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ET: Engine (Twin) Engine Shock Absorber


oexing

Well Known and Active Website User
VOC Member
Vibrac,
my remark about that Alton ESA being useless was meant to point to the photo showing some sprocket holes filled by poly bushes up to the top . You cannot compress rubber, only deform it . So for getting several degrees of rotation within the sprocket assembly there must be about a third of the volume in the holes free of rubber for it for deformation into this space. Either do a few cutouts in the polybushes or replace with o-rings. So when holes filled to the top with poly material the lot does nothing in smoothing the drive - so in this aspect it is useless like in being solid. But then it does not produce shock loads going into the chain like the original Vincent ESA does when that hits the end plate due to the hopelessly shallow lobe design with which the springs cannot possibly cope. I really believe it is better for the primary chain drive to have NO ESA at all than instead exposing it to the harsh shocks the Vincent ESA does to the chain.
It is a waiste of time trying to discuss pros or contras of the progressive action BMW lobe design as opposed to the flat Vincent shapes that lacks the progressive feature and in consequence hits its hard limit at the end plate. I cannot see a need for a linear action in an ESA but definitely for a more progressive design that does not rely on springs to fight a bang to the stops. I´d be interested to see that Australian design ESA which is said having been too firm at first try with all springs fitted. Remember, all these springs fighting to prevent the bashing at the end plate in the Vincent ESA put their total load onto the inner race of the main ball bearing via the triplex sprocket. Increasing spring preloads is simply the wrong way to achieve an effective ESA , the BMW type does it with the steeper lobes so forces stay in the ESA mainly and don´t wear the inner ring and sprocket face so badly.
Since the production days of Vincent post war bikes there is widely known experience about both types of ESAs: Millions of BMWs from fifties up to present types I think - no defects ever here in the gearbox ESA, most owners don´t even know about them, never had to deal with such. BMWs are all gear bikes, no drive chains to speak of, so no damping effect from said chains. So you bet these need an effective ESA for sure !!
Then at Vincents, a few thousand bikes produced - and many hundreds of snapped triplex chains, smashed cases and wrecked dynamos . . . . .

Vic

BMW type lobes:

P1070571.JPG

BMW R 100 gearbox input shaft:

s-l1600 ll.jpg

Kawasaki 1300 gearbox output shaft right side:

001.jpg
 

Pushrod Twin

Well Known and Active Website User
VOC Member
And just for comparison, here is a dirty old Moto Guzzi one. Remarkably similar in ramp shape, I think, to a Vincent one. Been used by MG from the first 750cc Sport 5 speeds in 1972 until the demise of the 5 speeds in 1100 cc California models recently. The only change I am aware of came with the 1000cc Lemans when the coil spring was replaced with Belville washers.

What does make a noticeable difference in driveline shocks is a rubber cush in the rear wheel. It is easy to get a direct comparison with an old Guzzi. My Sport started out life with the solid, fixed spline, rear wheel. I fitted an 850T wheel with the rubber cush. Noticeable difference in gear changes, smoother & quieter. One would expect a bit more life out of universal joints too, but I havent been in for a look yet.

I would be reluctant to remove the D style ESA off my Vin if I fitted an electric starter. I feel it should take some of the shock out of the starter system. Electric motors, with no VSD or soft start, go from zero to full torque instantly, if that doesnt create a shock on the mains bearings I would be surprised.
 

Attachments

Bill Cannon

Well Known and Active Website User
VOC Member
Vibrac,
my remark about that Alton ESA being useless was meant to point to the photo showing some sprocket holes filled by poly bushes up to the top . You cannot compress rubber, only deform it . So for getting several degrees of rotation within the sprocket assembly there must be about a third of the volume in the holes free of rubber for it for deformation into this space. Either do a few cutouts in the polybushes or replace with o-rings. So when holes filled to the top with poly material the lot does nothing in smoothing the drive - so in this aspect it is useless like in being solid. But then it does not produce shock loads going into the chain like the original Vincent ESA does when that hits the end plate due to the hopelessly shallow lobe design with which the springs cannot possibly cope. I really believe it is better for the primary chain drive to have NO ESA at all than instead exposing it to the harsh shocks the Vincent ESA does to the chain.
It is a waiste of time trying to discuss pros or contras of the progressive action BMW lobe design as opposed to the flat Vincent shapes that lacks the progressive feature and in consequence hits its hard limit at the end plate. I cannot see a need for a linear action in an ESA but definitely for a more progressive design that does not rely on springs to fight a bang to the stops. I´d be interested to see that Australian design ESA which is said having been too firm at first try with all springs fitted. Remember, all these springs fighting to prevent the bashing at the end plate in the Vincent ESA put their total load onto the inner race of the main ball bearing via the triplex sprocket. Increasing spring preloads is simply the wrong way to achieve an effective ESA , the BMW type does it with the steeper lobes so forces stay in the ESA mainly and don´t wear the inner ring and sprocket face so badly.
Since the production days of Vincent post war bikes there is widely known experience about both types of ESAs: Millions of BMWs from fifties up to present types I think - no defects ever here in the gearbox ESA, most owners don´t even know about them, never had to deal with such. BMWs are all gear bikes, no drive chains to speak of, so no damping effect from said chains. So you bet these need an effective ESA for sure !!
Then at Vincents, a few thousand bikes produced - and many hundreds of snapped triplex chains, smashed cases and wrecked dynamos . . . . .

