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dnano-mini-z · 12 years
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Latest Dnano Ferrari Modena Iteration
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Introduction
The Dnano Ferrari Modena and its Mini-z equivalent the Ferrari 360 GTC are gorgeous bodies.  Early on I was a fan due to their visual appeal and clean light weight design.  However, based on my driving experiences I now have significant reservations about this body.  My personal preference is for a car with better rear grip and with more understeer character.  Fans of Mini-z quickly learn that the different body styles have an ENORMOUS impact on handling.  My tests indicate that most of this effect comes from how the upper portion of the body's weight is distributed.  The Ferrari has a forward biased cab with the windshield located above the front wheels.  This upper weight (more so than the aerodynamic effect) results in roll forces with a bias to the front wheels, and that promotes oversteer.  By contrast Mini-z bodies that give more rear grip, such as the Lexus 430, the Ferrari 599x, and the Honda HSV, have rearward biased windshield/cab structures.
So that is a long discussion about Mini-z bodies for a blog post about my Dnano, but it should help explain the rational for some of the modifications made to my Modena.  I further need to emphasize a difference between these cars.  Heavier Mini-z cars give higher g-force turns on RCP tracks because they dimple the soft rough surface more at the tire/track interface, such that the increased grip exceeds the centrifugal force penalty that dominates in real world cars.  I do not observe this phenomena for Dnano cars running on the Nanotrax EVA foam course.  So with regards to my modified Modena, while the positioning of the lead weight shown does serve to increase understeer character and to improve on-throttle rear grip, I still need to assess its impact on cornering speed.  With all that said lets look at my Modena modifications.
The Body
My Modena body has a number of modifications that are intended to both lower and move the CG back.  The bottom has been sanded down to the point of penetrating the front and rear "brake cooling vents", and the rear body mount has been relocated to lower its ride height on the chassis.  The windshield is a thin light weight polycarbonate vacuum molded off of the original piece.  The front end was lightened as much as possible although crash repairs now have rendered that bit redundant.
Other miscellaneous modifications were made.  To provide wheel clearance the fender wells were enlarged and to prevent damage from boundary impacts flares were built up from multiple layers of medium CA.  The front end corners were filled with CA and contoured to smooth glances off the car's sides.  The wing was mounted on the roof because it better plants the rear end than does the same wing mounted in the back (and I have no race spec rules to worry about :-)).  The holes reamed into the rear were intended to reduce the so called parachute effect, but are likely a mistake for contributing to a more forward CG.  The screw holes in the roof allowed for testing the effect of weight changes to the cab region, and helped shape my opinion stated in the introduction regarding the basis for the dramatic impact of various bodies on handling.
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The Chassis
I have recently changed the front tires from XP FRA 15 series to 20 series rubber.  This has virtually eliminated the tendency of the car to traction roll but still provides plenty of grip in the turns.  These tires are mounted on PN Racing aluminium wheels, which are ultra precise, and X-Power (i.e. light) wheel shafts.  This overall heavier than stock combination gives the car quite a bit of turn in to tune around (see my "Power of the Ring" blog post for details).  Note that these silicone containing tires must either be glued to a metal rim with silicone glue, or a retaining lip must be fabricated to keep them on your wheels.  I really like them adhered with silicone sealant to these sweet rims.  Quick tip: roll a thin layer of silicone sealant on the rim and on the inside of the tire using a Q-tip.  Pre-cure for about 8 minutes then put the tires on the rims, wipe away the excess, and allow them to fully cure overnight.  They will be on there solid but can be pulled off cleanly as needed.
On the rear I am still running double XP FRA 15 series tires on custom made double rims in size 18 (note: size 17 can be used on fresh taller tires, or to minimize traction rolls if 15 series compound is used on the front tires) that are mounted on Kyosho #1 aluminum hubs (note: the Kyosho product mates more accurately than the X-Power equivalent when using the Kyosho adaptor ring).  This is an awesome mod for enhancing the rear grip of your Dnano.  Do not be intimidated about making yourself a set!  I will describe my technique now.  Buy 4 Kyosho plastic size 18 front rims.  Take a pair of small wire cutters and cut the spokes from 2 of the rims.  Just be careful not to warp them by using too much force (i.e. cut, cut, cut, without pulling).  Now sand these down so that when they are glued to the uncut rim they will precisely fit a pair of tires.  Decide whether you want an outer rim lip and choose the appropriate side to trim using something on the order of 280 grit sandpaper.  This needs to be done evenly.  For example, use 10 circular motions, stop and rotate the sandpaper/rim 180 degrees, sand another 10 circular motions, stop and check for size, then repeat this process until the width is exactly right.  The rest is easy but critical to get right.  Carefully tape an uncut and cut rim together around their full circumference to temporarily form a wide rim.  Remove the pinion gear from your Dnano and mount the taped rim onto the axle.  Now rapidly spin it and very closely examine the rim.  With a good pair of eyes or crappy ones like mine with strong reading glasses, the rim must spin perfectly true.  If not retape the two pieces until it is absolutely perfect.  At this point simply place a drop of thin or medium CA onto the inside of the rim at the seam between the 2 pieces then quickly give the rim another spin.  To be safe you can repeat this with another drop or two as needed.  Remove the tape, let it cure a few minutes, and your done.  Awesome wide rims with no wobble for your little baby.
