Yet another grapple project

[davesisk]

Design flaw

Btw, I tried to post an MPEG video clip, but it's too large...

There's a design flaw in this contraption that I didn't consider. The bucket is self-levelling (when you raise the lift arms, the geometry of the lift arms and curl arm are such that the bucket stays parallel to the ground). The grapple is based on an upside down mirror image of the same geometry, so when you raise the lift arms the grapple opens and vice versa. However, it has enough motion about the pivot point to still be useful for what I intended, I just have to compensate by changing the bucket curl when raising or lowering the lift arms.

I can't think of a mechanical fix for this. I think the best way is MossRoad's design that uses the additional hydraulic cylinder (just like the PT grapple bucket).

Enjoy the photos, and let me know if you have any suggestion about where I could post the MPEG's (largest is about 550KB, other two are around 300-400KB).

Dave

 

[MossRoad]

Re: Design flaw

HOLY COW DAVE!!! /w3tcompact/icons/laugh.gif

How did you figure out the geometry?

Private e-mail me here at TBN and I'll give you a different e-mail address to send me the MPEGs and I'll post them at my web site until I run out of space or you find a differnet host.

Cool!!

 

[bubenberg]

Great job, and allot cheaper than my pt grapple. on suggestion i have is to add an angle iron of your choice, mine was bedframe size, to the front of the teeth, if not they will bend every which way. additionally the angel iron will help you grab more firmly on to your debris. logs etc

 

[davesisk]

Hans: Good suggestion...actually, I made the forks out of 1/2" rod so they would be springy (just in case I encountered a "design flaw".../w3tcompact/icons/smile.gif).

Dave

 

[davesisk]

Re: Design flaw

My email address is davesisk@ipass.net...

 

[davesisk]

Re: Design flaw

MossRoad:

<font color=red>How did you figure out the geometry?</font color=red>

Essentially, the only important pieces (to my thinking) where these:

1) the pivot point of the grapple needs to be on the same vertical line as the pivot point of the bucket.

2) On my bucket, the point where the curl arm connects is 6 vertical inches from the bucket's pivot point (ie. where the lift arms connect). So, the curl connection on the grapple needed to be 6 vertical inches below it's pivot point to get the same leverage and speed but opposite direction.

Of course, as I stated earlier, this ignores the fact that the bucket is self-levelling, so the bucket curls down by geometry when you raise the lift arms, and vice-versa. So, this means that the grapple curls up at the same speed when you raise the lift arms, thus the design flaw.

This would have been a case where some sort of mechanical design/solid modelling tool would have been really helpful to design it detail first. (I was pretty much working from a mental picture.) I've got a copy of AutoCAD, but you (AFAIK) can't "animate" mechanical parts without some pretty fancy and expensive plug-ins. I have copy of something called FreeCAD that lets you do that animation (plus other solid modelling analysis) with basic geometric shapes (freeware), but I couldn't figure out how to use it (it documentation is pretty much non-existent) and it doesn't appear to support drawing solid to specify dimensions...? Something in between would be really nice....if you know of anything (particularly freeware or shareware, please post it!)

Dave

 

[MossRoad]

Here's a link to Davesisk's grapple video.
<A target="_blank" HREF=http://users.beanstalk.net/godollei/pt425/othertractors/grappledemo.mpg>Right click here and choose save target as,</A> then save it to your PC and watch it there.

Gotta say, pretty cool, Dave /w3tcompact/icons/smile.gif

 

[Anonymous Poster]

Re: Design flaw

davesisk,

Is geometrician a word?...I hope so, 'cause I think you're one.../w3tcompact/icons/smile.gif

Just slap some black paint and a Pat.Pend. sticker on it and you're finished.

That baby will work way better than teenagers/w3tcompact/icons/smile.gif

 

[davesisk]

Re: Design flaw

He he...don't do this at home! (In other words, stick with MossRoad's design, it is the more conventional idea and will work much better.) This will do, until I get the gumption to plumb in another cylinder and valve, though...

 

[Spencer]

Re: Design flaw

It may not be the conventional way to do it but it opens and closes. I say you get an "A" for effort. Some sort of grapple is better than no grapple at all. Thanks Mossroad for making the mpeg available to us.