All about cams

US cams are made by Webcam and Megacycle. Both have hard welded lobes with a high nickel content which give excellent wear characteristics. Web cam requires that you provide a cam core which means that you are starting with a used cam and re-furbishing it.

Hardwelded Webcam below:


After hardwelding the lobes, Webcam trims the sides of the lobes with a thin grinding tool. This is a difficult job (I know - I tried it). Webcam has great customer service and they are always ready to help.

Megacycle makes their cams new out of billet steel so you don't have to provide a used cam core and this is very convenient because you don’t have to worry about using a used cam core with wear on the journals. Most of the used cams I come across have to be tossed because the journals are worn. Megacycle cams are hardwelded on the lobes - again with high nickel alloy with excellent wear characteristics.

Megacycle cam below:


Megacycle cuts a channel all around the lobe and fills it in with hard weld. This way they do not need to trim the sides of the welding. Its a neat clean process and you can see the different metal color of the lobe channel in the photo below:


Both Megacyle and Webcam use Berco type or similar cam grinders which use a "rocking table" that follow the shape of a larger master cam plate. To make the cam plate they must start with an existing cam lobe and use the original cam lobe to make their cam plate. This is why copies are not perfectly accurate and its why there are so many cams with different names that are close but not identical. The PW3 cam and a Triumph grind (and others) are all copies of each other and no one knows for sure who was the original inventor as far as I know. A master cam plate can't be made from scratch because the Berco rocking table travels on an arc and there isn't a computer program available to translate all that geometry (so I've been told).

Fortunately I know someone who makes cams on a CNC machine who can decipher the lift/duration numbers after reading them on his "Cam Doctor" or other computer program. Databases of cam profiles are available to choose from to find the cam you are looking for (usually). I've spent a lot of time manipulating the numbers to create the cams I need. This is especially important when developing improved ramps that lessen the jerk which creates unwanted valve bounce as seen on many of the older British cam grinds such as the PW3. Modern cams usually have better closing ramps that slow the lifters decent more gradually to reduce valve bounce at high RPM.

Newman cams in the UK uses a CNC machine to make their cams and they also provide new billets so you don't have to start with a used cam core (sorry but I don't have a photo of a Newman cam). They are the primary makers of the cast iron PW3 cam but they can also make cams out of Nitride hardened EN40 steel. They can make cams straight from the lift and duration numbers which is very convenient. They have made some cams for me but I have not compared the wear characteristics of nitrided EN40 to the hardwelded cams of Webcam and Megacycle. I have recently been in touch with "Nourish racing engines" and they also make their cams with nitrided EN40.

So there’s the story as I know it. I value all the cam grinders that I know and they all have their various qualities. The more I learn about cams and how they are made – the more I understand why the grinders must charge what they do to provide their product.

Many thanks - that's most interesting!

How is the scroll usually cut into the journals ? I've found a guy who has a die grinder, however it would be nice to find out the BEST way.

Very informative. Thank you.

Slick

Many years ago, I had a book about Ed Iskenderian's polycyclic cams - were they ever much good ? Megacycle cams seem to be very popular. My feeling is that in the past I did not ever get the most out of the race cams I had, due to lack of optimisation - exhaust and inlet systems as well as the actual timings used when installing the cams. I also believe that the good racing guys and the bike factories only ever sell their second-best cams to mugs such as myself.

acotrel said:

How is the scroll usually cut into the journals ? I've found a guy who has a die grinder, however it would be nice to find out the BEST way.

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Comnoz tells and shows all about it here.

https://www.youtube.com/watch?v=B5XH_CK6dj8

Great thread Jim, thanks for sharing that info & taking the time to post it. That megacycle cam sure does look nice! Cj

In the interest of completeness, we shouldn't omit Johnson Cams from the list of US suppliers, as they've got a variety of hardweld Norton offerings as well. Their grinds are created similar to Web Cam, i.e., hardweld either on your camshaft or a donor core.

It might be slightly out of the ordinary to create billet hardweld cams, but suspect it is primarily done because in flat tappet applications the hardweld alloys often provide superior wear resistance relative to certain billet alloys. Another factor worthy of consideration is economics, i.e., that by employing the tough hardweld lobe face, a heat treating cycle is circumvented along with accompanying distortion and the subsequent need to final grind the lobe following heat treatment.

