[M-man]

We got a low budget engine, that we are building, to reduce costs we were thinking of manufactoring our own inlet cams.

Would a cam with 12% more lift area on the opening side considered as agrassive cam or is it a kind one?

[NC Cams]

Your question is far to vague to give a specific answer to. For that reason, the answer is both yes and no.

IT all depends on how you plan to get 12% more area.

If you do it as a combined function of adding more lift and duration to the lobe, it might not be agressive.

IF you do it soley by adding lobe lift, the cam will surely be more agressive and, if you are velocity limited by way of tappet diameter and/or other such limitations in/of the follower mechanism, you might not even be able to do it this way.

If you do it soley by adding duration, low speed performance will suffer while similtaneously enhancing high speed power. Again, your useage and/or operating requirements will determine if this is even a viable option

If you do it by adding only rocker ratio (going from 1.5 RAR to about 1.7), the cam will stay the same but your spring and valvetrain forces and stresses will go up drastically due to the more agressive valve action the higher ratio will foster. This may or may not overtax and break something in the rest of the parts in the valvetrain.

I've yet to see anyone who's successfully made cams (especially one offs) on a DIY basis and we make cams for a livelihood. I'd highly recommend first finding an expert to grind your cams for you and then graciously take advantage of their expertise.

Surely there are folks somewhere on the Continent who can help you. You might check "Racer" magazine as a number of European cam makers advertise there.

[M-man]

Would a valvelift diagram on both the original and the new design tell anything about what to espect? There are no option of regrindig the 4 pcs of original cams,(Cost to high and I would have to buy 4 more cams) and the machining would be free if I would make my own and it wouldnt really do much if i had to make severel models to get one to work OK..

[NC Cams]

Yes, lift curves can provide a lot of insight into how a cam will perform. However, you'll need much more than the lift curve to see it what you plan to do is even viable. Things like lift curve, spring loads and rates, valve component weights, valve train design, RPM and performance goals are just a few of the things that need to be considered.

We offer these sort of consulting services as part of an engineering service or as part of a service/cam design/manufacturing package. As you might expect, we do not do these things for free as valvetrain engineering is our profession.

Let me caution you against "machining" a cam to change the lift. There is not a milling machine or lathe that I know of that can/will reshape a cam profile in a fashion suitable to both provide smooth, wear free motion. The ONLY proper way to reshape a cam lobe is by grinding and cam grinders are not something that even professional automotive machine shops posess.

Moreover, it may be possible to machine the cam cores out of billet but, most cam makers do not give out the exact specs on how to machine and/or heat treat their cam materials - it involves trade secrets which are hard to learn and quite valuable. We can't and won't explain how to make cams on message boards.

We design, grind or regrind cams all the time for our clients. Considering that the grinder cost us $80,000 and the machine that makes our masters another $60,000 or so, plus we have over 25 years experience in grinding cams for street, race and marine applications, I'd like to think that we are entitled to charge a fair price for cam grinding services. These vary depending on the engine and difficulty but prices typlically range from $250 to $500 per cam PLUS a tooling charge for the profile master or masters.

I dare say that we could professionally grind and do so correctly for a cost much less than what it would take you to learn how to do so, all things considered. Sadly, the cost to make a one off cam is not cheap. The cost to make one wrong or out of the wrong material could ultimately destroy the whole engine.

Finally, "free" machining of parts that require unique finishing and/or heat treating processes (camshafts are just such animals) is ultimately worth what you pay to have it done.

Take my advice: save your money, buy some good cores and have a pro grind your cams.

Chances are, the experience and expertise of a pro cam grinder (us or any of our competitors) will save you far more than what you plan/expect to save by doing it yourself - DIY cam grinding is something that I STRONGLY feel is a fool's errand.

[M-man]

THanks for the help you didnt provide.....´

And why do you uses masters? Why not use a modenr cnc grinder instead, and buy the way, a machine for 60 000, what old junk could be so cheap??

[NC Cams]

The attitudes displayed by low buck DIY auto enthusiasts and/or racers defies logic sometimes. The arrogance of your remark, however pretty much all but demands a reply.

First and foremost, our $60K "junk" cam grinder is a Berco RAC1500. The exact same machine can be bought new today for around $80k. We bought a good used machine about 10 years ago and have gone thru it completely to tune up some known areas where some improvement in size control and/or consistency could be affected. The efforts have served us well.

