Comet suspension

[John Emanuel]

Reply for John Emanuel, I don't consider myself brave for riding my rapide "standard". For the last 5 years it has been a fine companion over many thousand miles, never given me any trouble at all.(apart from maintenance) Rides hands off up to and including 90 mph. Makes me wonder what you all are worried about. If mine can do it, all as per factory, why can't the others.

Hello Roy,
It was said somewhat tongue in cheek, as I hoped the icon would suggest. However, I do believe that if the bike is driven hard on bumpy roads, sooner or later it will happen. As I said, I rode the bike for 15000 miles before it went berserk, chasing after my friend on his Norton Commando on a straight but bumpy road. On reasonably smooth roads I could get away from him with ease, but on rough roads he had a big advantage. After it happened, I rode the bike for another 20000 miles without a repetition. ( I did screw the steering damper down with both hands!!)
I'm not an engineer, but I enjoy making things and experimenting, so it seemed perfectly reasonable to attempt to improve the handling on the bumpy back roads of North Yorkshire and the Isle of Man. Back then, there was no thought of originality to keep its re-sale value.....it hardly had any!!
Best wishes
John

 

[ossie]

i dont think [lucky] is the right wording.
honda 4s and kawasaki 3s were all a bit of a question mark handling wise when they first came out but never got branded with watch it mate they will throw you down the road?
if he was still here Ron Owen- Pullen could tell you some tales.
he was a staunch vincent man,he also had all the latest bikes as they came into this country usually from reads of leytonestone.
he would come down teds cafe and give us a blow by blow impression of them and they were not all praise.

like roy i can take my hands off with the throttle lock on and the damper lightley pinched up it will go in a straight line just adjusting it with me knees.
i DONT do this going round bends etc.then you would be pushing your luck.
i can still do this after 46 years, even with the orders from the back seat [ pack it up] from the missus.
OSSIE
riding my bike the last this i think about is when is it going to eject me.
im to busy watching them phone packing motorists and there antics.

 

[vibrac]

i dont think [lucky] is the right wording.
honda 4s and kawasaki 3s were all a bit of a question mark handling wise when they first came out but never got branded with watch it mate they will throw you down the road?
.

When pushing a bike to its ultimate limits it is not always the best handling bikes that you want to be on. Take the Irish born (later Norton) featherbed, a good handling frame (not as good as the Egli but good for the fifties) but not a frame IMHO to have at the limit, my Manx let it all go without warning at Snetterton one day, one minute steady as a rock the next.... Another guy raced a Grey flash with great effect and the first race on his Norton fell off because it gave no warning -who was that?-John Surtees

 

[john998]

Hello, It took around 5 years for my rap to bite me, one dark night in 1968, on a straight road excelerating through 50 mph or so it picked me out of the seat. I landed on the road still in a riding position. knees out of the trousers elbows out of the riding jacket, bruises on the thighs where they hit the bars. The bike slid by in a shower of sparks.
At that time being an impercunious apprentice the bike was not maintained so well as now. I do feel that if you get all things lined up against you Girdraulics will generate more enormous force,than a hydraulic searing damper will cope with. Have fixed it now though, in 15 years of racing my Bramptons never gave the slightest worry. Will try to attach photos of 3 fork legs, as you may see all the holes line up a treat, would like opinions on the 1/4 holes in the neck of 2 of them, would you use them?

John.

 

[redbloke1956]

Hello, It took around 5 years for my rap to bite me, one dark night in 1968, on a straight road excelerating through 50 mph or so it picked me out of the seat. I landed on the road still in a riding position. knees out of the trousers elbows out of the riding jacket, bruises on the thighs where they hit the bars. The bike slid by in a shower of sparks.
At that time being an impercunious apprentice the bike was not maintained so well as now. I do feel that if you get all things lined up against you Girdraulics will generate more enormous force,than a hydraulic searing damper will cope with. Have fixed it now though, in 15 years of racing my Bramptons never gave the slightest worry. Will try to attach photos of 3 fork legs, as you may see all the holes line up a treat, would like opinions on the 1/4 holes in the neck of 2 of them, would you use them?


John.View attachment 1631View attachment 1630

Hi John, I would plug the holes and use them.
How did you straighten yours?
Kevin

 

[hadronuk]

Hello, It took around 5 years for my rap to bite me, one dark night in 1968, on a straight road excelerating through 50 mph or so it picked me out of the seat. I landed on the road still in a riding position. knees out of the trousers elbows out of the riding jacket, bruises on the thighs where they hit the bars. The bike slid by in a shower of sparks.
At that time being an impercunious apprentice the bike was not maintained so well as now. I do feel that if you get all things lined up against you Girdraulics will generate more enormous force,than a hydraulic searing damper will cope with. Have fixed it now though, in 15 years of racing my Bramptons never gave the slightest worry. Will try to attach photos of 3 fork legs, as you may see all the holes line up a treat, would like opinions on the 1/4 holes in the neck of 2 of them, would you use them?

John.

I agree the force generated by a hydraulic damper seems trivial compared to tank slapper forces, but it does increase at higher velocities, just when it is most needed, unlike a friction damper.
Reading the Cranfield and Imperial study, they say that road undulations that cause forced oscillations for 2-3 seconds are sufficient to initiate a tankslapper. It's in this initial phase of relatively low forces that a steering damper can be effective, by reducing the build up in amplitude until the road forcing is past.

 

[timetraveller]

With regards to john998's query about the extra 1/4" holes in the fork legs; from the photograph it looks at though they are on the centre line. If that is the case then that is known as the 'neutral axis' and that is where when a beam is subjected to a bending force the compressive and tensile force equal out. If they are on the centre line and are nicely finished then they will not cause any problems.

 

[Bill Thomas]

Sorry John998, I can't agree, I think that first bit of steady, That a Hydraulic Steering Damper gives, Stops it from Kicking Off, The other thing we have not talked about is Taper Roller head bearings, They also just damp it down a bit, The Funny thing is, My lightning was better with worn out fork bushes, It just shook it's head a little, But felt compleatly safe, Unlike Ossie, Every time I go out on ANY bike I think it will throw me over the top again, It realy messed me up !! Cheers Bill.

 

[john998]

Hello Kevin, sorry I should have been clearer, Just seeing if they where OK alignment wise, having read so much about forks in this thread. The main Spindle holes are in the centre line but the wheel spindle is set back so that a straight edge down the back of the spindles touches all three, but down the front the 1/2" wheel spindle is about 1/10" back.
No idea which clown drilled the holes, any where but there would have bothered me less. Not sure how I ended up with an odd number of fork legs. Thanks to Timetraveller, and yourself for comments.
John.

 

[john998]

Hello Bill, Yes I know what you mean, my little wobble was so instant, the bike just disappeared from under me. It was not a matter of fighting it, no warning just gone.
No hydraulic damper at that time. John.