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jwallis
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Joined: March 02, 2012
Posts: 594
Location: Chicago
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 Posted: Sat Mar 26, 2016 12:38 pm Post subject: Overtightened V-Belt leads to premature water pump failure...? |
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| kamzcab86 wrote: |
Water pump is relatively young, but perhaps it is faulty? Lots of stories about poor quality pumps out there. |
I was considering posting this the other day, but kamzcab86's note to me in an unrelated thread prompts me to do it now.
I had an old water pump fail on me in Seattle, replaced by a local shop. A couple days later, I cranked down on the v-belt as I'd seen others do and tightened the alternator screws. I wasn't sure if the deflection specs were supposed to be hot or cold, but whatever, I got it real tight.
< 1 year later I had to replace it. I thought what a piece of junk, then I realized I must be to blame. I put way too much stress on the bearings in that pump, and probably my alternator as well.
Point is, I'm not going to worry about deflection specs as much as whether or not it's turning the pump, flopping around, squealing... generally looks like it's doing it's job.
Just wanted to throw this out there for anyone else who thinks tighter == better.
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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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Merian
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Joined: January 04, 2014
Posts: 5212
Location: Orygun
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| Posted: Sat Mar 26, 2016 1:10 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| you can call it the golden mean, or the interior optimum |
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chase4food
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Joined: February 27, 2016
Posts: 636
Location: PNW im Amerika
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| Posted: Sat Mar 26, 2016 1:12 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| jwallis wrote: |
| kamzcab86 wrote: |
Water pump is relatively young, but perhaps it is faulty? Lots of stories about poor quality pumps out there. |
I was considering posting this the other day, but kamzcab86's note to me in an unrelated thread prompts me to do it now.
I had an old water pump fail on me in Seattle, replaced by a local shop. A couple days later, I cranked down on the v-belt as I'd seen others do and tightened the alternator screws. I wasn't sure if the deflection specs were supposed to be hot or cold, but whatever, I got it real tight.
< 1 year later I had to replace it. I thought what a piece of junk, then I realized I must be to blame. I put way too much stress on the bearings in that pump, and probably my alternator as well.
Point is, I'm not going to worry about deflection specs as much as whether or not it's turning the pump, flopping around, squealing... generally looks like it's doing it's job.
Just wanted to throw this out there for anyone else who thinks tighter == better. |
I seriously doubt you killed it. Not all rebuilt pumps are created equal. I suspect it is likely a crapy rebuilt. On the Vanagon I don't heel the deflection method of determining the right tightness. I go by my seat of the pant gut feeling knowing the frictional characteristic of the belt. I do it a bit by trial and error.
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MayorMcCheese
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Joined: October 07, 2009
Posts: 750
Location: Lancaster PA
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| Posted: Sat Mar 26, 2016 2:27 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| I believe tencent says to run it pretty loose. I run mine loose with no noticeable downside |
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jwallis
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Joined: March 02, 2012
Posts: 594
Location: Chicago
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| Posted: Sat Mar 26, 2016 2:53 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| MayorMcCheese wrote: |
| I believe tencent says to run it pretty loose. I run mine loose with no noticeable downside |
He certainly knows his stuff, and this has become my feeling as well.
It's very possible I didn't actually kill it, but looking back I was running it stupid tight. I don't know what brand the shop put in there. They were a vw shop, but I was not at all impressed with anything they did for me. Bill was several hundred dollars, which I that was ridiculous after doing the job myself a year later.
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newfisher
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Joined: January 05, 2012
Posts: 1764
Location: The wet spot--Oregon
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| Posted: Sat Mar 26, 2016 3:45 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| Overtightening most V belt style water pumps will cause pre mature damage. Very common problem with novice classic car garage builders. I run all of mine looser than the deflection specs and have never had a belt break or fly off. |
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Wildthings
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| Posted: Sat Mar 26, 2016 7:59 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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On a Vanagon you are usually going to eff the alternator mounting in short order if you run the belt too tight. Buy a quality belt that will not stretch much when put under load and then run it fairly loose.
If you run a cheap belt with a lot of stretch you can crank it down pretty tight and still get squealing when you first start the engine and the alternator has a goodly load on it recharging the battery. |
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OhChit
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Joined: January 29, 2004
Posts: 271
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| Posted: Sun Mar 27, 2016 4:04 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| Wildthings wrote: |
On a Vanagon you are usually going to eff the alternator mounting in short order if you run the belt too tight. Buy a quality belt that will not stretch much when put under load and then run it fairly loose.
If you run a cheap belt with a lot of stretch you can crank it down pretty tight and still get squealing when you first start the engine and the alternator has a goodly load on it recharging the battery. |
Wildtang
Any idea how much resistance or energy is required to turn a alternator?
