ET: Engine (Twin) Ditch the ESA ?

Howard

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Has anyone run a twin with chain primary drive and no ESA? I have a rear hub cush drive (Egli) and think the ESA may be superfluous, not to mention my ESA seems to be creating a start off judder due to wear.
 

Chris Launders

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I've been considering this for some time, my Norvin hasn't got one at all (belt drive primary, Manx rear wheel). I keep meaning to buy another sprocket and weld it up just to test the idea on my "standard" twin. I have a 1979 HD sportster that hasn't got on at all either, they had an ESA earlier but dropped it for some reason, there isn't another anywhere, I'm still building it so can't comment on that though.
 

vibrac

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Here is the sprocket and shock absorber on the electric Comet (From the comprehensive instructions)
1596383076190.png
 

oexing

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Vincent, what do you mean "too much movement" with this Alton ESA ? I found this photo with pins working in poly bushes, so only minimal movement I´think, minimal "elastic shock absorption " then.
In a Vincent twin I´d block the old ESA for fear of slamming the end plate due to wrong shape of lobes and useless springs in that case.
But I suggested to leave out two or four springs and put lengths of 6 mm O-ring strips inside and suitable cuts of 6mm /1/4" rod on top. So the rubber strips can compress to a minimum via the 1/4 rod over them but prevent a hard bang onto the spring plate stop when you tried out a combination of o-ring plus steel rod by squeezing the assembly in a vice for checking it does not touch the end plate still. This would be an easy mod to try but so far nobody jumped at this for reports.

Vic
ALTON ESKC SA sprocket assembly 02.jpg
 

Howard

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Sounds like there's mild agreement that I don't need the ESA. If I decide to have it welded up, does anyone know what grade of steel it's made of?
Howard
 

timetraveller

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If you want to find out whether it is necessary or not then you do not have to go the whole way and weld it up. You could just put a solid disc of steel in the gap normally used to allow for spring compression and then make sure it is well bolted down. My own feeling is that there are some misunderstandings about the movement of the ESA under load. These were typified by Oexings advocacy of the superiority of the BMW design. I went to the trouble of showing a chart on here of the way in which the force exerted by linear rated springs would vary with the rotation of that design. I can't reproduce it from here but the result was that the mechanical design induced a non linear, rapidly increasing force as he components rotated against each other. The Vincent design does not do that. Instead the force exerted increases linearly with rotation. I also pointed out that when Dick Sherwin fitted one of the Australian produced ESAs to his Black Knight and sidecar he found, after a few thousand miles, that only the very bottom of the ESA cams had been used. Removing four of the springs cured that and allowed the cams to move further up their ramps. The problem, it seems to me, is not the mechanical design of the ESA cams but the strength of the springs used. There is absolutely no problem in getting springs made. Even I, with a completely non engineering background, have had four different strengths of spring made for the JE steering stem mod, for Series A seats and for a variety of different drum brake shoes. I believe that Stu Spalding has already had stronger springs made for the ESA and clutch shoe centralisation. If stronger springs are required then there should be no problem getting them made,
 

greg brillus

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While we're talking ESA's, one recent job was a 1330 Godet Egli that the customer bought new in 2015 and was literally terrified to start it. This was on account of the massive destructive crashing sounds as the engine fired up. I found that the stock ESA well one with 22 pairs of springs was going to full deflection from cranking to engine firing up........This was evident by the witness marks and ware shown on the cam surfaces. I spoke to Neal Videan about the stronger ESA he had come up with, but he was unable to supply any more as he had exhausted his stock of them, and they were slow moving (as in slow selling).........He did send me a sample so I could copy it, but I remembered what Stu had said about replacing the inner springs with lengths of "O" ring material. I decided to give this a go, and it seemed to work very well. I'm not sure the starter system likes the ESA set up at all........ I think a belt primary would be much better, and just run a cush drive in the rear hub...........Running a twin without some form of shock absorber in the drive train would be too destructive, and eventually something will fail.
 

stu spalding

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I believe that Stu Spalding has already had stronger springs made for the ESA and clutch shoe centralisation. If stronger springs are required then there should be no problem getting them made,
Thanks for that Norman, although I feel I should point out that while the clutch shoe plunger single springs are a direct replacement for the double springs, the ESA springs are different and require a fair bit of work and a new nut and spring plate. A write up on the mod can be found in MPH 820, May 2017 for those who are interested. Cheers, Stu.
 
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