Comet Rear Suspension
- Thread starter Howard
- Start date
You've lost me with that one. Don't you need a longer damper to stop it bottoming out? H
I mean short in the sense of having a small closed length, allowing more room for spring compression. A damper that was short in the sense of having limited travel would not be helpful! Producing a damper with a short closed length but a long travel was the reason for the offset RFM mounting of the AVO rear dampers.
I have always understood "bottoming out" to mean the suspension has hit some mechanical limit that prevents it from compressing further, be it the spring going solid, the damper bump stop, or the mudguard hitting the seat.
Similarly, when the suspension hits the limit of its extension, it is "topping out".
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Hugo,
Thank you for the information. I did not have it at hand, but I found my notes on the Thornton springs and the details are:
Free length: 9"
Active coils: 12.5
Wire diameter: .247"
Spring diameter: 1.89"
Mean diameter: 1.64"
Rated: 90 lbs/in
Calculated by formula: 101 lbs/in
Tested by scale: 100 lbs/in
There as also a 6" long 70 lbs/in helper spring which would nest inside the larger rear spring (one or both). So, the adjustability was good. I see why I selected a 200 lbs. spring for the coil over on the racer.
I considered making a Thornton rate spring in an open end as opposed to the closed and ground end. I was then going to thread an aluminum plug for the pitch of the spring and wind it in. By plugging the end of the spring I could thread in the spring eyes and end up with a set-up that was quite close to the original in terms of the springs holding the spring boxes together. I would have needed to adjust the spring rate for using up some of the active coils with the end plug. Because it is expensive for me to get prototype springs I simply went with the coil over.
For those of you who may not have seen one, this is the Thornton coil-over:
David
Thank you for the information. I did not have it at hand, but I found my notes on the Thornton springs and the details are:
Free length: 9"
Active coils: 12.5
Wire diameter: .247"
Spring diameter: 1.89"
Mean diameter: 1.64"
Rated: 90 lbs/in
Calculated by formula: 101 lbs/in
Tested by scale: 100 lbs/in
There as also a 6" long 70 lbs/in helper spring which would nest inside the larger rear spring (one or both). So, the adjustability was good. I see why I selected a 200 lbs. spring for the coil over on the racer.
I considered making a Thornton rate spring in an open end as opposed to the closed and ground end. I was then going to thread an aluminum plug for the pitch of the spring and wind it in. By plugging the end of the spring I could thread in the spring eyes and end up with a set-up that was quite close to the original in terms of the springs holding the spring boxes together. I would have needed to adjust the spring rate for using up some of the active coils with the end plug. Because it is expensive for me to get prototype springs I simply went with the coil over.
For those of you who may not have seen one, this is the Thornton coil-over:
David
That Coil over is a super looking job, Looks fine on your racer, But for the road it just don't look right, It's a shame somebody can't make a pair to go like standard in black !! Who would have thought I would say that !! Cheers Bill.
Mine doesn't look too bad on a road bike and non-Vincenteers are impressed that I've got Kawasaki Mono-shock/Uni-track rear suspension. The Knight also has monoshock but it's hidden from others on all but the worst of days.
Hello Ian, Show us a photo, Maybe I was wrong, Cheers Bill.
Hi Bill,
Your request is not forgotten or being ignored - I'm just ineffective. A friend brought a camera around yesterday and, being a gentleman, I raised the seat. That was when he found that the rechargeable battery had insufficient power to take pictures. Not only am I ineffective, I pick matching friends!
If your C Vincent is handling poorly when laid over on bumpy bends check your dampers if the originals . If these , especially in the rear is partually empty of fluid and has a loose or undamped part of travel and most do , this is the reason . Rebuild with fresh Viton o rings and fill with 30 / 40 wt. tele shock fluid does wonders at improving rear end control . There is a way of eliminating the floating undamped portion of the damper travel , and this transforms the suspension action . Or fit more modern damper units . Armstrongs were far better. Sid .
Sid, what is your recollection of Armstrongs used on the back when they were new? Were they on the soft side?
When we dynoed my Armstrong and Vincent dampers (Don Alexandra rebuild), the Vincent was much firmer.
I agree Armstrongs were very good, both for longevity and for a smooth continuous action. Mine still has a perfect action in spite of being made in 1956.
But it is a bit soft, even when used at the front, so a lot too soft for the rear. So I wondered how much that is down to age?