I might also add that many of the 'name' cam companies to this very day use the IDENTICAL SAME make and model cam grinder to grind cams. Companies like Crane, Comp Cams, Lunati and Ultradyne all have and use the exact same model of Berco today.

How good is the machine? We have had the opportunity to measure and inspect the lobes ground on a very high dollar CNC grinder. The exact same profile was then ground on our tuned up Berco. On Spintron and/or dyno testing, one could NOT determine the difference between the $1.5million CNC grinder generated part and the one ground by our refurbished 'junk'.

When a $60k "piece of junk" can essentially match the grind integrity of a $1.5million CNC, why should a low volume prototype shop spend hard earned money on equipment that doesn't provide good value????

As far as our design and machining integrity: in case you haven't heard, NASCAR is THE most popular and most competitive form of racing in the USA. Apparently, it must not be easy to do as a noted F1 and Indy winning driver recently started racing in the series and hasn't set the world on fire with his abilities to compete let alone win regularly.

We were and are grinding cams for NASCAR Winston and Nextel Cup engines as well as the Craftsman truck series. Our record in 'Cup is something to be proud of. We've won 3 Daytona 500's in a 4 year period and 12 of 16 restrictor plate races in the same 4 year time frame - a record unmatched in the history of the sport. We also do prototyping work for the Big 3 auto companies as well as some psuedo factory jobs for Porsche and/or Nissan. Not bad for a company aflicted with "junk" cam grinder.

I don't know what you want a person to do. Tell you it is easy to grind or make cams? Well it isn't and wishing and hoping to the contrary isn't going to change that fact.

The bottom line is this: assuming your are trying to make a cam for an OHC bucket follower engine, you can NOT machine a profile with a mill that is smooth enough to run without encountering swift and abrupt problems. How do I know? I ALREADY TRIED!!!!!!!!!!!!! And did so numerous times and ways. Moreover, I spent more money in R&D trying to doing so than you probably have budgeted for your whole damn car.

If you are trying to make a cam for a finger or roller follower, the cam loads are more severe and the need for a smooth, accurately GROUND lobe even greater.

We also looked at cutting profiles with a lathe. After all, "all you have to do is move the tool in and out in a syncronized fashion" and it should be easy to cut a lobe shape.

Well, sir, the servo technology that is affordable to the DIY'er simply isn't fast or accurate enough to generate even a moderately mild "stocker" cam profile let alone even a mildly agressive one for a performance or race motor - we tried to go down that path too as we'd hoped to retrofit some lathes so we could rough cut lobes to save machining/grinding time. Do a "lathe retrofit" search on this website and you'll see that lathe retrofits are not walks in the park by ANY stretch.

Okuma has a lathe that will do it but the lathe is soley adequate for roughing the profile - it can not/will not FINISH the profile and it is SLOW. To finish it, you still need something like a Berco or a CNC and a CNC grinder costs about 18 times MORE than a Berco.

Moreoever, the Okuma costs nearly 3 times what a "junk" Berco costs and it won't finish a cam. Interestingly, a Berco can both rough and finish grind the raw turning - slowly but it can and will do it. Not a bad capability for a piece of 'junk'.

Why use masters? Easy answer. A dedicated CNC cam grinder is not cheap or easy to setup although they run fast and well. They do a great job of spitting out piece after piece assuming that you are running the same part albeit with maybe a different profile.

However let's say you want to go from a V/8 Chevy cam to the grinding of a OHC Ford cam. The tooling setup and validation run on the only CNC grinder we'd ever consider takes between 4 and 6 hours to achieve - we can do the same setup in about 1.5 to 2. Basically, we can setup and run off the part while the CNC guy is still knocking down and setting up his machine. The cost of a CNC grinder is simply prohibitive for a small shop.

The only CNC grinder that is recognized as suitable for automotive cams in the USA is a Landis 3L. Last price I heard of for them was $1.5 million. There is another 1/4 million associated with ancillary support equipment which makes this a VERY costly investment - one I couldn't get funding for when I set out to make cams. Used ones cost nearly as much as new so it makes little sense to buy a used machine. So, I made do with the Berco and have found that I can compete in my chosen industry by properly focusing my efforts.

The key to successfully executing low budget projects is to spend money WISELY. After a lot of time spent trying to start a cam company on a low/no budget basis, I can tell you from PERSONAL EXPERIENCE that low buck cam manufacturing is a fool's errand.

