Is solid roller lifter loading really the highest at idle?

[ZIGGY]

desoto - my bad. Shot too soon. Just looked velocity up.
I withdraw my quickdraw. Sorry.

[TheEngineWorks.com]

I have never really felt that idling was the culprit for failed rollers, I never bought into that and always thought it was urban legend. I have NEVER had anyone give me a clear reason that I would buy into to support such.

If that was the case then your typical "hydraulic" street rollers would see failures at some point.. Taxi cabs, police cars and the such have roller cams in them and DON'T have roller failures, although they may spend a lot of time at idle. I NEVER see hyd. rollers fail, even with a million miles on them.

Due to recently failure, I have started to go in the direction of LASH being the biggest culprit to roller failure, its the single biggest difference between the hyd. roller and solid.

I feel setting up a solid roller with as little "running" lash as possible may get close to solving the issues, as well as modifying the cam profile for that environment.

I strongly believe that the extreme impact the roller takes as the lash goes away is the single most destructive force on the ENTIRE valve train, not only the roller, but specifically the roller as it is at the epicenter of the event and has no buffer between it, compared to other parts of the valvetrain.

I believe I started the conversion of lash being the culprit in the last roller lifter failure thread, I'm gonna stick with that theme in this thread.

[Lasher...]

Well I still think that " For a Street / Strip " car that will see far more street driving than blasting the quarter mile.... then it's better to give up a few ponies and use a lobe(s) with an older school constant velocity clearence ramp or simular rather than the more abusive so called " ramps "........ yes the newer ones will out power the old ones..... but you just might find the old ones still will run a decient number and are likely to live longer...... and often times a " Street car " spends 98 % of it's time at part throttle so you might not even miss the power difference......... especially if you want it to last for 30,000 miles or more.

I dont think it's so much that there is lash .... but more in how we get from the base circle to the lash point and beyond on the opening and just the opposite on the closeing...... a lot of different ways of doing that..... and for every action there is that opposite and equal reaction...... hit em hard and make the power.... but it is more likely to bite you...... hit em slow and your down some ponies but its easier on parts.

[TRN]

Mr. 540,
I understand exactly what you are trying to say. I wish you the same. Velocity and acceleration are not the same. Ask a bungee jumper if they feel no force (F=ma) as they stop, and change direction. Better yet, get yourself a bungee cord, tie it firmly around yourself and to a large tree, and starting at the tree ride a motorcycle away from the tree. As you reach zero velocity, ask yourself if you feel any force (F=ma) applied. And please let me videotape your physics experiment. I will put it on youtube for the viewing pleasure and education of everyone.

[Rizzle]

Now if it was the lash that is killing the lifters, wouldn't a simple rev kit keep the rollers in contact with the lobes better then the valve spring, and allow the lash to be made up at some other point?

[CamKing]

Now if it was the lash that is killing the lifters, wouldn't a simple rev kit keep the rollers in contact with the lobes better then the valve spring, and allow the lash to be made up at some other point?

Yes.
It may also move the high acceleration from the lash to the next weakest link in the valvetrain.
A rev-kit may make the lifters live, and cause the rollers on the rockers to fail.

If you look at the GM crate motor hydraulic rollers, you're looking at .330" lobe lifts with not much spring pressure pushing against it.

I believe the biggest problem is the lash.
I looked at a GM crate HR cam, and a 244@.050"/.406" Lobe lift solid roller of mine.

Max Velocity
GM's HR: .00795"
My Roller: .00836"

Max Acceleration
GM's HR: .00037"
My Roller: .00044"

Acceleration at 1st point of valve movement(Assuming the lifter is following the ramp)
GM's HR: .00028"
My Roller: .00022"

Now if the solid roller lifter doesn't follow the ramp until the lash is taken out, the acceleration at that point could jump as high as .00109"(about 4 times higher then the hydraulic roller).
A rev-kit will keep this from happening at the lifter wheel, but it will move it to somewhere else in the valvetrain.[/b]

[Doug F]

Camking,
WHat is the acceleration at the lash takeup point on a "super agressive" lobe, say something a sprint car might use. Maybe not one of your designs but stuff that you've seen that might be rough on valve train components?

What is the peak accel on such a lobe?

[540 RAT]

OK, this discussion has gotten a little nutty. But what else is new? The original discussion only had to do with whether or not the highest load on a solid roller lifter was at idle or at max rpm. While there are no doubt a few diehards who still don't quite "get it", I think for the most part we've shown that the higher the rpm, the higher the load the lifter feels. But now people are bouncing off the walls about lifter acceleration. Most people who are gearheads no doubt have a pretty good idea of what is really going on here, but they may not great at expressing their thoughts very well in type, as opposed to verbal discussion. I'm probably guilty of that myself. And maybe some are simply confused about some of the details. But the one about a bungee cord backing up the idea that a lifter's acceleration over the nose is not zero, is flat wrong and just plain silly. A bungee cord is simply providing an applied load, nothing more, and that could be measured in lbs, just as could any spring. But acceleration is the rate of change of a velocity, given in ft per second squared. Two entirely different things. Perhaps dusting off those old Physics books would be in order.

I'll make an attempt to get everyone on the same page, and see if I can explain a few things in a manner that everyone can follow. In Physics, an example of something that DOES have an acceleration even though it is not moving, is a projectile like a bullet for example, that is shot straight up into the air. It's acceleration ceases the instant it leaves the barrel, and it only has an initial velocity. Then it immediately begins to slow because of the downward acceleration due to gravity. And gravity affects it the whole time its going up, stopping, and coming back down. So, even when it is dead stopped, before coming back down, it is still under the affects of acceleration due to gravity. Gravity slowed it, stopped it, and pulled it back to earth.

But we are NOT looking at a lifter as a projectile motion problem in school. For our purposes, let's ignore the affects of gravity on our hypothetical lifter, since the affects are quite small for what we are looking at. Now for an analogy we can all identify with, I'll use John Force and his Mustang Funny Car doing a burnout. So, John begins his burnout and the car feels some ACCELeration since it keeps speeding up, and we'll call that positive for the sake of keeping things simple and easy to follow. When he's gone as far as Coil will allow, he lifts, and the car DECELerates since it keeps slowing down, we'll call that negative for the sake of simplicity, just as before. Even though he is still going the same direction, his Flopper has gone from feeling a positive acceleration to feeling a negative acceleration or deceleration. It went from positive to negative without ever changing directions.

Now he comes to a dead stop so that he can put 'er in reverse, so that he can backup to the starting line. When he came to that dead stop, he has NO acceleration either positive or negative. NO decelleration, NO NOTHING, HE'S STOPPED dead in his tracks. He throws her in reverse and starts going backwards. Now the car feels some acceleration (positive, since he keeps speeding up) for a bit, then he lifts again. Now the car feels deceleration (negative, since it keeps slowing down). Easy to follow right? I can't imagine how anyone could argue with any of this. It is as simple and clear as falling off a log.

Its really the same concept with the lifter. It speeds up initially (positive acceleration) on its way up, and at some point begins to slow down (negative acceleration or deceleration) as it approaches the nose. When it reaches the nose it stops dead in its tracks. NO ACCELERATION, NO DECELERATION, NO NOTHING, ITS JUST STOPPED DEAD. Here it only feels the full force of the valve spring pushing back on it, assuming no valve float. So, as I've said before, every lifter feels no acceleration whatsoever when stopped on the nose. It feels max spring pressure, but does NOT feel acceleration of any kind (remember, we are ignoring the affects due to gravity). It can't, you cannot change the laws of Physics. Then the lifter starts back down the backside of the lobe, where it rinses and repeats. Its really that simple. This stuff is not Rocket Science.

The lifter feels low valve spring force, but high forces due to accleration on the way up the lobe/lifter bore. As it goes up, the spring force becomes greater and greater, while at some point, the force due to acceleration peaks. The particular point at which the sum of the force due to acceleration and the force due to the valve spring are the highest, is where the lifter feels its highest load. And since the force due to acceleration is greater as the rpm rises, it again tells you that the total force on the lifter is highest at max rpm, not at idle.

Hopefully this helped clear up some of the confusion. If not, then remember those old Physics books???

[540 RAT]

I have never really felt that idling was the culprit for failed rollers, I never bought into that and always thought it was urban legend. I have NEVER had anyone give me a clear reason that I would buy into to support such.

If that was the case then your typical "hydraulic" street rollers would see failures at some point.. Taxi cabs, police cars and the such have roller cams in them and DON'T have roller failures, although they may spend a lot of time at idle. I NEVER see hyd. rollers fail, even with a million miles on them.

I agree with you here. I have to believe that this came from when the older roller lifters didn't have pressue fed oiling. And since old habits diehard, people continue to say it.

[Doug F]

Why is it "nutty"? You keep talking about F=MA. "A" is particular to a specific lobe and a specific point on that lobe and RPM. Understanding different cam designs can better allow someone to understand the impact a lobe profile has on the durability of the rest of the valve train components.

Why aren't you interested in a little education from some people that do this for a living like Camking?

[Unkl Ian]

How do the axles and bearings in the OEM hyd rollers compare to the race rollers ?

Size,material,hardness,etc.

[CamKing]

How do the axles and bearings in the OEM hyd rollers compare to the race rollers ?

Size,material,hardness,etc.

The race rollers are stronger.
It's not a material issue.

The "hammer blow" of the lobe hitting the solid roller at the lash point is 4 times harder then what the hydraulic roller sees.

[andyf]

Mike,

Are the solid roller cams marketed as "street rollers" designed to have lower acceleration on the ramps? Is that the main difference between a street roller lobe and a race lobe?

[CamKing]

Mike,

Are the solid roller cams marketed as "street rollers" designed to have lower acceleration on the ramps? Is that the main difference between a street roller lobe and a race lobe?

I don't know what other companies do.
My Street Rollers (SR Series) have a slower ramp, and less max acceleration then my racing rollers.

[540 RAT]

Why aren't you interested in a little education from some people that do this for a living like Camking?

Obviously, you are one of those who still doesn't "get it". Your loss. If you did "get it", you'd know that what I said pertains to any lobe design in general, not a certain lobe in particular. We all know that more radical lobes will generate higher acceleration rates, which is still absolutely in line with my "general" explanation. I'm not sure what more I can say to help you understand, what is really a pretty basic concept.

And I don't recall off the top of my head, where my explanation runs counter to anything CamKing has said. He seems very knowledgeable to me, and has provided a lot of good info. So, I have no idea what you are talking about, with regard to him.