PVC Pipe for frame?
 

I saw a few videos on YouTube about quads made of PVC piping. What do you guys think of using that for a material?

I've worked for a company for over 36 years making PVC pipe, fittings and glue. I think a bike frame from PVC pipe would work as well as a fart in a phone booth.

I would say PVC is a last resort for a bike frame. It flexes too much.
You can still make a lot of other good stuff from PVC like bike racks, Canoe racks for your truck, etc.

It flexes, expands and contracts, and makes a horrible looking and riding bike. What's not to like?

The best application for PVC with bikes is making little accessory add on posts and mounts. Well mitered and zip tied extensions have held bike computers and lights on recumbents for decades. Andy

And when it flexes too much, it shatters.

I suppose you could use PVC pipe as a foundation and wrap it with carbon fiber to provide strength and stiffness. But what would be the point?

I was looking at quads like these, from American Speedster

Top marks for ingenuity to those guys. But a bike frame would be hard, especially the fork, because it has fewer tubes. You would need large diameters, two top tubes (or similar). You would need a much larger diameter head tube and steerer and therefore non-standard bearings. And all the attachment points like dropouts etc. would need to be metal comprehensively glued in place (like you see on bamboo frames).

On the plus side of the ledger, sub-millimeter tolerances are probably not required. ;)

They aren't required on any other kind of frame either. Anyone says they hold those kinds of tolerances is blowing smoke

I made one once for a bicycle store rooftop. (display purpose only).

Back in the late 1970s there was an attempt to produce an "all plastic" bike. We saw plastic bearings (Nyfor? headsets), plastic freewheels (very yucky feeling between the sort of spin and rough catchiness to the ratchet) and more. A company produces a plastic frame (and not the engineered plastics we call carbon these days) and it was so flexy... I don't remember how the component interfaces were handled (as in a BB shell sleeve in metal?) as it was intended to accept then current parts. Some of us who handled or learned of this attempt have retained their dislike for plastic stuff. (or was it the cracking Simplex ft der clamps that soured our view of stressed plastic being better then stressed metal). Andy

I had a nyfor headset on my teledyne breakaway bike for a while. Suitable choice for a bike made out of CP titanium, which is just a little stronger than chewing gum.

I thought for a minute I forgot the smiley.

I was grumpy all day, had to turn off my computer.

Oh my gosh yes it will shatter unexpectedly! Terrible material for repeated flexing and vibrations.

The cynical side of me says these guys really just want to sell plans. I really question if these really work.

Some warning signs for me in include the note the pvc must be reinforced with wood or a metal pipe, there are no pictures of anyone sitting on these things, and there are no pictures of details like bottom bracket and crank setup

also PVC get really brittle in the cold which we know Alberta has.

This is so far off your long stated design goals that you should just rethink them

i.e forget quad go for 3 wheel, one in back and 2 in front, forget suspension and use big tires, super light outside covering, and so on. Good luck

I believe the OP has another thread about trying to build a 4 wheeler pedal thing with all kinds of uncommon thinking. A bunch of us tried to lend our views then too. Andy

This was me rethinking my plans, sir--using PVC pipe because I can't weld.

And besides, if I go 3 wheel now, the guys at Cranked are going to be super-annoyed: they just spent a joyous weekend last month lacing up the wheels for the rear end. :o (Note: On another forum I'm on, the forumites there use green to denote sarcasm.)

But I am seriously considering not using suspension, like you suggested.

And I'll make a confession: I've more than just seen videos; I have seen this in person--someone in a nearby town owns one. Their kids seem to like it.

It's much easier to learn to weld than it is to make a chassis or bike frame out of PVC pipe! Especially if you aren't too bothered about weight-- you can use thicker steel (like 1.6mm) and buzz it together with a flux-core welder, which only costs 100 notes or so. People are a bit snobbish about flux-core but with a little practice and a decent quality wire you can make an acceptable joint on material between about 1.6mm and 2mm thickness.

PVC is brittle when cold, also gets brittle when exposure to sunlight over time when it shatters it beaks up into shivs . To much flex . You can weld PVC it uses a plastic rod and hot air Harbor freight used to sell a PVC welder

Quick experiment. Take the longest piece you can fit it your freezer. let it sit over night. first thing in the morning take that outside and swing it around like a madman when it explodes look at the pointy end and ask your self do I want that to enter my body?

I admit that I stopped following the OP's earlier thread after it seemed like we were "talking" to a wall. Glad to hear that those plans have evolved a bunch. BTW unless you were a PIA to the shop that did the wheel building, and they were paid, they should welcome more work. Andy

I hope I wasn't a PitA to them--I just dropped the whole assembly off and asked them to call me when it was done.

Oh, and if you're referring to the 8-wheel monstrosity I posted a thread about, that was a joke, nothing more.

Joke? It was lost on me, what with 81 posts it looks like others were also fooled. Here's the link to the thread I'm talking about. Velo: Thus far, thus bonkers - Bike Forums Andy

That design didn't have 8 wheels, Mr. Stewart. The joke design I'm referring to is in https://www.bikeforums.net/framebuil...arcycle-d.html.

Actually that has got me thinking about an inline three-wheeler with rocker bogey suspension. There are still quite a few challenges with the concept however.

After watching the Utah Trikes video, I *REALLY* want to see a fully enclosed plywood version with a rear bench seat, full suspension, floor, the “driver” and two parents and a tuba inside rolling down the road. Any road. Paved, dirt, frozen, muddy, rutted, unplowed, tore up from beer-swillin’ yahoos in their brodozers... you name it! I’ve got the popcorn popped, extra buttery, and the couch pillows are all fluffed up! Bring it!

I'll watch the video :) I was thinking inline trike inspired by the 6-wheeler and 8-wheeler cars. So all three wheels in a line and you ride it like a regular bike. That car design is actually not as mad as it at first sounds and does have a few things going for it.

I was thinking about how to best answer this, thus the delay in replying.

I was looking at this for ideas, not necessarily to directly copy.

My goals are, and have always been:

1) Must be stable. Yes, recumbent trikes are stable, HOWEVER:

2) Ingress and Egress must be reasonably easy. By the time a recumbent trike is low enough to be stable, it's so low that, with the baking show's worth of lard padding my seat, it's hard to get out of. Some trikes I almost had to roll off the seat onto my hands and knees, then get up. Therefore...

1a) Must be stable with a relatively high center of gravity.

3) Must provide some protection from weather.

4) Must have a smooth ride. Honestly, fat tires looked tempting, until I found out how squishy they are. I've ridden on half-flat tires before. No fun. Thus the suspension.

5) Be COMFY. Which is why I wanted to go the recumbent route in the first place.

6) Be nice to look at... and I kind of like the look of old cars, on which my original design was VERY loosely based.

7) Must have decent carrying capacity, including room for saxophone or guitar, or groceries.