Shear pin keeps shearing

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Gordon J

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Didi Mau
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I just replaced the motor on my maxwell 1200, 12v electric windlass. In one week I have shaeared the shear pin twice. The first time I was pulling the anchor and just as it cleared the bow roller the pin broke. Half a day later, because of bad access, I was able to replace the shear pin. The pin broke the second time while I was setting the anchor. As I have done on every boat I owned, I dropped the anchor and then backed down on it to make sure it was set. The anchor was set and I would forward to put on a snubber line. When I try to put slack in the chain, I found the shear pin again broken.

The shear pin goes through the motor shaft and aligns in a slotted shaft in the gear housing.

I had anchored with this windlass many times before the motor required replacement. For two years I never had a problem, and then now. The shear pin is a split, spring pin that is hollow and compresses as it is driven into the hole. I am thinking of replacing the spring pin with a solid pin.

Has anyone experienced similar issues?

I am in Marsh Harbour the Bahamas and getting parts here is difficult. I was able to find similar shear pins in an auto parts store, but it broke like the first on.

Other info: using 3/8ths bbb chain and 60 pound Manson Supreme anchor. I always drive up on the anchor, never pulling the boat with the windlass. Backing down on the anchor with my 50k pound boat obviously broke the pin. However, I have used this procedure for two years with this boat, and for more than 20 years with previous boats, to include charters, with no issue. And backing down a n the anchor does not explain the first breakage.

Anyone have sage advice?

Gordon
 
Gordon J said:
I just replaced the motor on my maxwell 1200, 12v electric windlass. In one week I have shaeared the shear pin twice. The first time I was pulling the anchor and just as it cleared the bow roller the pin broke. Half a day later, because of bad access, I was able to replace the shear pin. The pin broke the second time while I was setting the anchor. As I have done on every boat I owned, I dropped the anchor and then backed down on it to make sure it was set. The anchor was set and I would forward to put on a snubber line. When I try to put slack in the chain, I found the shear pin again broken.

The shear pin goes through the motor shaft and aligns in a slotted shaft in the gear housing.

I had anchored with this windlass many times before the motor required replacement. For two years I never had a problem, and then now. The shear pin is a split, spring pin that is hollow and compresses as it is driven into the hole. I am thinking of replacing the spring pin with a solid pin.

Has anyone experienced similar issues?

I am in Marsh Harbour the Bahamas and getting parts here is difficult. I was able to find similar shear pins in an auto parts store, but it broke like the first on.

Other info: using 3/8ths bbb chain and 60 pound Manson Supreme anchor. I always drive up on the anchor, never pulling the boat with the windlass. Backing down on the anchor with my 50k pound boat obviously broke the pin. However, I have used this procedure for two years with this boat, and for more than 20 years with previous boats, to include charters, with no issue. And backing down a n the anchor does not explain the first breakage.

Anyone have sage advice?

Gordon
Click to expand...

I think you might do better asking the windlass manufacturer directly.

The shear pin is designed to protect the windlass. A solid pin disables that protection and if there's a problem, something more expensive will break.

Also, the shear pin you find in an auto parts store may not be the same as the original. Replacing the pin with the manufacturer's part may solve your problem. Again, contact them.
 
A roll pin as they are called are generally not used as a shear pin as you have a clutch for the purpose of overload. My guess is you have something binding in your gearbox causing the roll pin to break. Try separating the motor and gearbox and no chain on sprocket and see if gearbox turns easily.
 
I should have said that I did contact the manufacturer. The US representative had no great ideas. He suggested that I look for binding in the gear housing. Because the anchor pays out so easily, he thought that was probably a low percentage issue. Also, I never had this problem with the old motor. I swapped the motor because it begin dragging. After removing and troubleshooting we learned that there was some internal shorts in the motor that were unrepairable here in the Bahamas.

I suspect that perhaps that Maxwell Might have received substandard pins. I wish I had saved the old motor and I could have remove that pin and re-used it.
 
If this began after replacement of the motor, then I would look there. Perhaps the fit of the motor is different such that when you bolt down the motor it is crushing or partly sheering the sheer pin? I would be looking for some sort of interference in the motor fit.

