Fiberglass molding a new sculpture

Chris and I have only done a few molds in fiberglass. This is the first proper one, done on a WED clay sculpture. 

After sculpting, Chris added a mold wall using .02"  x 4" aluminum sheeting. I sheared it into strips and he inserted it into the clay. We wanted to try molding both halves at once to save time, instead of using a clay mold wall, fiberglassing one side, waiting for it to cure, then molding the other half. 

We sprayed three coats of PVA on each side. Then went over the aluminum with some sonite wax to he safe. 

While the PVA was drying, I ripped off a bunch of sections of 38-1/2" 7-1/2oz fiberglass mat. This particular mat can only be used with polyester fiberglass resins. We prefer the mat over cloth for conformability to the sculpture. 

I pre dispensed some of the materials we would be using. I like even numbers, so I used 16oz cups of resin, as this took 5cc of MEKP. 

 

For the first two coats on each side, we used a 50/50 mix of bondo and resin, 16 oz of each, the activator for the bondo, and 5cc of MEKP. 

3 layers of mat on the main body and 5 on the mold wall later, and we have a mold. 

Do not use PVC for compressed air purposes.

Several good links that show why you should NOT use PVC pipe to distribute your compressed air system, or to make any sort of pressurized device, such as a home made pneumatic cylinder, air cannon, spud gun, etc. Although PVC has a PSI rating on it, it is not designed for the types of forces that compressed air exerts upon it. This can result in shrapnel explosions that are very dangerous.

https://www.osha.gov/dts/hib/hib_data/hib19880520.html

http://www.lni.wa.gov/Safety/Basics/HazAlerts/902.asp

As a side note, I personally was standing next too a 3" PVC elbow that was installed with an improperly specified pneumatic distribution system, when it exploded. Luckily I only had small cuts. It could have been much worse.

Welding cubes

For some reason, I tend to weld a lot of rectangles, and cubes, out of steel tubing. 99% of the time, it's 1" x 1" x 1/8" wall. For along time, I have been using these Wilton 90 degree corner clamps that I bought at Lowe's, for something like $30 a piece. They are light weight cast aluminum, and have served me well. However, when welding a cube, it takes multiple set ups, several grinding set ups, and so forth. When a recent project arouse to weld some rectangles and cubes, I decided to invest in some new equipment.

In the first picture, you can see a rough set up using the mentioned Wilton clamps. The second picture being the end result.

I  have been drooling over these clamps, from Stronghand Tool for years. But at $1600 for all 8 needed to weld a cube, they have been out of my price range.

I bought these corner clamps made by Stronghand Tools, to replace my Wilton corner clamps.

But I still need a way to clamp a third axis. After doing alot of googling, I found an image from an obscure website, showing how to use 2 products from Stonghand, to make a less expensive 3 way corner clamp. By using a combination of these pipe pliers and these clamps, I was able to make a cube in one set up! I actually ordered the parts from Welding Supply.com because their prices are less than Trick Tools, but I order some items from Trick Tools as well.

You can see a cube set up here:

After tacking, before full welding. 

Harbor Freight Bar Bender Set up, 90 deg Steel

In the previous post about setting up the Harbor Freight Bar Bender, we bent some 5051 aluminum using the right angle attachment. Here, we will be bending 1/8" x 1" cold rolled 1018 steel. With this material, you can not use the right angle attachment, as the steel will actually fracture on the back side. On these parts, I had to get the 90 degree bend with a small radius around the center pin.

For this set up, we use the bar bender in it's more standard set up, of having the swinging arm pined in the last hole, and bending around the center pin as the mandrel. I wanted a tight radius bend, so I used the pivot pin with no extra mandrel in the center. The driving pin in the swing arm was in the 3rd hole, as I only had a small amount of stock sticking out to bend. In the frame of the bender, I bent against the other pivot pin, although I should have installed the square stop block. I wanted a bend of just 1-1/8" sticking out, and this is about the minimum possible in this set up. Anything less, and the material will slip past the swing arm driving pin and you won't get the full 90 deg.

