ET: Engine (Twin) Identifying cams
- Thread starter jim burgess
- Start date
I would like to thank you all for your time and input into this little thread, I used to get e-mail notifications when a response was made to a thread but this seems to no longer happen, I don't know why, but the result is that I have been a little tardy in my response. My sincere apologies.
Thanks for the thoughts on the "wobble" I may not have made things clear. I don't think the wheel is eccentric to the shaft, it is, in fact not perpendicular to the axis of the shaft, therefore when viewed side on it moves from inboard to outboard by 10 thou. So when in mesh with the large idler the cam wheel will tend to move from back to front by 10 thou, in 180 degrees of rotation, so it oscillates. This will mean that the teeth of the cam wheel will move in an arc, in out, in out, I have tried to resist "shake it all about," but clearly I have failed... There will be points at which the apex of the tooth is pushed into firmer contact, first at the front then at the rear. Even as I write this I become more and more convinced that this is not a reliable component, I just had this vague hope that somebody out there would tell me that I'm being over fussy and therefore wrong...
I was also hoping that I might be able to visually compare the profile to a picture of a cam to confirm. I have read so much about the opening, closing and readings at max lift and their variability that I think I would despair at trying to identify a cam this way.
Many thanks for all your help.
jim
Thanks for the thoughts on the "wobble" I may not have made things clear. I don't think the wheel is eccentric to the shaft, it is, in fact not perpendicular to the axis of the shaft, therefore when viewed side on it moves from inboard to outboard by 10 thou. So when in mesh with the large idler the cam wheel will tend to move from back to front by 10 thou, in 180 degrees of rotation, so it oscillates. This will mean that the teeth of the cam wheel will move in an arc, in out, in out, I have tried to resist "shake it all about," but clearly I have failed... There will be points at which the apex of the tooth is pushed into firmer contact, first at the front then at the rear. Even as I write this I become more and more convinced that this is not a reliable component, I just had this vague hope that somebody out there would tell me that I'm being over fussy and therefore wrong...
I was also hoping that I might be able to visually compare the profile to a picture of a cam to confirm. I have read so much about the opening, closing and readings at max lift and their variability that I think I would despair at trying to identify a cam this way.
Many thanks for all your help.
jim
Jim, that suggests to me that the hole through the cam pinion is not perpendicular to the face of the cam wheel. Unless you find something like swarf in the hole I would suggest scrapping the wheel. The thought of a cam pinion wobbling in and out by ten thou causes an attack of the conniptions to me. Regarding what type of cam you have then it is not hard, but it is tedious, to find out. Just use the degree wheel and DTI method and measure the valve lift every ten degrees of engine rotation. Over the years there have been some rubbish cams made for Vincents and unless you know the history of these cams it is better to be safe. It will only take an hour or two to do the measurements, put them into a spread sheet and plot a graph. You can even get the spread sheet to calculate the speed and, more importantly, the acceleration of the valve due to the cam. I can help you with this if needed, via email, but it is not hard to do.
Jim,
If your cam assembly is assembled out of square, it definitely should be tossed. I would be surprised if the "out of square" assembly would not wobble your cam spindle out of line and out of the case. I have never run across this, but considering the work done on your pinion, I would assume that it was not done correctly.
Although I have used many welded pinions on camshafts, I switched to the use of an anchor "pin" to avoid applying any heat to the cam assembly to avoid any type of movement due to warping from excessive heat.
I have found that the large idler boss can be bolted down to the case with some dirt underneath, which creates the same problem you have found with your cam with the idler shaft. I began checking the "squareness" of the large idler shaft.
I check the distance to the parting line at a number of spots to make sure the boss is square. The tool is not the best design for this, it was just a test to make sure the concept could work. I also used it to check the spindle heights for installation. Something similar might give a quick indication of how square the cam spindle is.
David
If your cam assembly is assembled out of square, it definitely should be tossed. I would be surprised if the "out of square" assembly would not wobble your cam spindle out of line and out of the case. I have never run across this, but considering the work done on your pinion, I would assume that it was not done correctly.
Although I have used many welded pinions on camshafts, I switched to the use of an anchor "pin" to avoid applying any heat to the cam assembly to avoid any type of movement due to warping from excessive heat.
I have found that the large idler boss can be bolted down to the case with some dirt underneath, which creates the same problem you have found with your cam with the idler shaft. I began checking the "squareness" of the large idler shaft.
I check the distance to the parting line at a number of spots to make sure the boss is square. The tool is not the best design for this, it was just a test to make sure the concept could work. I also used it to check the spindle heights for installation. Something similar might give a quick indication of how square the cam spindle is.
David
That tool would only check for squareness to the gasket face, no? Obviously, all the spindles need to be parallel to the axis through the crankshaft. So the gasket face should first be checked for flatness and then for squareness to the crank. If that all checks out, a longer version of your tool which can sweep the entire gasket face should work. But then, with all the excellent work you've done, I'm sure you have thought this through.
Gary
Gary
I think what Jim is trying to say is: because he had the gear wheel welded to the cam spindle, when it cooled it was not in alignment. So, the spindle rotating should not, in my opinion, wear out the case bushings, as the only thing wobbling is the gear wheel. That will in effect wear out the idler. Toss it Jim. I like the roller bearing press fit to keep it all in alignment. Welding the gear wheel to the cam spindle should be very questionable indeed. Just my 2 cents.
The timing case face is the datum and should be square to the crank.
I didn't weld the wheel on, honest, I'm just checking the thing over for a club member. I can see how welding could work, I can understand why it was done. But my very limited experience with welding gear leaves me feeling that it is a process likely to create as many problems as it solves, especially as in this case it is a short weld on the back of the wheel in one position only. Bob Dunn once showed me a primary case for a twin that looked like a banana after an inexpert welding job. Maybe 25mm out of alignment from front to rear, his job was to make it all be straight again... ho hum...
In this case the shaft and wheel will fit on the slightly worn spindle, but a new spindle will not enter so I suspect the actual shaft may be out of true, however close inspection also indicates the fitment of the bearing with a blunt instrument and kinetic energy...
Looking at the contents of the timing case does leave me wondering: Why are the spindles so damn skinny? Why don't they screw into the case? Why not have much bigger bearing surfaces for all components? Why no needle rollers? It is hard to imagine the immediate post war era and the restrictions that had to be worked to at that time, but I can't help seeing the timing case as a group of missed opportunities. But then we are 70 years down range of the launch of the vehicles and I guess nobody thought we would still be working on them.
Many thanks to you all!
Jim
In this case the shaft and wheel will fit on the slightly worn spindle, but a new spindle will not enter so I suspect the actual shaft may be out of true, however close inspection also indicates the fitment of the bearing with a blunt instrument and kinetic energy...
Looking at the contents of the timing case does leave me wondering: Why are the spindles so damn skinny? Why don't they screw into the case? Why not have much bigger bearing surfaces for all components? Why no needle rollers? It is hard to imagine the immediate post war era and the restrictions that had to be worked to at that time, but I can't help seeing the timing case as a group of missed opportunities. But then we are 70 years down range of the launch of the vehicles and I guess nobody thought we would still be working on them.
Many thanks to you all!
Jim
I take your point but I think I could design a spindle with a shoulder that would screw up tight leaving the holes pointing downwards 45 degrees left or right?