Vic

BMW type lobes:

View attachment 32457

BMW R 100 gearbox input shaft:

View attachment 32458

Kawasaki 1300 gearbox output shaft right side:

View attachment 32459
Sorry, off topic, but I've changed so many of those R100 input shafts over the years and I see that one has worn its clutch splines just like all the ones I changed!
Cheers Bill
 

stu spalding

Well Known and Active Website User
VOC Member
Hi Vic, I've done over a quarter of a million miles on my "D" ESA and the only problems I've had have been with breakage of the inner spring PD27. This has been cured with a different spring plate and single springs. (see MPH 820, p 25). Cheers, Stu.
 

greg brillus

Well Known and Active Website User
VOC Member
One common fault is a mismatch of parts whereby the outer spring plate does not exert enough crush on the springs, this causes excessive movement of the cam and the springs deteriorate quickly.
 

Vincent Brake

Well Known and Active Website User
VOC Member
Well sorry to say but theres another problem to take into account specially when you ride the alton esa a bit of mls.

As the damping only needs short ways to travell and not th long ones as on a twin ( indeed a disaster for the peak loads on the chain) thats very good
But;

All looks soft material.
Apart from chain wear.
There is these little f#@cking movments causing the internal pivot to wear rapidly indeed.
I guess only a harndent chainwheel with an tight fit bronze bush on the counterpart.
Will make it
Repairable.
And longer life span.

Or did i miss it in the reading...

Succes with all the one pots.

Cheers

Vincent
 

Glenliman

Well Known and Active Website User
VOC Member
BMW is one of the least reliable motorcycles produced today according to a huge Consumer survey of motorcycle brands , done a few years ago. Harley beat them quite badly.
Only Ducati fared slightly worse than BMW. Electronic failures were their biggest problem area but there are plenty of driveline failures as well.
Yamaha came out on top with the other Japanese brands close behind. If we are going to change out our esa, maybe one of these big Japanese MC manufacturers would be worth copying. Pretty sure they all use a big soft rear wheel cush drive. So maybe weld up the esa and start looking at the rear wheel.
Or just leave as is. Its not been a big problem area for me nor have I heard of others experiencing massive primary chain failures etc. It's good to put a new Primary chain on once in a long while.
The Vincent is a smooth bike to operate. The modern BMWs I've ridden were not.

Glen
 
Last edited:

oexing

Well Known and Active Website User
VOC Member
Bill,
the clutch spline in "modern" BMWs is crap design since 1969, everybody knows that. But this has nothing to do with the ESA, and I guess you never had to change the ESA parts and reused them on the new shafts. Lubrication of the clutch splines is critical, I take MoS2 powder plus sticky chain lube there. You don´t want this to contaminate the friction material in the dry clutch. Nevertheless the BMW ESA is very effective, no rubber cushions or chains anywhere on these bikes for extra damping - and no gear tooth breakage so what else does one need to confirm the effectiveness ???
This Guzzi ESA in the photo above is another example of the designer being not quite up to scratch and only copied the poor prewar design. I heard from a friend about this when I discussed the troubles in Vincents ESAs and he told me the Guzzis get gearbox disasters from chips that break off the edges of the lobes with not matching shapes - exactly like with the original Vincent design, no secret here , everybody will know. When you look at the Guzzi photo you can see the wear marks along the edges with consequences. The present Vincent replacement design only fights this mismatch of faces but does not turn the ESA really effective. I am puzzled that it seems so hard for many to see the need for a progressive shape in ESAs to produce a real damping action. It is a bad idea to hope for springs achieving this target when the shape of lobes is poor . Really the steep gradients of the lobes should do this task . I cannot provide sketches or drawings of my BMW inspired modification. It is NOT a job for a CAD based program but instead only for an encoder based dividing head hooked onto a CNC mill and this set has to dial in about 50 positions per lobe with one mill axis only used plus its corresponding rotation on the dividing head. I made 6mm radii on one male half of the ESA so logically the matching other half was machined with a standrad 12 mm carbide end mill for 60 HRC material. I did this all manually with DRO and encoder position, would be a smooth quick operation when a such equipped CNC mill would do this. But I am not interested in production - nor is the Spares Co obviously. So possibly Conways could be an address for this.
I have no idea how the traditional Vincent lobes are produced but can prove with my first aluminium test pieces that my thinking was spot on by looking at the bearing blue marks. Guzzi still struggles with their poorly matching shapes , don´t know about the "new" Vincent ESA.
As I see it, there are two aspects with ESAs: Do you just want to protect gear teeth from breakages or pittings by hard shocks - or do you want to cushion the power pulses between strokes when going very slow in high gear ??? In first case a little bit of rubber in an ESA would do - or no ESA at all in a chain drive bikes. Chains like tooth belts should do OK without ESA. When wanting to smooth out power pulses and kangaroo drive character you´d need a wider range ESA but with progressive lobes to be effective. So yes, two requirements you could choose from and for racing I´d choose NO ESA at all, no troubles with Vincents I guess.
Modern BMWs unreliable, not my topic and too unspecified, and possibly written by an USA magazine, I ´don´t care. But regarding ESAs , the Vincent design is in no way recommended in comparison to the BMW type - and this is based on millions of bikes produced. See my photo above of the Kawa 1300 ESA in the output shaft or elsewhere , I guess in other industries used as well.

Vic
P1050180.JPG

pre-1969 BMW gear shafts, twin on top, 250 below, coarse clutch splines !!
P1050205.JPG

modified Vincent ESA:
P1050213.JPG
 

Cyborg

Well Known and Active Website User
VOC Member
Vic, When I read your previous posts on this subject, it didn't quite register in my head. I now understand what you are talking about so you have at least one convert. It's the "bang" at the end of its travel which makes it worse than no ESA. Not sure why spring pressure on the inner ball bearing really matters. It all transfers through to the flywheel, so as long as the mainshaft stays put... then no issue?

I will now give myself an extended time out for participating in yet another highjack.
 

greg brillus

Well Known and Active Website User
VOC Member
The shock absorber is not only responsible to absorb power shock loads from the engine but reverse loads from the rear wheel forwards, like from a sudden stoppage like a crash or some other uncontrolled lock up. It absorbs torsional loads, just like the row of springs in a clutch plate center from a manual car. The issue with broken chains and so on is either poor maintenance, poorly fitting parts (wrong collection of parts assembly) and lastly the fact that over the years the availability of good quality chain has declined, remember what happened to the "Goodwood racer" of the Horner brothers......they could not find any decent chain, and were lucky it didn't smash out the front of their engine.........most users of these bikes should not concern themselves, it seems all too easy to "Overthink" these things.
 

Pushrod Twin

Well Known and Active Website User
VOC Member
I have just read the other post, directed to by the link. Like Cyborg, I am now understanding better the reason for Vic's insistence that the Vincent ESA is not progressive whereas the BMW one is. The steep sides of the female curve (for want of a better expression!) on the BMW style do not appear instinctively to be progressive, but when looking harder & adding that to Timetraveller's diagram, I now see it.
The Vincent one, visually, appears instinctively progressive, but is not, it the pressure exerted along the shaft would remain constant, it relies on springs progressively compressing to make the movement progressive.
I join Cyborg as convert number 2 and will go and stand in the corner. :(
 

Chris Launders

Well Known and Active Website User
VOC Member
I can certainly see what Oexing is saying about the ESA and I have to agree, but surely the shock loads are not generated by the engine, the flywheels should damp them out, and as regards breaking the triplex primary chains, that seems a ridiculous thing to happen in any sort of normal usage.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
regards breaking the triplex primary chains, that seems a ridiculous thing to happen in any sort of normal usage.
It is common knowedge that the spate of breaking tripplex chains mainly occured in the 1970's & 80's when the quality of primary chain went through the floor with Reynolds stopping the manufacture of motorcycle grade tripplex chain and quitely replacing it with industrial chain, usually with cheap split rollers. Why is it you never hear of Comets breaking primary chains which use the same ESA but a single row chain? Could it be because the single chain was still available as motorcycle grade?
The biggest problem with the Vincent ESA is it rubs against the outer main ball bearing during movement and slowly wears away and so moves the engine sprocket inboard over time. This then puts side load on the primary chain due to sprocket misalignment which is not good and Vic's BMW design will suffer exactly the same problem. I have seen twin engine sprockets which have worn right through the hard surface of this contact area and caused the sprockets to be out of align by over 1/8" which is not good on a tripplex chain which is inherently stiffer against sidewards forces than a single row chain. That and low quality chain is most probably why they broke.
 