Although jseng1 reported that Megacycle grinds their Norton lobes on a rocking table grinder from masters, I'm quite certain they also have a Landis CNC grinding machine capable of producing masterless grinds from a database. However, I'm sure it is not cost effective to employ an expensive machine ($0.75MM?) like this for producing a handful of Norton cams, nor that we have the need for such precision machining in our dinosaurs. CNC grinding is probably better suited to specialty or higher volume cams, e.g., NASCAR or Caterpillar cams where survival is required at extraordinarily high sustained speed or for 10's of thousands of hours at lower speeds respectively.

https://www.youtube.com/watch?v=QegFuZGJ5JI

https://www.youtube.com/watch?v=hl60zEDQbVo

No doubt our colleague SNOTZO could create a CNC databases for just about anything we'd ever want for a given Norton application, and confirm the soundness of the design via simulations. Given the plethora of Norton cams already available, and in light of Comnoz' spintron findings for several of them, I believe a path forward exists for the ambitious Nortoneer seeking custom cam profiles or performance not addressed by the cams presently available in the marketplace. That said, unless you're a really serious racer requiring extremely high rpm operation, IMHO existing cams do a very nice job of covering the large majority of our performance needs. But then again, there's always room for improvement.

acotrel said:

Many years ago, I had a book about Ed Iskenderian's polycyclic cams - were they ever much good ?

Click to expand...

Polydyne cams, computer designed, were but a passing phase as noted here....
http://www.iskycams.com/advanced-design.html

We also have to remember that many racing V8 engines use roller cam lifters,
and cam design and shape are different, to suit this...



Interesting stuff Jim.
Can't the cam journals also be metal sprayed and machined/ground back to renew them (without distorting the cam ?)

Masters for all rocking table cam grinders are covered by Prof. Gordon Blair's software 4StHead. The grinder used by Nourish Engines is a rocking table Churchill.

With all grinders, flat follower type profiles can be ground using any diameter grind wheel, but most roller or radius follower designs will usually have a negative radius as part of the profile, and this radius will determine the size of grind wheel required.

Rohan wrote:

"Can't the cam journals also be metal sprayed and machined/ground back to renew them (without distorting the cam ?)"

Or chrome plated and ground back? The journals will then outlast several bushings. This is the usual treatment on aircraft turbine vane journals.

Slick

Snotzo said:

Masters for all rocking table cam grinders are covered by Prof. Gordon Blair's software 4StHead

Click to expand...

Professor Gordon Blair designed the cam for the 500cc Norton ultra short stroke we built. Data files were emailed to Mr. James Dour of Megacycle Cams. Megacycle made the masters (presumably by CNC). Three cams were made. The engine/cam profile was good for 10,500 rpm practical redline. The 180 degree firing order was problematic for the valve train.

There appears to be bucket loads of workable cams for an 89 mm stroke Norton with near off the shelf valve train components. It is when you go beyond the rpm limits imposed by an 89 mm stroke engine (shorter stroke higher rpm) that the engines breathIng needs change and the valve train dynamics get pushed outside the envelope of pretty much any off the shelf cam that has been designed and manufactured for Nortons.

jseng1 said:

Both Megacyle and Webcam use Berco type or similar cam grinders which use a "rocking table" that follow the shape of a larger master cam plate. To make the cam plate they must start with an existing cam lobe and use the original cam lobe to make their cam plate. This is why copies are not perfectly accurate and its why there are so many cams with different names that are close but not identical. The PW3 cam and a Triumph grind (and others) are all copies of each other and no one knows for sure who was the original inventor as far as I know. A master cam plate can't be made from scratch because the Berco rocking table travels on an arc and there isn't a computer program available to translate all that geometry (so I've been told).

Click to expand...

It is possible to make a master from scratch. That's how Axtell did his cams. He designed his own profiles, drawing them out on paper and doing the math by hand (and maybe a pocket calculator), and his partner Mike Libby made the masters on a mlling machine with a rotary indexing table, cutting very tiny increments at each setting. Axtell did the math to convert the numbers from his lift curve to settings on the mill to cut the masters, point by point. I think the tiny cuts were blended into a smooth curve with a stone, but I'm not sure of all the details after so many years. Mike once explained the process to me, and said it took a lot of man hours to make one master. I don't recall what brand cam grinder he had, but it was the same rocking table design as most cam grinders at the time. He bought it surplus from a Navy facility (might have been Canadian Navy, again, I'm not sure) and rebuilt it in his shop. I saw it after he had it trucked down to his shop, and it was a massive machine. He previously had someone else grind the cams from his masters, but wanted his own grinder so he could control the quality better. They used a Stoody hardfacing rod (using oxy-acetylene torch) to build up the lobes before grinding, but I don't recall which one it was, and I think it's no longer made. He mentioned that it was critical to use the right alloy rod to be compatible with the Stellite pad on the lifters. Towards the end of their cam production, they switched to using a TIG welder to apply the hardfacing rod. The technique looked to me more like bronze welding than regular fusion welding. After grinding, the cams were hard chrome plated, and then coated with a dry film lubricant. I think they were also shot peened before chroming.

The precision of his cams was pretty impressive. I dial indicated the profile on a couple of his cams, and they were all right on. I also did the same for a copy by a local SoCal grinder, and it had a lot more variation between one lobe and another. I'm sure the grinder just made his master from an original Axtell cam. Using the larger master cam plate to grind the smaller actual lobe contributes to accuracy. In the other direction, making a larger diameter master from the smaller original lobe, and then using that to grind a cam introduces a lot of inaccuracy.

