Mushroom Flat Tappets/Tappet Weight

[CamKing]

Maybe Mike can way in say if a mushroom tappet lobe is any different than an a more modern OHC on bucket lobe of the same diameter?

I would design them exactly the same.
In fact, with some of the diesel engines that run mushroom tappets, I use some of my Overhead Bucket follower profiles on them.

[hoffman900]

My point being that if the mushroom and bucket diameter is the same they still have the same max velocity limit. I was looking for Mike to join in because I don't know if on the bucket one might be able to use a higher acceleration.

Stan

Right, they do.

I thought this was interesting...

Generally speaking, for most camshafts, maximum velocity occurs about 30 degrees after liftoff. Maximum acceleration occurs about 60 degrees after liftoff.

Normally, Max acceleration occures before Max velocity.

Here are some examples of distance from lash point to max accel, and max Vel on different cams.

Comp Cam, Pro Cup roller: Max Accel=14 deg, Max Vel=46 deg
Crane cam, 410 sprint roller: Max Accel=30 deg, Max Vel=70 deg
Schrick Cam, BMW overhead bucket: Max Accel=10 deg, Max Vel=48 deg
LSM Cam, Pro Mod roller: Max Accel=32 deg, Max Vel=78 deg
GM 604 crate cam, Hyd roller, Max Accel=27 deg, Max Vel=53 deg
Jones Cam, "Banjo"'s roller: Max Accel=17 deg, Max Vel=59 deg

I just designed a roller cam that gets to max velocity in about 10 degrees, but it's only designed to turn 2,000rpm.

If acceleration has to be the same (same it's governed by the valve spring), but the stiffness may allow the bucket system to accelerate faster (higher jerk).

One thing to think about, is ultimately, they should be both the same at the valve, just that the pushrod system has a rocker to amplify it. Hence Mike's working backwards and Jay's comments on swtiching from FT to Roller cams in NASCAR.
It's one thing to look at Velocity / Acceleration / Jerk at the lobe, but it's almost meaningless without look at the same at the valve. On a 1:1 bucket, it's the same, but a rocker (either pushrod or finger follower) it's not.

I do believe very large diameter buckets can run into issues with trampolining. Obviously the 4 valve stuff likely wouldn't fall into that category.

[frnkeore]

How much HP benefit there would be in reduce reciprocating weight reduction, I can't say but, reduced weight is always a good thing in a race car. The old saying "take care of the ounces and the pounds will take care of themselves" has always applied.

I did a little math this morning and anytime you multiply something by 16, the numbers go up.

It turns out that with the MS tappets weight at 68G and a further push rod weight reduction of 4G. The total weight reduction over 100G .904 FT's is 1.27 lb and for rollers is 2.15 lb.

No matter how you figure it, weight enter acts with HP.

[Stan Weiss]

My point being that if the mushroom and bucket diameter is the same they still have the same max velocity limit. I was looking for Mike to join in because I don't know if on the bucket one might be able to use a higher acceleration.

Stan

Right, they do.

I thought this was interesting...

Generally speaking, for most camshafts, maximum velocity occurs about 30 degrees after liftoff. Maximum acceleration occurs about 60 degrees after liftoff.

Normally, Max acceleration occures before Max velocity.

Here are some examples of distance from lash point to max accel, and max Vel on different cams.

Comp Cam, Pro Cup roller: Max Accel=14 deg, Max Vel=46 deg
Crane cam, 410 sprint roller: Max Accel=30 deg, Max Vel=70 deg
Schrick Cam, BMW overhead bucket: Max Accel=10 deg, Max Vel=48 deg
LSM Cam, Pro Mod roller: Max Accel=32 deg, Max Vel=78 deg
GM 604 crate cam, Hyd roller, Max Accel=27 deg, Max Vel=53 deg
Jones Cam, "Banjo"'s roller: Max Accel=17 deg, Max Vel=59 deg

I just designed a roller cam that gets to max velocity in about 10 degrees, but it's only designed to turn 2,000rpm.

