Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Capstan winch practical for long 2,000' towing up 1,000'?

  1. Jul 3, 2015 #1
    Exploring practical options for towing a small/light flat bed trailer up mountain side that while flat at bottom gets progressively steeper until almost vertical right before it rounds out cresting at the top.

    Maximum design load not to be exceeded, not including trailer weight which has not been selected yet, is 2,000 lbs of building supplies secured onto trailer bed. Total distance travel will be 2,000' from bottom to top that's at an elevation 1,000' above.

    I was looking at anchoring rope or cable (if any capstans do steel cable) at the top and having the gas powered capstan be secured in the front of the trailer with a roller guide for the rope/cable to run through on top at the front of the tongue of the trailer. But, that might be a little too much excitement for the operator, so let's just figure the engine/capstan is anchored at the top, pulling the trailer up.

    I started thinking capstan winch cause drum winches become less effective as their drum fills up and it's near at the end it would need to be most effective. Some of the capstan winch outfits talk about limitations on rope length of 500-600' because of stretch. Some talk about different or larger ropes less so.

    If above might be practical, what minimum size combinations of engine/torque/capstan/rope should I be looking at? Is steel cable even an option with any capstan rigs?

    If above is impractical or not advisable, what might work instead to accomplish the task?

    Thank you for your response.
     
    Last edited: Jul 3, 2015
  2. jcsd
  3. Jul 3, 2015 #2

    berkeman

    User Avatar

    Staff: Mentor

    Thread closed temporarily for Moderation...
     
  4. Jul 4, 2015 #3

    berkeman

    User Avatar

    Staff: Mentor

    Thread re-opened for a bit. This is a potentially dangerous setup, so we need to keep safety in mind in the discussion.
     
  5. Jul 4, 2015 #4
    Achieving safe workable design was point in posting here, as I'd ended my original posting with;
    "If above is impractical or not advisable, what might work instead to accomplish the task?"

    In the meantime...

    I took another closer look and there is possibly another place to go up with some clearing work first
    that, while length of rope/cable (2000') and final elevation gain (1000') are the same, it's a much more
    gradual slope all the way without an, as extreme, vertical near the top. I'd figure worse angle there, at
    near the top, is 45 degrees. If I can keep trailer under 1,000lbs, then combined with maximum load atop
    it of 2,000lbs, I'd be looking at 3,000lbs maximum rolling load.

    What do you figure my winch, be it capstan or drum, needs to be, with safety margin, as a minimum for
    max pulling force and/or rated lifting capacity?

    Thank you for responses.

    - Shane
     
  6. Jul 4, 2015 #5

    Baluncore

    User Avatar
    Science Advisor

    You cannot use a drum because of the cable volume involved. Selection of the correct cable lay will be important.

    A motor and capstan on the cart would work with a wire fixed at both the top and bottom. The cart would be dangerous and should not be ridden by the operator. There would be energy stored in the elasticity of the wire. If the wire snapped it could be lethal if anyone was nearby. The cart should retain the wire in a way that cannot disengage the capstan.

    A system with a loop of wire and two carts that pass at the half way mark might work with a motor and capstan at the bottom. When the top cart is emptied, fill it with rock to help bring the other cart up. That is more like a balanced cable car system and would need less power from the motor. Does it actually need a motor or could filling the descending cart with rock be sufficient? Maybe that can be done with a single length of wire through a pulley at the top.

    It might be cheaper to hire a helicopter when available at an offpeak rate.
     
  7. Jul 4, 2015 #6
    What sort of service life are you looking to achieve? I would look into the use of one of the Spectra ropes as opposed to steel cable. The Spectra or any of the other alternatives (all of the 12 strand single braid lines be it the red, the grey, or the blue just look for urethane coated single braid) are far lighter and much easier to attach and spool. They also are stronger then steel and more forgiving if misaligned or kinked. In either case the closer you can approach a balanced system as Baluncore noted the easier the system will be to power.
     