Just another stroll down memory lane. Modern cam design software has removed a lot of the black art from the process.

Ken

Dances with Shrapnel said:

The engine/cam profile was good for 10,500 rpm practical redline. The 180 degree firing order was problematic for the valve train.

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Could you please explain how/why the 180 degree firing order was problematic for the valve train? Thank you.

I wondered that too..

Presumeably it loads the chain drive to the cam differently (more unevenly).
All these offset cranks would also do the same. (?).

As for the 10,500 rpm operation - didn't the JPN racers find the alloy pushrods flexed too much for use much above 7000 rpm even.
(or whatever rpms they used).

Yes a 180 crank loads the cam very unevenly, resulting in a lot of strain on the chain etc. also increased cam flexing. All of this inevitably made much worse if the engine is built for high performance (which it almost inevitably would be) as higher rate valve springs would be employed.

Rohan and Fast Eddie touched on a few of the aspects.

Given the specific firing order of this 180 degree cam, the kinematics of the matter include LH intake opening near concurrently with the RH exhaust with only the LH exhaust closing. The 360 degree phase only has a single lobe opening at any given time so in the case of the 180 degree cam, one has doubled the load. Furthermore, the two center lobes are loaded simultaneously (LH intake closing while RH intake opening); so two lobes adjacent to the center of the cam are loaded at the same time thus increasing the bending moment of the cam beyond what is realized with a 360 degree phased cam.

So as a result of selecting a 180 degree firing order, we now have a valve train tasked with opening twice as many valves concurrently. Add to that the additional valve spring rate required for compliance. If that were not enough, the forces due to acceleration (Dynamics) increase with the square of the speed. As an example, when comparing the relative red line rpm between the 89 mm stroke and the 59.6 mm stroke the valve train forces increase by a factor of 2.25 ((10,500^2)/(7,000^2)). So with opening two valves together and the acceleration we have upwards of 4.5 times (2*2.25) greater forces in the valve train at relative redline rpm of the 59.6 mm stroke without even factoring in the increased valve spring force needed to keep things in compliance. You can see how this gets out of hand in a heart beat.

Someone mentioned the push rods being too flexible. I recall there are pictures of this particular motor floating around somewhere on the forum or elsewhere and you may see that these were very short and stout push rods so push rod flex was not a major issue, if any at all. Chromoly steel is always an option.

So, what happens, cams break, cam chains break, cam chain slack adjusters get beat to sh*t, crankshaft timing pinons fail, stellite on cam followers goes missing and cam sprocket nuts and pinion nuts get loose. Some of the remedies included a center bearing for the cam and replacing the cam chain with an all gear drive. The pinion remains a challenge but when all is said and done, IMHO, why bother - stick with a 360 crank for very high speeds. The metallurgy and means of manufacture have solved the crankshaft issues.

For those contemplating or fantasizing an alternate crank firing order, the above is something to consider. We have learned that by solving one problem we have squeezed out and gave birth to a few more problems.

I hope this helps.

Is primary balance of a Commando engine really an issue if the crank is balanced to suit the usable rev range ? There is a thing which I discussed with a friend a while back - it is about tyre recovery between motor firings. Often there is a balance to be maintained between slide and drive. - Something to think about when you are all cranked over doing 70 MPH around a corner in the rain.
I can send myself insane trying to optimise the cam to suit the inlet and exhaust system of a 360 degree motor without introducing further complication. The performance of a motor is not simply the sum of the parts used to build it.

WZ507 – Comnoz is scrolling a couple solid cams for me now. And yes, Johnson also makes cams in the US. Megacycle uses a rocking table grinder for all their British cams because they already have old school rocking table cam masters. They also told me that they heat treat the cams after the hardwelding process to give better journal wear. The hardweld rod I have tried in Nickel based, has a hardness of 60 and goes on with Oxy Acetylene.

Rohan – I’m not sure about alum pushrod flex. It depends on the alloy and I don’t remember seeing any pushrod flex on the Comnoz spintron at any RPM. Maybe he could clarify.

Texas slick & Rohan - Below is a cam journal that has been hard chromed.


Jim Door at Megacycle created the profile below. It’s an improvement on the PW3 cam. Snotzo ran a simulation with this profile and found it to rev beyond 9000 without valve bounce (not accounting for cam bending). Brooking 500 has one of these cams for BSA lifters.


Heres a layout of a billet cam core for machining I drew up. Someone has offered to make these for me but there is not enough volume demand to make it economically viable.


There's a few Landis grinders around and I know of someone with a Landis who is willing to grind cams that will rev higher without float (Many hours spent computing this data) but the price is an obstacle.

Below are some billet steels that may work well without resorting to hardwelding and they have been used successfully on some sliding lifter cams but need to be tested on brit bikes.

S7
4140
52100
carburised 8620 billet
Nitrided EN40 (Nourish cams)
A2 tool steel heat treated and hardened through to 58 –60C scale

Do any of the factory production Commando cams ever give valve float at 7000 RPM ?