Foell.org

At the front end is a Renogy 100 watt portable solar panel and a MPPT controller. This model is more expensive (at $275) than the normal $1-per-watt deals you can get on just panels. But it folds nicely, comes in a carrying case, and includes a waterproof controller and all necessary wiring.

The panel turns sunlight into power, and the MPPT controller decides how much power goes to the battery. It has several settings for different 12-volt battery chemistries (Lithium Polymer, Lead Acid, AGM, etc.).

For my “energy sink” battery, I went with a tried-and-true Interstate group 27 deep cycle battery that I got from Costco for about $100. It’s got 160 minutes of reserve capacity, so figure about 67Ah at 12v. Pro-tip: the deep cycle batteries aren’t available at Costco in the winter here. You gotta get them in the spring when Minnesotans are bringing out their boats.

I call it a sink, and I drew it to look like one in the illustration because I like to think of the stored energy like water in a sink. Energy in the sink can be emptied to charge another battery, it can be refilled by the solar panel, and it can be refilled from another battery. I’ll show you how…

Regenerative charging

My favorite part about this setup is with the right charger, I can do regenerative discharging. I did my research and found a couple of chargers that can do fast discharging by reversing power flow and putting energy back into the input – the energy sink. The two chargers I’ve found that will work are the Turnigy Reactor and most Junsi iCharger models. I went with the iCharger X6 because it’s extremely portable and packs a powerful 30-amp punch.

Why do I want to do regenerative discharging? When I go racing I usually bring two batteries for every vehicle we’re going to race. I’ll use one during practice and charge the other for qualifying and racing. At the end of the day, usually a 5-8 minute practice, qualifying session, or race isn’t even close to getting the battery to its most stable resting (storage) voltage – 3.8v per cell.

A quick way I had been discharging was to use a AOKoda Cellmeter 8 to bring their voltage down to 3.8v per cell. It works incredibly fast because I can draw up to 150 watts of power by running three 50 watt incandescent bulbs. The power turns quickly into heat and light.

But why not recapture that energy instead? Regenerative charging allows you to put that energy back into an energy sink battery just as quickly.

X6 regenerative discharging setup

The X6 has 4 “input source profiles” that you can use to tell it whether it’s being powered from a normal power supply or a battery. You can give it parameters for how much power these sources can deliver and whether or not they are regenerative.

To set up the input sources, first get to the system menu by pushing and holding the nav wheel down from the home screen. Then you can go to the “Input & Power Limit” section.

You then select one of the four available profiles you want to edit.

This is my setup when connected to the deep cycle battery. My Costco/Interstate battery has a reserve capacity of 160 minutes (at 25 amps). I set the max current to 20A so even if there’s no solar power input, I should get over 3 hours of charge time at 20 amps – but I’m never charging at that rate anyway.

Check the regenerative enable box to get those options. Here you need to know what the fully charged voltage you want to stop at and what the max charge rate is. This will vary whether you’re using lead acid, LiPo, LiFE and how many cells it has. Maybe you want to use something like my 6S lawn mower battery as the energy sink. Regardless of what you use, you need to know the max charge rate and voltage.

Based on my 67Ah deep cycle battery, charging it at 10 amps is a 0.15C charge, or 15% of its capacity. That’s between the recommended 10-30% of capacity rates. Best to be conservative here.

Discharge vs. Storage Programs

Once regenerative charging is enabled on the input source, we need to also enable it on the discharge setting for your charging profile(s).

Why Discharge and not Storage? Because storage is a smart mode that will either charge or discharge cells based on whether or not they’re above or below your target voltage of 3.8v. As long as all of your cells are above 3.8v, you can use discharge mode and set the discharge voltage to 3.8v instead of the default 3.5v. The charger can still do some balancing of the cells on the way down to the target voltage – enable it in the “Advanced” section of this screen.

There are several safety measures built in to make sure you don’t send power back to something that can’t accept it. The iCharger will warn you here with a yellow exclamation.

Once you’ve enabled Regenerative Mode, when you go to run the program, Discharge will have “REG IN” in red next to it.

One last safety feature – when you select discharge it will give you another confirmation on whether or not you want to do a regenerative or normal discharge.

Now you’re taking energy out of your RC battery and putting it back into the source energy sink! In the lower left you’ll see RE in yellow & red with the voltage and current. No wasted energy to light or heat – just put it back where it came from

Wireless Charging in Action

Here’s my setup at the track. On a sunny day I’ve seen the MPPT controller send out 6.0 amps to the battery. At 14v that’s about 85 watts. Not bad. Without taking away any battery charge from the energy sink, I can charge a 2S battery at 10A, and my 6S lawn mower battery at 3A.

Do you have any other green charging ideas? Let us know about setups you’ve built or seen in the comments.

The post Solar Charging Setup appeared first on Meatball Racing.

