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Taking some time off for my hobby by building a Comical Hornet on the -02CB chassis.

Still pondering about the paint job, since I‘m pretty certain not to go with box-art.

First step is to take apart the preassembled gearbox to replace the plastic bushings with proper ballbearings. Whoever thought a prebuilt gearbox was a good idea, it is not! This is a kit after all, even a beginner friendly one.

Let the screwing around commence!

Taking apart the gearbox of the just takes a moment. These gears almost *look* bone dry, but they‘re actually somewhat greased.

The differential seems properly greased to me, nothing to do here. I‘ll add some more to the gears.

The white plastic and bronze metal bushings are all the same size throughout the kit. They‘re getting replaced with ball bearings which run smoother, and last longer. It‘s a key upgrade to make in my opinion to enjoying your vehicle for many years to come.

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As usual with kits, we‘re starting off with the A-Bag from the metal parts.

It contains the iconic Tamiya wrench, which is really super handy. A bunch of different tapping screws, screw-pins, outdrives, cups and dogbones and spacers. We‘ve already used the grease to prep up the gearbox.

The plastic parts come on sprues (or parts trees) which are labelled with a letter for the sprue and a number for the part. Each referenced in the manual.

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We continue with assembling the rear lower wishbones. The ball connectors will be the mounts for the shocks later on. The different mounting positions allow for vehicle setup like ride height and its tendency to wheelie.

The small O-rings in the drive cups help with sealing the gearbox and put a tiny bit of pressure on the dogbones that go in there to reduce slop.

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Opening up the b-tree we find rear uprights, front c-hubs, servo horns and saver parts, wheel hexes and some more bits‘n‘pieces.
The designator tells us this is black polycarbonate, a strong and impact resistant with a shiny surface finish.

I‘m replacing the dogbones and wheel axles with universal joints. The are a hop-up option party from a third party manufacturer named Yeah-Racing. This tuning part is probably not really necessary, but I prefer running universal joints.

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We‘re opening the two-piece sprue F which contains a few chunky parts. The main chassis frame, a huge and a ginormous front bumper, shock preloading clips, and a wheelie bar.

It‘s made from black Polyamide (Nylon) again which makes sense. These are chunky parts, and the ones taking a lot of the impact energy during crashes and the occasional unfortunate landing after a jump.

The wheelie bar is mounted with spacers to the rear of the gearbox.

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This concludes build group A if the Comical Hornet buildup kit.

There‘s a few left over parts from the metal bag A. A fee screws which can be used as spares. Sometimes you lose one. The bushings haven‘t been used because we immediately affixed ball bearings in the rear uprights.

The tiny allen key is used for mounting the pinion to the motor shaft which came already premounted. Should you want or need to change it, that‘s the tool you need.

We‘ll continue using the cross-wrench.

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For build group B we‘ll be needing metal parts bag B to complete steps 5 through 11 in the manual. I‘m sure you already sense a pattern here.

We‘ll need our electronics, to center the steering servo and then build the front suspension and main chassis.

This includes a cameo appearance of the transmitter.

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To connect the tie-rods to the servo we need a few parts. One piece that directly goes on the servo axle matching the correct number of splines. The C-shaped servo-saver clamp, and the servo horn that connects to the tie-rods via ball joints and cups.

The correct length of the tie rods is stated in the manual and also how exactly it is measured. It helps having calipers available, but if you don‘t you can just align your piece with the 1:1 print in the manual. This applies to screws as well.

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Getting out the D-tree now, which is made from ABS. A common choice for chassis frames, like this one. The connections between part and tree are somewhat larger and rounded this time, so make sure to remove any burrs.

Mounting the servo takes just two screws and don‘t overlook the washer, like I just did. The rest is just screwing together the chassis sandwich and the receptacle for the front bumper.

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Getting out the M-tree now with front and rear bumper parts made of black, flexible Nylon. Also the front double wishbones, knuckles and C-hubs. A few bearings, screws, ball joints, screw pins, and even body clips.

It all goes onto the front of the main chassis.

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The front suspension fully mounted and the tie-rods are connected to the steering servo already. Wishbones are moving freely up and down and drop through gravity alone when lifted up. That‘s how an unloaded suspension should behave.

This part of the assembly is mostly done now.

Concluding group B leaves us with the screws we didn‘t need for our particular servo we used, so that‘s perfectly fine. The remaining screw pins, ball joint and screw are spares.

The 2 bearings are for the rear axle.

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Build group C, steps 12 through 15, may come as a shock to you because that what it‘s all about.
Building for shock absorbers.

The V- and W- trees made from Nylon will compose the inner shock bodies that hold the damper oil.

To keep this entry friendly kit easy to build, the damping rate of these is not adjustable. That also means, you can’t go wrong and mess up your suspension. :-)

Expect this to be partially messy, so have a few kitchen paper towels ready and a pair of pliers.

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We‘re building two pairs of shocks, one each for the front and the rear suspension. They‘re *almost* identical. The rear ones sport an additional spacer that limits their travel. Don‘t forget to put that on the piston rod before screwing on the end ball cup.

