Air compressor belt alignment problem

[Akathorn]

I found a Campbell Hausfeld VT619500AJ on CRAIGSLIST $400 last week. So far everything seems to be functioning properly except for one nagging issue. The drive belt won't stay centered on the flywheel. When I first got it home the belt was shifted one rib to the pump side of the flywheel. It'd been going on for some time because the belt was stretched out on that side from riding up out of the groove.

I replaced the belt with a new NAPA 5320, same part number as the old belt, but that didn't fix the problem. I consulted the manual and suspected the motor might not be properly aligned to the pump flywheel. I removed the belt, loosened the motor mount bolts and very carefully insured that the motor pulley and flywheel were properly aligned with each other. I tightened everything up, put the belt back on and, at first it appeared the problem was fixed. That was, until the pressure built the pressure built to about 90 psi, then the belt did a couple quick jumps and shifted one rib to the pump side of the flywheel again. I tried moving the motor pulley out by very small increments but then the belt started skipping out of the groove to the other side of the flywheel. I spent about an hour trying to find the sweet spot for the motor pulley but the belt just won't stay centered on the flywheel.

About the only thing I can think to try next is to spend another $20 the official Campbell Hausfeld replacement belt. Has anyone else out there dealt with and solved this problem?

 

[Bogie1632]

Got a pic of the pulleys? Are they adjustable on the shafts? Sounds like one, or both, may have shifted. Usually just a small set screw on the pulley hub to loosen and slide the pulley into position. Uses a long straight edge to help with alignment and tighten back down. Also make sure there aren't any burs or dents on the pulleys sides or ribs. They can cause a belt to jump position.

V/R
Bogie

 

[The Cobbler]

take a straight edge along the compressor flywheel, and adjust the motor pulley so the belt is parallel to the straight edge. also be sure your motor is parallel to the pump
also try flipping the belt end for end. if it still pops off after this

 

[Akathorn]

Thanks for the replies. Yeah, already looked into all of that. Everything is nice and clean, carefully aligned using a straightedge and burr free.

Steve

 

[LS6 Tommy]

Poly rib belts can be really tough to align. Millrighting is almost a black art.

Tommy

 

[nadogail]

Keep trying, even a blind dog sometimes finds a bone.

 

[The Tool Tyrant]

Correctly aligning the sheaves and proper belt tensioning is paramount and takes time...don't rush it. Using the straight edge across the pump sheave to motor sheave, be sure you measure to the belt groove on both front AND rear NOT just to the sheave as the distance from the the edge of the sheave to the belt groove varies between sheaves.
Locate an owners manual and verify the correct belt tension, which I've found to usually be higher than I would have guessed. To save frustration, use some sort of sheave spreader between the sheaves to tension the belts. Due to the slop in the receiver platform motor mounting grooves, the natural tendency is that the motor wants to **** out of parallel, so check, double check and triple check before finalizing everything.

 

[Akathorn]

Thanks for the feedback. I was very careful to insure that the flywheel axis was parallel to the motor pulley axis. I think my problem is probably insufficient tension. I tightened it some from the original position but probably not enough. The manual just said to properly tension the belt but didn't give any specification. I searched the company website and found that the belt slack should be between 1/4" & 3/8". Mine is currently closer to 1/2". I'll take out some slack and give an update.

I kind of miss good ol' v-belts...

 

[sberry]

spreader. I have had a busted thread in a belt, run it right off.

 

[KenC]

Correctly aligning the sheaves and proper belt tensioning is paramount and takes time...don't rush it. Using the straight edge across the pump sheave to motor sheave, be sure you measure to the belt groove on both front AND rear NOT just to the sheave as the distance from the the edge of the sheave to the belt groove varies between sheaves.
Locate an owners manual and verify the correct belt tension, which I've found to usually be higher than I would have guessed. To save frustration, use some sort of sheave spreader between the sheaves to tension the belts. Due to the slop in the receiver platform motor mounting grooves, the natural tendency is that the motor wants to **** out of parallel, so check, double check and triple check before finalizing everything.

That red part is really important with those little polyvee belts and easy to miss. Pulleys can be perfectly aligned edge to edge and still not be aligned groove to groove.

 

[jubilee]

A string is the best straight edge IMO. In most cases string can be tied off on both ends and then the 4 contact areas aligned.

 

[The Tool Tyrant]

A string is the best straight edge IMO. In most cases string can be tied off on both ends and then the 4 contact areas aligned.

Very seldom is the distance between the edge of the sheave to the belt groove the same on both drive and driven sheaves in which case a string is of no use.
I always clamp my straight edge at 180° apart on the driven (pump) sheave to allow my hands to be free to measure.

 

[SGKent]

If you can take a photo of both pulleys in the same shot, from above a ways but about the center of the pulleys looking down, then open it on your computer. Use a straight edge, or if you have a a program that draws lines on a photo you can see if the pulleys are aligned.

The string trick works equally well with two people if they each site down the string while it hovers closely over the grooves. The straight edge works well too but that assumes that the flange is machined evenly on the outside. Sometimes the string is better because it can look at the grooves. Make sure the pulleys are on tight, and that there no bent shaft or pulley involved. Someone could have dumped it on its side causing one of the pulleys to wobble now.

 

[Dustball]

There's three types of misalignment to look at, not just the offset-

https://www.flowcontrolnetwork.com/...le/15555626/the-importance-of-shaft-alignment

 

[Akathorn]

Lots of great guidance since I started this thread. It's running fine and staying in line (nice little bit of alliteration) now. The original problem was a combination of alignment and insufficient tensioning. I first addressed the alignment and took out some of the slack but the belt was still jumping out of alignment.

Since I had already addressed the alignment, I clamped a straightedge against one side of the motor mount base, removed the belt, loosened the motor mount bolts and, using the straightedge to maintain alignment, moved the motor back slightly before re-tightening the bolts, replacing the belt and rechecking the tension. After about the third attempt I had the belt at 1/4 inch deflection, per the manufacturer's recommendation. As KenC mentioned earlier, that was way tighter than my first guess at proper tension but the belt is staying put now, so I'm a happy camper.

 

[rburke65]

These simple problems can be pretty frustrating.