More Madill Madness

[Beekster]

I've been hinting at this on my original thread describing my first Madill 071 yarder project.  After some deliberation, I've ordered this from SANY America for $49.95.  It has yet to ship, but will eventually become the basis for a second yarder:

This is a 1/35 scale SANY SY-215 excavator.  The real ones are made in China and I'm sure the replica is too.  I will disassemble it and use only the track frame, fabricating a hull around that.  In between various work on the first yarder, I've started the structural elements of the second.  Behold, the winch bedplates, glued together for now with wood glue just to keep things lined up.

The holes have been drilled for the various shafts, and this time around I made them all closer to scale diameter rather than all one size.



Here you see most of the gears and shafts mocked up.  On the right, the big Skyline gear and the little one adjacent (on the Intermediate shaft) are shown for their relationship to all the others.  Both of these will be on the front face of the rear bedplate (that is, inside the winch bay with the big drums).  The other gears will all be on the front face of the front bedplate, inside the superstructure.  The middle medium gear is the Haulback drum, and below to the left is the small gear from the Primary Input Shaft.  The medium gear furthest left drives the Main line drum, and above it is the smaller gear & shaft which run the small Straw (or Haywire) and Tag drums.

The last image shows the relationship of the winch drums to each other:


The three largest drums are all sandwiched in between the bedplates.  The Straw drum doesn't really overlap, it is in the forward superstructure compartment.  It's twin, the Tag drum, is back in the engine bay.

This yarder will be loosely based on S/N 70141, seen here:

It will have four powered guylines and the fancier cab, and a more enclosed engine bay so that I don't have to do as much detail in there.  The deck will be extended aft, like this:

[JCON]

Wow that will be very cool!!!

[dogfish7 (R.I.P.)]

Count me in!

[JED]

WOW you don't take the easy route do you 😳

[JCON]

Apr 2, 2021 15:02:22 GMT -6 JED said:

WOW you don't take the easy route do you 😳

The easy route if for sissies!!!  

[Beekster]

Apr 2, 2021 15:02:22 GMT -6 JED said:

WOW you don't take the easy route do you 😳

This should actually be easier in some respects than the first one, Jed.  For one thing; I have figured out how to do things in a way that simplifies the task.  Those bedplates, for example.  On the first yarder, I laminated the thickness I wanted and glued on the paper template to cut them out.  It's much easier to make two big rectangular slabs and dial in the dimensions, then add the small shelf and the angle on top as separate parts.  The suspension will be immensely easier to deal with, though getting paint to stick to what are sure to be rubber tracks might be a challenge.  This model will be finished in transport mode, which also has it's benefits.  The turnbuckles won't have to actually support it, so the U-shaped ends can be plastic, not brass.  Likewise, the shackles on the spar for the fixed guylines don't have to be functional so they can be swiped from a Sherman kit or bought from Shapeways; all they will support is some portion of the mass of the rigging line itself.  This is fortunate, since RB Model in Poland hasn't updated their website in four years and most of their sizes of working brass shackles are out of stock.  I will have to come up with working shackles for the powered guyline sheaves at the end of the spar, but I'll have plenty of time to figure out what to do about that.

[reserve]

Well, in for a penny in for a pound...ought to go smooth since you've already done one.

As for paint on rubber I've been playing with Mission Models paint lately, did the vinyl tires on the last two truck builds in their tire black. Ran the primer, let dry for a day, then the final color coat with an additive they call poly mixed in and let that dry for a day. I did an extra I had laying around also which was my torture test bed and after it was dry and cured I stepped on it, twisted it, squashed it and the paint did not crack or flake off. I am most favorably impressed with the stuff, I'll be phasing out all other paint I use in favor of this brand methinks.

