How difficult is basic frame fabrication?

[MikeFairbanks]

I'd like to start fabricating low-trikes (basically drift trikes but with drift as an option, not the norm).

Specifically, how would I go about bending the tubing? Wood jigs and a blowtorch?

I was certified 25 years ago in oxy-acetylene welding (up to about an eighth of an inch) and basic arc welding, but most of my skills are long gone.

I'm good mechanically, and have been steadily involved in carpentry for thirty years, so I have basic knowledge.

I want to be cheap, but build some fun trike frames or just experiment. Is this something reasonable for a garage shop, or should I just design a frame and work with a local fabricator?

None of this is serious. I want to build trikes like the Atticus and such (but my own design, not like theirs).

Example: http://www.google.com/imgres?imgurl=http://www.urbantrike.com/wp-content/uploads/2012/05/Atticus-main-428x420.png&imgrefurl=http://www.urbantrike.com/store/products/atticus/&h=420&w=428&sz=148&tbnid=tsZ8AfcDaHpUvM:&tbnh=86&tbnw=88&prev=/search%3Fq%3DAtticus%2Btrike%26tbm%3Disch%26tbo%3Du&zoom=1&q=Atticus+trike&usg=__BkKA10MNfQ57J629NETqw8ion20=&sa=X&ei=pNhhUPnfAZDK9QS4jYGACQ&ved=0CBUQ9QEwAQ

 

[ejay]

I built my own frame, with NO knowledge, with an angle grinder and a borrowed stick welder. It held me for around 1000miles at up to 30mph, though it was heavy (2mm x 40mm box section lol)

With your past experience it should be no problem mate!

Jay

 

[Drunkskunk]

To bend tube you need a tube bender. and to get good bends with a constant radius and without pinching down the inside, you need a mandrel bender. Thats a few hundred bucks used. Not cheap, but not outragiously expensive either.

But depending on your welding skills, you might have an easier time building the first one out of square tube. Its easier to cut, and easier to make joints with basic home tools and basic welding skills. Thats the direction I went with mine. My plan called for round tube, but after a few practice welds, I went with square tube. Its not finnished yet but its a solid frame so far.

 

[dogman dan]

Compared to my worse than a farmers kid welding skills, you got it made. What gets pricy though is the nice fittings, really good stuff for the dropouts, disk mounts, bb housing, etc. Plain stuff not so expensive, better still if cut off of dumpster bikes.

I keep wanting to get a cheap wire feed welder, and give it a whirl. Even just fabricating some killer rear swing arms would be neato. Start making medium longtails out of FS bikes. Add cool stuff, like integrating a bobtail trailer mount and pinchers. Frame ride height adjusted to take a 20" rear wheel of course.

 

[spinningmagnets]

Before welding up a frame, you might consider the option of making up a couple of frames in wood. the frame would be heavy, but they would just be prototypes to establish the posture and make cheap and fast adjustments before welding.

edit: use the steel bottom bracket (BB), drop-outs, and head tube from a salvage bike. I have used an angle-grinder with a thin cutting disc as a tube cutter, as long as eye protection and gloves are used! (yes, I have scars)

"wooden bicycles, lots of pics"
http://endless-sphere.com/forums/viewtopic.php?f=1&t=10697

 

[MikeFairbanks]

Wow, great advice, guys. Thanks. Using junk bikes sounds ideal, and about twelve miles up the road is a lot right out of Sanford and Son, with at least a hundred bikes, not one of them in working order. They'll sell any part for five or ten bucks.

So here's a question: how feasible is connecting tubing using holes and bolts? I'm really just trying to make a prototype low trike for zipping around the neighborhood. It doesn't need too detailed as it won't have any pedals, chain, etc. it will have a basic frame with forks (hub motor on front...20 inch), and some twelve inch wheels in the back. I'm not making it a drift trike, just a fun trike...a large big wheel. It's legal in my town if it's under 20mph. Keep in mind it would be used on our paved golf cart paths that connect every building in our city without mixing with cars.

I'd build it to go about 22mph top speed and just ride around having fun.

 

[chisixer6]

want to bend tubing? for about $170.00 you can a new one from Harbor freight...

http://www.harborfreight.com/tubing-roller-99736.html

Warren B. when he built his bobber chopper, he had a video of this in action...
I'll tried and find it...it's neat.....

here is the build

http://www.recumbents.com/wisil/chopper/default.htm

go down to date 12/04/11 and you will see a demo of the tube roller....

 

[cal3thousand]

Wow, great advice, guys. Thanks. Using junk bikes sounds ideal, and about twelve miles up the road is a lot right out of Sanford and Son, with at least a hundred bikes, not one of them in working order. They'll sell any part for five or ten bucks.

