Tappet anti-rotation scheme

[pontiacjack]

I hope I'm not violating a forums rule by posting "just for fun"?

This ia an Iskenderian Cams ad from Mar '58. Although I usually enjoy puzzles, I'm at a loss to visualize "automatic, self-locking keys" that require merely "dropping the lifters into place".

These ads didn't run long- way less than a year, if I remember correctly, so I'm guessing the scheme wasn't flawless.

Umm... disregard above, until I figure out how to upload the image!

 

[pontiacjack]

Darn... can't edit the above post... so please diregard my "disregard" sentence above!

 

[patprimmer]

The photos certainly seem to be arranged to hide details.

I had a very early set of Isky roller followers that had blades off the side of the follower that had a tongue and grove principle to stop rotation. I ran them for 20 odd years and sold them in a running engine, so they obviously worked. You would see them from a top view or a side view with correct orientation.

Regards
Pat
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[ivymike]

I've worked on an engine design wherein the flat followers were intentionally displaced slightly along the cam axis vs the lobe crown to promote follower rotation and spread wear evenly.

Since we're talking about roller followers, wouldn't a tiny bit of caster be adequate?

 

[WGJ]

I thought all pushrod engines with either bucket or mushroom followers were aranged to rotate the followers - no?

Bill

 

[patprimmer]

I thought all flat tappet followers or OHC buckets where offset to rotate. The only non roller followers I ever saw that don't rotate are the curved face ones, kinda like a segment out of a large roller that does not roll. It was used on 56hp VWs of pre about 1962 vintage and many over head cam rocker arm follower systems.

I can't see enough castor being possible to accommodate the shift in contact point as the cam profile strikes the roller as the cam rotates. I have never measured it, but it seems like it could go something like 45 deg shift from the axis of the follower on an aggressive profile like a concave or unversed flanked cam.


Regards
Pat
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[NormPeterson]

Caster might not be very effective in preventing rotation when the engine is cold and there is a finite amount of lash. Or at high revs should the lifter get tossed a little going over the nose. The follower would not have to rotate a full 90° where the roller would stop rolling entirely, just having to run at a few degrees off with some amount of slip under the pressure of heavyish valve spring rates can't be a good thing. Given the intended applications for solid roller cams 50-odd years ago, I'd expect both possibilities to occur at least occasionally.


Norm

 

[Lou Scannon]

FWIW, I've recall seeing overhaul manuals that illustrate different tappet wear patterns. A key point was, while rotation is intentional and designed into the geometry, non-rotation is acceptable as long as the resulting wear pattern showed no cause for concern,i.e. due to unacceptable wear.

 

[tbuelna]

pontiacjack,

Here's a couple of Isky lifter patents from that time period.

 

[tbuelna]

forgot to include the second one.

 

[patprimmer]

Yep. The 1958 patent looks like the ones I had.

Regards
Pat
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[pontiacjack]

Okay, thanks. I was putting too much faith in the ad's photograph, and assuming aome clever scheme that avoided link bars.

 

[BrianGar]

Bmw also uses a non-rotating follower with a curved face,

Brian,