LWB recumbent for long trips.

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BalorNG   1 W

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LWB recumbent for long trips.

Post by BalorNG » Mar 29 2021 3:59am

It took on enough shape that I think it merits a thread.

It it a platform to be fully faired, hence some rather unconventional designs choices, like low-trail geometry, steering damper, semi-low seating and LWB form-factor - all according to theory that too much trail and too forward a CP does not bode well for stability in crosswinds given a full fairing.
And yes, it's 100% no-weld.

I've been experimenting with design and assist in previous iterations, and been thinking about turning it into a leaning diamond quad - but the idea been put on back-burner because I *think* I'll manage well in a purely singletrack mode.

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2.3kwh (hopefully) of chinese lifepo, and electric transmission - not unlike on Electrom, but (without downplaying his pretty creative solution) much smarter in my case.

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There should be at least 3 RC motors on my setup: a generator, a high-geared fixed gear drive used for efficient cruising and regen braking (belted) and low-geared, double reduction motor for starts and hills. I'm thinking about front drive, too.

The heart(s) of the system is vescs and arduinos, communicating with UART.
Basically, I have real-time data on power I am generating, and transmit it wirelessly to two motors that, in turn, 'share the load', with priority given to the more efficient motor.
Setting any level of assist (or even 'regen pedalling') is a simple matter of controller logic.

Currently I'm having trouble with torque (unsurprisingly, since my 'ride' weight 50 kg and I weight 120) and hall sensors, so I've yet to truly try it on the street (it takes two to haul it to up to 7th floor, so I want to be absolutely damn sure it works like I want to).

The key idea is to predominately use human power for propulsion and using assist mostly to 'even out the hills'.

I'm not 100% sure that I'll leave electric transmission as main mode of operation (that depends on efficiency of the system, I have hopes but reality can be a bitch).



P.S.
I'll likely experiment with friction regen brake as well, once I get the system working. I don't want to rely on friction drive for torque - it can be unreliable in wet weather.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 01 2021 5:26am

Belt transmission is being fine tuned, 3d printed a huge chainring of carbon filled pla (as well as first stage jackshaft)... should be worth for a few hundreds kilometers hopefully, the weather is not quite rideable due to pouring rain (will order laser cut cogs later)

Control signals are routed wirelessly and power from pedal generator is split between two motors, with a button for starting at max torque - starting with input from pedal generator turned out to be impossible, but than being able to start w/o pedalling is, actually, a good thing - recumbents don't exactly shine in this respect.

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With two motors and a jackshaft it finally feels *somewhat* brisk (ok, not too sluggish)

Combined torque at the wheel is, frankly, kinda measly 58 Nm (will not actually take me up even all the local hills), but due to 3d printed components I don't wanna crank it up any higher... maybe later.

TrotterBob   1 mW

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Re: LWB recumbent for long trips.

Post by TrotterBob » Apr 01 2021 5:31am

Love that no weld philosophy. Works great for us non-welders.

Are those bike stems as rear dropouts? How does that work? Are those solid axles, QR or thru-hubs?

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 01 2021 5:39am

TrotterBob wrote:
Apr 01 2021 5:31am
Love that no weld philosophy. Works great for us non-welders.

Are those bike stems as rear dropouts? How does that work? Are those solid axles, QR or thru-hubs?
12mm through hub, with a 3d printed insert inside the stem. Seem to work, but frankly I need to ask a steel 12mm axle machined, or maybe grab M12 150mm shoulder bolt - there is a LOT of weight on the rear.

TrotterBob   1 mW

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Re: LWB recumbent for long trips.

Post by TrotterBob » Apr 01 2021 6:11am

Thanks for the reply. Working on a long term project here and was wondering how to join tubes to wheels. Going to eventually build a solar bicycle trailer/camper.

Those tube clamps you have elsewhere remind me of hydraulic pipe or Stauff clamps I see on ebay.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 02 2021 2:23am

TrotterBob wrote:
Apr 01 2021 6:11am
Thanks for the reply. Working on a long term project here and was wondering how to join tubes to wheels. Going to eventually build a solar bicycle trailer/camper.

Those tube clamps you have elsewhere remind me of hydraulic pipe or Stauff clamps I see on ebay.
It's a combination of 3d printed 'pillow blocks' and laser cut plates - a sandwich of sorts. Heavy, but been pretty damn reliable so far.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 03 2021 1:03pm

First outing! Just a ride to the garage, using mostly pure 'human powered' mode - no pictures cause helper arrived only in the evening. Worked really well, too well really - the 'power transfer' is a bit 'too' immediate and cases some suspension bob and noise as second motor engages to help the first one as it gets torque overhelmed at slow speed. Yea, human power is damn pulsatile!

