| [GMCnet] Lifter Position on cam lobe [message #239157] |
Fri, 07 February 2014 22:08  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
In an email I noted that the reason the lifter spins in an Olds engine was because it runs offset from center on the cam lobe.
Gary said it was because the lobe was tapered, Matt noted the taper was 1 ~ 2 degrees.
It may be an optical illusion but in this photo it sure looks like the "wear" is in the middle of the cam and that the lifter is off
center to the lobe! ;-)
http://www.gmcmhphotos.com/photos/mechanical/p52612-455-cam.html
Regards,
Rob M.
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Lifter Position on cam lobe [message #239165 is a reply to message #239157] |
Sat, 08 February 2014 00:23  |
LarryInSanDiego
Messages: 336
Registered: September 2006
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The lifter face is slightly convex, so wear is in the middle instead of across the entire lobe. In practice, it shifts a bit to one side or the other. The cam lobe is slightly off center as seen in the photo, which gives the lifter it's spin. Some cam lobes I've measured are at a slight angle (front or rear of the lobe is slightly higher), but I'm not sure whether this was just the result of off center lifter wear or that perhaps the lobes may have been ground at a slight angle front to rear - which may explain why an off center lifter still seems to wear the lobe near the middle.
Larry Engelbrecht
San Diego, CA
'73 26' ex-Glacier
TZE063V100319 03/07/73
[Updated on: Sat, 08 February 2014 00:52] Report message to a moderator |
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| Re: [GMCnet] Lifter Position on cam lobe [message #239174 is a reply to message #239157] |
Sat, 08 February 2014 08:43 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| USAussie wrote on Fri, 07 February 2014 23:08 |
G'day,
In an email I noted that the reason the lifter spins in an Olds engine was because it runs offset from center on the cam lobe.
Gary said it was because the lobe was tapered, Matt noted the taper was 1 ~ 2 degrees.
It may be an optical illusion but in this photo it sure looks like the "wear" is in the middle of the cam and that the lifter is off
center to the lobe! 
http://www.gmcmhphotos.com/photos/mechanical/p52612-455-cam.html
Regards,
Rob M.
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Rob,
In practice, the followers (lifters) are seldom centered on the lobes. Things are set up so the wear track is centered on the lobe because it is a disaster if the follower load gets near the edge of the lobe.
In the pictures 52612 and 52613, notice that the visible wear track is very nearly centered on the lobe, BUT - it is not centered on the follower!! This is as it should be. It is a direct result of both the angle of lobe face and the radius of the follower.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Lifter Position on cam lobe [message #239225 is a reply to message #239174] |
Sat, 08 February 2014 18:25 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Matt,
I just don't seem to be able to communicate what I'm saying properly.
I believe that the lifters are slightly convex.
I believe that the cam is ground on an angle.
I can see that the wear pattern on the cam is near the center as it should be.
I believe the fact that the centerline of the cam lobe is not in alignment with the centerline of the lifter will cause the lifter
to rotate in the opposite direction of the cam rotation.
Am I nuts or what?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Matt Colie
Rob,
In practice, the followers (lifters) are seldom centered on the lobes. Things are set up so the wear track is centered on the lobe
because it is a disaster if the follower load gets near the edge of the lobe.
In the pictures 52612 and 52613, notice that the visible wear track is very nearly centered on the lobe, BUT - it is not centered on
the follower!! This is as it should be. It is a direct result of both the angle of lobe face and the radius of the follower.
Matt
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Lifter Position on cam lobe [message #239320 is a reply to message #239270] |
Sun, 09 February 2014 16:34 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Matt,
Thanks, I finally explained myself understandably!
HEY, WAIT A MINUTE, YOU THINK I'M NUTS!
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Matt Colie
I think the answer here is that you are correct on all counts.
But, I don't think it matters which way the followers rotate as long as they do.
Matt
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Lifter Position on cam lobe [message #239344 is a reply to message #239320] |
Sun, 09 February 2014 20:55 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| USAussie wrote on Sun, 09 February 2014 17:34 |
Matt,
Thanks, I finally explained myself understandably!
HEY, WAIT A MINUTE, YOU THINK I'M NUTS!
Regards,
Rob M.
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Rob,
Why would I think that?
Because you have not just 2ea 40Yo Motorhomes, but you have them on two continents on opposite sides of the planet.
I never had any doubt.
The only one I am in doubt about is Helen.
(And Mary, why she hangs are with old sailor is still a mystery.)
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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