E: Engine Checking Vincent crankshaft alignment

[craig]

Seems I have a clowns collection of dial indicators and bases.
80-90 year old lathe an acceptable fixture?
I need to know the best method of checking and improving crankshaft alignment.

Is the location of these dial indicators appropriate? top of all.
Is rotating crank on shaft end centers the best method?

Reading are 180 deg out , right side +.003/.002 when left side is zero, vice versa.
crank pin is at 90 deg front /rear at the high read.

Are these readings acceptable as is ?
or should action be taken?
I have a lead knock off hammer somewhere in my vintage sports car tool kits.
Should the E57 crankpin nut be loosened?

 

[passenger0_0]

Craig, unless you grind the centres of each mainshaft before mounting you will not reliably be able to true a built-up crankshaft turning on centres. These are often distorted due to past use, hammering, and the use of pullers.
Because the mainshafts run on bearings, you are better off using plain vee-blocks located where the inner main bearings run. Please don't support the mainshafts on live bearings as these have their own run out which gets added to the total figure.

 

[oexing]

Same old crap logic with "between center" checks. How can you know what the crank ends do in the engine when your crank is NOT supported/rotating at the main bearing places ? You can only do a questionable guess when you squeeze the crank by the center drills. Better get two pieces of alu or plywood and cut Vees in them and support the crank close to the crankwebs . A bit of oil on Vees is allright for slow turning the crank with clocks at outmost uninterrupted diameters. In the engine it will be exactly the same condition so depending on your findings you can do a better guess if all is well. I´d like to see less than 1 thou on both ends else there will be funny loads on bearings and engine case bearing seats. In my Youtube clips below the indicators are NOT imperial in thou but 0.01mm graduations. These old clocks in your pictures are actually awkward in use in the workshop. For checks on machinery better get lever indicators, they are a lot more sensitive with less spring load on tips and less internal friction . Plus you can reach into places and edges with levers , not so with the old clock shaft.

Vic

 

[passenger0_0]

Well described Oexing. This is one job the must be done right, otherwise the main bearings will certainly fret and come loose in the crankcase.

 

[Chris Launders]

Ignore the flywheels, it's the shafts that matter.

 

[Damien McGouran]

Notwithstanding all of the excellent advice above, if you are intend on using the Atlas lathe, don't use the 3 jaw chuck to hold one end of the crank. Remove the chuck and work between two dead centres, even then check the alignment of the lathe between the tailstock and the headstock to ensure the lathe is accurate. If it's outa wack, no dial gauge will give correct readings.

 

[timetraveller]

I agree with Chris above. If I have understood your figures correctly then is sounds like one of the flywheels needs to be rotated about the crank pin. I do not use a lead hammer. Instead I hold the whole flywheel assembly by the drive side mainshaft and using its inertia to provide the force I bring it down sharply on an imovable object, concrete floor or whatever and I provide protection against damage by using a piece of oak or similar at the contact point.

 

[craig]

Factory fixture


Is it successful practice to "realign" by blunt force an in-service Vincent crankshaft?

 

[Chris Launders]

Having rebuilt many cranks for other makes one piece of advice I will give that will help no end is with a marker pen mark one flywheel at a point 90 degrees to the crankpin in one place only, this will give you a quick reference point to work from, it's easy to get confused which flywheel, you hit which way last.
Taping the rods together will help as well.

 

[craig]

It would seem to me that checking runout using crank end centers would produce a many times more accurate readout than V supports simply based on mechanical advantage.
The V supports would provide a much faster way of providing readouts.
V supports will require very accurate instruments because of a limited mechanical advantage, while crank end support could easily use my collection of eBay .001" dials. I am aware of the suspect crank ends, but I am not seeing damage of any type on the last 5-6 Vincent cranks I was able to observe. I have 3 cranks in the shop right now. I want check cranks prior to outside work and after their return. I would like to avoid purchasing $1000 worth of lever dials for this not so often measures, but...........

I might seek a Harley shop, which seem plentiful, for crank checking as well.

I appreciate all the technical input, especially Vic, Chris, Greg, Norman. This forum is fantastic!

Off to find some big oak lumber pieces