Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

This is a tech-heavy post dealing with material harnesses and the manufacturing process of fuel lines. This is a heads-up if you're not into that.

I'm working on a fuel shut-off valve project and this question came up.

Does someone know why the fuel line that runs from the gas tank shut-off valve to the firewall (fuel strainer) is made from hard steel?

Typically, the main material hardness options for most types of fluid lines are:
1. Aluminum (soft and hard)
2. Copper (soft and hard)
3. Carbon steel (soft, half-hard, and hard).
4. Stainless steel (varying hardness).

Most car manufacturers stay away from aluminum and copper for fuel lines. In vibrating environments, these materials may work-harden over time, then fatigue and crack.

Based on working (cutting, bending, flaring) with a repop Model A fuel line, it seems to be made from hardened steel. Why hard steel?

The original (seamed) Model A fuel line is also hard.

The first thing I thought of was that there may have been concern that the fuel line may be damaged by the passengers feet. This is possible of course, but the fuel line is fairly high up and mostly out of the way, in my opinion anyway.

If these fuel lines were to be made of annealed (soft) steel instead of hard steel, they would be easier to fabricate, and they would still hold their shape very well over the short distance that these lines run. An annealed steel fuel line would also be easier to install since the tube could then be 'tweaked' into place without specialty tools. Not easy to do with the hard steel line that acts like a spring. So why not annealed steel?

For your reference, most auto parts stores sell annealed steel straight tubes (with flares at each end) for fabricating your own fuel and brake lines.

Its my belief that the original seamed tubes were mostly processed while hot; the seam sealing process required that of course. Tube cutting, bending, and flaring may have also been performed hot. Then the tubes would have been quenched for quicker processing. Through that whole process, the tube material became hardened. I believe the hardness of the original tubes was a RESULT of the manufacturing process, and it was not deliberately hardened. I have no facts to support that this is how the tubes were made, but its logical I think.

When the repop manufacturers reproduced Ford's fuel line, its reasonable to assume that they would have copied as much as possible (including the hardness). However, the modern fuel tubes don't have a seam...the 'seam' process of manufacturing tubes is obsolete. It seems that the repop tubes are hard, but they don't need to be.

I'm looking for input. I made several assumptions which I cannot substantiate.

Is there any reason to not make the fuel lines from annealed steel?

Thanks for your support!
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Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

No comments from anyone?
Is there any reason to not make the fuel lines from annealed steel?

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

I don't have a answer to your questions but why not use Ni-Copp for your fuel lines. Easy to form, rated for brake service.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Likely nobody cares !

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Seriously?? I think it is more likely nobody has an answer.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Some of us do care !! First have you read the recent post about Bundy tube that I started? Originally Bundy "seamed" (rolled) tube was soldered, later it was brazed. When the transition was made I don't know but willing to bet that it was prior to Model A time. Brazing takes red heat. If after braze they were "quenched" that could account for the hardness. However I doubt that the tubes were formed and flared prior to brazing... that would not work as a process step. So, I'm afraid that the tube is what it is, it may be harder than annealed but ... that's the way it is. As for the repop stuff, maybe just chalk it up to either and/or work hardening or Chineasium steel.
Joe B

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Really?
In your world, just because you don't care, that means nobody cares :confused:
Such lack of vision and perception :(

The purpose of my question is actually stated in the first post.
Those who have open minds will see a direction that I'm heading.

I stated in the first post: "This is tech heavy...This is a heads-up if you're not into that (fuel line manufacturing process)". You could have just left, but oh no, you zoomed to the bottom of this thread to make a disparaging remark anyway :mad:
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Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Guten Morgen, that's no reasons to quarrel!


At that time, machine construction was oversized. A great safety factor was built in. In case of doubt a number stronger.

You hardly had to pay attention to the total weight and the material consumption was hardly limited.

Due to the known vibrations and the risk of fire, a fuel steel line was used that was considered to be particularly safe. Because the frequent opening and closing of the often tough fuel tap resulted in additional stress. Especially since at that time pieces of cargo were also loaded on the floor.

There are many other examples. The suspension of the axles, the powerful pedal shafts, oversized crankshaft bearings, thick piston skirt, ...

"Lightweight construction" was unknown in the 30-th automotive industry. It only started gradually with the self-supporting body with sheet skin without a frame.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

No it was not disparaging. Your responses suggest it is not a highlight in our hobby. You were not exactly overwhelmed with responses. No need to get upset because people state the obvious. Calm down.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

I suspect thermal exspansion was a concern when designing long tubes which will be exposed to varying temps and carrying fuel. Brass and Aluminum would not be my first choice. For a short time I used modern fuel hose, and then replaced that with a new steel fuel line. If nothing else . . . I feel safer.

Thermal exspansion is always testing me. As cool weather is upon us, my tudor becomes a leaking @#!$!#@. Last week the radiator started leaking again, and last night the carb started dripping fuel . . . .again. Extensive repairs fail to cure the problems associated with metal and tempurature.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Is there documentation the the lines were made of hard steel? Or have they just age hardened?

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

I read something on the annealing process when spinning brass which may apply. The brass is annealed before starting the spinning process. As work progress it may need to be re-annealed several times as it work hardens. The steel tube may be the same thing. While it starts out bendable as it goes through the bending process it self work hardens. My observations has been that while bending a steel tube, bends easy at first, but not so much to un-bend. Could have something to do with stretching the molecules, so no longer elastic.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

I like how you continue to reinforce the reputation you've created.

Re: Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?
 

Yep, that's my take on it also.

So it seems that the 'hard' state of the original tubes was an unintentional result of the tube forming process. Heating and quenching may have contributed to the hard state of the original tubes as well.

Its interesting that the repop suppliers have elected to deliberately harden the entire tube after forming. I've cut some of these tubes up to reform them...there is no doubt that the repop tubes are full-hard.

Unless someone chimes in with a reasonable response I see no reason why the tubes cannot be made from annealed steel. The only difference in making tubes with todays annealed steel is that after forming, most of the tube remains soft-ish (that's what my samples did anyway).

This solves a key issue with my fuel valve project. I hope to have more good news soon.