The Arrma ATX-300 transmitter & receiver I switched to for left handed use is a 3-channel unit. The 3rd channel is operated by the yellow triangle button at the top of the handle. This would be perfect for the firing mechanism. The button is even on both sides for right or left handed drivers.

With the parts gathered, I just needed to make things fit. The Dromida truck has a large firing mechanism in back, so the possibility of simply adjusting the LaTrax body post height was out.

3D Printed Solution

So I decided to design and 3D print a set of body posts that would fasten into the LaTrax chassis, but were purposely designed to fit the Dromida body without the need to drill any new holes.

Here’s the design: https://www.thingiverse.com/thing:3641857

Result

After a few revisions I got the fit just right:

I designed the posts to align the body with the front bumper right behind the grille. I did have to do some fender trimming with a body scissors on both the front and the rear fenders to avoid any rubbing during steering or suspension compression.

It’s like I’ve combined the best of both worlds. This thing shoots far! It frankly caught me by surprise the first time I fired it. Guaranteed to put a smile on you and your kids faces. Just don’t shoot anyone’s eye out!

I’m still experimenting with materials. My first 3D prints were from PLA filament but we’ve already broken a couple sets. I’m going to try PETG filament as I’ve heard good things about its durability, specifically for RC. I’ll update the notes at thingiverse as I improve them. If you’ve got any tips to increase strength through design or materials, let me know in the comments below.

The post LaTrax Wasteland Mashup appeared first on Meatball Racing.

I think it is spot on!

Because some of you might have 3D printers already, I’ll link my products to the STL files so you can print them yourselves. I’ll offer them for sale (with low shipping costs) for those who do not.

Keep in mind that sometimes it will be cheaper to order through MeatballRacing than to print it yourself. In the case of this Traxxas fan mount for most 2wd vehicles (Slash, Rustler, Stampede, Bandit) – the cost of the hardware alone would be more than ordering it from meatballracing.com direct.

Do you have any ideas for 3D printed parts? I’ve got some ideas in the hopper, especially for the venerable Traxxas Slash – maybe you have some as well? Let us know in the comments!

The post MeatballRacing 3D printed products appeared first on Meatball Racing.

MeatballRacing is going to debut a patriotic-themed Slash product in May, so I wanted to church-up my jump to go along with the theme.

I got an American Flag Distressed Stencil in 24″x18″ from Stencil Revolution. While I could have easily do a single-color paint job with it, I figured I could creatively reposition the stencil to get a full-color, red-white-and-blue, star spangled banner!

To make sure the paint would stick, I sanded the surface of my jump with some 220 grit sandpaper. I went in one direction, then another to create a crosshatch pattern.

For all of the paints I used Rustoleum 2X Ultra Cover spray paint – based on recommendations that it works well on plastic.

• Gray Primer
• Gloss White
• Gloss Apple Red
• Gloss Deep Blue

I started with the primer. I masked off some edges, which isn’t strictly necessary, but they’re useful as guidelines when removing & replacing the stencil.

Then it was time for the red stripes. I put some paper behind the stars as a mask. Then painted red in the striped cut-outs.

After the red dried, I repositioned the stencil slightly to the left and slightly up. I did this to cover the red I already painted and also so the angle on the top-most stripes would match up with the red and the white.

The last part is putting the stencil on for the last time to paint the stars. I went a little too thick on many of my coats, and the stars were no exception. I should have done multiple lighter sprays, but the few stars that bled don’t bother me – it adds to the distressed look.

Once your jump is done, it’s time to give it a go.

If anyone out there has done some artwork beyond adding a ton of stickers to their jump, let’s see a pic. Post up in the comments below.

The post Send It, ‘Merica! appeared first on Meatball Racing.

To pre-empt any bashing that would take place during the first track session, I removed most of the scale details:

• Windshield wipers
• Antennae
• Side-view mirrors

I left the scoop on since it’s low-profile, and also the wing since it might actually help on jumps.

Despite these efforts to keep the body in usable condition, I found out very quickly that the shell itself is not very durable.

First Laps

It did well on its first time out:

The S1 compound tires gripped nicely. I didn’t even add traction compound. My gut tells me that if there was a big SC Rally scene, the more commonplace stock Traxxas rally tires would also do just fine with some traction additive.

Traction Roll & Wing Durability

Once the tires warmed up they had enough grip to (inevitably) traction roll the vehicle. The general shape of hatchback rally car bodies is good because odds are the car will land back on its wheels. On my first roll-over where I landed upside down, I got hit by another Slash and the wing exploded.

Thankfully it was my nephew who crunched it, so I can’t really harbor any remorse.

Body Durability

Also, at one point I grazed the outside of the back straight and it almost completely tore off the front fender.

Needless to say the Basher/BSR 1/8 Rally Body is not up to the task of a full season of door-to-door racing. If I go all-in on this rig, I will instead get a thick (1.5 or 2mm) Deltaplastik lexan body.