[Note: It is possible to run double XP FA 20 series front tires (15 series compound is not available for FA tires), if your body provides enough room.  Others at Nanotrax prefer this option although my early testing of such a tire suggested it had slightly less grip than the more narrow FRA 15 series tires.  In this case little to no trimming of the rims is necessary]
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The front suspension uses hard Kyosho springs (copper color) and the rear suspension uses a soft Kyosho fiberglass I plate which has been further softened by reducing the neck width to 3.6mm.  So overall this is setup generates more understeer.  I have tuned my custom disc damper to give fast weight transfer to the rear for strong rear traction when throttle is applied, and a level of sudden off throttle turn-in that carves fast yet accurate turns with minimum braking requirements for the given course.  I seem to have a preference for a system that uses slightly progressive damping (i.e. currently a soft silver XP top spring paired with a slightly stiffer bottom spring that was sourced from slot car parts).  To accomplish strong on throttle rear traction I have an unusual arrangement in which the top spring retainer acts as a travel limiter that prevents unloading of the I-plate beyond a certain level (which is very nearly its static position), and the top spring itself then primarily functions to give progressive damping during I-plate compression.  The bottom spring is somewhat softer than an Atomic black spring and is mounted substantially preloaded.  If I am getting too abrupt a turn-in and hitting the inside boundary I need to lighten the bottom spring or its preload, or vice versa if I am overshooting the turn apex.  Currently I am running Mugen 800 silicone oil.  My "Ultimate Disc Damper" setup allows me to add oil only once at start of the day and get smooth consistent damping the rest of the day.  Thusfar I have adjusted viscosity to allow for rapid transitions to the tight combinations of left-right turns on the track.  Higher viscosity oil slows these transitions so the proper viscosity needs to be selected at least partly on that basis.  At some point I need to think about matching the oil and spring rates to give optimal bump adsorption.  I did notice that thicker 1000-1200 oil seems to cause skipping over bump tops and that my setup with 800 oil appears to allow the tires to stay in better contact with the track.
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Having worn out my discontinued XP Extreme motor, I have now installed the 2nd version of this motor (XP-MOT-HS, long shaft, which I cut down) which is presumably sourced from a different manufacturer.  The power produced by this motor is insanely over the top, and to fully use it you would likely need a modified car on a full Mini-z sized course.  Nevertheless, I am happy with this motor when I use my transmitter to turn the throttle H-point way down, and I can adjust it easily to provide whatever level of power I desire.  Using this motor with a Kyosho 6 tooth pinion/31 tooth spur gear train excellent engine braking/weight transfer is achieved with my current setup.  But be forewarned, I have been told that the basic KT-18 transmitter is not adjustable enough to do the same, and the preferred motor with that transmitter has been the Kyosho X-speed (DNW108).  However, one needs to be aware of a quality control issue with this Kyosho motor.  Mine developed a tick-tick noise when slowly rotated, and an associated drop off in power within the first week of use.  Local Dnano expert Khun Dahm has experienced the same problem with these motors.  The likely explanation is that one of the micro brushes starts to catch on the commutator.  So you may need to buy some motors until you get a good one.  Very un-Kyosho-like IMO.  Regarding Dnano motors it is generally frustrating that there is no documentation available on their output and Kv.  I prefer higher Kv low torque motors because they are less prone to power on oversteer coming out of corners but turn on more down the straights where it is needed.  I think both the motors described above are relatively high Kv but I have not seen any numbers.
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I have fashioned fiberglass front suspension plates in size 6 and size 7 (shown here) using Kyosho aluminum plates as a template.  I do not believe these give a performance advantage over the plastic pieces, but they do not need replacement every couple of months, they do not add the weight of the aluminum up front (which is a performance disadvantage IMO), and they are thin enough to give the mounting screws more bite in this area that is so vulnerable to screw hole stripping.  Because I like to make full use of my tires I must pay close attention to the ride height/ground clearance of the chassis.  With new tires up front I can lower the chassis by adding spacers at the kingpin interface with the lower suspension plate, and then remove them as the tires wear down.  With new tires in the rear I can keep the standard arrangement but then add spacers between the rear body mount and the chassis case to increase ground clearance as needed.  Sometimes, for the rear, I may even build up the rim a bit with a few layers of masking tape.  Below is an example of some heavily worn front tires without added lowering spacers.
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Lastly, I will discuss all that lead just to the back of my car's center of gravity.  One can think of the car as kind of a teeter-taughter in which the CG is the fulcrum.  The more I both lighten the front end and add weight towards the rear the more down force gets generated in back to keep the rear wheels from breaking loose under throttle.  Additionally, I have noticed that on the Nanotrax surface I get better turn in as I lighten the front end, presumably because there is less centrifugal force and the track dimpling artifact of Mini-z/RCP tracks is not dominant.  So this seems to be a win win situation.  But perhaps their is a mid corner drawback to this setup.  If the front end can suffer from being heavy it seems like the same should apply to the rear.  Maybe this is a worthy compromise.  While I have not noticed a problem I want to strip this lead out before I leave and see how the car handles. 
