Beyond Unboxing: A Dive into the Gear Vendors Overdrive

We’re going to skip ahead a little from the Summer of Ven into more the “Autumn of Ven” because I get to ramble about a cool mechanical thing. As one of the categories on this site, I often take apart neat things and make snide comments about their construction or internal parts. This time, it will be the Gear Vendors overdrive unit that lives under Vantruck, which I got for it in 2018 in a already very well used state.

I didn’t know how many miles it had on it already, and kept up with the recommended maintenance interval for fluid changes. It was just fine from 2018 until this past summer when it began slipping under load, and even worse, would occasionally seize in the overdrive state, leaving me barely able to reverse (and you’ll see why soon). Hauling so many vans back home probably did the unit in, finally.

I tried a few hacks, like flushing the fluid with a lower viscosity oil for a little while and cleaning the high pressure filter, neither of which really resolved anything decisively. Well, that’s how things shake out I suppose, so I called Gear Vendors to send the unit in for rebuild. What they do is go ahead and send you the new one and refund a core charge once they get the used unit. The total cost afterwards is about $1200 for a rebuilt unit, $500 of which is the core charge.

I’ll get to the install itself – first is the interesting bit, which is taking the old unit apart!

Here it is on the surgery ward floor after dismounting from vantruck. Notice that the input shaft is pulled out? It’s not actually attached by anything, and all you need to do is ensure it mates with the internal spline on the right side. I’ve pulled some kind of inspection lid off already, as my MO with anything on Beyond Unboxing is to start popping bolts off.

Inside the lid is the tail end of the output shaft. There’s nothing much going on here to speak of. I think this port is to install retaining clips.

The real bolts are around the perimeter on M8 studs. They come off fairly easily.

On the front, you need to remove the four nuts that holds the shifter piston’s end effectors, little bracket things, to the internal shifter ring. They’re gently spring loaded in this position, so the studs will pop inwards as you take the M8 nuts out.

When the shifter solenoid valve is enabled, oil pressure fills the two shifter cylinders (the round things behind the brackets). These two brackets then pop outward and collide some parts together inside that they’re linked to. We know from cutaway diagrams that it’s cone-clutch based, so presumably it’s connected to the cones.

Where does that oil pressure come from? The shaft that fell out has an eccentric lobe on one end, which rides in the circular socket seen in the center. That’s connected to a simple rod pump. So when you move, there is oil pressure. When you don’t move, you pray the seals are still adequate (though it seems like one or two pumps of the rod is enough to fill up the shifter piston chambers. Typically, to prevent leak-down from causing inadequate pressure to operate the pistons, the automatic controller you can get (which I didn’t install, because fuck using phone jacks as connectors) has a speed-based lockout.

And with those bolts removed, the whole thing just kind of splits open. Well there’s my first sign of something being wrong, the clutch cone has no… clutch on it.

Here are all the fun bits laid out in order left to right: the casing with the fixed clutch ring, the cone clutch assembly, the gearset, and the output. So what in the epistemological hell is going on inside these things, anyway? They rely (as most good things do) on the magic of planetary gears and their ability to add, subtract, and multiply speeds.

So the big showrunner of this basket of skulduggery is the cone clutch assembly, pictured center left. It’s coated on the outside (usually……..) and inside with clutch lining, and is the object being rammed into everything else.

I pushed the shaft back in for the assembly photo, but notice that the shaft doesn’t engage with the cone clutch, but actually with a splined bore inside the planetary carrier (center-right). When you spin the input shaft of an assembled Gear Vendor overdrive that’s at rest, you are applying torque to this carrier.

The sun gear of the planetary gearset is attached to the big clutch cone. This means the clutch cone controls whether the sun gear is fixed (grounded) or free to spin with everyone else including the clutch cone itself. This is important, because on the very right is the output cup, which acts as the ring gear (asteroid belt?) of the planetary gearset. It, too, is a cone shape on the outside, fitting tightly into the interior of the cone clutch under rest conditions.

So you have two choices for the position of the clutch cone. Either it’s spring-loaded (with a big throwout bearing seen below) into the output cup, or it’s pushed against the fixed clutch ring on the casing by the shifter solenoids.

In the rest condition, the cone clutch is shoved against the output cup. They rotate as one. With the sun gear affixed to the cone clutch, it’s forcing the planetary gears to also not rotate. If you overtorque the system and overcome the cone clutch friction, there’s one more line of defense left: the planetary carrier on one side is a very large spline that fits into the corresponding spline in the output cup, around which is a one-way bearing.

