3D printed 1/16 scaled RC rotating tracked dumper

Nice save!  If its just some holes missing, PLA takes a drill just fine, just keep speed down or it melts.

Looking good! Glad you got the kinks worked out.

The bed is mostly printed and assembled.  I've got a 1/16" pin installed in each of the top rails that runs nearly the full length of the bed.  The same thing has been done to the bottom rails, except that the pins run from behind the bed pivots to in front of the bed lift pivots.  If you hold this thing up to the light you can see where the pins are located.  The bed is MOSTLY assembled because I still have to print and install the four gussets.  Two will be installed on the bed-side, in the corners between the top rail and the front wall.  The other two gussets will be installed on the cab-side to support the overhang.

I just took the  engine/pump bay off the printer, that was close to a 12 hour print.  The hydraulic/fuel tanks are printing now, the slicer thinks it's going to be a 5 hour print.  The printer seems to think it'll take 12 hours to print, but then again the printer thought that the engine/pump bay would take 19 hours to print - but it managed to complete the print in about 12 hours.

Tomorrow I'll print the gussets.  Then the only other yellow parts are the door and its' hinge.  The hinge I still have to figure out, but I've got an idea for the hinge that's been rattling around in my head for a while - just need to see if it'll work.  (The rear edge of the door needs to kick out as it opens.)  I found my stash of small rare-earth magnets, they're about 3-4mm in diameter and about 1.5-2mm thick.  They are what I plan to use to keep the door closed, and to attach any bits that I'd rather have pop-off than break.

Wow, that is a slick looking piece of equipment.  I spent my youth working for my father, digging and backfilling drainfield ditches with washed rock.  Having a pivoting dump bed would have made slick work of the backfilling; we often had to build "bridges" over previously dug ditches to bring in gravel for the next tier with a front end loader. 

Well - it took most of the day yesterday, but I finally got the hinge designed and and the hinge assembly working like it's supposed to work.  All 5 pieces of it.  Then I got REALLY ambitious and decided to model the engine/pump bay, the hinge assembly, AND the engine bay door.  I needed to figure out where to drill the hinge screw holes in the engine/pump bay wall, since it's already printed.  It took all NIGHT, and into the wee hours of the morning, to get that working correctly. 

For some reason the hinge assembly refused to work correctly after I attached it to the pump bay wall.  I'm not sure what I did that got it to work, but I'm thinking Alibre is fussy about the order the assembly constraints are set up.  It's almost as if Alibre thinks that A+B+C does not equal C+B+A.  I think what finally got it to work was when I manually aligned the 2 surfaces I wanted to make coincident.  Usually if I get the surfaces aligned within 45 degrees Alibre can figure it out.  However, this time, I had the surfaces aligned to within 2 degrees and it still kept refusing to align them.  I had to manually tell it that I wanted a 0 degree angle between the surfaces before Alibre said, "Oh... THAT's what you wanted me to do."  THEN, the hinge assembly started working.

Anywhooooo... I now know where to drill the holes in the engine/pump bay wall so that the door will work properly.  Without pictures it didn't happen, so here's what the engine/pump bay - hinge assembly - engine bay door look like when put together.  I haven't got the door, or any of the hinge assembly printed yet, so you're going to have to tolerate what Alibre says it'll look like.

It's somehow very satisfying to watch the door open and close, some day I'll have to get really ambitious and figure how to animate it so you can see it too.

Don

It always feels good when you have beaten the System 

I used to VERY frustrated with Alibre in regards to 'Import a SubSystem that in itself could move' - just to have it being Locked after Import   
So I was very happy to discover that the latest version (I skiped many [no money]) has a knob/function to 'Unlock the Subassembly' again 

Per     

ps  giving the different parts shown different colours - helps understand what you see 

I reprinted the door, and printed all the hinge parts late on the 11th.  Let's just say that I was less than impressed by the performance of the actual hinge and leave it at that.  Mistakes were made, there was a LOT of slop in the hinge, and I found out that while I was able to TELL Alibre how to make the hinge move correctly - there's no EASY way to do that in the real world.  I was all set to scrap the hinge idea and just use a couple of magnets to stick the door on, then I came up with a design for the MkII hinge. 

Most of the day was spent working outside on the lawn, we've been getting some rain lately and the lawn is loving it.  Because of that, I didn't get a LOT done on the MkII hinge.  I did get enough of the design done to realize that my initial MkII design would not work correctly.  I need the hinge to make the edge of the door swing in an arc, not just pivot around a fixed point. (I need the edge of the hinge side of the door to move about 1mm away from its' closed position and finish up about 2-3mm behind it's closed position.)  I can't make the hinge any thicker, or wider, than it currently is without redesigning a bunch of other stuff - but I can make it longer.  I think I can make this work, I just haven't found the right pivot points yet.  Kind of like Edison and the light bulb, I'm finding many ways to NOT make the hinge work like I want it to.