If you don't do it RIGHT, chances are nearly 100% that the part you make by kluging something together will NOT work or live. The days of guys like Winfield and the other pioneers who ground cams in home shops is long over. The speeds are too high as are the resultant stresses as well as the accuracy requirements.

I reiterate the point: save your money and have a pro grind your cams for you. The alternative if you REALLY want to DIY? Beg, borrow and/or steal what you have to in order to find/buy your own cam grinder.

That is exactly what I did in order to both LEARN how to grind cams as well as to ultimately MAKE my own cams. If I and any other number of cam grinders that I know of can do exactly the same thing to make cams, why should you be deprived of the same learning experience?

If/when you can eventually figure out how to make a cam without a Berco, Van Norman, Storm Vulcan, Fortuna or any other form of true cam grinder, God bless you. When and if you do it, I'm sure you'll share your "secret" for free for all the world to see on a DIY message board. For some reason, I don't think you or anybody else will or would.

By the way, "you're welcome" for the information which you feel that I didn't share with you.

The info I did share had you chosen to assimilate and accept it was the result of nearly 20 years trying to learn, set up and finally successfully operate a cam company. Moreover, the info I did share was 1000 times more than was shared with me by my peers in the industry - peers who are notoriously stingy with ANY free information whatsoever.

[M-man]

I thougt the nc you machined your master in were the cheap junk, sorry for that.. Anyway, I`ll will try to machine my cams myself, a bit of teasting in the bench will tell the results..

[NC Cams]

For someone who knows SO little about the science and art of cam grinding and/or manufacturing, you really have a lot of nerve to criticise the advice and equipment of a member who makes them as a profession. Then again, this won't be the first, nor last time, that a "dreamer" has asked for help and failed to take heed of the well intended advice tendered. (chair)

Moreover, refering to anyone's CNC, especially one that is capable of creating masters that are comparable to that generated by a $1.5million CNC grinder, as "junk" demonstrates arrogance and a blatant lack of respect as well as a simple case of bad manners. Refering to ANYONE's product made in any fashion as "junk", especially when you've never seen or used it defies tolerance.(nuts)

EDIT: M-Man = although we do not use a Haas TM-1 to cut our masters, the program we use does create a tool path that will run perfectly on the TM-1. These machines are anything but "junk" and can be purchased, sans tooling, for about $25K to $40K fully loaded. I do not think that anyone who has/uses a TM-1 would call that a "junk" mill. Nor would a used Haas VMC (which we do use to cut our masters) and probably could be bought for $60K someplace, be considered "junk".

Finally, do you READ what your write and judge whether the posting might, just might offensive? If you do, perhaps you should rethink your word choices. If you don't, you definitely should start.

END EDIT
I do hope that my above diatribe, when read carefully and taken to heart, will prove beneficial to your endeavors - there is more information there than I think you realized/comprehend, especially when it comes to the DIY cam grinding part.

[LongRat]

M-man, good luck with your endeavour. Please post some pics of your cams/engine when you can!
NC Cams, I have a question for your expertise. I have done quite a bit of grinding over the last few years of zirconium oxide ceramic material. Recently I have been researching making a model engine from plans, but I am still undecided as to what as yet. Anyway I was wondering about the feasibility of making a solid zirconia camshaft for such an engine. Bear in mind it would not be of the super accurate, high performance variety that your outfit produces but more along the lines of most model engine cams, i.e. open at the right time style. I am sure the wear resistance would be excellent (any followers would have to be zirconia too I'd guess), as this material is used for abrasive pump parts and production wire guides etc for this very reason. It is also pretty hard (about 1300 HV). Thermal expansion similar to steel. The main reasons for trying it would be the possible longevity, fun of trying and to say "look, I have a ceramic cam!"
What sort of problems can you forsee with this? I'd be very interested in your views. I enjoy reading your posts and certainly feel that I have learnt a lot (time will tell..)

Cheers

[NC Cams]

Re: grinding zirconia oxide - While I can not speak from experience with regard to grinding zirconia, I can speak with a degree of expertise with regard to grinding hard face materials (chromiun-nickle-boride aka "stellite") as well as some special high alloy tool steels that have nickel, cobalt and/or other very hard alloys.

First and foremost, it takes more than "HARDNESS" to prevent wear in cams and followers. The tribological properties of the materials often has as much to do with wear properties/resistance as pure and simple hardness.

