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Cat D7R build
Stickframe
#362
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California, United States
Joined: December 01, 2013
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Posted: Wednesday, June 10, 2020 - 01:18 PM UTC
Hello fellow model builders.

Well, in these strange times, a guy needs to figure out how to make sense of it all. Between working from home and staying at home, I was debating about what to start, and the post office helped make the decision. An AMT CAT D8 arrived on Monday. The plan is to "convert" it to a CAT D7R. I'm not sure if this is actually a conversion, and instead, really more about borrowing parts, then cutting them up, and scratch building.

A few weeks ago, I did some research and concluded a guy could probably start with the D8 kit, and go from there. There are numerous differences between these two dozers, including the most obvious, which is the elevated final drive sprocket on the D7R.

I went with the D7 rather than the D8 or 9 because of size - and adaptability of the base kit - including the number of track links/shoes provided in the kit and the number required in the adaptation. It also turns out the overall height, and length of tracks on the ground is fairly close between the two, so I'm off and running.

I have some pictures I'd like to post, but am running into the server problems with the Gallery that happened a few months ago - I'll keep trying. Ok - gallery is back - this is the D7R:

Gallery down again......



Well, as a guy has to wait, I'll write about what I did. First up, some homework, trying to establish the overall dimensions and diagrams of the D7R and then converting them to 1/25 scale.



My first task was to build one set of track links and put them over a copy of the dozer to scale - so far so good - they appear to fit. I'll say they go together a lot easier than they do in 1/35 scale, flexible armor tracks - but, they suffer from a real lack of detail and are pretty toy-like. The grousers are big and clunky, no bolts are shown on the shoes, and the chain - the basic shape is right, but the there are none of holes that the real version has.

So, I filed down the grousers -just so they are thinner at the peak, and now at an angle. They look less toy like. I'll add the 320!!! bolts to the shoes - yep, four per shoe...no doubt good times there.

Next, the D7 idlers and drive sprockets are smaller in diameter than the D8, so, I took about 1/4 off of the overall diameter of each. Tedious, tedious task!! and of course, that meant I had to carve a new teeth into the drive sprocket - in a visually convincing way. So - the sprockets reworked, and the idlers, cut down and an inside added, just to increase their overall thickness.

The kit running gear looks pretty good - the rollers, details etc look good for the D8, but are not at all right for the D7 - so, after mulling it over for a while, figured out with some cutting and reworking, a guy could make them look "similar" to that of the D7R -

Sorry- I'll dump photos in while the server is up:



















Sorry about the chaotic order of the images - the server was working, so, this guy decided better to post in a hurry than fuss about.

Above, you can see the comparison of the kit suspension (rails, rollers, Idler mounts, and rock guards, and then, how I changed them to look closer to "right". I need to add the tensioners and all sorts of stuff still.

You can also see the new planetary hubs for the drive sprocket - all sorts of stuff going on there, and fun to do. The hub itself is cut sections from an old spool of copper wire - got luck the dimension was spot on and they accept Testors liquid glue.

Finally, the chassis. The D7R is shorter than D8, so, I cut it down. The evergreen will eventually serve s the bearing block pillows for the pivot shaft, which crosses the full chassis. Several other changes need to be made - ranging from simple body panels to ROPS and so on.

I discovered that the equalizer needs to be modified and moved forward - of course, only to the "other" side of the kit's brackets - perfect. It also attaches to the chain rails differently than on the D8 - so, more changes.

Anyway, as it's early in the build, and I'm optimistic - that said, I can already tell the suspension - will be one of those projects where it would be nice to have a third hand!!

So, here we go!

Cheers and stay well -

Nick
Cosimodo
#335
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Auckland, New Zealand
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Posted: Wednesday, June 10, 2020 - 05:10 PM UTC
Hi Nick,
This looks like a challenging build with a number of modifications required. I'm impressed by your ability to assess the requirements, design the changes and implement. I don't know the first thing about CAT machines but they look mighty impressive. Looking forward to you working Haskell magic on this.

cheers
Michael
jimb
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Posted: Thursday, June 11, 2020 - 12:13 AM UTC
Great looking conversion. Looks like you have your work cut out for you.