Therefore, in the rest condition with the vehicle powering forward, the torque is taken up by either the cone clutch friction or the one-way bearing forcing the carrier’s torque (which is your input, remember) straight to the output shaft.

In the overdrive condition, the cone clutch shifts forward a half inch or so and mates with the fixed clutch ring on the outer casing. The sun gear is stopped dead, and the planetary gears are forced to mate in orbit around it.

The good trick here is when you have a planetary gearset in that condition, the rotational speed of the planets adds to the rotational speed of the carrier. A gear that mates with the planets, like the output cup, will get flung faster than the rate at which you spin the carrier (/the input shaft). You might say it’s overdriven. In this situation, the one-way bearing capitulates and spins freely as the output cup is now moving positively (faster, in the same direction) relative to the carrier.

So there you go. That’s how the thing works in forward. Here’s a better view of the stackup from the end view, showing the big throwout bearing that controls the cone clutch and the also-conical shape of the output cup, and its one-way bearing inside.

When using a GV unit, you’re advised to not reverse while the unit is active (shifted in OD). The automatic controller (which I didn’t install, because fuck using phone jacks for anything) has a reversing switch lockout so it automatically disengages. Also, if a unit is severely worn, reverse is also generally difficult or impossible as it slips even in the rest state. The reason this happens is a unique property of the angle of cut of those planetary gears (they’re helical cut) and the liability of having a one-way clutch.

Cone clutches work on the principle that the two cones crammed together create an outward normal force many times the force pushing them together axially. The same principle governs tapered spindles in machinery. To work properly though, you generally have to keep holding them together. If a force exists that pulls the cones apart, they’ll decouple quickly.

The helix angle of the planetary gears creates an axial thrust load when the gears are transmitting torque. The direction of the helix is very important here. It turns out, by observation, that the helix is purposefully set to 1. Pull the clutch cone tighter in the OD and forward-torque condition, as well as 2. failsafe in the off (rest) position.

In the overdrive position, with the input shaft applying positive torque “Forward”, the helical thrust force pushes the sun gear into the clutch cone, which forces it more into the fixed clutch ring. That is, to the left in my explosion photo. It took me a while of staring to realize this is the case, and it makes the engagement more solid: As long as you’re applying drive torque, the system will tend to keep itself engaged.

Reversing in the overdrive position is a problem, because now the thrust force is pulling the clutch cone away from the fixed clutch ring (Towards the right, in my first exploded photo). At this point, you’re fighting the oil pressure in the shift pistons. At low-to-no speed, the oil pressure is not high, and likely leaking down slowly. The applied reverse torque at standstill wins, the cone clutch begins disengaging from the fixed clutch ring, and you don’t go anywhere fast while slowly grinding the clutch down. In real life, this is manifested as a really ugly squealing sound as you only maintain roughly idle speed in reverse, if at all.

Oh yeah, that one-way bearing isn’t helping you in this case either, because if you’re spinning the planetary carrier the wrong way, it doesn’t engage.

In the rest position, however, with the clutch cone now forced against the cone of the output cup, reversing torque now turns into thrust load which shoves those two cones together. The one-way bearing still doesn’t help, but at least your system is trying to be in a positive-feedback state. The reversing torque is still ultimately limited by a 3/4″ wide clutch band, and if this band becomes too worn or disappears, you could lose reversing power entirely. However, the general story seems to be it’ll try its darndest even severely neglected going metal on metal, because of the thrust of the planetary gears helping keep the cones together.

So there we go. Quite a clever mechanism with a few foolproof design choices to improve overall reliability. If the helical gears were cut with the spiral the other way, everything would have sucked more. That’s easily something I see myself doing, so good thing I didn’t design this thing, huh?

Alright, I’ve satisfied my curiosity and am now ready to put it back together so I can ship the unit back to Gear Vendors. I dunno what it is that I did, but I can’t quite get the thing to close again.

So I just left it halfway open, put the nuts and washers in a baggie, and left a note explaining myself.

That’s all for this episode of Beyond Unboxing! The installation of the unit itself will be covered separately as the Summer of Ven progresses.

Beyond Unboxing: Inside a Very Chinesium Mini MIG Welder

Welcome to another episode of Beyond Unboxing, where Charles buys something almost solely for satisfying his morbid curiosity. Generally, it’s something made of pure Chinesium (except last time) that I’m trying to press into service for something completely unintended, and I’m more interested in a part inside rather than the thing itself.