The ball cups come pre-threaded and go on easily and alined. Make sure the piston is screwed in all the way. The last part needs more force and you must hold on to the piston rod with protective cloth and pliers.
Then slowly fill with oil.

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As soon as all the bubbles have left the cylinders we can progress with closing them up with the seals and the top cap.
The process is put the green sealing caps on from the side so excess oil can spill over. You just wipe it off carefully with a paper towel.

Screw on the top cap, rinse and repeat four times.

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Only a few things left to do for build group C. Putting the spring preloading clips onto the shock cylinders, add the coiled springs and snap them into the bottom caps.

You may now clip the shocks onto the balljoints reserved at the front and rear axles. Should almost just snap in place by hand but feel free to use pliers.
Take care to put the ones with the travel limiting spacer on the rear axle and the remaining ones at the front.

You‘re left with O-rings and some sprues. This concludes C.

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In build group D, we‘re finishing the chassis.

There‘s a good amount of slightly different screws, screwpins, washers and other parts involved in these steps. Nothing that could scare you though. I like sorting the different bits‘n‘pieces on my parts trays to get a better overview and so I can more easily find what I need.

We‘ll unify the front and rear and mount body posts and even some LEDs.

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Front body post are mounted adjacent to the steering servo. The rear posts sit over the shocks with the taillights on either side.
Suddenly the hornet starts looking like a hedgehog. And it glows furiously red.

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Step 19 is where the side nerv guards are attached and the power switch. This step uses five (5) different types of screws and four of them are black and only distinguishable by length.
Getting the necessary screws sorted before starting this step and maybe mark them with a quick sticky note will make it easier.

If you accidentally mix up the left and right side, don‘t worry. You can take it apart again and flip a piece around. Just happened to me despite being in the hobby for decades.

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The funny looking dual antennae are a little fiddly to mount. Turning the vehicle on the side makes matters easier.

The manual also wants us to mount the speed controller and receiver to the top of the chassis using double sided tape.

I‘m using the kit stock ESC because it‘s a versatile piece of electronics and it‘s included. My receiver is quite different in shape and size than the one depicted in the manual though. So I‘ll happily divert from the guide and decide how to affix them later.

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@MacLemon neat! I never realized that the links were 1:1 scale in the manual

@MacLemon I buy cheap bearings in bulk (especially 5x11x4 for Tamiya kits haha) and I realized Tamiya could have bearings in every kit and only have to bump their prices up by a few USD.

since dirt can get into bushings and permanently damage parts, bearings should be in all kits

@ddipaola I buy bearings from a third party as well. A lot cheaper and they even make kit specific sets for almost any kit and vendor on the market.
If they don‘t have a set yet, just ask them and they‘ll put one together.

Small austrian shop.
modellbau-werkstatt.at/shop/th

@MacLemon I have used an Ubeck to transform 7Volt from my Libpo to 5 volt for my Raspi. (I used those in a robotics project)

why does this keep frying "hobywing U-Beck" s and similar?

@Wifi_cable What model exactly?

Assuming you mean “Why does it keep frying my Raspis?”.

UBECs are not meant as a normal input voltage converter (aka Step down in your case).
If you use them with a servo, that can draw 2A or 3A instantly, for a brief moment, or 3A for a longer time.
What often happens when the load goes away with these, is that the voltage overshoots for a moment.
Power Electronics in RC are often very dirty.

@MacLemon My Raspi is fine.This was the first time my electronics literally went up in flames.
Two kinds of UBECs released their magic smoke.
I know one was HWBEC Hobbywing 3A 5V/6V max 5A.

What is the difference between a step down that can handle 7V -> 5V for an hour and a UBEC?

Why would an UBEC die when supplying constant power to a Raspi?

@Wifi_cable Oh, the other way round they die. I see. Powering a Raspi 3/4, an Arduino and a few sensors will likely go over 3A at 5V.

The Raspi alone can use that much power depending on how much it has to do. They rise pretty high once the GPU is involved.

My best guess is that you‘re drawing more than 3A over a too long period from that BEC. Time to get out that multimeter or put a resettable fuse in there.

The 5A peak rate are for a few seconds only.

@Wifi_cable No idea what you need that UNO for, I don‘t see anything connected to it. Powering it through the Raspi is very inefficient though.
You could get the same 328p or 32U4 in a Pro Micro, Pro mini or Nano. Some can directly use up to 10V IIRC.
If you need a serial connection between them use the IO pins instead of USB serial.
This could already save up to a few hundred mA in total.

@MacLemon I needed the Uno so that a student team member could work on the project at home with her hardware. There is ultrasound sensor connected.

I checked the Raspie's Power consumption during boot and running various programs. Power consumption did not exceed 1A.

I did not think that an AVR (Arduino) would draw 2A.

@Wifi_cable I‘d expect the UNO to be around 200-500mA and the Pi at 3A max. During boot it doesn‘t use the GPU, so that is expected. If you also do CV that may rise significantly from the 1A at boot.

Still doesn‘t easily estimate to a constant draw way over 3A. :-/ Also doesn‘t suggest peaks over 5A.

Hobbywing usually are quality products, so I‘d expect them to be on spec.

RX and servo are powered via the ESC integrated BEC I assume.

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