Project A Better Grabber

Currently laid up a bit due to some outpatient surgery yesterday.  Good news is the only physical requirement to blog is to simply be able to bang out words on a keyboard.  Fortunately, the knife didn’t impact my ability to type so I can spend my downtime being more attentive to my loyal readers!  Yesterday (also in recovery mode) I featured a new project for this year’s Haunted Trail.  Actually, this year brought a large number of new features each of which will likely make their way here in the not too distant future.  In fact, let’s go ahead a feature another new element – this time an animated decoration.

Scenes from The Haunted Trail of Tears 2017

Yes, folks, another ground grabber.  If you recall, last year I took my first attempt at one of these (link here).  This year I wanted to improve upon that design and deliver a better product.  I had been seeing a number of designs on the web (thank you Pinterest) and opted to work off a template from Yard Haunt (link here).  I liked the fairly basic design and really liked the effect.  Of course, I have to extend and improve upon it – it’s my nature.

I knew I needed a frame to rest the arm on.  The Haunt plan used a block and what looked like nails to contain the arm itself.  My preferred medium is PVC so clearly we needed to start there ha.  There is always a struggle trying to find flat endcaps.  Places like Lowes have gone to rounded tops which are useless when you want to fix them to a board or piece of plexiglass.  Menards tends to have the flat ones when they actually have them in stock.  Knowing how much of a pain that option was, it was time to spend some time in the PVC aisle and figure out an alternative.  The results of that noodle time …

Project Grave Grabber Halloween 2017

Hit the jump to read about how this all went together!

PVC Plugs.  These always have a flat end and in my opinion look much sleeker.  Simply drill a hole through the end and run a bolt up through it.  Recommend you countersink the bolt hole on the other side so it doesn’t scratch whatever surface you put it on.  Oh, and to save extra work in the future, go ahead and place a lock nut on there so it doesn’t loosen up.  I then slapped a straight coupler on it to hold the support pipe.

Project Grave Grabber Halloween 2017

I wanted the arm to move through it smoothly.  To keep the frame somewhat compact, I opted to drill a hole in each post at the desired height and put a steel rod through it.  Took keep the frame together and my initial belief that this would help the material over the arm move over it better, topped it off with two elbows.  Yes, I did measure the distance between the two posts before drilling the bottom holes so the two elbows could fit between the gap.  Next up was to add the motor.  Most wiper motors you see out there are full 360 motors that can easily be turned into a 180 range of motion with a two piece linkage.  My brother Ron was able to find wiper motors (think out for a Honda) that only have a range of about 165.  This is absolutely perfect because you do not have to worry about the linkages crossing over each other.  Aluminum stock was cut for the first linkage off the motor.  Attached to that was the arm made out of 3/4 PVC.  You need to make the arm long enough to remain on the support rod when the motor linkage is at its furthest point  – used my own arm as a reference.  Here it is with a temporary arm in order to get feel for how it will look.

Project Grave Grabber Halloween 2017

For the most part, most wiper motors are way too fast for direct use in a Halloween prop.  You don’t realize how fast it really is until you have it hooked to a smaller arm – downright dangerous.  There are easy ways to control the speed.  I picked up a bunch of 12-40V pulse width modulation units from Amazon (<$9) and inserted one between the power and the motor.  This allowed me to set the arm speed to whatever I wanted.  Opted to put this in with Molex connectors so I could swap out easily if it went bad – pretty sure these things come right from China.

Project Grave Grabber Halloween 2017

Lucked out at Joann Fabrics and found a very nice set of hands and a skull on sale for 50% off.  To my surprise they had both left and right hands!  Most of the time at the cheap Halloween outlets they will have a pair of hands that are both one side or the other because they cheap out by not making two molds.  These were also made of stiff rubber giving them a nice weight – very important for the next addition.

Project Grave Grabber Halloween 2017

This is one of the enhancements over the Haunt design.  I wanted the grabber to have extra motion to give it more flair.  Since the arm is being pushed out by the motor linkage, it occurred to me I could use that motion to add additional movement in the hand.  By simply tethering the hand to the frame, the hand could be raised as it extends out.  This idea required a new wrist linkage to allow it to go up and down easily.  A few hours rummaging around Lowes resulted in the perfect solution – door hinges.  A mending bar was placed on the end of the arm PVC in order to bolt one side of the hinge.  The other was screwed into the bones of the hand.  Now it could move easily up and down – note, I had left the ends of the bones a small distance away from the pipe so it wouldn’t impair the movement when it came down.

