aluminum anchor roller

[ebb]

That is the rollers and channel that receive the anchor when hauled in by the rode.


WHY ARE ANCHOR ROLLERS NOT MADE WITH ALUMINUM PLATE?



What am I missing?
Is it the bling of buffed stainless?
If the stainless roller is made with 1/8" 304
it is usual to double the thickness for aluminum to be of equal strength to stainless plate.

1/8" 304 = 5lbs - $40sqft.

1/4" 6061T6 = 3.5lbs -$30sqft. (source onlinemetals.com - which is usually expensive.)

[c_amos]

Seems like (just theory, but hey why not..)

The Aluminum would corrode on the bottom, the flat part of the 'U' that lays against the deck.

Thinking about the way those alloy cleat bases look sometimes when they come off of their bedding... I bet there might be a corrosion problem.... especially with constant contact with the anchor / chain / shackles.

That is a theory... just a theory. I do have some big ole aluminum backing plates (below decks) that look just fine... so there is that... :rolleyes:

[Bill]

Looking for something strong but lighter that SS? Why not titanium? Remember, "it only costs a nickle more to go first class!" :rolleyes:

[carl291]

Well ebb,
My guess would be with aluminum, you would fabricate the gizmo and then heat treat to T6 specs. Then anodize for corrosion protection, This would be mucho expensive! You could never build this out of T6 stock, it just won't bend without breaking. I have seen cast aluminum rollers though.
With stainless you just bend . What I find amusing is the big thick plate of aluminum or stainless the roller is generally mounted to or on and then bolted to a deck of 1/4" fiberglass and 3/8" balsa wood.:p Do you see a weak link here?

[ebb]

Carl,
I know!.... another thing thing that gets me is how OFTEN the roller/channel is cantilevered off the bow - which puts the thrubolts in tension, which is not very smart.*

As I understand it, anodizing is a chemical process of oxidizing. Times three, since it is thicker than what naturally occurs. Anodizing is what fabricators do to give their work a nice finished look. But aluminum does its own oxidizing. It's the black stuff that comes off on your hands whenever its handled, even if its not noticable.
Just pointing this out, not lecturing - whatdoayeknow.

But it is to say that it is an unnecessary step.
And like stainless, if the fitting is exposed to air, the protective coat is self-healing.


As I went a little deeper into this, I found out that commonly available 6061T6 sheet (1/4") is quite versatile and can be formed into the bell curves we see on most anchor rollers. If the T4 sheet is available more 'severe' curves can be made.

5052 is aircraft aluminum sheet. Even more corrosion resistant and strongest of all available 'non-heat-treatable grades.' At the moment it's cheaper than 6061 at onlinemetals,com - at $13.60 a square for 3/16"!!!!
2.6lbs.
I'd seriously consider using the thinner sheet with this grade. But I'd be happy to talk with an aluminum fabricator about it first!!!!!


*In setting up ANY cantilevered anchor roller, I'd certainly support the outer end with a strut to the bow. I know, more bucks and added weight.


Anchoring using the channel is probably not the smartest. A bridle off the bow chocks would have to be used in all occasions imco. But I'd feel that way about any roller.


This is speculation.
I think we might all be happier with a twenty five pound Supreme banging around in a "traditional" stainless roller. I'm going to have to custom fabricate a roller for the Manson because nothing in the market really matches the anchor. That's why I'm asking what we know about aluminum rollers. My aluminum roller would be welded, not formed or bent into the channel shape. That's a real consideration, trusting the weld!
It may be cost, but aluminum has come down in price. It may be that a working fixture in aluminum is hard to get the brain around. But, there's that 40 year old mast.....?.......RIGHT?

TITANIUM??? Hey... how 'bout carbon....?
There's always galvanized.

[carl291]

Yes anodizing could be optional, but for the visual effect I'm sure it would be done for uniformity.... and eye candy appeal :o
The aviation repair folks I know claim fabricated aluminum gizmos are made from very workable soft aluminum and then heat treated to the desired hardness.
I'm guessing here now, but this may be what you want if welding will be done on your roller. Also anodizing may be needed because of welding , or powder coating.
T6 1/4" being very workable, I guess that is very subjective, It isn't for me, I've ruined more power tools just trying to cut it. Generally I drill hundreds of small holes where I want a cut and then file down. I can't bend a 1/4" wide X 12" long piece by hand.
If weight is the main concern , why not keep a smaller emergency (picnic)anchor on the roller and the hurricane anchor below?
Ebb , I have been meaning to ask you, Have you ever put an Ohmn meter on the copper coated hull of your vessel to see if it would get a reading?

[ebb]

Carl,
Got some 6061T6 from onlinemetals and macmastercarr. One piece was a 6"D tube with a 5/16" wall.
But remember no real trouble scrolling out shapes from the tube with my old Hitachi and an appropriate Bosch blade. They make aluminum specific blades.

Grinding and sanding (smoothing) was more difficult but got it acceptable for professional welding and anodizing.


5052-H32 (common) is 'far stronger than the 1000 to 3000 alloys. Yet forms well with a reasonable inside bend radius. Good weldability and corrosion resistance. Clear anodizing may be yellowish.'

6061-T6 is 'heat treatable to improve strength and has silicon added to the magnesium recipe. Much larger inside radius but can be formed.
LOOSES STRENGTH WHEN WELDED. The 5000 series alloys replace it in dump body and some marine aps.'

