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Written by Super User

Parent Category: Big Blue Saw Blog

Created: 27 October 2016

Rick Johnston was working on his  Factory Five Racing MK4 AC Cobra replica (shown above) and wanted an upgraded braking package. His solution: custom brackets waterjet cut from stainless steel by Big Blue Saw.

Once he's tested out the parts and worked through any bugs, Rick plans to make the designs public. For now, here's a sneak peek at the custom braking package partially assembled.

 

 

Rick gave us some technical details on the how and why of his design.

The design is modular and covers both the front and rear brakes. The outer bracket you see on the rear brakes is also used in the front. This is why there are 2 additional “outer brackets” (“L” shaped) in the part outlines [shown above].

 

 

This allows the mounting of front brake packages to the rear. Cobras are different than most production cars that the kit industry borrows parts from. Cobras have a typical front to rear weight balance of 55% - 45%. Additionally the center of gravity height is MUCH lower than a typical production car measuring approximately 15” in height. Also the tire Diameters remain quite large for such a low CG height. This means that this kit needs a lot more rear brake than the standard parts provide. My equations (not proven yet) should reduce the pedal force needed from around 150 lbs to about 40 lbs to lock all 4 wheels in a balanced manner (fronts locking slightly before the rears). I am working on another design very similar to this one, that would allow standard production 13” Mustang Cobra brake components to be used that would further reduce cost to builders.

 

And one more look at Rick's ride.

 

 

Note that when Rick ordered, he took advantage of our best tip for saving money on waterjet cutting: putting several designs into the same file. If you've got many parts all made from the same material and thickness, it's most cost effective to put them all into the same file before uploading them to the online quoting system.

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Written by Simon Arthur

Parent Category: Big Blue Saw Blog

Created: 21 October 2016

Unlike acrylic plastic, which is available in dozens of colors and styles, it's difficult to color match polycarbonate plastic. Polycarbonate sheet is generally available in small quantities in one of only a few colors: clear, gray, bronze, white, and black.

Above is a photo of my robot "Big Blue Saw Presents Flipper 720". You may notice that the top is a lovely semi-transparent blue. It's waterjet cut from polycarbonate for extra toughness. How did I create the top without buying an entire truckload of blue-tinted polycarbonate? Read on.

I wanted a robot that would stand out from the typical metal and plastic creations of Robot Battles. A blue top would help with that. After some research, I learned about several common techniques for coloring clear plastic:

• Coloring with a permanent marker
• Applying window tinting film
• Dying with clothing dye
• Spray painting

Spray paint seemed like the least fuss way to go. It turns out that Tamiya, the plastic model kit and RC company, makes spray paints specifically for polycarbonate. They typically sell to hobbyists painting polycarbonate shells for RC cars. It's available in a large variety of colors and styles, including metallic, transparent, and irridescent hues.

I ordered a can off of Amazon in an appropriate color, "Translucent Light Blue", part number PS-39.

Here's a closer look at one of the smaller pieces after painting.

I'm quite pleased with the finished product. It leaves the inside of the robot visible while adding the flair of a bright color.

My tips for using spray paint:

• Make sure the surface to be painted is clean.
• Paint in a well ventillated area away from dust or wind.
• Begin spraying next to the piece to be painted. Starting the spray with the can pointed right at the workpiece can lead to clumpy or uneven paint.
• Move in a steady, even motion across the workpiece. Follow through and stop the spray only after the end of the stream is off of the part.
• Apply in layers and use less paint than you think you need on each layer.

Details

Written by Simon Arthur

Parent Category: Big Blue Saw Blog

Created: 19 October 2016

We often see parts come out slightly smaller than the designer expected when they're designed in a vector based drawing tool like Inkscape, Illustrator or Corel Draw. These parts show up smaller in the online quoting tool than they do in the drawing software. This is due to the stroke width of the part. Let's take a look at how this can happen.

In Inkscape, we'll resize a square with rounded corners to be 5 inches by 5 inches and export the design to a DXF format file.

When uploaded to our online quoting system, the size is only 4.902 x 4.902 inches!

What's going on here?

The secret is that Inkscape counts the stroke width as part of the object's size. So if your line is 0.098 inches wide, this increases the overall width and height of the part beyond the center of the line by 0.098 inches (0.049 inches on each side). Our online quoting tool (and most CAD programs) measure from the center of the line, rather than the edge of the stroke.

The solution is to set a very small or 0 line width before resizing. Let's set the line width to be 0, then resize to 5 x 5 inches, and export again.

Now when the part is uploaded, the dimensions are correct.

Details

Written by Super User

Parent Category: Big Blue Saw Blog

Created: 14 October 2016

You have seen parts from Big Blue Saw being used for robots, lighting fixtures, signs, car parts, electric vehicles, and more robots. But you may be having trouble deciding which material to order. During our Tough and Transparent Sale from Monday, October 17 though Wednesday, October 19, you have two great materials to choose from. And you can save on both of them.

 

 

All of Big Blue Saw's polycarbonate and aluminum parts are made using waterjet cutting, which allows us to turn flat sheets of solid mateiral into real parts based on the designs you upload to our online quoting system.

Polycarbonate is a plastic with a high tensile strength of 8000 to 16,000 psi. 

Being a polymer, it is lightweight. And it's transparent to boot.

 

 

 

Polycarbonate happens to be one of the tougher plastics around.  Impact toughness is the ability of a material to absorb energy and plastically deform without fracturing. To put some numbers behind it, polycarbonate has a notched Izod impact strength of  5.71 ft-lb/in² or 12.0 kJ/m². That's over 7 times tougher than acrylic (Plexiglas®) plastic. So polycarbonate can take a beating without shattering or cracking.

 

 

  

 

Meanwhile, if you need something much tougher, you could try aluminum alloy 6061. It has a fracture toughness (ability to resist breaking completely after cracking) of 29.0 MPa-m½ or 26.4 ksi-in½.

Aluminum 6061 also provides fantastic stiffness for its weight, making it an ideal material for frame parts, trusses, bearing blocks, and the like. It also is corrosion resistant, weldable, and looks good too, which makes it a great choice for a variety of other applications.

If you're looking for stiffness of aluminum or the transparency and light weight of polycarbonate, Big Blue Saw makes the custom parts you need.

 

 

 

During the Tough and Transparent Sale, waterjet cut parts ordered online made from aluminum 6061 in 0.25 inch thickness and polycarbonate in 0.125 inch thickness will automatically receive a quantity discount. This means that when ordering as few as 1 part,  you'll get the same discount as if you had ordered 10 pieces. Depending upon the design, you will save as much as 70% off your order.

Upload your design now to our online quoting system to get started.