Some contradictory info on CBH website

[drivermark]

I have some questions about some info that seems to contradict other info on the site and would just like a little clarification.
In the second part of the Springer Rocker Design article dated 5/4/2001 in the section on suspension geometry it states:

"control points #1 and #2 are always aligned along an imaginary horizontal line parallel to the ground regardless of the rake angle."
Control points being the rocker pivot points.

Then in the Good Mockups article it says


"The Rocker Angle"

We talked about the 120-degree rocker angle earlier and the reason Harley decided to keep the front and rear rocker pivots parallel with the ground line was because they determined it gave the best spring action back in the old days when rakes were in the 26 to 30-degree range and the sprung legs (fronts) were at a relatively shallow angle.

As time progressed and neck rakes started to increase builders found the the old parallel rockers did not produce good spring action so the rocker angle started to change by canting the front leg pivot hole upwards relative to the rear pivot point.

Sugar Bear was blasted in the media when he told a reporter that it was best to keep the rocker pivots parallel to the ground but his remark was taken out of context because what he was actually saying was that the starting point for rocker angle was parallel to the ground for a stock fork and this was how the jig should be set up. If you build every set of forks using the 120-degree angle the rocker pivot points will automatically be canted to the best position when the forks are installed on bikes having any conceivable rake angle as shown below.



Note that although the angle between the rear rocker pivot and the legs of the forks is always 120-degrees, the angle of the axle moves upwards as rake increases which is the way it should be for best suspension action. This also changes your axle height so the difference needs to be added to the length of the forks you order.


I'm a little confused, which way is the better way to set the rocker angle?

I read an interview with Sugar Bear a while ago where he did say that he set the rocker angle parallel with the ground mounted but in the full extension position and most of the writings I've found on the CBH sight say that is the way to set the rocker angle.

In everything I've seen on the sight UL/FL springers measured 19.5" from the top of the bottom tree to the rear leg pivot hole but in the Mockup for Forks section of the Good Mockups the measurements are 16.5" measured from those points and 19.5" measured from top of bottom tree to the rocker axle hole. Just wondering which of those is correct.

Lastly I could never figure out what was meant when I read that using dropped rockers "tricks the front end into thinking it is running a smaller front wheel" until I saw the diagram in the 2nd part of the Rockers article so thank you for that it clarified that point for me.

Not trying to stir up any shit I wanted some clarification.

[DKillam]

I'm just getting into my CBH springer build and have become a little confused myself on the whole rocker length/angle bit. I don't have an answer for you, but will muddy the waters some more, if you haven't seen it already:
http://choppercompendium.com/ccforum/vi ... 228055e923

Don

[drivermark]

Don,
I'm wondering more about the rocker pivot angle, that thread is more about trail and axle position.
I've built 1 of the CBH springers and it works great but the new articles (and the DA springer plans) contained "new to me" information that's different than was in the original plans and build article and was wondering which way would be better for the next one.
I know Gary say's to do research but the CBH sight is just about the only "Chopper specific" info out there and is the only one I've found that says anything about the "120* rule".
Link to pic of forks on my Softail-
http://www.chopcult.com/forum/attachmen ... 1628613152

[curt]

check on here for posts by krymis i believe , he was posting a lot of stuff about springers and rockers when i was building mine . some in depth stuff if i remember .

[drivermark]

Curt,

I've read and re-read pretty much all the posts on this forum about springer forks in the last 6 or so years and searched any and all info I could find on building springers but like I said above, the CBH sight and here seems to be the best sources for reliable info. All of the stuff I've seen by Krymis seems more to deal with the position of the axle as compared to the rear rocker pivot not the angle of the rocker pivots themselves. That and the rear wheel width math stuff that I don't really understand.
I guess the bottom line question in regard to rocker pivot angle would be .... What angle is the best to set the rocker pivots? Parallel to the ground at full extension or 120* off the rear leg at full extension?


Thanks
Mark

[curt]

it may take a while but i will be watching for this answer myself

[Jim Sawyer]

I just found this info that I had not seen before

https://chopperbuildershandbook.com/rockers-2.html

[drivermark]

Jim,
The quotes in the original post from that article and the Good Mock-ups article are the source of the confusion.
"Rockers" article said the control points are parallel with the ground regardless of rake angle and the Good Mock-ups "introduces" the 120* angle.
I say introduces because that is the first time I've seen mentioned on the CBH sight although Gary does mention it in a round about way in this old thread
http://choppercompendium.com/ccforum/vi ... d01c6b93db

So the question is still which method would be the best way to set the angle for the rockers? OR Am I making a mountain out of a mole hill so to speak?

[drivermark]

Ok I went back and re read the thread I posted above and it finally clicked I don't know how many times I've read that thread and never really understood what was going on in the diagram Gary posted but for some reason it finally sunk in.

I think it was this bit that finally lit the bulb

"Ideally what you want is for the sprung leg to be perfectly parallel to the rear leg at two point in this up and down movement. One point is at full extension and the other is at full compression. Between these two points the sprung leg pivot point will arc out slightly which is normal. This is why the bushing for the spring rod at the perch is a very sloppy fit, sometimes a full .03" oversized. It allows room for the rod to move without binding for and aft."

Don't know why it never registered before .

[Fossil]

When I wrote the second part about rockers I was primarily responding to people who had called or emailed and wanted to build a lot of semi custom Springers but did not have the resources to hand calculate the front leg length for each specific order for forks of different lengths to be mounted on bikes having different rakes. The 120-degree method is usually used in such circumstance.
I use 120-degrees while other builders might choose to use 115 to 125. It is a matter of personal preference.

[Fossil]

By the way there is nothing wrong with having the pivot points perfectly parallel with the ground in the static condition as there will be a little sag once they are mounted and carry the bike weight.