Cheap Chainsaw Teardown Reveals Buried Treasures

People seem to have a love-hate relationship with Harbor Freight, and it mostly seems that they love to hate the purveyor of discount tools. This is not without cause — any number of HF tools have fallen apart in our hands. But there are some gems to be found amid the dregs and dross of your local branch of the 700-store US chain, as long as you match the tool to your needs and manage your expectations.

Now, we’d normally shy away from any electric chainsaw, especially a cordless saw, and doubly so a Harbor Freight special. But as [Professor Charles] demonstrates with his detailed and humorous teardown, the Lynxx 40-volt cordless 14″ chainsaw might be worth picking up just for harvesting parts. First there’s the battery pack, which is chock full of 18650 lithium cells. [Professor Charles] leads us on a detailed tour of the design compromises of the battery and charger and is none too impressed with either, but he clearly understands what it means to build to a price point. While [Charles] found the stock motor controller somewhat anemic, the real buried treasure in the tool is a huge brushless motor, powerful enough to “throw an 8-inch Vise Grip at you” during a (not so) locked rotor test.

The whole teardown is enlightening as to the engineering decisions that go into mass-market tools, so even if you can’t think of something to do with this motor, the article is worth a read. At $169 for the Lynxx (before the 20% coupon in your Sunday paper every week) it’s a little pricey to buy just to harvest parts, but it wouldn’t be the first HF tool to suffer that fate. We’ll bet these things will start showing up broken on the secondary market for a song, and if the [Professor]’s assessments are right, it likely won’t be the motors that fail.

104 thoughts on “Cheap Chainsaw Teardown Reveals Buried Treasures

          1. Yeah you totally could. Usually the new-price of a tool isn’t worth the parts cost for equivalent functionality of an industrial/commercial part. Secondhand/junked though…

            Plus, the point of the BU articles is to get peoples’ gears turning about seeing parts in everything around them, not necessarily because something is the best value.

  1. I once bought a chainsaw shapening machine that s it turns out was made from plastic, as a result it wasn’t overly constant or accurate, but as it turns out had an excellent motor that held a grinding stone, (think 4″cutting disk but stone) that was used to replace the dremel multitool! I my sawmill sharpener, so all in all not a bad outcome, but not acheap one either.

    1. Because you are a small consumer of power and large industry will continue to require large amounts of power and will have an edge on dictating the style of power transmission.
      Because that toaster oven you cook your pizza pockets in for dinner can’t heat up with led light, nor will your electric dryer.

          1. Saw a news item linked that said the Dutch are phasing out natural gas for the home, and want to disconnect all homes from it in time.
            They want to connect homes to waste heat installations for warmth I understand. Seems a rather costly and complex and big undertaking though.

          2. @Iwatcdr:
            But that would not make sense – to convert CO2 and H2O (+energy) to methane only to burn it back to CO2 and H2O and heat. It is more efficient to run the dryer directly with the electricity. Preferably with a heat pump system like my dryer.
            Of course, if you have suitable biomass, this would be an option.

          3. The problem with bio methane/methanol is that feedstocks are too cheap (i,e. any kind of biological waste) so no lobby behind it, due to that, profit minimal, when you can be price warred out of business by fossil methane i.e. natural gas supplied by your friendly neighbourhood oil co… It’s practically a waste product of oil recovery, they burn it off when it’s uneconomical to transport to nearest population centers, it really only has value as an object of exploitation in and of itself when it’s reasonably near large populations, like north sea gas is/was…. otherwise it’s 99% transportation cost…. every “natural gas shortage” has been a distribution issue so far, rather than there’s not enough available at various well heads.

            Anyway, the instant that the very last cubic foot of fossil gas is out of the ground, bio methane and methanol are economically viable, but not before… unless an otherwise rich govt with zero petrochemical resources declares war, builds a bio-methane industry that can bankrupt oil companies with race to bottom and cheap product.

