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Bakfiets earns its flames!

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  • calfee20
    Originally posted by DaHose View Post
    Did I miss seeing the specific value? You said it's confirmed that vacuum lightens things up, but I didn't see a hard number. I searched for a physical constant related to vacuum and weight reduction of an object, but I can't find an exact number.

    Hmmm I get 1.285 kilograms per cubic meter. It seems high but a common sense proof confirms it. Water will expand about a thousand times when it evaporates. A liter of water is a kilogram so close enough.

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  • DaHose
    Did I miss seeing the specific value? You said it's confirmed that vacuum lightens things up, but I didn't see a hard number. I searched for a physical constant related to vacuum and weight reduction of an object, but I can't find an exact number.


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  • tklop
    commented on 's reply
    The weight reduction of a vacuum is already well known. I just said that.

  • DaHose
    What about a hybrid design? Think Russian Aeroklan, but for travelling high in the air. Maybe you could make an exoskeleton of something like graphene and create winglets or nacelles that attach to a cargo section. Could the exoskeletal structural rigidity combine with the inherent rigidity of the aerogel to support enough vacuum, such that it greatly reduces mass? Then something like solar energy might be enough to power assist engines of some kind to create the speed/lift required for flight.

    I wonder exactly how much lift is generated by a cubic meter of absolute vacuum? I think that is really the place to start.


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  • tklop
    commented on 's reply
    That is interesting. Way cool. I never heard of that.

    I enjoy SciFi --but haven't read all that much, to be honest. Not since I was a kid, reading Ray Bradbury books!

    I never read any of Edgar Rice Burroughs' stuff. The synopsis indicates it's probably not my bag. I mean--Tarzan? Seriously?

    It's neat to know I've shared a concept with the author--somebody almost a hundred years earlier!

    At the same time, it's a shame to consider that we're not already riding on these craft.

    If the idea was in place, only awaiting Aerogel--we should've been flying on these things since the year 2000.

    Last edited by tklop; 07-02-2020, 04:06 AM.

  • tklop
    commented on 's reply
    Thanks, Jose...

    Of course the logic is strong. It's mine! ;-)

    I started with the same thoughts.

    -----------------------------mullings over----------------------

    Lifting-engines are a structural displacement story. Structural displacement of the heavier air outside--by a volume of lesser dense gas--separated by a membrane--provides buoyancy.

    Since buoyancy is based upon structural displacement, I wondered--could a bell-chamber be made to levitate--if you could somehow make it light enough? Well, I looked that up. Turns out a bell-jar's weight does go down as you pump the air out. But the heavy glass dome, the metal plate, the huge vacuum pump, the wax used to seal the edges--it's all just so heavy (to withstand the forces involved) that there's no chance whatsoever of levitation for a bell jar.

    Okay. No chance a bell-jar is gonna fly.

    But a reduced-pressure area is indeed buoyant... So how could that be made use of? How can our levitating-bell-jar dream be improved upon?

    Could we make something super-lightweight--but rigid? What would it take? A shell of some kind that's strong enough to support a vacuum?

    Curved shapes are very strong. Could we ever figure out how to make some kind of hollow-egg-shaped structure rigid enough to withstand one atmosphere (14.7 psi) ?

    Instead of being completely hollow--could our egg be supported internally--with some sort of super-light high-tech network--a complex honeycomb of structural supports?

    Maybe if supported internally, that'd mean we don't really have to be thinking about how to make a bell-jar fly anymore.

    If the internal supports can prevent our egg's collapse, its shell won't have to support all the pressure. The shell won't have to be nearly as thick and strong.

    If we could get a full 15 pounds per square inch of support from our honeycomb support-structure--and if that honeycomb structure could somehow be made lighter than air--we'd have our solution!

    We'd win the displacement game with structural displacement--the same thing we used to do with hot-air or helium or hydrogen--and we'd not need a super-strong or thick shell at all. We'd just have to make sure the membrane or shell was puncture-resistant...

    But how could we get our internal structure? What could we make it out of? Do we need to invent a new kind of material? Do we have the technology to weave carbon-fibers in a helpful way? Could we synthesize spider-webs somehow? What could we possibly use for internal support?

    ---------------------------grand realizations------------------------

    And that's when it hit me--we've already got exactly the right thing for that. Aerogel.

