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  #1  
Old 06-10-2020, 04:27 PM
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Plummit Plummit is offline
 
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Default Metallurgist?

I need to replace this sheave that lifts my hangar door via a hydraulic ram. There are 4 cables that go around the sheave, and the door is a one-piece, metal frame with corrugated steel (read heavy). I can use 6061T6 for the replacement. Opinions on the strength of that alloy? The sheave is 4" diameter with a 1" steel pin and bronze bushings. The broken pin seized in the bushings and was spinning until it (probably after a few years) wore down to ¼" diameter then failed.

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Last edited by Plummit : 06-10-2020 at 04:32 PM.
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  #2  
Old 06-10-2020, 04:57 PM
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I'd make it out of steel. Lathe turn 8620 and heat treat for abrasion resistance.
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  #3  
Old 06-10-2020, 06:37 PM
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Quote:
Originally Posted by rocketbob View Post
I'd make it out of steel. Lathe turn 8620 and heat treat for abrasion resistance.
The Aluminum has lasted pretty well as these hangars were built around 1985.
I'm pretty sure that my replacement will be "lifetime".

-Marc
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  #4  
Old 06-10-2020, 08:34 PM
Taltruda Taltruda is offline
 
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I think he means to replace the pin out of steel. .why don't you just replace the worn out shaft and bearings? What's wrong with reusing the pulley?
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  #5  
Old 06-10-2020, 11:39 PM
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Originally Posted by Taltruda View Post
I think he means to replace the pin out of steel. .why don't you just replace the worn out shaft and bearings? What's wrong with reusing the pulley?
The sheave (pulley) is worn pretty deep. i replaced the pin with a hitch pin I cut to size. There are no bearings, just bronze bushings. It would probably last several more years but I have the opportunity to have a new one turned for the cost of material, so I'm going to renew it now.

-Marc
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  #6  
Old 06-11-2020, 12:17 AM
scsmith scsmith is offline
 
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I think 6061-T6 will work fine for the sheave. The key to longevity here is the bushings and the pin. You may be able to buy a nice piece of high-strength shafting material from McMaster-Carr and then carefully ream the pressed-in bushings to be a close running fit.
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  #7  
Old 06-11-2020, 01:51 AM
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How do you keep it lubricated?
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  #8  
Old 06-11-2020, 10:00 AM
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Quote:
Originally Posted by emsvitil View Post
How do you keep it lubricated?
Ha! I happen to have one of the manuals from the original Port-a-Port installation. It says to lube it every 6 months with WD-40! Before I had the manual I had decided to lube everything with LPS2 on an annual basis.

It's a pain to open up the sheet metal covers on the hydraulic unit to lube everything every 6 months, and I'm 100% sure that the majority of the hangars NEVER get lubed until something fails.

These hangars were built by Port-a-Port and they all have a single, overhead door, not unlike the old overhead garage doors homes had last century. I've had some people tell me that they can't be Port-a-Port because they only made the 3-piece doors we are more familiar with. Well these even have the Port-a-Port logo on the buildings.

They were built in a row, with a shared wall between them, separated by a single corrugated sheet metal "skin". Except that the operating section has a double wall to house the hydraulics or chain drive (Some are crank-up with a heavy duty chain drive and counter-balance).

I'll get my sheave turned out of 6061T6 and see what happens. I expect it will be strong enough.

-Marc
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  #9  
Old 06-11-2020, 12:28 PM
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Quote:
Originally Posted by Plummit View Post
Ha! I happen to have one of the manuals from the original Port-a-Port installation. It says to lube it every 6 months with WD-40! Before I had the manual I had decided to lube everything with LPS2 on an annual basis.

It's a pain to open up the sheet metal covers on the hydraulic unit to lube everything every 6 months, and I'm 100% sure that the majority of the hangars NEVER get lubed until something fails.

These hangars were built by Port-a-Port and they all have a single, overhead door, not unlike the old overhead garage doors homes had last century. I've had some people tell me that they can't be Port-a-Port because they only made the 3-piece doors we are more familiar with. Well these even have the Port-a-Port logo on the buildings.

They were built in a row, with a shared wall between them, separated by a single corrugated sheet metal "skin". Except that the operating section has a double wall to house the hydraulics or chain drive (Some are crank-up with a heavy duty chain drive and counter-balance).

I'll get my sheave turned out of 6061T6 and see what happens. I expect it will be strong enough.

-Marc
I would drill and install a couple zerk fittings and use grease as the lubricant.
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  #10  
Old 06-11-2020, 02:55 PM
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GeoffP GeoffP is offline
 
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Quote:
Originally Posted by 9GT View Post
I would drill and install a couple zerk fittings and use grease as the lubricant.
Good idea - drill the grease gallery into the centre of the pulley, so the grease pushes outwards. This will keep the dirt etc out of the pin / bush.

This door must weigh about 3T, if it's got a 4-drop pulley, on hydraulics, with a 1" steel pin!
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