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Our shop recently purchased a dynocom 15000fx, used but in excellent shape, and we have been having incredible problems getting it set up.
Currently the last problem we are attempting to trouble shoot is that the belt linking the primary and secondary rollers continues to walk off to the inside of the pulleys, no matter what way we set the tension/idler pulleys. It seems as if both of the toothed gears are angled in, causing the belt to walk. Setup was performed exactly to dynocom instructions, and it seemed to align pretty well.
Any suggestions on getting this belt to track straight so we can use our dyno?
Can you shim one of the pulley shafts to bring it into alignment?
Maybe. They are keyed onto the shafts, and as best I can tell use jam nuts of sort to hold them in place. I'd like to avoid making permanent mods to the dyno if possible. If I can figure it out I'll try to post pictures.
Large toothed gear is on the primary rollers, small toothed gear is at the secondary rollers. Both have a idler/tensioner in between the main pulleys mounted a few inches below and forward or backward of the main pulley. The belt has been walking off to the inside of the pulleys, towards the rollers.
Your first picture shows an adjuster. I've tried to annotate your picture to point out the adjuster that will help you align the shafts so the belt tracks correctly.
It is pretty normal for a synchronous belt to walk across the pulley and rub on the retaining flanges. As long as there is no evidence it is working hard against the flange enough to damage the belt. Or are you suggesting it is so bad that the belt tries to climb up the flanges?
Adam, the belt has pushed both of the flanges off of the toothed gears and has begun to eat itself on the hard edge of the pulley. At first it seemed to be ok, but as soon as I got a vehicle up to speed it walked very hard, very fast.
David, we have used that adjuster, and with that adjuster bottomed out the belt still walks. Do I maybe have it adjusted the wrong way?
99% of the time it is a mis-aligned pulley setup. The other 1% it's manufacturing problem with the belt or pulley.
You need to align ALL the pullies and idlers in two planes.
The first, horizontal, is checked by using a straight edge held against the sides of the pulleys and idler(s). This checks two things - that all the centre lines are aligned (the same distance from the straight edge), and that they are all square to the centre line of the belt.
The second check is in the vertical plane, and is checked with a level or plumb line - the pullies and idler(s) should be all level.
If any measurement is off, it will load the belt unevenly and it will 'walk' off as it is directed one way or the other.
Give it a moment's thought and you should get the idea.
With the tensioner, it should NOT be tight, but just take up most of the slack in the belt as the cogs provide the actual drive. That also allows for thermal expansion and contraction. Don't know which is the drive direction, but the tension adjustment should always be on the slack, or non-driven side of the belt.
Gord, part of my problem may be that some of the pulleys are actually moving on their shafts. Even if all the center lines are in line, eventually they will move out of line. On top of that, each pulley is a different size so aligning them with a straight edge would not achieve centerline alignment.
Time to take the pulley's and shafts to a machinist to have them repaired / rebuilt. Most likely they will replace the shafts, and perhaps sleeve the pulleys if new ones can't be sourced.
I think your impression the dyno was in excellent shape was not correct -- needs work since it has serious wear.
The larger diameter pulley and idler fixings should not move if correctly fitted, there is quite a range of adjustment for shaft diameter - they're easy to do, but you will probably find a guide on the inter-web. Can't make out the small diameter pulley/s mechanism, though I've used the first two on multiple applications without problems. That said, if they have been allowed to slip by the previous owner, a clean and visual check wouldn't be out of order, in case there is actually some significant wear, but the designs are able to account for quite a lot.
Give some thought to the actual alignment - you should see how to square and align the pulleys easily using basic tools - reference back to the frame if required, you can also reference the pulley centre lines to the frame as that won't depend on figuring out the offsets for the straight edge. When you've done it once, and understand what you're doing, the next time it'll take a few minutes and get easier and faster each time.
I can understand some confusion if you're unfamiliar with these things, but look on the bright side, you only have 3 items to correct. When you've got them sorted, I'd suggest marking the shaft on both sides of the pulley, and the tensioner shaft position, with a marker, or paint, of some sort - that way a quick visual check will show if there is any movement that needs to be taken care of.
Forgot, if a shaft is bent, that can also cause problems, but it tends to be self correcting.
Thanks for all the help guys! This is my first time setting up a dyno, much less working with a belt drive of this size. I'm sure I'll get it.
I just got off the phone with dynocom, and learned some helpful info. We only used shims under the mounting brackets of the dyno, I think there is some flex on the frame, causing the pulleys to slope in ever so slightly. I've got another set of shims coming for the frame of the dyno, hopefully that will help in pulley/roller alignment. I also found out that the pulleys are adjustable side to side, and I think the jam nuts had backed out allowing the locking collar on the small toothed gear to loosen and the pulley to move. I have disassembled that pulley/shaft, cleaned, and lockedtited everything to help prevent that from happening again. I aligned the small toothed gear with the rest of the pulleys and tightened the jam nuts to spec, locking the pulley in place.
I will let you know when the shims arrive if these adjustments have made a difference.