Birty Dastards Jeep Club

Tech Forum => Workshop => Topic started by: MK1 on August 06, 2006, 01:12:27 AM

Title: Metal Strength
Post by: MK1 on August 06, 2006, 01:12:27 AM
Big Daddy Offroad make a 1/4" 6061-T6 (?)  Aluminum rocker guard/slider. The obvious benefit of this being the shipping weight is only 30(ish) lbs, there steel ones are 90lbs!

They claim that this 1/4" 6061-T6 (?) Aluminum is 25% stronger than 3/16 steel. Is this possible because I would have thought it bollocks?
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Post by: Warthog on August 06, 2006, 08:03:45 AM
Strength
The short answer to your question is  :shock: that in terms of strength, presuming an alloy and a steel are of the same design and have been engineered correctly, they will have very nearly the same strength, with the balance tipped somewhat in favor of aluminum, both in terms of overall yield, and in terms of ultimate failure.

In terms of weight, the balance is tipped very significantly in favor of aluminum.

Of course, taking that one step further, if the aluminum is designed to have exactly the same weight of structure as any given mild steel one, the aluminum will have considerably greater strength than the steel.
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Post by: isle of man on August 06, 2006, 10:05:46 AM
Quote from: "xj.jeeper"
(http://http://i37.photobucket.com/albums/e94/merlin2708/smileys/pics1.gif)



.



link to big daddy website http://http://bigdaddyoffroad.biz/xcart/home.php
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Post by: Ric Jacques on August 06, 2006, 11:17:06 AM
6061-T6 refers to the heat treatment applied, this is where the strength comes from.
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Post by: greggmo on August 07, 2006, 12:21:50 AM
if the ally is extruded it is strong as fook. if they make a claim they have to meet it anyway or ya send it back. 8) just be careful cos alum causes steel to rot if they are in contact.
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Post by: Ric Jacques on August 07, 2006, 10:02:58 AM
Quote from: "greggmo"
just be careful cos alum causes steel to rot if they are in contact.


Absolutely - you'll need to fay seal it with a corrosion inhibitor.  RTV should do the job.
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Post by: greggmo on August 08, 2006, 12:43:46 AM
Quote from: "xj.jeeper"
Quote from: "greggmo"
just be careful cos alum causes steel to rot if they are in contact.

 8)
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Post by: Warthog on August 08, 2006, 06:45:45 AM
Quote from: "greggmo"
Quote from: "xj.jeeper"
Quote from: "greggmo"
just be careful cos alum causes steel to rot if they are in contact.

 8)


Electrolytic Corrosion (Electrolysis)

Happens when dissimiliar metals are in contact in the presence of an electrolyte, such as water (moisture) containing small amounts of acid.

We Land Rover owners know too well.....! :oops:
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Post by: greggmo on August 08, 2006, 06:02:18 PM
as long as both metals are well coated with paint or what ever thay will be fine. i would think an ali tank skid of any strength would be almost as heavy as a good steel one.
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Post by: Anonymous on August 08, 2006, 07:49:09 PM
As has already been said the T6 refers to the heat treated condition & in the case of T6 this means it has been age hardened.

In other words it should not be soft & therefore has added strength which should enable it to take knocks without deforming or bending. It does however mean that in certain applications it will snap if bent beyond a certain point but on a formed skid plate I would have thought it unlikely unless there are small sections or tabs .

HTH
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Post by: MK1 on August 08, 2006, 07:56:11 PM
Ponyracer seems to think it's a bit of a con. He says that the aluminum will gouge and tear, which is no good for a rocker guard.
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Post by: chrisjones on August 08, 2006, 08:46:00 PM
6061-T6 ally is pretty tough stuff, with a much higher strength to weight ratio than steel. It's not as 'hard' as steel though and will suffer from scrapes and gouging when used for skid plates.
that said, this is only going to be cosmetic unless you get a real deep cut in it.
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Post by: ponyracer1 on August 08, 2006, 08:47:54 PM
That is correct when talking about normal ally, BUT by looking at the pics on the link it looks as if they annealed (softened) flat sheet then pressed into shape then hardened it. I doubt they could press that shape into hardened ally without it cracking.

So for those rockers I'd say go for it if you have the coin, they look like a nice bit of kit!!
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Post by: Mort on August 08, 2006, 10:32:57 PM
I have a mountain bike with a T6 frame - bloody strong and light, but not sure about the scratch issue.

On boats you have a sacrificial anode, which is usually aluminum, to protect the steel rudder and bronze prop.  This is usually replaced every few years (although more often in salt water).  This raises a cople of q's:-

Can you get sacrificial anodes for cars?  If so, what are they made of?

Is it the steel that rots on cars, or is it the ali like on boats?   If it's steel, does anyone know why it's different on boats?  :-k
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Post by: Ric Jacques on August 08, 2006, 11:12:28 PM
Oh Yeah it's definately softened, probably to T Zero, formed into shape then heat treated to T6.

A little while ago I had to try and form some 0.063" 2024 T3 into a channel for a repair splice on a plane (frame cross support).  Now then T3 is not as hard as T6, but it couldn't be done without cracking it on the outer radius.  There aint no way you could form T6 like that!!!!!!  Ended up getting authority from the manufacturer in Brazil to use a flat piece of 0.080" T3 instead.

Yes it will gouge quite easily, but hey just don't paint it, then you can polish any gouges out with some wet n dry.  Or leave em.  Battle damage is kinda cool......... :wink:
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Post by: MK1 on August 08, 2006, 11:24:22 PM
I have to have some kind of guard/slider to cover up the damage from Kirton. Yes, I know the bollocks about horses and stable doors.

My choices seem to be Rocker Knockers, Warn with the (W)anker, A-Z or the steel or ally Big Daddy. None of them are cheap to ship because of the weight.

Any thoughts?
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Post by: Ric Jacques on August 08, 2006, 11:37:23 PM
Personally I'd go with the ally.  Don't paint it.  Ally looks good not painted anyways, just keep it smeared with some oil to stop it from forming an oxide film.  If it does form an oxide film it's no big deal that's just ally forming a protective barrier against the elements, it won't corrode  further like steel does.

PM me and I'll send you some of this to fay seal it to the tub;

http://http://www.bergdahl.com/baps870c.pdf
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Post by: MK1 on August 08, 2006, 11:47:24 PM
I'm trying not to go for any chrome or shiney stuff so it would be the black powder coat if any.

http://www.quadratec.com/products/12012_202_07.htm (http://www.quadratec.com/products/12012_202_07.htm)

Thanks for the offer of the sealant though.