            Possibly carbon taxes could level the playing field enough, since bio methane and methanol are carbon neutral. I think actually they are greenhouse negative, because bio wastes may emit methane anyway, collected or not, so avoiding direct methane release is beneficial, since it’s that much more powerful a greenhouse gas than carbon dioxide.

            However, we don’t really have an energy crisis, we have a “the wrong people have the money and the power” crisis, which is an obstacle to progress.

            What we end up with is white elephants like an ethanol industry which in comparison needs relatively high quality specific feedstocks that are profitable to farmers, and hence farmers waste high quality land on ethanol crops, and lobby for ethanol, as do their representatives.

            The problem for a grassroots roll your own methane movement, is that average household doesn’t really have enough bio-waste to produce significantly useful amounts of methane, you need something more like a small farm or homestead to get the scale. I mean if they delivered a sack of shit as your share of what it took to make the quarter of a cow in your freezer, and a bale of straw for your bag of flour, then yah, suburban methane would be a go.

          4. the nano second we run out of fossil gas you can bet your left one that landfill methane extraction will be a “big thing”!
            there is/was a mob here in Adelaide that were/are extracting methane from the infamous Wingfill dump.
            They had these huge spark ignition engines running generators, those things were huge!

            bio fuel agriculture is set to be the next big battle front when it comes to greenhouse gasses, it is happening already.
            you can’t blame farmers for wanting a quick “cash crop”, just like friggen poppies here, but pasture that should not be turned and scrub that should not be cleared is, right now, for a quick quid.

        1. It’s more efficient, more cost-effective and easier to distribute electrical power as AC, and electrical heat is going to be with us for a long while yet… so AC to the house will still be the norm. You might see some sort of new DC branch type for all-LED lighting. Even so, low voltage DC in the home will still likely require the same or heavier wire than the 14 AWG AC wiring that most houses currently have.

          1. Well you could tun AC into DC near the home I suppose.
            And I’m sure the army and such have outposts running on DC, at least they did in the old days I think, but I’m not sure.

      1. Regarding the toaster, Vrms is used to compute a power equivalence to DC power.

        Power = (Vrms * Irms) * Cos thetha
        Power = Vdc * Idc.

        The crinkly wire doesn’t care.

        Gov’t will keep on increasing efficiency requirements of appliances to the point where BLDC will be the only way to achieve compliance.

        I’d expect to see CEC lead this in the US.

        Sort of like how PFC is a fact of life for CE market destined products.

      2. DC works fine in ovens and in incandescent light bulbs.
        The reason that we still have AC is because AC was the best at long distance transmission, AC transformers made changing voltage much simpler. And we still have a lot of good old fashioned AC motors around. BLDC motors have only just become commonplace and Frankly I do not want to replace every AC device I have in my home. The 1972 Hamilton Beach Juicer I have works just fine and dandy thank you.

        1. Your juicer is probably no induction motor, but a universal motor. Being from 1972 it probably has no TRIAC control so it should be happy with DC.
          But of course 3 phase AC is more efficient in distribution and the big 50Hz power transformers are really efficient and probably more reliable than any semiconductor based equipment.

    2. Because you get power from an AC power grid.
      A number of companies are developing LED fixtures that don’t convert to DC, stringing the LEDs in a bridge configuration so they get powered by AC directly. Granted it takes 2x the LEDs to accomplish, but you’re not taking an efficiency hit in your electric bill from the rectifier.

        1. Florescent and incandescent lights flicker too – at 120 times a second. It’s less obvious with incandescent because they dim slightly instead of turning completely off. Increase the frequency of the DC chopper running LEDs and you won’t notice them either.

          1. the OP talking about using the LEDs as the bridge rectifier. There is no DC chopper, just 120HZ drive frequency from the AC. Or 100Hz depending on what part of the world you’re in. That would also mean that it’s less likely you could mix bulbs meant for different power grids given the drive voltages.

