These images were sent to me by Clive Prew in June of 2004 while he was still in the development stage of what would soon become the all new Stromberg 97′s.
He was not interested in selling or giving away the delicate Prototype but he was willing to send some early prototype pics.
The New 97s have been out for several years now so there is no danger of giving away any patented or prototype ‘trade’ secrets regarding just how the new 97′s were prototyped or ‘rebuilt’..
These polyresin carbs were built using what’s called the SLA or Stereolithography prototyping process…
SLA or Stereolithography is a prototyping process that produces a solid 3-dimensional object in a vat of liquid resin using a computer controlled/motorized lazer beam. The lazer is positioned and controlled Via computer from a 3D CAD file of the particular object to be built.
-The Computer positions the Laser head and the laser beam heats/cures the object as it slowly descends one slice at a time into the vat of liquid photopolymer or resin. Photopolymer is a similar to film for a 35mm camera in that " Light" imprints or cures on the "Film".
But In this case, the ‘Light’ happens to be a Laser and the ‘Film’ happens to be a liquid….
That said, The actual laser beam will not penetrate down into the vat of liquid photopolymer more than a few thousands of an inch with each step so Clive’s New See Thru Stromberg 97′s had to be built by ‘developing’ many thousands of 3D ‘photographs’, stacked and fused, one on top of the other to form the Actual 3D Prototype Carb.
The layers can be described as similar to a deck of cards… One layer is stacked on top of the next…. the layer below cools while the elevator drops and the object is lowered a few thousands of an inch (into the vat of resin).
..Once the object has fully descended into the vat and the laser has cured it’s last actual ‘slice’, the object is carefully raised from the tank and emptied of any liquid resin then it’s off to the infared oven for cureing.
The resins for this process are about $800 per gallon which translates to fairly expensive prototyping.
I believe that these two particular polyresin images have not been posted anywhere on the www before. The images are also fairly low res compared to the originals (for obvious reasons
). Clive still holds the copyrights to the 3D CAD design that made this Resin Prototype and the subsequent new Stromberg 97′s.
It is interesting to note that this resin carb is actually capable of metering fluid and air into a proportional and accurate "fuel to air" ratio. The SLA process is accurate to .003 inches so even the threads of a small screw hole are accurate to the original item which is scanned into the cad file by a laser beam.
The pics were taken on the day that Clive returned to his office with the prototype freshly cured and out of the oven. Clive was in the midst of carefully assembling the delicate Stromberg 97 with the appropriate hardware/fittings/screws/parts that would eventually be used on the forthcoming -all new- Stomberg 97′s.
Clive Prew had to jump through more than a few hoops in reverse engineering the original Stromberg 97s. I do recall that the ball end of the throttle and/or choke actuating levers presented their own unique problems. The sweat was in the details all of which is history now.
