Monday, April 18, 2011

F1 Long-term review: the fixes (part 3)

3) Steering consistency. Few things are more annoying than a wandering center. The Mini-Z F1 chassis has a great servo saver, but it could use some work. If you notice any sticking, give it a good polish and lube on the mating surfaces. The big e-clip at the end can also hang up a little on the inside of the top cover. I like to sand down the edges and the overall diameter to ensure that nothing binds. Finally, if nothing seems to be working, try a new one. Servo savers can wear out or just be bad.

If you've raced F1 for a while, you've broken a plastic tie rod. This isn't the servo saver's fault, as the wheel is actually being ripped past the travel stop. The servo saver does it's job and saves the gears, but the tie rod or knuckle often can't take the load. You've got to use aluminum tie rod and knuckles. I like the 3Racing tie rods since they have a smooth finish. The old Kyosho aluminum knuckles were the best, but they've been discontinued and replaced by the R246 versions with the brake disks. These are essentially the same as the 3Racing aluminum knuckles, so you might want to give those a try. Camber plays a role here and less tends to give you more turn in.

Now if you've ever tried to install an aluminum tie rod, chances are you've broken those little tabs on the chassis. Don't bother replacing them with an aluminum holder, none of them work particularly well. I've spent time filing and sanding, and they all stick. While I've run with the tabs broken, I like stabilizing the tie rod a little more. The trick is to just go ahead and trim the front of the tabs, so you can slip the aluminum tie rod in, but they still support the tie rod from underneath. This keeps the tie rod operating on an even plane, so that the knuckle pins have a good contact surface. Aluminum on aluminum can bind once dirty, so a little lube here keeps the steering nice and smooth.

Another random tip I learned was to "screw" the front springs into the knuckles. The knuckles on the F1 have very tight tolerances for the springs, and I have chased setup for a while with one spring not seated all the way in the knuckle, essentially preloading one corner. Speaking of preload, make sure you've got enough preload on the springs to prevent the front bumper or wing from dragging. I do a lot of work filing the bumper mounting points to bring it up to the wing, but even the wing level can drag at times as the weight transfers forward on entry. If you are getting an initial push, chances are you are dragging something in the front.

F1 Long-term review: the fixes (part 2)

2) Tires, tires, tires. An old adage in racing of all scales is that tires are 90% of your setup. At a big race at an unfamiliar track, we talk about "hitting the tire setup". The challenge is to predict the best tire combo which changes throughout the race weekend. The "best" tire combo is one that provides the most overall grip while offering a balance that suits the motor and your driving style. This balance can be additionally tuned with dual rate, but you don't want to stray too far as steering angle has other repercussions.

You know the track will change, so there's no use in freaking out about overall grip. At the same time you can't afford to compromise practice or qualifying with an unbalanced car. What a lot of newer drivers don't realize is that low traction usually makes a car push, not oversteer (especially on entry). The exception is a motor with a lot of power or an abrupt powerband that can overwhelm the rear tires on exit. I start with as much rear grip as possible and a pretty aggressive front tire. The front tires gradually shift to harder compounds and less steering as the traction and front bite comes up over the weekend. Experiment with different brands, compounds, carpet tires and truing to develop a spectrum of front grip you can use accurately dial in the balance.

At the worlds, I completely screwed over my teammate Matt in the main with a bad call on rear tires. Due to the aforementioned packaging issues, I had been struggling with grip the whole week and took a last chance gamble with trued PN8's over Kyosho 20 rears. The grip was improved on a few trial laps, so I recommended it to the rest of my team. What I hadn't accounted for was the chemical grip fade of the PN8's. Less than halfway through the main, the rear grip disappeared and Matt and I were left with a couple really ill-handling F1's.

Luckily, Eugene and Jacob stuck with consistency of the K20's. Later on, I tried the same trued PN8's back-to-back against worn K20's, and it was like night and day. There was no physical indication of wear on the PN8's, but the grip was gone. The truing probably didn't help. The lesson learned is to understand your tires, how they wear, and when they will let go. The PN8's might just be the hot ticket when new, and I need to study how many runs I can get from them without relying on physical wear indicators.

Additionally, you MUST use R246 tape with these tires. There is just too much squirm in the center that leads to unpredictability. We also superglue the tire with mod motors for even more consistent traction.

Saturday, April 16, 2011

F1 Long-term review: the fixes

1) Packaging. What does packaging have to do with racing? Everything, especially in F1. Packaging engineering is one of the most important and difficult parts in designing an F1 car and this translates to Mini-Z. It's the proverbial conundrum of fitting 10lbs of stuff into a 5lb bag. Whereas the bulk of a full-scale F1 car is limited by aerodynamics, Mini-Z F1 is constrained by scale appearance and rightly so. The rear suspension of an F1 is a challenge, trying to cram as much suspension underneath that gorgeous scale body without anything hitting. Some bodies offer more room than others, and the latest models have enough room for a top spring and disk damper setup with some internal clearancing.

In that quest for an effective low profile rear suspension, I selected the 3Racing disk damper (same as upcoming R246). The problem that I couldn't identify until recently was that the lower disk damper translated to a lower damper arm on the motor mount. Both the Atomic motor mount and the 3Racing motor mount allow you to run the damper arm low enough to hit the rear battery when the suspension compresses under acceleration. The top spring damper mount on the PN motor mount is not adjustable and doesn't hit, but it can't readily accept a disk damper.

There are a few ways to check if you are running your damper arm too low. The easiest way to check is to inspect the area from underneath the battery box while working the suspension. If the damper arm looks like it's intruding into the battery box area, you're too low. Another way to check is to install the batteries, but leave the battery door off. If the rear battery pops out a little when compressing the suspension, then you're too low. With the battery door on, the damper post/top spring will abruptly move up instead of forward when compressing the suspension if the damper arm hits the rear battery, i.e. - you're too low. Finally, if you're noticing weird chunks missing from the center of the battery insulation after a big wreck, you're too low.

