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F: Frame Seat Dampers

Steve Morris

Well Known and Active Website User
VOC Member
Hi all, I removed the seat dampers from my bike Sunday, its a 1949 Comet 'C'. I need new damper inserts, the cloth stuff that goes inside the drum. Ive noticed the VOC Spares shop has them, so not an issue to get, but i also noticed they mention they are quite brittle and i guess care is needed to fit them?

Can anyone offer any tips/advice on fitting please? Do they need to be 'oiled' when fitted?

Many thanks,

Steve.
 

timetraveller

Well Known and Active Website User
VOC Member
Ask yourself how many modern cars or bikes use friction dampers for their suspension. This might have been acceptable in 1949 but most of us now think that friction damping is not a good idea. If you do buy the friction material then plenty of grease to cut down on the friction is a good idea or alternatively use PTFE, which has a very low friction coefficient, would help. A fully sprung seat and an AVO coil over will give you the best ride if you do not mind it looking non standard.
 
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Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Think about what the seat damper drums do. When they were introduced on the seres B the seat stay dampers were the only damper mechanism on the rear of the bike. When the hydraulic damper was introduced on the series C the factory kept the same seat stay and in my opinion that was a mistake as you then have a friction damper fighting against a hydraulic damper. On my Shadow I replaced the seat stay friction material with a bespoke bronze bush and so the only damper is the hydraulic one which can now operate on its own and it works great. On the Comet I'm putting together I'm thinking of trying something like PTFE which timetraveller suggests.
 

vibrac

Well Known and Active Website User
VOC Member

Ken Tidswell

Well Known and Active Website User
VOC Member
Ask yourself how many modern cars or bikes use friction dampers for their suspension. This might have been acceptable in 1949 but most of us now think that friction damping is not a good idea. If you do buy the friction material then plenty of grease to cut down on the friction is a good idea or alternatively use PTFE, which has a very low friction coefficient, would help. A fully sprung seat and an AVO coil over will give you the best ride if you do not mind it looking non standard.
they also have brass particles in the mix , it is brake lining material. My advice is to stick it to the aluminium casting so it can't wear the alloy and as has been already suggested grease the surface that somes in contact with the inner drum. the older stuff used bo be woven and was kinder to the components especially if they were greased, very anachronistic now but useful at the time our machines were first built with no rear damping apart from friction. Which has a linear response to movement.
 

timetraveller

Well Known and Active Website User
VOC Member
linear response to movement
Is that right Ken? I think that is only when it has started moving. It is the 'sticktion' before movement which tends to spoil things. PTFE is available with an abraded and acid etched face on one side so that adhesives can be applied. That would be my choice if I was to go down this route.
 

oexing

Well Known and Active Website User
VOC Member
PTFE has very low friction factor but pure teflon does wear quickly so is not used for bearing applications. You have to get a modified PTFE material for bearing bushes - that is not available as rounds. So better get some maintenance free plastic material like from IGUS or POM which should last longer. But really I don´t believe that stiction in these seat struts will be noticed much on the road compared to the sometimes very stiff hydraulic dampers. You are fighting at the wrong place , my guess.

Vic
 

Peter Holmes

Well Known and Active Website User
VOC Member
Having the seat attached to the rear frame member, and therefore mirroring the rear frames vertical movements, albeit at a reduced amount is probably not a great idea, especially if you take a pillion passenger often, the pillion passenger is subjected to far more unpleasant jolting than the rider, fully sprung by whatever means is definitely the way to go, sod originality, I would rather keep my wife happy, Happy Wife = Happy Life.
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
But really I don´t believe that stiction in these seat struts will be noticed much on the road compared to the sometimes very stiff hydraulic dampers. You are fighting at the wrong place , my guess.

Vic
Vic
My experience is the opposite.
My Shadow when I got it on the road had a Koni rear damper and std friction linings in the seat stays and the rear suspension was very harsh and stiff when riding. Lubricating the seat stay linings improved the action so I then removed the linings and made a bronze bush to fit in there and that transformed the rear suspension to a lot better and comfortable ride. Bronze may not be the best material but I had some and it only took an hour or so to make them. No change to the rear hydraulic damper was done.

