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Slash 4x4 LCG Stage 4: Prototype 2 and testing

Slash 4x4 LCG Stage 4: Prototype 2 and testing

When I received the 2nd revised sample, right away I noticed how narrow the chassis was in comparison to the first prototype.  The revised chassis being an inch narrow was noticeably lighter, and actually looks better being slimmer as well.  The wider upper deck because of its contour, actually accentuate the already slimmer lower chassis to look even more narrow. 


 

The Front bulkhead piece looks amazing in terms of the amount of machine work that was involved.  It ranks up there as one of the single most complex pieces our factory have machine for our product lines thus far.  The front bulkhead keys into the front portion of the chassis and it is critical that this have a perfect fit to ensure no separation or breakage of this area during hard landing or crashes.  The bulkhead keyed into the chassis perfectly and once bolt down with a combination of five M4 and M3 size screws, it is rock solid.


As I begin to put this 2nd prototype together, we noticed the improvement in the motor mount/rear gear box spacing.  In the 1st prototype it was too close that it caused a bind on the center spur, on this 2nd prototype the spacing was just right.  The servo mounts were in the right position and moved the servo back where the steering linkage was parallel to the steering bellcrank link.


The refinements continued on the upper deck where we were about 90% there on all the holes and alignments.  One have to keep in mind that on the original Slash 4x4, there was no upper deck to speak off, so to get all the holes for chassis posts, gear box, and motor mount just right would take a few revisions.

With the major issues all resolved from the 1st prototype, we now look into small refinements for the 2nd prototype to make it perfect:

1)      Alignment of upper deck.  Because we gone to more chassis posts, moving it to the other side of the center shaft and the steering posts now sit over the bulkhead, there were a few alignment issues that the upper deck had.  Another prototype cut would be necessary to make sure the upper deck sits snug between the front and rear gear box, and also to make sure the screw holes all line up perfectly

2)      We also cut away a bit more material on the upper deck for clearance of the motor wires and tabs on the end bell

3)      We wanted to shave weight where ever possible, so we change the steering servo mount profile from just being a rectangle to a slimmer more shapely design.  We shave down the center of the battery block (so it looks like a letter “M”) to save weight.  We also shave off the height of the battery bracket to save more weight. 

4)      We shorten the carbon battery strap a bit to save some more weight

5)      On the motor cam, we noticed upon installing the pinion gear that it was difficult to get the pinion gear deep enough into the cam on the motor shaft so it will line up with the spur gear.  We implemented a slot for pinion wrench access to sit the pinion gear inside the came more for better alignment with the center spur.  We will also be implementing this improvement for the Axial EXO Buggy motor mount (STA30800)

6)      We enlarge and lengthen the weight saving counter bore sections under the servo saver area, under the motor end bell area and under the center spur gear area all to save a bit more weight

7)      Include a slightly longer servo link turnbuckle

8)      We discover an oversight in regards to mounting a front sway bar.  So we implemented a design of two brackets that uses a set-screw to hold down the sway bar and the brackets key into the front portion of the upper deck.


Overall, I was very pleased with the 2nd prototype and we hit all the refinements that we put in over the 1st prototype.  We also now have a working prototype that we can hit the track with.

Testing

Maiden run for the truck was at a local indoor clay track.  This track has great traction and a good combination of jumps, rhythm sections, and high and low speed corners.  We were not looking to get out there and set any track records.  I will be perfectly honest here, I don’t have world class driving ability, I’m not a national champion, or any champion for that matter.  However, I hold my own well against locals in the Southern California racing scene, and I think more importantly I have a good feel for even the most subtle changes to the car/truck’s handling.  This I believe is critical to have in product development, as you need to be able to feel out even a 1mm roll center change, or a 10wt oil change, or a weight distribution change.  Some drivers have such great natural ability and reflex that they can “wheel” an ill-setup car and thus sometime make it confusing to make product improvement…because often times, everything works for these guys. 



