Len Marsden's humpback

[Lampie]

[img]http://pic2.****************/VOL26/934456/1718790/28825379.jpg[/img]
[img]http://pic2.****************/VOL26/934456/1718790/28825375.jpg[/img]

Len: your comments about the why and how please!
Maybe you have a good thing here, but it's too late for me.....

Martin

[8270king]

Re: Len Marsden's humpback

[img]/content/btubb/images/%%GRAEMLIN_URL%%/confused.gif[/img]

[Kat]

Re: Len Marsden's humpback

[len marsden]

Re: Len Marsden's humpback

martin,
firstly thankyou for acting as an intermediary and posting my pics.
for those of us who have worked with the pbl system and the kicker system,we would all have to agree that pbl is just about perfect.unfortunately it is not perfect,probably 80%. the problem stems from when the engineers came up with a great system but had to fit it into an existing framework.this was i believe an upgrade for the 70's kicker exit, so to keep costs down and make it a quick changeover it had to use as much of the existing hardware and also align to the machine brackets. the result was ok except for the problem where the parallel vertical alignment between the belt and uprails could not be achieved. this has lead to our most common problem of balls yoyoing between the belt and rails.
attempts to overcome this have generally been in 2 areas. bring the rail/belt closer together by packing the top of the rails with washers,but all this did was make the rail angle steeper and harder for the ball to roll up and also moved the "thimbles" away from the belt at the base of the rails. the other way is to apply extreme amounts of tension to the pbl to try and keep it from lifting away from the ball as it rolled up.
i ahve tried both and while they would work on certain exits i could not just do the one right across the house.
having worked with kickers before i knew that the gap between the belt and rails was the critical difference. the kicker lift sits very close to the rails and is parallel all the way up where as the pbl gap actually increases towards the top thus reducing the tension on the ball.
as you can see by the photos i have bent the tube just above the top bracket which achieves the result of getting the belt parallel to the rails all the way up.it also reduces dramatically the gap between belt and rail so much so the elevator lifts up high like a kicker lift.
to achieve this bend i supported the lift - after removing the belt - on the bench with the top half of the lift hanging over the end of the bench. i placed a length of steel rod between the 2 pulleys sitting in the groove to gauge when to stop bending and hung weights off the top pulley yoke. i then heated the tube until the weights starting pull the tube down. i continued the bending until i got a gap of 3/4" between the rod and the top bracket(where the grub screw sits).
i can honestly say that since doing this mod i have not had 1 problem with yoyoing.and the only ball i have had trouble with was a very filthy "skull ball".
len.

[Tablejam]

Re: Len Marsden's humpback

if this works like you say, be sure to get a patent on it if you can.

[Tablejam]

Re: Len Marsden's humpback

the way you had explained this mod really seems to make sense. our house has kickers and pbls, i can totally relate to this

[felix]

Re: Len Marsden's humpback

Len; Intersting, but you already had thicker uprails,right? [img]/content/btubb/images/%%GRAEMLIN_URL%%/wink.gif[/img]

[len marsden]

Re: Len Marsden's humpback

hi felix,
yea i tried that too. i've worked with pbl's since '83 and have tried lots of ideas in that time.
regards,
len.

[len marsden]

Re: Len Marsden's humpback

tablejam,
you're in the perfect position to see the difference between the belt and rail gap. i had to go to one of my old centres and take measurements and check angles each time i wanted to check something.
regards,
len.