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Design is an iterative process.
The guide design above was suggested to me by Josh Greenwood.
Originally it was to use a piece of railroad rail, the flange becoming the slide and the cap the ram.
Luckily I was unable to obtain the 150# rail I wanted.
After examining the rail I had, I realized that the center of gravity (mass) is near the center of the web.
I wanted more of the mass to be out in the ram and I wanted more throat depth.
So I decided to use a short section of 6# x 25 pound wide flange beam, cut off one flange and weld on a piece of shafting for the ram.
While laying out the beam to be cut I realized that I could leave the center and cut off two strips thereby gaining about 3/4" more throat depth.
The strips cut from the sides could become guide spacers (requiring shims).
Good plan I thought, and proceeded to make the above drawing. While making the drawing I made another realization. I was going to cut off part of the flange and then weld a piece back in the same place (within 1/4")! So, the plan changes again! This will save finding, cutting and welding one part AND will produce better results. This area of the design has required quite a bit of thought. Ideally the lifting point on the ram is on a axis through the center of gravity. However, in this design the center of gravity does not line up with were the load is applied at the dies. So I have compromised and attached the linkage between the center of gravity and the point of applied load. I have also had to back away from my original plan of designing so that the shock could not possibly be over extended. The problem is, if I designed in this narrow range it left no room for hand held tooling and dies. It also assumed that the design premiss of the shock absorber was going to fail. I decided I could not design with a defeatist attitude. If it didn't work I'd have to replace the shock with another linkage and the point became moot. Since making this decision I ran a test, lifting and droping a weight with the shock absorber as quickly as I could. The shock only extended a very small amount (1/4"). This is what I expected. The rest of the dynamics are still a question that only a working model will prove. East Coast JYH photos NEXT! East Coast JYH! p.4 |
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