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What's the best way to attach tentacles at front of a harness and have the controls feed backward?

I'm in the thick of prop and scene creation for a middle school production of The Little Mermaid.

I am also making the tentacles for and altering a dress for Ursula. We have a student puppeteer who will control a couple of the tentacles. Though, I've gone back and forth on having Ursula control the (2) tentacles in front by movement of her arms or actions with her hands. (not sure if this is a good idea or not). Then have puppeteer control one tentacles over each hip — keeping the (4) remaining tentacles at the back non-mechanical/without motion.  What is the best way to attach the tentacles allowing for best control and motion? Should the puppeteer handle ALL of the mechanical tentacles and keep Ursula's hands free? The dress for Ursula is very floofy and strapless (not my choosing) so I'll be adding a strap around the neck. She will be moving around and using her arms/hands for creating potion in cauldron, etc.

Suggestions welcomed…

What will be the best way to attach the tentacles to a harness and feed the cables to the appropriate places?

What should each mechanical tentacle be sleeved before incorporating into the fabric skin?

Answers

  • Chris EllerbyChris Ellerby Los Angeles Admin
    edited April 2016
    Hi Laura,

    I would try and keep the performer's hands free, and allow them to focus entirely on their performance.  Typically when a performer is asked to play a role and perform an additional task both suffer.

    One option I've seen before is to have the forward tentacles attached via monofilament to the performer's wrists, so as they move their arms the tentacles mirror that movement.  This is a low tech approach that is very reliable, though not as impressive as puppeteered tentacles.

    If you do choose to have puppeteered tentacles I would have a single puppeteer handle them all.  You can link the cable controls so one joystick controls multiple tentacles and flip the X/Y cables of a couple tentacles so they appear to be moving in a different manor.  That way 2 joysticks can easily control 4+ tentacles.

    It's important that they are firmly attached to the performer so they don't flop around, and a solid base also helps with the tentacle movement.  A fiberglass harness is ideal for this, as it's light weight and rigid enough to support the weight of the tentacles, which should be kept as light as possible.

    Depending on the design I would probably attach the tentacles to the fiberglass via carriage bolts, with the smooth side facing the performer and covered with padding, moleskin, etc.  Then you can use wing nuts to bolt them on.  That way you don't need any extra tools to quickly remove and service a tentacle.  The connection point can be camouflaged with wardrobe.

    The cables can be run down the performer's leg, hidden under her dress, or run through a static backwards facing tentacle towards where the puppeteer is stationed.

    One thing to keep in mind with this approach is that your performer is tethered.  And the longer your cables get the more force will be needed to operate the tentacles.  So if Ursula needs to move around the stage a lot, you may need a reset where the puppeteer can move the rig.  Also think about entrances and exits for the character and how those would work while tethered.  

    You also want the harness to be easily removable so your performer can get out of the rig during resets, wardrobe changes, bathroom breaks, etc.  The cables between the controls and the tentacles are typically permanent, so having the harness be easily removable is important so your performer is not permanently tethered.

    You can skin the tentacles with spandex prior to sleeving them with the fabric of your choice.  You may need to incorporate foam disks or padding to give you a smooth outline and prevent the fabric from bunching or buckling.

    Hope that helps!

    /Chris

  • Thank you for all of the information. It certainly helps me better visualize how to rig the harness and cabling.

    I've been debating the type of tentacle to build…compression spring vs. disc vertebrae (probably from wood since I can make them more easily). Which do you think would be most reliable and cost effective…and provide the best tentacle?
  • Chris EllerbyChris Ellerby Los Angeles Admin
    It depends a bit on what type of movement you want.  If you just want simple side to side movement you can get away with a much simpler/lighter design.  The more complex the design the more chance there is for something to go wrong, which can be challenging for live shows.

    Below is an example of a tail by Rick Baker that was covered in foam.  You can see the guides on this side (mirrored on the other side) for left/right movement via cable.