If acceleration has to be the same (same it's governed by the valve spring), but the stiffness may allow the bucket system to accelerate faster (higher jerk).

One thing to think about, is ultimately, they should be both the same at the valve, just that the pushrod system has a rocker to amplify it. Hence Mike's working backwards and Jay's comments on swtiching from FT to Roller cams in NASCAR.
It's one thing to look at Velocity / Acceleration / Jerk at the lobe, but it's almost meaningless without look at the same at the valve. On a 1:1 bucket, it's the same, but a rocker (either pushrod or finger follower) it's not.

I do believe very large diameter buckets can run into issues with trampolining. Obviously the 4 valve stuff likely wouldn't fall into that category.

Bob,
When talking about mushroom / buckets we need to look at the same diameter.

Again maybe Mike can way in. But with roller cams doesn't wheel diameter and base circle diameter come into play as far as what you can do and are all of these examples the same?

Stan

[hoffman900]

My point being that if the mushroom and bucket diameter is the same they still have the same max velocity limit. I was looking for Mike to join in because I don't know if on the bucket one might be able to use a higher acceleration.

Stan

Right, they do.

I thought this was interesting...

Normally, Max acceleration occures before Max velocity.

Here are some examples of distance from lash point to max accel, and max Vel on different cams.

Comp Cam, Pro Cup roller: Max Accel=14 deg, Max Vel=46 deg
Crane cam, 410 sprint roller: Max Accel=30 deg, Max Vel=70 deg
Schrick Cam, BMW overhead bucket: Max Accel=10 deg, Max Vel=48 deg
LSM Cam, Pro Mod roller: Max Accel=32 deg, Max Vel=78 deg
GM 604 crate cam, Hyd roller, Max Accel=27 deg, Max Vel=53 deg
Jones Cam, "Banjo"'s roller: Max Accel=17 deg, Max Vel=59 deg

I just designed a roller cam that gets to max velocity in about 10 degrees, but it's only designed to turn 2,000rpm.

If acceleration has to be the same (same it's governed by the valve spring), but the stiffness may allow the bucket system to accelerate faster (higher jerk).

One thing to think about, is ultimately, they should be both the same at the valve, just that the pushrod system has a rocker to amplify it. Hence Mike's working backwards and Jay's comments on swtiching from FT to Roller cams in NASCAR.
It's one thing to look at Velocity / Acceleration / Jerk at the lobe, but it's almost meaningless without look at the same at the valve. On a 1:1 bucket, it's the same, but a rocker (either pushrod or finger follower) it's not.

I do believe very large diameter buckets can run into issues with trampolining. Obviously the 4 valve stuff likely wouldn't fall into that category.

Bob,
When talking about mushroom / buckets we need to look at the same diameter.

Again maybe Mike can way in. But with roller cams doesn't wheel diameter and base circle diameter come into play as far as what you can do and are all of these examples the same?

Stan

I am hoping Mike chimes in too.

I think what I am getting at is the bucket and the mushroom lifter of the same diameter will have the same peak velocity, for obvious reasons, but the bucket can withstand higher acceleration, so it reaches peak velocity sooner (and would have more lobe area under the curve).

However! My argument is that the bucket lobe is the same as the valve lift curve (accleration / velocity / area under the curve), where the lobe on a pushrod camshaft is being multiplied by the rocker arm. So it may have less lobe area, but the same valve lift area under the curve. Looking at just lobes its not apples to apples. Finger follower systems get the best of both worlds... system stiffness but the multiplication of the lobe.

The NASCAR example was with the extreme rocker arms on the flat tappet engines, they were at the limit of how fast you could open the valve. Going to a roller means a more aggressive lobe, but less rocker ratio.

Obviously, the pneunmatic "springs" like used in F1 (since 1993) and MotoGP (since they switched to 4 strokes), you are not bound by the same restrictions. It's a shame it's been outlawed everywhere but there as I think you would see a huge leap in performance from much more aggressive cam profiles. Being 27yo tech, it's technically vintage technology at this point... at least the first iteration of it.