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dnano-mini-z · 12 years
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The Power of the Ring
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"The intriguing aspect of this modification is that one is essentially pushing off the inertia of the spinning front wheels to give an increase in steering that is independent of tire/track interface" (excerpt)
Updated 2/8/2012
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I was recently challenged with finding a handling solution for a new driver at the track under highly limited conditions.  His Dnano Enzo was understeering badly but he had just exceeded his budget for buying option parts and needed a quick free fix.  Furthermore, my long term suggestion to replace his front tires with stickier X-Power FRA series tires was rejected because he did not want to modify the look of his car.  These tires are my current favorite because they offer both the most grippy XP FRA 15 compound and many increments for tuning (20, 25, 30, and 35).  But their high silicone content necessitates another modification (outer rim lips or adhering with silicone to aluminum rims) to keep them affixed.  Both those options were off the table for my fellow driver.  So I opted for an extreme version of a mod I have been fascinated with for some time, and glued a ring of lead solder to the inside of his front rims.  Both of us were delighted with the effect.  His car now steered well, retained its stock appearance, and no money was spent.
I previously mentioned this tuning method in my "dnano-care-and-feeding" blogpost:
"This manipulation ... has a big effect on initial turn in, and is best experienced to be appreciated.  The important bit to remember is that the heavier the rotating mass up front the stronger the initial turn in will be.  This relates to the servo motor having to apply more force to turn a heavier spinning wheel (gyroscopic effect) and due to the Dnano’s steering geometry there is an equal and opposite force applied to the front end in the direction of turn"
And some of my first observations of this phenomena were posted in the Nanotrax forum at http://www.dnanoclub.com/viewtopic.php?f=2&t=120 last May when I was focused on using this information to alleviate the oversteer I was experiencing with my Dnano at the time:
"The reason is that the kingpin is located forward of the wheel center, which means that most of the mass of the turning wheel is pushed out in the opposite direction of the turn. Because there is much larger gyroscopic force generated by the spinning heavier wheels they require more force from the servo to turn them in. That force pushing the net of the mass of the wheel out in the opposite direction from the turn results in an equal and opposite force pushing the car in the direction of the turn" 
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The relevant steering geometry imparting this effect can be seen in the nose-to-nose image of my Dnano and Mini-z chassis above.  There are a number of ways to harness this phenomena to tune your car.  The image below shows some readily available options for the Dnano.  In order of lower to higher turn in are the stock plastic rims with lightened XP wheel shafts, substitution of heavier standard wheel shafts, substitution of heavier PN Racing aluminum rims, and finally the effective (if inelegant) addition of lead solder rings which can of course be modulated by using different gauges of wire.
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The intriguing aspect of this modification is that one is essentially pushing off the inertia of the spinning front wheels to give an increase in steering that is independent of tire/track interface  Individuals who are driving vehicles off large jumps most certainly have learned to control their vehicle's aerial orientation with this input in addition to throttle/braking effects on their already spinning wheels.  In the future I am going to experiment with whether I can exploit this effect to reduce my lap times.
Comments: To clarify this wheel weight effect occurs only while the wheels are being turned.  Static mid corner turning power is unaffected.  In my recent tests I prefer aluminum wheels with a lighter gauge solder wire than shown in this blog's images.  Excessive weight slows acceleration too much and the proper amount of weight needs to be considered in that context.  Additionally, I have gone back to stock tie rods and abandoned my lightened ones as they impart a similar effect, giving an equal and opposite force that contributes to turn in, albeit to a much lessor extent.
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dnano-mini-z · 12 years
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Part 2: In Search of The Ultimate Rear Disc Damper System
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UPDATED 2/29/2012
Above is the current iteration of my "Ultimate Rear Disc Damper" in which I am testing a further decrease in the base plate to oil reservoir surface area ratio and other modifications.
The key attributes of this damper system over the conventional DDS are:
1. Stable, smooth grit free damping action on the track.
2. Lighter more responsive damping.
3. More precise returns to "center" after deflections.
3. Reduced lubricant loss.
4. Less maintenance hassle.
The image below is of my previous iteration after a couple hours track time using what I believe is silicone 400 oil (and wiping the top clean).  One cool aspect of the system is the ability to visually monitor the depletion of the damping oil by examining the size of the bubbles that develop in the reservoirs.
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In this case the relatively high loss of oil at the plate base collar is reflected in the bubble pattern.  And perhaps there is increased loss of oil on the right side due to the predominance of right handed turns on the course.  Regardless, the rate of oil loss is low and the system provides a means of quantifying it and reducing its impact (i.e. refill the reservoirs before they empty!).
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While my car was driving its best ever using this damper system, the beautiful Kyosho hardware (above) I had adapted seemed be less than ideal.  The Kyosho system was designed to be compatible with a very thin carbon base plate/disc set.  As I mentioned earlier this is even problematic for the Kyosho system in that the constant banging of the titanium post rod against this brittle carbon disc hole expands that hole and damages the post over time.  The use of these lexan discs eliminates that problem, but the increased thickness results in such a tight space for the springs that my set preloads about 50% just to fit. 
Because I want to have more control over the preload I have hacked the hardware as shown below.  The post mount was trimmed down long ago but less obvious is a slight thinning of this plate to give the lower spring more room.  Additionally the use of standard Kyosho screws improves suspension movement clearance.
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Next are several images of the other damper system hardware.  The alteration that I am most proud of is the new adjustable top spring tensioner.  Dnano aficionados will recognize how this piece was produced :-).  Of note beyond what was already covered are spacers for adjusting the plate bed height and springs from X-Power (silver soft & bronze hard) and Atomic (black medium).   Relative to the Kyosho springs these are longer and appear to enable a more linear rate.  In the end I want to compare them both on the track, but I would not be surprised if Kyosho made a compromise in using very small springs to enable fitting their various body styles without cutting a relief hole.  I am not concerned about the scale look of my Dnano so only on track performance will matter going forward.
