Running without ESA

[Howard]

Does anyone run a twin engine with chain primary and no ESA. I've got a Laverda cush drive rear hub as well, but I can't decide if they're both necessary. I don't want to change the hub.
I'm about to do a Winter strip and tidy (leaks, paint etc) and one of the things I want to check while it's apart is the ESA, it seems to work at odd times (that's what it feels like) and it seems to be harsh.
Any comments and suggestions welcome.

Howard

 

[vibrac]

Its worth noting that the entire ESA has been re-designed by the VOC drawings project and is now available

 

[timetraveller]

You are probably aware of this Howard, but for others it should be noted that there is now a new design of ESA which is supposed to have better characteristics. I haven't seen one yet but clearly some of our brightest and best have thought about this so it should be better than the original which is not a very good shock absorber. John Emmanuel did tests on the standard item years ago with a stroboscope and found that it is more like a switch. It goes fully one way under acceleration and then fully the other way on the over run. The 'D' item is better than the 'B' and 'C' and when the Australian one is used with fewer springs than it can take then that is even better. If it is used with all the possible springs then it hardly moves even when a sidecar is fitted.

 

[bmetcalf]

Its worth noting that the entire ESA has been re-designed by the VOC drawings project and is now available

I don't see an assembly shown on the SparesCo site. Maybe too new to be shown.

 

[Howard]

Thanks, I didn't know there was a new version, but from TTs comments, I'm leaning towards locking it up and relying on the cush drive hub ......... it's just a bit of a leap of faith if no one's done it.

 

[hrdsuper90]

My gut reaction is not to do it, one function must be to ease the load on the gears. When I built my race sidecar I built a ESA into the primary belt drive to avoid broken Norton boxes I'd seen, did a lot of races and the box survived with regular servicing. However I concede that a primary chain (unlike a belt) would have some 'give'. Riding my 'A' Comet it is noticeably different from a post war bike, slightly harsher on acceleration which I always put down to the lack of an ESA, however overall I love the pre-war bike ! Hope that helps Howard.

 

[davidd]

My gut reaction is not to do it, one function must be to ease the load on the gears. When I built my race sidecar I built a ESA into the primary belt drive to avoid broken Norton boxes I'd seen, did a lot of races and the box survived with regular servicing. However I concede that a primary chain (unlike a belt) would have some 'give'. Riding my 'A' Comet it is noticeably different from a post war bike, slightly harsher on acceleration which I always put down to the lack of an ESA, however overall I love the pre-war bike ! Hope that helps Howard.

Howard,

I tend to favor the ESA. I have read many stories of Norton boxes suffering damage without an ESA. I think you could get away with a lot due to the strength of the Vincent box, but in the end, I think they are a help. I think a cush drive in the clutch might be a more reliable solution.

From what I understand the pulses from a running four stroke are incredibly harsh and hard on all the drive components including the rear tire. This is easy to understand with a big single banging away every other rotation with the attendant speeding up and slowing down with each explosion. A twin is not much better as the 50 degree firing can be seen as one much longer bang. The fly wheel is the primary ESA as it is absorbing pulses with its momentum. The gear box is protected by the ESA or the clutch cush drive and the rear tire adhesion is smoothed considerably by the rear wheel cush drive. I tend to see it as a one way system in that the benefits do not readily run back upstream.

David

 

[Chris Launders]

My Norvin with belt primary (Commando clutch), Norton box and Manx rear wheel is very harsh, I wish I could fit an ESA but I've a crank mounted alternator, I'm thinking of replacing the back wheel with something different.
Conversely my Brough has two cush drives, one in the clutch (Norton) and one in the back wheel (Enfield) and is as smooth as can be.
I've also fitted a belt drive to my Atlas and I'm going to replace the rear wheel with a Commando one with the cush in it.
Stick with the ESA if you can manage it, AND fit the Laverda wheel.

 

[Howard]

Thanks for those gems, real food for thought.
I'll reserve judgement until I strip the ESA and see what state it's in. Thinking about it, I don't think it's been apart since the 80s (doesn't time fly) so wear and tear is probably a factor in ts current operation. It came unscrewed at Cadwell when I was running second to Roy Robertson (my almost one claim to fame on a track) and I've hated the thing ever since, it was refitted with two locking wires, Loctite and probably three dot punches and a dab of weld (joke).
It's a strange component when you start to think what it does. Does it protect the transmission from the engine? If so it needs to be at the crank, or does it protect the transmission from road shocks? In which case it needs to be at the wheel. Is the cush clutch a compromise or a better mounting position? Do we need all three? A coffee beckons..................................

 

[greg brillus]

It's there to absorb torsional loads throughout the whole system. It's worst case scenario would be a complete lock up, though I doubt any shock absorber in the system can cope with that. But it primarily takes the power pulses from the engine as David pointed out, which is exactly why it works best on the end of the crank shaft. The other positions are better than none, but because they operate further along the drive train, their effect at the crank becomes less. The so called "Give" in a primary chain, or a belt means nothing in the scheme of it all. I run no shock absorber on the racer at all, and I found cracks in the spokes of the billet rear sprocket carrier I had on there......We made up another keeping the webbing a solid disc to stop cracks, and it seems to be ok so far. A crank shaft shock absorber would definitely be of help, even if it saves the crank over time. I would be looking seriously at the improved version the VOCS co have available. Just my thoughts..........Cheers..........Greg.