Jim
AussieReg
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AUTOMODELER
#007
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Victoria, Australia
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Posted: Thursday, June 11, 2020 - 01:19 AM UTC
Wow Nick! The words "Go Hard or Go Home" come to mind. What a challenge you've taken on there, I'm definitely going to be following closely.

Great start.

Cheers, D
KoSprueOne
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Myanmar
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Posted: Thursday, June 11, 2020 - 12:56 PM UTC
Cool project. I'll be following and taking notes.




Joel_W
Staff MemberAssociate Editor
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Posted: Friday, June 12, 2020 - 01:14 AM UTC
Nick,
I know next to nothing about trucks, and even less about trackers. Yet, you peaked my interest with this most unusual Cat D7R conversion. Every Cat bulldozer I've ever seen had more mud, dirt, and what not all over them, especially the tracks and running gear, that I never really took the time to look at them as a modeling possibility, but you've already changed my mind about heavy construction machinery.

It always amazes me how you can scale out even the simplest drawings to a workable set of plans.

Your conversion work on the drive train is just amazing as usual. while I'll confess to total ignorance in knowing what parts you're referring to at times with unfamiliar names, the pictures are a tremendous help.

As for the Gallery issues, the site as a whole has been experiencing server related issues causing very long loading times, as well as from what you have said about the Gallery as well. I've been in contact with Jim, and he's hard at work on trying to resolve those issues.

Joel
Stickframe
#362
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California, United States
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Posted: Wednesday, June 17, 2020 - 06:20 AM UTC
Hello guys,

I mentioned at the beginning of this build that the postal service essentially guided this build to be first up - thought you'd get a kick out of this picture:



Evidently the authorities get anxious if you order a couple of multi-media kits from Germany! lol - they nearly destroyed some of the resin body parts when they "repackaged" all of this, but not problems!....only off-set by the two month delivery time! lol

Ok, on to the bulldozer. Plenty of progress to report - and touching on the points that you guys noted - D, yes, it seems a guy needs to jump right in to build like this, as Michael, Jim and Joel note, without having any "real" shop drawings or machine tools - or the really fancy CNC, laser cutters, or 3d printers, well, you do what you can do. A guy just needs to start and find out what happens.

With this comes a certain give and take - that is, starting with a model of an old dozer, to make a newer vintage dozer - aside from the manufacturer (CAT) and the label "D" there is practically nothing similar between the two - nor should there be - like comparing a Corvair to a Corvette - both Chevy's....with names starting with the letter "C", but that's about it.

As such, my recurrent goal of creating convincing realism over precise detail is the rule of the day. While researching this, I've concluded that should someone really want to build this with precision, a guy probably could - step one: get an autocad or similar version of the plan...and so on - which is not for me.

OK, here we go:









As you can see above, the process starts with getting the fundamental "chunky" parts right, or at least proportionally more or less correct. It turns out, I cut about an inch of the rear of the kit frame, and added about an inch to the front. This was a hit and miss process.

If you look at the last post, you'll see I thought the rear would work as is - wrong - it looked wrong, so out came the saw!

Another important note is to use the right, or most useful materials for the job. The fender flares on the Ford F150 were done with the paper thin .010" evergreen, while this is the .040". In addition to looking correct, the material is serving a structural role, supporting the build, and standing up to the build process - like cutting, drilling, filing etc once it's glued in place.

On we go:



This image gets some text. These are the hood sides, which have screen - and it turns out the material I had on hand is fairly airy. This means, the engine will be more visible than I had anticipated. If this were an F1 car, that would be great. Unfortunately, this involves a big diesel engine, which I know very little about. So, back to google - what does this engine look like? Absolutely nothing like what comes in the kit!! Again, think Corvair vs Corvette - they are just different.

I of course discovered this once the basic engine (which I had fortunately already cut down a bit) was glued in the frame - hmmm....out came the knife and off came the top of the block, and all of the external parts, with the block still glued in the frame. Good times.

There are three distinctive visual features of the new version: 1) the top of the block (I'm assuming injection/air intake etc??) slopes down, forward; 2) the turbo is on the right side - and sits fairly low on the block; and, 3) the intake/air cleaner is on the left side - with a clearly evident cross-over air intake. So, that's what I made.

