Comet suspension

[Bill Thomas]

Hello Kevin, I was sure they should all be inline, But i have just checked 2 sets, One set on the bench in bits, Which is more easy. Sorry, But do check yours again, It is easy to make a mistake. I have done a lot of work on Vin' forks, I am Not a Fan ! Good Luck Bill.

 

[sidmadrid]

I have just run a string line between the centre of the top and bottom links (through the centre of the forward pivots) and down to the front axle, the centre of the axle is approx 3/4" behind the string line? Should they all line up?
Kevin

Kevin, my other Comet is fairly unmolested and I have had it for 30 odd years. The axle and two spindles are all in a line.
But do more research before you do anything rash. Sid

 

[greg brillus]

Hi all, yes can confirm that the centerline through the spindles and lower axle should indeed be in line. Just checked five sets and 4 of the 5 were in line whilst the last ones were out by nearly 1/2 inch at the axle end......Oh well looks like another jig to be made to straighten them. Can anyone confirm this to be an ok method.....heat the main area to be staightened to say no more than 300 Deg celcius, then on a jig, press the bend out, and let cool....odviously the heat will anneal the area, and allow it to bend easier, but would it really need to be heat treated again, or are the blades strong enough anyway....Cheers ...Greg.

 

[redbloke1956]

Hi all, yes can confirm that the centerline through the spindles and lower axle should indeed be in line. Just checked five sets and 4 of the 5 were in line whilst the last ones were out by nearly 1/2 inch at the axle end......Oh well looks like another jig to be made to straighten them. Can anyone confirm this to be an ok method.....heat the main area to be staightened to say no more than 300 Deg celcius, then on a jig, press the bend out, and let cool....odviously the heat will anneal the area, and allow it to bend easier, but would it really need to be heat treated again, or are the blades strong enough anyway....Cheers ...Greg.

Hi Greg, Thanks VERY much for checking that for me and you took the words right out of my mouth mate re: what can be done, I have done a little searching through the threads and found http://www.vincentownersclub.co.uk/...des-straightening&highlight=girdraulic+blades
Some of the reccomendations are quite in depth from a technical standpoint and a little disconcerting in the sheer quantity of technical expertise required to get the job done (straightening a pair of forks).
One thing above all others that impressess me about the VOC club and it's members is the wide and deep range of combined knowledge that members are willing to share readily...from quick fixes to advanced metallurgy!!..well done guys!!
I suppose the question that springs to mind immediately is whether one could use the forks as they are, assuming no other damage has been done during the "incident?" that bent the forks initially. Phil Irving tells the tale of a test ridden Vin plowing into an Austin A30, bending the car quite severely in the middle while the blades remained serviceable?

The other issue is that the rear of the front guard makes contact with the mag cowl once the forks are extended fully while on a jack (hard enough that the handlebars cannot be turned), I would guess that the likelihood of that happening in normal riding to be improbable (but not impossible) what if, however, the front damper could somehow limit the full travel of the forks? especially (as in my case) you had the shorter springs fitted?

I thought I was days away from registering the Comet but one step forwards and two steps backwards it seems, I would really appreciate any feedback available on this issue.......what have you done with bent blades?
Greg, let's hope that your idea is workable!!

Kevin (in tears.....again)

 

[redbloke1956]

Bruce,

If you look at the blue 110 lbs spring and compare it to the stock D spring, the D spring is at 464 lbs at midway and 653 lbs at full bump. The short springs are slightly softer at midway, 330 lbs and the same at full bump, 660 lbs. So, the short spring has no preload in the first half of its movement and is "softer", but as your fork compresses, the rate of the short spring catches back up to stock and finishes at the same load.

To get back to the Comet, I chose 150 lbs. by using two 75 lbs springs. The stock Comet spring for the Bramptons was 160 lbs. I went ten pounds lighter because I was trying to accomodate all the singles, including the Grey Flash, which weighs 100 lbs less than the 400 lb Comet. Jan Wiley has used the short Comet springs for years and neither she nor the people who have ridden here Comet have found any fault. As a result, neither Sam nor I saw any serious issue with the set up.

It may well be that this set up is on the light side. A red and a blue spring might be a better set up, particularly for boys. It is a major reason that I had several springs made. There is no other way that I know of to adjust the ride height on the front end, so even though it may require another spring, it is a very small price to pay for the improved handling and limiting the prospect of a wobble.

Just as an aside, the damper determines the fork travel. The length of the outer spring boxes vary wildly. Mine looks like Kevin's, but I have never bottomed out the racer. The distance between the spring box attachment holes when the fork is at full extension varies quite a bit from bike to bike. There should not be any "play" in the spring box and you should have to compress it slightly to mount it.

David

Thanks for all your shared knowledge David, you mention that the damper determines total fork travel, having not yet dismantled a damper can you tell me if there is a way to limit the total travel of the damper and therefore mitigate the issue of the rear of the front guard contacting the mag cowl when forks fully extended?

Regards
Kevin

 

[redbloke1956]

Hello Kevin, Is the mudguard fitted ok ? Does It look right ? It does from what I can see in your photo, I think you had that trouble befor you fitted the new springs, Don't ride it till that guard misses it . Give us a photo of the lower damper fitting, Cheers Bill.

Hi Bill, thanks for the response mate and yes the problem was there with the original springs as well!!

 

[redbloke1956]

Looking at my Comet, I would say the bottom link is horizontal ish in a normaly loaded situation. Yours is pointing skyward.
Springs too short, springs too soft?
On another vein, my Comet had a serious frontal in its life. After the wheel rebuild the front mudguard touched the mag
cowl when the front was jacked up. On very close inspection found the girdraulic blades were bent. Straightened and tweaked them on a hydraulic press. Might be worth putting a straight edge down the centre line of the spindles. Sid.

Thanks Sid, spot on, the blades are bent, what process did you use for straightening?
Kevin

 

[Big Sid]

Compare your front fender bolt up location on the fork and the lower rear fender brace with others . Might it be improperly sited too far rearwards ? Fender brace itself too long ? Incorrect fender ? Sid .

 

[Bill Thomas]

Hello Kevin, Sorry about your forks, Please don't use them as they are, I have done a lot of checking of these forks, And the Trail gets a lot less between full up and full down, OK in the middle, I would guess the trail was even less when bent like yours, Which would make the bike dangerous. Good Luck Bill.

 

[Big Sid]

Another suggestion re contact with the mag cowel . Might the flat stay short plate ET 186 be non original , too long ????
Remove it and see if the cowl can be rotated further back towards the magneto . If so shorten that flat stay . Easily done . Sid .