rear suspension leaf spring

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georges2
Posts: 193
Joined: 26 Dec 2008, 20:46

rear suspension leaf spring

Unread post by georges2 »

Hi everybody
I am working on rear suspension of my S1 Fulvla coupé, to replace all rubber parts and silents blocs by new ones
Please see attached pictures and specially parts n° 5 rear setting point of leaf spring
I suppose the upper bolt must not bee very much torqued as it should move a little
but for the lower, I would be pleased to know the correct torque setting, and if it is necessary to load the car during processing ?
Any experience or advice will be appreciated
Best regards
Georges2
Attachments
schema jumelles ressort arrière
schema jumelles ressort arrière
jumelles et axes schéma.JPG (17.1 KiB) Viewed 2714 times
photo jumelles
photo jumelles
Huib
Site Admin
Posts: 1778
Joined: 17 Dec 2008, 10:12

Re: rear suspension leaf spring

Unread post by Huib »

Very good question, Georges2. I am now typing from my phone already in bed. I will look up the data one of the next days. Don't do anything wrong in the meantime.

One question. Is the shackle block (the trapezium rubber) new or is it the original? If it is new can you compare the weight with the original one?
georges2
Posts: 193
Joined: 26 Dec 2008, 20:46

Re: rear suspension leaf spring

Unread post by georges2 »

Hi Huib, nice to you to answer at any time....
one of the old rubbers is 217 grams, the new one in only 175 g....economy ?
I will do nothing until next week as the other parts (leaf spring and reaction bar and link bar are in a garage shpo so st new silent-blocs in place
So I am quietly waiting for your instructions
I remember to have red on this forum (long ago) an advert from you about the way to fix correctly the different parts. No attention at this time, and I could not understand ..... If my memory is not wrong, you explained that "Tina" should have so sit in the boot before you turn the bolts....I am afraid I will not use this way, as my wife will just answer "this will not be helpfull, I am so light, as you know, dear..."

I hope you have a quiet night, and many thanks to you
georges2
Huib
Site Admin
Posts: 1778
Joined: 17 Dec 2008, 10:12

Re: rear suspension leaf spring

Unread post by Huib »

Keep in mind that twisting the rubber does the hinge action in case silent blocs are used. A silent bloc consists of two steel bushes, one large, one small with rubber in between. There are two qualities. Alfa Romeo quality where the rubber is just pressed in between the bushes. Lancia quality where the rubber in between the bushes is galvanized to the bushes.

The rubber can only be twisted over a small angle because rubber has limited elasticity. If the maximum twist angle is exceed the rubber will tear. If the rubber is twisted many times near the maximum it will degrade. If I have no specifications of the silent bloc, I assume a maximum twist angle of plus 15 degrees and minus 15 degrees.

The rule of thumb is that the bolts are torqued at half swing of the rubber. In other words the static position is when the connected parts are at half way between minimum and maximum travel. That is the position in which the bolts are torqued. The Fulvia DT 07/100 shows in what position the springs should be when torqueing the bolts. It says the distance between bump stop and the plate on top of the rear axle should be 8 cm. I use an M8 x 75 bolt. If it just fits between the bump stop and the axle it is okay. Do however always double check if the position is really at or near half way travel. The DT does not make a difference between S1, S2 and Fanalone (which has a bump stop that is 5 cm longer).

Always look at the situation, visualize the movement and fasten at the centre position. If you have more experience and never fell a sleep during the lectures on mechanical engineering you might measure total swing and if less then 30 degrees, off set the centre a bit if the swing will be more to one side than to the other.

On the Fulvia the maximum down travel of the springs is determined by the shock absorbers. Never remove the shock absorbers without making sure that the resulting extra down travel of the spring exceeds the maximum twist of the silent blocs. The limit for the up travel is determined by the rubber bump stops. Sometimes cars come into my workshop without the rubber bump stops. Don't drive a Fulvia without the rubber bump stops. The silent blocs may tear. Shock absorbers may bottom and destroy themselves. You can no longer drive if the spring is broken.

All bolts should be torques as in the DT 07/0010, 2 pages. Both the inner bush and the outer bush of the silent blocs have to be locked into place very securely. The movement has to come from the rubber only. Bolts are never to be used as spindle / shaft nor should they be loaded radially. Never. Never. Never. Bolts are uses to clamp two surfaces together. The friction between the surfaces should then take care of the shear force.

The rear swing of the Fulvia rear springs is a complex thing. If you load the boot till you have the 8 cm between buffer and spring the spring is flat thus at maximum length. It means the swing is pointing to the rear. It is not hanging straight down at 90 degrees from the shackle block. So here the position of the shackle is at maximum swing when the car is brought into the position that the books specifies for torqueing the bolts. Now, the question is did Lancia forget to specify the proper position of the swing for torqueing or is there a secret?

The secret may be in the 42 grams difference in weight between the original shackle block and the imitation shackle block. The inner bush of the original shackle block has 4 steel fins welded to it. It sort of looks like the tail end of a small rocket. The fins point to the corners of the block. The inner bush with fins is still vulcanized to the rubber. It is thus much better anchored in the rubber than the bush of the imitation blocks. Since there is more rubber, it may be able to twist more than 30 degrees left and30 degrees right. I am at loss here. My feeling says we should not abandon the law that it should be in the centre position when torqueing which is more or less straight down. If somebody has a different opinion I would like to hear that. If someone knows where I can get the blocks with the fins like the original I would like to hear that too.

