Toyota 4Runner Project

Page 1:  Chassis Construction

   

The Enduro chassis box is very modestly decorated on the outside with only text and no graphics or pictures.  This is in contrast to the RTR box which is full of color pictures.  The inside of the box, on the other hand, features graphics of a scale garage which can be used as a display for your truck.  With no body or tires in the box, the contents are just a series of bagged sequential plastic parts and hardware which don't look like much.




Here are the contents laid out on my table ready for building.  Each bag contains the parts for a series of steps, grouped in logical subassemblies.  The manual is black and white shaded drawings which are very clear.


   

The build begins with the ladder frame chassis and the formed steel chassis rails.  These are assembled with a series of plastic cross members and skid plate as shown on the right.  You can see that the skid plate is heavily reinforced.  All of the plastics in this kit are black, but stronger versions of everything are available in a gray plastic.  I can't really imagine breaking any of these parts so I've left them alone.  The shock towers and floor boards have also been installed.


   

This close-up of the front shock towers shows some of the adjustability inherent in the model.  The tower in installed in the forward most of three sets of mounting holes.  Moving it aft would reduce the wheelbase.  The shock tower itself also has two holes to choose from for mounting the upper end of the front damper.  The towers can also be swapped left to right to change the relative position of the body post holes.  The right hand image shows the adjustability in the rock sliders from below.


   

The kit comes with two battery boxes, one for a standard sized battery and one for a shorty pack.  I chose the larger option and attached it to the forward cross member as shown.  At this point the chassis mounted steering servo and radio box have also been installed.  The empty spot next to the steering servo is for an optional servo winch.




The "Stealth X" transmission is one of the stars of this model.  The three pairs of huge steel gears shown represent optional assemblies.  Using the 52:28T gear pair results in an equal front and rear axle speed (no overdrive).  Using the 53:27T option (stock per the manual) reduces the speed of the rear axle for a 5.7% overdrive.  Using the 54:26T option would be an even higher 11.8% overdrive.  I used the middle set of gears for a factory 5.7% overdrive.  It is pretty impressive that the kit includes all three optional sets of gears because these are certainly expensive parts to just have sitting around extra.  The entire transmission can also be built to have the motor facing either forward or backward.  I'm not sure what difference it makes other than balance or to allow room for a vehicle interior.  I used the standard forward facing option.


   

Here are the output shaft (large gears) and counter shaft (small gears) assemblies.  You can see the very slight difference (1 tooth) in size between the front and rear gears.  On the right, you can see these assemblies installed into the gearbox housing along with the 20T input shaft.  The input gear drives the front counter shaft gear directly.  Both front and rear gears are locked to the counter shaft so they rotate at the same speed.  On the output shaft, on the other hand, the two gears are on the same axis but there are bearings between them allowing them to rotate at different speeds.


   

The input shaft is connected directly to the 87T spur gear through what looks like, but isn't, a slipper clutch.  Although clearly designed to allow the use of a slipper clutch, there are no friction plates and no clamping spring so the spur gear is locked to the shaft through the plastic pads.  Although it can't slip, passing the torque through the plastic pads probably provides some cushion from the forces associated with dynamic impacts.  I used a Reedy 5-slot, 20T crawler motor to keep everything in the Team Associated family.  The kit doesn't come with a pinion gear but recommends an 18T 48p gear so that's what I used.  Steel of course.  Transmission ratios are therefore:

The right hand image shows the transmission installed onto the chassis skid plate along with my Hobbywing 1080 crawler speed controller.  Many builds have the electronics installed last, so it is interesting to see a kit which does all of this first.  At this point the electronics are completely functional so the model can be powered up and tested.  Of course, the outputs don't go anywhere yet.


   

Now we can start on the axles, beginning with the more complex front.  The locker uses a spiral cut steel gear as shown on the left, and the plastic axle housing has a very nice integrated overhead stiffening brace.  The axles are large diameter steel rods with universal joints as shown on the right.  The 30T ring and 8T pinion result in an additional 3.75:1 reduction.


   

These pictures show some of the suspension geometry.  The side view picture on the left shows the caster angle.  This can be adjusted by rotating the caster block on the serrated axle housing.  The front view picture on the right shows the kingpin inclination.  Note that this does not result in a negative camber angle.  Instead, this makes the wheel rise slightly as a function of steering angle which, in turn, makes straight ahead the most stable position.  Ideally, the steering axis should also intersect the ground in the middle of the contact patch of the tire.  This makes the tire pivot in place when turning instead of swinging through an arc.  This would be a zero scrub radius.


   

The left hand picture shows the completed front axle.  The steering cranks are separately installed aluminum plates.  The rear axle on the right is a simpler version of the front with straight axle shafts.


   

Time to build a massive pile of links.  The kit includes 5mm solid steel links to build the chassis in any of three wheelbase options: 11.8" (300mm), 12" (305mm), or 12.3" (313mm).  I'm using the longest wheelbase option.  There are 4 rear suspension links, 3 front suspension links, a panhard bar, a steering link, and a drive link.  That's 10 to make.  Each uses a pair of plastic ends and plastic pivot balls.  Note that the steering link is behind the axle (BTA) which keeps it out of the way of obstacles.


   

The multi-part drive shafts use plastic bodies, steel universals, and an extruded aluminum sliding spline.  They seem very durable.  Rear drive shaft is shown installed on the right.


   

The shocks use a machined aluminum body, caps, and spring perches as shown.  These are really high quality shocks with a nice soft spring rate.  The picture on the right shows how tight the area is where the shock passes between the various links to connect to the axle.




Here's the completed chassis with a battery test fit and ready to go.  This is always an exciting part of the build as it allows everything to be tested out before the maiden run.  This is the point at which I program my radio for steering end points and other parameters.  Note that I did not install any body posts because I will not be using them.


   

I'm re-using these Proline BF Goodrich All Terrain T/A tires which I had on a LEGO model for years combined with a set of plastic beadlock wheels from my Gmade Komodo.  In both cases, I think these are a perfect match for a chassis destined for a Toyota 4Runner.  The right hand image shows the completed rolling chassis.  This is the state it was in when I went out for the first test runs and pronounced it awesome.

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