Darmah damper rod

Post your 'Chassis & Suspension' FAQs, comments & questions regarding Ducati motorcycles here.
Post Reply
pigmilker
Cucciolo - the Lil Pup
Posts: 6
Joined: Fri Jan 04, 2019 5:51 pm

Darmah damper rod

Post by pigmilker » Thu Oct 03, 2019 8:02 pm

Can someone tell me the purpose of the spring on the dampening rod

wdietz186
Cagiva Alazzura
Posts: 703
Joined: Sun Sep 10, 2006 5:40 pm

Re: Darmah damper rod

Post by wdietz186 » Sun Oct 06, 2019 8:31 am

It is a bottoming spring, to soften the jolt if all the travel is used up on a sharp bump. Its rate is much stiffer than the main spring.

ducadini
860 GT / GTS
Posts: 251
Joined: Sat Jul 31, 2004 9:54 am
Location: Antwerpen

Re: Darmah damper rod

Post by ducadini » Mon Oct 07, 2019 12:09 am

I don't think so !
The spring is for when the fork is completely extended (like when doing a wheelie :rad: :rad: ) to prevent a hard metal/metal contact.
It is a bottoming spring, to soften the jolt if all the travel is used up on a sharp bump. Its rate is much stiffer than the main spring.
That part is done by the aluminium (or iron) part fitted at the bottom of the moving part of the fork.
It has a conical top so the oil is forced through a increasingly smaller diameter in the last cm of the travel and thus creating a hydraulic lock.
Bottoming out of a fork is usualy when there is nothing of fluid left in it, then it becomes a real metal impact.
Of course we are talking about old Marzocchi/Ceriani stuff, aren't we ?
Those new fancy inside/out/upside/down things are something different.

ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

ducadini
860 GT / GTS
Posts: 251
Joined: Sat Jul 31, 2004 9:54 am
Location: Antwerpen

Re: Darmah damper rod

Post by ducadini » Tue Oct 08, 2019 11:21 am

Took some time to find a the right pics to clarify.
Marzocchi and Ceriani have similar builds, nothing interchangeable though.
Bottom of the pic is the damper unit, on the right is the piston that moves up and down in the forktube.
The left is the flow restrictor, (the ally part, the washer with the bronze slider, the small spring, the piece where they fit in and the washer to hold it in place in the bottom part of the forktube with the circlip on the left.
cerianiguts.jpg
When all these parts are fitted in the forkleg it looks a bit like this.
kayaba%20%20marzocchi%20001_edited.jpg
Bottom of the pic is the forktube with the parts fitted inside, the damper sticking out.
On the left side of the pic is the hydraulic lock : when the fork is compressed, the conical part slides into the ally bush (secured with the circlip) and create an increasing brake to prevent metal contact fully compressed.
The lower forkleg is bolted to the damper unit with the bolt on the left.
PIA to unscrew it : there's nothing inside to clamp or put a wrench or key on. Enter air-stuff.
marzocchi_fork1.jpg
Here's the complete exploded view of a Marzocchi (with a few more pieces : the piston on the damper unit has a "ring"47 with spring 50 to seal better instead of the plain piston of the first pic.
The "wheelie-spring" is 43

Hope I didn't mess up the stuff, Kevin Cameron is MUCH better at explaining this :-D

ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

Post Reply

Return to “Chassis & Suspension Shop”