Rack Building
 

I hope this is the right place to ask this...

I am interested in building my own front and rear racks. I have access to bending equipment and 1/4" steel round bar is cheap. What method would I be best to use weld the bars together?

Is this a job for a real welder or can this be brazed or soldered? Excuse my ignorance, my experience is with sweating plumbing and soldering electronics.

You should do it by brazing! There is a good set of articles here.

I've done a rather craptacular job (picture here) with crappy coiled brake-line tubing, a crappy bender (both false economies), a propane torch and flux coated bronze. I have better tubing, a good bender and some regular bronze on it's way!

I would recomend tubing. There are a bunch of options that have been discussed here already. Bar is heavy and it is more difficult to weld to full strength. Not that full strength would be required.

Yeah, don't use solid bar! Get some 3/8" or 5/16" .035" wall 4130 tubing from aircraftspruce.com or wicksaircraft.com, a decent mandrel-based bender, and brass-braze it up! It's a really good first project if you're interested in framebuilding.

Framebuilding is my ultimate goal. I figured i'd do well to start with a smaller project like this. Plus for the prices they charge for a decent rack at Velo-Orange or Rivendell I can buy a Torch, Fuel, and a bender like this http://www.harborfreight.com/cpi/cta...emnumber=99826 for around the same amount.

I know thats not a top-of-the-line bender, but do you guys think it's good enough? Can you suggest one?

I did some reading last night and It sounds like I'd be best off with a MAPP torch rather than propane. Does that sound right?

that bender seems fairly expensive, although I might try it if I can't find a swagelock on ebay. HF has the worst search function, I have looked through their tubing benders a couple of times, and that one never came up.

As far as torches go, lots of people report success with MAPP, but I think it's a waste of money. I tend to use a lot of heat, so MAPP drives me nuts. I think beginners tend to concentrate the heat in one place, so MAPP actually works better than O/A.

I'm a complete beginner here, so any suggestions for tools would be much appreciated.

Would I be ok to go with a tube bender like this and save a bunch of money?
http://www.northerntool.com/webapp/w...3976_200353976


I've read that MAPP gas is expensive, Am I better off to use Propane? Oxy/Acetylene (that seems expensive and kinda dangerous)?


Also I've read that both Silver and Brass brazing are viable methods. Which would you guys recommend?

I ordered this bender, upgrade from a 10$ one which kinked more then bent. Seems good as far as I can tell, and the price is reasonable.

I'm really a novice too, but it seems a propane torch is fine for racks since the work area is small enough: brass melted quickly. I'm sure silver would work but brass is cheaper.

BTW (no mean to hijack), for my next project I'll put some vent holes near the joints. Is it OK to plug them with solder instead of brass?

EDIT: I tried the bender you showed it worked quite well, but only does up to 90degs. There is a 180deg one too.

Thanks! That bender looks nicer than the one I linked. I've already got a propane torch and plenty of Propane.

Maybe just some tubing, solder, flux and this bender is all I need to make an attempt.

**edit**

tuz, that rack isn't bad at all. If my first try looks like that I'll be fairly pleased with myself.

I just bought a O/A torch, haven't told my wife it's going to cost another $400 for regulators and tanks. I don't know how much more dangerous O/A is than propane. Get the air/fuel mixture right, and any gas makes a big boom.

I think the best bender there is this one:

http://www.aircraftspruce.com/catalo...ges/464-fh.php

Mostly those benders are for bending soft materials like copper. The first Harbour freight looks sturdy, but I don't see how it really works. Any decent bender has a following die that is co-axial with the die one is forming the tubing over.

The second harbour freight bender is a cheap version of the Ridgid model, and the Ridgid is strong enough to bend rack tubing, but no longer made.

The die cast aluminum bender from AS is probably not going to hold up long bending 4130. They sell 4130, so you could at least ask. Presumably there is a reason they are selling the heavier version also.

I adapted a Princess auto bender and am very happy with it, but one needs a lathe, and the bender was medium expensive so most people would probably choose a different route. I started with something similar to this one, and all you do is alter the dies so that the round dies have a groove in them the size of the tubing you want to bend. I actually used weldable sprocket hubs for the die stock, and left the rollers intact.

This one looks like it might be tough enough, all steel, coaxial, and long handles as though they expect you to use some force with it:

http://www.harborfreight.com/cpi/cta...emnumber=98612

The radius of the bend still needs to be correct for your intended use, with the style I made one can vary the radius quite a bit.

