Friday, June 23, 2017

Just some pictures of my rc cars.

This is my TC4 wearing an non approved Barracuda body.


M workbench is rarely organized at the track.  But most of the cars are there.  The DT-02 is under the TT-02b body on the top left, the TT-02b is on top of the rail...


The TC4 wearing my practice body.  


The TT-02b just before it's first run.


Another shot of the TT-02b


My M05 ready for some street action.


The body on the M-05 is really very beat.


This is my DT-02.  It's a fun basher buggy.


The insides of my DT-02.


An Audi Quattro body on the M05.  Metallic silver doesn't play nice with the light dry coats method... so it's not pretty.


This is the special grease that Team Associated sells as green slime.  


The M05, before I screwed it up by driving it.


The ultra mini CVA shocks for my M05


I have a spare body, that will get painted like this.


First night at the track.


The TC4's initial build.  

Monday, March 6, 2017

DT-02 - Tamiya's do everything 2wd buggy



So lets talk about the DT-02.  

It's got all the features of a fancy buggy, at a hilariously low cost.  For reference, I bought one of the midrange models, for $110.  


A Little History

First, lets talk a little history.  In the early 1980's, Tamiya started releasing "cheaper" off road kits.  Tamiya had sold off road cars before, but they were high end products for them.  First came the Frog, in 1983, and in 1984, everyone's favorites, the Grasshopper and Hornet.  

This was just the start of a long list of cheap, versatile chassis that Tamiya would sell.  

Jumping forward a decade, Tamiya began the DT series buggies.  The 1996 release of the DT-01 was more or less, a Hornet, with decent shocks.  Still live axle in the back, still swing arms up front.  A transverse mounted battery.  The DT-01 was a kit dancing on the edge of Tyco, Nikko, and other toy store brands.  But, we're not here to discuss the merits of a fancy Grasshopper are we?  

In 2005 Tamiya released the DT-02.  https://tamiyabase.com/index.php?option=com_joodb&view=article&id=104&joobase=21&Itemid=1063  The chassis was set to bring back at least one classic car from Tamiya's history.  The holiday buggy.  As well as provide a platform for other hard shell, and polycarbonate bodied cars.  

About the Buggy

In comparison to Tamiya's other buggy designs, it was a very modern design.  Four wheel independent suspension, with a-arms and upper links.  The steering setup is classic Tamiya off-road. (for better or worse...)  And the gearbox is just about what you'd expect from Tamiya.  That is, nylon gears, sealed, and .6 metric pitch.  


The high points:
  • Plastic Tub Chassis
  • Sealed Gearbox
  • Crud Proof Steering
  • 4 Wheel Independent Suspension
  • Durable Tamiya ABS plastic
  • Reasonable Upgrade Path
  • Easy Battery Management
  • Just One Bearing Size
  • Dirt Cheap
  • Includes a Motor
  • Sealed Power Switch


The low points:
  • Most models come with friction dampers
  • Limited Gearing Options
  • No Slipper Clutch
  • Soft Front Shock Tower
  • Designed for Stick Packs
  • A Bad Case of Bump Steer



Criticism of the DT-02

One of these days, Tamiya will start building their kits without bumpsteer in them.  But 2005, was not that day.  Between the unequal length steering links, and the absence of a rack to get pivot points in line, there's really not a whole lot that can be done.  

Access to the steering servo, for replacement or maintenance, is a bit troublesome.  It's a six screw job to get in there.  And being trapped under the chassis brace also limits the choice of servo saver.  

The chassis tub, and battery retention strap are really, very specifically, designed for stick packs.  With a little trimming you can get hardcase lipos to fit.  But it's not an ideal situation.  

Due to the motor surround, and gearbox design, getting wide gearing options is more or less a non-starter.  The gear cover holds one end of the spur gear shaft, this prevents easy changes of spur gear.  

Building the DT-02

First, this is now departing into "my experience" with the DT-02.

Building the DT-02 is typical Tamiya.  That's high praise.  The manual is good, and is specific to the version of the DT-02 you buy.  (I bought a Desert Gator)  And if you follow the directions, it all comes out perfectly.  

Be sure to have a JIS screwdriver, as that helps with the initial threading of screws into plastic.  A decent set of needle nose pliers will help assembling the CVD shocks if you got one of the ~better~ models.

Not counting the body, it took me about 3 hours to go from "pile-o-Tamiya parts" to "complete DT-02."


Painting the body was easy.  It's not easy to cut out, but the paint job is certainly easier than doing the paint on my Miata body for the M05.