Project Grave Grabber Halloween 2017

Now it was time to put the head and rest of the shoulder structure on.  Another plug was place further back on the board to hold the torso frame.  Like the Haunt version, I kept the right arm fixed and attached it to a cross piece on top of the head post.  To keep the covering out of the linkages, constructed a shell structure that mimicked where the shoulder would be for the moving arm.  A 45 connector was added to the right arm so it looked like it was leaning on the ground in order to reach out.

Project Grave Grabber Halloween 2017

The other motion in this decoration was the raising and lowering of the head.  This motion was also designed into the Haunt version.  The motion of the main linkage already provided the needed mechanism to raise and lower the head – basically a back and forth motion.  All that was needed was a mechanism to allow the head to rotate on the cross pipe.  To Autocad Fusion 360 we go.  Quickly worked up a tee on a ring that could rotate freely over the 3/4 pipe.  Fired up the 3D printer and presto an easy linkage solution.  Tied a piece of string on the small end of the aluminum bar linkage (guessing you were wondering why I left those two inches on the bar).  That would pull up the head as it rotated forward which happens to be the same time the arm is pulled in the farthest.  The fact that the arm went a bit past 90 degrees to the head linkage gave a nice bonus effect of dropping the head slightly and bringing it back up before the arm started back out again.

Project Grave Grabber Halloween 2017

Here you can see the hand being raised as the arm extends out.  I simply tied the string to a finger to make sure the motion would work – later swapped it out for fishing line so you wouldn’t see it in the dark.  You might also notice that the arm doesn’t simply extend out in a straight motion.  Due to the linkage, the hand actually extends out at an angle to the frame, the hand lifts up and then swings all the way to his right before dropping the hand as it pulls back – absolutely perfect motion for this grabber.  Note it made a bit of a clunk when as it moved within the frame.  Ended up hot gluing some foam on the upright posts which totally damped the unwanted noise.

Project Grave Grabber Halloween 2017

Eager to see how it was going to look, put the clothes on.  Basically a piece of heavy cloth Linda and I found at Joann’s when we were picking up material for the witch circle (oops, forget you read that, accidentally foreshadowed another decoration in an upcoming post).  Totally stoked at the progress.

Project Grave Grabber Halloween 2017

Next up was to add some cool touches to the skull.  Nothing says creepy like glowing yellow eyes.  Whipped up a pair of LEDs in parallel and drilled out holes in the eye sockets.  Took me forever to feed the wires from the LEDs out a small hole I made in the base of the skull.  Slapped a 4 double A holder on the leads and presto – creepy eyes.

Project Grave Grabber Halloween 2017

Slip the material on to cover back up all the electronics and frame and turn on the motor.  Here it is with the arm pulled in  (notice this time with the fishing line on instead of the yellow twine).

Project Grave Grabber Halloween 2017

… and now with the arm extended (head down).  You can also see it half way through the movement over to the right side.  Ladies and gentlemen you now see the latest addition to the Haunted Trail – a new and improved model for a grave grabber.  Big thanks to the Yard Haunt for providing the inspiration.  To tie the two post together, the Tombstone document in the previous post was meant to be behind this guy – get it now, Al Be Back as in the grabber is back from the dead and thus multiple dates.

Project Grave Grabber Halloween 2017

Okay, now for a bit of post mortem.  In the chaos which is the Haunted Trail build the tombstone ended up somewhere else and not sitting behind this grabber as intended.  We also discovered that the material would bunch up at the cross bar as it was pulled back.  This caused it to struggle to push back through.  When we noticed it, we were able to pull it back out and it would work for a while until bunching up again.  This will get corrected for next year – probably put a piece of plastic on the top of the frame so it moves over smoothly.

Hope you enjoyed my tutorial on the new creation for the haunted trail.  Definitely better looking than the one last year – just need to incorporate a few more design elements to get it running as smooth as I want it to.

3 thoughts on “Project A Better Grabber”

  1. This was a fantastic new animation, and people at the party really liked it. I think we found that someone (not me) had placed it on a slightly sloped piece of ground, and that was interfering off and on with it extending out and back in. No idea who did that. None.

    The clothing was a bit tricky to stay free from the linkage, but it was a definite improvement over last year’s grabber (which you also fixed this year so it wouldn’t have that problem).

    Anyway, a very nice new decoration! And I have to admit that I did not connect the multiple dates on the tombstone to multiple resurrections and returns to the grave. Oh, well.

    Ron

    Like

  2. I will take responsibility for the placement. It took a bit to figure out what was going on – likely due to being completely exhausted by then. I’ll devote some time to addressing the clothes issue. I think it will be easy to fix with a small piece of plastic extending out from the arm post.

    All that time thinking up that tombstone all to be lost – oh well, my plan is to make a lot more of those .. starting much earlier in the year .. I’ll try to make those more intuitive,

    Thanks for commenting!

    Like

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