Ok, on we go:



Above, you can see the build as of now, with a copy of my scale prototype taped in the background. This is the side with the turbo, but for this photo, the left hood side is in place.

Now a walk around:



What's funny about this build has been going back and forth between thick, chunky, not at all delicate plastic, and numerous tiny bolt heads!!


Well....server down again. Not a big deal - I need to get this posted in the next 30 minutes as I need to be on a conf call, but I have some time.









And there you have it. This project reminds me of some advice by Jerry Rutman (a truly talented model and master figure builder - amazing work and a good guy!), who emphasized the importance of practice. If I tried this a only few years ago, there is no way it would be as relatively clean, tidy and proportional as it is. Clearly there are many errors, but the basic structure seems to be coming right along.

OK gents, a guy needs to get on a call to help pay the bills! (doing some real work!!)

Cheers, and stay well,

Nick
rv1963
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New York, United States
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Posted: Wednesday, June 17, 2020 - 07:30 AM UTC
Nick, Well done, that's some nice scratch building.
Dixon66
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New Hampshire, United States
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Posted: Wednesday, June 17, 2020 - 08:25 AM UTC
Holy frak! Enough said.
AussieReg
Staff MemberAssociate Editor
AUTOMODELER
#007
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Victoria, Australia
Joined: June 09, 2009
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Posted: Wednesday, June 17, 2020 - 10:43 AM UTC
Some serious styrenology taking place here Nick, love it!
Stickframe
#362
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California, United States
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Posted: Monday, June 22, 2020 - 11:57 AM UTC
Hello gents,

Glad you guys like what's going on here. It's certainly a challenge! especially when compared to the intricate and complex F1 cars I've been fooling around with. This is the opposite - I kid you not, this build has already consumed about half a bottle of Testors glue! instead of fussing about with the number 78/82 drill bits and fine connections - this is thick, heavy styrene sheet material and a lot of it. The nuance hasn't been about fine connections, instead, getting the shape to look right. At first glance, this might look like a big clunky beast, but once you get into it, you'll find there is a distinct pattern and characteristic form.

So, for today's adventure - a guy just couldn't live with the rail frames - I thought I was close, but - honestly, it really wasn't. So, out came the file, saw, and knife, and off came most of the assembly for the front idlers - it just looked wrong. It's still not exactly right, but it's closer.

Next - the cabin. It turns out that many of the components of this tractor in real life are modular, including the cabin housing. So, I built the cabin shell and driver's area as two separate units. The basic pattern is derived from the template I showed in the previous post, wed to the basic frame/chassis I scratch built. The interior is not anything like the kit. I kept the seat, kitbashed and scratch built the rest.

Then, building the fuel tank etc that surrounds the cabin. This area is more complicated than it might appear as it's both angular and stepped - it also needs to be set high enough above the final drive sprocket to allow the rails and shoes (tracks) to fit. Making this more tedious was that the kit tracks - have toy-like grousers (the vertical blades on each track shoe) - ridiculous. They are too tall and wide. I just can't figure out how to modify them in a remotely efficient way - either in terms of cutting them up, or making new parts altogether - hmmm.

The area next to the cab also includes mounting points for the roll bar. Like my other projects, I concluded that a guy couldn't just build the roll bar and glue it in place - that is a recipe for me to wreck the build - I can essentially guarantee that I would knock that roll bar off. So, instead, I cut into the body parts, and made chassis attachment points. Another "clever" idea....that took some head scratching, but so far so good.

Finally, I added some etch material from old kits to the cabin area, and for the roof cap, a sheet of thin brass cut to match, and then the rear sil, attached with some small brass rivets - again, while it looks pretty cool, the reality is that a guy would no doubt knock the part off if it were just glued in place.

Ok, enough words, on we go. First some WIP images - even in the pics you can see how thick the styrene is:











And now, a few with the cabin buttoned up:











Next, I'm not sure, either the rear PTO / hydraulic winch? or a ripper?; or, the blade and front hydraulic cylinders?; or - the "C" frame. Regarding the latter, the base kit includes two separate arms, that attach the roller frames to the blade, but the new version - nope, a one piece, "C" shaped frame that connects to the roller frames, to which the blade is attached is used. A guy could find himself in deep...mud - trying to build that "C" frame. It will likely be a pair of one piece frame templates, made from .040 sheet, sandwiched to .188 x .30 strips - piece of cake.