The only other explanation would be that there actually is an internal gear box issue that caused the old motor to just slowed down, where the new one is pushing past the resistance to the point of breaking the sheer pin. I'm not sure how to test for such binding other that rigging up some sort of hand crank in place of the motor, and cranking by hand.
 
Is it correct to assume you replaced the motor in kind with matching OEM?
 
What you describe does not sound like a shear pin but a spring or roll pin used to hold a gear in place on a shaft.
The designers would not have expected there to be enough load to shear the pin so you need to find the source of that load.
 
One standard rule of troubleshooting is that if something was working OK and then you worked on it and now there's a problem, the first place to look is at the work you did.

SO - If the windlass was working until the motor failed and never broke the pin but since you replaced the motor it's been shearing pins, I would be checking the installation of the new motor. Alignment, binding, etc.
 
I can’t see a roll pin as being substantial enough to pull a 60# anchor with unknown weight of chain, or to back down on to set anchor. Roll pins typically just hold gears or parts in place.
Maybe you could get a spec on the torque value that it should shear at?
I’d pull the whole thing apart , inspect, clean and grease, and then put it back together making sure everything meets specs (no parts worn out).
Maybe the new motor is stronger than the old one, I see that on some replacement starter motors.
 
All ok

aboatman said:
One standard rule of troubleshooting is that if something was working OK and then you worked on it and now there's a problem, the first place to look is at the work you did.

SO - If the windlass was working until the motor failed and never broke the pin but since you replaced the motor it's been shearing pins, I would be checking the installation of the new motor. Alignment, binding, etc.
Click to expand...

Motor alignment is impossible to screw up...literally. Two bolts hold it on. The shear pin on the shaft either,fits into the end of the worm drive shaft, or it doesn’t.

Hordon
 
I'm having a bit of a problem visualizing the connection between the motor shaft and the gear, but if its like I'm thinking, if the slot that the gear end gets worn, it can try and kick the pin out. Since that pin is inserted in the shaft, it can get in a bind. I have a smilar issue on a slide for a motorhome and once that connection starts getting worn, it can go through pins pretty quickly.

good luck

toni
 
Somehow, the motor is the greatest suspect. It worked before the new motor. I don't see how it could be anything else.

While there may be no obvious alignment, there could be enough play in the bolts to allow a bind on the motor or gear box if the bolts aren't taken up together.
 
"As I have done on every boat I owned, I dropped the anchor and then backed down on it to make sure it was set."

Almost every windlass mfg sez to never anchor the boat to the windlass , just use it to lift the gear , After it is broken out.

Perhaps a bit too much reverse to "set" the anchor ?
 
FF said:
Perhaps a bit too much reverse to "set" the anchor ?
Click to expand...

Or at least set the cog wheel lock AND the bridle before applying strain, whether backing down or allowing from Mother Nature.

But I'm ignorant on purpose and design for Maxwell's shear pin. Thanks for post Gordon, I didn't know one even existed. Does on deck anchor load shear it or something else? :confused:
 
FF said:
................ Almost every windlass mfg sez to never anchor the boat to the windlass , just use it to lift the gear , After it is broken out.
Click to expand...

Yea, I posted that in another thread and people gave me grief over it.

You're right though, the windlass is designed just to lower and raise the ground tackle, not for holding the boat or backing down.
 
Gordon,
Long shot: not all roll pins are created equal.
Most are single wall construction, but I have also spec'd 3-wall "coiled" pins that have a lot more shear strength than the single wall pins (back when I was a machine designer.)

Given where you are, I am wondering if you could DHL-in a bag of pins from McMasterCarr or some place like that.
https://www.mcmaster.com/#roll-pins/=1bnifcy
 
I'm with Gone Farrell on this one, maybe the pins you're using are too soft ..? Failing that, perhaps there is a wobble of sorts that eats into the pin ....... FB
 
Actually

aboatman said:
Yea, I posted that in another thread and people gave me grief over it.

You're right though, the windlass is designed just to lower and raise the ground tackle, not for holding the boat or backing down.
Click to expand...

I saw a YouTube video from the windlass manufacturer in which they also used the windlass when backing down. They only secured the windlass to a cleat after they knew the anchor was set.