So here's a question: how feasible is connecting tubing using holes and bolts? I'm really just trying to make a prototype low trike for zipping around the neighborhood. It doesn't need too detailed as it won't have any pedals, chain, etc. it will have a basic frame with forks (hub motor on front...20 inch), and some twelve inch wheels in the back. I'm not making it a drift trike, just a fun trike...a large big wheel. It's legal in my town if it's under 20mph. Keep in mind it would be used on our paved golf cart paths that connect every building in our city without mixing with cars.

I'd build it to go about 22mph top speed and just ride around having fun.

Unless you mate the sections perfectly before-hand, the holes and bolts method will yield lots of flex in your frame. vibration will eventually loosen something unless you loctite it.

I bet if you get the design together, you could find someone to make the bends on the cheap. Maybe an exhaust shop can handle small enough tubing

 

[steelmesh]

want to bend tubing? for about $170.00 you can a new one from Harbor freight...

http://www.harborfreight.com/tubing-roller-99736.html

My dreams come true! I really wish I didn't see this =(

 

[Thud]

#1 place for chopping & bike salvage& ideas:

http://www.atomiczombie.com/

this guy does everything with a 4-1/2" grinder, hand files, a hand held drill & a stick welder!
brows the site & get inspired.

 

[Arlo1]

Yeah I am going to build a couple here soon. The way to do it is find a bmx or something similar with a strong front end and chop off what you don't want and weld up a rear end. There is lots of DIY drift trike plans. I think the easy way will be to have dual rear wheels on each side pneumatic rubber with a size you can find a tight fit for some abs or PCB pipe to slide onto.

 

[AussieJester]

Thud organised the harbour frieght bender for me, i built my latest frme out of 4130 chromo using it, gets good
results. Atomic Zombie is a good place to look also check the 'Built From scratch' section at RatRods
you will find some real works of art done by skilled fabricators and also examples of efforts
done by those with less skill but heaps of enthusiasm...

The satisfaction from building your own frame is priceless IMO

KiM

 

[Beachcruzer]

I've been thinking along the same lines. Drift trike with a 2810 9C in a 20" wheel (just got the motor yesterday) and 24s lipo. Yeehaa! The chopped BMX front end/square-tube rear method seems pretty simple. This kid did it in a day and a half for about $40. Now, put a controller and a layer of lipo under the seat, and hold on to your culo.

[youtube]GoqhZAgZ6vA[/youtube].

 

[dogman dan]

Gotta be easier to hack a bmx than start from scratch.

Once you got your wire feed welder, and a grinder, cutting and re welding would likely be even quicker than working out a bolt together. Or get several frames, try this with one, that with the other. You won't be wasting time putting anything on em besides brakes.

For light tubing, couldn't you use an electricians conduit bender? Especially if using conduit to make cheap prototypes not intended to last?

 

[MikeFairbanks]

I think I'll try the hacked BMX route.

 

[REdiculous]

Remember to totally strip the paint. The last bike I cut up..I spent more time stripping paint than anything else.

Oh, you might think about picking up a busted old shopping cart. Cut and reconfigure. Scrap the remainder.

 

[Sancho's Horse]

Bending reliably without a tube bender is possible but requires a lot of set-up, and if you go that route pack your tubes full of sand to spread out the stress, and avoid a pinch.

The way of the dumpster diver is an ancient art for a reason. It works. If you do bring some Fred Sanford to the table, learning some brazing could prove invaluable. Not too difficult. Patient grinding, tight material positioning, but you get the possibility of lugging, able to bring together dissimilar materials, and welds have good attributes while undergoing vibration or repeated stress. If you have done oxy welding you are almost there - skills wise anyways.

 

[steelmesh]

Bending reliably without a tube bender is possible but requires a lot of set-up, and if you go that route pack your tubes full of sand to spread out the stress, and avoid a pinch.

The way of the dumpster diver is an ancient art for a reason. It works. If you do bring some Fred Sanford to the table, learning some brazing could prove invaluable. Not too difficult. Patient grinding, tight material positioning, but you get the possibility of lugging, able to bring together dissimilar materials, and welds have good attributes while undergoing vibration or repeated stress. If you have done oxy welding you are almost there - skills wise anyways.

In addition to Sancho remark on sand filled. I was in Formula SAE at the university when studying for MBA for a semester (students fabricate and race a 20-21mm restricted cart), they said they bent the tubes by filling them with sand and using a table with pins to bend around, it was a gorilla like effort, chromemoly tube. They passed inspection. If you're going to sell these on the street, this would not be a good idea, but for custom "off-road" use, you can do whatever you want with your life. I would recommend not letting friends ride it unless you want to take full responsibility for their life, so you better be damn sure its quality.