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Old 02-25-2021, 03:23 PM   #21 (permalink)
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The most beautiful soapbox derby car I ever saw was fiberglass over expanded metal. Shape the expanded metal to the desired shape drape the fiberglass satin weave over it and saturate it with polyester or epoxy resin. Let that cure and add closed cell styrene foam (Like the Dow blue foam insulation) or balsa wood cores and add a layer to the inside. Aluminum or fiberglass window screen would work too. A downside to using foam for cores is you have to use epoxy with it and that is more expensive. 0.007" thick aluminum newspaper lithography press plate is another material to consider for 2D sections.

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Old 02-25-2021, 03:51 PM   #22 (permalink)
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Originally Posted by The Toecutter View Post
In the long run, I plan to build a 100 lb "car" inspired by Electrathon racers that can be similarly operated, except that the rider will be able to add pedal input at all operable speeds including what may be a top speed of 100+ mph, but will still be able to turn everything off and hopefully the machine will be efficient enough to pull sub 4-hour century rides or sprints to 40+ mph on human power alone. The plan is to make a full suspension roll cage on wheels that uses light-duty DOT 16" motorcycle rims on all 3 wheels with Mitas MC2 low rolling resistance tires, hydraulic brakes, and a Schlumpf HS drive on the pedal crank with a sufficiently wide gear range to allow anything from slogging up steep hills at 3 mph with a 60 rpm cadence to careening down the highway at 100 mph with a 140 rpm cadence, and everything in between. Having both a human power drivetrain as well as an electric hub motor will also greatly reduce the risk of ever being left stranded. I think a 100 mile range @ 70 mph and 300 miles range @ 30 mph is possible in such a thing with a very modest 1.5-2 kWh battery pack. Performance would only be limited by downforce/lift and the type of hubmotors available on the market. There are no synchronous reluctance or synchronous reactance hub motors of appropriate size with bicycle cassette/freewheel compatibility on the market, but a 7 lb motor of this sort could make 50 horsepower peak and 6-8 horsepower continuous if it were made, which would allow Tesla-like acceleration. In such a low mass vehicle, it would be difficult to design it for stability at much of anything over 100 mph, so that would be a good end point for ultimate top speed, no matter the peak power.
Something like this?
https://kronfeldmotors.com/specs/



Although it's a series hybrid, your pedaling just goes to charging the battery and there's no direct connection to the wheels.
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Old 02-25-2021, 05:10 PM   #23 (permalink)
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Quote:
Originally Posted by Crazyrabbit
The most beautiful soapbox derby car I ever saw was fiberglass over expanded metal.
The Golden Zepplin is a reverse trike. ...of sorts. It's made of perforated metal over welding rods. All that needs would be a vinyl wrap (over 30x stainless steel. )


https://content.instructables.com/OR...XY.jpg?frame=1
Quote:
Although it's a series hybrid, your pedaling just goes to charging the battery and there's no direct connection to the wheels.
I was thinking about this to enable regen.
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Old 02-25-2021, 05:28 PM   #24 (permalink)
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Originally Posted by samwichse View Post
Something like this?
https://kronfeldmotors.com/specs/

Although it's a series hybrid, your pedaling just goes to charging the battery and there's no direct connection to the wheels.
Sort of. The difference between that and what I want to build is the following:

1) The linked vehicle has far too high of a frontal area and given its specs it's overall aerodynamics aren't on par with those typical of a commercial velomobile. I seek to build something with the form factor and drag of a velomobile. This is built to offer a large rider plenty of room and a tall ride height, whereas I'd build a low-slung vehicle to fit the rider like a glove.
2) The linked vehicle is extremely heavy. It is built closer to the safety specs of a car than those of a velomobile. Because of its oversized motor and battery pack, it requires more pounds of battery per mile of range. To me, this is greatly extraneous. Lightness and efficiency beget more lightness and efficiency, and this thing is built to be so heavy that its components all must be heavier to compensate for it. This thing is as heavy as a high performance motorcycle, if not moreso.
3) If the battery runs out of charge or the EV drive system fails, the above vehicle is stranded. I intend to make a vehicle that can still function as a bicycle and be independent of the need for an EV drive system to move, which will require keeping it sufficiently low in mass that a fit rider can still pedal it up a steep hill and sufficiently low in drag that on flat ground and downhill it yields a significant advantage over a normal upright bicycle.

This all said, the Raht Racer is an interesting and cool concept. But the pedal generator isn't going to contribute much to its total energy use, probably on the order of a percentage point or two. It is reminiscent of the Twike designs in that sense. It's much too bloated for the application I have in mind, and the pedal drive system seems to be a gimmick from a purely functional standpoint, if the function is reducing electricity usage.

