Advice on fabricating spacer tube for windlass gearbox

[LifesBetterWhenYoureBeating]

Hi folks,


The spacer tube on my windlass' gearbox got badly corroded (probably because it was marinating in salt water and in contact with the bronze deck plate), so I'm on the market for a new one. The gearbox is only 3 years old, and Maxwell won't sell me just the spacer tube (only sold as part of the whole gearbox assembly), so I'm considering having one fabricated locally (Colombia). I know if I ask around there will be people willing to make one for me but I'm not sure how to ensure it's as strong as the original and last at least as long (provided I manage to keep salt water away from it), so I'm looking for advice. For instance, what type of aluminum should I use? How to treat it against corrosion (paint/anodised)? Is it OK to weld flanges onto a tube or does it need to be machined out of a solid piece of aluminum?


Any advice would be greatly appreciated

[barnakiel]

I would be tempted to guess it can be cut off (the rotten part) then an overlapping part could be fabricated and then the two parts joined with 3 fasteners (120 degrees each)


If I were lost in a jungle, I would also consider building my own resin/glass part along the same lines - cut off the bad part, build a 'sleeve over' cuff with a lip, then use 3 bolts to make the two parts one.


A laminated part will be as strong as alloy here. And will not corrode anymore. Mind the bolts would need to be sunk in lanocote / duralac / etc before joining. Lanocote better here.


barnakiel

[LifesBetterWhenYoureBeating]

That's a great idea! I just have a few questions below...

Originally Posted by barnakiel

I would be tempted to guess it can be cut off (the rotten part) then an overlapping part could be fabricated and then the two parts joined with 3 fasteners (120 degrees each)

If I understand correctly the fabricated part would go like a sleeve around the existing one (after removing the rotten part) and the 3 fasteners would go through the walls of both (with a nut in the inside of the tube)? The wall of the existing tube is around 5mm thick, though. Would 3 fasteners in such a thin wall be strong enough? Would more fasteners be any better?

A laminated part will be as strong as alloy here. And will not corrode anymore. Mind the bolts would need to be sunk in lanocote / duralac / etc before joining. Lanocote better here.
barnakiel

Forgive me for my ignorance but what is a laminated part exactly? The need for lanocote suggests to me a metal, but I'm not sure what

[LifesBetterWhenYoureBeating]

I guess first I need to find out what are the forces being applied to the spacer tube. Is it just the vertical force from the weight of the gearbox and motor, or is there a lateral (centrifugal?) force opposing that when the gears turn the shaft? Again, forgive me my ignorance, I'm no engineer

[Cheechako]

Originally Posted by LifesBetterWhenYoureBeating

Hi folks,


The spacer tube on my windlass' gearbox got badly corroded (probably because it was marinating in salt water and in contact with the bronze deck plate), so I'm on the market for a new one. The gearbox is only 3 years old, and Maxwell won't sell me just the spacer tube (only sold as part of the whole gearbox assembly), so I'm considering having one fabricated locally (Colombia). I know if I ask around there will be people willing to make one for me but I'm not sure how to ensure it's as strong as the original and last at least as long (provided I manage to keep salt water away from it), so I'm looking for advice. For instance, what type of aluminum should I use? How to treat it against corrosion (paint/anodised)? Is it OK to weld flanges onto a tube or does it need to be machined out of a solid piece of aluminum?


Any advice would be greatly appreciated

It appears to be cast aluminum. Not sure you can readily re-use any portion of that due to possible welding issues. You could cut the bad end off and try a welding scheme to see.
Just use common 6061-T6 or T4 which will weld readily. Any alloy like the 6061 series in a T4 or harder temper will likely be stronger than the original.

The idea of a sliding overlapping new end may work but may be more fabrication/machining, depending on tubing sizes available etc.

It's unclear to me how that all works, do you have an assembly picture of the windlass? Is the tube a stressed part or just a guide for chain?

[LifesBetterWhenYoureBeating]

Originally Posted by Cheechako

It appears to be cast aluminum. Not sure you can readily re-use any portion of that due to possible welding issues. You could cut the bad end off and try a welding scheme to see.
Just use common 6061-T6 or T4 which will weld readily. Any alloy like the 6061 series in a T4 or harder temper will likely be stronger than the original.

