Old 05-27-2008, 06:44 PM
  #66  
John Stranahan
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Josh-Good to hear from you on this thread. Yes that would be your motor spacer and your tires. Should not leave them laying around. Josh is an experienced hand at the oval as well. He held our track record qualifying laps, briefly during a visit to Houston. Be glad to have you back. I may be faster with a Battle Axe. Thanks for the reinforcement on motor movement. I think the answer is more like this. A rear weight bias always causes oversteer because of the overloaded rear tires. That is the same trouble we fight with that huge left rear down tweak. My right rear only has about 3 ounces on it now.

Measuring Ackerman
I was asked to describe the method I used to measure Ackerman. I described Ackerman previously. Now the racer usually does not need to measure this, but it is a little like left down tweak. If you don't measure it you can't really share it with anybody with a different car.

Car on setup board. Set to 0 toe in. Board up against block or wall. Use rear width lines to center the rear (no extra spacers). Use any front opening to center the front with the center line on the board. Using tire edges will not center the front of the car due to different cambers left and right.

Use the combination square with an adjustable bevel attachment on the right front tire to set it to a convenient angle. 15 degrees is more than we use on the oval but it gives more precision on the measure. Now move the adjustable bevel and rule to the left side wheel and see what angle is there. You just rotate it until it is parallel to the wheel by eye. This is shown in the first photo. It helps to have a straight set of wheels on the car (or Darksides setup wheels, Eric send me a set and I will take a nice photograph of them).

The second pic shows the reading on this quick setup, 19.5 degrees. That is the measure stock. I have made a change to steering link angle by sweeping them back as they go out. A more accurately done setup showed 19.0 degrees with my angled links.

Now I also have a Browne and Sharpe dial protractor (photo 3), that could be used, that has more precision but generally your wheels are not perfectly straight. This Starrett combination square is also pricy but imported models from harbor freight are really cheap these days maybe $6 (no kidding). Imported dial protractors are also now available from Grizzly industrial. That's the only place I have seen them now. About $40.

Ackerman is related to the difference between the two angles you get. The second B & S measure gives me 19.07 degrees (19 degrees 40 minutes) on the inner wheel when the outer wheel is set at 15. I did this one more carefully compensating for a rear spacer. It agrees with the 19 I got previously using the bevel attachment.

And there you have it.

Ruggedizing the car
Final ruggedizing is complete. Blue Foam Bumper BSR, Steel screws on rear pivots. Steel ball nuts with thin washer on rear pivots, 6 plastic body post instead of aluminum. Heavy duty servo, Steel ballstuds with little Nylock nuts on the steering arms. The Aluminum ball nuts have no locking feature and wear quickly outdoors. The car is at 41.0 ounces with about as thin a tire as you can have. Perfect. I need to find a way to lock the steering arm to the steering block. These got loose. Maybe a longer screw with Nylock nut to prevent overtightening.
John
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Last edited by John Stranahan; 05-27-2008 at 11:06 PM.
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