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Mack Truck B73 B75 AITM


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Hello model builders, 

 

A while ago, a guy went ahead and purchased a 1/25/24 scale Mack tractor from AITM.  I am not a big Mack truck enthusiast, but when I saw this kit, it reminded me very much of an experience I had with my dad and brother, likely more than 40 years ago.  Across town from where we lived was Hitchings Lumber - as the name suggests, it was lumber yard, but, not anything like the big-box mega stores we see today.  Instead, located in a rural part of the west side of town, a throwback from the past (even then!).  The yard seemed (as a youth) to be a big, overgrown place, with a gravel drive, lumber storage sheds, and a main office packed full of odds and ends, photos and wood burning stove.   In the yard and surroundings, were numerous Mack trucks in various states of repair.  But, there were always a few good looking, even shiny, vintage Mack trucks - which were their main service rigs.  So, when I found the kit, I decided I'd build a version of one of Mary Hitchings' lumber haulers.   I found the images below on-line:

 

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Yes, that's Mary Hitchings on the upper left.  As a boy, it was something of an adventure to visit the yard with my dad and brother, on what inevitably were cold and wet Saturday mornings - which we always enjoyed!  

 

This is the AITM kit:

 

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It is something of a mixed bag, as many small shop kits tend to be.  On one hand, they seem to have accurately captured the distinctive look and proportion of the somewhat iconic fenders - which is great.  On the other, some of the castings are a bit clunky, and have required some carving, filing and sanding, but, are for the most part true, and thankfully, not warped!

 

First up, I needed  😄 to make posable steering: 

 

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Mercifully, the material they used is fairly tough, but not so tough that it can't be worked with, so, off came the steering from the axle, and the knuckles.  Some clean up, and reassembled with a metal pin - I would have used a small bolt and but don't have any here right now.  Next will be to glue the steering control arms back on and make up a tie rod.  I'm going to try and make a drag link from the steering gear to the knuckle - not something to worry about just yet.

 

Then, I noticed in the photos, that the wheels on the front axle of the prototype are not spoked, so several months ago I ordered a set (incorrect version it turns out - too many small holes) from Auslowe (very nice BTW).  But, they were a bit too wide and either the tire or rim, or both wasn't round - so, fixed that (inside of wheeel):

 

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Maybe odd to do this so early but, a guy likes to have generally functional tires/wheels early on, as there always seem to be many test fits etc as we go.   The tires really don't look much like they are meant for the highway, so I'm going to do the right thing, and use them anyway - not in the mood to search for and buy another set of resin tires!   Then, on to some resin carving:

 

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The frame, leaf springs, and shocks, front and rear, were cast as one piece, so, I went ahead and cut out the necessary gaps - you can just see I did this for the shocks, while the frame/spring opening is obvious enough.   Less obvious is what's going on with the fenders.  The kit provides a stout block for mounting the fenders, which works well, but, doesn't match the fender outer contour, so it was cut and carved to match.

 

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The kit doesn't come with instructions, which is more or less OK, as fortunately I've built a few models.  It seems the kit would have you mount the cab interior to the frame, and then rest the cab on top of it.  I went ahead and changed that.  It seems the one piece interior might not actually be for this kit? I don't know - but, I didn't care for the fit.  I cut about 1/8" (3 or 4mm?) out of the vertical part, and glued the shortened version back together. Then, build a base and floor that would be attached directly to the cab, then to the frame - sort of like how you might with the real thing.  

 

Then, while taking these photos - I found a bigger problem:

 

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Well this isn't too good - something is amiss here.   The frame provides a distinct body locating point for the inside of the radiator.  These pics are of the cab lined up on that mark, and well - not so good.  Tho, you can see the outside of those modified wheels!  😄

What to do?  As I was looking at what I was taking photos of (all just taped together), tried relocating the body until it looked about right:

 

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That looks better - but, strangely, to look correct, the cab need to be mounted just inside the raised lip? - what's that all about???  well....I guess a guy will have to get after that and figure out how to make it work!

 

OK, thanks for having a look,

 

Cheers

Nick 

 

 

 

 

 

 

 

 

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IIRC, some of the AITM stuff (especially the Macks) dates back to the '70s and was first produced in fibreglass, so that's why the castings are fairly thick and crude by current standards.   Cab looks good where you have it, are the locators for the bumper?