Just a few words of advice.  First, pearl white, is not a solid coat, and needs a backing white paint.  Second, be sure to let your coats dry, and use very thin coats when painting over an existing coat.  

The decal job, is big.  But covers up most sins.  


The wings are usually molded "inside out."  so you need to do all the masking instead of trusting the build in overspray mask.  


All done, it looks a bit like this.  


It's a good looking buggy.  At least the desert gator is.  The Holiday Buggy, and other hard body buggys look pretty good too.  But are a good bit heavier.  I bought this for running on the local off road track while my on road batteries are charging.  

So how about yours?
I bought a Desert Gator.  Which is about the same as the Sand Viper, minus the speed control.  As opposed to something like the Super Fighter G, which has bushings, and friction dampers, it's got CVA shocks and bearings throughout.  

Sadly, the bearings are "just" shielded, as opposed to sealed.  But it's definitely something.  


So instead of going to the track I've been jumping off of things.  It handles stairs happily.  It jumps well.  On high traction surfaces, it will even wheelie!  

With the stock motor, it's slow enough that it handles being run into things very well.  It's also fast enough to impress people.  (if not someone who's really into r/c...)

When I bought mine, I also bought one for a friend of mine.  We built ours slightly differently.  


My car is built light.  I have a Turnigy D-Spec shorty steering servo.  A 2600mah 90c, ultra shorty battery pack, and team blue spektrum receiver.  It's very light, to get the correct ride height I only need about 3mm of preload.  

The other buggy, is set up with a standard size steering servo, and a compact 4600mah battery pack.  It needed almost twice as much preload to get the ride height proper.

Both cars are a blast to drive.  But there are some things were both looking to improve.  

What needs fixing.
With many low end cars, it's tempting to go nuts "fixing" everything on the car.  Eventually you end up deep into a car, where you could have just spent the same money and bought something better right off the bat.  

Realistically, this is why I bought the Desert Gator, as opposed to a Super Fighter.  Adjustable upper links, Bearings, and CVA shocks is a lot of value.  

The car could really use a ball diff.  Or sealing the gear diff, and filling it with something really goopy.  

A brace between the front shock towers should help the cars tendency to bounce the front end over ridges.  

There is some room to run bigger pinions, but you'll need to enlarge the motor mounting holes.  

How can I buy a DT-02, whats the best to buy?


  • 93031 Super Fighter G Black edition
  • 58340 Super Fighter G
  • 58344 Desert Gator
  • 58374 Sand-Viper
  • 58401 Neo Falcon
  • 58470 Holiday Buggy 2010
  • 58485 Super Fighter GR
  • 84212 Holiday Buggy (2010) Red version
  • 58500 Sand Rover 2011
  • 58522 Street Rover
  • 58511 Nissan Titan
  • 58536 Super Fighter GR (Violet Racer)
  • 58553 Fighter Buggy SV
  • 58615 RC Buggy Kumamonbajon
  • 49475 DT-02 MS


If it were still in production, the "car to have" would be the DT-02 MS.  Sadly, it's long past it's production run.  Today, the car to buy is the Sand-Viper.  It comes with bearnigs, CVA shocks, adjustable upper suspension links, and an ESC.  (one that supports brushless motors too!)

The cars start at $100.  They're a lot of car for $100.

Tuesday, December 6, 2016

So lets talk about Batteries. Vol 1.

