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modular fiberglass

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runcyclexcski View Drop Down
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    Posted: 07 May 2018 at 8:04pm
Fiberglass brings about thoughts of the 1970s and first failures in composites. Fiberglass hockey sticks and skis sucked in the 1980s. Is fiberglass all but abandoned in HPV? I have been experimenting with fiberglass, kevlar and carbon composite tubes and composite panels over the last year. I found that, cost-wise, fiberglass is quite hard to beat, particularly if one combines it with cheap Al honeycomb. At 2x the weight, I found it 10x less costly than CF, and it's much easier to cut with shears after curing. I so far have been using FG to build fragments of shells, but now I am thinking to try it for the trike frame as well (I am not going for the monocoque design, long story). E.g. I found that Unistrut (the company that makes all-familiar steel hardware) sells modular fg flanged U-channels in 40 mm, with a full set of nuts, bolts, angles, etc. So I am thinking if I can assemble the frame truss-style by bolting it together, rather than using traditional irreversible methods that are used for steel and composites (welding and gluing). If the idea fails (w/o killing me, hopefully), I will have plenty of angle brackets, bolts etc for shelves, racks, chairs, etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GeoffBird Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2018 at 10:24pm
Miles Kingsbury and I have used fibreglass skinned aluminium honeycomb to make wheels. A bit heavier than carbon but much cheaper. If used correctly, GRP has higher specific strength than aluminium.
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runcyclexcski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2018 at 11:01pm
Geoff -- thank you! In fact, making the wheel disks is what my fiberglass panel project was also about, to experiment with different materials, epoxy/fabric ratios etc What about fiberglass in framing materials and/or using bolt-together sections, like in this (failed) kick starter project?

https://www.backerkit.com/projects/reframed/reframed-bicycle-a-fully-customizable-self-assembl

(not sure what they needed 60K for, but anyway, too bad)

Welding/bonding is lighter and more pleasing aesthetically, but is largely irreversible, requires more skill/investment, not adjustable



Edited by GeoffBird - 08 May 2018 at 8:27pm
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runcyclexcski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2018 at 11:07pm
BTW, turns out, a bolt-together chassis kit is available for a pickup kit:

https://www.speedwaymotors.com/1947-1954-Chevy-1-2-Ton-Pickup-Truck-Frame-Rails,63702.html

seems ridiculous to use a bolt-together chasis for a car, but wheels are bolted to cars, too, and nobody seems to complain. I've changed flats a few times... used an steel pipe for leverage, strategically placed in the boot, bolts never came loose.

Edited by GeoffBird - 08 May 2018 at 8:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GeoffBird Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2018 at 8:32pm
In the old days, most car chassiseses were bolted together, as were some bicycle frames and IIRC, Scott motorcycles. It is possible to disassemble bonded joints, but heat is required, so better for bonded aluminium. Perhaps we need an adhesive with an 'antidote' that can be applied if we wish to disassemble the joint. There is one for anaerobic adhesives (superglue), which is most frequently used for debonding fingers...
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runcyclexcski View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote runcyclexcski Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2018 at 9:28pm
I did not know they used adhesives in bolt-together frames? Most epoxies come apart in chloroform, in my expeirnece. Problem is, it evaporates, so you have to bag the whole thing. That said, some epoxies are more resistant than others.

I am getting more interested in this bolt-together approach. Bolt-together seems to dictate the use of U-channels, I-beams, and rectangular tubes (just like that truck frame did). Will read more on using these as members. Bolt-together beams could be used as a step towards a laptop-cost velomobile or HPV (the cost of a high-end laptop, to me, is the max I am ready to spend in one shot, other than a car, or a downpayment). If someone made a kit for GBP 2000, and it came in a flat pack full of beams, panels, and bicycle parts, I would be happy to invest a few weekends into bolting the pieces together. We enthusiasts have the time.

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