ET: Engine (Twin) Engine Shock Absorber

[van Ginneke]

Alton ESA in 3 parts

 

[bmetcalf]

So Alton's next job is to build a triplex version of their ESA!

Peter B

I wonder if Oexing’s BMW style design is cheaper to make?

 

[Bill Thomas]

I would think the belt drive does the same thing, Just takes the metal to metal shock out of it.

 

[timetraveller]

I have some doubts about Oexing's theory. When he first came up with the details of the design I bothered to work out the path length that the moving/compressing part would go through at different angles and I put that on here. It is certainly true that there is a rapidly rising rate of movement, i.e. compression versus angular movement, with the profiles he mentions. However, I need to remind the reader of some other information also on this subject and previously mentioned on here by me. The first of these items is that when John Emmanuel used a stroboscope to view the ESA he noted that it was like a switch in that it went from the base to the top and limit of its movement when load was applied. The second item to be noted is that after Dick Sherwin fitted one of the Australian ESAs to his Knight and sidecar and then had a look at it a few thousand miles later he found that the wear marks on the surfaces indicated that only about quarter of an inch movement was taking place, despite the fact that there was the extra loading of the sidecar. That is the extra number of springs. i.e. more force, was limiting movement to only about 20% of the total that is possible. Removing a few of those springs allowed more movement and, presumably, more shock absorbing. It seem to me therefor that there is more to this than just the profile of the cams. The Oexing/BMW profile gives rise to a rise in force which is more rapid than linear rate spring can impart. The original Vincent and the Australian system give a more linear rise in force exerted with the original one not being able to exert enough force and the Australian one exerting too much. The Series 'D' ESA has more springs, and was therefore capable of exerting more force, but whether it exerts enough would have to be checked by looking at the wear marks on the cam surfaces.
Over to you chaps.

 

[oexing]

Just commenting this Alton ESA design: As it is now it is quite useless. Why? These poly bushes fill the space in their holes almost 100 percent. This is very crucial: For any damping effect the rubber elements need SOME space around them to squeeze at all. When there is no space around the rubber it is hard like steel because no air in the rubber and not compressible. You could bin the poly bushes and use o-rings instead - or just keep the Alton type. You don´t really need any ESA in a Comet or in a twin once you scrap the Vincent ESA for good. The chains do the job without the ESA well enough and no shocks FROM the old ESA so no troubles .

Vic

 

[vibrac]

Just commenting this Alton ESA design: As it is now it is quite useless.......
You don´t really need any ESA in a Comet or in a twin once you scrap the Vincent ESA for good. The chains do the job without the ESA well enough and no shocks FROM the old ESA so no troubles .
Vic

Not sure what you are saying: Its useless because its not needed? or its just useless?
I did have a moment when I saw it but its a material solution that was not available in 1948 so we shall see how she runs this season, One thing is certain every scrap of space is used on that mainshaft with the SA and the Sprag sprocket and the necessary spacers it would be a clever guy who fitted in a better one in the space.
Its been under development for ages, post #20 (July last year) said that a year before (2018) they had not got one so its been at least 18 months in gestation so its had some testing, lets see how it goes

 

[Monkeypants]

There is likely as much cush in a chain as in a steel and poly belt. The belt is really continuos steel cables encased in rubber or similar. The steel cables don't offer much cush.
I setup a Newby belt in the vice. With small steel measuring blocks clamped
to the belt I measure 9.546" between the blocks with a small amount of tension applied, just enough to pull the belt straight.
I then leaned into a tension bar with all my weight and all the leg strength I could muster. The bar tensioner had a mechanical advantage of about 4 to 1.
We could calculate the tension in the belt, but it's not really necessary.
It's many times what a Vincent engine can create.
The measurement blocks were still the same distance apart- well almost at 9.548". This is with a digital caliper so the 2 thou is +- anyway.
Jim Comstock told me there wasn't any give in the belts, but I thought it would be fun to try stretching one anyway.
He also mentioned that he ran his Norton about 100,000 miles without a cush.
I still think a cush somewhere in the system is a good thing to have.
The likes of Suzuki, Honda, Yamaha and Kawasaki agree.

Glen

 

[Bill Thomas]

I have changed many Cam belts on Cars, Same sort of thing, But with a belt you don't have the "ring of metal",
I would not use one on a Bike, Seen too many fail on Car cams, Hate the things.
I think Vibrac changes his every year ?.

 

[timetraveller]

Bill, there are belts and then there are BELTS. Some of the stuff I have seen will take hundreds of horse power. Different animals to cam belts all together.

 

[Monkeypants]

Those Newby Racing belts have been well and truly tested by now, as have his clutches.
I think they're excellent. Very light in weight and simple.

Glen