    Aerogel obviously is somewhat resistant to compression. There's a pic of aerogel on Wiki--a 2 gm piece supporting a 2.5 kg brick. It's a porous solid--think more along the lines of pumice--as opposed to a sponge. It's a solid--and it's not squishy.

    So, what I'm describing doesn't wind up being a vacuum chamber at all.

    On the contrary--there's a large, airless chamber, supported from the inside--structurally--rigidly--by aerogel.

    Blimp? Zeppelin? Same thing. Displacement:

    There's a large, airless chamber, supported from the inside--structurally--rigidly--by helium gas.

    In both cases there's a membrane, with 14.7 psi atmosphere acting on the outside, trying to collapse the envelope. In both cases, the chamber inside is held open structurally--by a material that is lighter than the outside air.

    So this is no more a vacuum-chamber than a hot air balloon is, or a blimp. There isn't a large pressure-difference on either side of the membrane in a hot-air balloon or blimp either--only enough of a pressure-difference to provide buoyancy. That's all we're talking about here too, because the aerogel side will always have "pressure" due to Aerogel's own structural rigidity--regardless of whether or not its pores contain any air molecules.

    This makes it a lot easier than you're thinking. The membrane only has to block the pores in the aerogel. You might even be able to seal the aerogel's surface with a thin membrane of latex--maybe even layer of paint. If its coating were lightweight enough, and if you could then figure out how draw the air out--you could watch an aerogel brick float--right in your office.

    And so what if aerogel is a little-bit compressible, and it can't handle full-vacuum? Who cares? Figure out how compressible it is, and see what gains are actually attainable--and at what pressures.

    Calculations would need to be made--but this ain't rocket science.

    -----------------------how to find confirmation---------------------------------

    This might be testable with a garment-bag full of aerogel and a dyson vacuum-cleaner--because a full-vacuum wouldn't be needed to establish a baseline. You wouldn't even need buoyancy. Any measurable reduction in weight over the original envelope's weight--will give a baseline--a rate-of-lift per aerogel volume, per pressure-reduction.

    Obviously you'll be able to draw a heck of a lot of air out of it--and when you have your baseline, you can then scale your envelope to suit your lifting needs.

    That's the key starting-point obviously. Find a baseline. I haven't access to any aerogel--or any of the precision stuff to take measurements with.


    Hell, I don't have a lab. I don't even have a garage, shed or basement. Odds are decent I'll be homeless within a year. So the fun stuff is going to have to be for others to enjoy... Students, professors, engineers.

    Get that baseline though--and the data won't lie. Even if you wind up only a tiny bit lighter than air, that difference--multiplied by enough volume--will still produce buoyancy.

    Now, sure--if calculations show you'd need lifting-bags full of aerogel the size of Delaware--then the technology may still need to improve a bit first. But I don't think that's going be the case.

    So no--you don't need a "bell-jar"--any shell or membrane capable of sealing the porous surface of the aerogel from the outside atmosphere should be able to support it at or near "full-vacuum".

    That membrane could be very thin--and even slightly porous like a tire's inner-tube, because you're going to have to have an active vacuum pump regulating pressure continuously during operation anyway--for lift-control. So slow nominal losses could easily be kept up by an adequate vacuum-pump system.

    Details. I can solve any you throw at me.

    Yep. "Anti-gravity." With today's tech. No gases, no heat, nothing but valves and a vacuum pump for lift-control. Solar energy or batteries could provide totally clean propulsion. Done. Maybe I'm the first to think of this--but I kinda doubt it. But if I'm not the first--then what the heck have we been waiting for?

    For all I know--for those at the "cutting-edges" of things, this is old and boring news. I'm well aware our gov't and military are always busy with "secret tech dark projects" and the like. Maybe this is what's been allowing those giant triangular craft seen over America since the nineties--to hover silently. Those things did seem to start appearing not too long after aerogel came on the scene.

    In any case, the lighter and less compressible the aerogel version, the better. And they're constantly playing around and improving the stuff--right?

    I'm sad I can't take this idea any further, except in theory. I'd love to--but I'm nobody. Just a disabled vet on a fixed income, in supported living.

    I've no access to resources. I've no friends, no family, no backing--nothing. And I've no credentials to back myself up either--so it's unlikely anybody of any importance will ever take me or any of my ideas seriously.

    Somebody with money, friends, backing, resources--they can go test my theory. Maybe a university or two might want to try.

    But I hope they hurry up about it. Even though I know I'd never be able to afford a ride--I'd sure feel happy to see examples flying in the skies!

