Modified setup thread

Modified setup thread

Postby Mopar 151w2 » Fri Oct 11, 2013 3:09 pm

I'll start by reposting relevant recent rantings - First "How hard is it to turn left?"
Ain't bad, at least with a Troyer, Spafco, or the old Lindblad design my front clip was cloned from. Other designs may have some little tricks that are'nt obvious to the casual observer - like unequal length steering arms, asymetrical ("Howe style") swaybars, or "lead" - unequal wheelbase side to side with the rear square in the car.

3 major areas of concern:
Differentials/Tire stagger: Oval Trackers love locked rears and stagger (difference in circumfrence of the rear tires) because they use it to help turn the car. Fairly easy to adjust (with bias-ply tires), BUT! it only works in 1 direction, and the proper amount varies somewhat proportionately to the radius of the turn. And the car always wants to turn.
At times, it has been hard to find differentials for the most common (10-spline) q/c's, 'cuz they are based on 3/4 ton Ford rearends from the 40's and early 50's, 95% of which ended up under "jalopies", with the differential gears welded solid. "Spools" are a simpler, lighter way to make a locked rear, when you are starting from scratch. Detroit Lockers are fairly common, as they were mandatory in BGN and some other latemodel series which allowed q/c's. A Detroit Locker is not a true differential - it is a captured ratchet, which drives the slower wheel under acceleration, and drags the faster wheel under decell, until the speeds equalize, when it will lock the wheels together. They'll work - but they have their idiosyncracies, and you need to be aware....
A torque sensing, true differential is best - the Torsen, Eaton TrueTrac (old Dual Drive?), Winters Triple Track, DPI Gold Track (can be preloaded - but I'm gonna un-preload mine)
Clutch or cone "Positraction" diffs are rare/nonexistent for Q/C s, FWIW.
Particularly for hillclimb, you want as little stagger as practically possible - even with a fully open diff- and 95 % of the "experts" who tell you that a locked rear will work fine have little idea what stagger is, and have no clue whether they have any if they are using a locker themselves.
Parts 2 & 3 later - I'm going back to bed!

Weight jacking/alignment:
As for the rest of the car. You don't have to change anything to race it. On my Troyer I did move the fuel cell from the left to the right side of the car and the battery also got moved to the right side. Other than that nothing special was done to make it turn right. I'm still using the standard suspension mounting points. I'm not saying that I know it is optimal but it works

Left side weight:
Left side weight - Kevin's Troyer is visibly quite offset, and scales around 54% left with driver. I busted my tail moving the engine 8" left of center when I built my car, and got under 1/2% side to side - moving the battery will change it that much. As it turns out, it may not matter that much - based on some fireside figuring, Brian Dennis and Clark Hinchman may well be more left-heavy than the Troyer.
Ride height - blocks under the frame is one way, or the ol' tape measure. Conveniently, 4" nominal lumber (really a tick over 3 1/2") works well. If you have the setup sheet from the chassis builder, you'll see that the oval setup is significant lower, and may be different side to side - you want equal, and anything hanging down below the framerail won't last! Adjust the coil-over sleeves/nuts 'til the measurements are equal. You want the spring and shock rates pretty close to equal - if 1 of the front or rear pair is a llittle stiffer, it goes on the left side.
Cross weight, weight jacking - if you are careful, and the coil-over nuts are in roughly the same place side-to side, this will be close already. However you wish to express it, cross weight should be 50%. On scales, this means that RR + LF add up to the same figure as LR + RF - The closer you can get this, the more equally the car will turn left & right.
Hillbilly method (endorsed by the PRODOG hisself) : need a floor jack , a big socket or short peice of tubing, tape measure, chalk or marker. Measure between the lower control arm mounting points, and find the center. There may already be a setup point mark there, or you need to mark it. Lay the socket on it's side in the lifting cup of the jack, line it up with the centerline, and jack up the car 'til the front tires just clear the floor. Measure the rear ride height - it may be a little different, because the frame is not level f/r, but it needs to be equall side/side. Adjust 1 side up and the other side down, so's you dont get your ride height all ka-wak-o. At the rear, you don-t need the socket tn the jack, and the centerline is the big cast rib at the bottom of the quickchange. Level the front of the car, and recheck your ride height.

Front and rear alignment:
A) check the rear for toe and camber - you want either one as close to zero as possible. Some guys screw around with 'em , or they get bent from crashes/contact/ Ted Christopher or Punky Caron being in the field. There is a knack to doing this in the car, and I ain't got it. So, it may have to come out, and go to someone with the knack - like Rusty Ball, Quinn Boisvert, or Pat Murphy. Regardless, it gets squared with the chassis centerline. Measurements are always made at ride height, tires @ 20 -25 psig and dead equal, with driver's weight in the seat.
Caster/ camber - look at the setup sheet - you want to use the reccomended RF caster on both L&R, dead nuts even. Camber starting point is the reccomended minimum negative for RF on L&R, best fine tuning method is by temoerature.
Toe: Toe follows camber. On a front steer car like the mods described , start with a whisker (like 1/32 total@ 0 camber) of toe-IN, and around 3/32" of toe-out @ -1 deg. camber. BE careful, be very accurate. If the toe is not correct, the car will follow whichever front wheel is heavier at that instant. On our roads, you'll look like !
Mopar 151w2
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Joined: Fri May 11, 2012 9:08 pm

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