Anyway this may be the solution for getting good color on rubber tracks, surely better than scratching a set of tracks for this if it works

Regards,
Mark

[Beekster]

I will certainly bear this in mind, Mark and have a look at the Mission Models paint. As the tracks ought to be steel, I will have to go with something other than black. It seems that modern alloys for machines like this weather no differently than their WW2 tank counterparts. What you are describing with the "poly" mixed in sounds a lot like the methods used to paint modern car bumpers and other things that have to be able to flex without having the paint crack. That will be essential, since I'm sure I will be removing the tracks to paint them and to paint & weather the track frames themselves. And since it's certain the model doesn't have a working track tensioner like the real ones, that means stretching the tracks. When I get to play with it. It still hasn't shipped yet, and come Thursday it will be two weeks.

[Beekster]

I never got a shipping notice, but this arrived today via UPS:


Rather a nice die-cast; seems a shame to part it out but nevertheless that is what is happening.  A single, very tight Philips screw and washer secures the track frame to the rotating cab assembly.  A little work, and the track frame is separated.  Here you see it with the Sherman-based yarder behind to get an idea of size.  This track frame will be perfect:


Now I have some thinking to do and a choice to make.  A bit of fiddly positioning confirms that a standard Sherman hull will fit between the tracks:




So I must choose between doing a modified Sherman chassis, like this one here:




Or go with a fabricated box structure hull like 70141 here:

[DPNM]

I use DupliColor lacquer paints. I wanted to paint a hardhat but the paint wouldn't stick. DupliColor sells a product called Adhesion Promoter. I sprayed it after I stripped what wouldn't stick then respray painted the hardhat. The paint stuck. Don't know if it helps you, just another avenue perhaps.

I'm fairly certain you said in a few posts back that you are going to base this one loosely on 70141. That being the case the fabricated hull would be the one to go with. Depends on how loose loosely is to you. Much easier to use a kit hull though.

I hope you don't mind me giving you my opinion before you asked for one.

[Beekster]

Always glad to get additional opinions! And you are correct, I did originally say a fabricated hull and to be hones only waffled on that when it became clear the the track frame will actually clear a Sherman hull. And a fabricated hull will be pretty easy, really. I've already cut out a floor panel to start looking at possibilities for the layout. My True Sander has problems sanding a piece eight inches long and keeping the sides even, though. That length looks to be proper, as determined by the highly scientific and accurate TLAR (That Looks About Right) method. Because the ends tend to get sanded a few thousandths more than the middle, I think I will cut the ends off this floor and cut smaller pieces to replace them so that I can keep everything square. Or just cut new pieces entirely; I can re-use the original piece elsewhere (perhaps cutting it up to form side pieces). I will not have this dimensional issue with the sides, which have to be sectioned to clear the bogie frame anyway. The bogie frame has a convenient hole in the center, and I am tweaking the diameter of a piece of styrene tube to use that as a center point. I will use bits of .375" I-Beam with .020" sheet backing one side to build frames to positively secure the bogie frame. I think I will be fine if I center up the frame front to back on the floor. The winch box, when assembled, will sit dead center on the track frame; makes sense to me because the winch box is the heaviest element and doing so also centers the spar above the center of the track run for maximum stability.

[DPNM]

I didn't think I had offended you.

Whichever way you go with it I am sure it will turn out extremely nice as your workmanship has proven.

[JCON]

I really prefer the bulk of the fabricated one to be honest...

[Beekster]

Apr 5, 2021 16:40:49 GMT -6 JCON said:

I really prefer the bulk of the fabricated one to be honest...

I have to agree, and going that route emphasizes the lower center of gravity and more stable platform compared to the Sherman chassis.  The difference will be obvious when the two are eventually side by side, even with the spar down.  Back to rummaging for useful bits.  There's an inline-6 engine that came with a Volvo snap-fit tractor-trailer in the war room somewhere, and that might be perfect.  Once I figure out what kind it is, and add some details to it.  Still less work than scratchbuilding another Detroit Diesel 8V-71, no doubt about that.

[JCON]

Yer a good man Charlie Brown!!!

