Club Cobra - Goodbye Kansas

Club Cobra (http://www.clubcobra.com/forums/)

- ERA---Speak with Bob Putnam (http://www.clubcobra.com/forums/era-speak-bob-putnam/)

- - Goodbye Kansas (http://www.clubcobra.com/forums/era-speak-bob-putnam/125213-goodbye-kansas.html)

:LOL:
Love the wrench.
If you saw my assortment of custom Craftsman, it would look like the 'land of misfit tools' ;)

Quote:

Originally Posted by ERA2076 (Post 1294040)

Elevation adjuster tool :)

https://imagizer.imageshack.us/v2/64...0/812/qeey.jpg

Well, so much for Craftman's lifetime warranty :LOL:

The lugs are a little thicker so we machined some .250 spacers - went right on to ERA's brackets. You don't get something for nothing - in this case piston area. Can't wait to try it.

https://imagizer.imageshack.us/v2/64...0/513/m5dg.jpg

https://imagizer.imageshack.us/v2/64...0/203/h4z0.jpg

Quote:

Originally Posted by kevins2 (Post 1294064)

Well, so much for Craftman's lifetime warranty :LOL:

You don't think they will give me another one? :eek:

Quote:

Originally Posted by ERA2076 (Post 1294070)

You don't think they will give me another one? :eek:

Actually, they probably would. If you still have the other half you could go to two Sears and get two for one! :rolleyes:

and both at the same time - savvy :cool:

You're obviously getting your tools from the wrong place.
I've been able to find just about everything I need from these folks.

http://img.photobucket.com/albums/v6...ps8aa64e22.jpg

http://img.photobucket.com/albums/v6...ps782fa1ca.jpg

http://img.photobucket.com/albums/v6...ps0cf8ca28.jpg

http://img.photobucket.com/albums/v6...ps2b9ec4a1.jpg

There's also a listing for a new series of fasteners for some of those hard to define attachments that I run into when I'm doing fine precision work.

http://img.photobucket.com/albums/v6...ps656e68e1.jpg

Just trying to help a fellow out.
DonC

We got the fasteners covered - the Nail Bender and the 48 piece Screw Driver set are of interest. :cool:

x-chr

With summer coming don't pass up the 8 Function Electronic Multitester. It has the much sought after meat thermometer and corn on the cob holder functions that are missing on some other brands.
DonC

Picked one up last summer for my wife - unbelievable how much use she has gotten out of it.

:D

x-chr

I have been working with Performance Shock Inc. to fit my FIA with Penskes. We worked from drawings as much as possible, but were not able to identify a Penske shock that would fit without using remote reservoirs. They arranged to have Penske ship me a shock so we could fit it prior to purchase. One of the issues is length of hose needed. The aluminum cradle has a boxed cavity on either side at the top. We are going to mount the reservoirs horizontally in the cavities. This will assure the entire cradle and suspension can be dropped and installed cleanly into the chassis.

https://imagizer.imageshack.us/v2/64.../834/yh42t.jpg

On to springs -

I have been told ERA comp cars have run 550 and as high as 600 lb springs in the back and it was suggested to run 350 in the front.

I keep looking at Allens car concerned with the amount of roll I am seeing. I have been focused on roll bar rates but while reading Smiths stuff last night it occurred to me maybe we don't have enough spring. I found a reference for ride frequency vs spring rate for un-sprung mass.

http://www.optimumg.com/docs/Springs...Tech_Tip_1.pdf

Non down force race cars run a ride frequency as high as 2.0 hz. I am shooting for a 2315lb race weight car. If it were properly balanced and I use a 49/51 split I would have

Front => 567 Total - 100 (un-sprung) = 467 lb sprung
Rear => 579 - 100 = 479 sprung

From my reference a 2 hz car

Sprung Weight => Needed Wheel Rate

500 => 205 Wheel Rate
600 => 246 Wheel Rate
700 => 288 Wheel Rate

I am shooting for a 10% difference between front and rear with a faster rear. I calculated motion ratios for the front and rear of my FIA. My front is optimized some so this won't transfer straight across, but it is of interest none the less.

Cliffs ERA Front - 467 Sprung Mass needs a 205 Wheel Rate

Spring => Wheel Rate

350 => 160
400 => 183
450 => 205 * Notice how much front spring we need to hit the 2.0 hz.
475 => 217
500 => 228
525=> 240
550 => 251

Gen II ERA Rear - 479 Sprung Mass needs a 205 Wheel Rate. Since I want to be 10% faster 205 * 1.1 = 226. Smith likes to go up so

Spring => Wheel Rate

550 = > 222
575 => 232 * Right in line with ERA suggestions -
600 => 242
625 => 252
650 => 262

So a 450 front / 575 rear would satisfy the 2 hz ride frequency and give me the 10% differential. I've never driven anything this stiff and I hope it does not exceed chassis stiffness. (Shelby did and it worked anyway - :LOL:!)

That seems like a lot of front spring, but looking at Allens car and knowing the rear roll bar was maxed and he was picking the inside tire makes me wonder if there was enough roll stiffness in the springs. A stock ERA front would require heavier springs because the motion ratio is less than mine.

There are two holes in the shock mounting tabs. The 3/4" outside placement is worth a lot.

https://imagizer.imageshack.us/v2/64...0/836/l13g.jpg

450f/575r

Am I missing something on the front?

x-chr

If I were to use a 350lb spring the and a 575 rear

We would have wheel rates 160f/232r respectively - that is a 45% difference in wheel rate. I would thing the front would want to trip over itself.

chr

Not exactly your #'s but have the 125# split F/R. Would be a softer option, and the price might work for you. Cheap enough to play with.

Set of coilover springs for an ERA 427 (or other car, your decision) for a Competition/Open Track setup with Spax or similar type shocks.

2 Front 10"x400# AFCOIL also-2 Eibach 10"x350#
4 Jag Rear 8"x525# AFCOIL

$200 for all 8 or BO. Reply @ a427sc@aol.com

Thanks for the offer, but I am committed to the Penskes .Double adjustable and I can run the bodies on top.

chr

The reason I am fixated on the roll is the roll centers do not move well together front to rear. The short front control arms have the front roll center moving laterally 7" at 1 degree of roll, where the back moves only 1/2" because the control arms are longer. In "Tune to Win" Smith states he thought control of the roll centers was more important than maximizing the camber curves because it affects how the car rotates especially at turn in. The front shocks were valved for 350lb springs but I know there is some float there. I am going to run the heaviest spring I can up to 450 in the front. Then match the appropriate rear spring and have the rears valved for that. It is a place to start.

chr

Lateral movement of the roll centers is an inherent characteristic of a short-long-arm design. The basic ERA intent is to keep the outer roll center fairly close to the ground so that there is minimal laterally-induced instability on the outer tire under cornering loads.