I realize that alternators spin free during cranking until engine starts and alt energized just curious approximately how much load is on the alternator.
Especially considering those that may be charging dual batteries etc.. That puppy must really put a pull on the distance water pump pulley, thus belt slap.. ?
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Steve M.
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Location: Fort Lauderdale, Fl.
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| Posted: Sun Mar 27, 2016 5:18 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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What happens when you tighten a belt too tight is your pulling the shaft over to one side causing the bearing to wear more on that side as well as putting more wear on the shaft.
That said how long did you drive it that way? If you know the mileage on the pump then you have a good idea it's condition. If not, then everything is just a guess unless you remove the shaft to see if the bearing is oval instead of round.
Even with recommended tightness, rotating parts just wear out. |
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Viva.Sabata
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Joined: October 09, 2013
Posts: 172
Location: Alaska
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| Posted: Sun Mar 27, 2016 6:58 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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Back to OP q - while alternator and water pump shaft bearings are designed for radial loading, excessive load (belt too tight) will lead to premature failure. The practical advice of running "loose" is good, just to the point that your alternator doesn't cause the belt to squeal all the time, or just after starting.
The pedantic answer is to google "v belt tensioning", which will show that belt tensioning has engineering consideration. Since very few of us own a tensiometer (more tools than talent!) the practical advice is sound.
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sjbartnik
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Joined: September 01, 2011
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Location: Brooklyn
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| Posted: Sun Mar 27, 2016 7:32 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| OhChit wrote: |
Wildtang
Any idea how much resistance or energy is required to turn a alternator?
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It depends on the electrical load you're placing on the alternator. The more electrical demand, the harder it is to turn. There's no such thing as free energy so take your full electrical load in watts, convert that to horsepower, and add some for conversion losses (converting mechanical energy to electrical energy) and that's how much hp it takes to turn your alternator.
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outcaststudios
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Joined: February 09, 2015
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Location: Maine
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| Posted: Sun Mar 27, 2016 7:35 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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youre not wildthings.
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Wildthings
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Joined: March 13, 2005
Posts: 52314
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| Posted: Sun Mar 27, 2016 8:00 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| OhChit wrote: |
Wildtang
Any idea how much resistance or energy is required to turn a alternator? |
The maximum load for a 55 amp alternator would be
Max load = 55A x 14.5V x e
where e is the inefficiency coefficient which I will guess is about 130% or 1.3
Max load = 55A x 14.5V x 1.3
Max load = 1040 Watts or about 1.4 horsepower
There are power losses due to the v-belt drive and the cooling fan on the alternator as well that would need to be added in, maybe another 50% for a maximum total load to drive the alternator of 2.1 HP.
When I have driven vehicles with the alternator belt removed, I have always been amazed how noticeable the lack of the alternator power draw is. |
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outcaststudios
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Location: Maine
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| Posted: Sun Mar 27, 2016 8:19 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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wildthings- semi-unrelated question about general belt tension.
i have(had until it burned up) an electric 220v 3/4 hp motor turning(1725rpm) a 2inch pulley that in turn (two belts)turns a 30 inch pulley,that is attached to a 800 lb. container of fluid that needs to be constantly turned. it ran for a day and a half straight until it died. the belts were slightly warm from friction i assume ,or possibly from heat conducted through the pulley to the belts . either way it felt warm. when i installed the motor i dialed the tension all the way out on the bolts so there was little deflection. the next day i came back out and one of the two bolts that provides even tension adjustment had slipped. i re tightened it and the a few hours later i came back and it was dead. no continuity in the motor windings. nothing hung it up but it burned up from stress. do you think that a) the motor is underpowered? or the tension was too much ? (thank you for indulging this digression albeit somewhat related to the topic)
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'69 westy
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Wildthings
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Posts: 52314
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| Posted: Sun Mar 27, 2016 8:34 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| outcaststudios wrote: |
i have(had until it burned up) an electric 220v 3/4 hp motor turning(1725rpm) |
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bluebus86
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| Posted: Sun Mar 27, 2016 8:49 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| outcaststudios wrote: |
wildthings- semi-unrelated question about general belt tension.
i have(had until it burned up) an electric 220v 3/4 hp motor turning(1725rpm) a 2inch pulley that in turn (two belts)turns a 30 inch pulley,that is attached to a 800 lb. container of fluid that needs to be constantly turned. it ran for a day and a half straight until it died. the belts were slightly warm from friction i assume ,or possibly from heat conducted through the pulley to the belts . either way it felt warm. when i installed the motor i dialed the tension all the way out on the bolts so there was little deflection. the next day i came back out and one of the two bolts that provides even tension adjustment had slipped. i re tightened it and the a few hours later i came back and it was dead. no continuity in the motor windings. nothing hung it up but it burned up from stress. do you think that a) the motor is underpowered? or the tension was too much ? (thank you for indulging this digression albeit somewhat related to the topic) |
Id ask the staff staff metalurgist about that.
