|Nov 12, 2012, 09:37 AM|
How to make a tow winch
I will share how to make working tow winches.
Please hold the comments untill Im done
The winch we will be making will mount under deck, and use the scale tow winch on deck as a pulley. This replicating the scale winch doing the work, but its..faux is the good word. It turns and everything with the line, but its really just a guide pulley.
In real life the winches are pretty slow. So it's usually better to speed them up a little for our models. Too slow and you wont even notice it and it will be no fun to use. Its a time space continuminum thing. How time speed up the smaller you get. But lets not get int that lol.
The winch we will be making uses a HS-81 Sized servo, which is good for smaller boats.
Making the winch is pretty simple and you only need a few things:
In this case we will be using a servo as a gearbox. it turns about the perfect speed too. for larger ships we would get a gearbox and motor combo. There are hundreds to choose from. A simple Ebay search will pull up a ton. Ideally you would want like 20 RPM or so. This can also be adjusted by the voltage so its flexable up or down somewhat
You need something to spool the tow line (Hawser) around.
I have a new concept to try here so it will be somewhat of an experiment.
So first things first, the gearbox
To get the servo to continuously rotate,we need to modify the pot, and remove any mechanical stops that it may have. All servos are a little different but basically you need to do the same thing. Some lend themselves better to this mod than others.
Disassemble and remove the electronics board. If the servo has an IC soldered straight to the motor (Futaba 3003's,S-148 etc), then you have to cut or unsolder it.
I'm using an expensive digital metal gear micro servo I burned up (not the motor obviously or it would be true junk) Its a beautiful piece of equipment! and I have paint and casting resin all over my hands, sorry.
Is that beefy or what. Such overkill. I love it. Very fitting for a winch!
after we're done drooling over the internals, we take the pot out and pry out the wipers and any other pieces that prevent it from turning all the way around
now it turns smoothly
it can then be re installed. Notice I have removed the electronics board and wiring. None of it is needed anymore so get it out of there.
|Nov 12, 2012, 09:49 AM|
Then solder some leads on the motor
We can the re-assemble the servo. luckily this servo had no mechanical stops on the gears. Most servos do, and they need to be cut off and filed down smooth.
Now you can try and figure out how to put the transmission back together. Prudence dictates that we take a picture before we take it apart, but that's no fun. Fumble around with the tiny gears untill you make them fit!
HINT: The smaller and finer the teeth, the closer to the motor they go.
Ok, lets call the servo turned winch finished. Now we have to make the spool. I know you all don't have a lathe. Thats why I will be selling these spools you will see very soon. or you can cobble something together.
But lets use the lathe and get going. you wont have to do this part but i will show how i did it.
We need the horns to start with
i drilled the screw hole in the arm out to 1/8", just a hair bigger than it already was. And then inserted a metal rod
Then I drilled a 1/8" hole with the drill press in a piece of MDF. This will hold the rod pretty true vertically.
The idea is we are going to cast this servo arm in a round block of resin, and then put it on the lathe and turn it into a spool. Our finished product will have the splines and strength of the nylon arm and the spool in one piece.
To be continued in a bit!!
|Nov 12, 2012, 10:35 AM|
Remember I said there was no mechanical stops in this servo. well I knew that was kinda strange... So I plug it in and you can guess what happened, it stopped.
See it! I didnt at first. Just was not paying enough attention
Its best to NOT us sanding or grinding equipment here. All the grindings stick directly to the greasy gears and you have to strip and clean everything with solvent. Pita. So use flush cutters of a razor knife for work in this area. And debris you get in the gear train will be really annoying in a clicking sound and possibly jam it up! Notice I'm working on a new sheet of paper. Thats my verson of a clean room and you can follow my example of suffer the consequences
Well on to the spool
The MDF piece of wood gets covered with a piece of packing tape. This prevents the resin from bonding to the wood. FYI Almost nothing really sticks to this tape, unless you scuff it up. Then I hot melt glue a 1" diam piece of PETG tubing in position, and eyeball center it over the servo arm. This does not need to be perfect as it all gets turned down on the lathe later.
Filled with casting resin.
While its still liquid it gets put in the pressure pot and blasted up to 65 PSI. This will eliminate the almost microscopic air bubbles that are trapped and form in the resin.
|Nov 12, 2012, 12:03 PM|
Turning the spool
Now the billet has cured and is ready to machine.
You can see the nylon control horn splines in the casting. No resin got in there! That's rare but I'll take it. Usually you have to clean the splines out with a pick.
First is to machine the face with the control horn.
Next machine the OD (outer diameter) down to the size we want.
Then we start the cutting of the spool shape
Then I smarten up and stick the shop vac hose in there so my face is not getting covered with tailings
Thats about how far we go.
Looks like a spool
|Nov 12, 2012, 12:06 PM|
The we gotta bore the center so the servo screw will fit.
I do this by hand. Easy and you have a lot of control. If you bore all the way through you're screwed, there is nothing for the servo screw to seat against and you cant hold the spool on.
There's our winch!
This one is going in the little SDM tug.
Next we do the installation of the hawser pipe, (the tube that the tow line goes through to the deck and scale tow winch) And then the electronics side of it.
I have a few simple ideas on control that are "safe". Meaning that if, or rather when, you leave it running it wont damage anything. Or pull the rope through under the deck so you have to fish it out.
To be continued
|Nov 12, 2012, 12:24 PM|
Any comments or ideas, go for it
I got this thing mounted up too high in the SDM, spool is hitting deck. So I'll be figuring that out for a bit
|Nov 12, 2012, 12:34 PM|
|Nov 12, 2012, 04:28 PM|
The brass rod you put in the servo arm, I would sleeve it up in diameter to a size where the screw will fit, then that eliminates a step and the risk of drilling too far as well.
|Nov 13, 2012, 05:05 AM|
Very cool Rick! Have you put the drum on a scale and tested to see how many ozs. or lbs. of force it will take to start unspooling the winch?
|Nov 13, 2012, 09:38 AM|
Besides I was only showing how I personally build stuff like that. I will be selling the spools of various sizes for a couple bucks each so nobody will have to build one unless they want to.
Troy: Thats part of the wiring scheme. The winch's wire leads get crossed via the switch effectively putting it into brake mode so it wont play out under tow. It holds way more than the tug can dish out. The bigger and more powerful the tug, the bigger the gear ratio winch you'll use and the effect the brake will have.
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