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goscommons / Grapples

The grapple is an implement that attaches to the Front End Loader (FEL) of a machinery. It requires a separate set of hydraulics in order to operate the open/close (grab/release) function.
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Design Optimization of Mechanical Parts #34

Open jurra opened 6 years ago

jurra commented 6 years ago

image

I collect the comments from the chat discussions, to then document better the issue:

Weight is the big limiting factor. SO my goals were a) to use lighter material b)to remove material from wherever I could without compromising strength

Oh, so you are optimising weight but keep same strength? Can you show the boundary conditions as well? Loads and fixtures you used for FEA

Correct. Thats why you see the holes in the tines, I didn;t see any noticeable loss on strength when compare the tines with the holes with solid ones And thats why I want to use AR400 steel 1/4" width , instead of 3/8" mild steel.

But maybe I should go to the middle ground with A572 alloy grade 50 which welds well and is stronger than mild steel

But AR400 is good for torch cutting and also 4 times more durable than A572. However A572 is economical to buy. So I would suggest your original choice was better. @polemidis of course, I have to check out FreeCAD analysis, but it wont be different in theory

The price difference is insignificant. I got quotes for a 4x8 sheet around 370 for mild steel, $450 for AR400. small difference. I only worry about welding it. It needs preheat, and slow cool down

vinaybhajantri commented 6 years ago

After a discussion with @polemidis we decided to make some force calculations first and then dive into FEA.

The scenario of interest would be grapple hitting a rock while running at full throttle, and the goal is to reduce the weight of the grapple

Inputs for the calculations:

Reference for traction parameters- see page 9

polemidis commented 5 years ago

After using the grapple for a while I realized that there is no need for that calculation. The reason is that the tine is never in such angle as the analysis shows. Even though when I tried it for testing reasons, the bump is absorbed by the tractor.

However there is analysis needed on the closing action of the lids. If the grapple is uneven loaded, when the cylinder pushes the lid it deforms. I have not pushed it to the limit but I am not sure that the lid will hold.