  8. Jul 4, 2015 #7
    Best maybe to endure more trips by dropping the combined trailer weight and maximum required load to under 700 lbs by using this...
    http://www.bikesatwork.com/bike-trailers/specifications

    bike-trailer-dimensions-series-awd-length.jpg

    It's toughest configuration is rated for handling maximum 600 lbs of cargo and that particular trailer itself weighs just 70 lbs.

    If we went that route, do you see any reason why this capstan winch http://portablewinch.com/en/products/PCH1000.html
    rated at Max. pulling force 775 kg (1700 lb) and Rated lifting cap 250 kg (550 lb) couldn't readily handle worst 45 degree incline?

    I'd just have to figure out a skid plate for it for whenever the tongue was on the ground. The tires can be placed more forward or
    back and loads situated so that we could strive to keep tongue from excessively scraping. That'll take some experimentation. Also,
    lowering it straight back down hill will probably be a challenge, but most any trailer we'd use probably would be, too.

    What do you think?

    - Shane
     
  9. Jul 4, 2015 #8

    Baluncore

    User Avatar
    Science Advisor

    There are some questions that will restrict the possible solutions.

    1. What is the total mass that will be lifted to the top?
    2. What is the heaviest single component that must be raised to the top?
    3. From that the range of the number of trips needed can be calculated.

    4. How many seasons will the system need to operate for?
    5. Will the system be kept in place to serve the summit structure after construction?
    6. What is the geology, vegetation, soil, climate and rainfall etc?

    7. Is this a commercial or an amateur venture?
    8. What budget is available?
    9. Is this a remote location?
    10. Do you really need to do this?

    11. Do you have access to two labourers, one to accompany each of two carts?
    12. If more or less labourers, how many?

    13. What is the “roadway” material and surface stability?
    14. What sources of local energy are available to drive the system that raises the cart(s)?
    15. What is the availability of rock, water or other disposable counterbalance mass on the face?
    16. Is wind or water energy available?
    17. Can you perform the lift in several shorter stages?
     
  10. Jul 4, 2015 #9
    Appreciate all the comments, at this point I'm really zeroing in on what I'd posted in my last, #7 above, posting.

    I'd only add that I'm looking at Samson Stable Braid in 1/2” diameter, it's a double-braid, 100% polyester rigging
    rope with "exceptionally low stretch" they say, and a breaking strength of 10,400 lbs. It's been used and praised
    by other owners of same capstan winch specified above.

    That reduced load and requirements on winch and rope and reduced cost of all components is attractive, if it'll
    both work and with sufficient safety margin. My intention at this point is, with capstan winch anchored atop, I'd
    draw up the cart. An available option, for little additional $, I'd likely do, too, is to get second set of axle/tires so
    it's much less of an unstable rickshaw. And, while getting rig back down hill can be down in a very slow speed
    controlled manner, steering could likely be an issue requiring trial & error experimenting with it.

    As described in post #7 above, along with what I've also shared here, does this set-up look like it oughta do the
    job and with a sufficient safety margin?

    - Shane
     
  11. Jul 5, 2015 #10

    Baluncore

    User Avatar
    Science Advisor

    No. You are dreaming.
     
  12. Jul 5, 2015 #11
     
  13. Jul 5, 2015 #12
    Can you be any more specific on any of the reasons why?

    - Shane
     
  14. Jul 5, 2015 #13

    Baluncore

    User Avatar
    Science Advisor

    Either:
    One person is needed at the capstan to control the system, while one is needed at the cart to solve navigational problems.
    Or:
    One is needed at each of two carts to shovel gravel into the descending cart as the slope changes. The operators can swap places half way at the crossing.

    It will therefore take at least two people, both of whom will be on the line of the tension member. They are exposed to both the elastic recoil and to a falling cart load of material. Communications will fail and there will be problems. Keep in mind that a cable system like that is evil and has only one aim in it's existence, that is to kill you. You will survive if you always assume it is just waiting for you to turn your back or momentarily lose concentration.

    I don't think you appreciate the effort needed to handle 2000 feet of cable or rope. You need to study cable logging techniques and ways to install the lines. They use multiple fixed and moving cables.
    You could install a fixed wire and then have a powered cart that climbs that wire with a capstan or pinch system.
    You could have a moving wire attached to the cart, with a capstan at the top, but where does the used wire go?
    You could have a moving wire with two balanced cart loads, no power or capstan is needed.