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dnano-mini-z · 12 years
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Adjusting Dnano Front End Toe
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The above image shows my current Dnano tie rod.  It represents a microcosm of my love-hate relationship with the Dnano vis-a-vis the Mini-z.  Whereas the Mini-z has every option available for a price from the various aftermarket providers, the niche Dnano is relatively unsupported and you are often left to your own devices to hack or fabricate a solution.  Fortunately, the simplicity of the Dnano design makes it eminently approachable to a reasonably motivated hobbyist.  And the improvisation becomes half the fun. So while there are many optional tie rods available for the Mini-z to adjust your toe-out or toe-in, nothing analogous is offered for Dnano.  On the other hand the Dnano tie rod is a simple piece of flat steel.  So you grab a vice and a pair of pliers and create your own custom tie rod.  From my experience it does not take much of a bend to impact the Dnano's handling.  After some trial and error I have settled on a preference for a bit of toe out, effected by bending a normally recommended tie rod as shown in the photos.  I find that while this slows the turn in a bit (which is easily overcome by other hacks) I get better performance in the middle section of the turn.  This makes sense in that each wheel is better able to follow your intended turning radius if you nail it right.  Others may of course have a different preference for the handling of their Dnano.  If you want to test toe-in do the same bend on a tie rod that is one size larger than standard.
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dnano-mini-z · 12 years
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Part 1: In Search of The Ultimate Rear Disc Damper System
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Since not much remains the ultimate for long in this world, I have changed this blog post title from the "Ultimate Rear Damper Disc System" by adding the "In Search of" caveat.  Still, for Dnano, this is the best system I have used, and I see no reason it can not be developed similarly for the Mini-z.
Updated Below 2/20/2012
First, a bit of history.  Initially, upon seeing the disc damper system, I was very impressed with its simple effective design.  After some real world usage its Achilles heel became apparent.  That smooth damping action felt on the bench was ruined by an accumulation of grit and a loss of lubricant on the track, such that it quickly became a friction based rather than a oil damped based system when it counted.  My initial reaction was to shield it from airborne debris with a Saran wrap barrier, and to delete the lower disc to give better transient response under these conditions.  This worked OK and is what I have used for my Dnano until just recently.
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The problem with this hack was that it was ugly, required fussing with the Saran wrap covering, and using just a single disc resulted in inconsistent damping forces.  My Mini-z employed a similar system but by using low friction teflon tape on the plate base (suggested by Bin at Inside Line Racing) I was able to use two discs without having excessive resistance develop.
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After an exposure to all this I became intrigued with a hack my friend Dahm developed for his Dnano, in which he had fabricated a couple of oversized lexan discs that rode on a relatively small bed surface.  I immediately thought that his system was cool in that it would not collect much dirt, but also thought it was too large a surface area to give the needed transient responses.  Basically, when one deflects your rear axle you want to see it recenter quickly.  This system did not have a good response and Dahm later abandoned it for that reason.  In the mean time I decided to pursue a related but exaggerated high disc surface to low bed surface design in a scaled down size.  In order to enhance oil retention and the lubrication of the lower disc I decided to drill holes into the bed surface.  Shortly thereafter a side benefit of this design was realized.  The holes not only retained lubricating oil but also reduced the surface exposed to friction, and resulted in a smoother and faster action overall.  So this design appears to be a significant improvement over the standard system.
Currently, I am recording my fastest laps with this damper system, as shown in the beginning image, using #600 silicone oil.  Since such thick oil has the advantage of dissipating more slowly this is a good indication that the design is close to being optimized for the Kyosho FG Soft I-Plate.  My testing also shows that the system remains grit free over an entire day and the clear lexan discs allow one to easily gauge when the oil reservoirs empty and need replenishing with more oil.  I am excited about this damper and think it is a winner.
If anyone is interested in obtaining a limited release of the final refined version of this disc damper system I am considering doing a run this coming summer.  Please drop me a line in the comments section above with your email address and if there is sufficient interest I will contact you with the details later. 
Update 2/20/2012: This damper system continues to perform beautifully.  I have expanded the size of the holes even further and am exploring whether it can be adapted to use thicker oils while retaining fast responses.  One huge benefit I have recently noticed!  I used to ritually find myself retrimming the steering on my Dnano at the start of each new driving session.  With this new damper it runs straight and true every time once it is set.  So that problem was clearly caused by the rear end not recentering completely with the stock damper setup. 
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dnano-mini-z · 12 years
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Kyosho Dnano Fiberglass I-Plates, a subtle rear suspension advance
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The more familiar I become with the Dnano product range the more impressed I have also become with the fit and attention to detail of Kyosho's option parts.  Take their front suspension springs for example.  X-Power springs work well on the track, they even provide an extra in case you lose one of the tiny pieces, and they are priced well.  But now I favor Kyosho springs having extensively used both.  What is the difference?  For the extra money you get springs that are clearly colored coded and don't strain your eyes to resolve the soft, medium, and hard variants.  Even more cool is the fact that these springs are so precisely made for the application that they hold themselves into the recesses on the mating knuckle to make your front end maintenance more trouble free (tip: install the springs with the small end face up).
Until now I have normally run PN Racing carbon I-plates.  These plates perform with a nice range of stiffness but they have an annoying issue.  It is critical that these plates are installed securely otherwise they move on their guideposts and develop enlarged holes.  This fit requires the use of one large washer and one small washer for each of the 4 screws.  This installation PITA is made worse by the fact it is located next to the motor magnet.  So bearing in mind Kyosho's exquisite attention to detail, what have they done with their recent release of FG I-plates?
