4130 Tube Steel Alternatives?

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

rkirk77

Well-Known Member
Joined
Apr 14, 2014
Messages
65
Location
Sarnia, Ontario Canada
What alternative steel grades can be used for building a Pietenpol Air Camper fuselage, and how would much would I have to compensate the tube thickness?
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
10,302
Location
CT, USA
As with everything in aviation, "it depends". Each component is different. Where the limiting factor is tube compression bucklilng, it wouldn't matter as the tube's strength depends on its elasticity, not ultimate strength. For tension or bearing loads, the alloy's strength does matter and you'd have to allow for the replacement material's reduced strength.

Often, however (and I'm not saying it the case here; I don't know) older prewar designs were designed for lower strength tubing like 1025. Later, 4130 became commonly available and relatively inexpensive so manufacturers switched to that even though its extra strength may not have been necessary. The Pietenpol is an older design that may have been designed for lower grade steel but the plans you're building from may been altered later to use (and require) 4130's greater strength.

Whatever you do, it should be specified as seamless (not welded) tubing.

Dana
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
8,126
Location
Rocky Mountains
The plans call for SAE 1025.
The problem I had years ago when I too was investigating the use of this grade of steel rather than 4130 is that the only way to get a reasonable quantity was to order it through the local steel supplier. They could get it but the cost was 3 times what I could get the same size from Aircraft Spruce - including shipping!

You might have better luck in a large city?
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
10,302
Location
CT, USA
The "common SAE 1020" tubing is likely welded DOM, not seamless.

Dana
 

BoKu

Pundit
HBA Supporter
Joined
Aug 15, 2013
Messages
2,999
Location
Western US
See if you can find 1/2" .035" 1020 that is any cheaper than 4130 from Aircraft Spruce and post it here please.
Also, note that 4130 prices at Wicks Aircraft are currently a fair bit below ACSs. I saved about 20% on a big steel tubing order a few weeks ago.

But BBerson's point is a good one: The relatively high volume of trade in 4130 probably makes it less expensive than 1020, even though it is stronger.

Thanks, Bob K.
 

cheapracer

Well-Known Member
Log Member
Joined
Sep 8, 2013
Messages
6,421
Location
Australian
1020 is fine, DOM or seamed.

The only difference it will make is if the yield is exceeded if you crash it (where DOM is superior), that's a personal choice you will have to make otherwise the actual strength of the frame isn't changed.

BTW, 4130 is very much an American affair, most race cars and off road racers for example in the rest of the world are built with 1018/1020 DOM and if the impact is enough to exceed it's yield then your chances of walking away were already well surpassed.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,471
Location
Port Townsend WA
Race car roll cages are typical 1/8" x 1-3/4". Actually, a lower yield can be good in a crash structure.
I doubt race cars use much 1/2" x .035", however. Usually the rules require a specified size and alloy.

4130 is commonly called "alloy" and is "air hardening". That means the post weld strength is very good.
Ordinary 1020 cold rolled carbon steel (not alloy) is soft post weld.
Having said that, I would still use 1025 1/2"x .035" if I could get it. Because in most cases it doesn't matter if the post weld strength is less.
 

cheapracer

Well-Known Member
Log Member
Joined
Sep 8, 2013
Messages
6,421
Location
Australian
Race car roll cages are typical 1/8" x 1-3/4". Actually, a lower yield can be good in a crash structure.
I doubt race cars use much 1/2" x .035", however. Usually the rules require a specified size and alloy.
Nope, go read the rules, SCCA website is the easiest. By the way, you can use 1010 DOM under FIA/SCCA rules as well.

Sports cars such as Donkervoorts and Caterhams are constructed typically from 1" x 0.040 - 0.060" seamed ERW box tube and they take a hell of a lot more pounding than any aircraft.

4130 is commonly called "alloy"
All steels are "alloy" as are most metals.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,471
Location
Port Townsend WA
Nope, go read the rules, SCCA website is the easiest. By the way, you can use 1010 DOM under FIA/SCCA rules as well.

Sports cars such as Donkervoorts and Caterhams are constructed typically from 1" x 0.040 - 0.060" seamed ERW box tube and they take a hell of a lot more pounding than any aircraft.



All steels are "alloy" as are most metals.
Of course....

I was obviously referring to common industry use of the term. (Meaning expensive alloys)

Again, the needed 1/2"x .035" thick or less cold rolled 1020 is not readily available here. Even .035" is too thick for my aircraft.
I actually need .018" but can't find it.

I found this in the 909 page scca rule book, which confirms my comment about use of the words "alloy" and " mild steel":
TUBING
  1. Seamless or DOM mild steel tubing (SAE 1020 or 1025 recom-mended) or alloy steel tubing (SAE 4130) must be used for allroll cage structures. Alloy and mild steel tubing may not bemixed. ERW tubing is not allowed.
  2. The following table shows the minimum allowed tubing outerdiameter and wall thickness by vehicle weight:
 
Last edited:

Turd Ferguson

Well-Known Member
HBA Supporter
Joined
Mar 13, 2008
Messages
5,875
Location
Upper midwest in a house
Also, note that 4130 prices at Wicks Aircraft are currently a fair bit below ACSs. I saved about 20% on a big steel tubing order a few weeks ago.
The Chassis Shop sells 4130- 1/2" x .035" for ~$.50/ft. Compare that price to ACS or Wicks ridiculously marked up price of > $2.00/ft for the same thing. Plus the nearest outlet is a 1hr drive for me. No cutting/crating/shipping charges.
 

BJC

Well-Known Member
HBA Supporter
Joined
Oct 7, 2013
Messages
14,277
Location
97FL, Florida, USA
The Chassis Shop sells 4130- 1/2" x .035" for ~$.50/ft. Compare that price to ACS or Wicks ridiculously marked up price of > $2.00/ft for the same thing. Plus the nearest outlet is a 1hr drive for me. No cutting/crating/shipping charges.
This might be a different Chassis Shop, but it is priced per foot :

Your shopping cart with The Chassis Shop



BJC
 
Top