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Quad Roller Skating Forum Discussions about quad roller skates and any other quad skating discussions that do not seem appropriate for one of our other forums.

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Old April 6th, 2017, 01:53 AM   #61
fierocious1
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So after doing a little math and some more pondering I determined it's a bad idea to rotate the truck from the original geometry (Remember I was trying to rotate it to get a steeper angle of rotation. But doing so puts the pivot pin perpendicular to the plate.).:

The problem involves energy transfer when landing a jump.
As long as the pivot pin is at an angle to the vertical, when a force is applied at the wheels, the truck will rotate about the pivot ball and compress the cushion. If I move the pivot pin to vertical; all the force is transferred into the rigid plate. The cushions will take none of the load. This sounds like a sure way to bend an axle.

I'm going to increase the rotation angle another way:
1. extend the pivot pin. Looks like I need to make the pivot pin .200" to .250" longer. So it's going to be a custom part. - There goes my low cost goal.
2. Add a washer(s) to shim between the truck and the bottom cushion.
Adding the shim between the truck and bottom cushion will not work, or gain you minimal changes(it would depend on exact nut position being repeated). The distance between the plate and truck would have to be altered to make a change in tune while leaving the pivot unchanged except for standard adjustment.
I bought some microstars many years ago and played a little with them when my wife needed to have them adjusted.. The wheels controlled the cushions on each side of the plate. Tighten the axle nuts and the cushions were compressed more. The wheels used spacers.
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Old April 7th, 2017, 04:38 AM   #62
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Adding the shim between the truck and bottom cushion will not work, or gain you minimal changes(it would depend on exact nut position being repeated). The distance between the plate and truck would have to be altered to make a change in tune while leaving the pivot unchanged except for standard adjustment.
I bought some microstars many years ago and played a little with them when my wife needed to have them adjusted.. The wheels controlled the cushions on each side of the plate. Tighten the axle nuts and the cushions were compressed more. The wheels used spacers.
It takes a lot of washers to make a difference. Theoretically you can add half the thickness of the washer to the truck pivot point.
I tested the concept tonight at Dairy Ashford. Used 4-5 washers on each truck. It defiantly created a different feel. But also created some other issues i did not expect. The truck did not rotate as expected. The pivot pin "wobbled" more in the cup. The setup exaggerated the fact that my trucks/plate do not match perfectly. The setup likes to be tighter than my normal setup - probably due to the pivot ball location issue. Also I'm still having an issue with crushing the blue cones. It was setting on the washer and not inside the truck cup. I really need to go with a harder & longer cushion on the bottom side.

So yeah, I'm not sure what I achieved. Can't really say I prefer either the old or the modified setup better. But at one point I did catch an edge I've never caught before. So I think I'm headed in the right direction.
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Old April 7th, 2017, 11:54 AM   #63
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It takes a lot of washers to make a difference. Theoretically you can add half the thickness of the washer to the truck pivot point.
I tested the concept tonight at Dairy Ashford. Used 4-5 washers on each truck. It defiantly created a different feel. But also created some other issues i did not expect. The truck did not rotate as expected. The pivot pin "wobbled" more in the cup. The setup exaggerated the fact that my trucks/plate do not match perfectly. The setup likes to be tighter than my normal setup - probably due to the pivot ball location issue. Also I'm still having an issue with crushing the blue cones. It was setting on the washer and not inside the truck cup. I really need to go with a harder & longer cushion on the bottom side.

So yeah, I'm not sure what I achieved. Can't really say I prefer either the old or the modified setup better. But at one point I did catch an edge I've never caught before. So I think I'm headed in the right direction.
If you are making the caster more vertical the skate will definitely want stiffer cushions. I can't use blue cones, too soft for me. Normally I use yellow cones on top and bottom of the truck. If needed I adjust the pivot but have only had to do it one time IIRC. The geometry of the trucks may be a bit different than the SG DA45s. Stay with it, your work will pay off.
Mine are done, The suspension is working great and I have no more changes to make to my skates other than cosmetic. Polishing may be in order but I can't tear them down long enough to do it with out a backup pair. I have spare frames but they aren't finished yet.
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Old April 7th, 2017, 12:32 PM   #64
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OK, I'll now admit adding washers above the bottom cushion is not a good way to adjust the roll angle (caster as you call it). It changes the geometry: how the cushions get compressed. Hence the cushions compress more for the same plate rotation. This would explain why I was not experiencing the movement behavior I was aiming for. It also explains why the truck wanted to shift instead of pivot. So in reality I need to hit the geometry correct on the first try since I won't be able to shim much.

That's the beautiful thing about playing with actual hardware: You see things you never expected.

Last edited by amohrfeld; April 7th, 2017 at 09:40 PM.
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Old April 7th, 2017, 07:45 PM   #65
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OK, I'll now admit adding washers above the bottom cushion is not a good way to adjust the roll angle (caster as you call it). It changes the geometry: how the cushions get compressed. Hence the cushions compress more for the same plate rotation. This would explain why I was not experiencing the movement behavior I was aiming for. It also explains why the truck wanted to shift instead of pivot. So in reality I need to hit the geometry correct on the first try since I won't be able to shim much.

That's the beautiful; thing about playing with actual hardware: You see things you never expected.
Working with the actual components teaches a techi what works and what doesn't. Lots of times the "dark art" is just hidden by misunderstanding.
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Old April 9th, 2017, 04:25 AM   #66
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Way back in the day I remember a plate called Microstar which had a unique action to it. I don't think it relied on cushions at all. Maybe DocSk8 has heard of it and knows more about it.
Microstar 2500. Used bearings in the plate for the axle to rotate in, and two big cushions on the side. It's a distant predecessor to the Arius. Heavy as all get out. I seem to remember the pivot angle on those was around 33. I have a pair that I got all torn down and serviced, but never put back together. Maybe I should.
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Old April 13th, 2017, 03:03 AM   #67
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To provide an update: I finally started the computer analysis. I started a new thread so I could refer to it in the future.

http://skatelogforum.com/forums/show...329#post725329

There are still a couple more features I want to explore.
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Old April 20th, 2017, 03:51 AM   #68
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Update:
Started receiving material.

I sent drawings to the machinist. I'm going to visit him next week to make sure my thoughts make sense. Usually these guys are crafty and have batter ways to set up the parts. So the drawings might change.



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Old April 20th, 2017, 10:53 PM   #69
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Update:
Started receiving material.

I sent drawings to the machinist. I'm going to visit him next week to make sure my thoughts make sense. Usually these guys are crafty and have batter ways to set up the parts. So the drawings might change.



Very nice!
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