Hi
I am trying to find out more information on the link front
end shown on the roadable page of your website.
I live in Brisbane Australia and am looking at building
a land speed record bike with my son over the next couple of years.
Any information would be greatly appreciated.

Thanks
jon


http://www.rotaryeng.net/roadable.html
That is a virtual caster pivot ahead of the center of the
tire patch. I designed that for one of Craig Breedloves
rocket powered land speed record cars. Tested to over
400 MPH :)



Old message on the subject.
Quote:
Paul,
 I am very pleased to finally find the designer of this part.
 Everyone who looked at the link found it ingenious. Craig and his 2000-2006
 crew chief, David Schmidt, were very, very proud of the design. The first
 day I saw the car in 2006, David did two things that I had an issue with:
 First, he claimed credit for the link even though I knew he was not on the
 original build crew. Second, he tried to dazzle me; saying that I could
 never figure out how it worked. I'm a flight test ME/AE, and have built
 vehicles in 4 different motorsports. David was out of his league with me
 and everyone I brought in. So I started questioning Craig about the
 original build and the people involved. I never got a straight answer on
 anything.

 The fact is, I recognized immediately that the lower links pointed at the
 steering center. The problem was, Craig had set it up with zero trail. I
 had never heard of any steering setup working with zero trail and this made
 me question the steering stability. The upper links were harder for me to
 understand, since they were parallel. I understood right away that this
 created camber with the steering angle, much like a fork front suspension.
 Since the whole assembly compressed the shocks when steered, there was a
 significant centering force with the car in the air, but not with weight on
 the wheels.

 Something bothered me about this, and it took a month for me to figure it
 out. If we have a single, round profile tire the camber change with
 steering angle would be correct. If, on the other hand, we have multiple
 front wheels then the positive steering axle camber would lead to negative
 roll.

 The lack of trail I knew was neutral in stability, the adverse roll was
 unstable. I did some research and found that wobble/weave stability was
 best at ~5% trail vs. total wheelbase. Less would lead to steering wobble,
 more would couple into the chassis and lead to weave. The 1996 accident was
 a yaw-roll-yaw-roll-yaw-roll oscillation that looked surprisingly like a
 motorcycle weave.

 Looking at the car, we designed new lower-aft link brackets that would put
 the steering center 18" forward of the axle. This respected 5% of the
 wheelbase of 360". I also wanted to flatten out the roll, or even make it
 proverse instead of adverse. So we extended the lower vertical link mounts
 so that we had a vertical center near the ground plane.
 We needed to test this before we got any further. We took the car out in
 the parking lot (~100 yds of flat pavement) and pushed it to less than 5
 mph.
 1.    With the 1996-97 setup, the car spontaneously diverged to one side
 or the other and full-lock steering would not correct it. The tire tracks
 clearly showed only the tire opposite the steering command was on the
 ground.
 2.    With the roll taken out, the car would go straight until we turned
 the wheel. Then it would turn in that direction and not come back even with
 a full-lock reversal.
 3.    Once we put the trail in, it steered straight, turned when we
 turned the wheel, and straightened itself out hands off.
 4.    We then repeated the test as fast as we could push. It worked the
 same up to 7-8 mph.

 Every amateur aerodynamicist (and many professionals who should know better)
 believed that the roll was cause by "SHOCK WAVES!!!" under the car. This
 never stood up to even the simplest analysis. First, at M.89 it wasn't
 going fast enough for shocks of any significant strength to bounce off of
 the porous-plastic surface of the playa. Shock waves do reflect, but they
 lose energy when doing so and typically don't come back up one half of the
 significant length of the object that created them until we get above M1.2
 to 1.3 at the point of the reflection. Second, the leading edges of the
 struts were swept at 75 degrees which means they would not create a shock
 until M3.8! Yes, there were probably local shocks from the intersections
 at the leading edge vs. the fuselage and wheel fairing. These would be
 pretty weak at M.89 on the high fineness ratios of the strut, fuselage, and
 wheel fairing.

 Craig was convinced that gyroscopic forces from turning the wheels rolled
 the car. I did some quick math and this just didn't add up. The car did
 roll in the direction of the engine torque, but it rolled back almost to
 level against that torque. The oscillation was also clearly discrete in
 roll vs. yaw: first yaw without roll, then roll without yaw, reverse,
 repeat.

 One last thing about the focusing link: on Sonic Arrow the vertical links
 angled slightly aft at the top. This loads them in compression and puts
 high shear stress on the pivots. I thought it would be better, if
 mechanically less convenient, to move the upper vertical mounts forward and
 unload the vertical links. When I visited the Chicago Museum of Industry, I
 persuaded the management to let me crawl up in the front wheel well of the
 original Spirit of America. The vertical links were installed the way I
 would have expected. I think Sonic Arrow was done the way it was for the
 mechanical convenience of mounting the links to a common plane, in this
 case, the front of the fuel tank structure. SOA had the steering forward of
 the driver.