    Maybe I ought to go down to Leiden University and see if some bright young student wants a free thesis idea.

    If you think about it, even if used to supplement lift in heavier-than-air craft, this technology might dramatically increase efficiency. Even small reductions in ramp-weight could add up to tremendous fuel-savings.
    Last edited by tklop; 07-02-2020, 03:53 AM.

  • calfee20
    commented on 's reply
    In a very old SciFi story either HG Wells or Edgar Rice Burroughs They had an air ship that worked on this principle. The fiction part was some make believe alloy that was light but strong enough to stand the vacuum. So the ship had a bunch of tanks that had the air pumped out.

    I found the book.

  • DaHose
    That's a wild idea tklop, but I think the logic is strong. I do wonder how fragile aerogel is, because you are talking about a vacuum chamber that would be exerting tremendous force. So the key challenges that come to the top of my mind are centered around creating a vacuum container that would be durable enough to withstand the crushing forces of the atmosphere, resist puncture, and still be light enough not to add so much mass that the bouyancy of the aerogel is exceeded.


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  • tklop
    Crazy random thought utterly unrelated to the bakfiets...

    In any lighter-than-air craft, the lifting-engine, whether it is a lighter-than-air gas like hydrogen or helium, or whether it is just plain old hot air, it can be viewed in terms of displacement.

    A boat displaces water in order to float on top of it. A boat relies on the difference in pressures acting both upon the water outside the boat, and on the inside--the dry-side of its hull. The hull acts as a membrane between different densities of atmosphere--in this case, there's a whole lot of difference in density--between water and air.

    A hot air balloon can also be seen as a displacement machine.

    The balloon's fabric is the membrane this time, between the hotter, less dense, lighter air inside the balloon--and the colder, more dense air outside the balloon. The membrane prevents the two from mixing--just like in the boat--and the massive size of the envelope allows small differences in density (air density) to accumulate.

    The balloon will only rise, when its size is large enough to displace enough air--subtracting the reduced, but still-present mass of the air within its own balloon-envelope--plus enough to overcome the weight of the basket, and passengers. That balloon has to just get bigger until it wins the displacement war.

    An inflatable boat would work the same way. It'll sink to the bottom--until you put some air in it. You must displace the water--if you want that boat to float.

    So--big size, low-weight, displacement is the thing... And the function of the thinner gas/hot-air is to maintain the structural shape of the balloon's envelope--with as little mass-investment as possible...

    Okay. Now--let's have some fun:

    Aerogel--esp some of the latest versions--is actually lighter than air. But it's porous--full of air. So its own weight, plus the weight of the air in its pores means that when all is said and done, it is heavier than air. So it's weird stuff--super-duper light, but when you open the container, it doesn't all float away. Okay. Check.

    But now hold on a sec. I betcha I do know how to make Aerogel float.

    Suppose you filled a Goodyear Blimp with Aerogel--but then began pumping as much of the air out of it as you could.

    Assume you got that aerogel packed in there real good--nice and tight--right up to that 2psi or whatever it was the blimps ran at. Full--and a bit of stretch... Yeah?

    So, as you're evacuating the air--drawing it from the pores--the aerogel structurally holds the blimp's shape--prevents the envelope's becoming collapsed under the pressure of the outside air.

    Remove enough of the air from the inside of the pores of that aerogel--you'll have reduced its density below that of the outside atmosphere--and you'll have buoyancy.

    And once obtained, that buoyancy could be obviously be controlled by allowing air back in, or pumping more air out.

    Would a Goodyear Blimp be big enough? I don't know. Maybe.

    But for certain--each time a newer and lighter version of Aerogel comes along, this idea becomes more and more doable.

    Maybe it's still too heavy--the differentials attainable still too small... Maybe it'd take envelopes of absolutely titanic proportions with our current technology--I don't have the math, so I'm not sure.

    I'm aware it'd be energy-intensive to have to bring the interior pressures of massive lifting-cells all the way down to a near vacuum (29.9 inches of mercury; -14.7 psi, -1 bar etc). I think less negative pressure than that would be preferable. But who knows? Maybe with the right envelope material, that'd be possible.

    Obviously the greater the overall displacement volume, the better--and the more of a negative air-pressure obtainable on the inside--the better.

