Frame materials

motorhedfred · Sep 3, 2009

After looking and looking at exsisting bicycle frame designs new and old, I've come to the conclusion that there must not be an available frame out there that looks convincingly like an old board tracker. If you mix in enough visual cues, you can get close....perhaps at casual glance passable, but not really.

I'm considering building a frame from scratch and I wondering if anyone here has any hands on experience with EMT (electrical metal tubing) i.e. conduit.

It seems fairly heavy gauge, relatively easy to bend, inexpensive and readily availible. I know it's not very good on a strength to weight ratio compared to CroMo and well design aluminum, but without the proper tools to bend, shape and weld those kind of materials, EMT might be a good alternative for home builders.

Here's a couple of links I turned up....

Frame Building - Atomic Zombie™ Extreme Machines Builder's Forum

Don Boose builds an EconBent

The second link is for a recumbent bike that actually uses exhaust tubing for the main backbone.

MHF

Kevlarr · Sep 3, 2009

Problem with EMT is it is relatively easy to bend. Main reason it doesn't weld "worth poop" is that it's zinc plated and it's usually has a plastic inner coating to make it easier to pull wire though.

Check out your local yellow pages for steel suppliers or welding shops and stop by to take a look at what they have. The local welding shop here has a nice stock of scrap steel that they're willing sell by the pound.

There are several ways to bend tubing without a bender too. One is to fill the tube with sand, cap the ends and bend over something close to the radius you're looking for.

joewlms3 · Sep 3, 2009

you can bend the cromo tubes on conduit tools
ive bent schedule 80 1" ss pipe with a conduit bender

get a piece of emt and a bicycle frame smack both with a hammer see which is stronger

i agree emt no weld good at all

ive sourced tubing from this company for the build im working on now
4130 ALLOY STEEL ROUND SEAMLESS from Aircraft Spruce
and found it very convenient that they have lots of sizes and thicknesses and they cut it to your order
also the common sizes are cheaper prices

foureasy · Sep 3, 2009

absolutely not, not even without a motor

MotorbikeMike · Sep 3, 2009

Hi Fred, I do have, in stock, some VERY nice drop-loop motorbike frames with Whizzer motor mounts built right in. Here is a pic of an old prototype that I put an EZ Motorbike system in.

Mike

joewlms3 · Sep 4, 2009

yeah i wouldnt smash a frame on purpose either i guess shouldve said and a piece of similar thickness 4130 tubing

aricarmon · Sep 4, 2009

hey im almost done with my bike and i was in the exact same position you are in now, i used galvanized steel, i bought it at the orchard supply down the street because i could not find for the life of me a metal supply shop around my area and when i looked it up it was way too expensive. so i asked the guy that worked there and he told me that it all it was was a steel pipe that had been galvanized (not DOM) and that the only thing to consider was that of you weld galvanized steel it creates a toxic gas but it would be fine if you ground down the area to be welded and welded in an open area, i had no problems whatsoever, and on top of that i used a large 1" conduit pipe bender to bend it, it was hard and required some muscle and help from my friend cuz im pretty skinny but it worked fine and i got some pretty smooth bends believe it or not by bending areas and moving down about 6 inches, you cant tell one bit and best of all i didnt have to buy a $600 pipe roller, i will postt a couple pictures so you can see what i am talking about, oh ya and dont use conduit, it wont work, trust me i considered it before i found the steel and they r pretty close in price, they were actually right next to eachother in the aisle, well i hope this helped you

motorhedfred · Sep 5, 2009

Guys, I'm always on a tight budget. There's 2 reasons I'm exploring the EMT route and I do actually have some experience making things with the stuff. So to those who flatly say "no way"....do you have any experience working with and making things with EMT ?
My reasons are...
A. Budget
B. Contributing something worthwhile for public consumption

Aric, I think you get where I'm coming from and I'll look into the stuff you used. You said you got it from an orchard supply place....do you remember what it's made for ?

For those wanting to spin this thread into an opportunity to sell a product.....well, kinda makes me not want to do business with you.

MHF

Kevlarr · Sep 5, 2009

It's water pipe look at the threads on one end.

MotorbikeMike · Sep 5, 2009

Motorhed, you said there was no frame made, that is flatly not true,which is why I made a comment. In addition I am a retired Electrician, and I can assure you that EMT is a poor material for a motorbike, or even ridable bicycle frame.

EMT bends too easily, and by the time you get the zinc off of the steel there is not enuf metal for a good weld, and yes I have made welded projects from EMT but not bicycle frames. My frames are DOM and Normalized Chromoly, BUT in the past I bought steel tubuing at a Metal Shop, and have added new bars to bicycle frames with it. I have also use "Black Iron" gas pipe for some projects and it works ok.