    For more complex tentacles, I'd suggest watching something like this lesson which covers the basics:

    https://www.stanwinstonschool.com/tutorials/animatronic-tentacle-mechanism-basics

    If you go the disc method, just keep in mind that wood can be a little heavy and is subject to wear.   If you can use a material like delrin that might be a bit more durable for you.

    /Chris
  • Chris, I appreciate the time you've given me in your responses today.

    I've watched the tentacle-mechanisms videos numerous times in the last week to study the construction and figure out what would be the best solution for the Ursula costume/tentacles. That coupled with trips to the hardware store, researching various products/cost availability online. Many of the items in the video are not available locally and I prefer to physically handle the materials before purchasing — helps me think through the process a little better. So, I've gotten a little stuck in committing to a particular construction/mechanism.

    On the example you posted of the Rick Baker tentacle, are the guides available as off the shelf items or are they individually machined? Are the thicker pieces where stops/termination points are located?

    Is the delrin easy to cut through with a chop/miter saw or require a special blade? Is it okay to pre-drill the holes before cutting the delrin into discs?

    I keep coming back to the compression spring construction since it has fewer parts involved, but feel the movement of the vertebrae construction will be more fluid.

    Hmmm…

    BTW - I love the tutorials!
  • Chris EllerbyChris Ellerby Los Angeles Admin
    edited April 2016
    Happy to help!

    In Rick's design they are likely custom machined, but any kind of eyelet or loop would work.  The cable moves freely and is only attached at the tip of the tail.

    Delrin is very easy to cut.  Any wood cutting blade will work, you just want to keep the speed down and move slowly so you don't generate too much heat and start melting the plastic.

    The compression spring method will work as well, it's just a matter of picking a method you are comfortable executing that will work for the effect you are going for, the tools and materials you have access to, and your budget.

    I hope you can share some progress shots with us here on the forums!

    /Chris
  • With regards to mounting the tentacles and easy removal / fitting of the outfit, this FX corset harness tutorial might be of use to you.
    https://www.stanwinstonschool.com/tutorials/fx-corset-harness-character-creation-tutorial


  • Thank you Stuart, that was my next question.
  • edited April 2016
    On the harness & fiberglass mount…would the cables run through a channel of some sort — picking up the cables from each tentacle — moving from front to back? Do you have a photo of how that would look?
  • Chris EllerbyChris Ellerby Los Angeles Admin
    You would want to run all the cables from each tentacle to a single point, typically the performer's back or near a hip to run down the leg.  Then you can run them down to the ground through/under wardrobe or disguise them as a static backwards-facing tentacle.    All the cables combine to form a single umbilical that trails behind the performer.  This can be held together done with zip ties every few inches, or by having all the cables in a sheath. 

    This photo shows control cables coming out of the performer's leg.



    I don't have any examples showing cables being routed radially around the performer, but they are fairly easy to route.  The one thing you want to avoid is having them bend to sharply, as that can make moving the tentacles more difficult.

    The more cables you have, the more difficult routing everything will be.  If you want to reduce the complexity of the setup you can have some tentacles only move up/down or left/right.

    /Chris
  • Stuart McconnelStuart Mcconnel UK ✭✭
    edited April 2016
    I recently bought a whole bunch of cables from the US (the shipping cost was almost enough to make a grown man cry, but alas, they are virtually impossible to obtain in the UK at anywhere near comparable prices) and most of them specify a minimum bend radius. Obviously, the thicker the cable, the wider the radius of sweep that is required. I suppose the transition from the plate to the tentacle is going to be the trickiest part. Fortunately, as tentacles are a pull-pull mechanism, the inner cables don't need to be excessively thick.
    I don't know what sort of cables you're intending to use, but as a reference, if it's of any use, this link has the minimum bend radii vs cable diameter for Sullivan cables.
    I guess they ought to be comparable for any type of cable, however something like bicycle brake cable I think usually has a coiled wire sheath (which is quite stiff) coated in plastic, so will need a considerable radius.

    http://www.sullivanproducts.com/GoldnRodMainFrame.htm

    Edit:
    I just looked up Ursula from the Little Mermaid and seeing where those tentacles are, the bend radius might not be of huge concern as they likely won't be protruding perpendicularly from the fixture plate.
    Oh well, hopefully the above information is still somewhat informative :)

  • Chris EllerbyChris Ellerby Los Angeles Admin
    Stuart is correct about the expense of the cables.  And with the lengths needed for this type of project the cost will add up. 

