Help With Alternator Belt On Stage Car.

[TurboDiverArt]

Hi All,

I’ve been having a chronic problem with the stage car where the alternator belt keeps coming off. My setup runs a Gilmer belt directly off the crank to the alternator, a la Duttweiler. I use to suffer from the belts occasionally coming off. Now I can’t see to keep the belts tight (same lot of belts I’ve been using for years, all purchased at the same time). There is about an inch clearance between the top of the belt and the bottom of the electric water pump. When loose the belt will actually slap the bottom of the water pump motor, it gets that loose. Attached is a picture. I think if I could fabricate a belt tensioner I might be able to keep the belt tight and not force it to come off. Recently it has not been coming off but jumping teeth and actually stripping the cogs off the Gilmer. The Alternator must sit very low, actually below the valve cover base because of the headers I have.

3 options I’ve thought of.

First option. Switch to a different belt. That’s got a whole set if issues. I don’t have a lot of room to adjust the belt so it needs to be just right going on. Would require new pullies. I don’t think I would go with a V belt because I don’t have enough adjustment to get the belt on and then tighten it. Also thought about a serpentine type belt but I don’t think I could get it tight enough without a tensioner.

Second option. Bore the adjuster hole larger. I think I might be able to get a little more adjustment “up” to tighten the belt. The problem is that it’s somehow loosening up. I tightened it as tight as I could get it and it quickly loosens up once started. I’m going to try this anyway. Maybe have to devise a better support for the alternator.

Third option. Devise a belt tensioner. I was thinking that if I could find 1.25 – 1.5 inch wide rollers I could probably fabricate up a tensioner that would squeeze the belt together. I might be able to mount it to the water pump as this is right in line with the belt.

My problem is that Norwalk is only 3 days away and I just discovered this problem last night. I thought I had it licked in January but I guess not. Any help or suggestions, even if long term solutions would be appreciated.

Art.
Well, I would post a picture but I gue you can't? Email me if you want to see the picture of the setup.

 

[8scbuick]

Hello Art.
I run the same setup as you do.Make sure the brakets arn`t moving around when you rev the engine.
You can make some sort of a tensioner.I used a vw t-belt tensioner to take some slack away.
On my alt i have some oversized washers that keep the belt inline.The washers go inboard and outbourd of the pulley.

Tony

 

[TurboDiverArt]

Originally posted by 8scbuick
Hello Art.
I run the same setup as you do.Make sure the brakets arn`t moving around when you rev the engine.
You can make some sort of a tensioner.I used a vw t-belt tensioner to take some slack away.
On my alt i have some oversized washers that keep the belt inline.The washers go inboard and outbourd of the pulley.

Tony

Hey Tony,

Do you have any pictures?

I'll double-check the mounting bracket to ensure it's tight to the head. The belt walks back and forth a little, maybe 1/8 inch as the engine revs but not too much. I have scrapes on the topside of the belt and when revving you can see and hear it slap the bottom of the water pump. The belt definitely walks more when the belt is loose (Duh!).

Where did you mount your tensioner to? That's my biggest problem is where to mount the darn thing.

Also, I have a bracket welded to the upper most portion of the alternator. It's the bolt that does not go through the alternator but bolts to the back. I had to weld a tab to extend the bolt-mounting hole upwards. I don't think the mounting bracket is really big enough, as there is not enough room. I've broken off the mounting bracket once before. Re-welded it and now it's bent so I removed the bolt as it's about to come off again. I was thinking that I might be able to drill a mounting hole through the aluminum bracket and use the stock bolt hole. Now sure why Dutt didn't do this, must be a good reason.

I'd be very interesting in seeing a picture of your setup so I have an idea of something to model it after!

Art.

 

[ijames]

Art, I'd like to see a picture of the belt and your current tensioner and the back of the alternator. Where do you get belts now, and what's the number on yours? Do you stretch the belt over the pullies or loosen the tensioner and slip the belt on then tighten? The latter is the right way - you are never supposed to stretch a cog belt like that or you can break the internal belts. My email is carl.ijames@verizon.net Thanks.

 

[TurboDiverArt]

Originally posted by ijames
Art, I'd like to see a picture of the belt and your current tensioner and the back of the alternator. Where do you get belts now, and what's the number on yours? Do you stretch the belt over the pullies or loosen the tensioner and slip the belt on then tighten? The latter is the right way - you are never supposed to stretch a cog belt like that or you can break the internal belts. My email is carl.ijames@verizon.net Thanks.

Hey Carl,

I don't have a tensioner, that's the problem. I loosen the alternator, put the belt on and then rotate the alternator up which tightens the belt. No stretching the belt when putting on or sliding over the cog. I'll email you a pic.

Thanks,
Art.

 

[TurboDiverArt]

Originally posted by 8scbuick
Hello Art.
I run the same setup as you do.Make sure the brakets arn`t moving around when you rev the engine.
You can make some sort of a tensioner.I used a vw t-belt tensioner to take some slack away.
On my alt i have some oversized washers that keep the belt inline.The washers go inboard and outbourd of the pulley.

