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Author Topic: Rear spring  (Read 7985 times)
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davidwheeler
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« Reply #30 on: 13 November, 2016, 02:10:11 PM »

Unfortunately one of my torsion bars is immovably fixed in the swinging arm - even 10 tonnes failed to shift it!      I will start from about 30 degrees and see how it goes from there!
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
ben
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« Reply #31 on: 14 November, 2016, 11:11:38 PM »

Hi David
             I think 30 degrees will give a very high ride height.
             On my car the trailing arms are about 10 degrees below the horizontal when the car is static with no weight in it.

             With one torsion bar stuck as you describe (probably a whack with a big hammer is more likely to shift it than a steady load in a press---or both!--but you will have tried this I expect) you do not have the luxury of the vernier type of adjustment on that side. This normally allows setting to within 1 degree because the inner spline has 42 teeth and the outer one has 48 teeth.

             1 degree of rotation of the trailing arm alters the setting height by about 4mm.

             Your best bet will be to fit the stuck bar first which presumably will go back the way it was before you took it to bits so should be ok even though moving only the inner spline changes the angle by about 8.5 degrees for one tooth. You can then measure the height on that side and set the other side to the same dimension.
             It will be easiest to do this height setting process without the transverse leaf being installed.Whether this is possible depends on the design of your spring compressor. If you have to do it with the spring in situ it requires manipulation of jacks under the body and under the wheel hubs to achieve the correct height setting and probably some extra weight in the boot will be needed.Either way the objective is to manipulate the radius arm angle to achieve the 155mm setting dimension (or whatever figure you are stuck with from side one) and then rotate the torsion bar until you find the position where it slides in with minimum alteration of the swing arm angle being required.  I think this "zero stress" position for the torsion bar should correspond to a typically loaded car.
           As Noel has pointed out working with the transverse spring in place you can judge if the ride height looks ok directly without worrying too much about the 155mm setting dimension.

Ben   
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BlueSky
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« Reply #32 on: 15 November, 2016, 03:17:55 AM »

I'm glad Ben has come up with proper technical explanation. I would have thought you could get the siezed torsion bar to move with a generous soak in penetrating oil and gentle heat repeated over a few days before the big hammer treatment!
Noel
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davidwheeler
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« Reply #33 on: 15 November, 2016, 09:45:23 AM »

Ben has just clarified on the phone that the trailing arm height is set without the spring attatched.   Posted in technical information thread.
The torsion bar bearings arrived from Ferriadelio yesterday in disintegrating vintage brown cardboard packets but immaculate inside their anti-rust paper (and very securely packed).
« Last Edit: 15 November, 2016, 09:52:20 AM by davidwheeler » Logged

David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #34 on: 08 December, 2016, 04:34:55 PM »

We are making progress at last.   Yes, several days of oil, spread the slot with a cold chisel and a heavy hammer and the splines relented and the torsion bar came out.     After much cleaning and painting and general tarting up I am now re-assembling.    I set the trailing arms to the prescribed height and the torsion bars went straight in on both sides so I am not sure about Ben's vernier effect - perhaps they are set right at the factory and it is just a case of getting things in the right position.    I am not using the original final drive so the inner splines must be set in the right place to start with as standard.      I have assembled one good spring from two and cleaned the rust off the leaves and applied much transmission grease.  When I have fitted it to the car I shall wrap it up with duct tape.   I fitted the new trailing arm bearings and packed them with unfeasably thick grease as the original seals got carbonised in the removing of the old ones and I shall then wrap greasy string round the shafts on both sides.   With any luck, it will not need to be disturbed for another 70 years.   All I have to do now is make new spring end shafts and repair the brackets that take the shock absorbers - the holes have got a bit enlarged over the years.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
simonandjuliet
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« Reply #35 on: 08 December, 2016, 04:53:43 PM »

Great progress - I have had problems with the torsion bar in the past as well. Any photos ?

