DMSBD Tech Tips

DMSBD Parts Installation Clinic - Brake & Steering Assembly  Written by- Ian Carsten

MSX International, 1426 Pacific Drive, Auburn Hills, MI, Saturday, March 16, 2002

The Steering and Brake Assembly Clinic, which is the third clinic in this series, was well attended. Detroit Metro director, Joe Flynn, began by discussing the basic ideas for efficient and smooth operating brake and steering systems for a derby car. He said that it is very important that the controls be placed such that the driver can operate them easily from the standard racing position, which is leaning forward with the upper body as low as possible. He also spoke of the various steering cable and pulley options available to accomplish this.

Then, Jim Scotti, father of Detroit Metro racer and 2nd Place 2001 All American Stock Division Champion, Kyle Scotti, used his specially-prepared stock body and floorboard to show how best to determine the position of the brake/steering assembly, brake pedal, and footrest. Jimís old stock body had cracked beyond use by being stored attached under screw tension to a floorboard in an unheated garage. The contraction of the abs plastic had cracked the shell. From this experience, he advised the attendees to remove the shell from the board prior to winter weather. In view of this, it may be advisable to store your shell in a heated building during the winter months if possible.

However, Jimís misfortune with the cracked shell has unexpectedly yielded advantages. He noted that you must have the body shell on the board with the driver in racing position to determine the proper location of the controls for a particular driver. But the body shell makes it impossible to see where the driverís feet and hands are. Then, when the driver gets out, you no longer know where these locations are. Here is how Jim solved that problem using his old shell as an aid. Since the old shell was no longer usable, he cut out arch-shaped pieces on both sides of the car, from just in front of the cockpit opening to the axle cutouts, and from the bottom upward about 7 inches. Then he mounted the shell to a floorboard. Now, when a driver gets in and into racing posture, it is an easy matter for Jim to reach in and position the unattached controls and footrest to custom fit the driver. Then the driver can get out and the dimensions from these components to the pre-drilled holes can be recorded. Now the racer and his team can use those dimensions to position the controls in their car for a truly custom fit. Several drivers in attendance took advantage of this.

Then Joe mentioned that many racers who attend rallies at other tracks often wear out their brakes and have to change them during the course of a race day. We donít really have that problem at Cronin Downs in Flint, since the up grade of our runout hill scrubs off most of a carís speed. He suggested that if any of our racers drive the rally circuit at other tracks, that they invest in a spare brake plunger and fit a new pad and trim the screw ends flush with the tops of the nuts. That way, he said, all we have to do to effect a brake change is to put the car up on horses, remove the nut and lock washer from the brake plunger eyebolt, push the spring down, and remove the eyebolt. Now you can drop the plunger, install the fresh one from the bottom and reattach the hardware. This way, a brake change can be completed in about one minute.

Next, Detroit Metro official, Tex Finsterwald, spoke about some ideas to improve the steering assembly by removing the excess clearance in some of the parts. He suggested placing the sides of the upper steering shaft support bracket in a vise and then tightening the vise a little bit at a time, removing it from the vise and testing the fit of the shaft in the bracket. By working slowly in small increments, he said, you should be able to remove the excess clearance between the shaft and the bracket. Ted Schafer, father of Detroit Metro racer, Alyssa Schafer, suggested the same result could be accomplished by slightly bending the bracket either up or down at the front. Tex also suggested that the steering could be made a bit smoother by filing and polishing the end of the steering shaft to reduce friction between it and the washer or quarter placed into the hole which serves as a thrust bearing. Further, he said we could remove the excess endplay in the shaft by selecting one or more washers of sufficient thickness to almost completely take up the excess space under the shaft. By doing this, you should just barely be able to install the cotter pin below the ďQĒ washer and through the steering shaft. Then Tex talked about ideas to get the cable to wrap more firmly onto the steering shaft. He said by using pliers to place a sharp bend in the center of the steering cable, the part of the cable adjacent to the bend could be made to better conform to the radius of the shaft. Further, Tex said that many racers feel that the steering turnbuckles generate less air drag by adjusting it until the ends of the two screws were touching. If you use this idea, then you will have to use the steering eyebolts to fine tune cable tension. Also, he said the steering cable clamps should be as close to the eyebolt as possible and touching each other to present the smallest possible profile to the airflow.

This was followed by a demonstration of laying out the location for the triangulation prick punch marks on the rear axle. It was suggested that both marks must have two essential features. First, they must both be the same distance from the center of the kingpin hole. And second, they must both lie on a common line parallel to the centerline of the axle. Two different methods of laying these out that conformed to these requirements were shown. The first used the 12-inch or 300 mm blade from a combination square, the end of which was pushed firmly against a kingpin inserted through its hole in the axle to scribe transverse lines across each end of the axle. Then the blade was put into the head of the combination square and set to 3/8-inch. The square was placed along the edge of the axle and lines were scribed across each of the transverse lines. The intersections of the lines were then prick punched.

The second layout method, which does not require a combination square, uses a trammel with a ball bearing for a pivot and a scriber in the other end. A 4-inch long piece of 3/8-inch cold rolled steel square stock and a scriber are used to layout the lengthwise lines into the axle. You first ink the area where the scriber end will swing its arc. Then you place the ball end into the kingpin hole. You must apply some downward force to keep the ball seated into the top of the kingpin hole. Now you use your other hand to swing the scriber end of the trammel across the inked areas at each end of the axle. Next, you turn the axle on its side on a flat surface such as a tabletop. Now lay the 3/8-inch square stock along the inked side of the axle and hold it against the axle while scribing along the top of the 3/8-inch piece to make lengthwise lines that cross the scribed arcs. Then repeat this on the other end of the axle. The intersections of the arcs with the straight lines are the locations for your prick punch marks. Both techniques are fast and equally accurate

Next, Ted Schafer discussed progress with the ballast weight program he is developing in conjunction with Detroit Metro sponsor, Ideal Steel. He displayed a preliminary specification sheet with dimensions and prices. He said he would have some samples for us to see at the March 23 Weight & Balance Clinic.

Then DMSBD Lady, Theresa Young conducted a drawing of ticket numbers as in previous clinics. Our lucky winners claimed some neat prizes including, a Lucky Monkey, Millennium Cup, Batman & The Joker Hero Card, two Red Ring Caps, John Force Duo, Pink Panther, Blazerís Cap, NFL Football, and a Godzilla Model Kit.

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