Well I am happy to report that Kyosho does indeed have a better idea.  Each individually packaged and sold I-plate includes 4 special oversized washers.  The included installation instructions have these washers going on the guide posts first, followed by the I-plate and the screws as shown above.  This setup largely eliminates the hassle presented with the PN plates.  The combination of the slightly thicker plate, the larger washer, and the novel assembly orientation secures the Kyosho system well and is dramatically less fiddly. 
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An additional design feature of the Kyosho FG plates is the tapered cut which in theory provides for better centered suspension movements.  The plates are available in soft, medium, and hard versions but are significantly stiffer than their PN counterparts.  The "soft" version I am currently using seems slightly stiffer than the PN "medium" plate, and the medium version (shown in the image) is in fact stiffer than the PN "hard" plate and probably better reserved for high speed tracks.  My only knock on these plates is the lack of gradations available in the soft range.  I will likely trim down a couple to make an expanded set.  It may also be possible to adapt the Kyosho washers and assembly system to the PN or Atomic plates.  But one needs to be cautious here as Kyosho has surely tailored the system specifically for their own plates.
Tip: to make your I plate even more secure scratch up the washers slightly by running them across some 120 grit sandpaper a few times on each side.
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dnano-mini-z · 12 years
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Optimizing your Dnano Differential
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My current favorite Dnano differential is composed of the Kyosho pressure plates, ball bearings, and titanium shaft in combination with X-power ceramic diff balls, and elongated spring.  The elongated spring reduces the parts count and allows the differential tension to be reproducibly and precisely set with a single spacer.  A small set of different spacers, which you must custom make, will allow one to tailor differential slip for different track conditions.  As a general guide I am now using a 1.17mm spacer on a very twisty track and found it give better times than a 0.9mm spacer which has too much slip.  In my case it should be useful to have a set of 0.05mm increment spacers ranging in thickness from about 0.95-1.25mm.  Because 0.1mm changes have a large impact it is probable that each diff may vary in its spacer requirements.  I should also point out that the level of slip I am using is similar to that used in my Mini-z differential.  If I lock the wheels and apply power I want to see just a bit of slipping.  Use trial and error around that point to determine an optimal personal setting for yourself.
The other option is the X-Power Easy Adjust Differential.  I disfavor this differential primarily because it is heavier, has less strength, and lacks a fixed reference point.  Every time you clean your rear end bearings you must reset the differential tension by trial and error.  And unlike the Mini-z, you must pull the differential out of the body to perform this adjustment.  All that said, I have not personally tested this differential and others may reasonably want to go this route should they want to frequently alter their diff tension in a relatively quick fashion. 
Another reason to disassemble the differential is to alter your cars gearing by changing the spur gear.  Whichever spur one chooses, be it a  Kyosho (31,32,34T) or an X-Power (29,30,31,32,33,34T), one must match to the same brand of pinion as each uses a different mesh.  Both work well but bear in mind that the Kyosho spur gear is of a smaller diameter for a given tooth count if you ever get into ground clearance issues (e.g. Kyosho 31T is actually slightly smaller in diameter than an X-Power 30T).
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Disassembly of the Kyosho Ball Diff with the above tools is initially fiddly but after one grows accustomed to the operation it is a trivial.  Removal of the lock clip is particularly easy, and one really only needs to keep track of the released clip (and have spares in case you to lose it). For reinstallation the key learned bit is to apply the proper amount of pressure to compress the spring and line up the receiving slot for the clip.  Look for the clip to start to slip under the lip of the groove and then fully push the clip into its slot.
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Here are the individual parts.  Unless you are replacing the "thrust" bearing do not remove the e-clip as shown for the bottom 3 parts.  Just clean that sub-assembly along with the bearings in your parts cleaner.
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Generally I disassemble the differential to clean the bearings and re-oil the diff balls once every week.  Basically if you notice much better cornering after the re-oiling then you are not doing it often enough!  In my opinion many people apply too much oil to the differential.  Kyosho actually recommends oiling both the diff balls and each diff plate.  But oiling just the diff balls better controls adding the minimum necessary amount of oil in just the right spots.  The excess oil just spins off anyway and until that process finishes your differential will not behave consistently.  To oil your diff balls add a small dab of a thin silicone oil to your palm and rub the balls in it to apply a reasonable coating.  Simply place these balls back into the otherwise dry spur gear and reassemble your differential to finish.  For this process I use Losi 1000 oil, and find the recommended Kyosho Diff Ball Grease much too thick for the Dnano cars.  The lighter oil will naturally spin off to leave a certain fixed level of oil, while heavier oil will vary and be dependent on how much you apply each time.
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A couple of additional points on more long term maintenance.  After your diff plates develop a significant grove you can carefully sand them on a flat glass surface with 1000 grit sandpaper to a point where the groove just disappears.  Use a circular motion and alternate rotating it 180 degrees to assure you are removing material evenly.  Do this perhaps once a year.  Next, an important bearing to keep an eye on is the apparently genuine thrust bearing which takes all the lateral tension generated by the diff spring.  Keep checking this bearing and replace it if it is not silky smooth.  For replacement note that this bearing is directional and the cup part of the bearing must face the outside of the car (open side with visible balls faces inward).
