90 ton 1/14 metal excavator scratch build w/embedded PC

[SteinHDan]

The top rollers are similar to the bottom rollers, but a bit smaller.
The type is SG15 U Groove 5x17x8mm Sealed Ball Track Guide Bearing.

Ebay link:
- http://www.ebay.com/itm/400561381584

The top rollers use an M5 40mm bolt and two M5 4mm spacers on each side to get the right width and position (I've not received the spacers yet, so I just used some washers in these pictures).





The mount is a bit different than the original CAT 390 (and most other excavators). Normally, the top rollers are only mounted on the inside. I guess this is to avoid rubble being stuck under the roller as it slides down on the tilted suface of the rail. But for this build, keeping it simple, I've just mounted it on both sides like the bottom rollers.

[SteinHDan]

The tracks are made of an industry-standard roller chain and track pads. The roller chain I'm using is a British Standard 08B 1/2" pitch chain, similar to the ANSI #40 chain. I'm using this chain as it is one of the more commonly used types, and thus the price is lower. It is a bit too big for this model. The 1/2" pitch means that every track pad is 25.4 mm long, and it should really be something more like 15mm long.



The "ears" are called attachments and there are various standard types. These ones are name "k1 attachments". There are wider versions that also can be used called "wk1". They have two mounting holes on each side. Search for "roller chain k1 attachments" on google to get more info.
- https://www.google.no/search?q=rolle...=lnms&tbm=isch
- https://www.google.no/search?q=rolle...=lnms&tbm=isch


I originally planned to mill all the track pads in aluminum. But then I though I just make some temporary ones on the 3D printer, and they became very tough, so now I'm thinking that I'll keep the plastic ones until they break (or maybe they won't break). It is also a benefit to be able to drive inside without scratching the floors.



The pads attach to the chain with two M4 bolts 10mm long. I chose a slotted head, as I think it will be easier to unscrew than philips or hex when the tracks get full of mud. On the other side I use two M4 locking nuts with nyloc locking mechanism.

Ebay links:
- Screw: http://www.ebay.co.uk/itm/261605587451
- Nut: http://www.ebay.com/itm/321386920963







I also overdid the width on purpose, but now I regret it a bit. I like the wide-tracks look, but I guess this is a bit too much. The real model in scale would be something like 60mm wide tracks. Mine are currently 70mm wide.

[SteinHDan]

The first test drive:

https://www.youtube.com/watch?v=AoB3Eev6npk