Memo to M-man: pay attention, the following info MAY pertain to you and is IMPOSSIBLE to learn via DIY bench testing.

Example: Chilled iron is essentially "white", very high carbide iron. It is commonly used in European and Japanes OHC engines. It develops its hardness and wear resistance (carbide structure) via the material constituents and, more importantly, the casting technique. The technigue involves pouring the metal in a way so that the lobe area "chills" (hardens very very rapidly) and creates a carbide structure in the process.

The iron is very hard and quite wear resistant. HOWEVER, it is not a "tough" material. That is, it can not be highly stressed as the material is hard to the point of brittleness. Thus, you have to be VERY careful of the stresses applied and the life of the part. Any time you increase the stress signifigantly, the fatigue life drops quickly.

Hardenable gray iron: whereas the European and Japanese makers used chilled iron, the North American car companies jointly developed an alloy in the 1950s for their flat tappet cams called hardenable gray iron (trade named as Proferal).

Instead of low alloy iron poured to chill, the N/A's took and added alloying eleements such as chrome, nickle, tungsten and other agents to the iron. They then poured it into sand molds and did NOT force chill the iron. Once the iron cooled, they then flame hardened the lobes followed by oven tempering.

The result was a much deeper hardness. Moreover, the iron was basically carbide in stucture BUT it also had pockets of flaked graphite distributed thru the alloy. The hardening did what it was supposed to do but the subsequent tempering drastically raised the toughness of the part. The stress levels that this material can run and live at is FAR, FAR superiour to chilled iron. Moreover, the graphite supported in the tempered structure made the iron both wear and scuff resistant.

Proferal will run and live at stresses that would kill chilled iron. THis was one reason why the heavy valvetrains in the pushrod engines were able to live - superiour metallurgy that was NOT soley reliant on hard, brittle material to prevent wear.

The common problem of grinding/finishing ANY pre-hardened material is to cut the material without damaging (burning especially) the parent metal. A google of "grinder burns" will give incite into what's going on and why. The issue as to whether or not the zirconium would be viable for a cam depends on:

a: can you even grind/finish it? (probably the biggest hurdle)
b: will it carry/survive the loads?
c: is it financially worthwhile to even use the material?
d: is there a related material that can/will survive while rubbing against the zirconium and do so under ALL extremes of service?

I know of some ceramic materials that were used to make valves and cam followers. They were hard, very wear resistant materials that you could NOT hurt in bench wear tests. Yet they failed almost immediately in engine use.

Why?

They couldn't survive ALL of the conditions that the parts must withstand not the least of which were low speed cranking (scuffed the hell out of the parts due to lube ruptures that are "normal"), random overspeed bounce/float (overspeed at gear change or downshift) plus a lot of other "issues" that were not readily apparent to the parts inventors.

ALL and I do mean ALL of the material properties MUST be considered when selecting the alloys to use to make engine parts. The IC engine has a history of using up and spitting out materials that "should work beyond anyone's dreams". That was a lesson that my former employer learned when they tried to introduce ceramic coated piston rings to the industry almost 20 years ago.

It worked GREAT on the dyno and in the lab. Give it to the general public and/or the know it all racers and DISASTER.

The point is, and I can't/won't argue the point, that there may be some tremendous satisfaction in creating the first zirconium camshaft. The question is, however, is this exotic material REALLY needed? Or can/will some other, more reasonably priced material do a better job? Especially under the extreme, abusive conditions that can befall the lowely cam to lobe interface.

How abusive? The roller cams are operating at stress levels at or above the yield points of even the best materials. Race cams that used to last a whole season now have a tough time living 200 miles. In NASCAR, we used to use select grade, special castings to make the cams. Anymore, cams made of tool steel billets are the ONLY thing that will survive. In light of prior "issues" with exotic materials, the rules makeres have stipulated that only STEEL followers be used.

Don't even mention F1. Why? The last I heard, F1 was using valve lifts of 11 or 12 mm. We run that much lift at the cam and THEN put 1.7 to 2.5 rocker arm multiplication on top of that - worse yet, the drag racers run 12 to 13mm of cam lift and also put 1.8 to 2.0 rockers on top of that.

Jokingly, I once said that we run more valve lift than F1 runs stroke in their engines. Come to think of it, that snide remark probably isn't far from the truth.

I won't deny that there may be a desire for a zirconium cam - I just would question the need for it and how you'd go about grinding it. I know what it takes to get the custom wheels we need for our tool steel - I'd hate to see and pay what it would take to come up with wheels to finish zirconium.....