Will need to add more aggressive smoothing.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 04 2021 2:34pm

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Ok, had one clamp slip on slippery carbon tube (should have thought about it) and ruin my geometry on the second ride, so had to spend almost entire day fixing it . On the plus side that was actually something I've been contemplating for a long time anyway, ehehe.
Did get some seat time - it IS pretty sluggish w/o any assist (using electric generator power output w/o any modifiers for additional motor drag), so after adding a few modifiers (still much less than even 250w of 'legal' assist) it feels much more enjoyable now, and about 5 wh/mile at 30 kmh.

Not particularly impressive, but weather is windy and close to freezing, that pretty much double rolling resistance that is already double that of a typical racing bent. With 'aggressive' smoothing it feels less of a bike and more of a e-bike, I'll need to fine tune it for a balance of 'feel' and 'efficiency'.

I think that on very cold weather belts are much more draggy, too... but I love how smooth and silent they are at high RPM!


On the plus side the experience of being able to pedal as hard or as light as you want and not fiddle with any gear changes whatsoever IS pretty damn cool. Unfortunately peak input power is limited to about 500w - a bit more if I pedal smoother. I think I should add some sort of 'boost' button that temporary boosts my cadence to 120 or so, for better peak power out, it also meshes better with my short cranks (currently it floats around 95-100).

fatty   1 kW

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Re: LWB recumbent for long trips.

Post by fatty » Apr 04 2021 3:23pm

Per your previous thread, this is exactly the dangerous behemoth deathtrap that's going to get safe and practical ebikes restricted.

This doesn't belong in bike lanes or on public roads.
Don't take advice from:
there is no difference between a mean well CC/CV power supply and a device sold as a charger. they operate in EXACTLY the same way
Testing has demonstrated that ordinary rim brakes thermally outperformed all but the best disc brakes...You'll always add weight and cost, while not equalling the capabilities of comparable rim brakes, if you use discs

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 05 2021 2:11am

fatty wrote:
Apr 04 2021 3:23pm
Per your previous thread, this is exactly the dangerous behemoth deathtrap that's going to get safe and practical ebikes restricted.

This doesn't belong in bike lanes or on public roads.
Hah, so you ARE on a moral crusade. Your demagogy is noted and duly dismissed.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 06 2021 5:00am

An other ride, this one is quite uneventful.
Some telemetry to whoever is interested:

https://www.strava.com/activities/5077965007
Power meter data, and logs from all 3 controllers.

I've added some flat bonus to power output in addition to 1.5 multiplier, and it feels pretty good now - basically like a lighter and more aero bike.

The weather is cold and very windy, and it clearly shows in the data! W/o fairing I'm still (unsurprisingly) 'unaero', and with assist that is less than 'legal' even you can hardly expect wonders.

~7 wh/mile overall.

Yea, and despite quite a bit of lateral area, there is pretty much zero steering disturbance from side wind gusts whatsoever, low-trail geometry does work! Of course with a fairing, and at higher speed, things will be different... we'll see, but it gives me hope.

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neptronix   100 GW

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Re: LWB recumbent for long trips.

Post by neptronix » Apr 06 2021 1:52pm

Looks pretty dangerous ( in a structural integrity way ), unaerodynamic, insanely heavy, and the opposite of stealthy.
Why did you chose to build a bike this way?
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 07 2021 1:05pm

neptronix wrote:
Apr 06 2021 1:52pm
Looks pretty dangerous ( in a structural integrity way ), unaerodynamic, insanely heavy, and the opposite of stealthy.
Why did you chose to build a bike this way?
Because it's an evolutionary design, basically, and test bed for some of my ideas. Plus, I don't weld - I have no facilities.
Structural integrity will be fine once I get all the tubes properly bonded by composite lugs, but I need adjustability for now.

I already have plenty of bikes, upright and recumbent, including those that are faster w/o any assist, but true speed and economy is possible only with a full fairing - and that is a very considerable challenge that I've been been researching for more than a year already - from basics of aerodynamics to specific effects of wind disturbances over control of the singletrack vehicles.

NOT being insanely heavy is not an option - because I weight over 250 lbs myself, plus recumbents don't exactly shine in power delivery department, especially uphill (posture-related perfusion penalty, mostly), so I need some sort of assist anyway - and heavy weight is *bonus* when it comes to fully faired vehicles, makes them safer actually.