    3. Also,
      Because dc, when dealing with any amount of significant currency, is far more dangerous and difficult to deal with than ac. The average person can barely unplug a cord properly, why in the world would you ever think it a good idea to put something in their house that cause them to have to think.
      Yes, I know, they make dc appliances and so on and so forth for people in rvs and off grid applications, but usually those people are invested into what they are doing and therefore are somewhat willing to educate themselves on what they own.
      As a 20 year service work and remodel tradesman I feel I can say with a fair amount of authority that most homeowners don’t have a freaking clue about how things work in their house, nor do they care, therefore should not be trusted with large current dc distributed in their house. It’s to dangerous

      1. How much licensing is required for a low voltage wire puller vs a licensed electrician? How about a burg installer? CCTV / Fire alarm?

        To avoid hiring tradesmen for installing lighting in commercial buildings, there is a move towards using higher power, but still Class 2 PoE for LED light fixtures instead of the usual 277VAC single phase (1 leg of a 480VAC 3 phase branch circuit.)

        Now the same people who pull network cable in the plenum area can perform lighting installation.

        This is a real thing.

        BLDC motors are more efficient therefore smaller than simple AC split, cap start motors.

        One day we might wind up with smart outlets that servo their voltage to what ever is plugged in, think USB-C 3.1 for regular useage. USB-C 3.1 is really useful for charging because by upping the voltage you can still use tiny 28AWG wires to overcome voltage drop.

        Everything low voltage means no shock hazard. The higher currents are the real issue for DC since DC tends to weld short circuits.

        Think long term, people!

        1. It’s not a matter of long term thinking, it’s a matter of safety.
          Most dc circuits in a house (unless integrated into a manufactured listed product) are a class 2 circuit and are therefore limited to 100va of power.
          Heat up your pizza pocket with that.
          All dc run through a house regardless of voltage for solar panels needs to be run through metal conduit regardless of protection before it enters the home because it’s dangerous.
          When purchasing disconnects that can safely disconnect dc power they are much more oversized then their ac counterparts.
          Yay, you have a natural gas dryer, good for you. You probably hear your home by it too. Some areas in the US use electric heat for third homes.. Yes elements can heat with dc or ac but good luck heating your home at night in 0 degree weather with your tesla battery bank charged by your 30 panels stacked on your roof buried under 10″ of snow.
          DC transmission will never be a solution.

        2. There is a direct relationship between voltage current and power, and this relationship has nothing to do with AC or DC.

          100 Watts = 1 Amp X 100 Volts
          100 Watts = 10 Amps X 10 Volts
          100 Watts = 100 Amps X 1 Volt

          Regardless it’s the same wattage and the same available power. And since AC / DC does not matter you could run 120V DC on the same wire size as AC providing you were drawing the same current.

          But there are real issues with higher voltage DC.

          The first is safety – touch a ‘live’ 120VAC power source and you can let go. This is because the AC power is actually off 120 times a second and your muscles have a chance to do what your brain wants them to do 120 times a second. But grab onto 120VDC and your muscles will lock up tight. You won’t be able to let go, you will be cooking like a giant hot dog on a Presto Hotdog Cooker.

          The second issue is technology, and there are several issues here.

          The first is switching power on and off. Even with relays, switching higher voltage DC power off draws a huge arc compared to switching AC off. AC/DC rated relays are DC rated at 1/10 the AC current for this reason.

          The second is larger DC motors are very inefficient and noisy – they require large brushes and commutators to transfer DC power to the armature. In contrast, as AC shaded pole motor is one of the most efficient designs around. The only issue AC shaded pole motors have is they are constant speed, which is the real reason BLDC motors were designed. BLDC motor design has nothing to do with efficiency.

          The third is voltage conversion. With AC it’s easy – you convert with a step up or step down transformer. With DC every voltage conversion will require some sort of active power supply.

