Good.......A Hard One....... :≫)
Hey John: How are things in Australia....hoppin .... I Trust??
Quite a perplexing problem: Weird 101
1. Can you get a nice flat magnet......say 6"x6" square and tape a piece of white paper on it for me.
2. Stick it on the sideplate, at top of sideplate on feed end, take a pencil stroke check, the at centre of sideplate-a pencil stroke check and then the discharge end of the sideplate - a pencil check and then do the same on the other side in all 3 positions please.
3. Use a nice sharp pencil, and just a almost non existant touch to get a measurable stroke, SCAN IT, and send it to me via email to bael@golden.net . I will analyse it ........and comment.
I really want or have to see the pattern to comment properly.
4. 12mm stroke (.480") is typical....actually a tad small or undersize .....but, nominal 1/2" basically. Typical for a lot of horizontal screeners.
THE GOOFY PART is: the part about the stroke length actually decreasing to zip or zero stroke then increasing to full 12mm stroke. My experience and yours says..."Now that aint kosher"
The stroke angle (should stay a the timing angle.....gear engagement of 45 deg off hor or vertical) it should not vary. Maybe this is the TROUBLE SPOT? it should NOT MOVE ...how can that be? Are gears OEM made or did someone blow a bearing and smash it through MR GEARSET.......and someone rebuilt the gearset.....to save money but, not to proper spec?
Like.........you have a stroke of some length when gears are engaged but, not when you hit a worn tooth area.......??? Should be lots of noise........theoretically.
850 rpm.......SEEMS a tad fast.........but, stroke seems a tad small.......to speeding up screen helps to compensate.
ANY new heavy parts added to body.....perf plate or heavier body members if repaired or other additions?
These units come with nested coil springs......were the rubber mounts OEM....or aftermarket??? Durometer of the rubber could be a possible contributing factor.........
Scan me a stroke check...........and all may become clear as mud.
Let me know...........George Baker - Moderator ■
Re: Troublesome Vibrating Pattern
Thanks George - much appreciated.
I will make some stroke cards as you suggest (visually the stroke appears a good flat line), but in the meantime would just like to clarify an important point.
The twin eccentric shafts are not geared together. They are each driven independently through separate electric motor/vee belt drives. This appears to be the OEM design, and I figure that they should automatically self synchronize (?)
I too am starting to look suspiciously at the rubber support springs. Don't know the rubber duro, but they compress about 25mm or a little more under static screen load, which would seem to suggest they are OK.
27 degrees C and sunny down here ■
No Gears???
John: If not gear driven.......is the drive mounted thru the body or up above the deck?
HOW WIDE is this screener?
If not gear driven.........are the belts.........VBELT STYLE or COGGED gates style drive belts?
................
sometimes when we mount circle throw shaft drive assemblies above vs thru the screen body........you will get stroke pattern going towards D.E. at FEED END.......KINDA up and down at centre and heading back towards feed end at DISCHARGE END...but not typical pattern on horizontal stroke machines.
...............
What do the adder weights to change the length of stroke or subtract the length of stroke look like?
George ■
Re: Troublesome Vibrating Pattern
Dear Mr. Johm McKenzie,
Please tell us if you have ensured both the shaft are running in opposite direction.
This way the vertical component of the moment wil get cancelled out and you will get pure linear Motion.
If the shaft turn in the same direction the the vertical component of the moment imparted add up and increase the erratic vibration which is transmitted to the springs and a secondary harmonic is generated.
Lots of luck ■
Re: Troublesome Vibrating Pattern
Dear Mr Jacob,
Yes I am very sure that both shafts are running in opposite direction - but thank you for the contribution.
......
George,
Sorry for the delay in getting the vibration stroke cards to you. It has taken a little while before I could get back to site - but all done now so I will scan and e-mail them to you.
Some questions that you asked....
1) The drive shafts are above the deck
2) The screen is 8' wide x 16' long
3) The belts are Vbelt style (3V profile)
4) The weights are flat plates bolted, to a flat milled section on the centre journal of the shaft.
The screen is generally identical to the L-Class as shown on the tycan website www.wstyler.com
I spent some time staring at the sucker the other day, and came to the conclusion that the screen IS "hobby horsing" on the rubber springs - but only at one end at a time. As the surging transfers from one end to the other it is giving the illusion of the stroke angle changing.
All other cases of hobby horsing I have ever seen have been simultaneously on both front and rear springs, and can usually be fixed by a small change in speed (say 50 rpm). Altering the speed in this case however only changes the length of cycle (from front to rear springs) ■
Strange Stroke
Hey John: Thankyou for you reply and the practical observations from the field. Always the best info.
I just got back into town from CONN-AGG show in Las Vegas....huge equipment show for aggregate processing firms.
..............
Here is another little trick.......i had an inclined screener 8x20 3 dk that was shaking weird by stroke check. I found a weird pattern on the DISCHARGE END.. stroke check and examined this area hoping to find a broken spring or rubbing on structure or anything........and of course, i found ZIP ALL. They were actually breaking a coil spring in one corner regularly and wanted to know why. If it more normal to break springs one corner, then opposite then another corner, etc.
,,,,,,,,,,,,,,,,,,,,
Playing SHERLOCK HOLMES,,,,,,,I suggested to the customer that this plant by my memory was erected VERY FAST,,,,,,,to meet a tight ERECTION SCHEDULE. I suggested he do a new TRANSOM check......(plant was already up and running for 3 years) and found ONE CORNER beam to be low by 3/4" ---- WE relevelled that corner and problem went away.
George ■
Troublesome Vibrating Pattern
I have a new (second hand) Tyler Horizontal Screen 16’ x 8’ with twin shafts (each driven independently by via separate motors and v belts), and all mounted on solid rubber support springs.
The screen has a most troubling vibrating stroke, which goes through a continuous cycle of slowly decreasing to zero and then increasing to full stroke. During each of these cycles the stroke angle (nominally 45 degrees to horizontal) sweeps through a full 360 degrees so that for half the time material is being thrown back up the screen. This phenomenon remains the same whether the screen is loaded or unloaded.
I am familiar with screens “hobby horsing” or “surging” on support springs, and am confident that this is not what is occurring here:
So far I have taken the following actions to investigate:
1)The two drive motors originally were not electrically interlocked, but doing this has only resulted in increasing the frequency of each erratic cycle from approx 5 seconds to approx 1 or 2 seconds.
2)Checked that both motors are drawing equal power, and that both screen shafts are operating at the same speed.
3)Decreased and increased the speed from original 850 rpm with no noticeable effect.
4)Altered counterweights to increase and decrease the throw from original 12mm with no noticeable effect.
5)Taken accurate vibration measurements (by vibration meter) which shows a very even stroke from identical positions on each side of the screen (several positions), and also relatively even stroke from feed to discharge ends. There is virtually no transverse motion measured on the side plates or drive mounting plates. (From my experience any broken or loose components would be indicated by transverse vibration)
6)The support structure is new, appears very solid, and the screen is only about 1.5m above the floor. Vibration readings taken on the structure indicate negligible transmitted vibration trtough the structure.
I am fast running out of ideas and would greatly appreciate input from anyone who has experienced a similar problem, or has any suggestions as to where to from here. ■