In my experience propane is not better than mapp. MAPP is hotter, and that is critical. The main problem with either is the heat transfer is too slow. Either flame is hot enough to melt the braze, but the heat transfer is too slow for it to work properly. The flux tends to char up, and the tubing tends to get red hot because one needs that kind of heat to make the brazing work. It is odd because red hot is nearly 1500F, while the silver has a melting point considerably lower, but the propane or MAPP just can't get the heat up enough to really work it. You will notice the hotter the flame and the smaller the parts the better it works. With 4130, the red heat is not a problem, it isn't supposed to be done that way, but it won't harm anything. With AO at about 3x the temp the main issue is not melting the tubing. Even so, big enough parts require pre-heating. With a much hotter flame you can kick the temp up in a smaller area, before it has a time to conduct all over the place.

I wouldn't use AO in a home shop. It is a very odd animal, a fundamentally unstable gas at the storage pressures unless it is handled properly. I am using PO, but since I don't have AO, I don't know what I am missing.

Cool thread! Add me to the list of framebuilder wannabes practicing on racks. I`ve built several racks and a few stems already- I`ll post some pics when I get home. Tuz, I think your rack looks allright too. Did you ever clean it up?

I`ve done all mine at work so far. I have OA torch, tanks, and regs at home, but still need a vise, bender, and small welding tip (I only have a cutting body) in order to start working there. At work, we have two similar type benders, dedpending on the tubing size. Some sizes are an older version of the Imperial-Eastman one in Peter Pan`s Aircraft Spruce link, other sizes are a very similar Rigid (looks nothing like the HF ones). They both work great and they`re both out of my price range- I`ve looked at some of the ones you guys mentioned here, others are new to me. That Imperial triple size one and the big single size HF ones are pretty tempting.

I did my first rack with solid aluminum, all the later ones were with 8mm and 10 mm hydraulic line that was surplus from an equipment installation here a few years ago. They both have 1mm wall thickness. I`d like to try with .035 4130 one o fthese days. Can somebody who`s used both hydraulic tubing and 4130 comment on how the cromo bends in comparison to the hydraulic line? I imagine it`ll take more force, but I don`t know there`s anything else different. I`d hate to pay that kind of money and destroy the stock.

A rack is agreat project! Spend time thinking of what you want it to be for you, there is alot of room here for customization!!! A rack that fits without any adjustable brackets has that "trick" factor!

some thoughts:

-If you go with the brakeline/hydraulic tubing, remember to sand off any galvanized/zinc from the areas you'll be heating, at brazing temps, the zinc burns off and the fumes are toxic.. not to mention it will contaminate the joints.
-No matter what tube you use, the area should be CLEAN!! I sand, then wipe w/alcohol.
-Flux liberally.
-Silver rod flows at a few hundred degrees lower temp than brass, if you can find it cheap or can afford it, I'd say go with silver, its a bit easier, flows better.
-Get a file or two of the diameter of your tubing so you can fishmouth the tubes into eachother. Braze will not fill gaps.. 1/32 maybe max. Spend time getting them to fit right. It will make brazing the joints much easier.

have fun, post pics!!!
~Steve

These were my first projects. I TIG welded them because that`s what I knew and I hadn`t learned to braze yet. The bolted together on on my mtb was my first. It hooks to a mount on the seatpost and has a single pair of struts, the idea being to let it pivot when I raised or lowered the saddle. In theory, it should work- in practice I can`t move the seatpost without twisting it a little and the rack won`t let me do that. It`s the only aluminum one I`ve done (just the platform). The stem is kind of funky too because since I didn`t know how to braze the binder clamps on I had to machine away the unwanted metal the best I could.

I learned to braze through practice and the internet and I much prefer it to welding now- it looks nicer, it`s easier to stick itsy bitsy pieces together, and it`s fun (I really don`t enjoy welding). The suspension fork rack was the first I brazed, then I brazed a modified copy of my commuter basket for my sister in law, the "rando" rack is the most recent. The funky stem here is fully adjustable- I did it that way first to dial in the height and reach, then made a fixed one, which is off getting powder coated currently. Next rack will probably be a touring rack for the same bike.

That is wicked rodar! What sort of jig did you use for the stem? And is it for a threaded fork? I might give it a try one day :)

Thanks for the compliment. I cleaned it up a bit. The joints were messy because I used a flux coated rod... bronze flowed everywhere!

"Can somebody who`s used both hydraulic tubing and 4130 comment on how the cromo bends in comparison to the hydraulic line? I imagine it`ll take more force, but I don`t know there`s anything else different. I`d hate to pay that kind of money and destroy the stock."

I find stainless is fairly hard to bend also. 4130 bends very nicely in the .035 wall size. As long as it is supported and the wall is thick enough not to wrinkle, then it is pretty easy to bend. The bad thing about 4130 is that it needs some kind of protective coating. I used powdercoat, which is pretty expensive. If stainless has been working for you with it's far lower yield strength, then I would be tempted to stick with it. I wouldn't use a zinc plated line at all.

Nice racks!

