Friday, 7 March 2014

JCB JS 115 Tracked Excavator


JS115 is the smallest JCB tracked excavator, excluding mini and midi series.


Why the smallest excavator?
Because my previous one, the JS360 was very big and heavy, and therefore not able to move and operates easily under its own weight smoothly as I want, not to mention under some load.
So I wanted to create smaller one, which will be able to realistically represent model of a excavator.

 LINK to the real machine.

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Goals during construction:
Realistic functions,
Modelling realistic body carefully using official PDF file,
Scale exactly 1:13
Efficient use of the motors



This model has to be very agile and nifty, so I made few drastic moves, like getting rid of the gears (the whole model has just 5 gears) and simplified cylinders.
Also, It has to have realistic moves, meaning speed of the arm and the tracks.
So, to fully utilities the PF motors, I have connected them directly to the sprocket wheels and cylinders. That is how its done on real machine, except it uses Hydrostatic motors directly on sprocket wheels, which are fed by pump.
On the model this concept would be unrealistic since it does provide greater speed of movement of the tracks and arm, unless operator uses Speed Remote controller

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That way, operator chooses one of the 7 speeds, and the model becomes very precise and realistic digging tool and can accelerate gradually or make very delicate moves with the arm.


1:13 scale
The model was developed for a week or two on a computer to make sure almost every bit of it is scaled down in a proper way.
I wanted to achieve the perfect look, as the real machine, meaning "big bubble" look.
Reference was PDF file from official JCB webpage, every single line of the machine is scaled down.
It was of great importance to me, to have exact scaled replica.

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As you can see, this machine has a little bit unusual look compared to the bigger brothers, it looks like it is unstable or just like a toy, or it looks like tracks are too short, but thats why it had so big impact on me, and even it does not look like that, it can provide good digging performance and it has 12 tonnes.

Functions:

Drive left track-XL
Drive right track-XL
Superstructure slew-M
Arm up and down-2Ms
Dipper-M
Bucket-M


Tracks:

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Are 26 studs wide.
H shaped frame in few layers does great job in providing stable platform.
One XL provides torque for each track, in 1 to 5 reduction so this model has great power to weight ratio.
Everything here is symmetrical.
Each side has side rollers (like on real machine) which keep the weight off the wheel sprockets.
I had to rebuild the whole undercarriage 5 times to achieve the stage I am fully satisfied with.
It was very tricky.

Turntable:

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Is 14 studs wide.
This was the most difficult section to create.
Hardest part was to make it so small and sturdy.
It has to have big turntable part in the center, then worm gear on it, then ring of black rollers around it, then it has to have room for PF cables from undercarriage motors, then vertical bracing beams (which holds the boom and frame of the superstructure)...and all of this has to be sandwiched between tiles underneath for smooth rotation and superstructure above it, and placing all that between tracks, which is narrow  ...connecting all that and make it sturdy was a nightmare, but I have done it.

Superstructure:




The cool part! It is 24 studs wide.
As you can see on the pictures, this machine is full of curves...at the back there is that sloped section, and at the top there are rounded edges.
I have enjoyed modeling that on my model.
The most difficult part was that tail part, because it has 1x3 slopes at the top, black section in the middle, and 1x2 slopes at the bottom...and all that is tilled. It looks simple from the outside, but inside it was nightmare to make it...I don't care, it was a fun. The best part is that it is high exactly like the real machine just in 1:13 scale!
Strength comes from the Technic bricks at the bottom of the superstructure, but it was constructed that way that all the pressure from the boom and the cylinders are delivered to the turntable and its vertical bracing beams. It took me a few rebuilds to achieve that.
I also wanted for superstructure to have some details like openable hatch at the back, where the engine is mounted...in this case there is new LEGO rechargeable battery which is great as it can be charged without removing it from the model.
At the sides of the body there are two openable storage areas, where are chains, tools and other misc on one side and oil filters and fan on the other.

Cabin:

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Is 8 studs wide.
It is the same size as on previous excavator, they are the same size on the real machine, too, but it get a mayor facelift, basically it is built from scratch.
Once again it has flexible tubes and slopes done in SNOT.
It has internal gadgets at the right side.
Cabin is completely separated from the superstructure (it is connected to the frame with 4 pins, and can easily be removed for any reason,

Arm:
Due to scale and the small size of the real excavator, the arm in 1:13 scale is just 3studs wide.
It was hard to find a perfect mounting points for the arm and its cylinders, because that points has to be heavily braced.
I managed to achieve relatively realistic range of movements.
The arm is strong enough that it can bear the whole load of the machine on itself, as well to perform wheelie on each side.
Arm can withstand 500 gr, and the superstructure still can rotate.

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Cylinders:
As simple as possible...M motors connected directly on LAs...and it is effective, it has power to operate the arm in a very agile way, and it can lift any side on the excavator while digging.

Buckets:
As on real excavator, depending on the ground thickness, there are few buckets available, so on this model 4 bucket were adopted for the arm.
There is big bucket 18x10, medium bucket 8x6, small bucket 10x4, small bucket 4x4 and brick-built bucket.

Stickers
Were made by me, from PDF files, printed using LEGO color scheme.
I have always wanted to make a model with full details, using stickers.
I like them, as they provide realistic look of the real machine.

Controller:

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Behind the scenes:

I have always wanted to build tracked excavator that, hopefully, will be good enough to compete with the greatest excavator of all time, the JCB JS220, made by Jennifer Clark.
I think that her work affirmed my passion for the excavators, and pushed me in building more realistic and more complex models.
So, my aim with this model is to try to achieve realistic look and technical possibilities of her model.
My model is exactly 50 percent bigger than her, but since my JCB is much smaller in real world, both models are relatively similar in size.

Also at that time, LEGO was presenting their newest excavator, 8043.
It looks great and I wanted to make my own excavator that will be very close in size.
So, that was just one push more to invest more time in my model.

I think that I can call this model my Limitless Tracked Excavator!