Traxxas TQi Telemetry Radio and App: Part 1 -- Project overview

Project overview, goals, methodology, process/tool (April 2015)

I have been given a generous opportunity by Boca Bearings to replace all my bearings in my Traxxas Jato 3.3 nitro Truggy. From the moment this car was purchased the intent was simple, go fast, and go very fast. It is a 3.3cc nitro methane engine using a "somewhat" stock RTR. The reason for Traxxas was the readiness of available parts and the most importantly their TQi (Top Qualifier intelligent) 2.4 GHz 4-Channel radio system. There is a little known fact that this data can be exported from the "Traxxas Link" app. It is this amazing feature which makes this workshop possible.

A little background.

As mentioned, I have a background as a technician mainly electrical but also mechanical / pneumatics. My work experience has led me to data acquisition using VBA (another hobby of mine). Since electrical is my day-to-day I like my extracurricular to be non-electrical. I make no bones about it and realize that brushless 3 phase motors can out perform my 3.3cc in a heart beat (but my fun only stops when I run out of fuel;). I've always loved the tuning, and physics behind internal combustion. This RC hobby lets me combine the things I love the most, remote control, engines, and data! I am new to this hobby as of 2012. I experienced a health scare that put me in a wheel chair. My brother, Richard, gave me a chance to start my recovery process ... I needed to stand up slowly for longer periods of time. He gave me a reason to; at my work bench. He wanted his old nitro truggy running again. We got that thing ripping up a storm, and so it began! Thanks Ricky!

This is my gear.

Traxxas Jato 3.3 1/10 2WD Stadium Truck

1. Transmitter (for telemetry with an iPhone dock)

a) TQi 4 channel radio #6507
b) A new transmitter #6507X is available with Bluetooth for Android & iOS

2. iPhone 4
3. Receiver
4. Telemetry hardware

There is a better way.
a) iOS version of the Traxxas Link app
b) Captures all the data
c) View data "real-time" on a customizable dashboard
d) Media can be saved and exported
e) Data limits can be set to set off an audible alarm and vibrate
-for example my temp limit is 300 degrees and battery is set to 5.5v

a) Receiver 5chan #6518
b) Steering servo is a Losi steel gear #LOSB0812
     -"extra high torque" digital servo
     -so it can survive a 60mph crash, right? …
c) Carburetor and brake servo is stock

Great article on this

a) GPS module #6551
b) rpm sensor #6522
c) Flywheel with magnet for rpm sensor #6542 (replaces flywheel)
d) Temp/Volt sensor #6521(for engine head and receiver battery)
e) Expander module to house the GPS #6550
    -permits further expansion of 6 additional temp sensors
f) Mount for expander module #6555 (replaces the receiver box lid)
g) Mount for rpm sensor #6536 (replaces the rear engine bracket)

5. Wheels

These wheels will be balances periodically after speed runs. This makes for a predictable truggy down the line.

a) Front Pro-Line 2.8" Dirt Hawgs #1175 (on factory mounted rims)
b) Rear Pro-Line 2.8" Road Rage #1172 (on factory mounted rims)

6. Suspension / Steering: (this is where my OCD kicks in)

I want a truggy that tracks straight every time all the time. At higher speeds, this is where the money goes to prevent you from spending later. The suspension, I've learned, keeps the spending on repairs to a minimum.

a) Aluminum GTR hard-anodized shock set #5460X
b) Traxxas 30wt silicone for shock damping
c) Shock damper hole diameter rear is 1.3mm and front is 1.4mm
d) Front shock spring rate 1.1 (green) stock setting
e) Rear shock spring rate 1.2 (silver) changed from 1.4 (pink) stock
    -thinking about changing back since the pink did not squat as badly
f) Aluminum steering blocks #5536R
g) Aluminum caster blocks at 25 degrees for steering at high speeds #5536X
    -plastic stock blocks are 30 degrees for on power steering
h) Aluminum hub carriers #5555X
i) Aluminum drag link #5542X
j) Integy aluminum bell crank #7923
   -aluminum bell cranks are important so the bearings have a solid base
   -the stock does not come with bearings, simply nylon bushings.
k) RPM suspension arms front #80722, rear #80752
l) Suspension arm torsion bars have been removed
   -RPM arms don’t have the mounts and they don’t really affect much
m) Rear suspension arm spacers are setup to create a long wheel base
n) Suspension arms and shock connection set to progressive
    -Using mount holes set closest to the center of the truggy
    -This is so there is more body rolls
    -At high speeds the car is not meant for cornering, it needs to roll to on those corrections.
o) Ride height is just below the frame after rebound
    -Thinking about lower this a little to avert some “parachuting” lately.
p) Anti-Squat changed to 1.5 degrees block #5559
    -Stock was set to 2.25 degrees
    -I want the car to be able to handle the bumps in the road
q) Front axles fit and finish: The pivot rod of the steering blocks was a little sloppy. This unwanted steering movement was taken up by using some LocTite retainer fluid (green). The steering now has zero backlash!