    I'll provide a hypothetical example for this project based on a lot of assumptions. 

    4 tentacles, each 5 feet long.

    The performer's hips are 3 feet from the ground.

    The puppeteer needs to be 20 feet away from the performer to be hidden off stage and allow the performer enough room to move around stage and hit their marks.

    Each tentacle contains 4 cables.

    4 tentacles x 4 cables each is 16 cables.

    Our distance is 5 feet (tentacle length) + 3 feet (height off ground) + 20 feet (distance to controller)   And we'll add 4 feet to allow for cable routing on the performer end and on the controller end as a safety.

    That's a total of 32 feet

    16 cables x 32 feet is 512 feet of cable.

    If you limit the design to bi-directional tentacles you can get by with half the number of tentacles.

    8 cables x 32 feet is 256 feet of cable.

    If you limit the design to a single pull cable per tentacle with gravity return you can reduce that further.

    4 cables x 32 feet is 128 feet of cable.

    This type of cable is typically called "Bowden cable," which should help in your search.

    The housing and inner cable are often purchased individually.

    Because this quantity of cable is typically for industrial/manufacturing industries most sellers don't list prices, so you'll need to request individual quotes to get a total cost estimate.

    You could probably expect a cost of around $2 a foot.  But that's just a rough guess based off a couple places where I did see prices listed.

    Here's one placeI found https://www.cccables.com/

    My personal applications are typically small enough to use cables like what Stuart found, which are intended for radio controlled aircraft.  They are small and ideal for things like animatronic character faces and light duty applications.  I'm using that type of cable for my animatronic Skeksis.

    I'm using heavier duty cables for that project as well (head/neck control), but the lengths are minimal enough that I was able to use standard bike break cables.

    Your minimum cable length in the hypothetical example above is 32 feet, which is longer than you'll find for non-industrial applications.  Once you go over 10~ feet you are looking at buying the cable and housing by the roll.

    One option, which I hate to suggest as it's so prone to issues, is to make your own cables.  This can be done using drip irrigation tubing and steel cable or fishing line.  I would not go below 200lb rated line, but you may need more depending on how much force is required at the controller.  

    Other down sides are that the drip irrigation tubing does not have a coiled metal support structure inside so it will kink causing jams or increased friaction.  It also does not have a teflon inner liner so friction building up is an issue with longer runs, requiring more force and thus stronger line.  


    /Chris
  • I wonder if it would make more economical sense to use a radio and servos in this particular application? I don't really have a feel for what sort of servos would be required. I've been grabbing job lots of standard size ones on ebay for around £1-£1.50 a piece when the crop up as I need loads for my upcoming project. 4+ channel transmitters can be had very cheaply and a receiver only runs a few quid.
    But then you need a battery and some spares, a regulator. I guess it adds up going this route, too.
    If you go the route Chris suggested and make your own, I might suggest using 4mm nylon pneumatic tubing. It's slightly less flexible than irrigation tubing (but still surprisingly flexible), would be less prone to kinking and has much lower friction.

    I just did a test running Sullivan 0.032" brass plated stranded cable through about 20 feet of 4mm nylon tubing and the friction wasn't too bad. I think the large part of what friction there was may have been from the cable bunching up a bit in the tube ("S" ing) - the cable probably ought to be thicker (4mm tube has ID of ~2.5mm... 0.032" is about 0.8mm, so it is a very baggy fit).
    0.063" cable might be better.