          The forth if you really do decide to do low voltage DC is wire sizes. A typical house in the USA has a 240V 200 Amp service for a potential peak power of 48,000 Watts. If you want the same 48,000 Watts available at “safe” 48VDC you are looking at a 1000 Amp service. This would require 5X the wire size and approximately 5X the buss bar size inside your electrical panel! And instead of wiring your 120V outlets with 12 gauge wire you’d be wiring your 48V outlets with something not much smaller than your little finger. Then there’s the outlets themselves, and the power cords to your appliances…. Everything would need to be 5X larger!

          1. Actually 120Hz AC is very good at commanding your muscles tight shut. Your nervous system works with pulses. But DC could do electrolysis in your body, which is very dangerous in its own.

            Shaded Pole motors are between the most INefficient designs. That’s the reason, they are only built for small power. They have only one advantage: They are cheap to manufacture. Any – brushed or not – DC motor is way more efficient.
            A real 3 phase induction motor is quite efficient, if you want to top it, you need probably the BLDC.

          2. As far as voltage conversion, active electronics are now cheaper than transformers, that’s why every PSU now is switch-mode. The electronics mean you can use a much smaller transformer, and it makes the difference. Not for power distribution, but in the home certainly.

        3. “How much licensing is required for a low voltage wire puller vs a licensed electrician? How about a burg installer? CCTV / Fire alarm?”

          5 years, the same as a regular electrician, only the regular electrician can do low voltage too.

        4. The electric network in my home has to be reliable at first priority. There is no room for too much “smartness”. I can still plug any smart charger in any normal 230V/50Hz socket – and I can unplug it, if it needs a reset. Like these radio controlled sockets. Sometimes it does not switch off properly (or if the battery of the remote is down) and I can just pull it from the socket.

    4. My scariest thought on DC is how an arc will not self-extinguish, and if you want to run it <50 V for shock safety, bigger appliances need relatively high current and bigger conductors and switching capabilities.

    5. Because that electricity has to get to your house somehow, and AC means you can use cheap transformers instead of expensive DC-DC converters to go between transmission, distribution, and line voltage.

      HVDC is great for long-run transmission, and for inter-grid links, but until recently, the electronic DC-AC converters used at the end of these would only feed into a live AC grid — if you tried to feed a step-down transformer with a rectifier (and DC grid) on the secondary, they wouldn’t have worked. Now they’re switching to VSC, there’s more flexibility there. Basically, these converters are three-phase variable speed motor drives, like you find in most CNC machines, only with ludicrous current and voltage specs.

      Even so, you don’t want to step straight from transmission to line voltage — you need to drop to a lower voltage for distribution, and then to line voltage only on the last leg (pole->building). So if you replace all transmission lines with HVDC, and run the distribution lines on DC as well, you still need additional DC/DC converters on the pole outside every building, to replace the transformers currently used — it’s cheaper to run distribution, at least, on AC, and just put a rectifier on the existing transformers to provide DC to the home, and cheaper yet to keep feeding homes AC, and install hybrid fuseboxes in new homes that include an efficient AC-DC unit, and provide for circuit breakers on both AC (for major appliances) and one or a few DC rails (for LED lighting, computers, etc.)

          1. Yes, and right now I save a fair percentage of my summer power bill because I allow the utility to turn off my air conditioner as they need to for load shedding.
            Power grid load shedding is probably one of the best ways as a community we can help “save the environment”.
            Even if your “powered by nuclear” because if you save energy that potentially allows your clean producing plant to sell power to reduce coal plant power production elsewhere.

          2. @evad:
            That’s the reason I am against this.

            @Alfiesauce: I switch on the AC only if it is necessary. So there is no reason I want anybody else to switch it off (or on). The utility poeple do not know my room temperature or how I feel hot or not.

          3. Sure the power company don’t know how hot your room is (though the weather report gives them a fair idea). But if they’re willing to part with a fair chunk of money if you’ll let them turn your AC off, it might be a deal worth taking. Ultimately they want the AC on most of the time, since that’s what their business is, selling electricity. But help them out, and they help your bank account. Sounds tolerable.

