SACC Power Steering

Looks good. Good engineering thought process.

I'm not sure how much positive caster you can dial in without significant fender/tire interference.

I'm concerned with the big delay to deliver the kit from SACC as well as thinking there is a smaller, more compact EPS unit that they can use?

This is a good time of the year for me to consider a project like this. It likely will be at least April before the car is on the road because of the weather conditions anyway.

Even LA is getting washed away. Not even a good time for boats...and you can't even be guaranteed your flight will get off at all or even close to being on time.

Nope. Garage time it is!

Steve,

With your upper control arm mods, how much caster do you have with the upper ball joints fully to the rear?

Steve,

Is the upper control arm in the picture upside down, on the wrong side of the car? Shouldn't the plate be on the top?

Steve

Steve, yes, it is the wrong side.  Thanks for catching this.

@davidnunn posted:

Steve,

With your upper control arm mods, how much caster do you have with the upper ball joints fully to the rear?

I will be measuring the maximum positive caster angle today or tomorrow.  Before the modification it was slightly less than 2 3/4 degrees.

Moving the upper ball joint towards the rear will also offset the wheel towards the rear so the wheel will no longer be centered in the fender opening (assuming it was in the first place). How much offset depends on several things. This may or may not cause clearance issues or aesthetic consequences. People have mentioned offset bushings for caster adjustments. If they are available, that is a good option to offset the lower control arm forward. We built custom upper adjustable control arms and modified the lower control arms to get the caster adjustability I wanted with keeping the wheels centered to the body. Attached is a very crude sketch to illustrate the point. I am not suggesting that the upper joint mod shouldn't be done, just sharing for the few that may not know this.

The offset bushings would be the simplest way to accomplish the increase caster but have disappeared from the common sources.

I would go for a set if I could find them.

Doug,

I missed your question: "Wasn't there a group buy of 25 from the Michigan chapter?". Not sure if it was 25 but yes, there was a group buy of EZ Electric PS systems but it was the Great Lakes POCA Chapter. Gerry Romack (glpanteraclub@gmail.com) arranged it. In fact, I think they've done more than one group buy of EZ systems.   

I don't think any of them have chimed in here. I like to get feedback from as many as I can. Everyone has a little different experience and notices slightly different things.

I will say though David, that the EZ uses a VSS and the SACC does not as far as I see or I mistaken on that?

EZ uses either a VSS or a potentiometer; it’s up to the customer. Naturally it’s less expensive with a potentiometer, but not a lot cheaper. The VSS they supply goes between the angle drive on the ZF and the speedo cable. SACC only supplies their system with a potentiometer.

As I mentioned in a previous posting, the only person I know of that has experience with both systems is Gerry Romack. I’m sure he would be happy to reply to an e-mail asking for a comparison of the two systems.

The Japanese units, made by Koyo or NSK,  have a fail safe built into the basic motor device that will go to what was programed into that chip as the assist necessary for 43mph.

For those you only need a three wire hook up for "basic operation". The 10 gauge black (-), red (+) and the white wire to the ignition switch "run position".

IF you want to dial down the assist automatically as speed increases, then you need the separate brain, i.e., the little separate box. It's only purpose is to dial down the boost according to vehicle speed.

I'm not sure why SACC uses the box unless the EPS CPU sees the potentiometer the same way as it sees the VSS?

The US GM versions will not operate without that original CPU box or the little aftermarket "patch in" box that fools the EPS motor.

I'll email Gerry Romack. I'm enjoying this discussion. It's fun and informative.

Typically with the 'Johnny Woods' A-Arm mod you are going to have 3/4" of spacers total, if all in front of the ball joint it's about 7.5 degrees of caster which is ideal for a wide body car. The narrow body benefits most from 5 degrees which can usually be achieved with the 1/2 spacer in front and 1/4 " to the rear of the ball joint.

I plan to start with the 3/4" shims and try to get a feel for better centering of the car.  I am actually looking forward to having a heavy feel of the steering wheel.  Prior to this the steering wheel turned with very little effort and the car has not returned to center very well.  Thus I will start with the maximum positive caster and then rearrange the shims for less positive caster as needed.  I have a nice assortment of shims to work with.  My plan is to measure the degrees of caster from the start to finish of this endeavor.

With an EPS, I'm not sure there is value to a lot of caster. My 73 (4460) is still stock caster (maxed out) and has a nice feel of not fighting you to return to center.

As a matter of fact because of that I'm not sure EPS is worth the effort unless the car is a wide body?

I'm probably used to the feel of an American PS car and not seeing the difference?` I realize this may be a 180° wrong thought but am still working this out in my head.

Anyone want to loan me theirs for extensive side by side testing? I'll be gentler then the car magazines? I mark 7,000 rpm's on the tack with a yellow crayon so there are no issues.

Greater high speed stability isn’t the only reason  to increase caster. It also improves turn-in and makes the car feel more nimble. The penalty is increased steering effort. Most contemporary sports cars run 5-1/2° or 6°. In fact, the Pantera’s front suspension was designed for these levels of caster but Ford thought the steering effort was too high, so caster was reduced accordingly.

Do the very early cars have provisions for increased caster? Racecarmikes comments about moving both the upper and lower suspension arms equally opposite to center the wheel is well taken.

Hey Doug, If you want to finish putting my 5715 together, you can borrow it. Redline is 6500 though.

@davidnunn posted:

Steve,

With your upper control arm mods, how much caster do you have with the upper ball joints fully to the rear?

With the the ball joints fully shimmed to the rear and the car on the ground, I am reading 6.25 degrees positive caster.

A little more about caster. Mostly cut and paste but slightly embellished by me.

"Caster:

The steering axis is angled such that a line drawn through it intersects the road surface slightly ahead of the center of the contact patch of the tire on the pavement by a distance called trail. The purpose of this is to provide a degree of self-centering for the steering—the wheel casters around in order to trail behind the axis of steering. This makes a vehicle easier to control and improves its directional stability (reducing its tendency to wander). Excessive caster angle will make the steering heavier and less responsive, although in racing large caster angles are used for improving camber gain in cornering. Caster angles over 7 degrees with radial tires are common. Power steering is usually necessary to overcome the jacking effect from the high caster angle.

The steering axis does not have to pass through the center of the wheel, so the caster can be set independently of the trail, which is the distance between where the steering axis intersects the ground, in side view, and the point directly below the axle.

Caster angle and trail both influence the steering, albeit in different ways: caster tends to add damping, while trail adds "feel" and returnability (to self-center)."

Take particular note of the last sentence.

I revised my very crude sketch to show the trail (which will vary depending on tire size and other design aspects) to illustrate how that can vary depending on how caster is added. The red car on the right side of the sketch (very simplified) shows some things we experimented with on our race cars. I don't have the drawing here so the dimensions are arbitrary just to illustrate the point. Design "B" worked OK but required lots of arm strength and was overly sensitive to steering inputs. For "C" and "D" I redesigned the front uprights from a forward spindle design to a trailing spindle design. That tamed the beast. The car was no longer overly sensitive to steering inputs and I didn't need to take Advil after the race. I was ready to install power steering before the change. The lap times improved, mostly because the car was much easier to drive.

Mike

@racecarmike posted:

Hey Doug, If you want to finish putting my 5715 together, you can borrow it. Redline is 6500 though.