as the load on a motor goes up, so does the current draw. too much load means a really high current which will over heat the motor and lead to winding failure from heat. could be too tight a belt could do this as a high side load on the parts can cause more friction, even bearing failure, or maybe the motor is undersized for the job. you can test how much current is required to turn the motor, just measure the current draw while it is running (let it get fully warmed up first) with an amp clamp, measure the current. see if it exceeds the rated capacity of the motor or not. you may also check for temperature rise as an indicator.
you may also measure torque required to turn your device and calculate required power based on that.
many motor companies have data to help you select the correct motor.
if then belt had been loose enough to slip, the motor may have lived to see another day a slipping belt can be a good thing, it is like a fuse that can prevent motor damage. better to replace the belt than the motor. also consider a motor with thermal overload protection, that will save the motor from damage do to too high a load.
what brand and type motor was used? does it have thermal overload protection?
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outcaststudios
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| Posted: Sun Mar 27, 2016 9:01 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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see thats what happens when a metalurgist tries to become an engineer. you missed the part where i said that the 'motor is burned up'  . if i could test the load on the motor while its running then i d already have my answer. the motor is a baldor ( ive had really experiences with them running full time for years) TEFL,capacitor start etc.rated for wet locations and continuous duty. but you're right ,the belt being loose certainly would have allowed the motor to turn and cool itself properly and not burn out the winding. especially that the one tension screw was loose and the other remained tight also shifted the load to one side and im wondering if that increased the friction just enough to clear the 3/4 hp motors load rating. im probably just going to go with a 2 or even 3 hp motor and leave the belts tension loose enough to slip instead of burn out. i figured that that debate here upthread about too loose or too tight just needed another slightly related example thanks for the replies!
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'88Doka JX td
'69 westy
(rip)couple bugs
(rip)three type III"s
(rip) '81 vanagon
a bunch of french stuff,and 9 motorcycles.
https://www.thesamba.com/vw/classifieds/detail.php?id=2573791 |
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bluebus86
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| Posted: Sun Mar 27, 2016 9:46 am Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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| outcaststudios wrote: |
| see thats what happens when a metalurgist tries to become an engineer. you missed the part where i said that the 'motor is burned up' . if i could test the load on the motor while its running then i d already have my answer. the motor is a baldor ( ive had really experiences with them running full time for years) TEFL,capacitor start etc.rated for wet locations and continuous duty. but you're right ,the belt being loose certainly would have allowed the motor to turn and cool itself properly and not burn out the winding. especially that the one tension screw was loose and the other remained tight also shifted the load to one side and im wondering if that increased the friction just enough to clear the 3/4 hp motors load rating. im probably just going to go with a 2 or even 3 hp motor and leave the belts tension loose enough to slip instead of burn out. i figured that that debate here upthread about too loose or too tight just needed another slightly related example thanks for the replies! |
for the next motor get one with thermal protection, basically a bimetal strip that is heat sensitive. if motor gets too hot the bimetal strip will bend and that opens the contacts thusmshutting the motor off. it will then cool down and eventually restart.
adding a regular fuse wont be as much help, as the starting current of the motor can be very high, exceeding the current rating of the motor, however the starting current is only breifly applied, so things do not get ruined during that brief over current situation. use of a slow blow fuse will help. a slow blow fuse can withstand a brief over current as when the motor starts. however unlike the thermal protection system, it will not automatically reset once things cool down, you will need to replace the fuse.
Baldor company can be very helpful in motor selection, they have good data sheets and can give advice too you. let them know what you are trying to do, pulley ratios and torque, rpm etc...required (put your torque wrench on one of the pulleys and measure torque to turn your system) with that data the correct sized motor can be determined.
good luck.
ps what is the stuff you need to stir?
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914guy
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Location: Cincinnati, Ohio
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| Posted: Wed Sep 21, 2016 7:58 pm Post subject: Re: Overtightened V-Belt leads to premature water pump failure...? |
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I just finished installing a new water pump. To avoid belt squealing, I did two things. I cleaned the alternator pulley and the crank pulley. Since I had the water pump pulley out, I lightly sanded the surfaces that make contact with the belt. I put radial sanding marks on the pulley and cleaned it.
No belt squealing and lower belt tension then I had. |
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