Truing Alpha and Villiers crankshafts

[IanCordes]

I have an Alpha full circle crank, and a Villiers bob-weight standard one, both with 5 1/2" rods. They appear sound, smooth big-ends with no up and down movement, good axles etc, but clocking them up on a lathe shows they are both running out around + or - 0.010"; 10 times what they should be!

Any tips on truing them up, or anyone in or around Cornwall who has the requisite skills?

Ian

[Brian Thompson]

Villiers and Alpha Cranks etc.

Hi Ian,

I guess you may have already heard of this, but probably the best info/tips I've seen 'in print' on this topic is in the 'Villiers Singles Improvements Handbook' by John Wood and Rob Carrick, of which there is now an updated 'version 3' available - details here; http://www.lortim.demon.co.uk/pdfbook.htm

There is also a sample page given here to give you an idea of content; http://www.lortim.demon.co.uk/vsih/VSIH3_sample_ch4.pdf

The Villiers 'specialists' are, of course, Simon at Nametab Engineering (http://www.nametabengineering.com/ See also; http://www.nametabengineering.com/services/) or Steve at Villiers Services (http://villiersservices.co.uk/index....4lp1fjjcfnat93) I have used SEP Engineering (http://www.sep-kegworth.co.uk/page1.htm) in the past, but sadly none of these options are close to you. All come highly recommended.

Hope this is of some use anyway Ian, and can anyone else offer any further tips/contacts to help?

Brian.

[John Wakefield]

2 stroke crank true up

This video shows what to do https://www.youtube.com/watch?v=saARVyy4pdY

[dave higgins]

Ian, i am by no means questioning your engineering skills, but are you using a four jaw & clocking the crankshaft to zero next to the jaws,
I have done many cranks & can tell you from experience, that most times, you will find it hard to get an accurate reading using a three jaw.
After setting the run out to zero next to the chuck, i move on to check the run on the far shaft, once this has been trued & run out eliminated, i set it all back up & check it with the tailstock centre in position, so with no runout on the shaft in the chuck & a clean accurate centre in place, & with no runout on the far shaft, the crank has to be accurate, thats how i`ve always done them.
Those bob weight/hammer head cranks used to suffer from crank pin slippage, when any real power was put through them, & many i have replaced, i have drilled another pin in the side of the crankpin to eliminate this.
As for trueing, a judicious blow with a copper hammer to realign the flywheels, then back on v blocks/lathe to check, altough this can take time retrying, thats where the skill comes in, hope this helps, dave.

[Brian Catt]

I would have thought that seeing that much run-out on BOTH cranks is too much of a co-incidence....

[MikeV]

Trueing crankshafts

All you need is a pair of knife edge "v"'s mounted to the width an height you require, can be made by making a wooden u shaped support, a dial guage(obviously) a copper hammer (heavy weight) and plenty of patience!!
If you are using a lathe you can use a centre point in a 3 jaw chuck as long as the chuck is locked and unable to move.

Mike.

[greeves246]

Alpha true crank trueing

Hi ian nice to see you
theres a device called a "ALPHA TRUE" they were used to true the flywheels but could be done in lathe engineers in wadebridge should be able to fly that !
use a rawhide/copper mallet hit ajacent web till it comes into true with two dial gauges

[dave higgins]

Hi mike, a three jaw chuck is not as accurate, as you cannot compensate for wear/worn jaws etc in the chuck & also any disscrepancies in the the crank shaft itself
When its zero in a four jaw, its absolute.....

[IanCordes]

Good info gents. The guy in the video made it look easy! I am no engineer, so I took it to a small local engineering works yesterday, but I do wonder if the lathe might not be the way to do it, in the light of the comment by greeves246; sorry mate, don't know your name.

I have the Carrick/Wood book, and in fact took a copy of the relevant page, to show them how it should be done. An hour later, and we seemed to be getting nowhere. They checked the run-out on the lathe, marked the high spots, then rested it on V blocks and with a very similar copper hammer, whacked it. It took waaay more weight behind the hammer than the guy in the video was using, for it to sometimes move, sometimes not. We seemed to be chasing a moving target, so in the end they gave up, as they were shutting shop. That was on an Alpha crank that had been in my Greeves, but was vibrating quite a bit before I laid the bike up a few years ago. They then checked the bob weight crank, found that was out, and my 3rd one, an Alpha which Simon Bateman had rebuilt for me, if I recall, and that was within .001"; spot on.
I will see if I can sort out some V blocks, and have a go with the bob weight crank my self. It may just be that the one we tried was particularly tight on the crankpin, perhaps?
Cheers. Ian

[greeves246]

Gary gwillam aka greeves246

ian yes lathe best two revolving centers i use needs no trueing ir two "v" blocks
dave yes the scroll on a 3 jaw can be out mine is

[John Wakefield]

Holding between centres in a lathe is not a good idea, as the guy in the video says, the ends could be damaged and therefore give false readings. The V blocks is the best way.

[MikeV]

Trueing crankshafts

Hi Dave,

The point I was trying to make was that the 2 centres of your crankshaft trueing set -up do not have to be perfectly in line. If you use the centering points drilled in the end of each main bearing shafts, with the chuck locked and just enough pressure applied by the tail stock to allow free movement of the crank rotationly without any lateral free-play there is no problem with slightly out of line centre points as your runout measurements are taken off of the main bearing shafts when you revolve the crankshaft, not the chuck.
I have done a few Jawa crank's this way with excellent results.

Mike.

[dave higgins]

Hi mike, i know what your saying, but to get a true centre line for accuracy, the only way is to use a four jaw & true up off a machined face, ie the main bearing journel, when that is set to zero, the opposite shaft, must then be trued to suit the first shaft...zero.
In reallity, you will never get it, in mass production cranks, but to get within a few thou, with most engines, it is within tolerence.


Reading back on this thread i realise why we are getting confused, i tend to use large lathes & which i hold the whole crankshaft in the jaws itself, not a centre held in the jaws to align the crank, so sorry for the confusion mike....

[dave higgins]

Holding between centres in a lathe is not a good idea, as the guy in the video says, the ends could be damaged and therefore give false readings. The V blocks is the best way.

If you read my first post john....properly, you will see that i did not use centres to true, only after, to check..........................

[IanCordes]

ian yes lathe best two revolving centers i use needs no trueing ir two "v" blocks

Haha! Gary... gotcha!

Not quite sure what you are saying here, though. I have done a quick search on the net for knife-edge V blocks and can't find any. What have you got in your workshop? Maybe I should pay you a visit....? Cheers. Ian