Tony

Hey Tony,

I tried to email you but I got a bounce. Can you shoot me an email at artpaltz@optonline.net so we can chat and I can sent you some pictures?

Art.

 

[ijames]

Got the pics, Art, and have some more questions. What is the part number of your belt? How many teeth are on the alternator pulley? From the pictures I'm guessing a 20 tooth pulley and either a 5 or 8 mm tooth pitch and 15-20 mm wide belt, and from the design tables in the Gates catalog you may be over the maximum speed rating. You definitely need a tensioner, though - it's almost impossible to use a toothed belt without one. The tensioner needs to be a "positive" one, too, not a spring loaded one like stock. Those just bounce too much and you can jump teeth and strip them.

I guess while I'm asking questions, how may teeth on the crank pulley, as well?

 

[TurboDiverArt]

Originally posted by ijames
Got the pics, Art, and have some more questions. What is the part number of your belt? How many teeth are on the alternator pulley? From the pictures I'm guessing a 20 tooth pulley and either a 5 or 8 mm tooth pitch and 15-20 mm wide belt, and from the design tables in the Gates catalog you may be over the maximum speed rating. You definitely need a tensioner, though - it's almost impossible to use a toothed belt without one. The tensioner needs to be a "positive" one, too, not a spring loaded one like stock. Those just bounce too much and you can jump teeth and strip them.

I guess while I'm asking questions, how may teeth on the crank pulley, as well?

Crank pulley is about 4 inches in diameter and has 28 teeth. The alt pulley is about 2 inches in diameter and has 18 teeth. The belt I use is 30 inches in diameter and 1 inch wide square tooth. I've had best results with the Goodyear 300L100 belt.

I have a 1 inch good year belt on the oil pump. I can't remember the belt number for the oil pump because I've never had any trouble. Going on 3 years for the same belt, stays nice and tight but it is under-driven so does not spin as fast as the crank belt. No tensioner on the oil pump belt.

Art.

 

[opeltwinturbo]

Art: I sent you some pics in an email.

John Schmidt

 

[EightSecV6]

A common mistake when using "cog type " belts is running them too tight, rule of thumb is grab the belt and twist it, you should be able to twist it 90 degrees. I dont know if that is your issue, but I would look at it.

 

[TurboDiverArt]

Originally posted by EightSecV6
A common mistake when using "cog type " belts is running them too tight, rule of thumb is grab the belt and twist it, you should be able to twist it 90 degrees. I dont know if that is your issue, but I would look at it.

Hey Billy,

That's how I like to run it. Right now the alternator is not holding tension for some reason. I can start out having it much tighter than I like, start the engine, rev it a few times and then it loosens up and is slapping the underside of the water pump motor. Right now after running I could probably twist it 180, no kidding!

Art.

 

[EightSecV6]

Originally posted by TurboDiverArt
Hey Billy,

That's how I like to run it. Right now the alternator is not holding tension for some reason. I can start out having it much tighter than I like, start the engine, rev it a few times and then it loosens up and is slapping the underside of the water pump motor. Right now after running I could probably twist it 180, no kidding!

Art.

The alternator must be moving, I wouldnt put a tensioner on it, maybe a better bracket. Figure out some way to add a rod with 2 hiem ends on it for adjustment.

 

[TurboDiverArt]

Originally posted by EightSecV6
The alternator must be moving, I wouldnt put a tensioner on it, maybe a better bracket. Figure out some way to add a rod with 2 hiem ends on it for adjustment.

Yeah I hear ya. Norwalk's 3 days away and the welder is down. Going to have to see what we can do with limited time and resources right now. I'm hoping it's something with the adjuster hole and that can easily be fixed. We'll see.

Art.

 

[ijames]

Originally posted by TurboDiverArt
Crank pulley is about 4 inches in diameter and has 28 teeth. The alt pulley is about 2 inches in diameter and has 18 teeth. The belt I use is 30 inches in diameter and 1 inch wide square tooth. I've had best results with the Goodyear 300L100 belt.

I have a 1 inch good year belt on the oil pump. I can't remember the belt number for the oil pump because I've never had any trouble. Going on 3 years for the same belt, stays nice and tight but it is under-driven so does not spin as fast as the crank belt. No tensioner on the oil pump belt.

Art.

You definitely need a way to move the alternator to set the tension, rather than counting on the pulley's being the correct distance apart to get the right tension. Short term coming up with an adjustable bracket is your best bet.