So let’s talk about batteries.
Many things about batteries depend on each other. Most people flying race quads are going to be flying 1300-1800mah 3 or 4s battery packs. I’m going to assume you know what mah are, and what 3s and 4s mean.
Chemistry is what really limits our batteries. Reaction area, and speed of the atoms and molecules. Reaction area, for LiPo’s works out to “physical size”. Speed of atoms is “literally” the definition of temperature. The warmer something is, the faster that reaction can happen.
LiPo batteries are built of thin layers deposited on big sheets of polyester. (I think it’s polyester) Some Lithium, Some carbon, a membrane that’s impregnated with an electrolyte. Those sheets get rolled up or folded up into the shapes we’re accustomed to seeing. If you’ve ever seen a bunt up battery, you can see those layers peeled apart. Durable batteries have thicker layers. Durable batteries have higher C ratings. We’ll come back to C ratings in a few moments. Batteries with more capacity, have bigger sheets of battery. These directly relate to the size of a battery pack.
For my 9xr ratio, I had a 2c 2200mah 3s pack, that was smaller than 1500mah 20c 3s pack. A 45c 1500mah 3s pack, is about the same size as a 2200mah 20c pack. This is due to the tradeoff of cell area, and cell durability. “Stronger cells” are thicker.
Now we need to talk about abuse. And abuse is something that we do ~very well~ in the multirotor community. Tiny batteries, steep pitch, and multi blade props, four 20-30-40 amp ESCs and 2000kv+ motors. (High Kv essentially means “low turn” for the r/c car guys.)
Battery packs beyond their capacity and number of cells, are rated on the “C” rating. C is “the capacity of the battery” The “C” rating is a multiplier of the capacity of the battery. This lets you do some math to figure out how to treat, and what is considered abuse of the battery. There’s going to be a separate charge rating for both charge, and discharge. Typical limits for charging are in the 2-4C range. That’s 2-4 times the capacity of the battery.
For instance, if we have a 1300mah battery pack, we could safely charge it at 2.6 to 5.2 amps. Slower charging is always better for a battery. To a limit… I don’t have any research handy, so I’ll say you don’t want to charge LiPo at less than 1/10C. This relates back to our bag of chemicals, the slower we charge, the more time atoms have to do their thing. The slower we ~need~ them to move, the less likely they are to damage their surroundings. If you exceed the speed that those chemicals can react, ~things~ start happening. For instance, electrolysis.
Electrolysis is the splitting of chemicals via electricity. Generally, it’s water, and that’s how we get puffed packs. When you push a pack to hard, and you get water splitting into H2, and the O2 then oxidizing other parts of the pack, you end up with a puffy pack, and less reaction area due to oxidation.
Let's stick to abuse. Charging, or discharging quickly, causes heating. Moderate heat can be a good thing. Batteries can “have things done to them” faster, if they’re warmer. To a limit, either by generating vapors, or, let's say, fire.
When charging, or more importantly, discharging, heating comes from within the pack itself. While we’re used to the idea of batteries providing power, they also consume some power. All parts of an electrical circuit, have some resistance. That includes LiPo batteries. This resistance is called “internal resistance”. For LiPo batteries used in commercial situations, which frequently see ~very~ cold temperatures, the procedure for starting involves a two step process. First, is “knowing” the cart/truck/plane won’t start, and applying the starter for a few seconds. This puts a high load on the battery, warming the pack. Then, you wait a few seconds, and try again. The engine would start on the second attempt, because the warmer battery could provide more current without the voltage sagging under load. Some r/c car people have taken to preheating their LiPo packs with some very high C charging. We’ll come back to voltage sag.
Now i’m making it sound like batteries being warm, is good. Unless you’re having peak current issues, it isn’t. Batteries age in relation to their temperature. The warmer they are, they faster they lose capacity and C rating. It’s better to keep batteries cool. Cold even. But not frozen, as that can cause the electrolyte to freeze and directly damage the cells from the inside.
In the past, the internal resistance of batteries were there to save us. You could short out most NiCad, or NiMh batteries and nothing would happen. They’d get warm, and finish discharging. No ~real~ drama, excepting some of the very latest NiMh cells, funny, that was discovered by the r/c car guys too. Maybe we should stay away from r/c car people. Do the same with LeadAcid, and you might get some steam… Their discharge would be self limited by chemistry and internal resistance. This, is not the case with LiPo. The internal resistance of LiPo packs are often in the miliohm range. This means we need to do current limiting somewhere else. Sometimes we don’t….
And when we don’t, because a lot of us use OSD’s, we’re aware of “voltage sag”. Voltage sag is what happens when we get ahead of the chemical reactions that restore the voltage of our batteries. Voltage matters to us, because our motors are a long series of wire coils. And the speed at which we can energize those coils, is directly related to the available voltage.
Back to cell abuse, deep discharge of LiPo batteries is a problem. When the voltage is ~very low~ in a LiPo cell, some of the copper used in the battery can dissolve in the electrolyte. This makes it more conductive, and makes it more prone to runaway. It’s also irreversible.
So how do we stop our packs from dieing? Keep them somewhat charged, so they don’t dissolve into themselves. Keeping a battery charged also has it’s downsides, when you charge a battery, you’re forcing the battery into a state it does NOT like being in. That is, it holding the positive and negative poles as far apart, electrically, as it can. So the lower voltage you can store it at, the better. But batteries also self discharge, so you need to have “some” buffer. The generally accepted voltage is 3.6v, for storage. Finally keep them cool when stored. Higher temperatures increase self discharge rate, and the damage the cells do to themselves while stored.
I ~think~ I have all of that right. I didn't cover balancing or cell choice. But that gets into an even longer discussion.

Thursday, September 1, 2016

A little more Doink(er)

I made some more progress on the Doinker.  In fact, short of the props, it's complete.



