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Maurizio · Post by **Maurizio** » Wed May 07, 2008 11:18 pm

kevin wrote:Mats, toppic for debate here. On page fifteen I was not sure if it would make any difference which direction you put torsion bars in as I had lost the marks on my 28mm Autodelta bars. On further investigation in this area (as I wanted to make a few sets of 28mm and 33mm bars) I discovered why they work properly in only one direction ONLY
After looking up(Wikipedia) Young's modulus, Hookes Law, discolations, work hardening, yield strength and then looking at the process they make torsion bars here in SA it can be explained. Basically in order to stregthen the bars they are work hardened or scragged(term used here). This is done by loading bars through the elastic limit into the plastic limit a few times(calculated). By doing this it introduces discolations which increases the density of the material which inturn increases the yield strenth which means more stresses can be applied.(whew). As in the case of torsion the atoms on the outside of the bar are intoduced first into the plastic limit before the atoms in the centre. A curve can be drawn from the centre to the edge of the bar defining this area. As mentioned its a curve in the direction it has been work hardened in. These torsion bars are only work hardened in one direction.Therefore if you had to load the bar in the other direction it would not have the same strenght.
The only way I can test the direction of my unmaked bars is make a small jig and load them with same weight in both directions and see which direction rotates the least and that will be the direction it was work hardened.
So, if you say you got them in the wrong direction all that will be different is the loading. Unfortunately NOT as a material that has been work hardened follows a different curve back to the Youngs Modulus curve once the load has been released and effect your rebound rate which the Alfa engineers worked out.
At this stage Im not sure If mine are in the correct way but I am not taking them out to check as my cars handling is absolutely brilliant at this stage and far exceeds my driving skills.
Comments, anyone

As for this story, my comment nonsense. It doesn't matter if the load has a + or - the material get the same load, only differs from direction. So there is no difference in stiffness or strength in bound or rebound.
I even doubt a material really can be hardened by putting it through an plastic deformation. The basics of hardening is making smaller crystals in the material. Plastic deformation doesn't make smaller crystals.

Mats · Post by **Mats** » Thu May 08, 2008 3:08 am

work hardening is real, that's how you do stiff wire or nails for instance.
But it needs to go over Rp0.2 (yield) or it never happens. Call Wöhler, he will tell you.

Maurizio · Post by **Maurizio** » Thu May 08, 2008 4:38 am

Mats wrote:work hardening is real, that's how you do stiff wire or nails for instance.
But it needs to go over Rp0.2 (yield) or it never happens. Call Wöhler, he will tell you.

Yes slip of my mind, true, work hardening is real.
My comment should say: Just loading a torsion bar by putting torsion on it, will not change the stiffness. As the youngs modules wont change.
If you hammer on it (black smith) you change the density, ok that works.
And then still it won't know if it is loaded in the + or - direction.
Strength and stiffness are two completely different things.

For wohler/fatigue, enough deformations cycles are also enough, at only 30% of Rp0.2

Do you have the phone number of Wöhler? I need some info from him....Currently designing a non magnetic spring for an aggressive environment.

Mats · Post by **Mats** » Thu May 08, 2008 5:25 am

Sorry, I promised I wouldn't spread it...

kevin · Post by **kevin** » Thu May 08, 2008 7:43 am

Maurizio, thanks for those calc's. Perfect for what I need as i am setting his car up into the same proportions as my car to start off with. Its great to have rocket scientists on this forum (stops having to go dig out applied maths files from Civ.Eng 101)

Maurizio · Post by **Maurizio** » Thu May 08, 2008 12:07 pm

kevin wrote:Its great to have rocket scientists on this forum

talk to my boss, he has a complete other opinion

MD · Post by MD » Fri May 09, 2008 1:17 am

I talked to your boss, he's right..

Micke · Post by **Micke** » Fri May 09, 2008 4:11 am

You mean SHE is right (I've seen his "boss")

Maurizio · Post by **Maurizio** » Fri May 09, 2008 4:12 am

MD wrote:I talked to your boss, he's right..

he is always right as long as I get a raise

@work: Say: yes, think and do: NO! Engineers are always stubborn, only dumb and stubborn is a lethal combination.

Micke wrote:You mean SHE is right (I've seen his "boss")

A, I hear a man speaking with his own portion of life experience

Barry · Post by **Barry** » Fri May 09, 2008 9:59 am

MD wrote:I talked to your boss, he's right..