The movement of the swing at its bottom end is even more complex. If someone can simulate that movement with a computer program and calculate the centre position I would be happy indeed.

Yes. Good old times with Lucas (well over 100 kg) and me (then just under 100 kg) in the boot smoking cigars and drinking Prosecco while Claire (48 kg) crawled under the car to torque the bolts. Was that 10 years ago. Or 12 perhaps? Anyway, Claire is doing well today, already at 52 kg. She is my (104 kg) boxing trainer. Fortunately for old times sake she does not take me seriously. I don’t see how we get her over those 52 kilo’s. Best regards from Claire for everyone.

Wainer Mariuzzo, my colleague, born in Turin and trained by Lancia now just loads cylinder blocks in the boot until the spring is in the right position. If the sills of your car are all right it helps to put axle stands under the front cross member of the subframe. A larger part of the car is now weight and no part counterweight.
georges2
Posts: 193
Joined: 26 Dec 2008, 20:46

Re: rear suspension leaf spring

Unread post by georges2 »

What a wonderfull word....
How one (like me) could imagine the technology hidden in an old rubber part, even trapezial ? some people speak about "intelligent cars", I stay confident with my Fulvia created by intelligent engineers (and driven by responsible drivers too)
Now, after hours to translate correctly all informations (thanks to writer sharing knowledge and english language, Brexit or not) I can understand what I have to do :
1) place all parts in place without torking bolts => then the 4 wheels are back on the groud
2) load the boot until the distance between bump stop and the plate on top of the rear axle is 7.5 /8 cm; the average line of the leaf spring should be nearly horizontal. To load the boot, as the is no rugby players in my neighborhood, I think to use water bottles sold by paks of 6 (1 pack gives 9 kg and the boot can contain 10 to 15 packs, I will check the result of this test)
3) checking the 8cm distance on each side, I will then torque all bolts (I have read 2.5 mkg on the technical data book)
4) if the result is OK, drink some water...and may be St Emilion too.
to be continued in one or two weeks.
Great thanks; Georges2
georges2
Posts: 193
Joined: 26 Dec 2008, 20:46

rear suspension damper

Unread post by georges2 »

Next question (and mystery ?)
It is strange that the lower axle of the rear shock absorbers are not "in the main axle") of this part.
Why ? is it more efficient ?
Huib
Site Admin
Posts: 1778
Joined: 17 Dec 2008, 10:12

Re: rear suspension leaf spring

Unread post by Huib »

Attends mon ami. Pas si vite. Pas sur les roues. Sorry. Relax. Take it easy. Not on the wheels but on axle stands as you also have to torque the 4 M10 bolts (on each side) fastening the rear axle to the springs, the bolts of the drop links of the anti roll bar, the bolts or rather brackets at the front of the rear springs, the bolts of the Panhard rod, shocks.

May I suggest to load the boot with boxes of St Emilion and Pomerol? With a few bottles of Nebbiolo to remind the French what a good wine should taste like. No insult intended. Just a friendly advice.

Votre message sur les amortisseurs: do you mean why the mounting eye is off center? On the ones I have seen it was to avoid that the shock hits the rear axle.
georges2
Posts: 193
Joined: 26 Dec 2008, 20:46

Re: rear suspension leaf spring

Unread post by georges2 »

Hello again;
I have plenty of things to do every day, only the night to think of the car..
Well, the car is actually sitting on her 2 front wheels, and on 2 "chandelles" (french word for a kind of vertical iron tube welded on a triangular base, that means safety for car an man; chandelles just at the place for the jack near the rear wheel
My plan is to set all things in place : stabilisation bar with the links and plates, and bring the rear axle under the leaf springs by using 2 jacks
When the springs are in place at each end, they are hanging free weight except the axle
Now to set the correct distance between the spring and the schock rubber, (80 mm before torquing bolts at silent-blocs) why not use two jacks (left and right) to lift the axle gently ? Lifting the axle will make "load" on the springs, and the car body should make "resistance", so it seems there is no need to place load in the boot ?
Note that I am not an expert, I just try to understand what I do and why so so...
Here a picture of a booklet "documentation technique d'atelier modèles Fulvia" in french, but do not explain how to do.
I will not work on the car before middle of next week
Attachments
susp ARR réglages lames ressort.JPG
bmarler
Posts: 110
Joined: 22 Dec 2008, 17:33

Re: rear suspension leaf spring

Unread post by bmarler »

the car body will provide resistance, but not enough. you will simply lift the car off the stands. you still need to load the boot with enough weight to keep the car on the stands and get the axle in the proper position. having the car on stands is an advantage though, then you have room to slip underneath and tighten everything up.
Huib
Site Admin
Posts: 1778
Joined: 17 Dec 2008, 10:12

Re: rear suspension leaf spring

Unread post by Huib »

As bmarler says. The springs are designed to carry the car.

Put axle stands (chandelles) under the axle and put weight weight and weigh in the boot.
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