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Lastly, I want to comment on an issue with the X-Power aluminum hubs.  If using the X-Power hubs with the Kyosho Differential you will likely find that the left side hub is too tight a fit over the guide posts of the mating Kyosho housing set piece.  This has caused a problem for me as the hub tends to shave off a bit of plastic such that the hub does not seat evenly with this piece and results in your wheel having a small wobble.  If you look carefully to the outside of the guide posts in the above photo you can see a deposit of the shaved off plastic that cause this effect.  To fix this take a razor blade or other appropriate tool and chamfer the opening of each hole BEFORE assembly.  If you want a perfect fit out of the box, buy the Kyosho aluminum hubs.
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dnano-mini-z · 12 years
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Dnano Care and Feeding ..... and some tuning points
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I always have to bite my tongue and snicker inside whenever I hear a salesman tell a newbie to the hobby that "pretty much all you need to buy after you put your car together are replacement tires".  Well, in that perfect world which does not exist, with a mentor presiding over every step, that may be possible.  In reality most everyone will run across a substantial number of costly mistakes that constitute learning the hard way.  This blog will endeavor to describe some of the most common gotcha errors as well as some basic maintenance advise.
Tools
Those above are the one's I use the most (beyond Kyosho's standard provided differential tools).  The Kyosho screwdriver (the X-Power version is excellent as well) and high quality forceps, or their equivalent, are essential.  I would highly recommend biting the bullet and getting these tools.  Left out of the picture is a pair of high power reading glasses as working on the Dnano can make you feel like a watch technician.  The other tools are useful for mods and tweaking.  The sand paper covered battery or dowel is great for enlarging body wheel wells for clearance and the CA glue can be used to make various repairs and even to create body wheel flares.  O.K., lets go over the various bits to keep your Dnano in top shape without flattening your wallet.
High Performance Motors
Anyone interested in a fast Dnano will want to remove the anemic stock motor and replace it with a high performance motor.  Done properly this new motor install can last for nearly a year of heavy use.  Done improperly it may only last a couple of days.  There is one incredibly fine detail to pay attention to and there is one easy insurance policy I recommend that will prevent any problems.
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The upper photo is an extreme enlargement of the concentric housing that holds the motor.  Visible on the left side are 2 slots for the motor wires.  Below these you can just make out a small bump that is intended to fit in one of the crimps on the end of the motor (lower photo).  Unfortunately, this near invisible projection is easy to damage and/or misalign when inserting the motor, and if that happens the motor will twist within the housing and shear its delicate motor wires.  Be very careful not to stress these wires during the install as they are easy to irreversibly damage.  The insurance policy I suggest is to put a dab of silicone adhesive at this end cap and around the wire slots.  Do not overdue it and rub away any extraneous silicone on the surface of the motor/housing before inserting this assembly into the motor mount.  Let the silicone set overnight before driving.  This prevents the more powerful motors from twisting within the housing and provides extra protection for the wires.  While you have the silicone available it is a good idea to rub a bit on the wires where they exit their plugs.
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Broken Tie Rod Sliders and Servo Gears
Simply said, if you are breaking lots of these your front track is too wide for the body.  For some reason the general observation is that if your front end is far too wide you tend to break servo gears, while if it is slightly wide the tie rod slider goes first.  My guess is that this may be due to whether the front or the rear of the wheel impacts the track boundary.  To test whether your car may have such a problem stand it up on its side and move the steering wheel all the way left and right.  If the car moves it indicates the wheel is projecting outside of its housing and is subject to damage.  You can either reduce the track or make a wheel fairing.  For the later, I have recently taken to applying multiple layers of medium CA glue as a quick and easy solution.  One point of caution.  If you do break a servo gear it is best to get help with the replacement as one can easily damage the chassis main board if you do not know what your doing.  Perhaps I will cover this in a later blog post.
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Suspension Plates
I am a big fan of the standard plastic Kyosho suspension plates.  The large plastic on metal bushing should be smoother, and the plate is much lighter than the optional aluminum plates.  The only problem is that it flexes, fatigues, and then cracks over time.  As a fix I have added a thin layer of reinforcing material on top of it to make it a bit stiffer and durable.  The very thin 0.1-0.25mm carbon I am using works great but may be tough to locate, but one should be able to make a similar support with more commonly available fiberglass.  As an additional feature you can fine tune the front end by varying the length/stiffness of the support plate.
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Stripped Screw Holes
This is quite a problem.  Recently Kyosho, after considerable urging by Q'on of Nanotrax, released a chassis plastics set that can be used to replace stripped out screw holes.  That is an improvement but still a big expense and hassle.  Obviously it is better to avoid stripping these out in the first place.  First, get used to not cranking these screws down too hard.  If you use the Kyosho screwdriver use the small diameter end to reduce the applied torque.  Second, be very cautious in the regions that are most vulnerable to stripping.  These are areas that are subject to a lot of force, and which use spacers that reduce the length of the screw bite.  Typically, these are the screws that secure the upper and lower suspension plates (the former being the worst offender by far), and those that secure the I-plate (which tend to break the guideposts off as shown below).  This nearly always happens when spacers are used and it would be wonderful to have screws that are identical to the stock screws but longer for use under this condition.