Do business with whomever you wish, but please keep insults to yourself, this is a family board, and respect is the order of the day here.

EMT is not a good material to sustain weight, welding, vibration, nor stress, and is not recommended by any of the builders that I know, motorized or pedal versions.

Select a better material, and you will be happy for it later.

Mike

Ilikeabikea · Sep 5, 2009

Norman and I have made go karts out of emt. It's not that hard to weld. We ran the dickens out of em and never had any structural failures. I flipped and rolled my kart and it didn't bend or break. I broke and had to go to the ER and get some xrays. I wouldn't hesitate to use it to build a bike frame. Oh yea I am using it to build my Board Tracker. Just my opinion and my experience.............

motorhedfred · Sep 5, 2009

My apologies, my reply was rather harsh. I tend to champion my causes too strongly sometimes. Must be all those years of being a union steward.

MHF

foureasy · Sep 6, 2009

have you ever priced out seamed tubing? it's like a dollar a foot for .120 wall 1".

roxrcool · Sep 6, 2009

motorhedfred said:
My reasons are...
A. Budget
B. Contributing something worthwhile for public consumption

MHF

please tell me you're not thinking of selling these to someone......

geeksquid · Sep 6, 2009

Ilikeabikea said:
Norman and I have made go karts out of emt. It's not that hard to weld. We ran the dickens out of em and never had any structural failures. I flipped and rolled my kart and it didn't bend or break. I broke and had to go to the ER and get some xrays. I wouldn't hesitate to use it to build a bike frame. Oh yea I am using it to build my Board Tracker. Just my opinion and my experience.............

I built a mini bike from EMT when I was a kid. No bending, I just welded straight pieces together that I cut with a hacksaw. Used a Clinton engine. I used a bicycle fork. Just welded the tube, fork and all onto the emt tubing. The frame never bent but I blew a few motors and ate a lot of dirt. People do actually make go karts from PVC pipe, so EMT will work. It's good for the poor jerk who has no money and isn't making a commercial product. I still can't bend pipe because to practice, you have to waste a lot of pipe.

geeksquid · Sep 6, 2009

MotorbikeMike said:
Hi Fred, I do have, in stock, some VERY nice drop-loop motorbike frames with Whizzer motor mounts built right in. Here is a pic of an old prototype that I put an EZ Motorbike system in.

Mike

Those antique type frames you have are my favorite shape for bike frames. If I had the bucks to buy that type frame, that would be the only way to go. Total class.

Kevlarr · Sep 6, 2009

Difference in building a mini-bike or a go cart frame is you're building what is basically a ladder frame, ie. two frames joined with cross bracing and triangulation to gain the needed rigidity. A bike frame built on a single plane has to get all it's strength out of just 3 tubes and you have to trust those tubes to not flex, bend, twist or break. Add the vibration of a motor and you're dealing with metal fatigue as well.

If you're dead set on building with emt make sure you have good health and life insurance because you're going to need it.

:edit:

Here's a good test, go ahead and build your frame, lay it between to saw horses and stand on it. If the frame folds up it's not a good idea to ride it.

Ilikeabikea · Sep 6, 2009

Here's a good test, go ahead and build your frame, lay it between to saw horses and stand on it. If the frame folds up it's not a good idea to ride it.

When would you put that kind of load on a bicycle frame? I think I would be more worried about the circumstance it would take to put that kind of load on a bike than the bike folding up. But I went out stood on mine and it didn't even come close to bending. But like I stated in my first post on this thread. This is only my opinion and my experience. I would never recommend someone build a bike with conduit, nor would I recommend that they don't. Just my 2 cents.........................

aricarmon · Sep 7, 2009

i see where u r coming from, i havent worked with emt but from what little i know is its not necessarily used for support but as a surrounding encasement i guess you would say for electrical wire and it seems like it just bends too easy, granted, these arent extreme motorcycles that go off jumps or anything but i would say it might have the possibility to warp and bend slightly over time and on top of that your welds might break because i dont think its steel 100%, but the galvanized steel is stronger than the bikes steel that i chopped up for parts, and im telling you i did this with the most limited tools, space, and especially money that i could. one thing i forgot to mention in the
ast post was though that when you weld the pipes together, you should bevel the edges in order for the weld to sink in and really create a good bond, just a little trick i learned

Bikeguy Joe · Sep 7, 2009

I'll jump in here and say this- You can build a bike frame or an aircraft structure, bridge, ect out of just about anything IF YOU KNOW WHAT YOU ARE DOING.

Get at least a rudimentary understanding of structural engineering before you bust you yaya's on some "home-made contraption".

Frame materials

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Godfather of Motorized Bicycles