Plastic sheet - material/source?

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jameso
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Plastic sheet - material/source?

Post by jameso » Fri Mar 27, 2020 8:35 am

Had a quick read of the plastic sheet seatpack posts here and it got me thinking. Can anyone tell me what sort of plastic is used for guard flaps like these? Same stuff as an Asssavers guard.

https://rawmudflap.uk/gallery/

I've got a couple of Rawflaps -yeah, I know :grin: - so, wanting something else to do now my riding hours are down.. I made an extended front flap for my Brompton from truck tarpaulin but it's too flexy/flappy for the guards on my all-road bike, want to make something for the front that Rawflaps don't offer. The Rawflaps stuff is really good btw, recommended kit.

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Bearbonesnorm
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Re: Plastic sheet - material/source?

Post by Bearbonesnorm » Fri Mar 27, 2020 8:51 am

James, remind me of your address and I'll stick you some int' post.
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mfezela
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Re: Plastic sheet - material/source?

Post by mfezela » Fri Mar 27, 2020 4:36 pm

Ass Savers are 0.8mm polypropylene.
Here's one online source. There's bound to be someone close to you.
Steelexpress, Hindleys, ebay. Signwriters and outdoor advertising companies sometimes use the same.

https://www.kitronik.co.uk/materials/po ... heets.html
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jameso
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Re: Plastic sheet - material/source?

Post by jameso » Sat Mar 28, 2020 7:57 am

Great stuff, thanks to you both. Will PM, Mr BB.

Cyclepeasant
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Re: Plastic sheet - material/source?

Post by Cyclepeasant » Sat Mar 28, 2020 7:38 pm

Any of you guys in the building trade?
I have been using damp course to make mudflaps for years.
Rigid with give if caught on a root,rock etc.
Use cable ties or existing screw holes etc.
Not posh,just functional.
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oreocereus
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Re: Plastic sheet - material/source?

Post by oreocereus » Tue Mar 31, 2020 12:03 pm

To hijack this thread, I'm looking for a plastic to make a rough handlebar harness with. Without being able to go into a store and feel different materials, and knowing little of plastics, i feel a little blind (most DIY guides refer to US specific materials).

Anyone who's more MYOG oriented have a good idea of what to aim for in terms of balancing stability/stiffness with the right amount of flexibility to wrap around a dry bag?

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Bearbonesnorm
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Re: Plastic sheet - material/source?

Post by Bearbonesnorm » Tue Mar 31, 2020 12:13 pm

Anyone who's more MYOG oriented have a good idea of what to aim for in terms of balancing stability/stiffness with the right amount of flexibility to wrap around a dry bag?
Roughly what size of piece do you need?
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oreocereus
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Re: Plastic sheet - material/source?

Post by oreocereus » Tue Mar 31, 2020 12:46 pm

Hmm, probably minimum 30cm x 40cm.. larger in either/both of those dimensions give me a bit of room to play a little with the design.

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Bearbonesnorm
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Re: Plastic sheet - material/source?

Post by Bearbonesnorm » Tue Mar 31, 2020 1:57 pm

I've got a piece of 2mm HIPS here but it's only 22cm x 30cm. Yours if it's any good to you?
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mfezela
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Re: Plastic sheet - material/source?

Post by mfezela » Tue Mar 31, 2020 4:47 pm

High Impact Polystyrene, HIPS is less flexible and more brittle than Polypropylene, PP.

PP allows for cold creasing and repeated (but not infinite) bending at that crease, whereas HIPS requires heat to crease successfully and repeated bending will quickly cause cracking.
Both can be cut by knife, but HIPS requires more careful treatment at sharp corners to prevent tearing. Ideally there aren't sharp corners for either material, try for rounded corners instead.

A useful comparison site.

https://www.makeitfrom.com/compare/High ... omopolymer
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oreocereus
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Re: Plastic sheet - material/source?

Post by oreocereus » Tue Mar 31, 2020 8:21 pm

Bearbonesnorm wrote:
Tue Mar 31, 2020 1:57 pm
I've got a piece of 2mm HIPS here but it's only 22cm x 30cm. Yours if it's any good to you?
Oh thanks, that's very kind! Having not handled it, do you reckon it's about the right stiffness for a handlebar harness for a bigger drybag (I use synthetic sleeping insulation)?
My other thought is that it might be a touch too small in dimension to be able to wrap effectively enough on a bigger drybag, and I don't want to take it off your hands if it'll be wasted on me. I gather you've probably enough experience using and making bikepacking stuff to advise there?
mfezela wrote:
Tue Mar 31, 2020 4:47 pm
High Impact Polystyrene, HIPS is less flexible and more brittle than Polypropylene, PP.

PP allows for cold creasing and repeated (but not infinite) bending at that crease, whereas HIPS requires heat to crease successfully and repeated bending will quickly cause cracking.
Both can be cut by knife, but HIPS requires more careful treatment at sharp corners to prevent tearing. Ideally there aren't sharp corners for either material, try for rounded corners instead.

A useful comparison site.

https://www.makeitfrom.com/compare/High ... omopolymer
Thanks for this! I was planning to cut with a fresh scalpel blade and sand the edges a little - would this be suitable?

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mfezela
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Re: Plastic sheet - material/source?

Post by mfezela » Wed Apr 01, 2020 12:00 pm

Re: Corner treatment of thin sheet polymers.

External corners should be rounded, not for strength but to reduce sharp edges.

Slits cut into the material, e.g. for fixing straps, must be rounded. If not, the acute corners are very prone to splitting (jagged line on sketch). For narrow slits a larger than slit width hole is recommended.

For DIY purposes, external rounded corners are easiest cut with scissors. Use a hand drill (or any very slow speed drill) with brad point wood bit for internal corners. Drill holes first, straight cuts with modelling knife thereafter.
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oreocereus
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Re: Plastic sheet - material/source?

Post by oreocereus » Wed Apr 01, 2020 12:18 pm

Excellent tips. Almost certainly would've omitted to round internal corners without that comment.

jameso
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Re: Plastic sheet - material/source?

Post by jameso » Fri Apr 03, 2020 9:40 am

Bearbonesnorm wrote:
Fri Mar 27, 2020 8:51 am
James, remind me of your address and I'll stick you some int' post.
Arrived, thanks - got more ideas now. Lightweight roadpacker seat pack rolls.

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