Been running this topic on building the Oshkosh 4x4 vehicle as part of a Mk23 8x8 16.5 ton LHS truck conversion over at:

http://armorama.kitmaker.net/forums/252818

Thought it might be appropriate to give the topic its' own thread.

Dimensional Drawing:


4x4 Short bed

It seems that Oshkosh has offered this vehicle in a number of forms to the military with primarily the US Navy and Marines accepting some, but not all variants:



4x4 Short bed (Not accepted as standard.)
6x6 Standard Cargo Truck, 7 ton (Mk23 or Mk25 w/winch)
6x6 Long wheelbase cargo variant, 7 ton (Mk27 or Mk28 w/winch)
6x6 Long wheelbase with LHS Load Handling System; 9 ton (Mk??)
8x8 Long wheelbase with LHS Load Handling System; 16.5 ton (Mk??)
6x6 Semi-tractor (Mk31)
6x6 Dump truck (Mr29 or Mk30 w/winch)
6x6 Wrecker (Mk36)
HIMARS missile launch vehicle (Mk37)
HIMARS missile resupply vehicle (Mk37)

All have options for armored cabs, extended cabs, recovery winch and 4, or 6 wheel steering!

Standard 6x6 cargo variant; 7 ton


Long wheelbase 6x6 cargo variant; 7 ton


8x8 Extended frame LHS; 16.5 ton


6x6 Extended frame LHS; 9 ton (Photo by rcsadmedia)


6x6 Standard cab Semi-tractor with either two or four wheel steering


6x6 Extended cab Semi-tractor with either two or four wheel steering (British Military version shown here.)


6x6 Dump variant; 7 ton


6x6 Wrecker (Mk36)


HIMARS Resupply Vehicle (Mk37)

[quote] H.P.
On a side note, I guess the 4x4 variant was the one used as a base by Oshkosh for their TerraMax UGV (Unmanned Ground Vehicle) to compete in the DARPA Urban Challenge 2007 edition :


This prototype was fitted with a steerable rear axle :

https://www.youtube.com/watch?v=CSPd6TyXPAo

[End quote}

Post submitted by Henri-Pierre elsewhere on the Armorama website and copied to here.

Trumpeter makes an outstanding model of the MTVR Mk23 in 1/35th scale for us to use as a starting point for ALL these many variants;

OK, they don't include the gun shown on the boxart, they don't include an engine and the hood (engine bonnet) doesn't have working hinges but that's just me being cranky!

All that being said, the production design engineering of this kit is nothing short of 21st century industrial perfection! Crisp moulding, a near perfect fit, a wealth of detail and an ample parts count that makes for an excellent finished model!

As said elsewhere, I am also in the process of building the four axle, 16.5 ton US Marine LHS. This required the purchase of a second MTVR kit to obtain the necessary additional drive axle.







And that left me with . . .

. . . the perfect selection of parts to build the Oshkosh 4x4 truck with TAK-4 suspension. (Two or four wheel steering, short bed, long bed - whatever we might want to build.*)


Shown here is an extremely unusual extended wheelbase 4x4 with the full sized Mk23 loadbed.

* Oshkosh has tried continuously to find just the right combination of wheelbase, independent suspension,
multi-wheel drive and box length to satisfy every military requirement.

Started the project by cutting out and removing the frame section for the forward of the two rear axles to produce a reduced frame length of 265 scale inches for the much shorter 4x4 truck.





You can probably see that I cut my frame in a number of places. You will need to cut yours only twice to achieve the desired length. However I was trying to salvage certain particular portions of the frame to use for my big 8x8 LHS project.

You can also see that I added some white Evergreen plastic reinforcement plates to the inside surface of the loadbox support beams, (located above the frame members, they allowed me to make the patch joints stronger without changing the look of the "C" channel frame itself.

SIDEBAR REGARDING THE ENGINE:

Like I said the model comes with no engine - for me, worse than that, what engine there is is just an oil pan with the rest of the space filled in by a blank plate. I like to be able to see up through the engine area on my vehicles. I have encountered this before and my usual course of action is to cut out this blank area and to build up additional 3D depth to the engine area.


Engine and Transmission as offered in the kit, (with the area to be removed shown in white.)


My cutouts leave six attachment points for "engine mounts."


Mechanic's bottom side view.

. . . . . . . The modeler could easily stop right here, engine wise, and still have an improved model . . . . . . .


Beyond that I built in more depth to the engine and transmission.

Now Mike, you know that skipping the engine makes the project go a whole lot faster!

OK Doc, I fully admit I overdo a lot of things in my model making - but for whatever reason, "I just gotta do it."

In this case I am just showing possible options that others may choose to include or to bypass.

Frame construction coming along on the Bobber 4x4.

Here a comparison in relative size between the big 8x8 LHS and the Oshkosh 4x4:

Here is where my engine modifications stand as of today on the 4x4 "Bobber." I think this is as far as my engine work will probably go on this model.

If I ever happen to build a third one of these trucks (not likely - though I do now have enough extra parts left over to build the long wheelbase extended loadbox variant.) Perhaps by then there will be an after market CAT C12, in-line 6 cyl. diesel engine available
or . . . I might even scratch build an engine after doing the proper research.

Unique Oshkosh independent suspension now being applied to many US military vehicles:


Same suspension unit on the Trumpeter scale model:

Front suspension/steering unit complete:


Rear fixed (non steering) suspension unit complete:

Right side view; frame and front axle assembly:


Right side view; rear frame and axle assembly:

Top view of 4x4 frame with some component callouts:


While these vehicles all have lifting/tie down points at the front and rear bumpers, the hood (bonnet) being fiberglass, necessitates additional upper front lifting points be provided when slinging the vehicle from overhead. If attached to the front bumper the front lifting slings would crush the light weight hood assembly.


(Photo by military-mashup.com)

Some progress last night:

Lengthened and installed the new rear driveshaft:


Also added hydraulic hoses to connect the two steering gearboxes:

One additional change:


I modified the primary steering gearbox. The head of the Trumpeter gearbox is molded flat at a zero angle due to plastic mold/casting restrictions. In actually this head should be rotated approximately 30 degrees upward. Also missing is the universal joint and steering column that connects from here up into the cab floor. (To be built and added later.)

________________________________________________________________________________________________


Talking about steering gear on the Mk23:


Main driver controlled steering gearbox.


Secondary slave steering gearbox.

Also started on the cab and cab seating:

I tried to give the driver's seat a more natural "used" texture and profile. Still working on the passenger seat.

A construction tip / suggestion:


Consider adding these two .060 shims between the cab kickboard and the fenders.


Adding these shims allows you to attach the fenders to the floorboard without also gluing them to the cab body.

This will allow the cab floor and the fenders to remain separate from the cab so you can continue to have access to the cab interior and to add the window glass at a later time.





You can even permanently mount the floorboard and fenders to the vehicle chassis and still be able to remove the cab when necessary.

Its coming along nicely. Keep at it.

I am trying to dress up both cab seats with a little extra detail:

Added wrinkles, mounting brackets, edge trim and more than a few irregularities to give the seats a more "used" look. I feel that so often model vehicle seats look like nothing more than big square blocks of cheese with little or no detail coming from the hobby companies.



F.Y.I - Just in case you would like to pose the passenger seat
to accommodate a topside gunner:

This is what it could look like with the back folded down.

(Second photo taken of the cab seating in my 16.5 ton LHS.)

Thanks Gino. I am really enjoying this dual build!

Mike