Ikon Shock Springs.

Not specifically for roofs, its another way of referring to components. EG members of a club, pieces of a whole. It's common to refer to individual structural members, beams and columns as parts of a whole.
In trusses, its individual bits are called members, from memory chords and I forget and each bit combines to make a whole truss.
 
Vince, you will be very surprised to discover than what uyou thought was 50mm of travel will actually be quite a bit more in wheel travel.

An easy way to get a basic idea would be to measure four distances on your Lav: 1) from swingarm axle to top shock mount, 2) from swingarm pivot to lower shock mount, 3) from lower shock mount to top shock mount and 4) from swingarm pivot to rear axle.

Divide them all by, let's say 2 (or whatever, so the lines will fit on an A4 sheet of paper) and draw up a triangle with an extended line to the axle. Try to get the to-ground (horizontal) angle of the swingarm pivot to the rear axle close to that of the bike off the stand, without sag.
Draw part of a circle using the swingarm pivot as the centre and the axle as the outer circumference (you might be able to use a dinner plate or something with the right circumference for this). By duplicating the concept of the shock shortening to different points of compression (length of the line between the lower and upper shock mounts), you can replicate rear wheel travel.
Draw a scale along the side of the A4 sheet. Referring to that scale will give you the rear wheel travel (don't forget to multiply x 2 - or your division factor above - for actual).
 
I remember seeing a drawing of a Laverda frame somewhere, showing the basic dimensions. Can't remember where I saw it, or whether it was a 3C or something else.

If anyone has the 3C frame dimensions, I could do the swing arm travel in CAD.
 
Yes Q that's the plan,punny. But I bet with the shock stroke at 76mm and it being so close to the wheel centre wheel travel with be maybe 100mm at most 120mm and I really doubt that and again as a percentage with the wrong spring, I am not getting even close to that movement. We will see.
 
A couple of clarifications, it's really hard to get accurate dimensions around mufflers etc so these are as good as I could estimate. All dimensions are horizontal and vertical unless I say not, all dimensions are with both wheels off the ground the bike is at the moment on 20mm timber blocks under the centrestand so I added bits of timber to the tape measure where it was used down to measure to the ground. It should be close to correct, within 3 or 4mm. This is for a 3c with vertical shocks and my shocks are a bit longer than standard.
Centre of swingarm to rear-wheel axel centre = 480mm
Centre of swingarm to centre of rear shock bottom bolt = 425mm
Ground to centre of swingarm pivot = 355mm
Ground to centre of rear shock bolt = 365mm
Ground to centre of rear wheel axil =320mm
Ground to centre of upper shock bolt =735mm
And the only raking dimension is
Centre of swingarm pivot to upper shock bolt centre on the rake is = 495mm
Icon say the shock travel is 76mm.

Doing the drawing to scale wouldn't result in much accuracy, hopefully, Cam will use his CAD package and get a result. Seen Architects use it and it's pretty impressive. My bet is 110mm of total wheel travel if the rear suspension is working correctly. By persentage, if I loose 1/3 shock travel that obviously means 1/3 of wheel travel is also unusable with this to hard a rear spring.




 
Be interesting to see what effect the later layed forward shock mount had. It was the first attempt to increase rear travel when long travel became the big thing in dirtbikes in the late 70s. It's the same length shock use standard in both applications.
My bike has slightly longer shocks so my dimentions don't help. In the dirtbike world, they did it to use much longer shocks with more travel and not end up with crazy high seats. Laverda seat hight didnt change, the same length shocks were used. Other than style what's the advantage.
 
That's helpful but I couldn't see the upper shock mount position in that diagram, so early or later frame?. I suppose that swingarm dimension is to halfway in the wheel position slot? My shocks are a bit longer as well.
 
I see an upper shock mount (in the upright position).
The fact that a grab handle is shown indicates it does not have laid down shocks, as that would clash with he grab handle.
 
Wrong again by me, but no dimensions are shown to locate it. At least it's definitely more accurate than my bending tape measure and eyeing offsets.
 
