Frame materials

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dmar836

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Jun 23, 2009
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This sounds like a 1st grade discussion. IMO, if one starts with conduit for a frame, it is an indication of the shortcuts one is willing to take, early on, to have something that he cannot otherwise afford. After the frame, there is much more to do. I had these types of fantastic ideas only when I was a child - with no knowledge of the properties of metal. I built many wooden gocarts with plastic wheels and used large nails for axles! I also built "houses" out of cardboard boxes. In reality, neither of these were what I had imagined them. Even by highschool, I knew there were many ways to do something but only a few right ways. Nails are not appropriate axles, cardboard is not building material, and conduit is not bicycle/motorbike frame material.
Steel tubing isn't that expensive and hacking a bicycle frame or two for (non-butted)tubes would be far better.
Suggesting conduit as an option, regardless of the rationale, is irresponsible and shows one has much to learn about the basics, even if another says it can be done. Since when do we try to achieve the least common denominator with mechanical devices?
Cost is not the issue as metal is often cheaper than wood. Availability? Metal can be ordered online for a bit more in shipping. If you have access to a welder, why can't you spring for proper building materials? Next will be fuel tanks out of coffee cans!
Don't hack!
JMO,
Dave
KC
 
B

Board Track Racer

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You posted a question and received 3 pages of answers. Your going to be the one riding it. What do you think is the appropriate material?
I don't think anyone is trying to judge your inteligence, I think you seem offended that everyone didn't give you the answer you were looking for.
EMT is cheap $$ and easy to bend If it was a suitable material for bicycle frames why don't all the companies use it?

Would you buy a Worksman, Schwinn, or Raleigh made form EMT?

Spend the extra money and go with steel, DOM or seamed tubing.

Or like dmar836 said, I would cut steel tubing off a donor bike before I used conduit... but thats just my opinion.

My latest project! .....sorry had to break up the tension. dance1
 

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Reel Adventure

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Jul 1, 2009
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Your time is worth something. You should spend a little more and do it right the first time instead of having to come back and do it over. In the long run you will save money if you think of it that way.

Look at what Halycon or some of the other builders are doing. 3 pages of "dont do it's" would be enough for me. I think you answered your own question when you said you want to use it because it bends easily. That bend easy part will go both ways if your building it or riding it.

Good luck!
 
Elmo

Elmo

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I have built a few bicycles. The first ones were made of salvaged tubing from old junk bikes. most of the time they are free. If you are strapped for cash get a few old frames and salvage the tubes. They can be spliced if you know what you are doing. Exhaust tubing comes in a lot of sizes and is comparable to the cheap bike frames. IMHO EMT conduit is not acceptable for anything that will go over five miles an hour.
Elmo
 
Bikeguy Joe

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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I built a set of 5' chopper forks once with two aluminum clotheline props.
First they busted my yayas when they suddenly folded, then my mom busted 'em again when she found out I ruined her poles.
 
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dmar836

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Jun 23, 2009
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MHF,
No I don't feel better. Your question was a no-brainer to those who have built frames and not one I feel challenged to argue. I just tried to put a hard stop to much of the silly suggestions.
I stopped short of calling you stupid because you just asked a question. That's wise - not stupid. Those who encourage conduit builds are, well, maybe a bit inexperienced. There are many "experts" in the anonymity of the internet. You are responsible, however, to sift through for the correct answer(Hint: it's always the harder one). Remember, you might just be getting such engineering advice from a 6th grader with the same enthusiasm I had as a kid - creative but with a lot to learn.
As mentioned, there will always be the advice you want to hear found somewhere on the internet if you search long enough. There are an equal number of sites with video bloopers of failed and injurious hacked creations. Then there are those sites where people have done it the right way, i.e., the hard and usually expensive way. In the end, you ultimately chose which site you want to be on.
JMO. Build on.
Dave
KC
 
B

Board Track Racer

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I spent some time trying to find out the structural properties of EMT,..I can't, but I did find this site offering information on building a geodesic sphere. Also with a quote from this site.