Setting up a Harbor Freight Bar Bender for 90 degree bends

I love my little harbor freight bar bender. I use it for a lot of parts. We even use a few of them at my day job for bending lots of parts we shouldn't be able to in quantities that exceed expectation. We have actually worn a few of them out bending 1000's of 3/8" stainless rod.

The problem is the lack of set up information for general bending. The book that comes with it is vague in explaining where to put what pins and stop to get the desired results. I will be posting pictures and information for every job I do with mine, for the purpose of helping others like myself out.

In our first installment, I was bending 1-1/2" wide, 1/8" thick, 5051 aluminum sensor brackets. For this we use the right angle bend attachment. As shown below, it gets mounted in the back frame. As opposed to standard set ups where your bending around the mandrel on the center of the frame, with the right angle attachment, you are using the arm to push the part across and over the right angle attachment. That is why the arm gets moved from the center hole, to at least the 3rd hole. Depending on your part, you may move it farther in. When I get some time, I will post a link to a youtube video and a picture of the part before and after.

Calculator apps and online calculators

This is a list of my most often used engineering calculators.


http://easycalculation.com/physics/classical-physics/moment.php

http://easycalculation.com/mechanical/deflection-hollow-rectangular-beams.php

http://easycalculation.com/mechanical/deflection-round-tube-beams.php

http://easycalculation.com/mechanical/deflection-solid-rectangular-beams.php

http://easycalculation.com/mechanical/deflection-solid-round-beams.php

https://itunes.apple.com/si/app/right-angle/id292390648?mt=8

http://www.wiresizer.com/

http://www.syclabs.com

https://itunes.apple.com/lv/app/imachinist/id377711549?mt=8

https://itunes.apple.com/gb/app/etools-pro/id480157834?mt=8

http://trunnion.info/elecref.html

http://www.millerwelds.com/about/news_releases/2011/miller-electric-mfg--co--develops-miller-weld-setting-calculator-for-iphone--millerwelds-com-

https://itunes.apple.com/us/app/bolt-hole-circle-calculator/id587069250?mt=8

Cad examples

This is a design example post for a potential customer. Luckily no one really looks at my blog.

A simple mechanism drawing. This is a single cylinder casket popper.

This is a ceiling swinger prop. 1 cylinder for each arm and another cylinder to operate the head back and forth.

This is an animatronic coat rack. A cylinder for each arm and one for the head. 

Giant (14' tall) prop erector in it's down position.

And in it's up position. The cylinders can be operated in all my models so that I can check exact movements and make sure there are no interferences.

This is the back of a one off custom prop I built in 2008. A cylinder for the spine turn, 1 for each shoulder and then 1 for each elbow. As you can see I use pillow block bearings on almost every movement of every prop.

An animatronic plant monster I am building. This is it in it's up position with arms open. This design uses over 20 bearings, including a linear bearing for the lower rear slide. 

Same thing, but from the side. There is a cylinder to operate the scissor movement up, one to operate the arms opening, then 3 to operate the head up/down, left/right, and jaw.

Shown in it's closed and collapses position.

From below.

An animatronic sleeping bag kicker. This is to show my methods of cylinder bracket attachment and bearing use. I bolt every cylinder bracket to the frame. I never weld them in place. That way the forces can not fatigue the welds on the brackets, which are the most likely to break. 

A small scissor mechanism I designed. It uses a single cylinder and linear bearing to achieve the scissor action. 

A torture table prop I built. Once again to show cylinder attachements and bearing use.

This is a zombie chaser I built. The body mechanism is driven down the length of the table on a linear bearing and driven by a cable cylinder. There are cylinders for each arm and 1 for the spine/waist movement.

Showing the cable cylinder and linear bearing. I calculate load ratings and life expectancy on all bearings and make sure they can handle well over the loads they will see, and make sure they will last for years with little maintenance.

Same mechanism showing the lower bearing and spine assembly, and my use of a cable carrier for the bodies airlines, so that they can not be damaged by the forward and backward movement along the table.

An overall view of the model.

Below is a machine I did at my day job. I did a lot of the engineering and most of the assembly and manufacturing.