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

[SteinHDan]

I'm looking forward to that, Jeff!

Stein :-)

[SteinHDan]

I don't like doing non-reversible operations like gluing, painting and welding, because it's then a lot a work to make small adjustments to parts. And when doing prototyping like this, you make small changes all the time. I think I've had the machine built completely up and down around five times now..

Anyways, sometimes you need to do those types of operations anyway, either because it's the only way or I'm not able to think of any other way.. ;-)

I've glued the counterweight pieces together now. First there are three 75mm M3 threaded rods. They don't screw into anything, they are just there to align the pieces and give more strength. Then the two pieces slide together:








I think the best glue to use for a certain type of plastic is... more of that same plastic! Dissolved in acetone. This approach works very well with ABS.

For this model, I've just cut the yellow 3D-printer filament into very small pieces and put them into a glass jar. Then add acetone and let dissolve for a couple of days (depends on the size of the pieces).








I've also glued in the stainless steel M4 nuts that hold the body to the base plate with the thumb screws. One in each corner:





Just a tiny amount of glue is needed here. We just don't want the nuts to come loose when the thumb screws are not holding them in place.






Ebay link:
- Thumb screw - 10pcs M4 x 15mm

[SteinHDan]

The body goes together by using eight M3 threaded rods, four self-tapping screws and two M3 machine screws.

First M3 nuts are inserted into slots in the counterweight parts:






Then the threaded rods are screwed into the nuts:





The rear doors slide onto the threaded rods, and are attached with an additional two M3 20mm long bolts:








The front doors also slide onto the threaded rods. They are attached to each other in the middle by three M3 bolts and locking nuts. This attachment is the bridge that holds any weight on top of the house body.






Finally the tanks and the steps slide onto the threaded rods:




For these two parts, there are four additional self-tapping screws that attach the tanks and steps to the front doors:




At the end of the threaded rods, there are M3 nuts countersunk into the end of the front parts. Since they are completely inside the part, a socket screw driver is needed to fasten them:

[SteinHDan]

I made a somewhat improved snap-in hinge pin assembly. I should have used some longer bolts, but I didn't find any.

The assembly consists of two M3 20mm bolts, one compression spring and an aluminum tube to hold it straight:






The hinge pins are then snapping into the holes in the sides of the lid opening in the body: