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post #1 of 17 (permalink) Old Jul 28th, 01, 09:03 AM Thread Starter
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Marc
 
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Hi,
I speak French, and I 'd like to know what is a roller cam, and a flat tappet.
I understand the camshaft, crankshaft, rod, piston, rocker cam, push rod.
Thank you. Maybe it should be easier with a picture,...
Marc
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post #2 of 17 (permalink) Old Jul 28th, 01, 10:31 AM
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Bill
 
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Marc,
Roller camshafts use a lifter (also called a tappet) that has a roller on the bottom where it runs on the camshaft. A flat "tappet" camshaft uses a flat faced lifter, it just "rubs" on the camshaft as it moves and has no roller.
Hope this helps,

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post #3 of 17 (permalink) Old Jul 28th, 01, 10:37 AM
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Pictures: http://www.cranecams.com/master/lifter.htm Bill explained it exactly.
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post #4 of 17 (permalink) Old Jul 28th, 01, 02:09 PM
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j'ai habite en Zaire pour trois ans. Pardonnez-moi, mes francais est horrible. Le arbre (camshaft?) est un piece dans le moteur qui faire marche l'ouvreture et le fermier (closing?) de les valves. Il y a deux sorte.

Le roller sorte a un (lifter) avec un bagnole. La bagnole sur la (lifter?) abaisse le temperature et la (friction?). Avec ca, l'arbre peux ouvre les valves rapidement et les valves reste ouvre pour beaucoup de temps aussie. Avec ca, il y a plus de power du cheval (horsepower?).

Il y a aussie duex sorte du les rolleurs, une hydraulic et une solide. Utilize le hydraulic pour le rue, et le solide pour un voiture dans que tu fait s'emballer le moteur.

Putain de merde! Ma francais est tres mal.
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post #5 of 17 (permalink) Old Jul 28th, 01, 02:44 PM
 
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Boodle,
I will ask my daughter to read to me what you said, he, he!! pdq67



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post #6 of 17 (permalink) Old Jul 29th, 01, 12:02 AM Thread Starter
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Thanks Guys !
Well Boodle, good try! But I don't understand what you means with "bagnole".
If you explained with non tech English words, I'd understand without problem.
But thank you though. I'll try to understand while looking at cranecams.com
Marc
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post #7 of 17 (permalink) Old Jul 29th, 01, 07:32 AM
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Marc,

I mean wheel. On a roller type camshaft, the lifter uses a small wheel that allows the camshafts lobe (the ramp that pushes on the lifter) to be designed differently. It allows the lobe to have a more steep angle and also allows the lobe to be taller, keeping the valve open longer.

By having a more steep angle, the valves open and close at a faster speed.

A non-roller type camshaft doesn't use a wheel on the lifter. Instead, the lifter is flat on the end that the lope hits. Because the lifter is flat on top, it has a sharp angle at the side that can wear out the lobe if the lobe has a steep angle. This means that a non-roller camshaft can't open and close the valves as fast as the roller type or else the lifter could break the camshaft.

Bon chance!
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post #8 of 17 (permalink) Old Jul 29th, 01, 10:34 AM Thread Starter
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OK,
I understand the improvements of the roller cam, but looking on Cranes pictures, I still donít see how it fits to the cam, and the valve. And what is the rod that is on the pictures between those lifters.
The lifter is fit on the cam, isn't it?
the lifter moves the pushrod, that moves the rocker arm, that opens the valve. Or am I wrong?
In fact I don't understand the pictures.
I understand how the cam works on the roller lifter, as you said, Boodle.
Thank you.
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post #9 of 17 (permalink) Old Jul 29th, 01, 11:35 AM
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you are correct about how the system works. The cam lobe pushes the lifter, which pushes the pushrod, which moves the rocker, which opens the valve.

Roller lifters are usually connected in pairs by a bar. I think that is the piece you are describing. The end connected by the bar is the end farthest from the camshaft. The pushrods sit on this end. Non-roller lifters are not connected to one another like roller lifters are. I don't know why this is. Anybody got any idea?

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post #10 of 17 (permalink) Old Jul 29th, 01, 03:56 PM
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If roller lifters were allowed to rotate in their bores BAD things would happen....

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[This message has been edited by ZZ430DropTop67RS (edited 07-29-2001).]
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post #11 of 17 (permalink) Old Jul 29th, 01, 07:23 PM
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yep because if the roller part of the lifter is facing the other way the lobe on the cam will be catching on the sides of the "roller", and in that case you better get out the bacon and eggs 'cuz youll have toast

nate
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post #12 of 17 (permalink) Old Jul 30th, 01, 11:52 AM Thread Starter
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Thank you, now I understand everything. Great!
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post #13 of 17 (permalink) Old Jul 30th, 01, 01:24 PM
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Ah yes. I don't know why I didn't think of that. What if they were to change the wheel to a ball bearing? Wouldn't have to have the connector keeping the lifter from rotating.
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post #14 of 17 (permalink) Old Jul 30th, 01, 02:08 PM
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how would they get the ball bearing to stay in place though??
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post #15 of 17 (permalink) Old Jul 30th, 01, 03:01 PM
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You would not want to use a ball. A ball creates point contact loading that leads to large point-load stresses. A roller creates a line contact that spreads the load over a larger area.

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