Don

Significant progress has been made, we dun got's us a workin' door now.  Sadly the MkII hinge did not function either, but it was really close.  There was some interference between the door side of the hinge, and the engine bay side of the hinge when opening, I left myself a note to fix it.  Yesterday morning I fixed the interference and printed the Mk2A hinge, it didn't work either - this time the interference was on closing.  So....  I printed the Mk2B version and it worked, I got the full range of motion out of the hinge.

Up to this point, I'd only been using the front pivot with its' bent dog-bone linkage - the bend gives me a couple of extra mm's of clearance Clarence when the door opens.  Now it's time to throw the rear scissors linkage into the mix.  Whaddya mean, it don't fit?  There's supposed to be a 0.5mm clearance around that linkage - back to Alibre and check it out.  The linkages, both front and back, have a 4mm OD on the ends.  The radius of the clearance for the front link was 2.5mm - just like it was supposed to be.  The rear radius was not QUITE 1.9mm.  Instead of the 0.5mm clearance fit I wanted, I had over a 0.1mm interference fit - on nominal 4mm OD.  How'd that happen?  OH..... I see, I had a tangent constraint between the clearance radius and a line segment.  I keep forgetting that order REALLY matters in Alibre when setting up constraints when neither position is fully defined.  I apparently clicked on the line first.  That would adjust the radius to the line position, not the other way around adjusting the line position or the radius like I WANTED it to do.  Stoopid computer did exactly what I told it to do, not what I wanted it to do.

Just like the little bear's porridge, the Mk2C was JUST right.  The operator was so excited to see the door he jumped in the seat to take it for a spin.  He CLAIMS that when it wouldn't start he called the mechanic over to take a look at it to see what's wrong.  When the mechanic opened the door, HE started yelling "We've been robbed, we've been robbed!  They took everything!"


I'd LIKE to get a little more of a door opening.  But, it's enough that I can get my fat fingers in there to flip the power switch on/off.  That ain't perfect, but it's good enough.

We be movin' onnnn... 

We're moving from printing yellow parts to grey parts.  What's next on the Hit Parade, the cab, the CAB.  I'm tired of the operator complaining about the lousy boss who doesn't even put a roof over his head.

Now he's got 4 walls, a roof, a floor, and a control panel - with buttons and a knob to play with.  And, unlike Les Nessman's walls, these don't involve masking tape on the floor.  OK, masking tape IS keeping the floor from dropping out from under him - so I guess masking tape IS involved.  MUSE..... Stop whispering in my ear,  I am NOT adding a working door to the cab.  Keeping what remains of my hair, and sanity, over-rules the coolness factor.

I'm ALMOST done digging wiring tunnels, I'm up to 8 of then now.  I KNOW there weren't THAT many Stooges, maybe I'll name them like the Bing Crosby/Bob Hope "Road" movies, you know:
Road to the Front
Road to the Back
Road to the ESC's
Road to the Slew Motor
Road to the Left Headlight
Road to the Right Headlight
Road to the Left Drive Motor
Road to the Right Drive Motor
And the list will probably go on...  I've still got to dig a hole in the floor of the Engine/pump base, so the wires can get out of the tunnel and into where they belong.

Don

Dumping Donny in the cab won't be getting wet while operating any more! I wouldn't worry about a working door, Donny can climb in and out of the big side windows easy! 

It's looking great so far! 

cnr6400:

The roof is currently just sitting on top of the walls, so it's easier for him to climb out through the roof.  I'm considering reprinting the roof with pockets in a couple of the corners for my small 4mm magnets.  I can glue a couple pieces of scrap steel in the cab corners for the magnets to grab onto.

If I do that, I am definitely NOT using organic supports under the roof overhangs again.  Cleaning that crap off took longer than it took to print the roof.

That blankety-blank Muse really is a slave-driver!  It put an idea in my head last night and wouldn't let me go to bed until I tried it out.  It was after 1:00AM before I finally got to bed, but this was the result.

This "Experiment", is a test print of the work platforms that the RT7R has attached to the side of the track frames.  It's about 60mm tall, 20mm wide at the bottom, 10mm wide art the top, and is 2mm thick.  On the real thing it's probably covered with some type of expanded metal mesh that'll let the dirt fall through.  How to duplicate easily that in small scale was the problem, you're looking at my solution using the "Easy" button.  I designed the platform shape as a solid object, then told the Prusa slicer to slice it using 0.2mm layers, 3 perimeter walls, the "Grid" infill pattern with 25% infill, 0 bottom layers and 0 top layers.  If I had used the "Rectilinear" infill pattern it would LOOK the same, but the only places the infill layers would actually touch each other would be at the intersections.  The "Grid" pattern takes longer to print because it prints the entire 90 degree pattern every layer, but you get 100% contact between every layer of the infill.  It only takes about 5 minutes to print the platform.  But it took a LOT longer than that to figure out how to do it.  If I jam something through it, the infill WILL break - it's only 0.4mm wide after all.  But under normal conditions it's quite strong.

I'm sure others have done something like this before me, but it's still a "first" for me.

Don

That is a very clever way to get that expanded metal grid pattern, Don!  I'll have to file that one away.   

Kim