 I'd like to hear about everything you did on all of Craig's cars. We've had
 to do a lot of forensic engineering and need to know about all of the theory
 that went into each area of the design.
 Eric Ahlstrom
 President, Star Aerospace LLC

 Guilty as charged. How is Craig? I have not heard from him in years.
 The links form a virtual pivot ahead of the tire contact patch so it forms a
 caster effect.
 Here is an example of such a system on my flying motor cycle design.
 The two vertical links control the camber of the wheel and the lateral link
 mounted at the back of the wheel controls the steer angle. Craig said it
 worked very well up to 400 MPH.
 http://www.rotaryeng.net/roadable.html


 I only worked on the American Motors V8 powered version around
 the early
 70's. Margie Smith, a mechanical engineer from a mining school in Colorado
 did all the drawings. That car was intended to achieve the
 wheel driven land speed record. Little is known about this car as it never
 set any records. On November 12th 1965 the Goldenrod held the wheel driven land speed
 record at an average speed of 409.277 mph (658.526 kph).
  I did a manual analysis using a Friden mechanical calculator of the speed
 verses time/distance and told Craig I did not think we had enough room at
 Bonneville  to achieve 400 MPH with the intended power and tire traction available.
 I used inverted wings between the fuselage and rear wheel pants to apply
 down force to improve the traction. Craig said not to worry and showed
 me some Jato bottles. He intended to fire at the start. I said the best
 place to fire them was around 375 MPH when the real estate was being used
 up much more rapidly.

  The following is hearsay. Craig told his ex wife about the Jato
 bottles and she told her boy friend who happened to know Joe Petrilli(S?)
 of the USAC (I think) sanctioning body. Joe called Craig and said three
 words. "No Jato bottles." AMC cut the funds and I was laid off. As I understand
 it The V8 was removed and a spare lunar landing rocket motor was installed. Craig
 did a demo run at a drag strip and achieved 400 MPH in the quarter mile.

 The car was banned as too dangerous on drag strips. Craig later told me
 he took it to Bonneville and could not get it much above 400 MPH due to
 not enough fuel storage. It was stable for a few runs but he decided to
 take the wheel pants and wings off to save weight. I was not there. The wings were
 essential for wheel driven use as all stabilizing lateral tractions is lost when
 they are on the verge of slipping. Not needed for the rocket configuration
 however the rocket had a slight down trust angle. A run was made and the car
 became  unstable as soon as the rocket shut off and crashed at over 400 MPH. Craig
 survived of course because the round cockpit was double wall .065 alloy
 with two inch high .065 hat section stringers about 10 or 12 degrees apart.
 The rear sub frame was separated as was the front suspension in question.
 I don't know what happened to the remains.

  Margie Smith went on to form her own company building racing car trailers
 called IRD designs as I recall.

 Paul Lamar in Australia back in two weeks.

 Paul,
 Another thought occurs to me when I look at the design you have on the web
 site vs. Sonic Arrow. On Sonic Arrow the horizontal links are very short
 and connect to the aft corners of the swing arm; on your drawings they are
 longer and connect much farther forward. How does this affect steering
 force and feedback?
 Also, as the swing arm is steered, it has to move vertically due to the
 vertical arms (tilt being controlled by their focal point). The vertical
 motion changes the side angle of the horizontal links from horizontal by
 more if they are short vs. long. OTOH, longer links move more with
 suspension travel. Is it better to have them long to keep the
 steering-angle-induced angle change low, or better to keep them short and
 have the suspension-travel-induced angle change low?
 Eric Ahlstrom
 President, Star Aerospace LLC
 My guess (without making a dwg) is it would increase force but it would
 also speed up the steering in a negative fashion. The last thing you
 need at high speed is quicker steering. Thus for a given steering link
 motion the yoke will change angle more. Slop in the ball joints could
 be disastrous. Of course you could gear down the steering wheel angle
 to compensate for the high speed steering but the slop problem would remain.
 As I now recall Craig had the original idea and I just laid it out to take
 out the bump steer by moving the steering link back to the plane of the
 lower vertical link ball joints. It may have been used on the 1967 jet
 car prior to my arrival. What happened to that car after it crashed?
 Bad stuff like bump and deflection steer is also a big no no.
 Car stability is not only a function of the aerodynamics but also of the
 tire lateral forces. The original J79 powered 600 MPH jet car actually
 lifted it's nose at high speed ironically adding to its stability.
 One must know the lift or down force distribution.
 That is why we added an adjustable canard
 on the AMC V8 car. We could adjust it after we made some
 lift measurements on the track. I don't know if that made it to
 the rocket version.
 The whole idea here is to widely distribute the loads into
 the front of the car better than would happen with a
 traditional motor cycle front yoke.

 BTW Craig's nick name was Brave Speedlove :)
 Paul Lamar

Unquote:

http://www.youtube.com/watch?v=ul-vDUpxSeg

It was not built in Salt Lake City.
It was built in Torrance or Lomita California on Amsler street.
See the map. I know I drove there daily from my home in Hermosa Beach.

Paul Lamar