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ET: Engine (Twin) Shock Absorber

Joe

Website User
Non-VOC Member
Hi Joe, "clutch judder" is often down to broken springs in the ESA. I should check that it's OK before you start on the clutch. Cheers, Stu.
Hi Sut,
what I am not happy about is when accelerating (motor torque) there is some little ratte synchrone to motor revs so I checked ESA and just found to my surpise that one of eight inner spings PD27 was completely MISSING !

Q1: Is it possible that a single inner spring missing out of 16 can cause a noticable effect?
Q2: or might this come from wear of sprocket ET60/1 and PD3/2 - see pictures?

thanks for feedback
Joe
 

Attachments

stu spalding

Well Known and Active Website User
VOC Member
Hi Joe,
It's unlikely that 1 missing spring will make a difference if the rest are ok, trying to diagnose primary drive problems at long range is very difficult as there are so many variables. Best of luck. Cheers, Stu.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Just wondering if you have "pinking " ?, Ignition a bit too advanced ?.
If you have an old Magneto and the points are too wide, You could try closing them a touch ?,
To retard it a bit, Sounds like you are getting there. Cheers Bill.
 

oexing

Well Known and Active Website User
VOC Member
. . . . well, I´d say . . .typical. Looking at the wear in some places you could try three positions for optimal fits of lobes . Maybe you can find marks that correspond to marks on the other part. That would be the one of three options that was in use for last long mileages. But then I don´t have ideas about your observations on the road.

Vic
 

greg brillus

Well Known and Active Website User
VOC Member
rotate the crank back and forth to see if you can "Feel" any backlash.......It is possible the keyway in the crankshaft on the right side and the crank pinion has movement in it. This can cause quite bad low speed knocking sounds from the engine similar to a big end bearing gone, had this on a few engines now.
 

Bill Thomas

Well Known and Active Website User
VOC Member
I get more worried by the wear on the inside now they are getting old !.
If you put it together without the springs and see how much end float and rocking, You get and the alignment
for the chain.
I would put it back for another 100,000 miles !.
 

Gary Gittleson

Well Known and Active Website User
VOC Member
rotate the crank back and forth to see if you can "Feel" any backlash.......It is possible the keyway in the crankshaft on the right side and the crank pinion has movement in it.
I'm curious about this. You speak of the keyway on the "right side". That's the timing side. Is that what you mean?
My bike (D Rapide) has a bit of a knock on take off in first gear. I've been assuming it's a bit of piston slap but maybe it's what you're referring to.
Gary
 

oexing

Well Known and Active Website User
VOC Member
Now that would be another slap on that ESA, from me as you´d expect, once again: Could that knocking be from bashing the moving part of the ESA onto the end plate when all stroke of the ramps is used up - as is typical in this case and no amount of springs will prevent this ?

Vic
 

greg brillus

Well Known and Active Website User
VOC Member
Gary, with the timing cover removed and the bike on it's rear stand and in gear.......if you rotate the back wheel and watch the E 80 nut that secures the half time pinion.......you will observe the nut moving and the gear not so much.........this is movement in the keyway, and this can happen for various reasons. This back lash creates a noise in the engine mostly noticeable at low engine speed that sounds bad.........The first time it happened to me on the racer back in about 2015 or 16 and I thought for a moment that the big end had gone, i have found it on other road going Vin's since then........not common but still happens. On the ESA's well another common issue that can be ignored at the time, is the actual compression of the springs........this not being enough.......Either the cam sleeve of the face washer is incorrect (perhaps a mismatch of parts used) who knows, but i have found on many bikes that when the ESA nut is tightened, that the actual compression of the springs is not enough. This must cause the springs to compress too readily causing the cam to "Ramp up" too soon. This is probably a major contributor to Vic's complaints about the design. On some engines I actually cut a piece off the cam sleeve to allow the springs to compress more, but it also depends on which washer combo you are using against these springs as well.
 

timetraveller

Well Known and Active Website User
VOC Member
and no amount of springs will prevent this
That is not quite right Vic. Several years ago Dick Sherwin fitted an Australian ESA to his 90 bore Black Knight which had a sidecar fitted. These ESAs have more springs than the standard Vincent one. After several months the ESA was taken apart and despite the fact that the bike plus sidecar had done several thousand miles there was only wear right at the bottom of the ESA cams. The ESA had not been getting anywhere near to the top of the cam profiles. A couple of springs were taken out and more movement was obtained. The cam profiles were very similar to the original Vincent ones.
 