OK gents, stay well -

Cheers
Nick
Dixon66
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New Hampshire, United States
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Posted: Monday, June 22, 2020 - 02:30 PM UTC
Looking great Nick, you are definitely keeping Evergreen in business.
rdt1953
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Posted: Monday, June 22, 2020 - 07:37 PM UTC
Hi Nick -
Iíve been watching this with great interest. Very nice work indeed .
I donít know about the D7 but the in the D6 I got to play with the operatorís seat is not square across the machine but is at an angle to reduce neck fatigue as bulldozer operators are looking to the rear nearly as often as looking forward .
Keep at it ! - Richard
Stickframe
#362
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California, United States
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Posted: Tuesday, June 23, 2020 - 05:52 PM UTC
Hi David, yes, this project is eating up lots of evergreen - it's a
great material source. It's fairly remarkable how much you can squeeze out of basic raw material with enough head scratching lol

Hi Richard, thanks for checking it out. You raise a really interesting question about the driver's seat - I don't know if it's set off axis, but it would sure make sense if it were. I've been using several photos for reference, like this:



After reading your comment, I went back and looked at my resource images and can't tell if it's off axis or not? I tried to "fake in" something that looks close, but, if it were off axis, that would have been a nice detail to try!

Based on this and other photos, I can tell the seat is adjustable up and down, maybe even an air ride of some type? I don't know - if you look back at the images you can see I added some half round material to look like the rubber base and some small channel for the adjusting tracks - hmmm. I guess it's too late now to carve the seat out to set it off-axis. All things considered, it was a relatively tight fit - and you can see, I salvaged the kit seat -

Shoot! you know what? I've built the Meng D9R (a great kit btw) - I could look on line for the instructions and see what they did? I can't see into the cabin on my build - it's weathered and has an RPG cage - thinking about that, here it is built - I used it as part of a Ca 2004 US Army version used for select battles in Sadr City:









Something worth noting on the D9 is the more accurate portrayal of the grousers - they "look" right - I need to figure out how to fix the grousers on this kit - paint and weathering might help, but I'm not convinced that will do the trick.

Take care -

Nick
Cosimodo
#335
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Auckland, New Zealand
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Posted: Wednesday, June 24, 2020 - 12:22 PM UTC
Amazing watch this CAT develop. Great explanations of how you approach the various requirements and seeing the outcomes realized in styrene is pretty cool.
The military version you done is looks incredible - photo realistic I would say - as is its setting.

cheers
Michael
Stickframe
#362
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California, United States
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Posted: Wednesday, June 24, 2020 - 02:45 PM UTC
Hi Michael - thanks. The D9 dio was a big project, opening up all sorts of challenges, including taking a shot at weathering that Cat!

I've been around a lot of equipment and have spent time in that part of the world, and paid attention to what real "weathering" looks like on heavy equipment - on one hand, making it engulfed in dust is essential, and obvious, broad scrapes (both surface and to the metal) in some areas, and really very clean in others.

And as it's depicting something in use, more raw metal than rust where the scrapes can be seen. I really enjoyed building that. I think this will get some weather too - no reason for a guy to have a "showroom Cat"! that iron is meant to be used - lol

Hi Richard, speaking of the Meng kit, I found this in the instructions:



It's hard to tell if the seat is off-axis or not in this image? But the foot rests on the deck, are asymmetrical! maybe the seat is too? oh well....maybe next time!

Cheers
Nick
2002hummer
#257
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Ontario, Canada
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Posted: Wednesday, June 24, 2020 - 05:12 PM UTC
Great build Nick. just found your build but will follow it. I wish I could build have as good as you. I am still in the OOB stage with a few mods.
Stickframe
#362
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California, United States
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Posted: Sunday, July 12, 2020 - 07:14 AM UTC
Hi guys,

Despite the quarantine in place, I've had some things to do, so work on the D7 has been slow, but not stopped.

