Flywheel alignment

[Cyborg]

Tony Maughan told me that the centres were not to be relied on and that rollers were the best bet. Cheers, Stu.

Terry Prince told me the same thing about his cranks. And I quote “The crank cannot be checked between centres on a lathe, only on knife edges close to the inner bearings as the grinding process does not use the centres and they could be out.”

However, there is a local guru here that I would trust to measure one between centres. As I understand it, he confirms the centres are actually centres and redoes them if they are not.

 

[Bill Thomas]

I have V blocks with bearings I could use, Also I welded up a bracket with small bearings to check the balance,
So could use that, I just like playing.

 

[Robert Watson]

And he taught me to check them, first thing is to confirm the centres are, and if not, out comes the dremel to make them deadly. Then they are checked between two dead centres, so they don't care where the tail stock is, and a bit of lanolin on the centre tips and just enough pressure to hold them at cantre. I trued my Thruxton crank and got it well under a thou. As for the guru's cranks, (and I won't ever admit publicly that he has done one or two for me) but they usually run well under a thou both sides. I recall the last one being at 0 one side and 4 10'ths the other.

they're also done with a .003 per in taper in the wheels and on the pin and aligned almost there before being pressed all the way home. And you need to beat them to get them to move at all.

 

[Chris Launders]

As I don't have knife edge rollers I've made knife edge V's and fit bearings to the crank which then sit on the knife edges, so it spins freely but will act as though it's on knife edge rollers.

 

[Cyborg]

And he taught me to check them, first thing is to confirm the centres are, and if not, out comes the dremel to make them deadly. Then they are checked between two dead centres, so they don't care where the tail stock is.

Point taken, and again I’m no expert, but if the tailstock is very far off, doesn’t that effect the way the centres fit in the centres? I’ll have to think about... probably should have thought about it before I wrote this. Maybe cutting too many unintentional tapers has clouded my view of things.

Would dead centres automatically be better? I would have thought live ones would be fine as long as they haven’t been abused.

 

[Robert Watson]

Anything rolling on bearings must be suspect as the bearing have some clearance? -and when we are down to 10ths?
If the dead centres are offset by what, a few thou or 1/2 inch? -and you are measuring the run out at the bearing seats. So you put it up in dead centres and rotate the shaft with an indicator on the closest finished surface to the shaft end in the shaft centre, and if it is true there, then you are good to go, "true" being relative, if you are looking at less than a thou at the bearing seat it seem reasonable that a 10th would be OK at the shaft end sitting on the centre. There are all the theories, and the then there is practical. I think the Velo book calls for less than 1 1/2 or 2 thou run out as acceptable...............

Now if only I could remember the name of the minute wear that occurs just from the act of measuring a part..........

 

[Cyborg]

Observer effect.

 

[Bill Thomas]

Must admit, In the first video, It looked more than 50 thou,
When he first put it in the cases, I thought I could see a tight spot, But he fluffed over it, As I would ,
That's what I fear mine will look like.
While playing on the Lathe, At first it got me going !, Then I found the old spinning centre was not running true, This was just checking a mainshaft,
So I bought a new one, Wish I had bought 2, Maybe I should do that.

 

[greg brillus]

Hi there Bill, are you using original flywheels.....?.......Were you planning on using a shorter conrod to compensate for the longer stroke.......... Cheers.......... Greg.

 

[Bill Thomas]

Hello Greg, Yes standard wheels, Going to weld them up a bit and rebore 1/4" nearer the outside.
Standard 1" Alpha bigend, Justa bit of Fun, I am too old to test it in race conditions.
Got a new Carillo Rod 1/4" shorter, Should be 560 cc ?, Trying to do it on the cheap !!, Joke !.
I now find it would have been cheaper to have got, Trev' or Conways to have done it, Too late now.
I keep putting the job off, Silly Old Sod, But must do it soon.