Doh!! Brilliant !!

kevin · Post by **kevin** » Sun Jun 08, 2008 12:54 pm

Spent Friday at the track(free courteous of Bridgestone) chasing a 700hp Skyline GTR on slicks around the track in the race car. The GTR's handicap was it had a women driver who could not take it around corners but would go like hell on the straights. At the end of the day I was 4/1000 of a second slower. I have never pushed my car like this before and suddenly a few gremlins have appeared. Firstly under have braking I could not down shift as it seemed to be 'stuck' in fourth. Only when I was totally off brkes and slowed down then I could select gears. This problem got worse until finally something 'gave way' in the clutch assembly. This did not happen on a gearchainge but on hard acceleration out a corner and suddenly a huge vibration developed. i backed off immediatly.The car was drivable back home 50km's but could only rev to 3000rpm until heavy vibration occured. I put the car on the ramps and inspected all couplings which are perfect but when you rev it up you can see the rear doughnut whipping about as though the clutch bearings have failed.
The box will come out tomorrow as I ran out of time attending to a mates car.
Now I have not put the drilled and bolted gearbox mounts in yet but I do have a powerflex dedion bush in. I think the exessive movement of the box under heavy braking with full race pads, big brembos and semi slicks has created this problem which has transferred unneccessary large longitudanal forces on the clutch bearings. (Mats you will tell me if im speaking crap here but need imput as well)
In most cases the clutch housing normally explodes but I have caught this one in time.
Has anyone experienced any of these problems under braking and also a resultant clutch failure ?
cheers
kevin

Post by **Zamani** » Sun Jun 08, 2008 11:46 pm

Yes, I have experienced the same issue before. Can't shift under heavy braking. Never found out the reason. A few months later, lost 4th gear. Turned out to be some catastrophic failure of the center piece (the piece which the 2 halves of the transaxle mates to which I believe holds the bearings for the shafts). But around the same time the clutch was also making funny noises.

Right now might clutch housing is making funny noises, mainly due to the bearings (not the throw out).

Mats · Post by **Mats** » Mon Jun 09, 2008 9:43 am

I guess you can jam the selector shaft if you have the old linkage and the brakes force the box nose-down. But I have never experienced that at all, always have had super smooth shifts even during rear wheel skid braking (i.e. as hard as it gets). Are your bushings alright?

Post by **Zamani** » Mon Jun 09, 2008 12:56 pm

BTW Kevin,

Does your clutch makes clanging noise regardless of whether or not the clutch pedal is depressed or not? My mechanic also said my driveshaft was "wobbly" (viewed it when my car was on the lift). I'm ordering the bearings in the clutch housing. Replacing the throwout bearing as well since I'm doing that.

kevin · Post by **kevin** » Tue Jun 10, 2008 11:52 am

Typing this while watching the slowest game of soccer from Salzburg(Mats vs Jim).
The clutch is out but the whole unit(clutch housing) is broken around yhe bearings. Before I removed the clutch we spot welded the Magnesium casing before it went totally out of position, and then stripped the unit out so it can be properly . I left the bearings in so no distortion occurs and then i will change them.
Problem number one , I have the wrong gearbox mounts in as they are from a Giulietta. I probably did not even notice as last time I put the box in was five hours before a race with little sleep. These Giulietta mounts are obviuosly smaller and also not as high. This is why my gearbox is closer to the cross member(10mm) causing that clunking sound I mentioned earlier in the thread when you back off on throttle. You can see a deep groove on clutch housing.
As Mats mentioned the excessive dipping of gearbx makes sense why i could not find gears and this is exaggerated by the smaller, softer and lower Gilulietta mounts.
Normally clutch casings burst from bad or lack of balancing in the unit at high RPM. As this car is very smooth with zero vibration up to 7000rpm Im putting my money on the mounts. Anyway my new mounts arrive tomorrow which i will drill and bolt ith Bolts machined by Barry few months back and put box back tomorrow night. Huge race coming up this weekend.
Anyone got any tips on putting a piper into breather of gearbox while its half hanging out the car before i put the clutch back. reason for this is its spilling to much and dripping onto exhaust(black flag looming). Or any other method of stopping spillage.
Thanks
(still no goal -euro 2008)