7. Drive train
a) Low-mass constant-velocity rear driveshaft set #5551X
b) Differential replaced with 10,000 wt silicone fluid
c) Integy aluminum transmission housing #T8002
d) Self-modified dual disc braking system
e) Clutch bell gear by Robinson Racing - Revo 20t extra hard - #8020
f) Spur gear - Revo 40t - #3955
   -the 2.0 gear ratio keeps the power on the road
   -reduces the wheelies
   -we now need a longer run way to see what second gear can do!
g) First gear is locked down until about 25,000 rpm.
h) Slipper clutch set to 0.5 turns.
i) Carbon clutch shoes by MIP #1620

8. Engine
a) 30% nitro, 11% lube, by Byron Racing Fuels, Race 3000 Gen2 # 3130186
b) Medium Traxxas glow plug
c) Carburetor settings
    Low Speed needle: 1-7/8 turns open
    High Speed needle: 3-7/8 turns open
d) Tuned dual chamber pipe for high rpm performance #X5485
    -provides an average 10% increase across the range
    -11% increase in peak power arriving at the top end of the rpm scale

All these parts with thanks to my local hobby shop. Thanks to Hobby Hobby for all the local support.

What does all this mean?

It's been a couple of years of experimenting with what works for my setup. These changes have had real effect on handling, speed, and repeatable performance. I believe it is the best setup and most reliable before I begin my next big upgrade.

It's all about the data!

The integral tool of this blog will be GPS and rpm data acquisitions presented in the form of a line graph over time. This is how I will present the data using Boca Bearings.

The Traxxas Link app is connected to the radio via blue tooth (new iOS/Android version) or in my case using the old version of an Apple 30 pin connector to my iPhone 4. It has the ability to collect telemetry data every 11ms or sensor values every 0.11 seconds. The apps dashboard can then be placed into record mode to record the media. It can be saved and played back.

The telemetric system of sensors which Traxxas has created is pretty fascinating. I currently have the following setup. The battery sensor keeps an eye on receiver voltage. A temperature sensor is wrapped precisely around the top of the cylinder to measure engine temps for tuning purposes. An rpm sensor measures the rotation of the flywheel. I have also installed the telemetry expansion board to allow for a GPS. Future upgrades will include measurements of heat transfer to the pipe inlet (under silicone seal) and gas tank (customized tee fitting with potted sensor between pipe and tank). My GPS telemetry sensor is my most important piece of data which makes this blog possible. It sends real-time actual speeds from my Jato to my transmitter every 11ms. It is the most unique application of RC telemetry on the market.

I discovered a little known feature in the Link app which emails the data points. If I rename the run the app seems to prevent emails, so I can plug it into iTunes and copy if directly from the app. The file is a *.csv file format or comma separated file which can be viewed in MS Excel. This kicked my interest of programming into high-gear!. I have a background in industrial data acquisitions. My main interest is VBA and data integration. I was able to manipulate the data in a way that allows me to quickly analyze and present speed-run data in the form of a list and line graph charts on-demand.

When the Telemetry-VBA idea was first developed the most important element I wanted to create was the ability to analyze the data with a custom calculation data column. This would be used to calculate differences and percentages between rpm and gps values or between temperature values. In our analysis it will be theoretical speed based on engine rpm and gear ratios. This calculation will account for clutch engagement at around 15,000 rpm and second gear shift point at around 25,000 rpm. It will give us a good idea at how good the engine transfers it's rpm to the ground when compared to the actual GPS speed. This theoretical calculation will be the light grey dotted line behind the solid black line for the GPS plot line.

The Traxxas telemetry data is first imported into a list which catalogues all my runs by date and description with min max values of each entry (as shown in the screen shot above). With each run listed, I am allowed to place the focus on either a min or max value from one of the telemetric sensors and graph the logged data points before and after that point. The number of points before and after can be customized. The graph could also be shown of the entire run.

For example here are some of my base line run data using my current setup and only replacing the clutch bell bearings with Boca Bearings. It is an unbelievable difference in take off inertia. The CB spins consistently throughout the friction point or engagement of the clutch shoes. In these acquisitions, I was using the typical Traxxas clutch compound - I believe it's a plastic/carbon combinations. We will use these as comparison runs. The future Boca Bearing replacements will be compared to these runs in this Workshop.

Fastest run yet!

Since installing the new ceramic clutch bell bearings from Boca Bearings I have just now recorded +3mph improvement. I accredit it to the super smooth clutch engagement using my new ceramic bearings. This is only the beginning. There have been faster at 67mph, however I failed to record it, arghhh!

It's getting close to what the box says but I am intentionally running it rich for my protection.

Please see my saved Link App “screen record” at 63mph
( file: New Ceramic Bearings in Clutch )

Please see my speed run pass on video with factory bearings
( file: Speed )

What are my goals?

A) Reliably fast!

