Streamline tubing 2" x 0.89" x 0.049"

[Luke B]

Hello all,

I am having real trouble finding a stockist in the UK,

Please help!!

Needs to be 4130 steel.

Thanks

[Genghis the Engineer]

What do you mean by "streamline tubing"?

Your specification is written a bit odd, but it sounds like you probably want 7/8" O/D 4130 chrome-moly seamless tubing at 0.049" wall thickness. You can buy that from LAS Aerospace (http://www.lasaero.com/site/products/article?id=Z01NFVB05) at £3.66/foot + VAT

If you need a shorter length for an aircraft application, the best bet is to get somebody to turn it to length on a lathe - any machine shop can do that for you.

G

[Luke B]

Thanks for reply, this is what I need.

http://i54.tinypic.com/ezplau.jpg

[Genghis the Engineer]

I think you'll probably need to buy it from Aircraft Spruce (http://www.aircraftspruce.com/catalog/mepages/4130streamline.php); last I ordered something from them, they charged me about $8 postage for a small item, and it arrived in about 10 days. No reason to believe that you'd be treated differently.

G

[Luke B]

Great thanks. I will try them.

[Genghis the Engineer]

What are you building by the way?

G

[Luke B]

Good question!

Rear wing struts for this
http://i52.tinypic.com/2wekubl.jpg

[Genghis the Engineer]

Negative lift!

You might find it is easier to use circular section steel tube, sheathed with aerofoil section tube - either in 4130 or a 6000 series aluminium alloy. Theoretically, you shouldn't put aluminium alloy and steel onto each other like that - but realistically, I don't think that vehicle's going to last long enough for corrosion to be a significant problem.

Incidentally, why 4130 in that application? It's a relatively heavy material and I'd have thought that aluminium alloy components would be lighter whilst strong enough on a short wing strut. In a strut, the critical component is buckling strength, not UTS, which in turn is a function of Youngs modulus, so a suitably hardened aluminium alloy should be fine.

G

[Luke B]

We want to remake the struts also to move the wing further back and with different mounting points too.

4130 is standard for parts like this in this application. I'd be very nervous using aluminium for a part 3+foot long.

We can get hold of titanium? worth looking at?

[Genghis the Engineer]

What does your stress analysis say? I wouldn't design a component like that without analysing the loads and load paths. On an aeroplane we'd use a safety factor of 1.5 and Rf>1 (say >1.3 if you're proving on simple analysis), but on a car I think a safety factor of about 3 would be more normal.

At risk of teaching you how to suck eggs, I think I'd work a basic aerofoil analysis to determine worst case force, resolve that into components along and perpendicular to your struts, and almost certainly the critical failure component will be the Euler buckling load case. That will be a Pi^2.E.I/L^2, so a bigger section strut material, a more rigid alloy, or a shorter unsupported section will be strongest - in other words, if it's not strong enough, introduce a lightweight jury strut like many aeroplanes do. But, tensile strength (the main reason usually for using steel) is pretty much irrelevant - it's all about stiffness, strut length and section diameter.

G

[Airstripflyer]

Have you tried PFA Metals? They advertise it on their website.

[Genghis the Engineer]

Steel has 3x higher modulus of elasticity, so if you don't want to (or can't) increase the cross section it can be the better choice in a buckling critical application. Aluminum is better if you have no non-structural constraints.

The old dodge for increasing critical buckling load for small aircraft wing struts is to insert a wood filler inside. Steve Wittman would be proud of you ;)

Okay I admit, I had to look that up!

A high temper aluminium alloy gives E~70x10^9 N/m^2

4130 gives you E~200x10^9 N/m^2

Titanium alloys are around E~105x10^9 N/m^2


So yes, steel does look to be substantially the better material for the job in terms of cross sectional area.

Looking at density, 4130 gives an SG of 8.0 and 6061 an SG of 2.7.

So Young's modulus has a factor of 2.85:1 steel:Al, and density a factor of 2.96:1 steel:Al.

Weight for weight, there's basically nothing in it. But since steel is cheaper, and also will give you the smaller cross section for the same buckling strength (and thus less drag) that seems to come out best.


Titanium alloys come out with 50% better bucking strength than aluminium alloys, but 67% greater density. So, of the three, it's the least weight efficient for the job.

G

[Mark 1]

Wicks are also a stockist. Have a look at Wicks Aircraft Supply (http://www.wicksaircraft.com/catalog/product_cat.php/subid=10345/index.html) for something almost to your spec.

[Charles E Taylor]

For 4130

Dillsburg Aero has no Website but the very best prices on 4130 Steel Tubing and Sheet

Phone # 717-432-4589 ask for Charlie Vogelsong
114 Sawmill Rd.
Dillsburg, Pa


Charlie Vogelsong and Dillsburg Aero (http://airbum.com/articles/ArticleDillsburgAero.html)



You won't be dissapointed.





Charlie, (A different Charlie!)

[Twinnshock]

Quote "Have you tried PFA Metals? They advertise it on their website."

PFA Metals are no longer trading. Web site still up but will not take online orders. Telephone number has been taken over by a new company who trade in aviation materials but only supply in large quantities.

Stuart

[bennie1]

Do you want
2.037" x 0.879" x 18g streamline

If so I may have some