My goal is long trips using *mostly* human power with help of a full fairing, using assist uphill and regen downhills to mostly negate the 'weight penalty'. The shell is just not done yet.
I agree that a typical velomobile is likely better, and I'll gladly accept donations towards a Quattrovelo. Those that insist on unsolicited suggestions w/o any monetary contribution, however, can go... somewhere else and have tons of fun there.

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neptronix   100 GW

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Re: LWB recumbent for long trips.

Post by neptronix » Apr 07 2021 4:31pm

Wouldn't a bike that's half the weight or less be a better bike for uphill? why build a heavier one if you have poor power delivery ( creating more of an uphill problem ).

There's a lot of recumbent bikes that can hold up to 300lbs out there.

I see how movable pieces can be a test bed for ideas and the value in that. But hopefully the final resulted is welded or constructed in a structurally more sound way.

A fairing with the right cross wind protecting design ( ie as short as you can get away with, and close to the rider ) would go further in reducing cross wind issues.. in particular, sealing the back of the fairing at key places would make it much less of a sail. I would consider a better fairing design over another ~40lbs of weight. And just think.. minus ~40lbs of weight, you could add 40lbs of batteries instead if you really need ballast. :thumb:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 08 2021 2:03am

neptronix wrote:
Apr 07 2021 4:31pm
Wouldn't a bike that's half the weight or less be a better bike for uphill? why build a heavier one if you have poor power delivery ( creating more of an uphill problem ).

There's a lot of recumbent bikes that can hold up to 300lbs out there.

I see how movable pieces can be a test bed for ideas and the value in that. But hopefully the final resulted is welded or constructed in a structurally more sound way.

A fairing with the right cross wind protecting design ( ie as short as you can get away with, and close to the rider ) would go further in reducing cross wind issues.. in particular, sealing the back of the fairing at key places would make it much less of a sail. I would consider a better fairing design over another ~40lbs of weight. And just think.. minus ~40lbs of weight, you could add 40lbs of batteries instead if you really need ballast. :thumb:
The problem of singletrack dynamics in combination fully fairings and side force input in pretty complex.
It is summarized (not in ALL the detail, btw, there is also *pneumatic* trail to consider!) here:

https://motochassis.com/Articles/Aerodynamics/AERO.htm

Next, 'just' lateral area is one thing, and it does bear minimising - BUT...

Look at Vetter fairings:
http://craigvetter.com/pages/470MPG/Ind ... iring.html

Look at this monstrously long tail. You may thing that the guy is insane and it will make the bike unrideable in any crosswind?
Actually, reverse is mostly true.

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Typical short wheelbase motorcycle (not a feet-forward recument type) has too forward a CP in relation to CG, making the design aerodynamically unstable. By extending the tail, you can somewhat fix this problem - and give the bike less drag, too... balance corrections (for toppling moment) are easily done by steering corrections, so long as side force/trail couple does not add it's own torque contribution and throw things out of whack!

Same applies to short vs long wheelbase bicycles. You don't need to specifically lengthen the tail on an LWB recumbent, but no LWB recumbent can be as light and stiff as a diamond-frame bike, unfortunately.

The tubes are thin cromo, btw, relatively light and very strong, and I'll replace some with carbon tubes, but quest for light weight can get you into silly cost numbers and compromise that very structural integrity... while using assist + regen for hills allows one to extract nearly 80% of kilojoules spent climbing, good tires set up tubeless can minimise rolling resistance penalty, and a fairing will take care of subpar aero - that's the idea, anyway.

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 10 2021 10:09am

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20-25 mph wind - just about time to mount a 3d printed 'stabilizer' and go out to ride while allowing the wind to 'broadside' you!
The test is passed with flying colors - there is absolutely NO effect of 25+ wind gusts on steering and negligible - on balance, there is some course correction taking place - either my automatic reaction to balance the bike or due to pneumatic trail, but it's minimal.

Very short trail geometry + steering damper just works. So, next step is making of the shell... which will make the wind effect much greater, of course, but so far it seems good enough and gives me hope!

BalorNG   1 W

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Re: LWB recumbent for long trips.

Post by BalorNG » Apr 13 2021 10:15am

To a question of 'unsafe'... had front tire puncture today, failed almost instantly, lost control and slide on the side.
Funny thing is, I've already create a 'ghetto tube plus' system with a tubular tire inside a tubeless tire for 'run flat' capability, but I didn't have it on THIS ride *doh*.
Anyway, the monstrously unaero contruction worked *exactly* like it supposed it, protecting me completelyas I slid to a harmless stop - not even strip of road rash. Well, not that I wanted to test that early, but THAT test is passed as well :)

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