May be able to help with the shock absorber mountings if you get stuck
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davidwheeler
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« Reply #36 on: 08 December, 2016, 06:28:02 PM »

Well, it is pretty well all up together so photos would not be very revealing!    The mountings just need a bit of welding so thanks but no thanks.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #37 on: 09 December, 2016, 06:14:51 PM »

Have made two new spindles for the spring ends having realised that I do not need the shock absorber brackets as I have side mounted (adjustable) shock absorbers.    Have applied the spring compressor and tightened it up ready for the morning - I think 5pm is too late to start re-attatching the spring and removing the compressor, it needs a clear morning head.


* IMG_0187 (Copy).JPG (351.33 KB, 1400x1050 - viewed 184 times.)

* IMG_0189 (Copy).JPG (360.11 KB, 1400x1050 - viewed 168 times.)
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
JohnMillham
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« Reply #38 on: 09 December, 2016, 08:15:54 PM »

Have made two new spindles for the spring ends having realised that I do not need the shock absorber brackets as I have side mounted (adjustable) shock absorbers.    Have applied the spring compressor and tightened it up ready for the morning - I think 5pm is too late to start re-attatching the spring and removing the compressor, it needs a clear morning head.
. I wouldn't stand in line with it! There's an enormous amount of energy waiting to get you!

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davidwheeler
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« Reply #39 on: 10 December, 2016, 05:38:30 PM »

True enough John but it is all up together again...  I did up the compressor even tighter, the channel section bent gently and I still had to use the coil spring compressor to approximate the trailing arm and cable mounting but nothing went spang.     She is now back on her wheels, level and ready to go but test drive will be tomorrow in daylight.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #40 on: 11 December, 2016, 03:52:03 PM »

Brief spin round the block.  The "new" cwp is silent and the clonks have gone so I must have done something right.    Seems as swift as ever, too, despite the higher gearing.   The Nardi bits help of course.  Must now try to calibrate the speedo.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
ben
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« Reply #41 on: 12 December, 2016, 05:23:40 PM »

Well done.

I should probably rebuild my diff as it has too much backlash and has been leaking for the past 40 years or so but the oil is keeping the spring nicely lubricated!

You mentioned that the torsion bars went straight in on both sides.That is exactly what should happen but usually to achieve it requires rotating the bars to find the position where this is possible without moving the trailing arm from its set position.

If the shafts had the same number of splines at both ends it might be necessary to move the trailing arm to get the splines to line up (by up to as much as half a spline in the worst case) but with the vernier system provided by having different numbers of spline teeth at either end the shaft can be rotated to a position where the splines will line up at both ends with negligible re-positioning of the trailing arm.
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davidwheeler
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« Reply #42 on: 21 December, 2016, 10:11:08 AM »

I hear what you say but the fact remains that I did not have to do any rotation, it would be highly unlikely that I would choose just the right position on both sides by chance?    Too late now to count the number of splines - has anyone got a shaft out to enlighten us?    In the meantime I have been flying around in my refurbished car.  The higher gearing means that I am going even more too fast!    At least the speedo now registers the correct speed.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
ColinMarr
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« Reply #43 on: 21 December, 2016, 12:37:36 PM »

I can assure you that possibility of vernier adjustment is real - there are unequal number of splines between inner and outer ends. As I posted at almost the start of this thread:

"The car needs to be levelled up and the torsion bars inserted (vernier adjustment) so that they are unstressed and 'neutral'. Not that I have ever seen one, but originally there would have been marker plates inside each rear wing cavity to help with this, as in the attached photo. In practice, I think the best thing is to set it up so the transverse spring looks flat and then insert the bars. What fun!"
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ben
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« Reply #44 on: 21 December, 2016, 06:23:20 PM »

A shaft I have to hand has 42 splines on the inner end and 48 splines on the outer end.

Because these numbers are both factors of six I think it means that there will be six equi-spaced positions where the shafts should just slide in.

This in turn means when the shafts are offered up they are bound to be within +/- three splines of optimum and only a very small movement of the trailing arm is required to enable them to slide in without any rotation of the shaft.

At the risk of upsetting the purists I think this is another (not uncommon!) example of Lancia over-engineering. Or it may just be a by-product of a design decision to make the inner spline smaller than the outer so that the shaft can be fed through more easily on assembly.
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