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There is a simple technique to repair stripped holes that I have used with success and recommend before chassis replacement.  For the example of a stripped upper suspension plate hole first remove the plate and any spacer.  Next take a new screw and wax and polish it with regular car wax.  Then mix up some good quality finishing epoxy.  Not the 5 minute stuff but the hard epoxy that takes hours to harden.  And please get a watch out and mix the epoxy vigorously for an entire 3 minutes to prevent a FAIL.  Apply the epoxy into the stripped hole and onto the waxed screw.  Put the screw in the hole as snugly as possible, wipe away all the excess glue and wait at least overnight for it to set up well.  Remove the screw, trim any excess glue with a razor blade and your fix is completed.  This has worked fairly well for me but the hardened epoxy does sometimes come out with the screw after repeated usage and requires another application.  Perhaps scoring the hole or continuing to use a waxed screw would eliminate that problem.
Bearings
Bearing maintenance is vital and generally under-appreciated.  The photo shows the "thrust" bearing, the two axle bearings, and two of the wheel bearings from left to right.  Cleaning the front bearings and rear bearings with parts cleaner every week and 2 weeks, respectively, works out about right for me.  Do not forget to clean the less accessible "thrust" bearing (hint: don't remove it but just place the entire hub plus axle assembly in the parts cleaner wash).  Never add any oil or grease as it only serves as a dirt magnet.   Additionally, I recommend getting in the habit of spinning your front wheels before every run to verify that both sides spin freely to the same degree.  It is easy to pick up a hair or some dirt and if one wheel slows down the car will pull to that side.  I will discuss preparing the differential in a later post, but it should be cleaned and oiled each time you clean your rear bearing set.
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Wheels (Rims) and Tires
There are a variety of wheel options available for Dnano.  I have been using the Kyosho plastic ones which appear to be relatively strong.  In the rear these rims provide a lightweight solution that reduces rotating weight and will help improve both acceleration and deceleration responses.  Inevitably drivers racing Dnanos will need to replace these wheels which become warped from crash impacts.  To minimize this problem I recommend adding a washer to the wheel nut to better support the weak spot there (if using X-Power hubs you will need a longer screw than that provided or this tweak can damage the hub by pulling out the guidepost).  After the first hit or two in which you notice a warp in the wheel you can physically bend it back straight.  However, do not do this while it is mounted on the car as it risks damaging your bearings.  I keep a spare axle and hub around just for this operation.
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For the front I also use the same Kyosho plastic wheels.  However, one might consider an aluminum wheel up here as a tuning option.  X-Power actually makes a lightened wheel mount backplate ("wheel shaft") with 4 versus 2 slots that reduces the rotating mass of the front end.  This manipulation actually has a big effect on initial turn in, and is best experienced to be appreciated.  The important bit to remember is that the heavier the rotating mass up front the stronger the initial turn in will be.  This relates to the servo motor having to apply more force to turn a heavier spinning wheel (gyroscopic effect) and due to the Dnano's steering geometry there is an equal and opposite force applied to the front end in the direction of turn.  So when you change the spinning weight with different wheel combinations part of the handling effect is due to this property.
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Lastly, there are a lot of good tires available from Kyosho, Atomic, and X-Power.  The later two brands contain silicone which may or may not be an advantage depending on the surface.  Generally, you will want to run one of the stickiest tires on the rear and then pick front tires based on handling tests.  I have omitted recommending PN Racing tires here as I dislike them for both Dnano and Mini-Z.  On standard rear rims the PN tires are probably the stickiest available, for the first day of use.  However, in my experience they degrade so quickly that other tires outperform them after just a small amount of usage.  On a good smooth Dnano track tires can last a whole month so having tires that give out so quickly is unreasonable.  Perhaps they can be an option for an important race day.
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dnano-mini-z · 12 years
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My Race Prepared Dnano, the Other Modifications
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Tuning a Dnano, or any car for that matter, can provide a rewarding hobby.  Given the huge number of interdependent variables, track conditions, and different driving styles, everyone is assured of arriving at their own unique solution for their fastest build.
For the particular Ferrari Modena Dnano described here I settled on a philosophy of concentrating the vehicle weight towards its center of gravity (CG).  This in theory should make for a more nimble car with strong throttle on/off weight transfer characteristics.  In the future I would like to develop a car with a large polar moment to test what the opposite approach would yield.
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This philosophy can be observed in the first few photographs.  Unnecessary plastic has been trimmed away.  Original Kyosho plastic parts are used up front instead of the heavy aluminum optional parts that are available.  The carbon visible up front is only very thin sheet (derived from spent reed valves, thanks Dahm) and provides reinforcement which both stiffens and extends the life of the original plastic pieces.  The steel tie rod has been heavily trimmed, the body has been judiciously thinned, and the stock windows have been swapped out for a light weight lexan version.  The saved weight has been moved to the bottom of the car in the form of lead tape (available at golf shops) centered about 4mm behind the vehicles CG.  The all up weight (AUW) of the model is about 43 grams.
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Visitors are likely wondering what's up with the blue tape on the bottom of the chassis.  That has been added to protect the delicate RFID lap counter chip/connection that is integrated into the Dnano design.  This car is vulnerable to damage here because it has been lowered in the rear by adding a spacer between the motor mount and the rear suspension I-plate, and raised in the front by putting the 1mm spacer under the bottom front suspension plate.  This gives a "chopper" like profile and gives the car a more stable feel.  My tests suggest this effect is due to the alteration in vertical weight distribution and not the attendant change in castor.
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As previously posted the rear wheels are composed of a twinned pair of X-Power FRA 15 series tires on custom prepared widened rims.  I have personally found the setup on the rear to provide the best possible grip for a dual tire rim (more than dual Kyosho 10 tires on the Nanotrax layout) and I keep that setup fixed.
