TFA Racing Lakester "tweak" diary

[gas pumper]

Just to address Nathan's long-short axle idea.
We know a NASCAR chassis guy who developed gun drilled axles a few years ago to handle just this situation. His idea was to look at each axle as a torsion bar and remove from the center enough material to even out the spring rate of the axle from side to side. Apparently it works and eliminates that problem.

Probably not a concern with the FD lakester unless the axle shafts are different lengths.

VERY interesting thread!

Frank

[SPARKY]

I am pretty sure Torsens or True Track available  on several QC system

[entropy]

After getting a ton of input, here is an updated Handling Issue list
Thanks to everyone!!!

#5448 handling issue - technique stuff:
1. minimize amplitude of course corrections, "it WLL come back"
2. Keep a light touch on steering wheel, gentle, smooth course corrections,
3. Both hands on the steering wheel equally, be careful during shifting & parachute deployment
     - "SS:  parachutes need to be actuated without removing hands from the wheel"
4. Any movement of the eye can be translated into movement of the hands...
5. Feedback: ask an experienced TFA-sized guy make a pass in the car (Tom?  Rex?  Stainless?)
6. other??

#5448 handling issue - set up stuff:
1. Would adding 300# F ballast help stability? (gives 55/45%) Pros & cons
2. Re-determine our Cg-Cp relationship, document basic vehicle info
3. Re-check L-R tire psi are equal; is F-R psi a factor?
4. Further minimize play in steering linkage,
     - look at the steering reverser box, get gears tighter, replace?
     - ?replace Heim joints (tie rod ends) w/something better?
     - ?replace linkage universal joints w/higher quality?
5. re-measure scrub radius, how close to zero?, find a way to measure it more accurately
6. Other?
7. Put car on automotive alignment system:
- measure castor; lots of caster is always good to go straight (not adjustable)
- measure front toe in; set to ?1/8?", is it better to err on the side of more or less toe in?
     - review toe-in vs toe-out
- check the rear axle for being perfectly perpendicular to the car's centerline
- check the toe in in the rear, assure it is equal on both sides and not all on one side
- other?
8. assure both F tires are same diameter, add pressure to the smaller on to equalize (as feasible)
9. assure L&R( F?) tires are at same psi in starting line, sun impact (up to 15psi difference)
10. R tires, assure same circumference, use pressure to equalize as feasible, watch sun effect
11. put laser on car F-B, assure body is straight
12. add steering stabilizer?
13. load/ballast one side of the front more than the other?
14. tq steering from unequal length F axles? (or something like that)
15. check toe-in setting stability under accel stress?
16. re-scale wet car w/suited driver to assure F L&R wheels are equal wt +/-?10?#, also document F/R wt distribution
17. slow steering rate down?

[SPARKY]

have you scaled the car with circle track type scales

[entropy]

have you scaled the car with circle track type scales

SPARKY,
yes indeed we scaled it as received (IIRC, RF = 70# too heavy) and we used a set of scales a second time to set up rear axle adjustment so that F L&R wheels were within 10# or so of each other.

But yr point is very well taken, re-scaling for sure needs to be on the list.
THANKS
karl

[Stan Back]

I don't know where or what it is now, but it's almost always a smart thing to slow the steering down from "stock".  Imputes at speed can be magnified with "stock" ratios.

[entropy]

I don't know where or what it is now, but it's almost always a smart thing to slow the steering down from "stock".  Imputes at speed can be magnified with "stock" ratios.

Stan,
thanks!

[SPARKY]

I was trying to find Chaz original build diary to study the driving frt axle and what brand to determine  which side the pinion is on  but it must have been taken down!

[Stan Back]

. . . also -- putting a smaller steering wheel than "stock" will quicken the steering, too.  And in our case, this is often done to aid in getting in and out of the vehicle.

[entropy]

I was trying to find Chaz original build diary to study the driving frt axle and what brand to determine  which side the pinion is on  but it must have been taken down!

SPARKY,
This is what is in our spec list  for rear end:
Rear End (front wheel drive)         
   Gear oil:  Winters P/N 1730,  #293 Supreme Gear Lube, SAE 80W/90 w/moly      
   Capacity:  approx 5 quarts. Fill utill the forward fluid level hole leaks; install fwd plug, then slowly add until the rear fluid level hole leaks      
   Winters Performance Products, 5270 Quick Change Rear End, serial #C67255 (Apr 27, 2007, Joe Timney - DCW $1638.28)      
      10" ring gear, 12 bolt, Wide 5 spindles   
      Ring/Pinion ratio: 4:12   
      reverse pinion direction(from normal drive); R&P on right side facing quick change cover   
      Spool, both tires turn at same speed   
      10 spline Quick Change gears = 17/32 (0.53)   
         17/32 (0.53),  is the tallest quick change set
         bottom: big gear (shaft from trans), top: small gear (turns pinion)
         both gears installed with shoulder around spline facing toward cover
         run 17/32 for initial passes
      Current final gear ratio = 2.19, 223mph @ 6100rpm hp max (assuming 6% tire slip)    

[entropy]

. . . also -- putting a smaller steering wheel than "stock" will quicken the steering, too.  And in our case, this is often done to aid in getting in and out of the vehicle.

Stan,
we are evaluating alternatives to our current steering wheel, the top blocks a bit of our Racepak dash.
Maybe go back to a butterfly like Chaz had.
Karl

[SPARKY]

I will have to noodle the reverse rotation---but is the eng rotation and the pinion/ring gear now both trying to lift the LF ---for traction purposes you most likely will need a bunch more frt weight---acceleration is now trying to unload your frt tires

[Rex Schimmer]

Entropy,
I did not see a response to my question regarding your 239 lbs of front lift. Is the 239 number what was seen at the wind tunnel speed (75 mph  as I remember) or is it the calculated lift for 200 mph? Again if it is the observed lift at wind tunnel velocity then at 200 mph it would be 7.1 times higher, 1700 lbs!!! Just wondering.

Rex

[entropy]

Entropy,
I did not see a response to my question regarding your 239 lbs of front lift. Is the 239 number what was seen at the wind tunnel speed (75 mph  as I remember) or is it the calculated lift for 200 mph? Again if it is the observed lift at wind tunnel velocity then at 200 mph it would be 7.1 times higher, 1700 lbs!!! Just wondering.
Rex

Rex,
sorry to have missed that.
I am pretty sure that 200mph was input by the wind tunnel operator and that the results data, e.g. lift, is given in terms of force which would be expected at that number.  Tom suggested 200mph; turns out he was very darned close.

Here's a thought:  anyone who'd like a copy of the 2 page excel spread sheet of our results, please send me your email id
Karl

[entropy]

I am pretty sure Torsens or TrueTrack available  on several QC system

i finally had a minute...
wikipedia: 
The Torsen differential works just like a conventional differential but can lock up if a torque imbalance occurs, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR).[3] When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric traction conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the angular acceleration of the faster output side of the differential.