
Spring out back will also soften the ride...That's why Henry moved them from '32 to '48...

 

I would visit the local spring shop armed with the measurement eye to eye of your spring perch's and an approximate sprung and unsprung weight. For less than 300 dollars all new springs that work great!

 

Get the house of havlier perches, they are also a bolt on item . Remove the 2 top bolts from the backing plates , get longer bolts and bolt them on .Sawzall the existing perches close to the axle , Your spring appears to be a standard length spring . This I am sure will solve your problem of spring length and clear your hairpin mounts . No matter what you do I would at least get the perches where they belong .

 

Have you noticed the previous posts about your spring perch center to center dimension being too narrow?

Who ever put it together did not understand what they were doing

 

X2 on the axle perches too close. Consider the bolt on perches mentioned above or cut the perches off of a model A rear axle, saving the top bolt holes and bolt them on to widen the gap.
My coupster started off with a 10 leaf pack from a sedan. Using lots of clamps and scaredyness, I disassembled the pack and removed every other leaf above the main and leaf directly above it to get it down to 6 or 7total. Then cut out the center 7 or 8" of the discarded leaves to add to the pack above or below the pack to adjust ride height and take up the room between the bottom of the rear x-member and the bottom spring clamps. Sedan and coupe spring clamps have different depth "protrusions" to bear on the bottom of the spring pack to tighten it firmly to the x-mem. May take a time or two to get the springiness you want and correct ride height.

 

Thanks, I checked the Havlier website and didn't see a set of bolt on's for my 51 F1 rear, I will give them a call and see what's available.
But there is a lot going on around those top two backing plate bolts
Chappy

 

Yep, I saw those post about the perches being to close together... obviously it wasn't put together correctly, that's why it is in pieces on my garage floor.

There are many options that have been discussed here to correct this issue, including
1. Move the spring 4" to the rear of the x-member (this would require shock relocation)
2. Cut perches off and weld on new ones
3. Cut perches off and bolt on new ones
4. Rip it all out and start over.
5. Guestimate the needed length and have my main leaf shortened
6. Get a readily available shorter spring that fits what I have.

I would love put a QC under it but with 2 kids in college that's not going to happen in the next couple of years (unless you know someone giving them away).

My welding skills are fair, but... not sure I trust myself on suspension parts...

So, the bolt on perches are an option and the shorter posies spring is an option.

I really do appreciate all the feedback and grateful for the help.
Chappy

 

Chappy.

The bolt on brackets referenced will only work with the banjo rear. It looks like your using a Dana 41 rear out of an f-1? You will need to use brackets that weld to the housing.
I’m the guy who started the original thread about my leaf binding up. For anyone stumbling upon this thread, I ended up going to millworks for the brackets and a new reverse eye main leaf.

If it were mine I would try a new shorter main leaf. If you can nail the length I bet you can re-use the setup you have.

 

Pete & Jake's sells a different style weld on rear spring mount that will let you move them further apart on your rear axle. This may be a solution to your shackle angle issue, though I don't know whether it will solve your clearance issue with your radius rod brackets.

Sent from my SM-A600A using The H.A.M.B. mobile app

 

Chappy said he's swapping a different rear end in sometime in the future, but not now. He also said he is not trusting his welding and is looking for advice.

with those two things in mind, what is the hamb feedback on this idea below?

^^^ First is to get a shorter main leaf so he can keep the welded shackle brackets as they are, and get the shackles to 45 degrees.

Next issue is the "too tall" upper trailing arm bar & clevis. How about cutting that existing top bracket down, relocate the hole for the clevis, then bend the upper bar down at the "X"? ..(which is directly behind the mid-point reinforcement spreader plate between the upper & lower bars)

Lastly is remove the excessive leaves to get a better ride, then use "cut" center pieces of those leaves up at the top of the spring pack as spacers, so the ride height is not lowered ?

Is this the easiest way out without turning this issue into a huge depressing project?, ...or am I missing something in all the pics so far?

.

 

I agree with F&J.