This time, it’s a little different. What Big Chuck’s Auto Body Center has been missing for the work I want to do in it has been a welder so I can start doing some sheet metal repair on the van fleet in earnest. I began seriously shopping around a few weeks ago for a MIG welder, which would pretty much handle everything I would typically weld. It would have to be at least somewhat shitty, since we paid top investors’ dollar for the company welders, but just not shitty enough such that it makes me want to “borrow” them periodically.

At first I was just considering a used Miller or Lincoln unit with dual voltage input since Big Chuck’s Auto doesn’t have any 240V or 3 phase – I only have 120. Hella butts 120 (several independent 50 amp circuits fed by what looks like a 200 amp breaker) but still only 120, and most welders will power limit automatically. Buying a giant step-up transformer was, of course, one workaround which I didn’t want to consider, and buying a dual-voltage one would also be expandable for any future shops I spider-hole in. Recent vintage ones will usually go for somewhere in the upper hundreds to low thousands, and usually quickly since they’re desirable. But wait….

Hold up, trap. This is me we are talking about here. I’m the king of spending more money and putting more effort into finding a suboptimal solution than just spending money on something that works. Just ask my van fleet and all my robots! Anyways, just buying a welder which actually works has no hack value. I came to this startling realization and decided I needed to do me: Go explore the horrible Chinesium product market and see what the bazaar of the world has to offer me for very low dollar. After all, I could just borrow the company MIG welder for a day and….

So! I spent an evening reading up and studying about Shitty Chinese MIG welders. Heaven forbid I put this much effort into actually studying something that’s useful for society, right? Here’s what I learned!

The Chinesium welder market is generally split up into 3 Gaussian bands for pricing. On the very bottom shelf, you have stuff like this…


These things are usually not even MIG, just flux-core only with no gas handling ability. They also don’t have discretely adjustable output power like a knob or setting keys, but just have 2 big switches which rearrange taps on an internal transformer to get you 4 vaguely different voltage and current settings. I’ve used the Harbor Freight Special of this kind before, and they do work with some getting used to, but this wasn’t even worth looking at for me honestly. No, not even the cheesy handheld welding screen was worth it.

Up around the $250 range, you start to get actual adjustability and gas handling, though some are still flux-core only……… but you have to read the description to find out! The torches are still usually hardwired in (this is where I learned the difference between the various welder output connector systems like Tweco style or “Euro” style torch fittings) – guess there’s not money in that product dev budget for a nice chunk of leaded brass.

For this price and less you begin to see the “inverter” based ones – cheaper ones if you just search Inverter Welder will be stick only or a combo stick/TIG machine. These are actually pretty cool in my mind, just I don’t have a use case for them. MIG needs a wire feed system so it’s usually pricier.

And getting close to the “Please buy a used brand-name machine” price range is when you’ll see the whole feature set of inverter machines with adjustable voltage/current/wire speed, gas handling, removable torch, and the like.

I decided to play a game and find the least expensive machine which had:

  • Knob- or button-dialed variable voltage and wire speed
  • Removable torch
  • Inverter-based
  • Dual voltage advertised, or at least I suspected could be dual voltage capable.

This last part is important, because I had a sneaking suspicion that these Chinese inverter welders were stupid enough that they would run on 120V even if advertised for 240V.  A lot of inverter machines were being advertised as 220/240V only – which was weird, since the way I know these things should be working, it doesn’t matter. Perhaps the Value Engineering had really made their power supplies dedicated to one voltage or another, or perhaps they are just seeking different markets. Either way, we fast forward ….

…A few days! What? It turns out that this thing is actually Fulfilled By Amazon. Thanks, Jeff Bezos! I was expecting to continue haunting the market for another 2 weeks or so while gently regretting not just getting a usable machine off Facenet Marketplace.

So this here is a “REBOOT” branded … box of something. There’s a crude lineart of a dude welding something – or perhaps shooting his death ray at something. It says Good Quality on it. You know, much like my LED headlights say ‘DOT” on them, writing Good Quality on the box doesn’t make it necessarily true. But, optimism shall prevail!

As of this writing, you can find this thing on eBay for $237.50 with FREE! shipping, which for a box this size is a nontrivial value.

So I’m gonna scoop my own Beyond Unboxing real quick. I actually got this thing so fast that I didn’t prepare anything else, and I was already at Harbor Freight for a company run and decided to unpack it to see if I could get any accessories that fit it right away.