What I want to do is make a vehicle that can perform like a car, but still function purely as a bicycle whenever the need arises. This in turn will assure that it reaps the benefits that come with that, such as phenomenal energy efficiency. With the design I have in mind, it is conceivable that even careening down a highway at 100 mph, a fit cyclist could still conceivably account for 10% or more of the load for a few minutes at a time, and at freeway speeds of 60-70 mph, maybe even 20% of the load for hours at a time, or turn the motor off entirely and account for 100% of the load riding it at 25-30 mph in the city. The 450 city/230 hwy MPGe of the Raht Racer could EASILY be beaten by a wide margin. Mine gets between 3,000-4,000 MPGe as it is, even though unlike the Raht Racer it has zero crashworthiness nor is it nearly as fast, but I intend to improve upon that. There are electrified Milan SL velomobiles getting 5,000+ MPGe in city riding and if made mechanically reliable and dynamically stable for high speed riding, with their aerodynamics could easily get 2,000+ MPGe highway, and like most commercial velomobiles, they have some rudimentary degree of crash-worthiness designed into them. A modern velomobile is not anything close to as safe as a modern car, but it's greatly safer than a bicycle or motorcycle, and I think that is a reasonable degree of safety to design for when coupled with robust enough wheels/tires/axles/hubs/brakes/chassis to handle 70 mph freeway cruising, and all of which is possible within the maximum weight limit I have in mind of 100 lbs.

Last edited by The Toecutter; 02-25-2021 at 05:37 PM..
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Old 02-25-2021, 09:19 PM   #25 (permalink)
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To achieve your goals will likely require component designs optimize by adversarial generative
AI and 3D printed parts with gradient gyroid infill.
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Old 02-25-2021, 11:08 PM   #26 (permalink)
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Quote:
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To achieve your goals will likely require component designs optimize by adversarial generative
AI and 3D printed parts with gradient gyroid infill.
Maybe. But consider that there are light duty motorcycles of ~130 lbs made to handle 60+ mph, made without that tech, such as the Mountain Moto FX5, and they have heavy IC engines and 4-speed transmissions and exhaust systems and fuel tanks to be removed from them. And they have large 19" motorcycle wheels. And they're built for the rigours of offroad riding, and not smooth pavement.

There are hobbyists who have modified velomobiles to handle 45 mph cruising speeds and get 200 miles range at said cruising speed while keeping the entire package under 100 lbs. It's not inconceivable to trade some battery weight for more robust mechanicals/chassis to handle higher speeds.

And even if it goes 10-20 lbs over the 100 lb weight limit, it's not exactly a deal breaker either, as it will still be of a pedalable weight, if only barely so, especially considering it would primarily be intended to operate with electric assist.
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Old 02-26-2021, 12:59 AM   #27 (permalink)
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I think it's achievable.The AI is just software, you can probably submit your requirement somewhere and have it iterate it's way to a solution in the cloud.

Suspension arms is what I was thinking of, but that may be out of reach.

I've been watching Youtube videos on 3D printing, and you can do things like print in PLA and then use an auto-catalytic bath instead of electroplating to plate the part in copper and nickel. It doubles the strength. For brackets and suchlike.
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Old 02-26-2021, 02:25 PM   #28 (permalink)
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Urethane foam can accept polyester resin.

Quote:
Originally Posted by Crazyrabbit View Post
The most beautiful soapbox derby car I ever saw was fiberglass over expanded metal. Shape the expanded metal to the desired shape drape the fiberglass satin weave over it and saturate it with polyester or epoxy resin. Let that cure and add closed cell styrene foam (Like the Dow blue foam insulation) or balsa wood cores and add a layer to the inside. Aluminum or fiberglass window screen would work too. A downside to using foam for cores is you have to use epoxy with it and that is more expensive. 0.007" thick aluminum newspaper lithography press plate is another material to consider for 2D sections.
And you can use a skim coat of TiteBond glue over styrene foam before the use of polyester resins.
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Old 02-26-2021, 02:29 PM   #29 (permalink)
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This thread just tickles my fancy.

Living in Southern California makes a vehicle such as these a year round practicality.
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Old 02-26-2021, 03:02 PM   #30 (permalink)
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I just posted one of these in a thread in the Aerodynamics subforum:

http://www.dailyicon.net/2009/02/dym...isamu-noguchi/





Quote:
In later years, Fuller recalled that the aim of the “Dymaxion” transport project was “to develop an omni-medium transport vehicle to function in the sky, in negotiable terrain, or on water.” Using existing Ford Motor engines, Fuller postulated that by taking the conceptual basis of an airplane and applying the principles of wind resistance and the aerodynamic shape of fish, he could develop a new concept of the automobile...

Fuller originally sketched his stylized vehicle in 1927 and in 1932 looked to his friend, Noguchi, to sculpt the three-wheel model for the “Dymaxion” car based on these early drawings. The models were later painted by Fuller.
.....
Dymaxion Car Model, Executed by Isamu Noguchi, Painted by Buckminster Fuller, Sold at Auction $92,500, at Sotheby’s

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