Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-02-2011, 03:43 PM   #1
Per
Guru
 
Per's Avatar
 
Join Date: Jan 2011
Posts: 622
New Alternator installed - but how to do a good belt tension?

I installed a new high output (105 amp) HD alternator. The old unit was not putting out so i figured why not spend a little extra and get more amps (thanks FF)

The only real challenge was to transfer the pulley from the old unit, had it done at a shop in the marina.

Now I am wondering if the belt is too loose, seems to move a little up and down when running, any rule of thuimbs of how tight or loose belts should be?

And whats a good method to get a good and tight belt?
Per is offline   Reply With Quote
Old 08-02-2011, 06:44 PM   #2
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 5,037
New Alternator installed - but how to do a good belt tension?

I use a prybar, normally a large screwdriver for tension while I tighten the bolts.

I don't make it as tight as I can get it, rather just tight enough so that when you try to rotate the alternator with your hand (by grabbing the cooling fins) the pulley will not slip.

Yes there are tension tools, but I read about "my" method and it has worked for me for many years and I have never burned bearings from being too tight, and the belts don't slip or bounce.

*


-- Edited by jleonard on Tuesday 2nd of August 2011 07:44:33 PM
jleonard is online now   Reply With Quote
Old 08-02-2011, 10:40 PM   #3
Guru
 
Edelweiss's Avatar
 
City: PNW
Vessel Model: 1976 Californian Tricabin LRC
Join Date: May 2011
Posts: 1,860
RE: New Alternator installed - but how to do a good belt tension?

I have always done the same thing as jleonard does and normally works fine. *Just don't overdue it. *On the Perkins the same belt runs the water pump, to much tension will run the bearings out of it.

The old 60 amp Delco's had a automotive style bracket and there is a lot of flex in them, so a little movement isn't unusual. *Just start out with a new belt and check your pulleys for wear and proper belt depth. *Since you are going to a higher output alternator check it under heavy load for slippage. *Some higher output units may really need a dual pulley setup to keep the belt from slipping.

Larry B
Edelweiss is offline   Reply With Quote
Old 08-03-2011, 03:52 AM   #4
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 22,553
RE: New Alternator installed - but how to do a good belt tension?

All you need is enough tension to keep the belt from slipping.

THis will depend on the % of belt wrap, if its high (goes almost 1/2 war round the pully ) lowerr tendion is fine.


You are looking to keep slippage low as it causes heat in the pulley , which is passed to the font bearing .

With the batts low start the engine and after 5 or 10 min shoot the temp of the alt , and the pulley.

If the alt is hotter than the pulley , the tension is fine.
FF is offline   Reply With Quote
Old 08-03-2011, 04:03 AM   #5
Guru
 
Tom.B's Avatar
 
City: Cary, NC
Vessel Name: Skinny Dippin'
Vessel Model: Navigator 4200 Classic
Join Date: Jul 2009
Posts: 5,841
RE: New Alternator installed - but how to do a good belt tension?

This might not be the most scientific method of doing it (or even correct), but what I have always done is to find the longest span the belt makes and twist the belt with my fingers. It should start to get hard to turn at 90 degrees. It seems simplistic, but it has always seemed to work for me.
Tom.B is offline   Reply With Quote
Old 08-03-2011, 09:38 AM   #6
Per
Guru
 
Per's Avatar
 
Join Date: Jan 2011
Posts: 622
RE: New Alternator installed - but how to do a good belt tension?

Quote:
FF wrote:
All you need is enough tension to keep the belt from slipping.

THis will depend on the % of belt wrap, if its high (goes almost 1/2 war round the pully ) lowerr tendion is fine.


You are looking to keep slippage low as it causes heat in the pulley , which is passed to the font bearing .

With the batts low start the engine and after 5 or 10 min shoot the temp of the alt , and the pulley.

If the alt is hotter than the pulley , the tension is fine.
*yes, definitively need to be tested under load. if the batts are 100% charged the alternator is not under load and the belt is basically just going around..

its a dedicated alternator belt and covers a good part of the pulley, probably 1/2 way around.

thanks to everyone, i will try some of those methods.
Per is offline   Reply With Quote
Old 08-03-2011, 10:09 AM   #7
JD
Guru
 
JD's Avatar
 
City: New Bern NC
Vessel Name: Stella Di Mare
Vessel Model: Mainship 34t
Join Date: Apr 2010
Posts: 1,702
RE: New Alternator installed - but how to do a good belt tension?

Quote:
Per wrote:FF wrote:
All you need is enough tension to keep the belt from slipping.

THis will depend on the % of belt wrap, if its high (goes almost 1/2 war round the pully ) lowerr tendion is fine.


You are looking to keep slippage low as it causes heat in the pulley , which is passed to the font bearing .

With the batts low start the engine and after 5 or 10 min shoot the temp of the alt , and the pulley.

If the alt is hotter than the pulley , the tension is fine.
*yes, definitively need to be tested under load. if the batts are 100% charged the alternator is not under load and the belt is basically just going around..

its a dedicated alternator belt and covers a good part of the pulley, probably 1/2 way around.

thanks to everyone, i will try some of those methods.

*1/4" deflection down from a straight line*on the long*span*is what will work.* Plain and simple.* Don't forget to tighten after four or five hours of run time.
JD is offline   Reply With Quote
Old 08-03-2011, 11:58 AM   #8
TF Site Team
 
Larry M's Avatar
 
City: Jacksonville
Join Date: Nov 2008
Posts: 11,681
RE: New Alternator installed - but how to do a good belt tension?