        1. I’ve seen a few that were trying to live off grid and went with 12v DC. The wall plugs were basically the same as the plugs in a car. They bought small electric appliances like a long haul trucker would have in the sleeper area of his truck. That was years ago though…. pre smart phone era, possibly pre mobile phone era,

      1. Imagine for a minute if you didn’t need to use a similar distribution infrastructure, or didn’t need one that travelled for such a long distance.

        How much energy does each AC inverter waste for all of the roof top PV systems that put energy back into the grid?

        How much energy is wasted just synchronizing AC?

        How would a DC system handle these problems?

    6. Serious electrical engineer working in the field answer:
      The problem is protection of DC components. AC has a natural zero crossing, you don’t have to interrupt the “full” fault current, it’ll eventually go to zero on its own. DC on the other hand will increase exponentially to the limits of your system, and you will have to break a fault after 1k’s of amps. It’s also difficult/impossible to tell the difference between a failure and capacitive inrush.

      Power electronics at every single interruption point (I.e. every breaker, possibly every outlet) can eventually solve that problem. It just requires them getting even smaller, cheaper and more efficient (which is happening). However, that same technology applied to an AC system can increase reliability and efficiency.

      It’s difficult to see where the market force will go over 20 years. It’s very clear DC distribution will pick up in niche applications (server farms / data centers, long-distance transportation). It’s not so clear it’ll catch on at the local utility and in the home.

      1. P.S. The original comment mentions BLDCs, LED lighting, etc. Although these items run off of “DC”, they still need power electronics to function. Since you’re already converting power. There’s not much difference for these items operating off of AC over DC, as you have to condition the input either way.

        1. Yes, that’s the real point. Nobody wants to run LEDs (of different power) with resistive droppers from a DC mains. And if you use a DC/DC converter, the mains rectifier diodes are probably the cheapest part of it.

      2. I think AC has a *lot* of momentum. My own off-grid setup is 12VDC PV panels wired in series/parallel strings to give a nominal voltage of 24VDC, heavy gauge DC cable straight into 1320ah of lead-acid cells, then an unregulated 24VDC circuit for lighting and power (24 volt refrigerator), and another heavy gauge run to a sine-wave inverter, then a 240VAC circuit for general purpose household appliances. In short, a hybrid system that’s served me pretty well for 20+ years (although I’m on my second set of batteries).

        New grid-tie systems are *all* AC. Microinverters on each PV panel supply AC to the grid-tie inverter, which supplies household circuits, and sends the surplus to the grid, or draws from the grid when demand exceeds supply. A battery charger extracts energy to charge a Tesla or LGChem battery to feed the inverter at night/cloudy days.

        I haven’t yet figured out why it’s preferred to convert to AC at the PV panel, then back to DC for battery charging, for some reason the latest crop of installers all think it’s better to have AC as soon as possible in the chain, then rectify to DC when needed. I like my hybrid system – if the inverter goes faulty, I still have lighting and refrigeration while I have it fixed.

          1. You could use higher voltage DC instead. Would be curious how using highest voltage DC you can run at the same level of protection as mains AC voltages compares to generating AC (and needing inverters etc).

          2. @Admiralranga:
            That’s the way my father’s solar system is built. A quite thin (OK, little thicker insulation than normal mains wire) 600V/8A line from the panels to the inverter and then 3 phase to the meter box. Of course if you had a shading problem (obstacles nearby) a micro inverter solution could be superior. But otherwise I prefer one big device, were it is economically viable to build it to good efficiency. You also need to power only one microcontroller, network interface, display, etc. And the inverter is better protected from the elements than on the rooftop.

