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aligning pulleys

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aligning pulleys

Post by callum12 on Sat Oct 19 2013, 21:49

hi all,
I have just got a belt for my lister d and union pillar drill. this is the first time that i have had anything to do with engines, pulleys and belts.i found that the pulley on my lister is slightly raised in the middle. as a result, the thin belt wants to make its way to the edge of the pulley. this is a problem as the drills pulley is only about 1.5inches wide and has no lip. so it slips off really easily. How do i stop this? the only thing that i can think of is to smooth out the ridge to the pulley is completely flat.
Also to add to this, is there an easier way to align two pulleys rather than eye balling it then testing it by turning the engine over then making adjustments? or is this the only way?
thanks,

callum:D 

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Re: aligning pulleys

Post by matt86 on Sat Oct 19 2013, 22:06

your pulley is crowned for flat belts help keep them on ...

but for a v belt does not work , run near to the flywheel face , and only way is do by eye and adjust from there .

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Re: aligning pulleys

Post by callum12 on Sun Oct 20 2013, 21:00

thanks matt,
i'll try spinning it over with the belt nearer the flywheel face.
if that doesn't work, what are my options, as i also have a lister domestic pump.
thanks again
callum

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Re: aligning pulleys

Post by matt86 on Sun Oct 20 2013, 21:03

callum12 wrote:thanks matt,
i'll try spinning it over with the belt nearer the flywheel face.
if that doesn't work, what are my options, as i also have a lister domestic pump.
thanks again
callum
you should get it right slip the belt on engine and then move pump and slip belt on that . Then look down from the pump to see if straight and tweek pump left or right at one end . Start engine up and then can tweek from there .

Make sure the belt does not have a kink in it either otherwise its 1 step forward and 2 back situation .

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Re: aligning pulleys

Post by Villiers on Sun Oct 20 2013, 22:12

If you have a "crowned" pulley on your D then you need to line up the drill pulley with the middle of the D pulley, the idea of the crown is to keep the belt in the middle of the pulley itself, that is why you only have 1 crowned pulley, if you drive a crowned pulley with a crowned pulley the belt will "Dance" from side to side as it tries to self centre.

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Re: aligning pulleys

Post by callum12 on Wed Oct 23 2013, 18:11

okay, thanks for that Very Happy.
the lister isn't running yet, but when it is i'll let you know how i'm getting on.

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Re: aligning pulleys

Post by Darryl Ovens on Mon Dec 09 2013, 22:35

Belt alignment is an interesting (and can be complicated), topic, fortunately you can normally keep it relatively simple.

Vee belt alignment can be surprisingly important on large highly loaded industrial machinery. But there you don't get an indication of alignment like you do with flat belts.  A long straight edge laid across the sides of the rims is one of the methods used in industy. (I've seem string lines used in place of the straight edge or at a pinch sighting across the sides of the pulleys.  There are also electronic laser based systems too).  The straight edge works well provided the pulleys are the same width, or allowance is made if they are not.

Flat belts
The straight edge can also be applied to "flat" pulleys in the same way, the aim is to get the centre of the crown and the centre of the other pulley lined up, again allowing for variation in the widths.
It can be amazing how well the crown "steers" the belt to the centre.  This occurs as the crowned part which is slightly larger in diameter pulls that side of the belt slightly faster than the rest, steering the belt up the slope of the crown to the centre.   Interestingly a flat belt will run central on a pulley much narrower than the belt for the same reason.  An example are the very large diameter pulleys on pumps that need to run very slowly.  There may be a 2" wide belt but the large pulley is perhaps only 3/4" wide.  This effect occurs very strongly, until the belt slips then it ceases to occur and the belt slides off the crown.  I have a geared pump which needs very little torque to drive it,  On one occasion the pump moved on the ground such that the belt was so slack that both of the straight bits of the belt between pulleys were hanging down and running along on the ground between the pulleys.  I decided to let it run like that to see how long it would "stay on".  After 3/4 hour I decided it was not going to come off and retensioned it.

Sometimes lips are put on flat pulleys to retain the belt when the belt is slack or slipping.  However these lips can be a liability, as occasionally the belt can climb up on the lip which makes it too tight and from which it can be very hard to remove.  If the belt has a jockey wheel to allow it to be used as a clutch,  this becomes a problem as the clutch cannot now be disengaged.  We used to have trouble with a (BMB) walk behind garden tractor doing this.  Very  dangerous it you were backing up to something solid !!

Another thing to watch with flat belts are wind gusts that can blow the belt sideways.  We have now had two occasions (that I'm aware of), where a gust has blown the belt sideways and it has jammed in the gap between the pulley and the flywheel, then the engine has "winched in" the belt, pulling the pump or what ever it was driving towards the engine.  This happens surprisingly fast and due to the energy in the engine flywheel the engine does not stall till after the two machines have smashed together.  If you are lucky the belt breaks!

My two bits worth   Wink 
Cheers
Darryl

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Re: aligning pulleys

Post by matt86 on Mon Dec 09 2013, 22:45

when using flat belts i ALLWAYS have 2 rope pins / steaks driven into the ground either side of the belt to stop acidents happening .

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Re: aligning pulleys

Post by StewartH on Tue Dec 10 2013, 10:03

Glad this topic came up and some very useful info given (and some nightmares....)

".....When designing belt drives it is normal to apply a service factor to the drive operating load to compensate for allow for different driver type, driven load types and operating periods.

Selecting service factors for drive systems is a very imprecise science and it is recommended that the engineer use the information provided by the drive system supplier for detailed design work. The table below is provided to indicate in general, the level of service factor to apply for drive systems based on some knowledge of the driver equipment, the driven equipment and the operating period.

Some judgment is required in applying service factors for it is clear that a well designed drive includes provisions i.e flywheels, slipping clutches, fluid couplings etc which will effectively isolate the loads providing relatively smooth drive conditions even with load which have high levels of shock loading....."

Some very useful service factors can be found here...showing a huge amount of driven equipment and the considerations for driving them off a flat belt..

http://www.roymech.co.uk/Useful_Tables/Drive/Service_Factors.html

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Re: aligning pulleys

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