Oct 25, 2017
It's been a long winter and good weather is finally upon us. This means getting the Jato ready for a faster season. Thank you goes first to Boca Bearings for providing all the bearings for this Jato. The replacement of these bearings has been made more convenient with the ever-precise and super-sharp metric tool kit.
About these ceramic bearings:
This part of the workshop will be the replacement of all 33 bearings with Boca Bearing's Orange Seal Series of bearings.
(Boca Bearing - Traxxas Jato 3.3, model 5507)
A) The Bearings:
The bearings are of ABEC 7 grade (American Bearing Manufacturers Association). This is a measure of eccentricity or roundness. It is measured at 0.0025mm. A regular bearing measures at 0.0075mm. There can only be one higher rating of ABEC 9 at 0.0012mm. This means only the best continuous and precise movement which allows the possibility of pushing your RC to go faster. Remember bearings are not a source for "more" power, but it allows for more power transfer to where it counts! As a simple extreme comparison; think, how fast would you go with square wheels?
B) Grade 5 ceramic balls:
Think: best hardness-roundness-temperature resistance-corrosion resistance
i) They are created in a sintered process using silicon nitride or Si3N4. The material is corrosion resistant. This is very important since my stock bearings in the steering drag link upgrade already began to show corrosion preventing the steering from centering. (Even though cleaning and lubing after each run)
ii) Grade 5 means that they are they are the second from the top grade in sphericity and tolerances. A typical stock bearing is a mid grade or between 50-10.
iii) Non-magnetic. If you've ever free spun your wheels using shop air then you've magnetized your bearings. This can slow things down with opposing and attracting forces in your bearings.
iv) Highest hardness rating. Rated at 70Rc (Rockwell hardness). Ever notice the difference between rolling a tennis ball versus rolling an equivalently weighted steel ball. Which rolls faster and further? A common bearing hardness is 50Rc and stainless is about 58Rc.
v) Highest resistance to heat. This makes it ideal for our nitro engines and clutch bells.
C) Orange seals:
These are Boca's ultimate frictionless (non contact) ball bearing protection against the terrain. They are made of an over molded washer with a flexible material left around the edges. The orange rubber seal is then used to slip into place around the outer race and will not contact the inner race. This creates a seal and prevents drag. It’s also an ideal solution to allow the end user to simply remove the seal without damaging it. This seal has the ultimate air-tight seal for your engine bearings. We don't want uncontrolled air entering the combustion of the nitro engine, since that would make the engine run hot. This seal allows for a very consistent engine tune. If you are constantly adjusting your carb, start with the orange seal. I love to tinker with carb (always a screw driver in the pocket); this eliminates a lot of the unnecessary adjustments. The engine just holds a tune!
D) Races: (which the ceramic balls travel within)
The races are made of Stainless Steel, another good reason to replace your stock bearings. Stock bearings rust, these don't!
The off-road bearings are supplied with NB2 grease
The on-road bearings are shipped with NF2 grease
A higher grease thickness could increase heat and overall spin reduction.
The lighter NF2 grease was picked for this project. The bearings were very carefully cleaned using an ultrasonic cleaner. The NF2 was replaced with Boca's High Speed oil for the ultimate speed and temperature rating.
I must note a couple of special points as I was going through the bearing replacements.
A) Cleaning and lubricating my bearings was only done to ensure Boca's High Speed lube was between the races. I have since purchased a small ultrasonic cleaner from Harbor Freight for around $30. I will be using it to do regular maintenance by cleaning out dirt, road grime, and old lube out between all those tiny components. Remember using oil requires a lot more maintenance since the oil will dissipate sooner, meaning it will require regular maintenance. The factory lithium based greases tend to stick around longer.
B) The wheel spin test is only preliminary since the Boca Bearings where not yet broken in. I hope to see similar if not better testing.
C) Ceramic and stainless steel!! I can't stress this enough. If you want precise steering the way to go is to remove all your plastic bushings, (especially the bearings in the upgraded bell crank). I just recently replaced all four using stock steel bearings. After a year I noticed my standard steel steering would not return center. It only took a little rust to throw those little bearings off and cause drag and a gritty feeling. Just as a note I am very careful to clean, degrease, and lubricate after each run using brake cleaner and Wurth's Rost-off penetrating oil.
D) In my videos I chose to remove my engine bearings using the "heat" method. It doesn't require special tooling. Using a tool was NOT the deterrent. In the industry precision bearing installation is typically done with heat. There is a good reason for this. Since metal on metal contact, especially when it is a precision fit will cause damage to the ultimate fit if done at room temperature. With pullers the bearing is forced to wear down the seat that they are mounted in or the "gap" is damaged. In an engine gap is bad since it causes air leaks and compression lose. The heat method is well documented and has already been performed in a Boca Bearings series by David Mills here:
E) Engine assembly is important and must be done carefully. I can't stress enough that it must be done when you have the time and patience. Otherwise, you will be buying a new engine. It is also important to consider sealing and rebuilding your carburetor when you are doing this process. I bought all the o-ring kits from Traxxas before I started. No air leaks = ultimate stable tuned engine!
OK here's the deal!
I have done some runs using my stock Jato bearings in my previous submission. From the data and "feel" of the machine I have had to back pedal on some of my vehicle settings. The car was too soft and did not handle the fast acceleration properly. Here is what has been done.
A) Anti-Squat moved to 3.75-deg (highest possible setting). It was set to 1.5-deg or the lowest possible setting. This is two blocks up from factory. So the softest setting was good off road. But this setting is good on-road and under acceleration. I found that the car was bottoming out way too easily under power. I need that squat-power to be transferred to the front of the car.
B) I have decided to move away from the softer rear-end springs. I am now running all stock springs.
C) I have moved rear control arms to a more progressive stance. They are now set to mid-upper mount position and inner-lower mount position or B1 setup. This link will show the diagram.
D) I have replaced the transmission grease with penetrating grease from Wurth called HHS-2000 Penetrating High Temperature Lubricant. I have found old the grease was too susceptible to high temps. This HHS grease is very tacky which will stick to the gears during high RPMs. It can be found here:
E) Huge change is coming to assist with high-speed handling. I am hoping for straighter launches, acceleration, and stopping.
For my next submission I am hoping the videos show my new drift box in action. It will be installed inside my wheelie-bar "battery box". You'll probably note that I added two 12" servo extension cables that run into my empty battery box. These cables were installed after assembling the transmission and engine back together.
Update: Just after placing the order for my new D-box, Traxxas announced a new receiver which allows for this adjustment on the transmitters user selectable adjustment knob. Part number TRX6533
Unfortunately Traxxas support confirmed that this new TSM can not be used with my old style (iphone/ipod) transmitter & TQi docking base, part number TRX6507.
Please see the videos below. The two speed transmission videos are particularly fascinating.
A) Front End
B) Rear End
C) Clutch Bell
F) Cleaning and Lubricating bearings
G) Wheel Spin test stock versus Boca Bearings
Note: special thanks goes to Thomas Sahs of Honey Claws for their permission to use Digital Animal as my video theme song.
The above changes are to make for a more consistent speed run. I am hoping that the data is repeatable from run to run so that we can compare and conclude power-to-ground analysis. So far my initial test run (for my next submission) results are in: "it's comin' in hot!" The handling is tight, the power is consistent. I can not even begin to explain the qualitative responsiveness the car is producing. It's a world of difference between tuning, steering, and laying it on the ground. Let's see what the data shows us, next time.