oexing

Well Known and Active Website User
VOC Member
Norman, you may be right about that Australian special but I´d first want to see a picture of it before believing it. Must have been very different from original. I am quite sure you cannot have that spring preload from original Vincent ESAs so as not to slam the end plate , the cam shape is just not fit for purpose - as Neville once observed with bang/left-bang/right stops when playing the throttle. What makes matters even worse with unhealthy preloads on the poor ESA resp. the sprocket face is all loads from springs plus extra thrust from torque of crank acting on the cam slopes goes onto the inner race of the outer main bearing, wearing both the sprocket and the race. Only minimal area there for taking all wear and load, the radius on the inner race reducing it even more. Looking at the Vincent ESA the angles of the gradients don´t get steeper than 35 degrees when lifted. The BMW cams approach 60 degrees and this fact makes the progressive action almost self locking approaching that steepness, not much depending on springs near block length and not adding much extra load onto the bearing inner race. Self locking on steep gradients is well known from worm drives: You can turn a typical worm drive from the worm but the drive self locks when trying to turn the worm by the crown wheel. That was the reason Sunbeam inline twins had to have two start extreme pitch worms in the rear drive. Otherwise you would not have been able to push the bike with engine stopped when the crown wheel drives the worm.
Anyway, all efforts to get the old ESA do its real purpose by adding high spring forces are just bad engineering by not understanding - or ignoring - basics of face cam shock absorbers. Old habits and thoughtlesnesses die hard when engineers just take over from old times , accepting too fast all to be good enough - that´ll do - without thinking.
Just came to an idea for those poor souls running the stock ESA : Target is to prevent the ESA from bashing the end plate hard, the springs will not do it alone -as everybody knows. You could do a test with taking out maybe two or more springs and replace them with a length of hard rod, nice fit in the spring bores. In the bottom of the bores sink a short legth of a thick O-ring, a bit smaller o.d. than bore, maybe 1/4 " long. Do a test in a vice and compress the lot so you can see what length of o-ring you need to almost press the ESA to its stops. This would offer a softer sort-of- progressive stop and no more hard slam. Rubber gets steel hard when in a closed volume so some experiment with length and diameter of the rubber can help for feel. Don´t see any risk in trying on the bike, the rubber is in the bottom of the bore - unlike the broken coils of springs flying around in the primary.

Vic

Sunbeam worm drive:

p8_f5.jpg


BMW type ESA :

P1050216.JPG

Vincent ESA :

P1050185.JPG
 

vibrac

Well Known and Active Website User
VOC Member
Interesting to compare all that engineering complexity with a few pieces of special material on pegs in the electric start comet it doesn't take long to take the covers and sprag clutch off to inspect the drive so time will tell....
 

peter holmes

Well Known and Active Website User
VOC Member
Tim, apart from dispensing with the mechanical metal to metal contact of the standard ESA, how much movement does the new electric start ESA provide, it looks to be negligible to nil, I have no idea whether that is a bad thing or not, I have known people, very good engineers I might add, that have completely dispensed with the crankshaft ESA altogether and have the shock absorption elsewhere, especially when fitting a Norton/AMC gearbox.
 
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vibrac

Well Known and Active Website User
VOC Member
I can see Zero movement in the unit I cannot deform the peg material by hand
 

oexing

Well Known and Active Website User
VOC Member
Zero movement would not be a bad thing, if you just want protection for gearbox components. I´d think the Vincent gears are strong enough to not need any protection from an ESA taking into account that there are two chain drives on a Vincent - unlike all gears BMW or Guzzi transmissions. So some protection from harshness is there already. One thing I remember from the Alton ESA pictures is a non-existing bearing bush for the sprocket that one had to add on later or else I´d expect wear in there. But then in case you liked to reduce kangaroo drive mode at very low speeds by having an ESA with a lot more range the Alton will not provide this at all. So you are back at the questionable original - that I´d try to improve a bit with adding some rubber material in place of two or more springs in their holes. Somehow I like the idea now and hope somebody else will test this , can not do much wrong I guess.

Vic
 

Joe

Website User
Non-VOC Member
Now that would be another slap on that ESA, from me as you´d expect, once again: Could that knocking be from bashing the moving part of the ESA onto the end plate when all stroke of the ramps is used up - as is typical in this case and no amount of springs will prevent this ?

Vic
Hi Vic,
what You are suggesting seams something different from what I am trying to tackle - I am experience a little rattle only.
The behaviour you are explaining can be forced (and unintentionally happened to me) by quickly accelerated the bike from 2nd gear but rather then swithcing to 3rd engaging 1st gear instead. The ESA is doing it`s job by eliminating instant shock from rear tire to crankshaft.
What You hereby experience is like an inverted Automatic Breaking Systems (ABS). The rear tire oscillates at dry streets - I would say - at about 1/3 of the frequency you know from today`s cars. And Yes, You then clearly hear metallic sound of the ESA bashing to the end plate.
(Good, that the rear tire does not break out sidewise :). The oscillation frequency is mainly determined by the total ESA sping constant and difference in rear tire friction between tight grip and sliding grip)
 

Joe

Website User
Non-VOC Member
HI Guys,
I am surprised about the amount of feedback I am getting - thanks to everybody:)
To determine whether the little rattle comes from ESA I would need to spend half a grand to buy a new one which to me is not worth while the thing.
 

MartynG

Well Known and Active Website User
VOC Member
HI Guys,
I am surprised about the amount of feedback I am getting - thanks to everybody:)
To determine whether the little rattle comes from ESA I would need to spend half a grand to buy a new one which to me is not worth while the thing.
Fit a complete set of NEW ESA springs then go ride. If the noise is gone = solution.

If the noise remains then to rule our detonation/pinking set the ignitin full advance to 30 BTDC and go ride. If noise noise gone = solution (note with the standard ATD it may be a bit difficult to start with 30 full advance)
 

oexing

Well Known and Active Website User
VOC Member
Joe, did you check the fit of all splines , on ESA that sits on the crank end, and the spline on the gearbox input shaft that holds the clutch center ? You described some not very loud noise when driving . Is this periodically even with constant speed , maybe not so loud but there ? Any difference in sound when accelerating lightly or decelerating lightly ? We are hunting for syptoms to understand but myself not competent in this, projects still a long way to go and never had a single meter on a living Vincent on the road, not to speak of yards or miles for sure.

Vic
 

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