    The exact tubing I tested with is Norgren PA2-0504100 which comes in 100m reels. You can also get it in 25m reels. It's pretty cheap but I don't know how easily you can get hold of it.
    http://store.norgren.com/uk/en/detail/pa2-0504100/nylon-tubing
    Just search for something like 4 x 0.75mm nylon pneumatic tubing (0.75mm is the wall thickness).

    What's your take on this, Chris?

  • This is about the sharpest bend you can make on it. Might be a little less with thicker cable inside.

  • Update:
    The cable I fed through the tubing was Sullivan S522 bulk cable kit. You get a good fitting sleeve with it. I managed to thread all 30 feet of cable into that sleeving, then fed that sleeving through 20 feet of blue pipe. The sleeving actually slides quite nicely in the pipe and the cable would probably be useable as a pull-pull system through the sleeving. I was able to fairly easily push it by hand with the whole assembly sort of straightened out. With a joystick, I reckon it would easily handle a few bends.
    The cable is $19 from Hobbylinc
    http://www.hobbylinc.com/htm/sul/suls522.htm
    But yeah... x8 is gonna get expensive. May be better using a thicker cable inside the tubing rather than a sleeved cable.

  • Chris EllerbyChris Ellerby Los Angeles Admin
    Nylon is a great low friction material, and would be a good fit.

    Servos with enough strength to move a big tentacle do exist, but they can be quite expensive.  Once a single tentacle is completed you could run some pull tests to see how much force is needed and then price servos that are rated a bit over that value. But with a skinned tentacle at the scale of a human performer you are likely looking at 20+lbs of force to move it without struggling at any kind of speed.

    Heavier duty servos are often quite slow, so that would impact the type of performance you could get.  Though I imagine slow undulating movement is probably ideal.

    A servo like this would be a potential fit:
    https://www.servocity.com/html/d945tw_servo__36945_.html#.VwLUwRMrLUI

    At roughly $150 it's relatively inexpensive for a heavier duty servo.  But for 8 servos (2 per tentacle as each could pull 2 cables, for 4 tentacles) you are looking at around $1200 USD.  And you would want at least 1 or 2 backup servo as the chances of one burning out during testing or the run of a show is a real possibility.

    /Chris
  • It's mad, isn't it. I never realised how quickly it all adds up for this sort of project. Must be awesome working with a studio budget!
    When I was watching the tutorial on making an animatronic eye mechanism and David Covarrubius stated which servos he used, I looked them up and they were about £70 a pop (~$100) for micro servos. I was like LOL I'm not putting 6 of those in an animatronic head just for the eyes!

    I really hope you can find a suitable solution that doesn't run an absolute fortune, Laura. I'd love to see the project come to fruition.

  • Chris EllerbyChris Ellerby Los Angeles Admin
    We are very fortunate that the cost of a lot of this stuff has dropped significantly in the last 5 or so years.   Today we have servos for just a couple hundred dollars that were well over a thousand dollars not that long ago.

    My current project has 12 micro digital servos that are very fast and very strong and they only cost me around $50 a piece.   But when you are buying 12 it still adds up!  (8 of those are for the eyes, 4 for each eye) 

    I'm sure Laura will be able to find a good solution that is well within her budget. There's nothing wrong with starting with a "blue sky" concept of the ultimate/ideal version of something and then narrowing things down to what is practical for time/resources/budget that still meets the ultimate goal of the project.   A bare bones scenario with two tentacles tied to the performer's arms via a length of monofilament can still look great.  Everything after that is just icing! :)

    /Chris

  • I appreciate all of the information. Needless to say, I'm a bit overwhelmed by the many options, not to mention the possible cost involved for a middle school budget.  :o

    Chris, thank you for breaking down the numbers. I've been stalling in hopes of finding a way to make it work with out busting the budget. Today I ordered 12" compression springs from Grainger. I'm getting 6 (2 packs of 3) for $43. (They also have Delrin that I could order for a 1 foot length with a 2"diameter for $21 should I choose to go the vertebrae route.) Tomorrow, I'll stop by a few local shops to see if I can salvage some steel spring strapping from shipping palettes. That will be my starting point and in theory I'll have fewer parts to worry about.

