Metal Hobi MH-245 kit as Hitachi ZX245 excavator

[Blender]

Been quiet around here in all sections.

I was too slow to paint the kenco and it rusted up. Recut it in stainless and painted it. Found some super thin .15mm THK M1.6 washers for assembly. Flipped the electro magnet to the top for added weight when collapsing. Needs some custom decals. Accidentally roasted one electromagnet by giving it full 3s lipo voltage through the ESC. Got real hot. No real harm since I have a spare.




Need a scale rigging system and route wiring to look like aux hydraulics.

In the short time I played with the machine at a hobby shop in Mesa, it was apparent there's little traction on plywood. Most noticeable at reach as there is no real counterweight. Fix is some molded "rubber" track pads. I don't think I could pull off self made rubber molded tracks, but snap on inserts are doable. First step was some cad and 3d printed prototypes. Got some SLS TPU and some rigid abs samples. Fit is fine, the rigid ones are difficult to snap on. The TPU ones are good. Nice attachment, and feels like improved traction. They're way too expensive to print each one, so I have to cast my own to actually try them. Done it a little at work. Made a 2 piece silicone mold and started pouring.

Pads will be polyurethane. First material I got is soft durometer, but way too flexible kinda feels like a silicone. Second material is higher durometer, and higher stiffness but still too flexible for retention. Neither are exactly what I'm looking for, but I'll pour as many as I can to test them out. I can only make 2 per day. Need 84 for a full set.


Printed samples. Were also used as the mold master.


Mold making in progresses. Added fill and vent ports, then poured the top half of the mold.


leftmost is my casting, other two were printed. No black colorant added so I don't waste it. Casting is full of bubbles. I don't have vacuum degassing, but maybe I should build one.

Also looking for a affordable toolmaker to possibly switch to injection molded parts. Protolabs doesn't want to cam out the snap fit undercut, so I'll look overseas. Proper injection molded parts will be nicer and have a better selection of materials.

[frizzen]

Great looking grapple!

Cool track pad design, hopefully that'll get the traction you need

For degassing, you might be able find a painting pressure pot easier than making vac chamber?
Resin poured from higher can also help reduce bubbles you get into the part. A thin ribbon pour can help degas as it extends, plus it traps less air as it hits surface than doing it as a bigger faster pour

[Blender]

Thanks frizzen. Extending my funnel upwards would be real easy to try. Lets we how it does.

[Blender]

Tried out the elevated pour. So far so good. Still has small internal bubbles when cut, but OK for my use.

[frizzen]

Glad that was helpful. Those pads are looking great!

I know with open pours some epoxies will let you clear out near-surface bubbles with a butane torch lightly, not sure how it might work with dark tinted poly before trying to mold?

[ddmckee54]

The Veg Oil Guy on YouTube has shown how to build an inexpensive vacuum chamber for degassing investment plaster before using it to cast a mold. He even shows how to build a hand powered vacuum pump out of PVC pipe, you might want to check his stuff out.

[Blender]

I needed a new brake bleeder for my real truck. Did the vacuum style, so maybe I can use the same to degas the resin. Haven't tried it yet.

The little ZX did get its first taste of real dirt. Brought it out to a raw sandy wash. Dug a trench 6 ft long by 9" deep. Machine did well. Proper digging technique was key. Occasional small rocks below the surface were not an issue. The hardpack dirt nearby had too many golf ball sized stones in it and was slow digging.



The excavator and dumper bouncing around in the backseat of my truck wasn't ideal. The excavator was ok, but the dumper would roll. Came up with some transport crates. Also conceals the contents when loading the truck so I don't look insane with my toys.

20mm square aluminum extrusion frame, aluminum deck, acrylic sides and top panel. Everything screws together. Made long nut plates, but tapping 80 M5 holes is not so fun. Found some tiny 3/4" wide ratchet straps. With a couple redirect brackets those will cinch the tracks to the deck. Locating blocks will secure it side to side and fore/aft. All I need is a strap to hold the bucket and prevent the slew from moving. It's meant to open by removing the upper 5 faces as one piece, leaving only the floor. Should allow good access for strapping things down. Will be slow to open/close since there is a lot of hardware.

Have some brackets to mount casters if I want to roll them any distance. Could stack 2 or 3. Sized to the largest machine I'll likely own: Lesu 4 axle roll off. The 3 axle dumper I already have fits no problem.

[jerry56]

Those cases are pretty slick, and being able to strap them down eliminates the need for foam..

[Blender]

Thanks Jerry. I hope the tie down system is as solid as expected.

Tapping the stainless steel nutplates sucks, so I ordered some aluminum nutplates. Thread tear out will be a concern.

[Blender]

Case worked well bringing the Hitachi to a Diesel show. Was only a few miles from home though. Mostly just enjoying playing with my machines.

While gluing in the windows many weeks ago I broke the upper door hinge. It was an aluminum milled part. I never figured out good aluminum welding so I can't just stick it back together. Metal Hobi is no longer around so I'm on my own for replacement parts.

First plan was to laser cut some stainless sheet and weld it together with the tiny welder. Parts are too small for the laser cutter. Plan b is an investment cast brass part from Shapeways. Had to alter the original design slightly to meet their part requirements. Hinge pin is 1mm dia brass rod that's welded at the top and bottom for retention. Swings freely and works great.



Top hinge is easy to swap. Have to gut the entire cabin to replace the lower hinge. I'd like them to match.

[ddmckee54]

Paint hides many sins, or in this case different materials. Betcha the hinges on the real 1:1 scale deal are painted.

The cases/carriers look good too. A few strategically placed holes, and some 3D printed chocks... Nuthin's goin' nowhere.

[frizzen]

That really sucks about your door hinges, but great job remaking them!

Those transport cases look sweet! Am i seeing that they can stack onto the wheeled one kind of like shipping containers?

[Blender]

Originally Posted by ddmckee54

Paint hides many sins, or in this case different materials. Betcha the hinges on the real 1:1 scale deal are painted.

The cases/carriers look good too. A few strategically placed holes, and some 3D printed chocks... Nuthin's goin' nowhere.

A little paint would go a long way. Just too lazy to fully disassemble.
As for the cases, yeah I need to finish a couple chocks/blocks and it'll be complete.

Originally Posted by frizzen

That really sucks about your door hinges, but great job remaking them!

Those transport cases look sweet! Am i seeing that they can stack onto the wheeled one kind of like shipping containers?

Stack is the goal. The bolt heads holding the top panel on are a little too big to align well into the case above. Never ordered the alignment wings that should extend from the sides to align the upper case.

since you mention shipping containers, some round pucks in the corners would key in really well and be super clean looking. If I have some scrap aluminum I should try and whip up a set in the lathe.

[Blender]

Sat down and spun up 4x corner pucks. Force fit into the lower box and slip fit into the upper. Works not bad once they're all aligned. Lets me use the top box as a push handle to pop over thresholds.




Now I need to make like 12 more