Tuz- yeah, it`s a quill type for a threaded fork. I don`t use much in the line of jigs, but to be honest I make the hard part (the clamping part) in a machine shop, first a lathe, then to a Bridgeport, braze, then back to the lathe for the final ID and part it off. The wedge and the angle on the bottom of the upright tube are also cut on the mill. If I didn`t have access to the cool toys, I don`t know how I`d do the stems- I probably wouldn`t mess with them. The racks are more hand work- very similar to the way you did yours, I`m sure. And I don`t think there`s a way to get around the initial mess from the flux. It always looks like hell until you get it cleaned up. How did you mount your rack to keep it from pivoting? Another arm from the middle down to the brake/fender mount hole?

Thanks, PeterPan. I love the look of brushed stainless and considered using it for a while while I was still TIGging, but since I went to brazing I gave up on that idea. I know it can be silver brazed, but my silver work leaves a lot to be desired and practicing is so expensive I think I`ll just stick with bronze wherever possible. Good to hear 4130 behaves well- I`ve just about used up my suply of hydraulic tubing and I think cromo is the route I want to go now. BTW, the hydraulic line I use isn`t galvanized but it has some kind of additive (lead?) for ductility that makes it a booger to weld. Still brazed fine.
OT: PeterPan, I run into your posts from time to time in different subforums and it sounds like you do a lot of different handywork. Have you ever built yourself any frames? Just wondering.

O/P brazed? That means with oxygen from a tank and regulator, or could that also be gas oxygenated by venturi system like in a plumbers acetylene torch?
And I`m surprised that you bevel so much for a braze. I always thought that butting two pieces by brazing was best with as little gap as possible and the most possible "almost contact" between the two pieces of base metal. Is my conception out of whack? When I braze other than filets, I usually just break the edges a little to let the filler flow easilly into the joint and try to have the two pieces of base pretty much together. Is that thte wrong way to go about it?

Inspiring posts. Can't wait to receive my spruce order. Rodar here is the rack set up. More pics on the blog but I'm kinda ashamed of the thing. Bad bends and joints, not parallel etc...

Originally Posted by Cycleops>
"Now on the positives. It was a lot of fun, and I think I know how to make a better rack!"

Well, there ya go Tuz. If you still don`t like your rack, read your own blog post and see what you had to build it with and what kind of experience level you had going into it. Considering the whole situation, as long as you were able to mount the thing up and could carry a lunch bag twice around the block, it was a success. You won! And the next one will be miles ahead.

Papa, your talking about Oxy mapp. vs Oxy propane? In the quotes I was refering to the berzomatic torch with Mapp gas vs, the berzo torch with propane. With oxygen it's all good.

"Thanks, PeterPan. I love the look of brushed stainless and considered using it for a while while I was still TIGging, but since I went to brazing I gave up on that idea. I know it can be silver brazed, but my silver work leaves a lot to be desired and practicing is so expensive I think I`ll just stick with bronze wherever possible."

I bought about 2 pounds of 45% silver off ebay, forget what I paid, but it wasn't that big a dent, and it is all safety silv, no cadmium. Not to suggest you should move away from brass. Part of my interest is playing with cheap home shop alternatives for hobbyists, and silver is one of those options, at least as far as non-oxy torches are concerned.

"OT: PeterPan, I run into your posts from time to time in different subforums and it sounds like you do a lot of different handywork. Have you ever built yourself any frames? Just wondering."

I haven't built one over the last year because I have been working on some fixtures and otherwise not spending much money. The current frame I am working on is a Rohloff expedition tourer, but I don't have all the parts yet, and I am not going to make it up until I finish the wheels... and the frame jig. I sold all my bikes last fall to finance the project but then I kinda freaked when the financial crise hit and the Canadian dollar tanked. I spent the war chest on family stuff.

I see. I use a plumbers propane torch. Can you get small tips for those?

"I see. I use a plumbers propane torch. Can you get small tips for those?"

It is a different system. Papa is talking Oxy/fuel torches that mix pure oxygen with the fuel gas before the mix exits the nozzle and is ignited. Tip size controls the size of the stream of mixed gasses that exits the torch, and therefor is one element in controlling how much heat one is using. Other elements, include the fuel gas, the mix with oxygen, the total pressure, etc...

You are probably using a naturaly aspirated jet ejector burner. Most of these use a nozzle that is burried in a tube where the mix with atmospheric air occurs. With these burners the fuel gas is propelled through the nozzle, where it mixes in the tube with atmospheric air and 4-10 inches latter there is ignition in the burner flair. There are examples of this type of burner that do have accessory burnner tips that can be inserted into the burner, but they are not used in the readily available commercial torches, and tend to require a large tank like those that come with a BBQ.

Papa, can you provide more info on your use of the Devilbiss 505DS oxygen concentrator? I have never heard of this being done with a torch. How well does it work compared to a compressed source?