[HuFlungDung]

Interesting stuff, NC Cams, thanks for writing about it.

Even though I'm not an engine geek, I'm still interested and intrigued by all the details that go into making the parts.

[LongRat]

Thanks for your full answer NC.
You make some good points there about extremes of use. One thing this material would be vulnerable to would be heavy impacts, I would expect (I have worked with zirconia a lot). It's abrasive wear resistance based on a combination of harness, tensile strength and toughness is superb, and it is probably the least 'brittle' monolithic ceramic there is. However the fracture toughness is still many times lower than steels.
It is possible to precisely grind zirconia using diamond abrasive wheels, although of course the home workshop is another issue altogether. It is used in a lot of medical devices, such as hip and knee implants, where there are several areas on the parts that require tight tolerances and extremely fine surface finishes. As for obtaining the material.. for a small model engine offcuts of material would be easy enough for me to procure, for a full size cam though... I'm not sure that there are any manufacturers worldwide that could make a stable blank of the required size.

[NC Cams]

AT one time, they used a titanium alloy (Howmet Metals, I visited their plant just out of college) for hip EDIT pivots (was sockets) END EDIT. At the time, it was the most innert material available that would survive unchallenged in the body. They've since found that ceramic alloys are much better suited due to wear and innertness.

Hard, wear resistant for body loads/stresses/surface velocities is NOT anywhere's near the same as those encountered in a lowly automotive camshaft application.

EDIT We use diamond, ceramic and various silicon carbide and/or aluminum oxides to grind cams. Some of the Landis machines use CBN. Our machine is too small and not properly fitted to use CBN. Again, just because it is hard, that does not mean it is suitable to use as a cam material. END EDIT

For example, surface velocity: even the fastest runner has relative low rubbing velocity between/at the body joint interface. In automotive cams, we've actually seen cases where the surface velocity has gotten so high the that lube film not only ruptures but momentarily boils/burns at the contact point. I doubt that the lube film in the body would be as hard pressed to survive.

Stress: there are two points of maximum stress in a cam. The first occurs at cranking. Reason: very low speed, very high unit loads (at the nose due to spring loads) in concert with very low potential for lubrication film creation/development. This is where (the nose at cranking) some of the most severe and rapid damage occurs to a cam lobe and/or follower.

The second point of max loading occurs at max speed BUT not at the nose. Rather, it occurs at the point on the lobe where maximum accelaration occurs.

To move something you have to accelerate it and to stop it you have to decelerate it. You have to do both to control the valvetrain. At max speed, the acceleration force is maximized at a point on the flank/side of the lobe. THis point is dependant on and by the lobe profile itself.

Max deceleration is ALWAYS at or near the nose, but the spring provides the reactive force there in response to the inertia generated by the cam. At max speed, the NET force at the nose is quite low - yes, "valve float" occurs at the nose which means that, at max speed, the force at the nose of the cam is quite low to non-existant.

The valve spring loads are simply repetitive and depend on spring geometry. However, the accelaration forces increase with speed and the weight of the valvetrain assembly. Thus, although the accel forces are quite low (almost irrelevant at cranking), they become SUBSTANTIAL at peak RPM.

Example: the intertia force of a 750 gram static weigh valvetrain increases from relatively inconsequetial during cranking to well in excess of 1200 POUNDS force applied at each lobe at 8500+ rpm. Some drag race stuff generates well in excess of 1500 lbs force at the lobe interface at the max accel point.

Depending on the geometries involved, these forces EASILY generate stresses that meet or exceed 190~200ksi. I'll let one of our European members do the math to com up with the metric equivalence in Kpa - I can't find my metric converter program. Very, very few materials will survive these repetitive loads without yielding and/or scuffing. Add the occasional over rev and you then have to add random impact loading that also has to be survived.

It should be no small wonder why the designers/developers of ceramic lifters and valves could not figure out why their hard, wear resistant material wouldn't/couldn't work in the lowly, archaic IC engine - especially if they had any clue about ALL the tribological characteristis of their "super material".

If you read between the lines above, it should not be hard to figure out why some of the special coatings that are being applied to some parts are not the end all, be all to the wear/failure problems that guys have even with "super alloys".