[JED]

Hmm decisions decisions 🤔, whatever you choose will be the bees knees so we're waiting 😂😂

[Beekster]

Today I have been working on the box chassis, and this is where things are:




The Chopper II and True Sander tools have been getting a workout dialing in the .040" thick pieces for this. The central post is sleeved tubing, and it needs a wee bit more sanding so that I can shift the track frame around a bit to get the gaps even on both sides. There are still some structural problems to solve; this is quite bendy since the middle is so open. Eventually the track frame will get epoxied in there, but I don't want to rush into doing that. There are also issues at the back:



If I use this engine, the transmission obviously has to come off. I probably also need to extend the hull back there, either full height or angled up from the bottom. The winch box will sit just about dead center above the track frame, perhaps slightly aft of there. And then there's this:



Note the large oblong structure nestled below and between the Wichita brakes. That's the cover for the power take-off, which drives the primary input shaft running through the bedplates. All the other gears are driven off this primary shaft. This drawing shows how, though the perspective is altered so that the layout of the drive shaft going to the Sherman transmission can be seen



The position of this PTO is fixed on the back of the bedplate, because whatever the chassis and however it is powered, the PTO is still driven by the engine and that's mounted on the centerline. The PTO housing will have to clear the track frame, which will establish a position for the winch box. The track frame widens out from the center as it extends fore and aft, so where the PTO housing sits will determine the furthest aft that the winch box can be.

It looks deceptively simple at this point, but that example I just cited is an illustration of how you have to think about where and how everything fits as you move along. So, oddly enough, making a PTO housing soon is probably a good idea. It can be tacked to the rear bedplate, and mocked up to clear the bogie frame. With that in place I can see how the engine wants to fit, which will drive design decisions about extending the hull.

[JCON]

Very cool!!!

[Beekster]

I mentioned being in no hurry to epoxy the frame into the hull. Here's why:

Visible here are depressions on the wheel cover plates where the plastic cooled. Some filler and sanding is needed here. And there's no detail on the ends of the rubber band tracks.

With track removed, you can see ejector pin marks and mold lines on the frames and wheels.

Here you see a seam on the metal frame from the die-cast process. This too needs to be sanded smooth.


Fortunately, a little work prying with a small screwdriver gets everything apart and off the frame:


It's easy to see the problems here, and in fact they do contribute to the rubber track not fitting very well. So I will start cleanup on these. One small mishap occurred when dealing with this so far. One of the track frame parts was visibly bowed, and the material is somewhat flexible. Not infinitely so, since one of them snapped in half. I've used ordinary plastic cement to glue it back together; we will see if it holds. If not, superglue ought to do the job.

The lack of detail on the rubber track bugs me. These plastic parts can be cleaned up nicely, I think, and so can the die-cast frame. If I use the rubber tracks, they will stand out as being rather toy-like. There's a solution, of course, and you may say that that way madness lies: Make my own track. I am actually thinking about that. The tread plates are actually rather simple designs. The complicated elements are the chains which engage the drive sprocket, and those are molded as part of the track frame. What I need to do is make the tread plates and glue them on...

Several dozen of them...

So I am beginning to formulate a plan. There is a SANY equipment dealer in Canby, about an hour away. They have an SY-215 excavator in stock. I think I will contact them and ask if I can photograph and measure up the track plates on the machine (or a plate from the parts stock, if they have one. With that, I can make a few and and make a mold to cast up more.

[Beekster]

Started grinding on the bogie frame to remove paint on the bottom and grind down the die-cast seams. The battery died on the Dremel before I was done, so I plugged the battery into the charger and examined what I had done. This revealed yet another opportunity to excel! This simple model has no support rollers, bottom or top. I need to see how the real ones are shaped, but a single piece of .188" tubing cut to size already looks like an improvement. I think that the rollers will have to be a bit more complex than this, with a space down the middle. The rubber tracks have a raised guide in the center that engages the four wheels. The real track probably has a center guide on each track shoe, too. I have emailed the equipment dealer regarding a visit, so we will wait for a response and hope it is positive.