    Stuart, the photo with the cable and blue tubing is very helpful. The bending and binding while routing the cables to the back has been a concern. I think the most severe bend/turn would likely be on the four tentacles at the back…so I should be okay since the front four tentacles will be the only mechanical tentacles.

    I actually looked at the irrigation tubing over the weekend and priced out several cable options too. I am also building/painting a rolling backdrop that will help get the puppeteer closer to Ursula and hopefully cut back on the expense related to engineering lengthy cables for the tentacles.

    Once I start building, I will post photos on my progress. Though, I keep getting "why are you going to this extreme" for the tentacles…my answer is that I love the challenge of learning something new and problem solving. Thank you both for mentoring me.
  • Back at it…and regrouping. The drama instructor ordered a second dress/costume since the first one ordered had not arrived after an extended period of time. The dress arrived yesterday. It's strapless and we're adding 1" straps to help keep the bodice in place. The corset-harness I had started will not work with a strapless dress. To make the challenge even bigger the dress has a fitted drop waist—making it difficult to place the mounting hardware and stay sleek/hidden. Have you ever used an elasticized lumbar belt as a base for a harness when attaching tentacles below the hips? I would likely add the reinforced harness material/coutil/boning to make a short skirt for mounting the mechanical tentacle.

    In the next few days, I'll assemble the cabling and post a few photos. I'm crossing my fingers that it will work smoothly.

  • Chris EllerbyChris Ellerby Los Angeles Admin
    The challenge with something like an elastic lumbar belt is that it's not rigid, so anything attaching to it might flop around a bit.  But you never know!

    /Chris
  • edited May 2016
    Last weekend, the Little Mermaid show took place. It's been a very busy several weeks since I last made a post. I attempted tentacle construction with compression springs, cable inside tubing with hardware found at a combination from Lowe's and Home Depot. Ultimately the weight of all of it was overwhelming…not factoring in the HUGE dress worn by Ursula. The range of motion was not enough for my liking, so I pursued a new design based off of the plastic finger/hand. My daughter who played Ursula, had actually done a science project somewhat similar to the finger/hand design. It used soda straws, strings and modeling clay.


    I went to a local appliance store and asked to salvage a variety of drain tubes from the backs of dishwashers. A great way to experiment, see if it will work and find the right density/flexibility, corrugation of tubing…as well as a great way to stink up your car with residual water in the tubes. Circular holes were cut into several of the salvaged tubes.I eventually found that an oval…elongated shape provided the best movement. Each tube was about 4'6" with 10-11 holes. I used 70# fishing line and tied one end off at the last hole, then ran the line inside the entire tube. No stops or tying off, though I did try putting stops in initially. The plastic to plastic did not allow for easy release/return to a straight position. With the holes providing directional bend and additional flexibility, plus the tube providing form/structure and casing…it worked well. The kids were in awe.

    Several hours were spent at the big box hardware stores, pool and spa supplies shops, trying to find an inexpensive option since there were 8 tentacles to fabricate. I did luck into a long section of salvage tubing that had been used as conduit -- so no stinky water. I made 6 tentacles of which 4 were operated by a puppeteer and the 2 in the back were static. Ursula's arms were counted as tentacles #7 and #8.


  • Chris EllerbyChris Ellerby Los Angeles Admin
    Glad you were able to find a solution that worked for you!  Do you have any photos or video of it yet?

    /Chris
  • edited May 2016
    Yes, I'll get detail photos of construction soon. Need to rebuild a few things. Always a learning process…which I love. Time has not been my own the last 3-4  weeks. Be patient…I'll get to the photos soon. We want to make adjustments to the harness and make it bit steampunk. Brief video below.
     
    https://www.facebook.com/laura.pichardmurphy

    Post edited by Laura Pichard-murphy on
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