Suspension Parts List

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Midlana1
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Re: Suspension Parts List

Post by Midlana1 » 19 Aug 2019, 07:40

The orientation of the forward spherical bearing is dictated by the rear upright. Where to place the retaining clip groove is discussed below:

Forces are trying to pop the ball out of its socket, hence it being oversized. The bearing - and the clip - see forces under acceleration or braking. I'm not sure which force would be higher, but imagine that side-stepping the clutch would be worse than locking up the brakes, so that argues for having the clip on the backside. Then there's corrosion; in theory, having the clip facing aft helps protect it from rock impacts and splashed water, but that benefit seems doubtful in reality.

Since there are two, the force on the retaining clip is roughly one half maximum acceleration or deceleration. If we round up and say that a fully-loaded car is 2000 lbs for easy math, then each clip sees 1000 lbs of force at 1G acceleration or deceleration. The problem is hitting a pothole, and how much higher the force might be is speculation, but it drives home the point of the importance of ensuring that the clips are both in good condition and fully seated.

Trying to avoid loading the clip has its own demons. A clevis pin arrangement through the bottom of the upright would change the forward bearing axis to vertical, which is a good thing because it no longer uses the clip under load. The problem though is that it also move to forward pivot further away from the upright, meaning that the forward end of the pin flexes under cornering. Worse, a fabricated clevis pin would probably be a welded assembly, and a welded joint in bending will eventually fatigue fail along the heat-affected zone.

Back to the design as presented. Failure of the clip would allow the spherical bearing to come out of its cup. If the retaining ring is on the forward (chassis) side and fails, the bearing could move forward a small distance, but the upright would hit the housing, keeping it captive. That said, even that small shift would result in sudden and unexpected rear toe change. If the clip is on the rear side and failed, the bearing could pull entirely out of its bearing cup and allow the upright to move aft under braking. This argues for having the clip on the forward side, which also has the advantage of making inspections easier, something that we will all need to keep an eye on.

The above almost argues for permanently retaining the bearing, with the understanding that it, being as large as it is, will likely outlive the car. For that reason, epoxying the bearing in (keeping it away from the bearing surface!), or maybe adding several bumps of weld at the retaining clip, might be a defendable modification. If the lower arm get bent, a new one will be needed, and installing a new bearing at that time might be a good idea anyway. Something to think about.

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Re: Suspension Parts List

Post by aces » 23 May 2020, 02:45

In the process of developing a suspension list, use Stevo's list as a template.
Since the Swedish inspection agencies have some recommendations on the size / weight of a car.
I gone used M14 * 1.5mm as a base, and it is approved on cars with a weight over 750kg / 1653lb.

All support arms will be built with 30 * 3mm, and the material is of structural steel S355J2.
Since the spring stay is mounted outside the bearing housing, I must use this quality of steel.
Had it been mounted 1/3 out from the bearing housing, I would have been able to use the S235J2.

Will add the complete list when it's done.

Not the best English, but hope you understand me. ;)

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