Hi Darrell, well, I started with straight OOB too, and gradually began adding this and that, and eventually tried to go beyond. It's always hit or miss, and requires some head scratching along the way

As for updates, I've got a minute, as the gallery seems to be busy, which is frustrating, but I understand the Kitmaker staff is aware of, and is trying to address it.

So, while I wait, some notes on progress. You'll see the front end and blade is well underway. I built some hydraulics. This wasn't specifically hard to do, but getting the alignments on mark was a challenge - you'll see it's just temporarily held together and I need to add more hydraulic lines and some bolts etc -

Next will be the rear end. I'm considering adding some rippers, or a winch - I haven't decided just yet. I ordered some parts for the ripper, that would be 3d printed - but this has been really slow - I might just build something myself -











OK- a speed post - the gallery was up!

So, a guy has some decisions to make, and still a while to go before buttoning this one up -

Stay well and keep building

Cheers
Nick
jimb
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New York, United States
Joined: August 25, 2006
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Posted: Sunday, July 12, 2020 - 08:57 AM UTC
Fantastic work on your dozer, Nick. It's really coming along.

Jim
AussieReg
Staff MemberAssociate Editor
AUTOMODELER
#007
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Victoria, Australia
Joined: June 09, 2009
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Posted: Sunday, July 12, 2020 - 10:44 AM UTC
Looking great Nick, outstanding scratch building as always!

Cheers, D
Cosimodo
#335
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Auckland, New Zealand
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Posted: Sunday, July 12, 2020 - 09:08 PM UTC
The hydraulics look amazing. They really stand out for me as a great piece of scratch building. I'd like to see you build the rippers off the back.

cheers
Michael
Stickframe
#362
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California, United States
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Posted: Thursday, August 20, 2020 - 09:11 AM UTC
Hello gents,

thanks for the positive words - certainly an interesting, and big build!

Michael, funny you'd mention the ripper. I found a guy online who sells a set of printed rippers for a normal D8. I figured I could buy them and adapt to this. Long story short, I ordered the parts on June 3 - by mid July was told they'd be sent out the week of July 20 - and here we are - no ripper from him. I called Paypal and cancelled the payment. The next email (post opening complaint with Paypal) I received from the guy encouraged me not to worry, it's no big deal and, it's only xyz$. If that's his attitude, he doesn't deserve my money. He's right, it's not about the money, it's about following up on his word.

So, now having spent only a few bucks for evergreen, some aluminum tube, solder wire, and a couple of days on and off, here we have it:







That could have easily been built to be movable - getting the geometry more or less right, allowed it to go together pretty smoothly. You can see I kept a few of the original kit parts. The mounting arms were cut down about 1/2" and two of the hydraulic cylinders cut about 1/4". Below, you can see the model and the working diagram. I chose to model this in the lifted position - just for convenience when it's done:



For a scale reference, next to the Ford PU. The Cat is just big, in all directions, but the scale looks about right:



I need to cut out some windows and then will be ready for paint. Unhappily, we are in what seems to be another "new normal" here, hot weather and wildfires, so the air outside is dense with ash/smoke, so I'll hold off painting until this blows through.

In the meantime, will get back on the Peterbilt.

Stay well and happy model building gents -

Cheers
Nick
AussieReg
Staff MemberAssociate Editor
AUTOMODELER
#007
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Victoria, Australia
Joined: June 09, 2009
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Posted: Thursday, August 20, 2020 - 11:02 AM UTC

Quoted Text

The next email (post opening complaint with Paypal) I received from the guy encouraged me not to worry, it's no big deal and, it's only xyz$.



It might be only xyz$$, but it's better in the hands of another seller if that's his attitude!

The outstanding construction continues here Nick, just amazing work with basically stock sheet and shapes. I love it!

Cheers, D
Cosimodo
#335
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Auckland, New Zealand
Joined: September 03, 2013
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Posted: Thursday, August 20, 2020 - 12:40 PM UTC
I wonder, and doubt, that they would have been as good the ones you have built. Great detail in the blades and hydraulics!

cheers
Michael
ti
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Dalarnas, Sweden
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Posted: Sunday, August 30, 2020 - 09:18 PM UTC
You always surprise me with your scratch building abilities. You are a great inspiration.