    So that leaves a lot of really complicated math. I'm not about to attempt to figure out how big an envelope you'd need before you hit neutral buoyancy--at whatever a reasonably attainable negative-pressure might be considered to be...

    That's all beyond my pay-grade... I'm just the nutty guy who's floating the notion...

    But floating is all about displacement. So at least in theory--this should be possible.

    Imagine: Massive lighter-than-air ships, barges--without any lifting-gas at all. You could engineer sails and and cruise the jet-streams for free.

    Coat their skins with solar-cells, and propel them even faster if you like...

    Helium is a limited resource. Hydrogen is plentiful--but expensive--and EXPLOSIVE--but you could just use plain old atmosphere--for my Aerogel-filled floating sail-barge idea.

    Airships always have always had to have three expendable systems--one of gas, one of ballast-weights, one of fuel.

    Flying an airship on altitude requires constant management of these three things.

    Displacement is all about maintaining the ratios between volume and pressure.

    If an airship began to rise too high too fast, it's envelopes would expand right on out into that thinner air--and might even burst. That's what brought down the USS Shenandoah airship. So they need "blow-off" valves, to prevent their envelopes/gas-bags/cells from bursting.

    If sinking--an airship can't "manufacture" helium outta nowhere, so they need to have ballast on hand--so they can dump that--if sinking too quickly.

    Further complicating this shitty "expendables" situation--was the equation of fuel. You'd start a journey heavy--and get lighter and lighter as you went--because you were burning fuel.

    Again--this meant venting your precious lifting-gas. Not so terribly handy.

    It's easy to see how an airship's journey is limited--according to how much ballast and lifting-gas they've got.

    This is still true with helium blimps (as far as I know it is anyway)

    At any rate, my idea potentially eliminates the issue of expendables.

    The emergency-valves for descent would be to open your cells--but rather than venting anything out, you'd be letting more heavy atmosphere in.

    Ballast would still be needed for emergencies--water's always a good choice--no matter where you dump it, or upon whom--the damage is likely not gonna be too crazy--if you really needed to stop an out of control descent.

    But essentially, under normal operations, you could be constant-weight with a system like I described--because you'd not need any fuel at all...

    At least not if you powered it with electrical motors, solar panels, and batteries for nighttime.

    Okay, *snaps fingers* Come on, Google. I know you've stolen and disseminated this idea--now how come nobody's built one yet?

    All the best,

    Last edited by tklop; 06-28-2020, 01:16 PM.

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  • calfee20
    commented on 's reply
    When I stop jumping from ebike project to ebike project I am going to have to do this to my main rides.

  • tklop
    commented on 's reply
    There it is (vid link: --or see the link under the pic) Well, calfee20 --it works! And I'm solidly convinced there is no simpler way or cheaper way to accomplish this.
    Last edited by tklop; 06-12-2020, 11:31 PM.

  • calfee20
    commented on 's reply
    Sometimes when the weather is poor I just sit around the house rather than go and do something. The past 2 days I have been working on my Vector enduro bike. I mounted all of my controls and decided to stick a battery in and spin up the motor. With just a slight throttle it spun nice and smooth. Add a little to the throttle and it jumped and bucked all over the place. The bike was on a stand of course.

    I left it for a day and after doing some reading and coming up with a plan I went at it again. I tried a few things and nothing worked. Maybe try another controller but before I did that I twisted the throttle in disgust and anger. Well it runs smooth full throttle to. So I let the throttle close and tried again and it is all fixed. The controller is an 18 fet Power Velocity unit with blue tooth and the web site doesn't say anything about a learning mode.

    I can't get the blue tooth going either. More reading on endless sphere and a phone reset. Maybe it will work now, who knows. Sometimes building these things will drive you crazy.

  • tklop
    commented on 's reply
    Sometimes the depression wins...

    Thanks for the reminder--I've got to put my order in at Conrad for the relay. But I hate shipping-charges, so I'm trying to put together a list... Maybe add some diodes to the mix, so I can make use of some LED lights I've already got.

    My own use is made more complicated, because of the lighting I've got going on. I want my "brake-lights" --on the side-fenders--to act also as "turn-signals"--and "marker-lights". The rear-fender's tail-light will need to have a brake-light function too, but I won't want that one blinking--no matter which side's turn-signal is flashing...

