Bouncing head on tracked stacker

[Paultaggs]

Hi all, new to the forum so hopefully I am in the correct place.

My question is as follows and I am so grateful for any advice:

I made drive and tail drums for a client for a large tracked stacker, with large overhang at the rear (tail) end.
The head was specified as requiring dynamic balancing, and the tail static balancing.
This was done, but there was still bouncing at the head.
I looked again at the report off the balancing machine and it said there was only single figure grams of imbalance on either plane, so that could rule out an issue with the head drum, and to (what I thought) further confirmed this, was when the rear overhang was propped with a wooden skid, the bouncing at the head stopped, thus bringing me to believe that perhaps the tail drum should also be dynamic balanced. this was done, again within grams, and sstill the head was bouncing when the drum was refit.

I'm pretty sure the drums are OK but the client is holding it over me that it is because of the drums, I know that is a natural inclination, but the reports are stating all is ok with drums.

Is there anything in the conveyor system that could be causing this that I can go back to him and suggest it's something he should look into?

many thanks in advance for any input guys.

Drum mass is 100kg
service RPM is 162 RPM

 

[DDoug]

How is the out of round ?
Balance and out of round are two separate things.

You can be in balance, but out of round.

 

[Paultaggs]

How is the out of round ?
Balance and out of round are two separate things.

You can be in balance, but out of round.

Thanks for the reply DDoug. No the drums are not out of round, the outer surfaces have been machined concentric ref. the shafts post welding, so not concerned there. Although I do understand the reason for your thinking here.

 

[funwithfuel]

Is it a folding conveyor or telescoping? Is the tail self-cleaning? What material is being carried? Is it dry powdery or thick and sticky? Do you have a belt wiper fitted and what about a back-scraper?how are your troughing rollers? Is there perhaps too much tension on the belt itself? Any possibility you can post a link to a video of the machine in operation? Particularly, how are they "propping " the tail with a pallet?

 

[Paultaggs]

Is it a folding conveyor or telescoping? Is the tail self-cleaning? What material is being carried? Is it dry powdery or thick and sticky? Do you have a belt wiper fitted and what about a back-scraper?how are your troughing rollers? Is there perhaps too much tension on the belt itself? Any possibility you can post a link to a video of the machine in operation? Particularly, how are they "propping " the tail with a pallet?

Thanks. It is a folding conveyor, no the tail is not self-cleaning but it's moot at this stage as the machine is brand new in a shed and hasn't been used yet, this bounce was detected during testing. They we just jamming a 4' skid vertically under one side of the rear of the conveyor to support some of the unsprung mass and the head drum stopped bouncing. I took a video but you cannot even see the bounce in the video, you need to see it in person by sighting the motor off something horizontal in the shed like the gantry crane. Thanks.

 

[funwithfuel]

Electric drive or hydraulic. What kind of coupler? Lovejoy, rag, tapered? What kind of output speed? Is the driven side supported solely by the motor or is there a pillow bearing and the motor is attached external? Is the drum itself oscillating or are you just seeing the motor? Trying to find the root cause from the opposite side of the world is a bit challenging.

Do you have adequate belt slack? Some guys have tendency to train the belt off the head pulley vs tweaking the return rollers. This usually results in excessive friction at head and tail bearings. The fact that propping a pallet beneath one side tells me it's either too tight or that the frame is possibly misaligned. Again, this is a word away and I have nothing to look at. Good luck

 

[Paultaggs]

Electric drive or hydraulic. What kind of coupler? Lovejoy, rag, tapered? What kind of output speed? Is the driven side supported solely by the motor or is there a pillow bearing and the motor is attached external? Is the drum itself oscillating or are you just seeing the motor? Trying to find the root cause from the opposite side of the world is a bit challenging.

Hi. It's hydraulic, double drive, pillow blocks and motors attached externally. The drum and motors are not oscillating, just a slight bounce like typical for static unbalance, but the drum is balanced statically to 12g, and at the same time 7g&5g unbalance one two planes, (this is actually in compliance with US Navy specifications, never mind ISO whatever number, G6.3). When I spin the drums on knife-edge rollers the drums roll like they aren't going to stop lol, even when they get slower when you would expect to see the gravity acting on them and slowing their momentum, they just keep rolling and come eventually to a very slow halt with no rollback. The shaft runout on both ends is 0.05mm.

 

[funwithfuel]

So, now I'm going in the weeds. How thick is the belt, I'm guessing minimum 12mm. What's your ambient temp up there? You might wanna let that system run 20 minutes or so to soften and loosen up that new stiff belt. Also, look at it from the side. Make sure the guys who threaded the belt put it on right. I've seen belts on inside-out before. Just my thoughts on places to look.

 

[Paultaggs]

Thanks for the questions. The belt is 15mm thick. Ambient temp this time of year is around 7°c. They were running the system for 3 hours as per their normal test process for tracking, testing Etc. The belt has a hot vulcanized joint. Thanks.

 

[funwithfuel]

And you've measured both sides center of head to center of tail, there is no deviation in length? What about the hinge? Is it a pin with circlips or a nut and bolt? Is the hole possibly drilled incorrectly?

 

[komatsukid]

A little late but the conveyor speed may be too fast causing it to jump.