The engine must be reliable and easy to start. Traxxas took care of this with the EZ start system by Traxxas. It was a big factor in purchasing a Jato. The engine has to breathe properly, no leaks so it would consistently start. So to be sure I used a brand new carburetor and replaced all the exhaust seals. Next the tuning was very important. This took the better part of last season. It gets cold here around October so that was my last and final tune before some speed improvements were made. Lastly, I know factory bearing seals aren't the best at the engine. This makes for a fussy task in tuning and maintaining a tune. I am looking forward to replacing the front and main engine bearings. This should keep the air leaks at bay and provide that “absolute-tune” I am looking for.

B) Handling

The suspension had to be perfect since my experience with bad suspension steering was an all too common introduction to the curb. I first set the suspension high for a higher center of gravity and 40 and 50 weight silicone in the shocks. This mistake was pointed out by my colleague who races modified 1:1 rock crawlers. It was the reason my truggy would cart-wheel down the road like a gymnast on caffeine! It was revealed to me the secret to suspension travel is that there must always be 1/2 the rod in the damper to allow the springs to move into the terrain and come back up. In my video of speed runs, above, I crashed. I didn’t have enough travel causing my shocks to bounce after bottoming. This is the reason I am considering changing back to stock springs.

The most important part of my suspension changes was the elimination of the nylon bushings and conversion to bearings. The steering improvements were great but there was a catch. I will explain in my bearing replacements why ceramic Boca Bearings are the only choice for this improvement. The aluminum drag link with steel bearings was added. I will get into why these bearings should also be ceramic Boca Bearings in my replacement. The steering is precise, the suspension is soft and quick. We know have a speed-run truggy!

C) Power to the Road

The PL Road Rage tires give the best asphalt traction and overcomes some light contaminates like gravel (used here in the winter for traction). The tires are cleaned with a brush and laundry stain remover for a factory clean rubber each time.

I purchased a propeller balancer to balance my wheels. This eliminated any high speed vibrations as the car makes its speed run passes.

These vibrations prevent the wheel bearings from spinning on center. This creates a resonating effect at high rpms. This effectively slows down the car and prevents the shocks from moving quickly and smoothly. Balancing is done before and checked after a few runs to ensure even wear on my tires. These wheels can spin faster! The bearings, of course, will be replaced for this Workshop.

D) Speed improvements

There are many elements that I could have and still might yet do to lighten up the car. But for now the parachuting effect of this car is incredible and I have to be careful of weight placement and body modifications. So the following has been done to improve weight and speed.

a) Moved the 4cell receiver battery the center of the car
b) Tuned the engine to maintain an average 250degF speed run temp
c) Gear ratio of 2.0 ratio between spur gear and clutch bell (using a Revo pitch)

These changes were made over the winter but I could not get the performance I was expecting. I was beginning to hit a wall with my Jato. I started researching bearings since I believed it to be heat and friction.

E) Friction reduction = less heat = performance improvement

This is where Boca Bearings comes in. I was suspecting friction to be my next improvement and it was set in stone the moment I took my new 2.0 gear ratio for some runs. My clutch bell bearings seized and this would be the last time. Over this past winter I was messing around with CB balancing and the removal of the CB bearing lube. I suspected slip and therefore performance loss. I knew from the heat (350degF) and rpms ('unloaded' reached 41,000 rpm) that this nitro engine would destroy, dry factory bearings. These factory bearings only had about 12 tanks on them. I suspect this is normal wear for factory bearings.

F) Finally, what's the Scoop?

The intention is to create a repeatable machine which performs as fast as possible every time with the best handling. The repeatable engine performance will come from the best bearing seals and the highest grade bearings for the stock Traxxas engine. This will create the absolute tune I am looking for. The horsepower of the engine won't be lost when the power is sent through the transmission running on these new bearings. Overall it is about getting all the power to road everytime without destroying the truggy.

G) My first Boca Bearings!

I decided to purchase my first ceramic bearings. So I did some research and found the Boca Bearings to be an excellent source (easy to navigate website, excellent reviews, fantastic support to name a few).

My first test was small to prove a theory. I replaced my clutch bell bearings with a set of Boca Bearings SMR115C-YZZ #5 LD that means a 5x11x4, ABEC #5 hybrids, SS races, shielded with no lube. The moment I unpacked my new ceramic bearings I was blown away at how smoothly they spun.

As a note, in this hobby we use what's known to the bearing industry as a miniature bearing. In small applications the small steel ball bearings will have normal sized pitting expected of steel, but, it makes a huge difference in performance when they're ceramic - non porous and no pitting in the bearing surface.

As with all mechanical engineering we have to account for more than just the bearing. In this hobby we have the most to gain from ceramic bearings since the inertia is virtually non-existent when compared to larger applications. High RPM + low inertia = greater gains from precision bearings.

I was so impressed with the effortless movement of my new clutch bell with ceramic bearings I wanted to put it to the test and start comparing. As already posted I showed the results to a Boca Bearings rep and they were also impressed. Impressed enough, to show how improvements can be made by replacing all 30 of my Jato's bearings.

Note in my speed runs I have a factory body in an orange type color. This one is swapped in for my speed-runs. You may notice a red type body in my media submissions. It is important to note that both are of the same car.

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