Albervin

Well Known and Active Website User
VOC Member
I have come in late and only scanned most of the comments. However I did see a very graphic demonstration of the "old" type ESAs sold by the VOCS against the "new" type. The old ones were plainly riding up to a very thin shoulder due to poor machining practise. The manufacturer refused to change their design. It was only with Ian Savage's insistence that the new and more accurate ESA made it to the manufacture stage. Now the two parts of the ESA run perfectly in sequence and optimise the loads. One thing that did annoy me though was that when these new ESAs were manufactured the old ones were not consigned to the bin immediately. When you do your next major maintenance look closely at the way the ESA works, each cam should maintain full contact and not "ride up"; if it does then bin it and buy a new one.
A question. If you use an electric starter in the approved way, how does that differ from a roller or a run and bump or downhill clutch start? When I do a downhill start I am in two minds whether to use clutch or valve lifter. Again I absolve myself from cries of incompetence because I am a chemist and not an engineer.
 

Cyborg

Well Known and Active Website User
VOC Member
The shock absorber is not only responsible to absorb power shock loads from the engine but reverse loads from the rear wheel forwards, like from a sudden stoppage like a crash or some other uncontrolled lock up. It absorbs torsional loads, just like the row of springs in a clutch plate center from a manual car. The issue with broken chains and so on is either poor maintenance, poorly fitting parts (wrong collection of parts assembly) and lastly the fact that over the years the availability of good quality chain has declined, remember what happened to the "Goodwood racer" of the Horner brothers......they could not find any decent chain, and were lucky it didn't smash out the front of their engine.........most users of these bikes should not concern themselves, it seems all too easy to "Overthink" these things.
Overthink is my middle name. Its a curse usually followed by a case of vapour lock. Don't disagree with anything you wrote there, but..... didn't I read some where that one of your fellow countrymen studied the ESA's movement with a strobe. He found that it was basically an on/off switch. So assuming I did actually read that somewhere and the ESA in question wasn't knackered, thats what makes me want to agree with Vic. Agreed that dampening is a good thing, its just that if the ESA isn't doing a good job of the "A" part and maybe at best it's delaying the inevitable shock by a nanosecond, then it isn't much of an improvement over just having a bunch of backlash in there. I honestly don't know, but I have an ESA installation coming up so find the subject interesting.
 

Bill Thomas

Well Known and Active Website User
VOC Member
There is a lot of people who have put a lot of miles on the old ESA,
We now know not to use the washer that locates the spring ends the way it was intended, Some just turn it around, But there is a better washer we can buy now.
I think in over 50 years, 17 years Racing I had the nut come loose once, And had a few broken springs.
Not so bad ?.
 

erik

Well Known and Active Website User
VOC Member
I would like to say that I have some experience with BMW gearboxes 5 speed from the seventies. I had never a problem with the esa ,but the rest of the gearbox was not very good engineerd.After less than 50000 miles the layshaft was for the bin and three idlers from the mainshaft ,too.Pitting on the pinions was although a problem.Changing gears was all the time very poor in relation to other motorcycles.BMW is not the benchmark to my mind.Regards Erik
 

Pushrod Twin

Well Known and Active Website User
VOC Member
I would like to say that I have some experience with BMW gearboxes 5 speed from the seventies. I had never a problem with the esa ,but the rest of the gearbox was not very good engineerd.After less than 50000 miles the layshaft was for the bin and three idlers from the mainshaft ,too.Pitting on the pinions was although a problem.Changing gears was all the time very poor in relation to other motorcycles.BMW is not the benchmark to my mind.Regards Erik
True. I had an example of the reputedly "indestructible" 4 speed /5 box in my R90S powered Earles Fork side car rig. I guess it was the combination of R90S horse power & side car work that broke the gears!
The cush drive went back into service!

Another point which has occurred to me is that the rounded tips of the Vincent ESA do appear to lend themselves to binding together, like two tapered wedges driven together. The BMW type cannot do that.
 

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