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RC models by Robert Holsting

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  Outriggers. 

The outriggers have been in the back of my mind for a loooong time, and I was kind'a waiting for an external vendor to have a free time slot for this project. I then stumbled over three steel profiles that were perfect for the job, so now I'm going to make the outriggers myself.

The span of the outriggers will be close to 26-28 cm on each side. The real crane spans 23 cm on each side, converted to scale. The larger the footprint, the better... so I am going to go with that.

  I will be using three different sizes of box profiles:

The first profile is 40x70mm (outside measurements), made in 3mm thick steel.
The second profile is 30x60mm (outside measurements), made in 2mm thick steel.
The third profile is 25x50mm (outside measurements), made in 2mm thick steel.

A series of cut-out's in the largest profile in places where it needs no strength anyway, will lighten the structure a bit.

  And here we go: 100cm of each size!

Now it's time for some new drawings in Inventor, and then some serious cutting!

  All elements are now cut to length, and the finer detailing can begin, as well as preparations for the inside mechanics so the outriggers can extend and withdraw by remote.

Here they are all mounted in the 4mm steel chassis as a small test. The footprint will be HUGE, which is great for the crane stability (Note the standard size beer can...).

  Brass (?) blocks will be added to ensure a tight(er) mechanical fit, but right now the elements sack and dangle wildly.

Crane weight, counter weights and the planned max load calls for an outrigger capacity of 25 to 30 kg each.


  First step: Ensure that the stationary element are 100% horizontal!
I had to fit all axles and wheels to perform that test. Result: The chassis and the stationary part of the outriggers does not list to one side.
Excellent, now we know that he base is in order!

  The stationary part of the outriggers will be bolted to the chassis with eight 3mm bolts each, four on top and four in the bottom.

 

The elements have all been cut in the front ends according to plan.
I then took the elements in the foreground and added spacers to the individual elements so they fitted one another. I then put them on some wooden blocks, and stepped on them! They carried my 85kg without any problems, so the planned load of 25 to 30kg each will not be a problem.

 


  Two brass plates are bolted to a couple of brass bars as shown. This will form the rear and of the outriggers, and serve as a base for the mechanics inside the outrigger. (Motor, spindle etc.)

  This is seen through the outrigger.

Why doesn't the inner plate extend all the way to the top? The empty space at the top will accommodate wires, hoses and such. I'll show you later.

  Fitted in it's new home!

And yes: If you look carefully you will see five outriggers in the picture. I made an extra, which I am using just for test and development. If an idea works, then is it copied to the four actual outriggers. This way I can keep my actual outriggers free of mistakes, extra holes, and errors.

  The outer plate can be removed to allow service to the gears, and emergency (manual) operation of the outrigger.
(Details shown later.)

  The outriggers sit right next to each other in pairs like shown, so I had to countersink one of the bolts.

  This is how they will be oriented, once fitted on the chassis.


Now I need to figure out the best spacers... brass, nylon, kryptonite ...hmm.. and then the extension-mechanism..

  This is the test-outrigger, with all three elements within one another. Strips of brass has been glued in place using industrial strength epoxy, and filed to correct thickness (0,5 to 2,8mm). The elements slide pretty well!

An M5 threaded rod allow me to extent and withdraw the 2. element. The rod is secured in the brass back plate with an inside nut, but later I will fit a couple of gears and a motor. The 3. element will be connected using the wire-method..

  This is the general method that I am aiming for. The horizontal part of the outriggers will not operate with any kind of load, so it should be good.
Instead of a hydraulic cylinder I will use the threaded rod (M5) and a geared motor, as mentioned above... and I have only three elements, not four.

(It will be a very different story when we look at the vertical part, not to mention the crane boom later, but both is a bit out of scope for now.)

  Now the 3. element: I bought a few samples of real steel wire, and looked for the most flexible one, yet strong enough for the task. I think I'll go with the 0,8mm wire... Now: Waiting for pulleys and stuff!

(Note the four "real" outriggers stock piled to the left, awaiting the successful completion of the test-outrigger, before they too get the mechanical stuff installed.)

 

While I'm waiting for the components for the internal wire system, I might as well go ahead and drill the holes.
I got some cup drills, sizes Ø44mm and Ø25mm. The reason for these holes is to reduce weight without reducing strength where needed.

Cutting was easy, once I got hold the right machinery. My handheld drill almost died trying, and I learned that a powerful machine is needed for cup drills!


  The outcome! The three small holes on the bottom is located in the middle and towards the back end of the stationary element. This part of the element will not need any strength at all, as the moveable outriggers (part 2 and 3) will only rest in this position (not carry any weight).
The large holes does not affect the minimum requirements for strength at all... far from, actually!

Total weight reduction so far (4 outriggers): Just shy of 1 kg.

  I still need to mill a rectangular hole in the top of the rear end, giving me service access to the internals of the outriggers. (Adjustment, lubrication and inspection.) The planned outline of this hole is marked in red when clicking the thumbnail.

The total weight reduction will end up at app. 1,2kg.

  Now the four outrigger houses have been through the metal shop again.
This time, I opened the upper side of the back end, giving service and inspection access to the insides.

  A narrow strip was left in place, so the outrigger end will look ok, when the end is visible on the crane later.

 

Here I have simulated a fully extended outrigger, (2 x 140mm extension)... and access to where the threaded rod, gears, and motor will go at the rear of the main house. (On the far right)


  *** LONG brake ***

Now, finally back at this project, I got the guts for the outriggers done!
In this pic I'm gluing (epoxy) brass plates in place, so the components fit and slide together (telescoping.)

  This is the extension-mechanism prior to the cable part being fixed, but you can see the spindle inside the long brass horn, roller for wire, gears and what-not.

  A bit more put together... getting ready for the wire-part.
(The outmost element will be driven and pulled by wire only, while the middle element are driven by a spindle.)

  Here's the other wire roller, this one is for the return wire.
The motor is a small DC motor with a gearbox from Conrad-electronics. Motor and all parts has to fit within the smallest of the three elements, so while you might think that there is a world of room for stuff.. there's really not.

  Note the two aluminum wire anchors inside element 3... and then see the next image...

  Here the two aluminum wire anchors are again, only this time they are connected to the mechanism that controls element 2 and 3.
The elements in the background are aligned with the mechanism, so you can see where everything goes when the outrigger is extended.

Max stroke is 300mm, but I will limit myself to 280mm (2 x 140mm) so the overlap of the elements are bigger, adding to the max capacity.

  Four brothers awaiting the vertical parts!
Outside measurements: 220mm long, 70mm high, and 40mm wide. Weight: 1840g (1,84kg)
Max stroke: 280mm in about 1:14 minute. Capacity is beyond 50 kg fully extended.

Youtube video here!

    Next step: The vertical part.. and an interface to control this by remote!

     


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