Otherwise everything else performed nicely. Besides losing the wing and the fender, there was only a small nick along the body’s front edge, so the bumper did its job well. The tires gripped well. It drove and jumped predictably. It was great seeing a full-bodied rally car out on the track – mixing it up with other buggies and trucks like it was the Baja 1000.

More Power?

I got to trade transmitters with a fellow rally driver who had a 4WD Traxxas Rally. It had a brushless system on 3S power with insane speed. It was actually too fast for most of the course, but it made one jump very easy. It made me wish my brushed rally car had just a little more power to make the first jump in the turf series right in front of the drivers stand.

The brushless rally car could jump right onto the 2nd platform, making this obstacle more smooth and fun. But I wanted to stay true to the low-cost vision of a Spec Slash based rally car. One jump didn’t detract from the smile I had on the other 99% of the track.

The post SC Rally Testing appeared first on Meatball Racing.

It was basically a 1/10th scale touring car with longer shocks and more suspension droop for a higher ride height. It also had a raised bumper for clearing bumps. Team Associated followed suit by offering a conversion kit to make a TC3 Rally. For the next 20 years various manufacturers have taken a stab at the rally game, some lasting longer than others.

RC Rallying Styles

RC Rallying overseas is done on scale courses where the driver follows the vehicle through the course which can be incredibly complex and/or long. It is very similar to RC rock crawling but at a much faster pace.

The SoCal RC Rally Runners stateside do a similar time-trial like setup, but on a smaller course where there’s (ironically?) less running. Lots of scale details have been added including bridges and small jumps.

But I’m OK with giving up a little bit of the scale detail. Why not run them at one of the many off-road tracks our country has to offer? We’re here to jump right? Sure the jumps will be comparatively HUGE, but if the cars can handle it, why not?

Also, as much I love WRC and the time-trial game, nothing beats racing RC cars door-to-door with your friends. I’m thinking something like what Ultra4RC racing is to crawlers… traditional main racing, just with rally cars. By racing at traditional off-road tracks, we’re going to need to go big with these cars.

Short Course Rally

Traxxas has been selling the venerable Slash for over 10 years now without many changes. What that means is there are a bunch of 2wd Slashes out there that are sitting on shelves, collecting dust. SC (Short Course) Rally would be a new lease on life.

Sure Traxxas already makes an out-of-the-box rally car based on the Slash 4×4 – but I want the sheer numbers of the 2wd Slashes out there to be able to participate as well. So keep driving your Traxxas Rally if you’ve got one, and if you’ve got a 2wd Slash or other short course truck collecting dust, consider this easy conversion. To keep costs controlled, I put together an example 2wd spec class list:

Spec SC Rally2

Truck

• Stock 2wd Slash (brushed motor, high center of gravity chassis)

Body

• Any fully-fendered car body (no truck/buggy bodies) – most 1/8 scale will fit. Here are some examples:
  • HobbyKing BSR Racing 1/8 Rally Pre-Painted Body
  • Deltaplastik
  • Parma
  • Traxxas 7411(X) 7412(X) 7416
  • Pro-Line/Protoform PRFX
  • Team Associated 7180 7181 7182
  • Baja Bug (Pro-Line) and BAJR (J-Concepts) fans – these are not full fendered. You should instead look at the Deltaplastik New and Classic Beetles.
• Pro-Line extended body mounts

Foam Bumper

• RPM wide Rustler bumper + Traxxas Rally Bumper Foam OR
• Integy Foam Bumper (for bodies with a longer front overhang)

Wheels & Tires

• RPM offset-compensating front A-arms – these could be considered optional, they just add +3mm of offset to the front so the wheel offset matches the body & rear tires.
• Traxxas 7471 Rally Tires (widely available, pre-mounted as 7473) – the reviews on loamy dirt were only fair but it would probably do well with traction compound like Spec Slash tires do
• Traxxas 7471R S1 Compound Rally Tires (less common, but better grip)

SC Rally4 & Beyond

If main style off-road rally racing catches on, there would obviously need to be a class for 4WD rally cars too. I imagine the class rules for this would accommodate all of the short-course based rally cars from various manufacturers. Some simple dimensions might be:

• Wheelbase 300-335mm
• Width 260-300mm
• 2S Battery
• Possibly a spec brushless motor? Maybe 4WD is destined to be a modified class.
• Some minimum weight standard

The real equalizer should be tires. Settling on pre-mounts such as the Traxxas 7471 or 7471R would be a good place to start. It would avoid racers messing around with the tire foams and wheels, trying to find an advantage. Other racing classes such as USGT and Vintage Trans-Am have seen great popularity by having spec tires and simple rules which encouraging close racing.

Testing

Rather than just dream about all of this, I put together a test SC Rally2 platform to see how it would perform. Tune in to the next article to see the results.

The post SC Rally Proof-of-Concept appeared first on Meatball Racing.