ET: Engine (Twin) Ditch the ESA ?

[Texas John]

Vic et al, What are "O-ring strips" to which you refer and from whence do they come?
TT - If most of the complaints against the ESA could be fixed by stronger springs - can You or any of those you have communicated with make a recommendation for what to get? How about progressive strength springs? Would not the VOC have an interest in a relatively cheap part that would solve owner's complaints about the ESA? Hasn't VOC Spares had a few iterations of redesigned ESAs for sale?

 

[oexing]

Please look up my post in previous page, I hoped to be clear enough in my thinking. The o-ring material can be a fat o-ring with 6mm cross section that you cut for having maybe 1/2" length of o-ring to drop in two or four holes (ca. 7mm ) without springs at all therein. Sure you can get o-ring material in meters - or feet for those stuck in 19th century. But easier to get a fat o-ring to cut. My idea is NOT to aim for extra heavy springs, not much space for mods to increase loads by springs. The negative effect would be extreme loads on lobe tops and corresponding parts by heavy springs so you´d get even more wear on ESA lobes as lubrication by oil will not help. When trying to limit range of ESA by introducing extra heavy springs you will also get extreme side loads onto faces of triplex sprocket and the inner race of outer main bearing - plus extra wear at these places too - steel on steel. It is better to let the ESA climb higher on its lobes till it stops by springs or o-rings as most of the torque will stay within the ESA and not be transformed into heavy sideloads onto inner ball race - a force vector matter from ESA gradients on lobes.
So the main objective is to have a softer stop from rubber elements in the ESA before it hits onto the steel plate at crank end with a bang - and destructive shocks on chain and generator.
I would not like to replace all inner springs by o-ring strips as I´d see them squeeze between windings of outer springs and would not expect high mileages in these conditions. So when dropping 6mm rubber material in two or four holes I´d place short pins with 1/4" dia. on top of the rubbers so all rubber is way down and just long enough that by squeezing the lot in a vice for tests you will not hit the limits of the ESA. In effect this would be a soft stop with the rest of the ESA assembly standard and at most of its original range.
Basically NO ESA is essential on a Vincent I´d think, except for smoothing the ride at very low speeds. No need for gear protection as there are two chains on the bike, plus a clutch that limits any extreme loads by slipping - simple. The gearbox contents are very strong for two 500 singles (v-twin with wide spaced power cycles) .
The Spares Co. seems not to be overly interested in reworking the old ESA for a real suitable operation, just tweaking a bit to fight side effects like chipped edges. The BMW type , an effective concept since half a century without any problems, would be cheaper to machine. One side very simple on a CNC mill, the other side needs an electric dividing head for dialling the angular positions combined with paired positions in one axis. I did it on a manual mill so no witchcraft really.

Vic

 

[Chris Launders]

Would there also be an advantage in somehow incorporating a flange on the inner end of the ESA sleeve (like a BSA for instance) so the axial loads are kept in the ESA rather than being transmitted into the bearings ?

I have some old ESA parts that have been modified to take a single spring, I've never tried fitting this arrangement would you think it worth trying ?

 

[stu spalding]

I have some old ESA parts that have been modified to take a single spring, I've never tried fitting this arrangement would you think it worth trying

Tony Maughan adapted an ESA to take, Ibelieve, a BSA A10 single spring but I understand that this was not successful. Cheers, Stu.

 

[bmetcalf]

There has been talk of Belleville washer/springs over the years, but I don't know if anyone has tried them.

 

[timetraveller]

