TurboDiverArt
The Guru Thorn
- Joined
- Nov 8, 2002
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.
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.
), 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.