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Hi @Six97s, interesting about the castings - maybe so?  As for the frame, it's just a basic box frame - there are no horns up front for the bumper, or much nuance in general.   I'm in the process of making some horns, tho I'm attaching them to the bumper first, which I'm modifying anyway.  As I began looking more at the parts, and thinking about your question, I wondered if rather than dropping the radiator over the raised lip on the frame (which is pretty straightforward), if you were supposed to carve the lower outside edge of the radiator to match the inside of the raised lip?  This would then leave a portion of the frame sticking forward, maybe to look like there are frame horns for the bumper?  I don't know - a guy went ahead and cut the "extra" frame distance off, and as noted, am reworking everything ahead of the radiator - 

 

take care

Nick 

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  • Stickframe changed the title to Mack Truck B73 B75 AITM

Hi Andy, and Jeroen, it turns out that the two parts/steps you mention are closely related.  Regarding the steering, my cutting technique has resulted in the need to add shims between the hub and axle to get the camber adjusted - ha! just like real life - but at this scale, a real challenge, which leads me to the body location.  It turns out the cast frame/leaf springs might be/are slightly out of alignment - both in terms of being perpendicular to the frame, and relative to left and right centering.  This meant that the axle was slightly askew to the frame and projecting outward on one side more than the other.  So, that's what I'm trying to fix now.

 

Yes Jeroen, that memory came right back when I saw the kit - ha!  My brother and I were helping my dad build a garden shed - not sure if exactly helping! ha, but dad kept us involved!  It was fun, and getting the lumber meant several trips to the yard!  

 

Take care and thanks for having a look,

 

Nick 

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I have no memories of helping my dad out with anything, because while his brain works very well indeed, his DIY skills are the worst! So one of my grandfathers always came over to fix stuff and I learned from him 🙂

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My dad was a very good amateur carpenter and general builder. His daytime job was builders-merchant manager. He basically ran the site!

He built several things in the house, including two fitted bedrooms and fitted kitchen, all from scratch. He built his own shed, again from scratch, including the foundations and last but not least, he built the extension to the house.

He just loved making things, I think. In later years, when he retired, he took up wood-turning as a hobby and turned out some very finely turned wooden objects.

When I was small, I did try to help and I did pick up some skills on the way. If I had the time, I would love to do some wood-working. Ah well, maybe when I finally retire ... sigh!

 

He very rarely had tradesmen in to do jobs, except for heating and electrical...

I think that he came from a generation who grew up during the war, and learned how to do things for himself. My generation were spared the war, but maybe missed out on the handiwork things.

 

Sorry, went off topic a bit (lot?).

 

Cheers,

Alan.

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@JeroenS and @Alan R, I don't think it's too far off topic at all!  As this is a hobby, and not a job!  It's a pretty interesting coincidence that I'm talking with my dad (he's proudly 83) right now about rebuilding another old garden shed - he has two, one we rebuilt about ten years ago - and, inside, not a garden tool to be seen - instead, his collection of model cars!  He began collecting them in the 50's - he was never a model builder, but a big Buick and automobiles in general enthusiast! lol - The shed we are discussing rebuilding is actually for garden tools and so on - 

 

Cheers

Nick 

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Ok back with some updates.

 

This has been an interesting build - the variances in parts quality has come to be a steady part of the challenges.  Nothing impossible, but a few that seem weird and might be pretty frustrating if you haven't done some scratch building before.  

 

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Starting with the 5th wheel, which by itself is pretty nice - except, it doesn't fit the frame? - offset by an 1/8" or so.  Again, not a disaster, but a bit of a nuisance.  To fix, cut off the kit landing tabs, file the opening, and replace with styrene set to the correct location, and back fill so that it doesn't look flimsy.  Next, the exhaust.  My prototype runs dual exhaust stacks - the kit came with one, so, I ordered another - fair enough.  Except, well, the second version didn't match the first, and the cast quality was pretty bad.  You can see in the upper center, the tall stacks weren't the same height, and the lower parts didn't face the same direction.  I cut off the tops anyway, as my version runs straight pipes, so on went some alu tubing.  The bottom - easy enough - cut the parts off, and pin in place in the desired direction.  As to the cast seam - you can see in the lower left, a piece of evergreen fit in place.  As my version will have a shield that will eventually cover this huge seam, it was more or less ok - but, imagine if you wanted this part exposed - what a PITA to clean up. 