[swampbuggy]

Bob, so what is it that limits how fast you can open the intake valve on say a roller cammed NASCAR CUP pushrod V-8 ?? "OR" Mike AKA Camking ? Mark H.

[cardo0]

https://www.summitracing.com/search/par ... %20lifters

You have to call Trend, they make them out of tool steel. Hylift Johnsons are available if you just google them. Pioneer, Comp Cams, others have them, also.

That Summit link has only 0.498" dia lifter bodies. Are you implying all the lifter bores have to be sleeved for these. That's not how I recall mushroom tappets were installed in their day. And I have looked at Pioneer and Comp and found nothing.

[Joe-71]

Not implying anything but that 292-312 Y Block Ford mushroom lifters are available from a variety of sources. The Y Block lifter bore is ~.500" stock, and there is usually a .002" clearance. They have a 1.000" foot. Race mushroom lifters are another category. I use the Trend tool steel lifters in the stock length, and +.100 lengths for my Y engines. Joe-71

[Stan Weiss]

My point being that if the mushroom and bucket diameter is the same they still have the same max velocity limit. I was looking for Mike to join in because I don't know if on the bucket one might be able to use a higher acceleration.

Stan

Right, they do.

I thought this was interesting...

Here are some examples of distance from lash point to max accel, and max Vel on different cams.

Comp Cam, Pro Cup roller: Max Accel=14 deg, Max Vel=46 deg
Crane cam, 410 sprint roller: Max Accel=30 deg, Max Vel=70 deg
Schrick Cam, BMW overhead bucket: Max Accel=10 deg, Max Vel=48 deg
LSM Cam, Pro Mod roller: Max Accel=32 deg, Max Vel=78 deg
GM 604 crate cam, Hyd roller, Max Accel=27 deg, Max Vel=53 deg
Jones Cam, "Banjo"'s roller: Max Accel=17 deg, Max Vel=59 deg

I just designed a roller cam that gets to max velocity in about 10 degrees, but it's only designed to turn 2,000rpm.

These degrees are only half the story. What was max acceleration and what was max velocity for each. This is a Comp Cams SBF roller. I was sent a Cam Dr file so I do not have all of the information about the lobes.

These numbers are from the base circle. Max Accel = 33 / 0.0003462"/deg Max Vel = 48 / 0.0088375"/deg cam degree / lifter raise

These numbers are from the lash point. Max Accel = 19 / 0.0003462"/deg Max Vel = 29 / 0.0088375"/deg cam degree / lifter raise

Stan

Edited: Had mixed Crank and cam measurements together

[CamKing]

I think what I am getting at is the bucket and the mushroom lifter of the same diameter will have the same peak velocity, for obvious reasons, but the bucket can withstand higher acceleration, so it reaches peak velocity sooner (and would have more lobe area under the curve).

Not in most practical cases.

In a pushrod engine, it most cases, you can fit the spring you need to control the valvetrain, and that spring pressure is being multiplied by the rocker ratio, on the pushrod and lifter.

On a bucket follower type engine, you are limited to a spring that can fit under/inside the bucket. In most cases, this limits the amount of spring pressure you can run, and that limits the acceleration rate.

[hoffman900]

I think what I am getting at is the bucket and the mushroom lifter of the same diameter will have the same peak velocity, for obvious reasons, but the bucket can withstand higher acceleration, so it reaches peak velocity sooner (and would have more lobe area under the curve).

Not in most practical cases.

In a pushrod engine, it most cases, you can fit the spring you need to control the valvetrain, and that spring pressure is being multiplied by the rocker ratio, on the pushrod and lifter.

On a bucket follower type engine, you are limited to a spring that can fit under/inside the bucket. In most cases, this limits the amount of spring pressure you can run, and that limits the acceleration rate.

Ah, I hadn't considered what could fit.

Can we just let pneumatic "springs" be legal in every series already, then?