First of all,
let me start off with my opinion of this extremely popular nitro touring car. Both
versions are extremely well equipped and clearly demonstrate HPI's dedication and
superiority in the field of pavement pushers.
forward, quality parts a plus
You can tell a lot about the quality of design and materials when you get the opportunity
to build one from a kit. Not only did I find this car very straightforward in it's
assembly but required very little modification to make it RTR. It seems that so many kits
these days seem to be chock full of addendums, requiring you to dramatically modify parts
in order to make them work. Now, I'm not against modifications.. they are how some of the
greatest innovations come to be, but when you are trying to build a kit, with it many
complex parts and the painstaking and inevitable task of having to fit third party servos,
radios and engines to the chassis, the last thing you want to have to deal with is
referring to addendum after addendum about how to dremel parts to make them work. I didn't
see this as a problem with these cars.
A picture is worth a thousand words
Now, many of you that may have built these kitss may feel that HPI's method of building
instructions may leave something to be desired. I think I may have counted all of about 20
words in the racer manual. Brief it is. However, the saying that a picture is worth a
thousand words clearly applies to their method. Systematic exploded views of each
"section" concisely illustrates how each part interconnects. Additionally, with
this method, you are not necessarily bound to the exact step-by-step instructions that
normally are part of most manuals. I feel that this also gives you additional
understanding of HOW your car works. Afterall, this is the biggest selling point
behind kits, vs. RTR's; so that you can gain a helpful understanding of how your car is
put together so that you can make your own repairs and modifications.
The driving force
The Nitro RS4 (both standard and Racer) are built on a three belt, all wheel drive design.
Although not as resiliant on gravelly pavement as drive shaft or other protected driveline
systems, it does provide the smoothest and most quiet results. The natural dampening
characteristics of belt-driven systems tend to help reduce premature wear by absorbing the
relentless vibration that accompany nitro systems and increase efficiency of power to the
drive wheels where they are needed.
Hit and Miss
I have to say I'm a little disappointed on their apparent lack of belt tensioners, even in
the Racer kit. Granted, most tensioners are more about improving the asthetics of
the machine rather than providing any real mechanical advantages. In theory, this is just
one more piece of machinery for the engine to drive and decreasing its overall efficiency.
However, there are exceptions to this rule. An improperly adjusted belt can either
increase friction at the bearings (if overtightened) as well as the belt itself. If too
loose, the belt can "slop" around dragging or hitting nearby parts as it makes
its journey from one gear to the next. On the Nitro RS4, the forward belt (the longest
one) tends to aimlessly drag on the top of the chassic plate. Whether this really creates
that much friction is debatable, especially since this drag is dissipated over several
inches. The other solution to this would be to put a tephlon or silicon backed tape on the
top of the chassic, just under the drive belt path. The more important concern with this
particular belt is the sharp pinch it must make as it enters the forward differential
assembly. A loosely stretched belt could, conceivably, not make that pinch either jam the
entire works, or worse, cut the belt in half. I have to admit that this is not something
I've personally experienced, but nonetheless, should be something worth considering in
future designs. As of this writing, HPI does not offer a forward belt tensioner for the
Racer. They do, however, offer a belt tensioner/gear brace for the middle belt that drives
the exterior offset belt assembly. The purpose for this is truly two-fold. It acts as the
only easily adjustable belt tensioner avaiable from HPI. More importantly it acts as
a much needed brace for the two drive shafts extending well beyond a structurally sound
standard. Why HPI doesn't include this as part of this kit, I will never fully understand.
I understand they are trying to keep the price of these kits down, but it seems to me that
this is a mandatory part and tops my list as the number one most important hopup for the
racer. Failure to install this device, puts an incredible strain on the shafts and
bearings that exist, especially when considering that a belt is being driven between the
two shafts, thus pulling the two shaft together at a force equal the the driving force of
to be continued....