www.Robse.dk - Thé internet site!!

RC models by Robert Holsting

HOME     Blueprints & plans About me Contact me

  Behind it all: The core!

The core of the crane will support everything else.. including the load.
This image is from AutoDesk Inventor, and shows a simulated load of 250N (25kg) on a 40 x 70 x 40mm steel profile, 4mm thick, right where the crane itself will sit. The core is restrained where the outriggers will support it later on in real life. Displacement is less than 0,07mm!

Well... let's build it!

  It is going to be a bit hard to build by hand, and I might have to take it to town once or twice.

  Cross section of the 40mm x 70mm x 40mm 4mm thick steel profile.
Weight will be about 5,5kg when I'm done with it.

  At the very rear of this beam, there will be two outriggers. The core therefore needs to be cut to accommodate these.
It was quite a job doing it with just a regular hacksaw and hand files, but it did offer a free workout!
New rule in the house: If the steel's cold, you're working too slow!

To prevent rust a light dust of gray primer was applied upon completion.

  Cutting the core like this does weaken it, so some reinforcement will be made later.

  Starting at the rear, having made the cut-out for outriggers, I could start building towards the front.
Here the two rear-most axles (No. 7 & 8) are fitted!

It took forever, as I had to check, recheck and then check the measurements before drilling ANY holes!

  The next two groups of wheels are the 3-axle boogies. Some M4 and some M3 threads needed to be cut, and to ensure that I didn't break any taps, AND that the thread was at it's best, I put the tap in the bench drill like this, oiled the tap, and cut the thread by hand-turning the tap, while applying slight pressure on the leaver.

It worked out perfect!

  Masking tape made marking and pre-drilling easier.

  The two 3-axle boogies have a separate anchor for the rear-most axle, shown here. It goes on the inside once done, cut holes and thread are of cause cut from the outside, so the anchor are on a one-time visit on the outside of the core wall as well.

The rest was pretty straight forward: A LOT of measuring, testing, careful drilling, cutting thread, fitting, testing.. on with the next.

  Rear-most group.. Axle 8 & 7.

  Middle group.. Axle 6, 5 & 4.

  Front group.. Axle 3, 2 & 1.

  Hope fully this is the only rollover it'll ever do....

  Seconds after this image the core was stripped down, cleaned off, and painted in an even coat of grey primer.
(I spotted some initial rust-flakes, and that I wanted to stop!)

  And that's it! One rolling chassis.. Made using nothing but simple hand tools.

Next: Steering, drive train, support structure for the drivers cab, outriggers... oh, and Christmas! :-)

  (two weeks later...)
Back from Christmas: Working on the support structures around the outriggers!
First I cut a piece of the same steel profile, and drilled a lot of holes....

  ..as seen here...

  I then called upon an old friend in the metal business: Mr. Metal Fatigue! He NEVER fails...

Bending the now isolated area back and forth caused it to break along the drilled holes.
(And no... Santa did not bring me a mill this year..)

  A while later, I had the three pieces needed: Rear, middle and front structure components.

  Here's the rear one. A back plate will come later, and finish it all in a strong formation!

  The middle piece.
Note that it's not filed into the final shape yet. I wanted to wait until it was in the final place, so the hole would be exactly 70 x 80mm, and aligned!

  The front piece.
Allowing the crane to be picked up by it's nose.

  And fitted using 4mm bolts and nuts, and some steel strips on the inside.
The support components might be TIC welded later on.. not sure if I really need to.

Update 20FEB2013: A friend of mine welded everything, and it did not twist or anything. Absolutely great result, and extremely strong!

  Note the holes above and under the hole. The outriggers will become an integrated part of the support structure by bolting those on to the main chassis.

  Front section, and the future bumper right next to it.

  Front bumper fitted for show..
It will not be able to stop a train, but it'll be fine for this job.
Four headlights will go into the bumper, as will a device to tie to crane hook to while driving.

  Now the main chassis is done. Weight ended up at 6kg, slightly less than expected.

Paint will follow shortly, but first I have to fit the cardans, and main deck, funny structures between axle six and seven, gear box and motor, travel limiters for the axles (maybe), and a few other details that will require work on the chassis.
I have got the real RAL codes for the Liebherr colors though!!! It'll be great!


Back to index --->