There were a few steps leading up to that though.  I had to populate the PicoBlox.  The first thing I added was the power stub for the camera.



I really didn't get any pictures of modifying the receiver tray, and the spektrum satellite.  It's stuffed under the flight controller.  I have thick spacers under the FC to provide clearance for the satellite wire.



It's not the most pretty solution, but the "wedge them in" ESC mounts is quite elegant.


16ga wire is a little big.  Here I'm trying to get the receiver bound.  


Happily, I only got one motor wired backwards.  That's a first.  I've had as many as three of four spinning the wrong way.  The wires on the 1104 motors have varnish on them, so when you shorten, and strip them to attach to the ESCs, sand the wires a little, or else your flux and solder just ball up and fall off.

In the end, I swapped the 16ga lead for 20ga going to a JST plug.  Most of my multi cell lipos are either e-flite 3pin, or T-connector.  So I built two adapters to I can use all three kinds of battery without any real strain.


Next is to order a few batteries, and cut down some props.  





Adding FPV to a normal Micro Radian

E-Flite released a UMX Radian with a FPV camera on it.  I thought this was a great idea, but I really didn't like the idea of spending $99 on top of the cost of the glider for a $40 camera and a $7 mount.  

So the first step to adding FPV to a micro plane, is to get power for the camera.  That means cracking open your bird.  The canopy is held on with "just" tape.  The tape to use for putting it back together is Scotch brand 1/2" clear tape.  The glossy stuff.

The UMX radian has a additional speed control board.  There's three pins that feed it, and my pencil is pointing at it.  


The center pin is battery positive, and the pin nearest the sockets is ground.

I bought a bunch of eflite mini JST plug extension wires.  So I cut one in half and slipped it through the canopy.  To put a hole in the canopy, use a normal 3/32" drill bit and spin it in your fingers.

I taped the wires to the inside of the canopy.  Then I soldered the wires to the reciever.

And there we go, a plug on the top of my glider to power a FPV camera.  The factory FPV camera mount is $7 from E-Flite.  Or you can just hotglue your camera on.  

Thursday, August 25, 2016

Another duck day, and an even bigger project.

It's a giant steel box.  That's the bigger project.  Two weeks ago TheSwitchElectrician came by and we built the platform that the shed stands on.  The platform took us about 4 hours start to finish.

The next week, Dan came by, and he helped build the shed.  Actually building the shed took about five hours.  Shockingly long for a bunch of tin.  
  


It's pretty roomy inside, and looks to be quite weathertight.  I'm going to need to do something about covering the small gaps at the top, without impeding airflow.  Perhaps stuffing them with steel wool?  



Both hulls are really in the stage for sealing.  With our truncated build day, Dan and I spent it doing epoxy work.  Every screw hole needs to be filled, and due to the quality of wood we've got some oddball gaps at coerners and edges.  



I work at a telecom company.  One of the smocks Dan brought had a fun brand name on it.  


The hulls look really good after being sealed.  The lack of screws somehow makes me a lot more confident in the seaworthiness of the hull.  


One last shot.  I think these are just so pretty to look at.  


Next time, we're doing keel trunks, and perhaps mast steps.  

The desk is clear. That can't stand. A Doinker build.

My desk is a place of projects.  When it's clear I start seeking for something to do.  Two nights ago, it was clear..


Yes, I really do type with my keyboard that far back on the desk.  My wrists are very healthy thankyouverymuch.

I ordered my Doinker kit from 65drones.com.  Here's what came in the package:


In there we have the frame kit, four escs, four 1104 motors, a 40channel micro FPV camera/transmitter, and a flight controller with built in PDB.  Oh, and that giant awesome sticker.

It seems like so much less once it's unpacked.  The frame is 3d printed, and has the usual problems with 3d printed things.  It's also been sprayed with some sort of clear laquer, which makes it nice and shiny, and fills in a lot of the layer artificats from being FDM printed.  


The first thing they have you do, is install the reciever, in the reciever tray.  They expect you to go frsky, and my house is not a taranis house.  I'm going spektrum, so their tray doesn't exactly match what I'm going to install.  We'll cover the reciever install in the next installment.

The build directions on theshortcrayon.com are really pretty good.  But they don't cover where these little spacers go.  


They go under the 1104's, for prop clearance, I think.  But that's where the spacers are on when you look at the pictures on 65drones and the shortcrayon.  


I got "a little" further than this, but we're now to the point of needing to solder everything up.  I'll be doing that this week, and hopefully getting it's first flights in.