Why 4130 tube?

Richard Lamb wrote in message ...
You know how hard it is to pull 20 pounds off of a bare airframe?

Or a girlfriend?

Richard

Depends on the girl............. one simple comment can do the job -
if your willing to be the recipient of the other reactions as wellG

20 pounds may seem like a lot on a bare airframe but in the grand
scheme it's not really significant. My Aeronca for example lost a LOT
more than that with the change from Linen to Dacron. With the other
modern materials available to us now, that 20 lbs (if that) can be
made up for elsewhere. I know guys that have more than 20 lbs of junk
stashed in their planes that they haven't even looked at for years.

Other than weight - IS - there a reason not to use 1026 DOM? This
assumes of course that the design is based on the slightly lesser
strength and/or has adequate design margins to begins with.

==================
Leon McAtee

"Leon McAtee" wrote in message
m...

Other than weight - IS - there a reason not to use 1026 DOM? This
assumes of course that the design is based on the slightly lesser
strength and/or has adequate design margins to begins with.

I'll never forget the time I machined a new axle stub for a friend's boat
trailer. I bought a blank from the trailer parts company that was made from,
"1020 *Plow* steel". We installed it, lowered the jack and the axle
proceeded to slowly bend under the weight of the boat until the tire hit the
fender.

I bought a chunk of normalized 4130 and turned a new axle stub. He used it
for five years and never had a problem.

'Course this would never happen with that 1000 series steel from XYZ
company.

Rich "Mebbe you could save a buck on the leather jacket and silk scarf" S.

"Rich S." wrote in message ...

'Course this would never happen with that 1000 series steel from XYZ
company.

Rich "Mebbe you could save a buck on the leather jacket and silk scarf" S.

Money saving is not my main motivation. In fact the local rusty stuff
purveyor wants - more - for local 10XX tube than AS+S 4130 W/shipping
would cost. From what I have been able to gleen from the Internet
1026 DOM looses a good bit of strength when welded (normalized state)
but something like 1040 DOM ends up with 92% of the yeild strength of
4130 N after application of fusing heat.

The down side of the 1040 seems to be that post heating is recomended
- the same as 4130 (says one Internet source). Does this mean that
1040 has similar problems with embrittlement in the HAZ as 4130? This
seems kind of odd considering the stuff is originally resistance
welded during fabrication. The same source says nothing about post
heating of 1020.

===================
Leon McAtee

Leon McAtee wrote:

Richard Lamb wrote in message ...
You know how hard it is to pull 20 pounds off of a bare airframe?

Or a girlfriend?

Richard

Depends on the girl............. one simple comment can do the job -
if your willing to be the recipient of the other reactions as wellG

20 pounds may seem like a lot on a bare airframe but in the grand
scheme it's not really significant. My Aeronca for example lost a LOT
more than that with the change from Linen to Dacron. With the other
modern materials available to us now, that 20 lbs (if that) can be
made up for elsewhere. I know guys that have more than 20 lbs of junk
stashed in their planes that they haven't even looked at for years.

Other than weight - IS - there a reason not to use 1026 DOM? This
assumes of course that the design is based on the slightly lesser
strength and/or has adequate design margins to begins with.

==================
Leon McAtee

I think it's the last assumption that won't let me let go here, Leon.
WAS that structure originally designed for mild steel of 4130.


Also, there is a subtlety here that only applies to airplanes.

Building a truss structure with heavier tube probably doesn't ring
bells and wave red flags for you, but it really should.

It's not the actual increase in weight that's the issue, but the
distribution of that weight.

(everybody look blank for a moment and say "huh?")

But wouldn't the increased weight would be evenly distributed?
Very true.

The extra weight in the cockpit section is hardly noticeable
BECAUSE
it's all close to the center of lift.

But.

The longerons, verticals, diags, tail feathers, etc. in the aft section
all weigh more too.

And THAT increased weight can be a real serious BALANCE issue.

(Sorry for the caps, but I get loud when I preach
the Gospel according to Weight and Balance)

Can I get an Amen?


Richard