Building an EMT geodesic sphere

"Strength of materials
You won't find much on the web about the strength of conduit, for good reason. A manufacturer of conduit is making it to hold wires, not to be used as structural material. Even if they do know the structural properties, the manufacturer is probably not going to publish the data. However, we can make some educated guesses. It's a galvanized welded steel tube and the alloy and temper are chosen to be quite soft (because you need it to be easily and smoothly bendable without cracking or wrinkling). "

" Watch out for splitting the tube. Choosing where the weld is (if you can find it) before bashing is the way to solve this. The following two pictures show a split in the middle (really bad, when it comes to drilling the hole), and along the side (probably not as big a deal). No matter how you're going to "form" the metal, you probably should allow for a few wasted pieces."
 

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Norman

Norman

LORD VADER Moderator
Jan 16, 2008
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well I guess I'd better go junk my conduit recumbent bike? And the go karts? What about the guy in South Dakota who built is home built airplane out of conduit? Its still flying too! What about the old heath airplanes built out of water pipe with shingle nails for rivets? Wood for a prop?
My airplane built out of foam, wood, and fiberglass? with a vw engine no less? Am I
living on the edge? It also has a wood prop.
Oh well I'm still working on chocolate chip cookies that will last for ever made out of high explosives and baked on enamel.
laff
Norman
use what you want to use as long as your the test pilot.
 
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markeatmark

markeatmark

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Jun 17, 2009
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I build bikes out of conduit all the time. 6' tall 9' tall Big Bikes we ride them in parades. all you need to do is gusset the joints. and have many still on the road. you can make frames out of conduit. fact.
 
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dmar836

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Jun 23, 2009
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Case in point. We aren't talking about a Shriner's parade bike. Motors and public roads add a lot of liability and danger and shame on you for suggesting this is comparing apples to apples.
I'm done with this topic. Build it. Build it heavy. Build it with a great front brake and mash on it. See what it does when not "in a parade". This is why these sites aren't taken as seriously as say motorcycle chassis forums. Just try to keep up there starting with conduit as a baseline. Modulus of elasticity is so far beyond this discussion yet so basic to metal and frame design that it's likely never been mentioned on this forum.
If you look at those suggesting against this, you will see many of them are the one's who have done it right.
Keep us informed and please be safe!
 
markeatmark

markeatmark

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conduit frame is still stronger than a aluminu or a carbon fiber bike frame. the welds are the week point not the tube. the crap bikes at Wall-Mart are thinner than conduit. build what you want take it slow and test your work at low speeds and you will be just fine
 
Kevlarr

Kevlarr

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Jul 22, 2009
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The gauge of the metal doesn't have anything to do with it's tensile strength. You can have aluminum that is stronger then steel, it all depends on what aluminum and what steel.
If you think conduit is stronger than carbon fiber you know nothing about carbon fiber.

I can't bend the frame of my crap Wal-mart bike by hand but I can bend 1" EMT by hand.
 
markeatmark

markeatmark

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Jun 17, 2009
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Kevlarr said:
The gauge of the metal doesn't have anything to do with it's tensile strength. You can have aluminum that is stronger then steel, it all depends on what aluminum and what steel.
If you think conduit is stronger than carbon fiber you know nothing about carbon fiber.

I can't bend the frame of my crap Wal-mart bike by hand but I can bend 1" EMT by hand.
Click to expand...


a steel frame is twice as strong as a carbon fiber. by weight and by size steel is stronger than titanium
you better do some research
 
bairdco

bairdco

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Aug 18, 2009
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my opinion, is i wouldn't do it. does my opinion matter? only to me.

i just broke my frame, which was made in the 60's, out of steel. not from jumping it or thrashing it, but from riding around all day, hitting potholes and manhole covers, and vibrating the heck out of it.

i've broken aluminum frames, cro-moly frames, and steel frames back in my bmx days, and i probably weighed 125lbs. but i wasn't riding them at 30mph+ down the street in traffic.

things are gonna break. that's the way it is. might be your bike, might be you, might be both.

here's a link to some guy that builds crazy bikes out of EMT: AtomicZombie Recumbent, Trike, Chopper, Scooter and Electric Bike Plans

good luck.
 
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