There were a couple of main things I was looking for with our test session:

1) overall durability
2) Low speed cornering
3) high speed cornering

Durability:

We went out with a truck that was pretty much in stock trim besides our LCG conversion kit.  As difficult as it was to resist hopping up the truck with all the goodies that we make for it, we want to see how the LCG would hold up even if the only hop-up parts a customer put was this LCG kit….and nothing else.  Believe me when I say, it was hard to go out there with an otherwise stock Slash 4x4….down to the plastic shock caps.  After 6 straight battery packs, and a few spectacular “oops!” on the track, I was pleased to see the entire LCG kit held up flawlessly.  The front bulkhead area never had a problem.  The motor mount/motor cam never loss a mesh.  The battery pack stayed in place even after hard tumbles.  I did manage to break an A-arm and strip out two plastic upper shock caps (I knew that was coming...), so I definitely wasn’t just putting it around the track….we were hauling with it. 


Low Speed Cornering:

The low speed cornering was one that I was interested to see how the LCG would improve over the stock Slash 4x4 chassis.  More specifically, it was the type of track setup where you have a low speed turn that quickly followed a set of jumps right before it.  Having raced the Slash 4x4 before, these kind of combo on the track usually gave the higher CG chassis the most difficulty.  As you jump and land from the jump right before a low speed turn, the truck shifts a lot of weight forward, and if you turn too quickly, it will shift the weight to one corner of the truck up front.  This often times will induce a roll over for the higher CG slash 4x4, because of the amount of weight that is “pitching” forward from such high CG, that it easily rolled the truck.  The only way on the stock chassis to prevent this from happening was to slow down considerably after landing from the jump before initiating the turn and blip the throttle a bit to shift the weight back to the rear of the truck a bit before negotiating the turn.  This often caused the truck to a bit wide and just overall slower lap times.  And if there are quite of these jump/turn combo setup on a track layout, then the stock Slash 4x4 would suffer greatly.

With our LCG chassis setup with all the weight lower, this problem has been completely eliminated.  I can backside land a jump, roll off the jump, or even coming over the jump a little bit crossed up, and just quickly turn the steering wheel to negotiate the next turn without the truck ever looking to roll over.  And this was running even without the sway bar.  The truck was sure-footed and very confident negotiating the jump and the immediate turn right after as the picture sequence show:

 

The truck also initiate the turn-in into the corner better as well as a few times I found myself turning in too early because once you tell the truck to turn, it responds crisp and quick.  Over the stock chassis, the LCG Slash 4x4 just makes you feel more in controlled overall.

(Oops....too early!)  

High Speed Cornering:

Without sway bars, I thought it was just going to be a nightmare getting into the high speed sweeper at this high bite track.  The stock chassis Slash 4x4 actually corners high-speed pretty good….to a point!  Once you pass that “point of no return” during a high-speed cornering, the stock chassis Slash 4x4 due to its higher CG would roll over (usually resulting in spectacular tumbles because of the high speeds) and depending on your entry speed into the turn, you never really know for sure where that “point of no return” is.  With the LCG setup, aside from having to slow down a bit more due to a lack of sway bars, the truck felt really good actually going through the high-speed sweeper.  The truck was able the flat-track through it and even with a mild jump in the middle of the sweeper, it never really upset the truck.

I can only imagine with the sway bars on, the truck would be dialed around the fast stuff.  Even a few times when I over cooked the turn, I was able to play with some counter-steering on the steering wheel and get the truck straighten out.  Normally on the stock Slash 4x4 chassis setup, the higher CG prevents the truck to negotiate quick left/right steering input adjustments and that usually will result in a spin-out.  On the LCG setup, the truck never seemed to be upset by steering corrections. 

We considered the first test session a great success considering nothing broke on the LCG components, everything worked as it was designed to do, and the performance of the truck was definitely elevated to a level that makes it competitive with anything currently on the market.  In checking with the lap times from the previous night club racing, our truck was doing competitive lap times right off the bat and that’s even without a proper setup or sway bars on the truck, which leads me to believe the truck still have huge amounts of performance potential to unlock with this LCG setup.  I also tried to pace with some of the fast locals during test runs, and minus the slightly rusty driving skills, the truck was hanging right with them.

I then boxed up the conversion kit and shipped it out to one of our drivers out in PA for further testing.  The 5th and final installment we will share some details about production, time frame, possibly a write up from our driver who is testing the chassis kit, and even an special offer to those that are willing to pre-order a chance to customize their own Slash 4x4 LCG conversion kit.  

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