PBL throwing the belt

[rd]

Situation:

PBL throwing the ball lift belt. About a month ago, the belt jumped off the pulley and rode on the side without falling off. I put it back on and a few days later it jumped the pulley to the other side but stayed on. I tightened the belt to 4" and it stayed on until this past Tuesday when it jumped off completely and (luckily) only slightly zapped a league bowlers ball. Not wanting to chance it anymore, I pulled that lift and put in another on Wednesday, no problems since.

The pulleys looked good, were centered on their shafts and didnt wobble. The lift was centered in the machine (I spent a lot of time on this). The lift belt itself (Vantage) seemed to be a perfect match to the pulleys on the lift. The height was adjusted so I could just see daylight between the ball and belt, same as the other conversions. The lift had ample shock travel left when the ball made it to the top.

What am I missing here?

[Ed Mc]

Re: PBL throwing the belt

Had to replace lift rails once because one was bent more than the other. Caused the ball to ride to one side. Never seen it again!!!

[Lampie]

Re: PBL throwing the belt

If the bushings or shafts on the lower and upper link assembly's are worn, the ball lift can be in center at rest position but will travel left or right in the up position.
These are neglected parts by a lot of mechanics...

[James Bandy]

Re: PBL throwing the belt

In the past AMF manufactured (due to error) pulleys with a wider groove. They had to have a belt made to fit these pulleys. I have seen mismatches and wrong belts.

Of course over time then there is wear that will also do this. Worn pulley groove that widens over time. It does not need to be noticable and belts will come off.

And as mentioned in the above post by out fellow BT Members, the bushings, housings and related components cannot be worn and loose. The lift must be centered and the lift tracks straight. If the belt moves to the side of the ball as it goes up the track it will eventually come off.

[JimDorsin]

Re: PBL throwing the belt

How does your top pulley look?? If it is slightly cocked to 1 side, you may have a bent/sloppy support rail. You can loosten the 2 5/6 18 bolts, straighten the pulley, and tighten them back down (very tightly) and it (should) remain straight.

Make sure your adjusters are set so that the belt runs flat all the way up the lift.

Worn belts can jump off. So can mismatched belts/grooves. If you have a large pulley groove and a small belt, you can have this problem. Both belts are still available as far as I know. (2 seperate part # in the book....lol)

lets us know what you find out.

Paul

[toon30s]

Re: PBL throwing the belt

Is the top yoke twisting some as the ball comes up? That would also throw a belt.

[LaRue]

Re: PBL throwing the belt

Also check the adjustment shafts on the link assemblys. If the pbl is not level that will also make a belt ride off. Alot of machines are not mounted at the same height and the adjusment shafts are there to compensate the difference. The adjustment shafts have to be pointed the same direction, if they are opposite the pbl will twist causing more problems.

[maister]

Re: PBL throwing the belt

Is the ball pushing the belt off from one side only.This will tell you that the ball coming from the opposite side is entering the door and pushing the belt away, not travelling up the centre and when it reaches the top it gives a final whip and pushes the belt off.A stretched belt does this or a pbl having excessive movement when ball enters.I would watch the belt and if it wobbles or vibrates when running without a ball , i think you may find it has stretched and 4" is still not tight enough.
Also if you can squeeze the belt in with your hands this is another clue.you don't want a belt when it is between the rails and half way up pushing the belt against the pbl. The cut in the pulley for the belt may be wrong, but if it is not deep enough, you would see this ,as the belt would not bottom in the groove.
good lick.
maister

[hatchie1]

Re: PBL throwing the belt

i had the same problem last week. about 3 time a day the belt would jump off the pbl. i stripped it out and and checked itbut couldn't find any problems, everything was fine on the pbl. i decided to put the spare in and as was installing it i found that the lift rails were loose where they join the down sweep. i sorted that and it's been fine since........

[rd]

Re: PBL throwing the belt

Thanks for the tips so far, keep them coming. I will check the lift rails tomorrow and things on the lift when time permits.

As these are conversions and not factory lifts some of your ideas have me wondering how good a job someone did when they built these. I think I remember something about the upper link but Ill check to make sure before I mention it.

The lift belt in question is only about 6 months old. The original was pretty worn so I grabbed that belt off a kicker lift and threw it on. It seemed to be a perfect match to the pulleys but I cant tell for sure. Before I started converting to PBLs I never knew there were more than one style of pulley or belt (WHY AMF WHY??).

Like mentioned, the replacement lift went in Wed with no problems during the week and no phone call this weekend so thats a good sign.

Thanks and Ill update later

Randy

[Universal Revolutions]

Re: PBL throwing the belt

I recall a time tossing ball lift belts. Found out that the spring loaded top end of the ball lift was not retracting when the ball went up the rails due to dents in the area where that “U” shaped slide bracket mounts and slides, causing it to bind. I would suggest removing the top fork from tube and check all related parts for dents, dings, bent…. Freedom to movment.

Dents and dings on mating parts makes the machinist cringe.

[Brianlah]

Re: PBL throwing the belt

You"ll have the best luck with the narrow belt Im not sure of the exact part # but its the lift belt that begins with 090-etc...That belt works well with both style pulleys.It fits better.

[poplarpetey]

Re: PBL throwing the belt

The support brackets (upper and lower) are sometimes attached with rivets. When these rivets come loose, that will allow the lift to twist and pop the belt off. Replace loose rivets with 1/4-20 x 2 inch bolts with locknuts.

Pete

[toon30s]

Re: PBL throwing the belt

Could the extra holes in the main tube of the lift be off far enough that the lift is not going up and down squarely, maybe off to one side, kind of a twisting motion? My PBL lifts were conversions too and I found a couple of new lower mounts off so bad I could not have gotten the shafts in the mounts on the machine sideplates without a BIG sledgehammer!

[rd]

Re: PBL throwing the belt

Originally posted by toon30s:
Could the extra holes in the main tube of the lift be off far enough that the lift is not going up and down squarely, maybe off to one side, kind of a twisting motion? My PBL lifts were conversions too and I found a couple of new lower mounts off so bad I could not have gotten the shafts in the mounts on the machine sideplates without a BIG sledgehammer!

<font size="2" face="Verdana, Helvetica, sans-serif">Yes Tony, this is what I remember about the upper link. Its bolt holes were drilled off center and its twisted to one side. I easily adjusted it out with the adjuster so I didnt give it much of a thought. Would this cause the lift to start out centered and track to the side as it raised up? Seems like it wouldnt be too big of a deal since a PBL lift only has a little upwards travel compared to a kicker lift.

Through Monday, no problems with the new lift. Its not even centered perfect yet either.