Shear pin keeps shearing

[Gordon J]

Old versus new

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?

The old motor was significantly slower than the new, but it was only working at about 30 percent, I am thinking. The performance seemed to get worse over time. I think the old motor was on the way out when I bought, but, being new to the boat, didn’t appreciate how slow it was.

The new motor, a 12v, works significantly fast than old.

The roll pin fits snuggly, has to be tapped in with a hammer.

 

[Gordon J]

This from the Maxwell website

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.

Tips and Guidelines:

Before deciding where you want to anchor, slowly cruise around the anchoring site and check the boats already at anchor, to ensure you have enough room to swing
Allow adequate room around the spot where you wish to anchor. Remember that power vessels swing differently than yachts. Boats on rope rodes swing around more than those on chain
Slow down and keep the bow into the wind, or current, whichever is stronger and as the boat comes to a complete stop, start to lower the anchor
After lowering the anchor, either drift back or slowly reverse while paying out the anchor rode, in order to ensure the anchor is set (holding firm)
The amount of anchor rode you pay out should always be at least three times the depth of water in which you are anchoring
In case the engine fails to restart, do not switch off the engine until you are sure the anchor is set (holding firm). Use buoys as reference points if they are available or, if close to shore, use prominent landmarks to check you are holding your position
Once anchored, secure your anchor rode with the chain stopper or secure to a deck cleat or bollard with a hitch that is easy to cast off. Do not anchor off your winch
Have a small buoy handy, which you can tie to the end of your anchor rode in case you have to slip your anchor. You will then be able to recover your anchor & rode later
Always anchor your boat via the bow
Check your position frequently when at anchor to monitor drag

 

[GoneFarrell]

For the roll pins is 5 mm by 26 mm

From McMasterCarr, two part numbers to consider:

Metric steel spring pin, 5 x 26mm, 3,900 pounds in double-shear, 91611A312. This one is really strong.

Metric steel coiled spring pin, 5 x 30mm, 3,300 pounds in double-shear, 91612A736
"These pins (the coiled pins) are stronger than 18-8 stainless steel pins and just as strong as 420 stainless steel pins. They remain flexible after installation, so they absorb shock and vibration better than slotted spring pins. They also have higher dynamic load capacities and accommodate wider hole tolerances than slotted spring pins. The ends are beveled or rounded to aid insertion. They are commonly used for fastening, pivoting, and holding."

So, while the single wall shows higher shear strength than the coiled, the coiled can take more hits from the high torque of motor startup/heavy load to the gears.

Consider getting both, less than $20, and you get lots of pins. You'll probably spend more on shipping.

Other considerations: see if you can turn the worm gear driven by the motor with a flat blade screwdriver or something similar, to eliminate the gears and bearings as a problem. The gears should turn easily with no chain on the wheel. I suspect the gearbox is not the problem though, as you have not changed anything there.

For the spring pin above with 3900# double-shear capacity: that is almost one ton of force on each leg of the installed pin, or 67 ft-lbs of torque on a 10mm shaft.

Good luck with this!

 

[Benthic2]

replacing a shear pin with a stonger one will defeat the purpose of the shear pin. Its designed to be a weak link so you don't break something more expensive. If you get a stronger than spec shear pin, you may break something else and regret it.

 

[aboatman]

replacing a shear pin with a stonger one will defeat the purpose of the shear pin. Its designed to be a weak link so you don't break something more expensive. If you get a stronger than spec shear pin, you may break something else and regret it.

Exactly and I mentioned this in post #2. Apparently, that's not what the OP wanted to hear.

 

[cafesport]

When you say the pin fits snugly I guess you mean into the new motor’s shaft. How about the ends of the roll pin that fit into the jaws on the worm shaft. Got a pick of the broken pin. Where did the broken off pieces wind up.

 

[GoneFarrell]

I don't think this drive is designed to shear at the motor shaft, the motor should stall first. Or we'd be hearing about a lot of Maxwell 1200's that shear pins off. I think it is better called a drive pin that is loaded in shear to turn the worm gear. I suspect under-spec thin wall pin on the replacement motor.

It is about a 24:1 self-locking worm gear drive, it won't backdrive by design.

 

[Gordon J]

And I suspect you are right

I don't think this drive is designed to shear at the motor shaft, the motor should stall first. Or we'd be hearing about a lot of Maxwell 1200's that shear pins off. I think it is better called a drive pin that is loaded in shear to turn the worm gear. I suspect under-spec thin wall pin on the replacement motor.

It is about a 24:1 self-locking worm gear drive, it won't backdrive by design.

Thanks so much for the help. I am going to order the pins from McMaster. I should know how they work in about a month. And you are right. It is probably better called a drive pin.

Gordon

 

[Gordon J]

I can’t see

When you say the pin fits snugly I guess you mean into the new motor’s shaft. How about the ends of the roll pin that fit into the jaws on the worm shaft. Got a pick of the broken pin. Where did the broken off pieces wind up.

How well the pins fit in the end of the worm drive. I was left with three pieces- the piece still in the shaft and both ends that were sheared off about even with the shaft. The breaks are irregular. The broken off pieces were lying in the gear housing. I have not yet disassembled from second go round. I am waiting for the new pins to get here.

 

[GoneFarrell]

Thanks so much for the help. I am going to order the pins from McMaster. I should know how they work in about a month. And you are right. It is probably better called a drive pin.

Gordon

You are welcome! I'd be all over this up on your foredeck if I was closer. But as it is, I am suffering through cocktail hour(s) here at my winter place in baja, where life is really rough you know!

Thanks to the power of the internet, I can offer free advice to the Bahamas while draining a cold one on the upper deck of my place here in baja against the green green palms and the blue blue sky!

Really hope this works out, I have had winch hassles in the field too.

Saludos, GF in baja, hoy!

 

[Benthic2]

Take the power of the internet further.....video conference with him via Skype or Facetime!

 

[Steve]

You say you are shearing a rolled pin, have you checked with the manufacturer to see if the correct pin for that hole is a rolled or solid pin? It should make a difference.
Good luck

 

[Gordon J]

Steve, yes it is a rolled pin

You say you are shearing a rolled pin, have you checked with the manufacturer to see if the correct pin for that hole is a rolled or solid pin? It should make a difference.
Good luck

I have pins coming from the manufacturer, as well as from McMaster