Long term, looking in the Gates catalog (not saying their belts are better than Goodyear, just that their catalog is a good reference book and available online along with a neat design program that I've used several times at work to design simple setups, www.gates.com ), you are really pushing the speed limits on your setup. 28/18 = 1.556 so if you spin the motor to 7,000 rpm you are spinning the alternator at 10,900 rpm - wow. At 7,000 rpm the surface speed of the belt on the large pulley is 6100 ft/min, and "standard" cast iron pulley's have a limit of 6500 ft/min or centrifugal force can cause the pulley to come apart. In the "hp rating" design table for a 1" wide L belt and 18 tooth smaller pulley, the table only goes up to 6000 rpm on the faster shaft (or 3,860 rpm at your crankshaft) and belt life is substantially reduced at speeds above this (progressively more so as you go faster). HP limit is about 4 hp depending on rpm. A 140 A alternator putting out 14 V is making 1960 watts and if the efficiency is 90% the mechanical input is 2178 W or 2.9 hp. Given the jerkiness of a V6, how fast electrical loads and thus alternator output can change, and the rapid rpm changes I'd use a service factor of 2 (or maybe more; that's off the cuff), so the belt and pulleys need to handle 5.8 hp. Your setup is definitely on the light side, which would explain some belt stretch after only a little high rpm work. A much better choice would be a metric 5M belt in 25 mm width. You can get many more teeth in a smaller diameter than you current pulleys so you can keep your speed ratio in an even smaller package for more clearance, a speed rating up to 12-14,000 rpm, and a hp rating between 10 and 15 hp depending on exact choice of pulleys. Just some thoughts for the future. If you want some specifics on pulley diameters and belt length I can run the numbers for you.

 

[EightSecV6]

Originally posted by ijames
You definitely need a way to move the alternator to set the tension, rather than counting on the pulley's being the correct distance apart to get the right tension. Short term coming up with an adjustable bracket is your best bet.

Long term, looking in the Gates catalog (not saying their belts are better than Goodyear, just that their catalog is a good reference book and available online along with a neat design program that I've used several times at work to design simple setups, www.gates.com ), you are really pushing the speed limits on your setup. 28/18 = 1.556 so if you spin the motor to 7,000 rpm you are spinning the alternator at 10,900 rpm - wow. At 7,000 rpm the surface speed of the belt on the large pulley is 6100 ft/min, and "standard" cast iron pulley's have a limit of 6500 ft/min or centrifugal force can cause the pulley to come apart. In the "hp rating" design table for a 1" wide L belt and 18 tooth smaller pulley, the table only goes up to 6000 rpm on the faster shaft (or 3,860 rpm at your crankshaft) and belt life is substantially reduced at speeds above this (progressively more so as you go faster). HP limit is about 4 hp depending on rpm. A 140 A alternator putting out 14 V is making 1960 watts and if the efficiency is 90% the mechanical input is 2178 W or 2.9 hp. Given the jerkiness of a V6, how fast electrical loads and thus alternator output can change, and the rapid rpm changes I'd use a service factor of 2 (or maybe more; that's off the cuff), so the belt and pulleys need to handle 5.8 hp. Your setup is definitely on the light side, which would explain some belt stretch after only a little high rpm work. A much better choice would be a metric 5M belt in 25 mm width. You can get many more teeth in a smaller diameter than you current pulleys so you can keep your speed ratio in an even smaller package for more clearance, a speed rating up to 12-14,000 rpm, and a hp rating between 10 and 15 hp depending on exact choice of pulleys. Just some thoughts for the future. If you want some specifics on pulley diameters and belt length I can run the numbers for you.

Good GOD Carl! I think I could whittle a cog belt out of an old tire with a hacksaw before I could figure all that out!
When I set mine up I used part numbers from the belts I took from a running Bush GN engine, made the brackets and bought new belts. I dont get to run my car much but I have not had any belt issues. The hard part is getting the correct length when you change widths.

 

[ijames]

Well, mumble, mumble, never mind then, mumble, mumble . I just had a couple of free minutes and a handy catalog and wanted to see how well designed it all was. By the way, if you tell me the pulley sizes and center-to-center spacing I can tell you the belt length you need, if you ever change brackets around again.

 

[TurboDiverArt]

Well, we're going to Norwalk. I figured out the problem. The alt ratio, belts, pulley's etc. were selected by Ken Dutt when he built the engine. The problem was the bracket. Looks like when Ken created the oblong adjuster holes be must have drilled 2 holes and then connected them to make an oval. The problem was the lower oval had a dimple in the middle. I was not able to pull up all the way. Once I had the alt and bracket off it became apparent. An hour of analysis and filing and it’s fixed. The belt is nice and tight now and not slapping the water pump or jumping around. I changed the belt anyway and put a new one on. The old one was showing signs of wear from being run while very loose.

I need to fabricate a new bracket because the bracket really isn't big enough, needs to be about 1/2" longer. I'm using 3 of the 4 alternator-to-bracket mountings because the 4th doesn’t line up and is not oval. The bracket is too small to make it an oval allowing adjustment. Too complicated to explain. Now the alt belt is tight, we're going racing and as long as the weather holds I'll see for sure if it's fixed.

Time to get a few minutes of sleep before setting out.

Art.

 

[QKRNYRS]

Art,

Did you buy this car a few years ago from a guy in New York named Carter? If so, I was the one that built that car. Just sounds like a problem that we had with our Duttweiler engine that he built with the belt drive.

Pat

 

[Scott231]

Well, Art did not throw any belts on Thursday or Friday at Norwalk...but on his last pass (against me) he ran a 9.685 and blew a head gasket. So you know what he and Rich are doing tomorrow.