The idea of a sliding overlapping new end may work but may be more fabrication/machining, depending on tubing sizes available etc.

It's unclear to me how that all works, do you have an assembly picture of the windlass? Is the tube a stressed part or just a guide for chain?

The first photo shows the exact gearbox that I have, and the 2nd shows a similar windlass setup (with a slightly different gearbox). Basically, the tube is just a spacer to create enough clearance between the gearbox and the deck plate (to accommodate a thick backing plate, the thickness of the deck itself and any padding between the deck and the windlass' deck plate).


The gearbox shown in the 2nd photo actually has the spacer tube split in 2 parts, joined by a plastic threaded nut, but the two parts of the tube seem to have matching "teeth" that line up -- I suppose to address the centrifugal force I mentioned before? The 3rd photo shows the gearbox from the 2nd photo, but in more detail

[wrwakefield]

A new spacer/anti-torsion tube could be fabricated, or the current one fixed with a new flange welded on top [after a weld test with a small tab of intended material.]

Assuming it is cast aluminum, or more likely a cast aluminum-magnesium alloy, I would weld test it first. [e.g., attempt to weld, say, a 1/4” thick tab of aluminum bar near the top- where it would be cut off with the corroded portion, and then try to break the tab off…]

If the parent material holds the weld well enough a new flange could be fabricated, welded on, then machined. [Or a complete new unit made…] Either way, I recommend a slip fit of the flange(s) over the tube so it could be welded on both sides for strength. Then the new flange(s) would need to be machined to be parallel with each other. [A mill or lathe would do…]

I would use either 5000 or 6000 series aluminum [e.g., 5086 or 6061, etc.] Degree of temper won’t matter if the flanges are circumferentially welded because the heat from welding will remove the temper on such relatively small pieces… unless possibly the welding was done in small increments between long air cool down phases… [The flanges will temper to T-3-4 naturally over time… or you could send the part out for heat treatment to T-6…]

That is a little bit of fabrication, welding and machining. I don’t know what the rates would be in your location, but I would be inclined to compare that to what you could purchase- even if you only need the spacer tube for now… [getting a back-up gear box may not be such a bad thing…]

I found a similar Maxwell assembly on Defender for US$630… https://defender.com/en_us/maxwell-gear-box-p12427



It is up to you to assess the cost of fixing/replacing existing locally vs: cost of new [even though it includes components not needed at present…] For me, if I don’t save at least 50% by fabricating/repairing, I lean toward replacement parts from the manufacturer…

Either way, to help the new unit last longer, I would isolate the aluminum flanges from those stainless steel fasteners with Tef-Gel or the like.

In case any of this is useful.

I wish you success getting your windlass functioning again.

Cheers, Bill

PS: Another consideration is to assess your current gears for wear, etc. in case that helps with the decision to buy new or fabricate/repair.

[noelex 77]

The easiest and least expensive solution would be to find a six-series aluminium tube of the correct diameter (most will be 6061). Weld this to a five series (say 5083) plate to create the flange.

The original product looks like cast aluminium, but the above solution will be the cheapest and easiest as a one off solution. It will be superior to the original.

Both five and six-series aluminiums have good corrosion protection and are rated as marine products. Five-series aluminium has significantly better corrosion protection than the six series but the five series are not commonly extruded so this cannot be easily used for the tube.

[barnakiel]

Originally Posted by LifesBetterWhenYoureBeating

That's a great idea! I just have a few questions below...



If I understand correctly the fabricated part would go like a sleeve around the existing one (after removing the rotten part) and the 3 fasteners would go through the walls of both (with a nut in the inside of the tube)? The wall of the existing tube is around 5mm thick, though. Would 3 fasteners in such a thin wall be strong enough? Would more fasteners be any better?