The yield strength of 5052 is 28000#. Yield of 6061 is 40,000# Both numbers seem enormous but focus here is material for an anchor roller, so maybe the wide separation is important. Assume an anchor roller will at times be subjected to sudden and extraordinary loads.

BENDING ALUMINUM
Now I'm thinking that the channel of the roller could be professionally formed. The bends would be 90degrees and therefor easy to do, but still could be expensive. It certainly seems an anchor roller of aluminum could be fabricated without welding!

Minimum bending radius for 5052 1/4" sheet is 3/8".
Minimum bending radius for 6061 1/4" sheet is 1".
I think the 6061 90degree 1" radius for a channel is perfectly acceptable.
Most designs have the front flaring done outside of the channel body where the roller(s) are.
Flaring 1/4" AL sheet also has to be done by a shop. Have made such a model that uses a lower roller instead of a flare with possibly split pipe rounds welded on the the outermost edges for fair leads. Need a photo huh?
Also, thought it would be a nice touch, since the bower will be a Manson Supreme with its prominent pipe roll bar, to add the anchor roller's chain keeper in a loop of aluminum pipe!

"As a rule of thumb, plan on using an aluminum sheet 40% thicker than steel. Since aluminum weighs only 1/3 as much as steel, this means the equivalent aluminum sheet will weigh only half as much as the steel sheet it replaces." Talking about equivalent stiffness and deflection. Broadly, comparing 1/8" stainless (probably thinner gauge) to 1/4" 6061.
This implys imco that any fears I have of aluminum not being equal to a s.s. Windline anchor roller are not well founded. Could be missing something here.... abrasion resistance perhaps???

Recommed DSM Manufacturing Co. (not an online retail materials source)
http://www.precisionsheetmetal.com/home/materials.htm
for a helpful and friendly technical reference on steel vs aluminum.:)
Quotes above generate from their presentation.


Is it possible that aluminum seems less acceptable JUST BECAUSE Windline has not marketed anchor rollers in that material. Have to see it to accept it???

__________________________________________________ _______________________________________
Bill, 1/8" thick titanium sheet (from onlinemetals) weighs 3lbs per square and costs only $195.70. Sounds like a real deal!!!!!:eek:

[c_amos]

Is it possible that aluminum seems less acceptable JUST BECAUSE Windline has not marketed anchor rollers in that material. Have to see it to accept it???


Could well be Ebb,

I look forward to seeing what you come up with. I am sure it will be a work of art. :)

[carl291]

Ebb,
I think Aluminum is a fine material, but bending the channel of the roller would be a challenge. I assumed this would flat stock welded into a channel
I don't know this to be a fact but I would bet the stainless anchor roller is a stamped piece. I don't know what type of a brake could make those bends that close together,but then I'm a back yard fabricator.
Looking forward to seeing your design.

[ebb]

Carl, my assumption too. But I don't like the idea of an anchor holder loosing half its strength to welding. I have some mast stuff going to the fabricators. I can tell you I don't go THERE very often. I often assumed that something can't be done - only to have the guys say, No Problem, we can do That.

I believe the relatively short (18"?) 1/4" sheet would be angled in the fulcrum press. Whatever its name. The sheet is pressed into a groove in a very controlled fashion with a radius edged blade - instantly making in this case a right angle. My roller however was designed for welding. gotta go back to the ole drawing board.

Imagine the monster press that stamps out the Windline channels. Probably a single shot! There's NO WAY we backyarders could accomplish either method.


What you pay the fabricators for is for things like this:
Aluminum has a grain from when it began as an ingot and got rolled and stretched.
Not good to bend aluminum parallel with the grain because the stuff might crack , but on one metal forum a guy pointed out that orienting the blank to be bent at 45degrees to the grain you'd get a much stronger fixture with hopefully no cracking in the joint. I'm gonna ask my fabs if they heard of this!
However I take shaped and finished pieces to the shop for welding and bending, to cut costs as much as possible.

Another thing about aluminum is that it changes its temper as it ages, it gets harder and stiffer. So you want to specify NEW stock from the foundry for bending, even if it's T6. I have not seen an aging rate chart.


Thanks for the interest. Maybe I can figure out how to get a photo to the Forum here beginning with the original model - for critique.
__________________________________________________ _____________________________________
THIS IS A LATER ADD ON POST (11/7/09):
I went to the www.kingstonanchors.com site and discovered a much more versatile group of anchor rollers presented in a very informative way.
There are decent diagrams that give enough info about specific rollers - and I think they have one that will work with the 25# Supreme. It's their Delta-20 Anchor Roller. It's stainless sheet of course. It has its rollers in a lower position (below the tray) that might work for the radial curve of the Supreme's shank. It may allow housing the anchor to keep it from moving. May be able to drill for a clevis pin to capture the anchor shaft thru one of its shackle holes. Haven't tried the roller.
My aluminum model looks a lot like the D-20 but is not as deep in front as the Kingston. All the metal out front might be necessay to control all the metal coming aboard when hauling the Supreme in. We'll see.
I've had to make a new model.
But I have the ALUMINUM in the shop.

[carl291]

Yes Ebb, positively a press and not a brake for this job. Your local affords you a wonderful opportunity to locate a fab. shop who would want to take on this job.
On the windline probably two punches one to shear and one to shape, what sixty to eighty and hour?
Interesting point on the age of the metal, I hadn't considered this. Also interesting is the 45* angle of the grain to the bend, hadn't heard that before.... maybe it comes with the directions for the press:D
Keep us updated Please.