The net effect of this is that you will have no rear suspension compliance under acceleration, which is why I couldn't put any power down at the worlds. The deceptive part is that the suspension looks like it's working, aside from the strange upward movement replacing the forward movement when the damper arm hits the battery. This effectively turns the bottom disk damper spring from a disk tensioner to a rear suspension spring, if the suspension can even get past the initial shock of hitting the battery. I fixed the issue by installing 1mm spacers underneath the disk damper plate, raising the whole assembly and the damper arm once the disks/post were centered. 1mm fixed the rear end... I'll pause to let that sink in. A side benefit is that motor wire clearance is improved. Drawback is that you have to clearance the underside of the body for the higher screw heads, top disk and rear top spring damper end.

Speaking of top spring dampers, I currently use the PN side damper for this application because it's a good length, has screw preload, and lots of options for spring rates. I like the PN white spring. You have to aggressively file the sides of the rear damper end and clearance the inside of the body cowl to give enough roll travel, but I think it's worth it. Additionally, don't short yourself on rear ride height with the top spring preload or the axle spacers trying to dump the car. RCP is bumpy, and dragging hard parts will lead to inconsistent handling. I also like to sand down the rear corners of the battery door to points to give more squat clearance during cornering.

So now that we can accelerate, let's look at cornering and roll stiffness. I'm going to go against the grain, and say that the rear end doesn't need to be MR floppy for mod. The F1 is a heavier chassis, and I think that the roll stiffness of a side plate setup is more than compliant enough to handle the power with a couple of tricks. Old school tuning left various side plate screws loose. This WILL NOT WORK with grey chassis, as for some reason the screws do not grip the grey plastic as well as the clear plastic and will back out unless tight. I personally have moved away from this, since the side plates are the only thing that "locates" the motor mount and thus the rear axle and wheels in relation to rest of the chassis. Leaving them loose has led to inconsistent handling as the car struggles to stay "square".

I've got quite a few options in my pit box for dialing in the rear roll stiffness. Side plates include Kyosho carbon, Kyosho carbon thinned down to 60% width, and Mantis carbon in order of decreasing stiffness. In addition, I use the full plastic spacers/blocks that come with the Kyosho carbon side plates for full stiffness, but I have beveled versions of both front and rear blocks that I can use in different combinations to soften up the side plates by increasing the effective plate length (moving up the pivot point with the beveled front block), or relieving the rear tension on the plate with the beveled rear block (so it bends in more of a "C" shape than an "S" shape). If you don't believe these have an effect, you will if you install a beveled block on one side and a full block on the other… Side springs can also be employed, and I've cut the "tubes" out of an old plastic motor mount so that I can screw them onto the Atomic motor mount. The 3Racing and PN motor mounts have the tubes machined in. Using the side springs will also let you use the Kyosho tube dampers.

Other things to look out for with side plates include the dreaded tweak. While the grey chassis has addressed the molded tweak issues of the clear chassis, the Kyosho carbon side plates also have a slight tweak that you need to address. The Kyosho side plates are made identically left and right which means that any bend in the raw material will be in the opposite direction when mounted on opposite sides of the car. Most of the Kyosho carbon side plates I've seen have a slight upward bend when mounted on the left which means a slight downward bend on the right. This means a stiffer right side which leads to the infamous left tweak. A thin shim between the side plate and the motor mount will usually address this without having oddball steering bias in the radio that can have inconsistent side effects. The Kyosho side plates I thinned down don't seem to exhibit this tweak which means that they are just too soft or I wasn't perfectly even with my sanding. The Mantis side plates are made individually left and right, so they aren't tweaked, though the holes can elongate. With an aluminum motor mount, it's also cheap insurance to use a nut in addition to loctite to capture the rear side plate screw.

Friday, January 21, 2011

Reflex Racing Club Series!!!

We are so excited to get the ball rolling. Check out the exclusive page to the series to find out what it is all about. We want to get as many sponsors and participants as we can in order to expand Mini-Z Racing globally. REFLEX RACING CLUB SERIES

Friday, November 12, 2010

Cristian's MR-03 at the Worlds

Brief post, cause it's late... :P This was my car at the Worlds. It was fantastic. It allowed me to finish 3rd Overall in GT Mod amidst some very stiff competition and without having driven a Mini-Z since June. It had prototype parts on it as well as some other parts that I had personally not run on an MR-03. One of them was the Low Profile Suspension. I LIKE IT A LOT! Come to think of it, our results seem even better when we put the conditions into perspective. In every class, we had the Top Finishing MR-03's as well.

My set-up was simple:
-Silver Low Profile Springs
-4 Degrees of Caster
-Low Down Knuckles 0.3 shim underneath/ 0.5 above knuckle (below ball)/ 0.3 shim at the top to give slight Pre-Load
-30000 Wt Kyosho grease on the lower ball (where the spring insets)
-1 Degree Camber
-PN RXF 15 Tires, on 20mm Wheels, trued to 23mm on +2 Wheels

-Reflex Soft MM T Bar
-96mm Position on Motor Mount
-Silver Side Springs on Tri Shock, 15000 wt Grease
-450 CST oil inside Kyosho Oil Shock, 50% Rebound
-Kyosho Yellow Spring, Pre Load set to have chassis level when fully loaded
-PN Racing 6 Degree Slicks, Trued Flat. +3 Rear 20mm Wheel
-Atomic Diffusor Installed

-CTP Tuned 32 Turn PN Spec Motor
-Atomic VP 800 Batteries
-Gear 11/53

Thursday, September 30, 2010


Pictures, 'nuff said!