www.Robse.dk - Thé internet site!!

RC models by Robert Holsting

HOME     Blueprints & plans About me Contact me

  Hooks, cables and winches.

There will always be sequences with spare time during a built as large as this crane, and I turn to detailing and small stuff during those.
I have decided that I want two hooks for my crane: A 200t and a 500t. A third much smaller hook may follow, but it is not part of the original plan.

I obtained drawings of real ram hooks, and scaled everything down to 1:13,5
The rest of the structures are my own design, inspired by pictures of real high capacity ram hooks.

  I need to make about 36 rollers for the wire, and for that I revived an old mini-lathe.
Note: A roller allows the wire to be "cut", eg you run it back up or back down. With every cut you increase the lifting capacity with 1 x (winch and wire capacity), so 8 cuts gives you 8 x (winch and wire capacity.) (Not to exceed general crane capacity....) But: Every cut eats away on your speed!
The crane head on the LTM 1500-8.1 has got 13 rollers, so it is possible to run the wire back and forth 26 times. Since the capacity is listed as 500t, then it must be at least a 19,2t capacity wire.. (26 x 19,2t = 500t)

  I cut the disks for the rollers from a sheet of 6,5mm nylon using my CNC, and then mounted each disk on a tool made for the occasion. It was then possible to make the grove for my cable in every roller, using a cutter that was shaped for this job only.

Why nylon? Weigh and to some extend durability. Aluminum and brass is heavy, and you don't want a lot of dead weight at the very tip of the crane..

  Then, a good while later, I could fit genuine ball bearings in the inner holes.

  Then the hook itself....
I started with the small hook, and got hold of a 15mm thick brass block.
Unfortunately I got MS63-brass, which is too hard for my CNC, so I could only cut the outline before the end mill left this world.
The rest of the hook was therefore cut and shaped by hand.

  Done! It's almost looks organic!

  A friend of mine made the shaft for the hook, and I topped it off making the spring loaded wire locks.

  Then I had a block made (that sits on top of the shaft) that will be fitted in the side walls using 6mm steel axles, so the hook can swing.
At the same time, the hook can also revolve, just like the real thing.
I set it up in a test situation, and tied a loop of rope to the hooks. I then stepped on the loop, and thereby loaded my 80 kg on the hook. It passed.

I plan to use this hook with loads below 20kg.

 

This is the block that the hook hangs in. Two steel shafts extrude into the walls of the main hook structure, and the hook is able to turn and revolve.
The brass is MS63 (The hard kind..)


 

All components for the 200t hook: Ram hook, rollers, wire separators, spacers, caps for axles / bushings, axles, bushings, sidewalls, nuts and bolts.

The sidewalls were made on my CNC in 5mm aluminum, and the four wire separators (goes in between the rollers) were cut in 1mm alu, also on the CNC. Outlines were reproduced from various pictures, and the actual design and measurements of my design. Now some paint, and fitting!


  After paint: Assembly! I painted everything dark gray, as black would kill the detailing.

Here I'm stacking the rollers, and the wire separators, and showing how the hook is attached to the main structure.

  Top view of the progress...

  -and done!

,   .. note that the hook has been rotated on this image..

,,   Total weight ended up at 584g, and I'm pretty pleased with the result of the 200t ram hook.


  With the small hook done, I turned to the 500t version. It'll be much larger, and much more complicated.
Again it all began with a program for the Mach 3 CNCN software, and a chunk of brass.

  This time it's a 20mm thick block of MS58 brass, and THAT I can cut on the CNC.
MS58 is also known as "engravers brass."

  I still have to proceed sloooowly, so it does take a while to eat through 20mm of brass.
The tools marks change appearance half way through because I had to chance to a long end mill half way through. Is IS one solid chunk.

  I then had to silver solder, as the shaft is a separate component. I had to use the weed burner from the garden as a supplement in order to get enough heat!

  Suddenly the silver flooded the areas covered by flux, and it turned out to be an excellent, strong solder... just like it must be in this case.

The hook was then shaped by hand, using ordinary files and sand paper, followed by dark grey paint.

  -and done!
Ready for some big time hookin'

  The hook can turn and swing, just like the real thing.

  Together at last!
The distance to the camera is the same, so perspective is equal. The hooks are turned slightly to show the markings, but sizes can be compared directly.

  Total weight of the large hook ended up at 1530g, while the smaller hook ended up at 584g.
Weight is important to avoid the wire from tangling during no-load operations.

  The larger hook; 500t version.

  The smaller hook; 200t version.

     

    I'll get back to this chapter later when it's time to build the hoists and choose a wire for the crane, but for now I'll place this section on pause..

     

     


Back to index --->