It isn't the technology, it IS in the FULL and PROPER execution of the details

[LongRat]

Being in Europe myself (UK) I did the conversion:

200 000 pounds per square inch = 1 378 951.46 kilopascals

Useful converter - Google (type "200000 psi in kPa") or in fact any other unit conversion you need.

Indeed those are some pretty high pressures!
I wonder if one reason full ceramic cams have not worked may be because of the difficulties of making the high performance engineering ceramics in large enough, flaw free blanks. Due to the fact that ceramics will fail from surface/internal flaws, the failure probability vastly increases with part volume and surface area. Small 'model' camshafts may not suffer in this respect.
Also, producing a solid ceramic part rather than a coated metal one does have the advantage that you are not covering a low modulus substrate with a very stiff 'shell', and the consequent likelihood of cracking and other damage. I believe cutting tool manufacturers have done a great deal of work in this area, and have an extremely good understanding of the tribology involved.
I do agree with you about the relative harshness of the bio implant environment w.r.t. that of a cam. However, I would not be so sure about the wire guide application. These see very high surface velocity and pressures, although I couldn't quote you any numbers.
As I said before, I believe impact damage may be the killer for ceramic valvetrain parts. Interesting about the force and dynamics on the cam lobes... I expect when the valves float, the follower could possibly crash back down onto the cam at a point from the nose dependent on the speed of the camshaft at the time. This impact could be damaging. Does this happen or is valve float only ever limited to the point of the force just going to zero on the nose?

[justlesh]

In the spirit of this site,( I.C. Engines, discuss HOME MADE engines), a lot of us realize there are complexities in manufacturing cams that we don't understand but are still looking for advice in making one for our models or projects without having to take enginering courses or having someone else design or make it for us. I myself like some others have built homemade cam grinders to copy profiles. I did this for kart cams, wanted to mix and match profiles from different I. and O. grinds. I know there is a lot of builders out there getting by with had formed profiles and I bet the smile on their faces is big when that thing comes to life for the first time. I for one would welcome any and all advice when it comes to design parameters of cams for model IC engines. NC Cams makes excellent arguments that it can't be done totally correct by an individual using simple machine tools but it can be done with functionality. I know when I finish my model V-8 it will run. Not being arogant, I just have faith in my abilities as do many people on this site. How about giving up some basics such as camshaft mal't versus lifter mat'l and their corresponding wear properties. Percentages of lift per degrees of camshaft rotation comparied to total lift, I know this is ever changing throughout the entire lift but maybe some guidlines or do's and dont's. NC Cams appears to be the most knowledgeable guy here, can you give us some useful advise on basic guidelines to perform the tasks we have taken upon ourselfs. My outtake on this is, If your out for maximum power, go to NC Cams or the supplier of your choice, If your after that personal satisfaction, well, show the guys that know respect and maybe we can get quality info for our own designs. I for one would love to have NC Cams design my profile but this does not match the parameters or goals I have set for this project.
Little side note, ever piss an old mechanic or tool maker off and try to get information off him, you would have more luck having good lovings from a porcupine. What do you say NC? got anything for us

[M-man]

I ve already machined a lobe with good results.. THe cams are designed with exchangable lobes, so the machining of lobes are done fairly easy and 1.5h to make a new set of lobes, so there are not so important to get a 100% working lobe at the first time.....


Anyway, we have messured the original cam, added 0.5mm to max lift, 1.27mm lift will be reached 24 engine degrees earlier then the orginial, this we have no clue if it is going to work, the closing side we didnt touch, coz we were not sure how much we could change before the vavle would "bounce". Totaly there are 12% bigger lift area, and we will se if low or high speed will suffer/ get better.. And yes, we will heat threat this proper....

It is the INLET cams we are trying to change first.

[NC Cams]

The "guidelines" for what can be tolerated are purely and solely a function of the geometry of the followers (how much velocity you can tolerate) and the stress that can be tolerated before you start to hurt stuff.

These limits are all pretty much matematically deriveable once you have the component geometries (these are different for each an every engine). The materials, on the other hand, determine what stresses can be tolerated. These too vary from engine to engine.

The interaction between the cam and follower materials will determine if/whether the stuff will slide or roll against the adjoining member without galling or spalling or cracking. In light of the tremendous variety of materials that are or can be used, it is simply impossible to give a rule of thumb guide. THe prior post on chilled iron versus Proferal illustrates some of the issues that need to be considered.

Over the years, the SAE montly magazine has published a number of articles that explains the hows and whys of the more/most common production cam materials. The society has also published a number of SAE papers that provide tremendous insight into materials.

