ET: Engine (Twin) Ditch the ESA ?

[stu spalding]

Hi Greg, I think you'll find that it was Paul Packman who fitted lengths of "O" ring material in the standard PD6 springs. I've often wondered what the results would be with a similar treatment of my set up. Maybe during the next tear down. Cheers, Stu.

 

[greg brillus]

Hey Stu, Sorry got me wires crossed.......anyway you have some good ideas.........I think I used some 4 mm "O" ring stock and cut them just slightly shorter that the new outer (larger) springs, and did this to all 22 springs. I actually set up the primary so i could run the engine with the primary cover off so I could see easily what was going on......It was immediately evident that this stiffened up the ESA a lot and this definitely helped the whole primary drive........I don't believe the shock absorber needs to have much deflection to save any damage, the Vincent design moves too much, not necessary I feel.

 

[highbury731]

When I heard about the use of O-ring stock instead of inner springs in the ESA, I understood that they should be the same length as the outer springs. Was I wrong, should I shorten them by say 1/16"?
Paul

 

[Monkeypants]

My understanding is that as long as there is some kind of shock absorber somewhere in the driveline, you are good to go.
A nice squishy cush hub is perfect.

Glen

 

[timetraveller]

Regarding Paul's question above. If it accepted that the original Vincent set up does not exert enough pressure and that the Australian one exerts too much then all we need to know is what the combined spring rate of the two original items is. Compressing bits of o ring nitrile rubber might be fine but what shore hardness etc. Can it be made reproducible? Properly specified springs could be and so, possibly, could carefully specified o ring string.

 

[Howard]

Update.
I bit the bullet and had the ESA welded up - I've wanted to do that for 40 years, after it came apart and robbed me of my best Cadwell finish.
Not road tested it yet (a few other bits and pieces to do) but the first thing of note, the starter turns the engine over a lot easier. My guess, compressing the ESA springs uses a lot of the starter's energy before turning the engine over. I think this is the problem that Greg mentioned above.
H

 

[greg brillus]

Good to know Howard.......On that Egli I had here I did make up an alloy disc to replace the springs so effectively locking up the ESA and the engine cranked over with no problems at all.........Because it had basically a Lightning type rear wheel that was all new, I had to keep some form of shock absorber in the system. I would have preferred to replace the rear wheel with something that had a cush drive within, but to expect the owner to proceed with that would be too much. the second option was to keep the ESA functional but to stiffen it's action up much more.........In a message sent to me the other day, the owner now reports that the bike is starting fine and generally running very well. I had to do some leaning off of the Mikuni carb's on it as well......it seemed to be running too rich and readily fowling it's 10 mm plugs, thus adding to the poor running and so on.

 

[Howard]

Quick 10 mile trip, seems ok. Advantage number 2 the multiplate clutch is much lighter. Again my guess, I always have to set it to the max load, which previously has been when using the starter, due, I now think, to the extra torque to overcome the ESA springs.

 

[highbury731]

Given that the Vincent ESA is way too soft, I think that more spring pressure is desirable. So I have a D spring assembly, and will use the O-ring string to the same length as the outer springs.
Paul

 

[oexing]

My thinking about this place is a bit different: Don´t take out ALL outer springs to be replaced with o-rings. I´d want to keep most of the range of the ESA lobes to use the steeper ramps on the lobes. That way you convert less of the motor torque into axial thrust on the small faces on the triplex sprocket and inner ring of the leftmost main bearing. This spot does wear a lot , steel on steel mating, lubrication is overloaded at this amount of thrust. That is why I would not suggest overly hard springs as a desperate way to prevent the ESA to slam to its hard limits due to wrong lobe shapes. You overload cam tops and inner race from this.
So yes, I´d put short lengths of o-ring strips in two or four spring holes but a suitable bit of hardened steel pin ON TOP of the o-ring in the bore. This will act as a "soft" stop before full hard lift of the ESA is reached. Steel pins on top because no o-ring can squeeze in the gap as it is way below in the hole. A 6mm o-ring bit in the 7 mm hole should provide some squeeze for a soft stop I´d think.
There are basically two arguments about ESAs : Do you want to protect gearbox teeth as a reason for any ESA in transmission? I´d think in a Vincent no need for this, gears are very strong compared to other 500 cc bikes. A Vincent twin is not a 1000 cc single, just two 500 cc singles flying in close formation. So why worry about this understressed gearbox and have a poor design ESA at all ? After all, there are two chains in a Vincent drive train so no real harsh conditions here even without any ESA - unlike all gears shaft drives like on BMWs or Guzzis .
Plus there is some kind of clutch, servo or multiplates, another shock limiting device that will protect gears from overloads to give peace of mind when having no ESA at all.
Or another argument about ESAs: You want to smoothen out a kangaroo ride at very low speeds ? Allright, so you´d be forced to keep a wide range ESA - try the two o-ring in hole soft stops as suggested. I´d be curious to get feedback from road tests.

Vic