We have 2 alternators that we tension using SS fork/fork turnbuckles.* They're*easy to adjust for the correct*tension.
Attached Thumbnails
picture 524copy.jpg   picture 522copy.jpg   picture 520copy.jpg  
Larry M is offline   Reply With Quote
Old 08-03-2011, 03:16 PM   #9
Guru
 
Codger2's Avatar
 
City: San Diego
Vessel Name: Circuit Breaker
Vessel Model: 2021..22' Duffy Cuddy cabin
Join Date: Oct 2007
Posts: 6,691
RE: New Alternator installed - but how to do a good belt tension?

Quote:
Larry M wrote:
We have 2 alternators that we tension using SS fork/fork turnbuckles.* They're*easy to adjust for the correct*tension.
*** Nice!
Codger2 is offline   Reply With Quote
Old 08-03-2011, 03:16 PM   #10
Guru
 
Shoalwaters's Avatar
 
City: Rodney Bay Lagoon
Vessel Name: "Dragon Lady"
Vessel Model: DeFever 41
Join Date: Feb 2008
Posts: 681
RE: New Alternator installed - but how to do a good belt tension?

Quote:
Larry M wrote:
We have 2 alternators that we tension using SS fork/fork turnbuckles.* They're*easy to adjust for the correct*tension.
Now that is an elegant solution Larry. It also avoids the horrible discovery that you have levered against a temperature or pressure sender that was hidden in the gap between alternator and engine block. Any Yanmar owners out there will likely know what I am refering to!
Shoalwaters is offline   Reply With Quote
Old 08-05-2011, 10:02 AM   #11
Per
Guru
 
Per's Avatar
 
Join Date: Jan 2011
Posts: 622
RE: New Alternator installed - but how to do a good belt tension?

i checked the tension again, and it seems to be good according to the above mentioned methods.
also is similar to the tension on the other engine.

however when i run the engine i get some squeaky squealing sounds, pronounced at lower rpm, this was also occurring prior the new alternator.
the other engine does not produce this sound.. any clues?
Per is offline   Reply With Quote
Old 08-05-2011, 10:52 AM   #12
Guru
 
Shoalwaters's Avatar
 
City: Rodney Bay Lagoon
Vessel Name: "Dragon Lady"
Vessel Model: DeFever 41
Join Date: Feb 2008
Posts: 681
RE: New Alternator installed - but how to do a good belt tension?

Per, It could be you need to change the belt. Old belts get a hard glaze on the contact surfaces which make them slip and squeal. I don't recommend belt lubricant - strictly a temporary remedy.
Shoalwaters is offline   Reply With Quote
Old 08-05-2011, 09:01 PM   #13
Guru
 
Edelweiss's Avatar
 
City: PNW
Vessel Model: 1976 Californian Tricabin LRC
Join Date: May 2011
Posts: 1,860
RE: New Alternator installed - but how to do a good belt tension?

Quote:
Per wrote:
i checked the tension again, and it seems to be good according to the above mentioned methods.
also is similar to the tension on the other engine.

however when i run the engine i get some squeaky squealing sounds, pronounced at lower rpm, this was also occurring prior the new alternator.
the other engine does not produce this sound.. any clues?

.

Yes and also check the belt depth, could be the belt is bottoming out in the pulley. Worn pulley are a concern too.
Edelweiss is offline   Reply With Quote
Old 08-14-2011, 09:34 AM   #14
Guru
 
C lectric's Avatar
 
City: Gibsons, B.C., Canada
Vessel Name: Island Pride
Vessel Model: Palmer 32'
Join Date: Oct 2007
Posts: 4,414
RE: New Alternator installed - but how to do a good belt tension?

Take a good look at the sheaves. If the bottom of the sheave v-groove or the bottom of the belt is shiny, the belt is not riding correctly. It should contact ONLY the sheave sides, not the bottom.

The sheave sides should be smooth and the tapered sides appear straight, no dips or worn grooves or steps. Anything like that reduces the contact patch, friction, and the belt may slip even if it is screaming tight [ not good].

The belt may be worn or the wrong size, cross section. I've had this happen and it took a couple replacements before I took a hard look at why and realized the cross section was wrong. I'd just replaced the slipping belt with the same type. When I got the correct belt there were no problems after.

The sheaves may be glazed. The glaze can be removed with some sandpaper or a small wire brush and solvent. A thorough wipe down afterwards with something like acetone to completely remove any trace of oily residue should help.
C lectric is online now   Reply With Quote
Old 08-14-2011, 05:16 PM   #15
Grand Vizier
 
Delfin's Avatar
 
Join Date: Jan 2010
Posts: 3,816
RE: New Alternator installed - but how to do a good belt tension?

Quote:
Larry M wrote:
We have 2 alternators that we tension using SS fork/fork turnbuckles.* They're*easy to adjust for the correct*tension.
That is so smart.* Very clever, Larry.* I am going to see if that will work for mine as well, and I don't see why not.
Delfin is offline   Reply With Quote
Old 08-18-2011, 12:53 PM   #16
Guru
 
Fotoman's Avatar
 
Join Date: Nov 2009
Posts: 649
RE: New Alternator installed - but how to do a good belt tension?

Quote:
Per wrote:
however when i run the engine i get some squeaky squealing sounds, pronounced at lower rpm, this was also occurring prior the new alternator.
the other engine does not produce this sound.. any clues?
My grandfather use to press a soap bar against a squealing alternator belt.*Works great. *
Fotoman is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Making Way With Mast installed phishown General Discussion 6 03-16-2011 04:15 PM
Boat Name installed blacksheep General Discussion 20 03-11-2011 09:00 AM
Serpentine belt and alternator rating r-rossow Electrical and Electronics & Navigation 2 11-09-2010 05:54 AM
Belt supplier and old numbers Tom.B Power Systems 15 07-28-2010 03:57 AM
Diver installed Zincs Forkliftt General Maintenance 9 02-07-2010 05:04 AM

» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 12:05 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012