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The front wheels are individual X-Power FRA 30 series tires on standard Kyosho size 17 rims.  So depending on the balance of the car it is easy to choose more or less sticky front tires to accommodate conditions.  The X-Power front tires are silicon based and can be a real PITA to keep on the rims, even with tape.  That problem can be eliminated by fabricating an outer rim lip.  In my case a thin sheet of lexan packaging plastic was glued with CA to the rim and then appropriately shaped.
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For the rear suspension my current best lap time was achieved with a PN Racing medium carbon I-plate (the hard plate is shown in the photo above).  As a matter of personal preference I do not like any of the existing damper plate systems as a total solution.  My current setup uses the beautiful kyosho titanium/aluminum damper hardware but throws in my own custom carbon plate, mylar damper disk, and spring.  If you go with the Kyosho system you will be able to fit most all of the available bodies without drilling a hole in them for clearance.  The primary flaw in the Kyosho system is that the damper disk, being made of carbon, quickly develops an enlarged hole in banging against its titanium post.  No replacements are available.  But this is no big deal!  You can improve the system by making your own custom disk out of a better material such as lexan or mylar.
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Lastly, lets talk motors.  I have been running the X-Power Extreme version 1 motor for the last year.  It is very fast, and in fact most of the best drivers think it is too fast and instead select something like the X-Power Torque motor.  Currently I do turn down the H-Point on my transmitter to manage the power.  I suspect that given the increased grip obtainable with the new rear wheel modification that the Extreme motor will gain favor.
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The other important part of the power equation is the battery.  Fortunately, the most powerful, lightest, and highest capacity solution is also the cheapest.  Naked cells such as the "Zippy" purchased from HobbyKing can be easily adapted to fit the Dnano compartment.  Obviously, extreme care and caution needs to be exercised with such naked cells so please do not go this route unless you are confident you can deal with it.  I should also add that if one opts for the X-Power Extreme motor it is necessary to use a low resistance high discharge rate battery such as the Zippy, or the Atomic Lithium Ion.  These batteries are able to keep up with this motor's appetite for electricity and prevent control glitching that can otherwise occur.
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dnano-mini-z · 12 years
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My Race Prepared Dnano, and the Key Modification
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On January 22nd, 2012, after nearly a couple years of tuning and driving Kyosho RC cars I miraculously managed to record the best lap time at the Nanotrax facility.  This record time lasted perhaps all of about a week's time, and most assuredly had nothing to do with my driving skills, but it was a direct reflection of an effectively modified car.  The following will detail how that car was set up.
The key modification needs to be credited to a local Thai driver here named Dahm, who is an extraordinarily industrious individual that prepares and tunes real go-karts professionally.  Dahm initially incorporated adding up to several front tires to a extra wide rear rim derived from size 19 super wide foam wheels.  This car was fast but suffered from a tendency to flip.  From there we collaborated and developed lower profile wheels that accommodated this more aggressive rubber.  The following shows the custom size 18 wide rims fitted on my Dnano rear end.  These are very simply made by trimming an outer rim to size, taping its circumference flush to normal rear rim, and supergluing the assembly together from the inside.  I ran these wheels each with a pair of sticky XP FRA 15 series compound tires, and it effectively remedies the lack of rear grip from which the Dnano series suffers. 
One can also create wide rims by gluing the extension onto the inside of the rim.  However, while this allows for an easy fit within the wheel wells on an existing setup, it would lack proper tire constraining rim lips.  If one goes this route it would be worth adding at least an inner rim lip.  See how those can be added in my next blog post.
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dnano-mini-z · 12 years
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Why I Love Dnano
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The Dnano is jewelry for men.  It is alluring in the same way as a fine mechanical Swiss watch.  And it is incredibly functional.  That adversary of speed, gravity, is reduced by the cube root of the scale, so it can produce a substantial excitement factor relative to its older Mini-Z sibling.  True, it is a bit of a sensitive wild animal, but when properly tamed it is extraordinarily fast and rewarding.  A proper track for Dnano is table high and brings the action in closer to enjoy.
Additionally, the Dnano tunes more like a real world car.  The Nanotrax track surface is a commonly available smooth foam that is quite stiff relative to the weight of the Dnano.  Just like real cars it runs on a smooth hard surface.  Mini-Z tracks have instead been standardized to run on the relatively soft and very rough surface side of the RCP purpose made track.  Unfortunately this imparts unnatural handling effects on parameters such as weight distribution.  If you are running a Mini-Z forget everything you know about tuning real cars.  It is not the same.  For example, in Mini-Z, contrary to Dnano or real world cars, adding weight up front increases front grip rather than understeer.  Why?  Word has it that that the Mini-Z actually dimples its soft track and creates more friction with more weight.
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dnano-mini-z · 12 years
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Kyosho Enthusiast: Dnano & Mini-z Road Cars
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I love driving and tuning both these Kyosho radio-controlled cars.  There has been considerable discussion regarding which is more expensive to run.  But do yourself a favor and forget thinking about this as a factor determining which to choose.  They are both roughly the same expense, and they are both rewarding and unique in their own way.
Determine which tracks are available in your area and select the appropriate car.  For most this will mean the Mini-Z.  I am fortunate to live half the year in the Bay Area of California, and the other half in Thailand, which enables me to drive both the Mini-Z (InsideLineRacing.com and FastPaceRacing.com) as well as the Dnano (Nanotrax.com).
Since I am currently in Thailand the blog that follows will concentrate most immediately on Dnano. 
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