I am in a marina in the Bahamas with about 50 other long-term trawler owners. I asked several of them how they set the anchor. They All back down on the anchor before attaching the bridal. Into years of owning this boat I never had an issue until I swapped the motor. It is the right motor. It is for sure installed correctly.
 
I’m now thinking you are right

GoneFarrell said:
Gordon,
Long shot: not all roll pins are created equal.
Most are single wall construction, but I have also spec'd 3-wall "coiled" pins that have a lot more shear strength than the single wall pins (back when I was a machine designer.)

Given where you are, I am wondering if you could DHL-in a bag of pins from McMasterCarr or some place like that.
https://www.mcmaster.com/#roll-pins/=1bnifcy
Click to expand...

Thanks for the link on the pins. I too wonder if those I bought here are too fragile.
 
Thanks but don’t forget

sunchaser said:
Or at least set the cog wheel lock AND the bridle before applying strain, whether backing down or allowing from Mother Nature.

But I'm ignorant on purpose and design for Maxwell's shear pin. Thanks for post Gordon, I didn't know one even existed. Does on deck anchor load shear it or something else? :confused:
Click to expand...

That the shear pin provided with the replacement motor broke the first time I attempted lifting the anchor. The pin sheared just as the anchor landed on the bow sprit.
 
If you know the diameter and length I will help make a recommendation. The Maxwell manual is no help! Can't tell what it is.
 
I think as long as you continue to conclude this is not related to the motor swap, you will not find the problem. But I want to emphasize "related", not necessarily the motor itself. You know two things here for sure. 1) you swapped the motor, 2) coincident with that you started breaking pins. Whatever the problem is, all probability says it was pushed over the edge by the motor swap. Maybe due to increased power? Maybe but you said it broke lowering the anchor? That's hardly abusive operation. Maybe there is wear elsewhere in the gear box, and the new motor is somehow causing it to bind up more than before. You did say the old motor was dragging? Maybe it was an early indication of the problem you are seeing now.
 
The correct size

GoneFarrell said:
If you know the diameter and length I will help make a recommendation. The Maxwell manual is no help! Can't tell what it is.
Click to expand...

For the roll pins is 5 mm by 26 mm
 
I have made no such conclusion

twistedtree said:
I think as long as you continue to conclude this is not related to the motor swap, you will not find the problem. But I want to emphasize "related", not necessarily the motor itself. You know two things here for sure. 1) you swapped the motor, 2) coincident with that you started breaking pins. Whatever the problem is, all probability says it was pushed over the edge by the motor swap. Maybe due to increased power? Maybe but you said it broke lowering the anchor? That's hardly abusive operation. Maybe there is wear elsewhere in the gear box, and the new motor is somehow causing it to bind up more than before. You did say the old motor was dragging? Maybe it was an early indication of the problem you are seeing now.
Click to expand...

The problem is clearly related to the motor swap. The previous motor failed because of an interior short. It was slow. The current motor is really fast. The first pin failed while raising the anchor. The pin failed as the anchor cleared the end of the bow roller.

The second pin failed when I set the anchor at slow speed, less than a knot. This is the same procedure used by all with whom I talked. NO one I know puts a bridle on before insuring the hook is set right. Clearly there are some here who do so.
 
Gordon J said:
NO one I know puts a bridle on before insuring the hook is set right. Clearly there are some here who do so.
Click to expand...

Humm, so I am an outlier? in your opening post you said backing down on the anchor "obviously" broke the pin.

So why then does the Maxwell book say to relieve the anchor strain before applying a load, or words to that effect. I always thought it was to protect the gears. Now another reason, to keep a shear pin intact maybe. I really don't know.
 
Are the diameter of the hole in the shaft and the gear the same? If the Pin isn’t a snug fit in each that could cause problems.
 
Is it a 12V or 24V windless?

Had the old motor slowly degraded in performance, or was it more sudden?

And is the new motor operating a lot faster than when the old motor was working correctly?
 
I use my chain stopper when deploying the anchor before backing down to set the anchor. Then let some more chain out and use the bridle. I don’t back down using the windlass to hold the chain. The chain stopper is designed for that.
 
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