So yes in my experience it did make a difference and that is not a theory or guess but found from actually using / testing the bike and no other changes were done. As far as I can tell the rear suspension on the Shadow now moves as well as my C Rapide which is fully sprung and so doesn't use the original seat stays.

Simon
 

davidd

Well Known and Active Website User
VOC Member
The original damper material was weatherstripping. It had no serious friction enhancers. It was easily available from automotive suppliers.

DSCN1305 (2).JPG

If you are looking for original replacements, I would start there.

I would think that Simon's solution works very well. phosphor bronze is a relatively high friction material without being constantly flooded with oil. Fiction material may be too high in friction and too delicate to work as expected. As Simon says, it is more of a trial and error test to find what works well for the rider.

David
 
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timetraveller

Well Known and Active Website User
VOC Member
A couple of things for completeness. Vic is probably correct that the loaded PTFE would be better then plain PTFE. Both IGUS in Europe and Pacific Bearings, in the States but with agents over here, are firms I have dealt with. The problem is that if one is trying to keep the original parts then some form of adhesion is probably required. The PTFE specially made for that is the only one I know of but there may be others. The other thing to note is that if one wants to keep almost the original appearance but still have a fully sprung seat then it is possible. The trick is to keep the original friction dampers but then support the base of them by two struts coming from two holes, one above the other, at the rear of the footrest plates. The magic can work because one is making a triangle, albeit a narrow angled one, by using two struts which start off about two inches apart where they fasten to the rear of the footrest plate. They can be through bolted to the central part of the friction damper. If the two supports are painted black then they hardly notice. All I can say is that by 1954 Vincents had fully sprung the seat and started to use a coil over damper. This was reportedly due to consultation with VOC members.
 
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delboy

Well Known and Active Website User
VOC Member
The original damper material was weatherstripping. It had no serious friction enhancers. It was easily available from automotive suppliers.

View attachment 39730

If you are looking for original replacements, I would start there.

I would think that Simmon's solution works very well. phosphor bronze is a relatively high friction material without being constantly flooded with oil. Fiction material may be too high in friction and too delicate to work as expected. As Simon says, it is more of a trial and error test to find what works well for the rider.

David
Hi David,
A useless snippet.
my old Ferodo agent told me years ago that it was known as "Bonrest" as it used to be used around engine compartments to seat the bonnet on car, to avoid metal to metal contact.
Regards, Delboy
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Wouldn`t it be possible to use a closed ballbearing in this place?
Erik
I looked at that and there isn't really enough room due to the position of the two bolts that secure the damper drums to the RFM. Its the smaller bolt that stops the drums rotating that is the problem and you would have to either move that bolt and so then have to redrill the RFM bracket or you would have to make an alloy seat stay casting that is larger to allow a bearing to fit.
I looked at needle roller bearings and couldn't find anything off the shelf, that doesn't mean one doesn't exist though.
 

oexing

Well Known and Active Website User
VOC Member
No need to struggle for zero friction in there I´d say. There is not a lot of motion in the strut bearing over full stroke of the wheel so some low friction material should be quite allright. Just get special plastic material for fabricating bushes and all is well. Below a link to IGUS for rounds for a simple lathe job - or find your local company which supplies anything like that.

Vic
IGUS rounds
 

Steve Morris

Well Known and Active Website User
VOC Member
Thanks all for your help and advice. I have decided to use the bonnet rest webbing and keep it kind of standard. The bike is only ridden on high days and holidays so its a good job for now!

Another question, the round bushing inserts, Ive seen a few pictures where the outside of these looked like it was painted red? Mine were painted roughly in silver hammerite but today when i cleaned the struts and bearings up i noticed some red paint on them? Should they be red??
 

vibrac

Well Known and Active Website User
VOC Member
I dont think anything on a Black Vincent was ever red which is why I always add a few touches of that coulor on the engine perhaps the horn and at the moment red handlebar grips
NB is this what happens to rebellion after half a century?
 

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