SP: Spring Boxes (Rear) Rear suspension springs

[Damien McGouran]

Hi Timetraveller.
I think the non standard look is already out the window with what I have (albeit I think it's a nicer look), I need to subtlety change the parts will allow me to ride the machine. This may mean, as you have suggested, mixing springs to achieve the desired result.

 

[Vinnie Boy]

Damien, the saddle front mounting is a pivot point. You must maintain some clearance between the underside of the saddle and the UFM or a fracture will occur for sure.

VB

 

[Damien McGouran]

VB,

Many thanks for pointing that out, I would suggest that the movement is minimal but nevertheless I will factor that in to my modification.
Cheers
D

 

[timetraveller]

Vinnie Boy is right but if you fully spring the rear of the seat then there is little if any pivoting motion at the front. Vibrac on here has the neatest and most robust fully sprung seat system I've seen. It depends upon your skills and availability of material. I just use solid tubes between the rear of the seat and the rear of the pillion footrest plates

 

[Damien McGouran]

For piece of mind (my mind), does anyone have spare original Vincent rear springs lying around? Initially I would ask if the diameter of the material that is used to make the coils could be measured to see if the part numbers and their descriptions are related.

To me, the measurements do make sense, ie, thinner wire used for the Comet/Meteor and heavier wire used for the Sidecar.

I have added the metric conversions to help with those of us that only use metric
F84/0 (.324") or 8.2296mm Sidecar
F84/1 (.300") or 7.62mm Rapide
F84/2 (.276") or 7.014mm Comet/Meteor

 

[timetraveller]

Damien, a coil spring is somewhat similar to a torsion bar, The thicker the wire, the stiffer the spring. The wire diameters shown are in the right order.

 

[bmetcalf]

https://www.therangerstation.com/tech_library/coilspringrate.shtml

 

[Bill Thomas]

As Greg said the other day,
I don't think there are many Comet ones around now ?.
Trouble is an OLD standard spring from under the bench will I think give a hard ride ?,
A lot of us have done what T.T. said and made the seat fully floating , Like a poor man's "D" !.
But you have to watch the seat does not bang on the mudguard.
There is now on the market an Avo Coil over spring unit,
I think they do a shorter one for your problem ?.
Cheers Bill.

 

[ray vinmad]

Modify your seat with your spring boxes removed &the bike on it's wheels or rear stand.
The damper will then be fully compressed & you will be able to see if the revised seat & tool tray clear the mudguard.
Ray

 

[Bill Thomas]

I converted a "D" to a "C" using an AVO coil over,
A single unit in stead of two spring boxes and a damper,
I could not tell the difference !.
Cheers Bill.