More serious modifications

(this is a slightly abbreviated version of the letters sent to our sponsors as part of the Bonneville 2013 Fundraiser)

We have progressed with the frame modifications.  The steering head removal was a project in itself, requiring almost two hours to remove it from the frame.  This care was needed to reduce the gap left after cutting and redressing the joint areas.  You want as small a gap as possible to fill with the TIG filler rod.  This is to maximize the strength of the joint and to minimize the distortion that an excess of filler rod can cause.

2013_2_15angle of the nose

Now the decision has to be made as to how much rake to take out of the nose.  Adding degrees of rake adds stability.  This very same stability reduces the responsiveness of the bike to steering inputs.  This bike is an absolute pig under 100-120 miles an hour.  This makes a productive start of the run more difficult as you are fighting this thing to keep it in the spot in the lane you are aiming for.  It also makes it a two man job to roll the damn thing around as well.  Putting it on the dyno is yet another matter, fitting around the corner and through the door.

The safer bet would be to take four to five degrees out of it and wind up with 40 degrees or so.  This is where I think we will start and see how it looks after the reinforcing is done and the centerline/ground plane references are rechecked.

2013_2_15 behind the motor

Looking into the bay behind the motor, the finishing of the x-bracing is the first order of business.   The loop that held the ballast and fuel tank is removed and a flat X is finished off.  This is a bit more interesting than a standard 90 degree joint because of the included angle being so close.  The sensitivity of the gap is much more so because you have two angles that change as the pieces approach proper fit, and because of the reasons described with the steering head, very important.   This is the kind of thing best done in solitude, without phones, and other distractions.

Cross bracing of the perpendicular variety is next and a number of different planes of flex were of interest.  While there isn’t the traction found at the dragstrip, the bouncing , wheelspin, and aerodynamic forces can introduce their own type of variables.  Originally there was a certain amount of flex built into the chassis.  This was taking a page from the Top Fuel dragsters where if you watch them going down the track they arc up in the middle of the car.  This allows the wheels to stay on the ground, while still transferring weight to the rear end of the car for traction, an important thing at Bonneville as well.  While there was a discernible amount of flex when the bike is fully loaded with the 180 lbs of ballast weight, plus the rider, big battery, and fuel, it may have allowed a bit of torsional deflection to occur under the right conditions, aggravating the wandering we are hoping to eliminate.  So we will try tightening up the vertical flex and eliminate the torsional.

cross braces added to bottom
cross braces added to bottom

Well it’s off to determine if we are going to put the downtube cradle under the motor or not.  It is looking less and less likely that we will need it if other areas are properly strengthened and gusseted.

Finishing up the bracing behind the motor was accomplished and pressure testing of that area of the chassis began.   A few bleed holes from the first construction were found and plugged and the final weld-up of the bracing began.  This all had to be done before the steering head was reattached so as much of the squirming around of the chassis is accomplished to allow the best chance of the steering head being perpendicular to the rear axle.  The goal is to loose less than 10 psi overnight.  That makes it possible to use this area of the frame as an air resevoir.  It doesn’t take much of a leak to lose that amount in an hour, but eventually we were able to exceed the goal by loosing only 5 psi in 24 hours.

Mounting the rear fender was next.  This was involving a steel 10 inch wide unit to put a bit more heft in the rear wheel area and still keep the salt from spraying up into the fuel tank and battery area.  Clearance will need to be made for the chain and chain guides after it is in place.     Enough room has to be allowed for tire growth.  While not as big an issue with the rim/tire combination we use as it is on the drag racing slicks, you still don’t want to burn the center of your tire out at 210 mph.  I could be embarrassing and expensive.  There also needs to be allowance for possible different combinations of tires, wheels, and gearing in the future.


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