        1. I think one of the main reasons for micro inverters has historically been, at least in Minnesota, the way solar credits are set up. The utilities are requiring a production meter on your system so even if you want a battery based system of some kind or another you still need to push your pv production through a standard utility meter before you can use it.
          I’ve actually wired a couple outback battery back up systems this way and just shake my head at the amount of loss incurred due to the inverter -> rectify -> store -> invert again…
          Thankfully there are people pushing for reform in this regard because it’s ridiculous.
          Another reason for micro inverters is the ability to not having to have a perfect location- micro inverter systems can still produce well under partial shading conditions. However solar edge has been able to substantially move single inverter systems into thus area very well with their dc optimizers.
          The last couple nec code cycles have really been unfriendly to single inverter systems as well as manufactures grapple with issues like remote dc rapid shut down.

      3. I see this more of a Fahrenheit 451 sort of way, where everything in the house is already fire proofed.

        The branch circuits in the house default to SELV circuits until the individually plugged in device requests more power. This would limit shock hazards etc., by default.

        Regarding appliances, 100Watts is a lot of heat. Technically a “power limited” circuit is also limited to 8 Amps within 5 seconds.

        BLDC’s are smaller and generate less heat (operate more efficiently when generating the same amount of work)

        Not sure if the following link will get clipped out.

    7. Because AC will still remain the only truly economical method of electric distribution. Which is why it won the “war of the currents” in the first place. DC distribution has real problems that AC does not.

    8. Because AC is better suited for distributing electrical power via the grid. AC motors are simpler, they just work with no additional electronic circuity. LED lighting is a poor choice to make your point. While for basic LED lighting applications the electric circuitry is simpler and less expensive. While the advertising wank claims superiority because of the power source this tool is designed to be throwaway tool for it’s targeted consumer just like ICE throwaway chain saw are. Sure some DIY types will eke out a few more cuts out of either tool before the tool is tossed to the junk box before they purchase a new tool, they are the consumer. exceptions not the rule.

    9. 1. Long-distance transmission of electricity requires high voltage to reduce current. We need to reduce current to decrease losses. At least until we get room-temperature superconductors practical for electricity transmission. High power transformers for increasing AC voltage are probably cheaper than DC/DC converters handling equal power.
      2. Cost of switching to completely new standard.

          1. In power transmission, it’s high current that’s the problem, and causes waste heat. The answer is high voltage. The same for AC or DC.

            Of course there’s other differences between AC and DC, but losses in wires isn’t one of them. A lot of modern super-high-voltage super-high-power transmission lines are DC. It’s also easier to connect systems between 2 countries or areas, you don’t have to mess about keeping their cycles in sync.

  2. $169 instead of buying $20 motor directly from alibaba … Some people are truly delusional. Reminds me of Dave(eevblog) having a stroke at a thought Chinese are able to make something useful for $5 while he spends more for a post stamp in the most overpriced desert island in the world.

          1. With China it’s likely they don’t know what “brushed” means, and think it means “good” because lots of other motors have it. Or “brushless”, either way. Some company on Ebay were selling a single, one-ear, Bluetooth earpiece that was apparently stereo. I asked them, and in very poor Googlish they said “stereo means can play music”.

      1. I would be happy to write a separate article with my own outlandish ideas on where I see this going and why.

        The future is going to be an interesting place.

        Appliances are designed to suit what power source is available.

        What power source is available is driven by economics as compared to other power means.

    1. lol

      in the rest of the world, not ‘Murica, we have “Consumer Protection Laws” and “Occ Health an Safety Laws” that stop crap like this entering the country BEFORE we get hurt, maimed, crippled or killed!

      Don’t get me wrong, I hate the “nanny state” with a fiery passion, but here in Oz crap products don’t make it through customs…

      1. Here you can get even cheap chainsaws with gas-motor or mains operation for 100,- in a supermarket. But in my garden with some woods it would be nice as the gasoline version is too noisy on weekends and the generator to supply a 230V version also. The solar inverter has only 200W – this is not enough for a chainsaw :-)
        I think I could by this over ebay, but with ridiculously high shipping costs from USA. Although it comes from China :-)

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