    Any synthetic cable will wear rapidly in presence of UV and abrasive dust on a capstan. It is an expensive investment in string or wire.

    Capstans are safer than drum winches on 4WDs but only when the cable is short and the operator is on the uphill side. Capstan winches are praised by 4WD operators, but they are usually only toys.You need a real capstan winch from an older mil-spec 4WD or truck.

    I think you are too eager to embark on an unreasoned solution to do it safely.
     
  15. Jul 5, 2015 #14
    Thank you for your expanded comments, I appreciate it.

    If I proceed, it'll be one cart, one cable, pulling one load up at a time via winch at top. KISS principle, best as possible.
    All hands involved will be briefed on dangers, duties, safety protocol and comms distributed and tested beforehand.
    Rope coming from capstan will be rolled onto big drum as it arrives, to minimize mess re-deploying it later for downward return trip.
    Cart going back down for next load will always be empty, weighing 70 lbs for any tender walking alongside and needing to help steer it.
    While you've said that "Capstan winches are praised by 4WD operators, but they are usually only toys.You need a real capstan winch
    from an older mil-spec 4WD or truck." and while that'd be great, the more robust the better, anything that gets onto that mountain initially,
    before first cart load up, has to go up on our backs and it's steep. We'll have our hands full first time taking 42 lb capstan winch, fuel and
    all the anchoring gear and then laying all that 165 pounds of cordage from top to bottom before our first cart pull tests with dummy loads.

    Anyways, while clearly not as robust as desired, and that much rope is nightmare potential, I'd still like opinions from anyone re the following:

    Is it likely to work, that a maximum 700 lb cart load can be pulled 2,000' with 1,000' elevation and maximum 45 degree slope, with this capstan
    winch http://portablewinch.com/en/products/PCH1000.html that's rated at Max. pulling force 775 kg (1700 lb) and Rated lifting cap 250 kg (550 lb)?

    - Shane
     
  16. Jul 5, 2015 #15

    Baluncore

    User Avatar
    Science Advisor

    So the operator at the top must maintain tension on the capstan tail rope and spool the used rope at the same time?

    I would instead mount that winch on the front of the cart and let it climb a fixed rope from bottom to top. No spooling of used rope is then needed, there can be no tangles. Also, the winch gets itself and fuel up the hill and the system can be operated by one person if necessary.

    That winch has a cylindrical capstan. It is much better to use an hourglass shaped capstan so the rope can creep diagonally away from the wall without being tightly pinched against adjacent turns.
     
  17. Jul 5, 2015 #16
    I've seen some spooling a drum where, correctly positioned, that was how they were also providing the modest tension on the capstan tail, while standing just as close, within reach, of the capstan normally.

    First go-arounds with any set-up I'll have more than enough people on hand as we test and sort out best practices.

    I'd wanted originally to start off doing exactly as you'd mentioned; "mount that winch on the front of the cart and let it climb a fixed rope from bottom to top." and likely will still later, but initially, for safety while sorting everything out, I think we'll avoid having anybody in or around heavily loaded wagon climbing up the steep inclines. Definitely, after heavy loads have been delivered, I look forward to be able to single-hand with the winch in the cart, as my primary way of commuting up & down. Need to also see any issues resolved with downhill steering first, too.

    One good thing, in the meantime, about all the line collected atop when cart arrives, is that it can then be stowed out of the weather till next needed.

    I'll check and see if any reported issues with capstan shape, thanks.

    - Shane
     
  18. Jul 5, 2015 #17

    Baluncore

    User Avatar
    Science Advisor

    "Best Practice" kills people. You need to sort out "Safe Practice".
     
  19. Jul 5, 2015 #18

    berkeman

    User Avatar

    Staff: Mentor

    I think Baluncore's warnings are good advice. Good luck, and please be careful. Thread is closed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Capstan winch practical for long 2,000' towing up 1,000'?
  1. Winch Motor (Replies: 4)

Loading...