The folowing SAE papers might be very helpful to folks who really want to delve into the subject to learn what works:

SAE #472 SAE # 710545 SAE #750865 SAE # 770019

The SAE handbook also has a section devoted to camshafts, in which materials typically used are/were outlined. The use of tool steels is NOT covered in any manuals that I know of - at this point in the development process, it is purely a racer market material and anybody who makes tool steel guards the processing as a trade secret.

If you want to learn how to design cams, there was a group of 3 articles published in the early 1950's (1953 I think) that outlined the polydyne method of cam design. The article was writen by T. Thoren, H Engemann and D. Stoddart and was published in Machine Design. Although the polydyne, method ultimately had some dynammic deficiencies that were hard/imposible to overcome, the foundation of the method uses a 4th or 5th order polynomial to generate some very smooth, continuous and powerful cam profiles - once you learn how to use the process.

To learn "rules of thumb", the standard practice is to gain access to used cams, read them with a precision measuring machine and reverse engineer the profile to see what's going on. Do that, oh 2 to 300 times over a 20+ year period like we did and, after a while, you can start to "see" whats going on and why. If you have a backgound in dynamics and/or statics, you can then superimpose on the cam the valvetrain inertia and spring forces and "see" much more.

To some extent, virtually if not all of the polynomial based cam designe programs that are in use to day ALL evolved from the Machine Design article which is/was the seminal work when it cam to scientific design of cams.

Functioning versions of polynomial based program can be purchased here:

http://www.andrews-products.com/cam_design/index.htm

or here

http://www.profblairandassociates.co...ucts_Main.html

Before you call to do a lot of tire kicking, the firms are in the business of SELLING software to design and/or make cams - the software is NOT CHEAP, so sissies and low buck, no budget programs need NOT apply.

The software works very well PROVIDING the user learn how to fully and properly manipulate it. If you don't understand the basics of calculus, and especially derivatives and/or the F=MA part of statics, you need not bother as hunt and pecking will not let you stumble onto a viable cam design. Design a cam you will but they may not be any better than some bench ground, jack hammer effort.

JUSTLESH: the old fashion "cut and try" method is how a lot of the hot rod cam company's created cams - especially in the late 50's/early 60's. They made something and sold it - the clients did the in-field testing/R&D. The "designer" initially added a little bit to the nose or to duration, usually in proportion on both the opening and closing (an early program called ADDON did the deed). The trouble is/was that if you didn't know what the velocity limitations were for your particular lifter type and size, you could run the cam out from underneath the lobe and fail the parts almost immediately.

In fact, this happened when one "hack and slash" so-called "designer" took a profile from a 0.904" diameter tappet Chrysler engine that ran quite well and "adapted" (copied it verbatim) it to a Chevy engine that only had 0.842" tappets. Damn near every cam failed and nobody could figure out why. DUH, do the math and it was obvious - tappet wasn't big enough. Don't do it and you run the risk of looking really, really stupid - and worse yet, not knowing why.

The method for "redesigning" a cam as outlined in posting #16 is about as dangerous and irresponsible a method as one can use.

Why?

Because you really must/should look at the WHOLE event (opening and closing) in order to properly and fully maintain control over the follower system. Would you add 200 hp under the hood of a car and NOT improve the brakes? No, so why would you open faster and higher and not do something to try to balance out the closing event?

I know of a case where an OEM "designer" did just this. The cam made power and broke every part in the valvetrain - the embarrasing part is/was that the manager couldn't figure out why even though the acceleration curve was clearly jerky and discontinuous. And the guys who did the work were supposedly "experts".

Do something radical or different or untoward on the opening side of the cam, you really and properly need to "balance the forces" on the closing side. Othewise, you could end up bouncing and or beating stuff all over hell and lose control.

Or, you could try to open the follower too fast and run the lobe out from underneath the follower. It might run on the bench but as speed ncreases (see prior post regarding peak accelerations), you could have the lobe eat the follower.

Worse yet, depending on how you harmonically excite the valvetrain with some herky jerky motion, the follower can send the spring into a slinky bounce-like resonance that will beat the hell out of everything even if you don't break or wear out stuff right away once you come up to speed.

Again, the 1950's method of "hack and slash" cam grinding/designing/redesigning does resurface when an untrained, inexperienced beginner grinds/makes/designs a cam that has NOT even had a cursory analysis done to even see if the damn thing is even technically viable.

