So I’m biking home last night, I happened to roll up at the lights next to someone on a new and shiny Harley. Holy crap, it looks like it’s about to fall apart. Are they really supposed to shake that much while they’re just idling?

Okay, we all know they’ve got crap silencers, but that’s so people will think the rider is a bad-arse, not an accountant having a mid-life crisis. But really, would it be that hard to put a balance shaft on it? Or maybe even a two-pin crankshaft?

Okay, the crap engineering is deliberate, it’s a statement of style. Unfortunately, that style says:
“I don’t know anything about engineering and I don’t care”
and
“I want a bike that looks comfortable but isn’t. Also, I want to remove my own fillings without going to the dentist.”

In which case, why get a motorbike at all? Why not take up needlework instead?

Also, valves actuated by push-rods? This is the Twenty-First century. We don’t use magnetos or starting handles and we don’t use push-rods either.

17 thoughts on “

  1. I admit I’m kind of embarrassed by how loud the MX5 I’m driving is. A previous owner (not me) seems to have removed all the muffling for more of that free-flowing exhaust action.

    I take a (very small) amount of comfort that at least it was done to help performance rather than just adding a ‘resonator tip’ or some such silly thing.

    1. I think it’s perfectly acceptable for a machine to make lots of noise, if it’s bending time and space.

      However, if someone’s trundling along in traffic at 50 km/h, surrounded by people doing exactly the same thing, for that person to try to point out their individuality by having a loud exhaust is pretty ineffective.

    1. Actually no, one doesn’t.

      One monstrosity is a cool thing. Doing something to see if it can be done is justifiable and frankly, downright awesome.

      Producing them en masse and then marketing them to suckers is an entirely different proposition.

    2. In WWII, they used radial engines in tanks. I admit, a radial-engine motorcycle is pretty cool-looking and I bet it’d sound amazing. I do wonder about its cornering capability.

  2. That’s a classic case of where marketing is driving the engineering: they’re advertised as being loud (for ‘safety’) and the terrible noise and shaking is an integral part of why people buy the things.
    Likewise, pre-’78 Cessnas with upright tails were faster and more stable than the ones with the sharkfin tail, but the latter sold *much* better.

  3. 90% of it is I’m sure, marketing. People want something that’s retro and hardass. I believe that Harley have made various innovations (like toothed belt drive) on their bikes and had them soundly rejected by the market place. For what Harley engineers *can* make, look at the Buell.

    The other 10% is weight, reliability and engineering costs. Balance shafts, second cylinders, overhead cams and the like all add complication and weight (obviously the latter can be offset by using better materials). They cost money in tooling and design. They also, if not done correctly, break. Italian motorbikes are a good demonstration of this.

    Look at the Lycoming, which drives most Cessna and Piper aircraft around the sky. Incredibly crude technology, mostly from the 1930s. But very reliable and has beaten off rival motors (adapted Porsche engines and similar) for the last 50 years.

    1. Reliability & it’s Consequences

      If you’re tooling around the sky at 10,000 feet and up, you REALLY WANT reliability, and proven reliability will win over unproven reliability when your life is on the line, every time.

      The problem these days is that every thing is built down to the lowest cost rather than up to a standard, and so it breaks rather more often than it should.

      Compare the old trolleys with the newer ones (not the brand new ones). The old ones are nearly silent, the newer ones are built closer to tolerance and require noisy fans to keep the running gear cool so are noisier. (Now I know there can be an argument for making them noisier so folk hear them coming, but I’m not talking about that issue.)

      Also the old English Electric Electric Multiple Units compared to the newer Ganz-Mavag (aka Hungarian) EMUs. On the Hungarians the trailer unit is noisier than the motor unit (I believe because of the fans keeping the power conversion units cool), whereas on the English Electric EMUs the motor unit makes all the noise (because the gears in the transmission are worn, I suspect. They are 50 years old!). Thus the type of train determines which carriage I’ll sit in as I prefer the quieter ones.

      [/ramble]

      1. Re: Reliability & it’s Consequences

        Um, i don’t know about trains, but modern cars are a lot more reliable than those of 10,20 or 30 years ago. Same with electronics gear.

        These things are built by machine of course, which deliver much more repeatable results than people.

        1. Re: Reliability & it’s Consequences

          I’m not sure about the electronics gear — it depends on what it is. I have Hewlett Packard oscillators and oscilloscopes from the 1960’s that are still doing fine, and we have a 1958 Tektronix curve tracer at work that’s still chugging along, while a bunch of our late-80’s scopes are behaving very poorly, we’ve had several brand new Keithley sourcemeters die hideously, a six-month-old Agilent AC analyzer went up in a puff of smoke the other day… now of course the only electronics that are around from the ’70’s and ’80’s are the ones that are still working. But I don’t remember as many things dying as fast back then. Some current Tek scopes have name-brand PC motherboards in them. Consider me dubious.
          For that matter, my 1986 and 1990 Commodore Amigas and their matching CRT all work beautifully. I can’t tell you how many late-90’s PC’s and monitors I’ve gone through.

          But having worked on cars from every decade since 1940, I’m in *complete* agreement with the general truth of your statement.

    2. All true, but it’s not like they don’t put a huge amount of marketing into Harleys.

      As for extra complication and breakage, if done correctly, they don’t. Japanese motorbikes are a good demonstration of this. But seriously, anything vibrating that much is going to have to be overbuilt, so there’s a cost saving from not having a machine that’ll shake itself apart.

      And aero engines are a special case, where, let’s face it, an absolute requirement for reliability has hindered progress.

    1. They’ve got a heavier valve train, so there’s less valve speed, and it’s harder to do multiple valves per cylinder. So how do they reckon to more power per vol? Coz everyone else uses OHC for the same reason.

      1. I honestly don’t know: it’s just a tiny bit of data I picked up somewhere. I think their basic idea was that they were running into a limitation of oil-pan to top-of-valve-cover height in order to have the hood line where they wanted it, and the only ways to make that shorter were to flatten the V or go back to pushrods. Vettes do some weird things. They still use (transverse) leaf springs for suspension, frinstance. But I think their point was generally that the cam and pushrods are essentially free, since they’re enclosed within the V block, so all you pay for is the rocker arms, whereas with an OHC/DOHC you need cam height, which means bearings at least as large in diameter as the max cam lobe, plus bearing thickness, plus bearing end caps. In my Soob, the width of the engine to the top of the deck, is about the same as the distance from the deck up to the top of the valve cover — the block is 1/3 the width of the engine. It’s weird to pull off a head and look down in there at those little pistons waaay inside all this mass of stuff.

        I wonder how much the valve train weight matters. I don’t know, mind you — but engines tend to be piston-speed limited, and at high rpm’s soak up an *enormous* amount of power into the valve springs. I remember reading about a 14,000 rpm Cosworth engine that they estimated was putting 8% or so of its total produced energy into heating up the valve springs, meaning *enormous* oil coolers. (Similar limitations led Mercedes to develop the desmo valve train and then license it to Ducati, as I recall.) So you run into all these other problems…

        1. True, pushrod engines can be shorter, but if that’s what you’re after then lay the cylinders down. Use a V or flat engine. Or use a mid-engine layout.

          As for valve train weight, I believe that a heavier (and less stiff) train gives slower opening and closing of the values, so there’s less time in each cycle that the valve can be fully open, hence less power per unit volume.

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