I think I got the idea from you ?.
Flywheel alignment
- Thread starter Bill Thomas
- Start date
I have a Norton Inter crank that you could have a go at. It drove me nuts and I shoved it off to the side. Wondering if it has mismatched flywheels or something. Maybe I should drag it out and give it another try. Perhaps large quantities of Jenever would help me figure out where to hit it?
This "between centres" in a lathe procedure for trueing cranks may look very impressive and scientific - but in real life I do not find it effective. Apart from questionable centres in the mainshafts that you have to rework in most cases you can only do guesswork what runout you will get when installing the crank by its bearings in the crank case. Allright, most will not check this in an assembled engine and hope for the best. So instead I belong to the religion of placing the crank on simple hacksawed alu plates with prisms/ vees in them. No need to have any bearings on these , just a bit of oil on the mainshafts - you don´t see thousand rpms when checking for runouts I guess ?? And it is simple as anything to fabricate with excellent measuring results plus reliability to KNOW you will have same runout in the finished engine like on your simple vees - very unlike to the between centres procedure.
I would better skip the traditional measuring clocks, even more so the digital types, for checking crank runouts and in fact almost all setting up jobs in the workshop, and get me the lever type clocks with minimal internal friction , low measuring force and great access to all places you want to check. The clumsy big clocks are a PITA for that kind of jobs. At a tenner or two you get them from anywhere and enjoy a new life at your machinery.
I did video clips today of my homemade cranks , see youtube links below, showing runouts at half a thou, 0,01 mm both ends. I had a jig for pressing in the 40 mm crank pin and was lucky to get just 0,06mm runout after pressing home. But then no way to true up with a heavy copper mallet, nor with a heavy steel hammer onto a flat piece of alu to keep crank webs nice - or I am too old and weak to shift them. So I used the drillings in the crank , shoved lengths of round bar through to put the lot in my hydraulic press for getting runouts to 0 - 0,02 mm finally.
The tensile strength of my crank webs is a LOT higher than standard Vincent so no wonder I had very high press forces and no chance to bash it into zero runout with big hammers. Have you heared of the "Ding-test" in the toolroom practice ? You find a piece of known steel quality and ding it onto the unknown item you´d like to test. The one part with the bigger ding on its edge is lower in hardness and tensile strength, same dings , same strengths. My photo shows an original B-Rap crank against my homemade crank, no ding at all at the new part.
As to securing mainshafts in the webs, the Mills pin was a joke from day one anyway. Why not do a mod by broaching a 5mm keyway into the web bore and mill a woodruff or better a parallel key into the mains and you are safe ever after ??
Vic
HRD crank clip 1
HD crank clip 2
I would better skip the traditional measuring clocks, even more so the digital types, for checking crank runouts and in fact almost all setting up jobs in the workshop, and get me the lever type clocks with minimal internal friction , low measuring force and great access to all places you want to check. The clumsy big clocks are a PITA for that kind of jobs. At a tenner or two you get them from anywhere and enjoy a new life at your machinery.
I did video clips today of my homemade cranks , see youtube links below, showing runouts at half a thou, 0,01 mm both ends. I had a jig for pressing in the 40 mm crank pin and was lucky to get just 0,06mm runout after pressing home. But then no way to true up with a heavy copper mallet, nor with a heavy steel hammer onto a flat piece of alu to keep crank webs nice - or I am too old and weak to shift them. So I used the drillings in the crank , shoved lengths of round bar through to put the lot in my hydraulic press for getting runouts to 0 - 0,02 mm finally.
The tensile strength of my crank webs is a LOT higher than standard Vincent so no wonder I had very high press forces and no chance to bash it into zero runout with big hammers. Have you heared of the "Ding-test" in the toolroom practice ? You find a piece of known steel quality and ding it onto the unknown item you´d like to test. The one part with the bigger ding on its edge is lower in hardness and tensile strength, same dings , same strengths. My photo shows an original B-Rap crank against my homemade crank, no ding at all at the new part.
As to securing mainshafts in the webs, the Mills pin was a joke from day one anyway. Why not do a mod by broaching a 5mm keyway into the web bore and mill a woodruff or better a parallel key into the mains and you are safe ever after ??
Vic
HRD crank clip 1
HD crank clip 2
All very nice tools, But how often would I use them.
My old Comet has never been touched since 1977, When I built it and the Crank was done by Tony Maughan.
Which I have raced as well as used on the road.
In my video you could see by eye 50 thou !!, It looked more to me.
And the straight edge, When wrong, Was easy to see.
It will be interesting to me, If I can make mine work, I know it's a bit beyond me, But S--t or Bust !.
My old Comet has never been touched since 1977, When I built it and the Crank was done by Tony Maughan.
Which I have raced as well as used on the road.
In my video you could see by eye 50 thou !!, It looked more to me.
And the straight edge, When wrong, Was easy to see.
It will be interesting to me, If I can make mine work, I know it's a bit beyond me, But S--t or Bust !.
Well I say go for it. My Comet crank was the first one for me. Eventually getting it within tolerances definitely gave me a sense of satisfaction. Also fun learning which I’m told helps to postpone the brain rot. BTW, my suspension comment was in reference to the long stroke and not meant to discourage you in any way. There must be a machinist hiding somewhere in some basement close by who could assist you with drilling and reaming etc. I discovered one right across the street. Have talked to him for years.. his current job has nothing to do with machining, although I knew he had a small mill in his garage. Recently I brought up the subject of sharpening tool steel and it became obvious he was knowledgeable. Turns out he started out as a journeyman machinist.
The point is I like to push myself sometimes, I think I have a good chance.
I don't have much faith in other people, I have had some bad work done.
Peter is worried where the hole will be, But if it's out a bit, I don't see a problem, I will have to rebalance it anyway, I had my flywheels narrowed on my Twin Racer, Years ago, And I said to the bloke I will have to rebalance it, And he said no !, So I put it together, At 100mph over the finish line of a standing 1/4 mile,
I could not see, It shook that much !.
So I took it apart and rebalanced it, Then it was even lighter !.
But worked OK.
Sorry if I was a bit Ratty. Cheers Bill.
I don't have much faith in other people, I have had some bad work done.
Peter is worried where the hole will be, But if it's out a bit, I don't see a problem, I will have to rebalance it anyway, I had my flywheels narrowed on my Twin Racer, Years ago, And I said to the bloke I will have to rebalance it, And he said no !, So I put it together, At 100mph over the finish line of a standing 1/4 mile,
I could not see, It shook that much !.
So I took it apart and rebalanced it, Then it was even lighter !.
But worked OK.
Sorry if I was a bit Ratty. Cheers Bill.
I have done quite a few smaller cranks in the last few years for a shop as well as my own JAP V-twin ones, it's not hard at all, one tip I have is to mark one flywheel 90 degrees from where the crank pin is with a marker pen, so that you have a reference point when you hit it with your big copper hammer, because if you don't mark it you WILL lose where you've just hit when you need to hit it again.