Using Vince's dimensions measured off his bike, I did the diagram below.

The shock length came out a bit longer than usual (I think normal is 360mm). Is that about right for your shock Vince?
Anyway, the suspension travel is around 88mm.

It won't make much difference if the measurements are a bit out. The ratio of shock compression to axle travel won't change much.
 

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Thanks, Cam, can you do one for the std shock and later racked top mount to see what effect that has. Buggar me 88mm is not that much to absorb big bumps. Take a 1/3 out and that's 58mm.
 
385mm c/w 360mm - seems a fair amount of diff. From your diag, Cam, it looks as if the wheel tangent pretty much duplicates shock tangent (for want of the correct term!). In the laid fwd pos I would definitely expect more wheel travel for a given shock travel.

I'll be interested to compare my SF setup. With std swingarm, when I added fwd mount shock mounts and I think I added about 15 or 20mm to ride height to compensate for the softening effect and sag. New Honda swingarm has mounts further back but higher, so will be interesting to compare. I'll do my A4 version and report back.

Vince, with decent shocks you shouldn't really be aware of jarring from the rear end, so sounds like softer springs are definitely required. Laying your shocks fwd will certainly improve the ride quality; it should increase the effective 'zone' of suspension usability. If you have top mounts available on the bike, why not try them?
 
Piranha Brother 2 said:
If you have top mounts available on the bike, why not try them?
Click to expand...

Even if you don't, it's easy enough to make some additional mounts and weld them on. I did that with the RGS based mongrel racer I built. Even fitted a plate to allow for intermediate adjustment a bit like Velocette's famous slot adjuster.  I positioned the holes so they jack the suspension up the further forward you move the shock, to account for the effectively reduced spring rate. The mounting bolts for the plate can also be used as shock mounts, the upper left in the photo below being the original shock mount. So there's 6 different positions to play with.

Seemed to work pretty well. Race pilot Rick preferred the middle hole, I used the back one because I'm quite not as light as him.

When I say I'm not as light as Rick, some might call me a fat bastard, but I prefer to think of it in engineering terms. I've noticed some significant aspect ratio drift as I get older.
For the non-engineers, aspect ratio = height/width.
 

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Icon sells a steel top section that's a bit longer than the standard alloy bit and I had then fitted when the shocks were rebuilt. I made something similar to Cams gadget but less adjustable to see what effect jacking the rear had problem was I didnt want to weld it on so it was boltable and to avoid any rocking on its mount with its one and only bolting and to allow its fixing bolt and the shock bolt to fit it ended up jacking the rear about 35mm. My first couple of rides around the block were interesting. It steered MUCH faster, too fast for my comfort and the seat was stupid high.
And then I found that Icon bit and that was either 15 or 20mm and that did what I wanted.

The whole point of this tread is my bike lately isn't handing the way it was and not to my liking. It has a distinct hing in the middle feel that wasn't there before, even when I had all those broken spokes in the rear wheel it felt more stable. And I think it started with the harder rear shock spring going in. That's my guess, other suspects are my oddball tyres wearing to where they are causing it or the swingarm bearing are suddenly causing it or my newly spoked rear wheel is causing it. It's not absolutely horrible, it just feels looser than before. Not as confidence-inspiring as it was. So I will fit the softer springs when they arrive and see if that fixes it. If not I will move to the next suspect. Ever change I have made I test and usually, it's for the better, this has me stumped as to why it's suddenly happening. What's even odder is its intermediate, bike feels good for a while on a ride and then it starts tram tracking or moving around slightly with no input from me. Hing in the middle, I cannot detect any play except that tiny bit from the now replaced wheel bearings.

 
Just rang Icon to see where my spring is, they rang the spring maker in Liverpool and he hasn't made it yet. 3 weeks and zero done, that 3rd phone call from Icon finally lit a fire under him and they apparently will get it tomorrow. And then Icon powercoat it and send it to me, sometime next week, MAYBE
 
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