This thing is… deceptively small. The company welders are all pretty beefy, and before that, the machines I’d have access to were not inverter units – they were older transformer ones. It’s in fact so small it can only take the 1kg wire spool size. It’s a very easy one hand lift. Definitely color me surprised and somewhat dubious it contained anything of value.

Alright, and we are on the operating table. This is the contents of the box. The unit itself, a ground clamp, a stick electrode holder, a length of PVC gas hose, and a 1kg spool of mystery meat flux-core wire to get you started. They really know their audience! Free consumable since you probably designed the thing to last as long as the spool does for the guy who buys this and welds 1 thing.

Let’s begin shucking this clam. First and foremost, let’s get this out of the way: Every cable on this – ground wire, torch output, and power cord – is copper coated aluminum wire.

I’m sure it was invented with the best of intentions. It’s light weight, it’s softer and easier to work, and it makes better use of copper conductors at high frequencies because of the skin effect.

Oh, and it’s cheaper. Did I mention it’s cheaper?

For the same gauge, make sure you realize you’re only getting 2/3rds the conductivity. When buying any questionable pedigree wire product, always take a cross section sample and ensure it isn’t bright silver colored, and strip a section and scrape the top few strands with a knife facing backwards. If it also feels too light to be made of metal, it’s probably CCA.

Basically every car audio product you buy on Amazon will use CCA wire to mimic the same gauge copper. This is just fine and dandy if you buy things by nameplate power and never, ever actually need all of the rated amps of a copper wire of the same size.  Listen to the man whose company product dynamometer results were thrown off 30% because we just threw the 4AWG audio cable we wired robots up with at the damn thing and actually tried to push 250 amps through it.

Anyways, I’m sure it works fine for the limited duty cycles and shorter runs (because these included cables and torch parts are NOT the whole 10-12 feet you’d get otherwise!). This is the rant of someone that is very butthurt and traumatized by one specific issue. I literally just finished yelling at a vendor recently for using car audio cable on some custom battery packs I commissioned because they came through silver – fortunately, after a lot more examination, they were just tinned well. I like my wire brown.


The drive mechanism is pretty generic, with fiber-filled plastic everywhere. I was hoping for a stamped metal or at least cast unobtanium drive system, but even low end brand name units have plastic wire feeds now.

What peeved me more was that this torch was hard-wired after all. The huge strain relief grommet made it LOOK like it had a Euro style connector on the output; but alas, it was just hiding the truth.

We’re off to such a good start with this one! Oh boy, this means it will be amazing.

I do have some good news – the Harbor Freight Vulcan series of MIG welder parts, such as contact tips and gas nozzles, do fit this torch. I figured the Law of Chinese Product Packaging Inertia would make this the case.

On the left is what it came with, and on the right are the Vulcan parts.

The gas hose is an 8mm push fitting; no 1/4 NPT here!

I took apart the drive mechanism to see if it would be plausible to convert the thing to a connector (so I can eventually attach an aluminum-dispensing spool gun on it) – not really, all of the cables and gas hose actually just disappear into the bowels. The cable sleeve is pretty much just a bike brake cable sheath.

My goal with taking the lid off was to investigate if there was any plausible reason why it couldn’t run on 120V. It woke up when I plugged it in, but I didn’t install any wire or try to weld anything. Besides, I was curious of what kind of Value Engineering had gone into the other parts. The case removal is easy – just undo all of the sheet metal screws.

There’s two more hidden under the handle too.

And here’s one side of the goods! The drive unit is a little speed-400 type motor, but higher voltage, feeding into a spur gearbox. This thing looked to be an OEM part of some sort you could buy – it’s genericized on eBay and other places as “24V wire feed motor”. The controls are up top, and the big money power is on the bottom.

All of the boards had this name written on them. Arcsonic seems to be the actual brand name/OEM of this unit, along with many others that look like it. I’m glad it was this straightforward!

This smaller board is the rectifier assembly. Just a bridge and some capacitors here, no fancy power factor correction.

The back side of the board – the relay is the gate for AC power to enter the rectifier and DC bus.

The part of this thing that can be called the “Inverter”, I suppose. Most of the time when welders say “inverter based” they mean this kind of buck converter architecture .  In this thing, the rectified AC mains power enters on the left side. It then gets chopped by the IGBTs under the left hand heat sinks to yield a lower voltage. It’s the same topology as almost every motor controller. The large donut on the right is an output inductor to smooth the current ripple.

Actually, looking at the backside of this thing, it’s more properly called a half-bridge forward converter. There is an isolation transformer in the middle between the input and output to step the voltage down in lieu of modulating the duty cycle across a wide range. The exact mechanics of what a half-bridge converter is are beyond scope here, just accept that it made me go “oh, neat” and can be highly efficient.


