shim question

Joined
Jan 2, 2001
Messages
416
Likes
0
#1
I have been reading this great info site of shimprogramm and was wondering about one part of it.
I already asked Kevin about it, but maybe you guys can have a go also.
It was the part were the shimstack is altered to gain lowspeed without affecting the highspeed.
The deal was to take 2x 40.2 out and put 1x 40.3 back in to accomplish this task.
My point is: how can there be an increas of lowspeed of 25% and it won't affect the highspeed?
When shims bend they bend non-linear. When the force is already 25% up at the beginning how can it decrease later on?
The rest of the stack was not altered. Only above shims.
 

marcusgunby

Lifetime Sponsor
Joined
Jan 9, 2000
Messages
6,450
Likes
2
#2
Because the shim deflection is now low with a 0.3mm shim-so it doesnt get the large shim deflection it would with a 0.2mm shim, therefore the high speed isnt increased, as the shim doesnt bend enough to get to the part where it really gets stiff.
 
Joined
Jan 2, 2001
Messages
416
Likes
0
#3
In the programm it reaches the same deflection stock stack compared to the altered stack. So it start with 25% plus and then when deflection increases tapers of again to approx 0 %. It wld mean bending one 0.3 shim intially is tougher than 2x 0.2 shim, i can agree with that. But bending it more and the 2x 0.2 shims are harder to bend. It this the idea??
 

marcusgunby

Lifetime Sponsor
Joined
Jan 9, 2000
Messages
6,450
Likes
2
#4
Its the other way around, two smaller shims bending with big deflections wont produce the resistance a thicker shim does.Not sure on his program , i dont understand alot of the things it produces, i guess you either believe its answers or not.
 
Joined
Nov 8, 2003
Messages
200
Likes
0
#5
Come guys
The stiffness of a shim is relative to the cube of its thickness.
1x1x1 = 1
2x2x2 = 8
3x3x3 = 27
Therefore it takes 8 x 0.1s to equal 1 x 0.2
Marcus, never just believe.
The stiffness of the lowspeed affects all velocities. By increasing low speed you add to the total damping co-efficient.
Terry
 

svi

Member
Joined
Dec 7, 2000
Messages
126
Likes
0
#11
Georgie,
It all depends on what lift you class as high speed.
I personally don't look at any figures above 0.020 lift and really concentrate on figures up to 0.0120 lift. I don't think that the stacks are lifting up to 0.0420 which is the range available, but the shaft speeds I use it for are a lot slower than Marcus posted.
 
Joined
Jan 2, 2001
Messages
416
Likes
0
#12
When you looking at deflections being so little, lowspeed and highspeed will also influence each other in my opinion. I wld say the only way to go is altering the seperator shim.
Any other way will affect the whole stack.
 

MSracer

Subscriber
Joined
Feb 5, 2003
Messages
63
Likes
0
#14
Kevin is now measuring actual deflections to tie things in with the program , dyno and data recorders. The way he is going about it should give accurate measurments of deflections.
 

svi

Member
Joined
Dec 7, 2000
Messages
126
Likes
0
#15
Marcus,
I use the program as a "guide" only to relative shim stack stiffnesses on what from experience and knowledge from other sources I expect the lifts to be.
The figures it produces do not really mean anything by themselves, there are no magic answers contained with in them. It's like a lot like data logging it's a usefull guide but it won't give you any answers by itself.