 

OK enough griping on this subject - on to the front steering:

 

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I generally enjoy fiddling with suspension and steering, so I was up for this.  As I mentioned before a few subtle problems emerged - it sure didn't seem the mounting positions for the front axle on the leaf springs were dialed in correctly.  Seem to have been a bit off center from the frame, making the wheels stick out different distances, and the height of the of the leafs didn't seem to match - perfect.  So, a guy fooled around with this for quite a while.  Making this more tedious, you can see I added U-bolts from wire, plates using thin alu, and nuts.  Only mention this because getting these bits to line up is nerve wracking to begin with, then needing to add shims, realign, file repeat became frustrating.  Nonetheless, got it where I wanted it.  Leading to steering - well  you can see I added a pitman and drag link from the steering gear which was fun to figure out, then added the tie rod.  Before this was done, I also added camber adjusting shims on the driver's side, which seemed to refuse to "pose" in the vertical position - more thin alu sheet to the rescue - cut, file, drill, punch, bend, and keep doing until: 1) you break the part; 2) you finally get the right part to fit and get glued in place 😀

 

On to the rear axle:

 

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This was a lot easier to do - added hard and soft brake lines, some bolt heads and never to be seen U-bolt segments!  Couldn't resist adding some "c" rings/clips to the U-joints 😀

 

And now we have the basics for a rolling chassis:

 

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I also carved and sanded the sidewall corners to make this look more like a highway tire.  Have thought about carving another line into the tread pattern on those front tires.....that does not seem like a pleasant task.  More chunks of resin to cut off here and there - like on the top bolt mount on that front shock mount!  You can also see here what I did with the the front of the frame.  Cut off a bit, and add the piece of styrene as a locator for the hood.  The carved up the front a bit to make something like frame  horns for the bumper.  

 

Anyway, there are plenty of things to get after - 

 

Take care and thanks for having a look,

 

Nick 

 

 

 

 

 

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That is some incredibly nice work on the front axle assembly sir. It all looks very convincing and I'm sure that with a little more tweaking of those rougher parts you'll make it all look good. This build will be dominated by that awesome cab body anyway so this will work out just fine!

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Thanks, Jeroen, we're getting after it - one bit at a time - thought I'd post progress on the pipes:

 

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As you can see, the various imperfections in the casting are now hard to see!  I added some thin strips of styrene in strategic locations, then added some very thin alu screen mesh, and then made bands out lead foil from a vine bottle - and now, some decent looking pipes!  The thick brass rods on the bottom mount to the frame, and the arms on top now have some brass rivets to mount to the cab.  The really small pins will be used from some studs, then more pipe,   I'm going to paint these black then hit with some Vallejo metal chrome - fingers crossed!

 

Thanks for looking,

 

Nick 

 

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Well guys, today, really the last two weeks, no fun at all!  I'm fairly good at doing my real job and not good at all at the administrative side of it!  Have been dealing with quarterly tax fillings, and 1099 forms...misery!  While I can comfortably spend plenty of time doing my actual job, or building models 😄, ask me to competently fill out forms, and that's another story!  I seem to have a huge mental block when it comes to doing those tasks....very discouraging - but, something that needs to be done! and now is!

 

OK enough  - back to the ol' Mack:

 

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And you can see more styrene.  I built up the front bumper - which I now see still needs more putty, built battery and service boxes, and the "headache rack" separating the load from the cab.  It's interesting that for such a chunky model a surprising level of precision has been required to make all this fit where it belongs and to make it look as it should.  And with the cab:

 

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The small tank next to the hood on the drivers side is for either hydraulic steering fluid, or a diesel filter - I don't know, but, whatever it is, this truck has one!  On the passenger side, you can see the big air filter and plumbing to get it under the hood.  The prototype actually has that big square opening, which in retrospect is just fine - as the resin is very thick, so cutting a credible circle for the plumbing would have been a challenge.  Next - those pipes - I've since done more work on them - both in terms of appearance, via the last post, and in regard to getting them plumb - now they look right.

 

Still more to do on the cab - horns, mirrors, trim for windows, and detail trim along the hood - and other stuff no doubt - all of which is better than dealing with tax forms!

 

Thanks for having a look!

 

Cheers

Nick 

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This is looking great already, even without paint. I like the "compact" look of it, short wheelbase, big cab. 

 

Good luck with the forms 🙂 ... I fully sympathize. Luckily I don't have to deal with any of that in my job, and my wife handles all such stuff in our personal lives which is for the best. 

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@silver911, well Ron, you certainly raise a good point! 😄  yes, the drill....😄  Such an exotic tool - seems I've grown so accustomed to using tiny hand tools (pin vice, knife etc) that I forgot all about real tools!  Yes, I do own a cordless drill, and several bits - just forgot about them!  I tend to drill a small pilot hole, then use a larger bit in the pin vice, then go about enlarging the diameter using various knives and files!  hmmmmm....not all that bright of me!

 

@JeroenS, hi Jeroen, glad you like it!  I concur - the big cab on the short frame does have a distinct look!  rather like the "bulldog" namesake - lol

 

thanks for having a look

 

Nick 

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