The control board is almost all discrete and thru-hole components. This design must date back quite aways – not being a welding historian, I can only guess it’s lifted from a 90s to 2000s era inverter welder of American or European bloodline. I wasn’t interested in diving into what it did here – pretty much just scanning what the logic power supply looked like.

At this point I was convinced that it might be stupid enough that I can just run it on 120V without issues, perhaps just taking a hit on the maximum output voltage. That’s mostly why I was staring at the power stage, since some architectures will prevent the duty cycle from changing enough to accommodate a 50% reduction in bus voltage; if not, it could be smart enough to error out of it detects a duty cycle increase above a certain limit. The design of the half-bridge forward converter is such that it’s pretty input voltage agnostic as long as your driver circuitry keeps working.

I began putting the thing back together and briefly wondered why a MIG welder would have both a volts and an amps knob – before remembering this thing can also do stick welding. In MIG mode, as I tested, the Amps knob just controls wire feed speed.

Continuing the reassembly! The torch is really, really hardwired in – if I wanted to smack a Euro fitting on it or something, I’d have to deconstruct that whole signal wiring harness to disconnect it from the control board. Not worth it, really. If you wanted expandability into the Chinesium aftermarket, this is probably not your unit – I also didn’t see any easy way to cut a spool gun into the control system. I suggest, you know, buying a real welder.

I decided to go ahead and arm up the mystery meat flux-core spool  and actually get some welding done.

So, Big Chuck’s Auto Body came with something I call “Frank, the I-beam”. It’s a 16″ tall structural beam that used to be 24 feet long. Just an entire I-beam, hanging out and squatting on the floor eating all your leftovers and smoking all your weed, the underachiever. Early on, I hoisted it onto a set of 4 car dollies so I could at least shove it into a corner. I later asked some friends to come over and have at it with torches and cutoff saws – they took most of it to make things like anvils and…. gantry cranes? I didn’t really ask too much.

Anyways, I kept 6 feet of it for… whenever I need an I-beam, or something. Right now, it’ll be welding practice. I was going to crank this thing up all the way and just deposit steel.

Well, I definitely own a steel ball spraying machine.

My history with flux-core welding has been very spotty. I’ve usually just been handed a machine in some field/competition/informal gathering and told to fix this or that, and it was filled up with flux-core wire because no gas or infrastructure to support it and no willpower to change that.

It’s always just made a mess and been horrible, and I always wrote flux-core off as a trashy third-tier welding process.

It turns out, you need to use Electrode Negative mode with it, or “straight polarity” welding. First, that’s a welding industry legacy term, because to everyone else, “straight” or “positive” polarity means something with positive voltage is touching it. Who the fuck knew!?

I sure didn’t – since I avoided the process like I avoid college town liberalism, i.e. once and never again, I never did research into it enough to find out that LITERALLY EVERYONE WHO HAS HAD ME TRY TO USE A FLUX CORE WELDER HAS BEEN WRONG.  You don’t just insert flux-core wire into a MIG welder and start firing away – well, you can, but it would make more little steel balls than weld.

This thing lets you switch the polarity of the torch and the return clamp manually. A more sophisticated machine might have a big ol’ switch on it to do so. Either way, by searching “why is my flux core welder shitty and raining steel balls everywhere” I learned a thing.

Yep, so that vertical line on the right is the first decent looking bead I’ve ever made using flux-core wire.

In my entire life.

You know, past the toxic cloud of flux vaping upwards at me, and the need to constantly wire brush and clean up your weld, it’s actually not bad! I see that, much like people fool themselves into liking India Pale Ales, people also fool themselves into liking flux-core welding. I made several more fine-ass looking beads after this, too.

So, the verdict? I had the machine cranked out to the max on both voltage and wire feed during these tests, and it handled that admirably. It’s obviously not pushing enough power on 120V input to hurt itself, nor to trip a convention 15A breaker. I deposited steel (welding implies it was usefully joining metals) for about 30 seconds straight crossing the entire I-beam width – that was a nasty looking slug by the end – and the machine didn’t throw any angry lights or stop running. In the near future I do want to drag it over to the new shop and try putting an Overhaul wedge together using 240V mains, and see if it wants to go back on vacation.

In the end, this “220V” Chinesium inverter MIG is proving itself quite handy on 120V. Luckily, it won’t be principally welding I-beams together in Big Chuck’s Auto Body. Instead…