ET: Engine (Twin) ESA Upgrade
- Thread starter Bart
- Start date
Looking good Vincent and Bart. What is the purpose of the discs with the slotted holes round their edges?
I assumed the discs were the replacement for the standard springs.
Possibly, but they look to be made of steel, not something compressible and why the holes? I imagine that they are to go round the springs. Intriguing isn't it?
The discs are definitely dished and most diaphragm springs have "fingers" so I believe that's what they are, given the ID they look to go on the flange just outboard of the cam not on the end as standard.
Thanks for that Chris. I had not noticed the dishing. I wonder how many stress reversals they will stand? Vincent is a clever lad so I expect he has done his homework.
My thoughts on it are car clutches have them which will make them more flexible and possibly longer lasting than solid ones, solid bellville washers are possibly too stiff to give the springing/travel he's looking for.
Looking at the ESA body itself it looks as though he might want up to about half an inch of in and out movement so my guess is that is why there are two pairs of washers to give the range of movement. I am also guessing that the reason for the circular cut outs at the inner end of each slot is for there to be a pin in each ex-spring hole to stop rotation of the washers. Would probably also act as a stress reliever. My guess is that they have been using a modern finite element analysis program. Let us hope it works as well as it looks. I expect they will let us know eventually.
More like 1/4 inch movement, the total height of lobes is just about half an inch. And you can only go to a bit over half of that with two identical cams both sides as they would reach the top radius and lock there at max. lift - as I was told here from someone having his very worn old ESA lock at the top. The wear was in lobes plus on the side face of the sprocket wearing away itself and the inner race of the main bearing by all that load from springs and the effect of engine torque riding up the 30 degrees of slope on the non-working ESA cams. Most of the force goes into side load on inner race and sprocket, just think about force vectors at 30 degrees, simply and plainly wrong logics in old design.
The modified Belleville washers in Vincent´s photos still look pretty strong for the purpose, no need for rotational positioning by holes here. It is only the sprocket that twists on its steel bush, the outmost half of the ESA just lifts and compresses the springs.
As mentioned above, I am not quite so positive about that type of springs in high cycle applications, suspecting early fatigue failure but I really don´t know . So time will tell and a chance for us to learn.
Considering all bad effects told by Greg about electric starts on Vincents with old ESA I´d propose to Vincent a fresh business case as he stopped production of his brake sets: With more electric start systems in the wanted list he could take over new design ESAs suitable for those interested in electro and keeping chain drive plus ESA. Greg should do a video clip when hitting the start and filming the bang-bang of ESA , in consequence likely to break some gears in the starter drive. When on the road on any Vincent the ESA does exactly the same bang-bang with every twist grip action so a new ESA is overdue and more so with electric start. But for a batch of new ESAs the Hollandse type would not be my choice. The CAD performance by Bart is fascinating to finally arrive at a good mating of faces. But in cruel reality the BMW inspired logics are a lot cheaper to machine on any CNC lathe with milling attachment, just a standard 12 mm end mill and in two, three minutes perfectly finished. There is nothing to be gained by having same shapes for both halves of the ESA, even less desirable - and awkward to machine with ball nose mills in small steps.
The Spares Co is uninterested in real working ESAs so far, so Conways or Vincent S. would be a good contact for that job I´d think.
As the male side of the BMW type is same for all types you only have to modify the female half of the ESA for Comet, 1000 cc twin or even 1300 cc for individual progressive damping. I have decided on a 32 mm radius on the circumference of the sprocket half by gut feeling. For a Comet maybe a 35 or 40 mm radius would be allright, making for less of a gradient , for a 1300 cc type maybe 25 mm better, more aggressive damping with steeper slope then. No rocket science to work out, I did it with a pocket calculator and a little help from a DRO using positions from circle pitch mode - simple and worked perfect from first test set in alu by manual milling. The last photo shows BMW ESAs left shaft for 250 cc singles with larger radius, the gear on the right is from twins, smaller radius - simple.
Vic
some Japanese shaft drive ESA I think:
The modified Belleville washers in Vincent´s photos still look pretty strong for the purpose, no need for rotational positioning by holes here. It is only the sprocket that twists on its steel bush, the outmost half of the ESA just lifts and compresses the springs.
As mentioned above, I am not quite so positive about that type of springs in high cycle applications, suspecting early fatigue failure but I really don´t know . So time will tell and a chance for us to learn.
Considering all bad effects told by Greg about electric starts on Vincents with old ESA I´d propose to Vincent a fresh business case as he stopped production of his brake sets: With more electric start systems in the wanted list he could take over new design ESAs suitable for those interested in electro and keeping chain drive plus ESA. Greg should do a video clip when hitting the start and filming the bang-bang of ESA , in consequence likely to break some gears in the starter drive. When on the road on any Vincent the ESA does exactly the same bang-bang with every twist grip action so a new ESA is overdue and more so with electric start. But for a batch of new ESAs the Hollandse type would not be my choice. The CAD performance by Bart is fascinating to finally arrive at a good mating of faces. But in cruel reality the BMW inspired logics are a lot cheaper to machine on any CNC lathe with milling attachment, just a standard 12 mm end mill and in two, three minutes perfectly finished. There is nothing to be gained by having same shapes for both halves of the ESA, even less desirable - and awkward to machine with ball nose mills in small steps.
The Spares Co is uninterested in real working ESAs so far, so Conways or Vincent S. would be a good contact for that job I´d think.
As the male side of the BMW type is same for all types you only have to modify the female half of the ESA for Comet, 1000 cc twin or even 1300 cc for individual progressive damping. I have decided on a 32 mm radius on the circumference of the sprocket half by gut feeling. For a Comet maybe a 35 or 40 mm radius would be allright, making for less of a gradient , for a 1300 cc type maybe 25 mm better, more aggressive damping with steeper slope then. No rocket science to work out, I did it with a pocket calculator and a little help from a DRO using positions from circle pitch mode - simple and worked perfect from first test set in alu by manual milling. The last photo shows BMW ESAs left shaft for 250 cc singles with larger radius, the gear on the right is from twins, smaller radius - simple.
Vic
some Japanese shaft drive ESA I think:
Yes the slots are there as the bellville washers are to strong at first, i than machined them thinner.
(I like ladies the same)
Didn't work that well, they started buckle over.
Like a norton cluch spring can.
Mmm nortn spring....
Heee lets do some like that.
Worked a charm.
Travell is about 5-6 mill yes.
Its going in my Gdet, and stroker rapide. Will do the long read later.
(I like ladies the same)
Didn't work that well, they started buckle over.
Like a norton cluch spring can.
Mmm nortn spring....
Heee lets do some like that.
Worked a charm.
Travell is about 5-6 mill yes.
Its going in my Gdet, and stroker rapide. Will do the long read later.