This was a problem with the Polydyne stuff and a lot of the high speed and OHV cams that were made in the 1950's. Back in the day, they designed cams with protractors and french curves. The polydyne did some dynamic analysis BUT it tended to input some violent jerk into the system. Depending on the resonance of the V/T, the dynamics were/could be attrocious, especially at the critical excitation point.

This is why the Polydyne was conceived - to be able to dynamically predict if the cam would be a puppy or a parts breaker. ALthough the "dyne" part didn't quite work as planned, the "polynomial part" was a godsend and the industry has never looked back longingly for the protractor and straight edge days since.

The OEM's learned how to avoid these "hack and slash" problems with expensive dyno and/or bench testing. When widespread Spintron use became available to the racers about 5-7 years ago, the racers actually developed capabilities that matched and in some cases surpassed the OEM's when it came to understanding high speed valvetrain dynamics.

This is why pushrod engines now regularly and with relative ease can turn 8500+ rpm. THis is also why the pro's turn 9400 and don't have stuff blowing up all over the place. Frankly, the pro's have less problems and run higher and harder RPM's than the hobbist and have less problems.

Why?

Because they ENGINEER or pay guys like us to engineer the valvetrains for them - they don't SWAG something and see what the hell will happen when they set fire to it, not anymore anyway, not the good and not even the average teams.

Yes, small micro engines can be made to run with pretty much anything. Usually because the forces are small in proportion to the size of the parts. However as you scale things up, forces and stresses go up disproportionately faster and higher. So do the costs and, even faster, the cost of failure.

Perhaps the worst analysis that any cam designer can give to his effort is to say "I don't know" to any of the critical design factors.

If you don't know what the critical design factors are that need to be followed, the above SAE papers as well as as Heywood's "I-C Engine Fundamentals" book provides bibliographical insight into readings that WILL give better insight into the process.

[NC Cams]

RE: valve float and impacting from same.

Yes, float is normally confined to the area at/around the nose. However, there is a recent development wherein the engine builder "lofts" (intentionally floats) the valve over the cam nose. When done properly the system never knows that it has separated. You toss, you loft, you land you DON"T bounce. It is done as smooth as glass.

However, this is very difficult to do and must be done in concert with a lot of bench testing. The only device capable of recording the data needed to "loft" a valvetrain is the Spintron. This device measures low and high speed valve motion and everything inbetween. A proper match of parts will make glass smooth valve motion. A hodge podge WILL result in herky jerky motion and unbelieveable valve bounce (and usually damage or failure), no matter what you do.

HINT: more spring will NOT always cure the problem - sometimes, it makes it WORSE.

With proper component integration, unbelieveably high and stable valve speeds and lifts can be attained and maintained. Done improperly, you'll break stuff so fast you're head will spin and your bank account drained.

The first Spintron trace I was given access to did more to show me what NOT do do with regard to designing cams than all of the SAE papers that I've collected and accumulated over the years.

Moreover, the Spintron showed very quickly that a lot of the "car magazine" technology that I grew up worshiping as gospel was not necessarily the best nor the right thing to do.

Frankly, the spintron made me go back and brush up on the mechanics and dynamics and calculus courses that I hated so much. However, I now had a purpose for re-learning it and, from doing so, got even better at designing some very radical cams that served client well in Craftsman Truck and NASCAR "Cup racing.

After seeing what even a cursory amount of analysis can and will do for valvetrain dynamics, I find myself avoiding involvement with racers who simply want a "catalog grind" cam. Since we don't have "catalog grinds", we urge them to call a name grinder as, most of the time, the "catalog grinds are more than adequate for their needs.

However, when they are up against the rev limiter and still are getting outrevved by 3-500 rpm by the competition, that's where we can usually help.

IN closing, the reference materials cited in this and my prior posts were more of a road map than I had when I started on my quest for "cam design" how-to's. The search for the data is/was part of the fun and half the challenge of learning how to design cams. The rest was gained over time, via spending money and spending even more time researching and reverse engineering cams and/or cam design books/articles whenever possible....

[M-man]

I ll post some pics of profiles later today..

[LongRat]

Spintron looks like an impressive piece of equipment.
Thanks for the info on 'intentional floating'. For ceramic model camshaft parts, I think I would just play it safe and stay away from speeds and profiles that could cause floating.
Look forward to seeing the pics M-man.