Texas John, I'll do my best to explain the situation regarding ESAs as I see it. There are people in this club who are competent engineers so they can then take apart what I write. The long standing fault with the original ESAs was their tendency to come undone and break the springs. A study of early MPHS will show some of the ways in which people tried to overcome the problems The series D ESA was a significant improvement and, if properly assembled, should not come undone. However, it has become clear with time that the force exerted by the original springs system is inadequate and that under any significant force the ESA goes from hard over one way to hard over the other. The Australian version with more springs was educational in that it did not move enough. This gives us a good reference system to work from, I.e. too weak to too strong. If we can measure the spring rate of each spring pair in the original systems then we can easily work out what strength springs are required to give us the required force.
You mention progressive springs. The mechanical design that Vic advocates would impart a progressive force from linear springs. I am not convinced that either solution is required, just some stronger springs.
Regarding the "redesign" of the ESA a few yeas ago; Ian can put us right on this but my understanding was that it was not so much a redesign but a correction to the drawings as there had been some design creep over the years and cam profiles had varied from the original.
When it comes to the use of "O ring string" to act as a resistive medium then I am suspicious. What shore hardness and what material would one advocate and who would ensure that the same material was used on each occasion? The way that I see it is that if we came up with the correct strength linear spring then they would be a trivial cost and it could be ensured that each batch met the specification. What would be the advantage of using o ring material of, possibly variable quality, rather than sticking to the original design, with D improvements, and just using springs.
I am away from home at the moment and cannot measure the spring rate of the original spring pair combination. When I can do that I can the find out from spring manufacturers whether a single standard spring could do the job or whether there is a problem meeting the spec with a single spring or whether something more complicated is needed.
This might all have been done before by Stu and I am sure he will let us know what happened.
The use of a single spring might work and I seem to remember back in the days of George Brown that he, or one of his competitors, used a square section spring but I have no way of knowing whether this was a term solution or not.

 

[greg brillus]

Interesting........You also need to remember that the ESA was designed to handle a certain amount of torque/shock load from a given engine specification...........Now we all know that these engines can vary a huge amount. So the basic 998 cc power unit gave about 45 HP at a certain rpm's........So what could possibly happen when we go to a 1330 cc High compression engine that supposedly puts out near 100 RWHP.........Oh and instead of a kick start it now uses a reduction starter off a Harley.........So how is the production ESA able to handle that.......Quite simply, it can't........That is why when you observe one in action with the primary cover off, you can see first hand the ESA goes to full travel either way from cranking to engine firing up. By stiffening up the action of the ESA this makes it function much better, although I feel it would be better with either a better design or removed (no crank shock absorber) and a cush drive used in the rear hub. On a soft engine combination you might get away with nothing as Vic suggests, but on a larger more tuned engine, it is a must, or else you will damage and break something........Those rear hub bolts and more so the ten 1/4 BSF bolts clamping the rear sprocket to the drum will probably fail.

 

[vibrac]

I know that square section wire springs were available for Manx Norton clutches as I had some on my Manx, In passing the Douglas Radrulic forks had square section springs and they were then ground on the OD to make a taper thus giving them a progressive rate. they are also widely used in die springs so some may be available off the shelf
they give more strength and larger flexibility range than round section.

 

[bmetcalf]

Matchy singles had a single square section ESA spring.

 

[oexing]

Remember with the standard ESA there is not much space for a lot harder springs, only ca. 7 mm holes for two springs. And lots of spring breakages all the times were reported anyway . They did their best to have maximum spring forces in that space, else you´d need a lot bigger parts for bigger and more powerful springs. Would not know any square section springs in that small dimension suitable for Vincents.
Also very hard springs will lead to extreme axial loads on inner bearing race and sprocket face and wear as noticed by other owners, up to misalignment of chain runs from this. This matter gets ignored each time when harder springs are discussed here to struggle on with old type ESA . That is why I would not go for hard springs to fight poor lobe shapes as you overload lobe cams from this. So I´d keep the standard springs and only provide a soft stop by o-rings in holes as suggested. Material hardness is not critical as only the soft stop is cared by rubbers , not affecting the whole range of movement in the ESA. This will not help the ESA going onto stops both directions lots of times but then not hard stops as in steel bashings like now.
So to be open, only a redesign for progressive lobe shapes would be a suitable way but for this we´d need a club vote to have this done .
I learned from axial faces wear in this forum so made up a special steel bush with maximum faces for the sprocket to bear on which also forms the lip for the outer roller main bearing at the inner side, made possible by having metric modern bearings with lots of choices. When you zoom in in the photo you see the sleeve on the crank end next to rollers and below the sprocket fitted on its place . Don´t know if there are ways to do mods on standard bearings like machining off any radius on inner race and fit a hardened spacer top hat type to get same conditions in the end. Not a brilliant detail in Vincents really, too small faces available for extreme axial loads.

Vic