• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

FF: Forks Modified Steering Stem



chrislaun

Well Known and Active Website User
VOC Member
The damper could well be the problem, my twin with the 45s is usable with NO damper, the damper just being used to do it's proper job, just damping out excessive movement. The damper being used may be too stiff for such a light bike/rider giving the impression the springs are too stiff. Ask him to at least try it without, carefully of course.
Chris.
 

timetraveller

Well Known and Active Website User
VOC Member
Chris, the chap in Italy is using a Vincent damper. I doubt that will be too stiff and he has tried it without the damper. I have now heard from the chap in Italy as to his progress. Here is what he has written;

I have several old Ducatis and while hunting around for a spare part the other day I came across a pair of fork springs that looked vaguely similar to the Vincent ones. Presumably from a Marzocchi, they have an od of 1 inch and are made of 4mm steel just like your springs. The gap between coils is a bit smaller and decreases a little half way down, so they are definitely softer than the 30lb/inch springs, and about 10 cms longer. Anyway, I decide to try cutting one down bit by bit, starting at the 'soft' end, and when that showed interesting results, I started on the other one from the 'hard' end. So, to cut a long story short (!), I ended up with a 40cm spring on one side and a 43cm spring on the other, producing a more or less horizontal lower link when I sit on the bike, no topping out (with the long lower eyebolts now fitted) and a spring rate that feels pretty good. It's certainly softer than with the two full length 30lb/inch springs fitted or with the one shortened one, but with no danger of bottoming out. On the other hand, the springing is a bit more than the Vincent damper can cope with, so for now I've fitted my Armstrong, which has better rebound damping.

You will see that he is starting off with multi rates springs so that is not useful for the rest of us. I have considered multi rate springs for the JE mod but am not sure the company making my springs can do that.
 

chrislaun

Well Known and Active Website User
VOC Member
Thanks for that, multi rate springs are only made by winding sections of the spring at different pitches, the closer together the softer. The firm I used in Sheffield copied some Progressive springs for me many years ago which originally varied almost continuously their length but they made them with three different pitch sections as that was far easier, they performed just as well.
Chris.
 

oexing

Well Known and Active Website User
VOC Member
These days I am on the track for pneumatic shockers, like from Fournales. What I like is the complete adjustment for loads via air pressure that you set with a pump. Second, they say that the air volume inside gives a progressive damping towards full bump so no hard bottoming to be expected. Another plus is the small diameter of 50 or 60 mm , so no clash with top link on the Girdraulic. The company that has its roots in aviation struts seems to be prepared for special types - as in Vincent ?? Not quite so nice is the price, but then there is a lot of sophistication inside and overhauls any day. My idea is to hang one of them onto a Brampton.

Vic
Link to PDF
Another PDF
Concept Fournales
 

Flo

Website User
VOC Member
Having Worked on a number of air pressure base suspension and having lookes at the Fournales strut some 20 years ago, I'd be vera interested to hear about your results.

Frankly I am not entirely convinced of the sealed cylinder concept of air suspension.
 

Attachments

oexing

Well Known and Active Website User
VOC Member
Hi Flo,
would you care to give some more details as to what you did not like on pneumatics ? These are standard for many decades in aviation but , allright, aircraft don´t do a lot of mileage on the ground. Even so, the Fournales are in production for long time so should be tested. Comments are , as far as I found, very comfortable on common roads, not so much for motocross.

Vic
 

Bill Thomas

Well Known and Active Website User
VOC Member
I just Googled, Air Suspension for Harley Davidson, And there is lots there.
I used just one side of an H.D. rear, On the rear of my "D" Special late 1970 s, I think it was S&S.
I was very pleased, It stopped the rear wheel Hopping off the tarmac, When Braking hard for the hairpin at the race track, I also used it on the road.
Cheers Bill.
 

chrislaun

Well Known and Active Website User
VOC Member
I've have a pair on my Harley Softail that were on it when I got it, 20 years ago, I think they have a pair of bladders inside not relying on seals. There's some serious pressures involved, 375 lb in the compression side and 175 lb in the rebound.
 

greg brillus

Well Known and Active Website User
VOC Member
Not only friction but the geometry of it all. Like I have said before, I have never been able to install any of the springs without them being hugely "Topped out" this means that you have to shorten the springs, or at least one side. That last Comet I did, after i installed the 33 or 36 Lb springs with the front shocker left off, it would readily bottom out, well the outer spring case would hit the front of the lower fork lug. I did trim some off the inner and outer spring cases, the inners were like a knife edge at the top anyway. With anything but the softest action shock absorber on there, the front end felt heavy and stiff. It was a juggling act between springs and shock absorbers, ending with a pair of 45 Lb springs with about 25 mm chopped off both, and an original Armstrong shock absorber used. The Thornton I had (brand new) worked very well, but I would not part with it, the second hand Koni was probably a bit stiff (heavy) even on its weakest setting, and the AVO was way too stiff..............Anyone with an AVO on the front of their Comet is going to have a very stiff action front end no mater what springs they use, the bike simply does not have enough weight to overcome the set up of that shock absorber. I have used the stock Vincent shock abosrber, (I think this was one of the new ones available from the Voc spares co) at full extension it's action was very stiff, almost felt like it was locked up, until the suspension compressed with a rider on, and then it felt ok. It is possible with that design that at full extension the upper bushes in the shock internals are binding as the piston is trying to overcome the rod bushes friction, and this gets better if the shocker starts to move further down its travel. I would recommend he use another type of shocker. He needs to back off the spring pre-load, cut the springs down so the suspension is not topped out.......................This goes for all of you trying to install this setup........................... Done about 30 or so of these now...................
 


Top