Forgive me for my ignorance but what is a laminated part exactly? The need for lanocote suggests to me a metal, but I'm not sure what

1) yes, a sleeve fabricated in aluminum alloy (NOT steel) is one option, I would bet to shear 3 M8 fasteners would take quite some torque from that motor, still, if you use as many as there are holding the flange to the (deck?) (I can see 4) then you cannot go wrong. Same number same diameter and this sure will not be too few.


2) a laminated part is a made in resin and glass fiber, it is not very difficult to make any shape and design one likes,


3) Lanocote or Duralac between SS fasteners and aluminum alloy body - is a MUST - perhaps that was part of why the original part died as it did on you - the fasteners (in SS) MUST be insulated from the alloy body. Otherwise the alloy part will be eaten out - like an anode on a propeller shaft.


Maybe the engineer who mounted your winch did not know that small, but quite useful, piece of info ...


ps and sure welding as another has said said - but I know too little about welding to be of use for you, but sure fabricating the missing part and welding may / will be an option


barnakiel

[Bowdrie]

For those of us sitting here in the U.S. with metal suppliers and machine shops/TIG welders at our beck-and-call it's easy to come up with solutions that in the end will hardly be cheaper than just buying the part.
In some back-alley place one might need to think outside the box.
One "outside the box" scheme; (assuming you can get fiberglass cloth and epoxy).
Wind a length of squeegeed out cloth over a mandrel, now you've got a tube.
Take squares/circles of squeegeed out cloth with an approximate sized center hole already cut out, compress them between two flat waxed surfaces with C-clamps, build up as much thickness as you desire.
With both tube and end plates you don't have to do the full thickness all at once, work at your own pace, use rasp and file as needed.
Now you've got your own "G10" end caps to bond/glass to the tube.
With a little care you can make an incredibly strong part that will hold fasteners and not corrode.

[thinwater]

Originally Posted by Bowdrie

For those of us sitting here in the U.S. with metal suppliers and machine shops/TIG welders at our beck-and-call it's easy to come up with solutions that in the end will hardly be cheaper than just buying the part....

This. I've made parts like this, and by the time you machine the parts, weld them together, and then finish machine to get proper alignment, as a one-off, buying is going to be cheaper. I'm also guessing there is corrosion other places, including inside.

[Cheechako]

Originally Posted by thinwater

This. I've made parts like this, and by the time you machine the parts, weld them together, and then finish machine to get proper alignment, as a one-off, buying is going to be cheaper. I'm also guessing there is corrosion other places, including inside.

I'm leaning toward these opinions from thinwater and bowdrie. By the time you get it all figured out and fabricated, along with the risk that something isn't quite a good fit........ buy the part and move on! Spend your additional effort figuring out how to protect it from corrosion again!

I had a Sunbrella underdeck cover made for one windlass of that type to avoid it getting doused with seawater in the anchor locker. But I will say, the cover kept it moist all the time as it didn't dry out well! Still ... it may have helped.

[LifesBetterWhenYoureBeating]

I got quotes for options to reuse the good half of the tube as well as fabricating a complete one, and there's a very reputable shop here that will make me one for $200 in 6061 aluminum (machined out of a solid piece), so I'm very tempted to do that. The new gearbox would end up costing more than $700 by the time it arrived here

Thanks everyone for the suggestions and advice!

[thinwater]

Originally Posted by LifesBetterWhenYoureBeating

I got quotes for options to reuse the good half of the tube as well as fabricating a complete one, and there's a very reputable shop here that will make me one for $200 in 6061 aluminum (machined out of a solid piece), so I'm very tempted to do that. The new gearbox would end up costing more than $700 by the time it arrived here

Thanks everyone for the suggestions and advice!

That is a bargain. That said, you/I don't know the condition of the insides. But it is a bargain, so it depends on your risk tolerance. Many or most people would get a whole new windlass, but I'm not sayin' that's right or I would know how to fix things.

[LifesBetterWhenYoureBeating]

Originally Posted by thinwater

That is a bargain. That said, you/I don't know the condition of the insides. But it is a bargain, so it depends on your risk tolerance. Many or most people would get a whole new windlass, but I'm not sayin' that's right or I would know how to fix things.

You mean the insides of the gearbox? It's only 3 years old and both the gearbox body and gears look perfect to me.