    Not too difficult so far--but then:

    The lights I want to use are similar to ones posted about elsewhere here--it's a two-brightness lamp assy, which uses two + legs--one with a resistor--to power the same array of LEDs. Problem with that, is backfeed through the 2nd + leg happens whenever the "Bright" leg is powered. Users here plopped a diode in that "Dim" leg--and seems to have taken care of it. I plan to do the same--for those side-marker/brake/turn-signal lights--so they'll stop backfeeding through the front-turn-signal lamps...

    So--my silly machine's circuitry becomes a little more complicated--and that has slowed me down some.

    My plan is to stick with the same plan--using that same relay, but then I'll try and do fancy things with the relay's brake-light output. (from pins 7 and 8). Maybe I'll send that through some other switching relays, I'm not sure. Maybe I'll just go with a single center brakelight, and leave the side-fender ones as turn-signals only.

    But I promise--I am going to give that relay-idea a shot. I'm certain it'll work flawlessly.
    Last edited by tklop; 06-07-2020, 12:10 AM.

  • calfee20
    commented on 's reply
    Waiting to see how you make out.

  • tklop
    E-bike Brake Lights via a $5 relay, suggested circuitry:

    Many have suggested using a relay, but have run into obstacles. I think they've been going at the problem the hard-way. Seems most have been trying to power their relay's-coil via the super-low-current "Low-Brake" signal, and the resistance added by the coil, and other factors have made that plan prohibitively problematic... So I've decided not to do that.

    There may be reasons this might not be the ultimate relay choice--this is just a model of the correct basic configuration needed. Many other relays of the same configuration might work--but at least this one has specs which can be easily looked up. Anyways, for better or worse, here it is:

    Omron G6B-2214P-US 5 VDC

    That's a 5VDC relay, with 2 normally-open contacts, which has six-pins--and no "common" or "shared" contacts.

    And here's how I'm going to attempt to use it:

    First, I'll splice a jumper into one of the controller's (+POS)4VDC leads (from either Throttle or PAS sensor).

    Next I'll connect my e-bike brake-handles' switches--in parallel with one another. One pair of those brake-switch leads will connect to the jumper I just made, the other pair will connect to the relay's Pin 4 (on that relay, (Pins 4 and 5 are for the relay's Coil Circuit).

    When either brake-handle switch closes, it feeds that (+POS) 4VDC controller's current via Pin 4, thru the relay's coil--activating it--exiting via Pin 5, and finally on to (-NEG) (Ground)--completing the Brake Handle Switches Circuit.

    That relay has two sets of contacts which close simultaneously when the coil is activated. One set of contacts uses Pins 1 and 2, the other set uses Pins 3 and 4. Either set of contacts could be used for either purpose below--I've just chosen and labled them as they are for the sake of simplicity.

    Pins 1 and 2 will be used to connect to the controller's "Low- Brake" wires (the controller-wires that used to be connected to the e-bike brake-handle switches). Whenever the relay's coil is powered, these contacts close, completing the Low-Brake Sensing Circuit and stopping the motor. (Note: That's really the big difference. That stupid, finicky, wimpy, fragile, problematic little Low Brake signal which made others abandon the idea of using a relay--will not be used to power anything at all in this relay circuit. No--instead, it will go sailing virtually resistance-free thru a pair of closed contacts--just as it had previously done thru the switches on the handlebars--only now, those contacts will be located nice and snug in a little relay-housing)...

    Pins 7 and 8 will be used for the Brake-Light Circuit.

    Any Brake-light power-source will do, any voltage. Polarity won't really matter either--but let's say we just connect the (+POS) source-wire to Pin 7.

    When the relay's coil is powered, these contacts also will also close, allowing Pin 8 to provide the (+POS) needed to illuminate the Brake-Light, and then from there, obviously on to (-NEG) (Ground)--and the Brake Light circuit is complete.

    That particular relay can handle up to 8A nominal for its contacts--and I think most of us using LED lighting would find our brake-lights operating way, way below that.

    Now--this might just be too dumb and simple to actually work--but I hope not...

    All the best, everybody.



    Here's the item. I went ahead and soldered on connections, so it'll drop right in place.

    As mentioned, any voltage light will work.

    Click image for larger version  Name:	Brake Light Relay.jpg Views:	0 Size:	1.89 MB ID:	107768‚Äč

    Here's a link to a YouTube vid I just put up to show the thing in action (Sondors mock-up).

    [END EDIT]
    Last edited by tklop; 06-12-2020, 11:16 PM. Reason: Added link to Proof of Concept video

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