hello from Viet Nam

[truyentu]

Warm greetings to all members. Hello, I am a new member from Vietnam, and I am very happy to be here.
I am trying to build my first engine,so i start to learning about basic concept of ICE,but this camshaft is abit hard to me
I found in this pdf file here,anyone can explain how did you make calculation for the new camshaft parameters such as : base circle,flank radius,lift... thanks so much http://www.makalesistemi.com/panel/...b5e2d4b7f8963e7535d45e7aa/37506f903036f02.pdf

 

[GreenTwin]

Welcome, glad to have you here.
I have followed several discussions here about cam profiles, and also how to build cam grinders, but I don't yet have a good understanding of the details of a cam profile.

There are some here who do understand cam profiles very well, so hopefully they will give some insight into your question.

Looks like an interesting white paper.
It will take me some time to read it.

Pat J.
.

 

[GreenTwin]

The paper mentions a line contact between the cam and the follower, and so the follower must be free to rotate, else it would get a valley worn in it.
From watching a buddy of mine build racing engines in the 1970's, he would install high-lift, high-duration cams in his racing engines (generally 454-LS6's and 427-L88's), and if I remember correctly, he sometimes had to mill the pistons to give more relief space under the valves, and had to pay close attention to head gasket thickness, to pay attention to overall compression, and also valve/piston clearance.

And I recall him using rollers on the rocker arm where the rocker meets the top of the valve stem.
The higher the lift and duration, the worse the engine would idle, but generally it would produce a lot more power at higher rpm.
Sometimes he would install double springs, one inside the other. Any valve float at high rpm would crash the valve into the piston.

Pushrods had to be very rigid to withstand the additional forces from high lift and possible high acceleration, to prevent the pushrod from deflecting.
He sometimes increased the size of the valves (I seem to recall that), and he ported and polished the passages to improve flow.
The intake and exhaust manifolds had to be sized to match any increase in size/shape and flow characteristics of the head passages.
Increase in power output seemed to decrease fuel efficiency, since there was so much valve overlap at lower rpms.
My friend had several street/track cars, where he not only drove them daily on the street, but also raced them at the 1/4 mile track on the weekends.
His 64 Corvette 454-LS6 was producing somewhere in the 550 or more horsepower, and he was getting track times in the mid 11's as I recall.
Manual 4-speed transmission; positrack rearend, racing axles and drive shaft.
If you don't strengthen the entire path of power from the engine to the rear wheels, then you find out very quickly what the weak link is.

These are a few recollections that come to mind from the 1970's, which seems like yesterday.
Now back to reading the white paper.

.

 

[GreenTwin]

The engines I design and plan on building in the future are generally on the large side of what is normally considered a model engine, and I like to design engines that can be used under load on small motive devices (scooters, etc), with a finite amount of continuous horsepower, such as 2 hp or less, and babbitt bearings for good wear characteristics.

For a model engine, often the only requirement is that the engine runs smoothly, since it may not ever be loaded.

For an engine that is designed to produce some finite continous power output, more attention must be paid to cam and valve design.
I have studied a number of small hit-and-miss engine designs, and often those engines have valve/cam designs that fall into a somewhat narrow range of dimensions.

As I recall, it is more important to open and close the valves at the correct time, than it is the actual cam design itself (others can perhaps comment on this idea).
A perfect cam design will not work well if the valve opens and closes at sub-optimal times.

And with a scale model engine, it makes little sense to design a cam that is more accurate than what can be measured physically, built, or tested performance-wise. Sort of like machining to 100,000 thou, when your instruments can only measure to 1/2 a thou.

The point of ignition is also important, and is dynamically connected to engine speed, and probably affected by cam/valve design too.

I would think that an engine intended for low-speed/high-torque applications would have a different cam/valve design than a high-speed/high performance design; so for starters select high, medium or low speed engine type.
Obviously there is not a one-size-fits-all cam/valve design, and so the design scope needs to be tailored and narrowed for the intended purpose.

Just a few thoughts.
.

 

[ShopShoe]

troyentu,

Can you tell us more about your experience and your shop?

It's always interesting to see how new members are starting out in the hobby.

--

Without any more information to guide us, it would seem that choosing to follow an existing and successful plan would be a good place to start. You would be more likely get the reward of a running engine and learn some of the things you are asking about. From there you could change the design to see how it might affect your projects.

To build on what GreenTwin has posted, study of information available in the automotive world can give you an idea of what things are done to change performanance of engines for various uses. You may want to go back a few decades to find information from the pre-emissions-control era when lots of things were done that can't be done today.

--ShopShoe

 

[Wp356]

Tru,
This is very good advice from ShopShoe. My first engine was selected before I had the knowledge, machining experience, and most importantly, the proper tools in my shop. I was fortunate to have a friend nearby to use his lathe and milling machine, as the ones I had were not accurate nor rigid enough for a successful outcome and fun experience.

 

[awake]

Welcome to the forum! I visited in Vietnam in 1974 (I think? around that time), traveling around the south visiting with missionary families. I found it to be an incredibly beautiful country, which made the devastation of war even more sad. I remember one place in particular - I don't recall the name of the area - where there was an incredible beach with the whitest, finest sand I have ever seen. And the food - absolutely delicious!

Yes, my view is probably not typical for an American, but I grew up in Southeast Asia until 1975; I was only 14-15 when we visited there. I would love to visit again!

 

[minh-thanh]

Warm greetings to all members. Hello, I am a new member from Vietnam, and I am very happy to be here.
I am trying to build my first engine,so i start to learning about basic concept of ICE,but this camshaft is abit hard to me
I found in this pdf file here,anyone can explain how did you make calculation for the new camshaft parameters such as : base circle,flank radius,lift... thanks so much http://www.makalesistemi.com/panel/...b5e2d4b7f8963e7535d45e7aa/37506f903036f02.pdf
View attachment 159505

Welcome !
Another member from Viet Nam
I have 2 options for you:
What is the purpose of learning about lobe configuration?
1 - To make a high performance engine? save fuel...bla bla...
2 - Simply make an engine and run it at a speed of a few hundred to a few thousand rpm ?? And happy, proud that you make an internal combustion engine yourself ?
For case 1: I have learned about lobes,,..calculation formulas...download...I have a whole folder for it, as a result, a few years ago I deleted the entire folder about lobes.
For case 2: Just follow the plans or rely on the plan (plan webster engine: free) and design according to your preferences
Only when you make an engine and it runs will you really know what is necessary and unnecessary
I choose case 3 from the beginning: just look at everyone's results and make the engine my way, why? What is the principle of internal combustion engine? - Compression: is the first principle, without compression, hundreds of formulas, adjustments...bla bla... it doesn't solve any problem. Good compression is my first and most important choice when making an engine
There are many other issues such as experience, understanding.....machinery, tools...
.........more....
Learning more is good, but sometimes it has the opposite effect
Some of my opinions, the choice is yours.
Again: Welcome !

 

[truyentu]

Hello everyone, I didn’t expect such a warm reception from everyone. I apologize for not clearly introducing myself or the purpose of my project. I own a mechanical machining workshop. Regarding equipment, I have a CNC lathe and milling machine, and I can design with SolidWorks as well as perform FEA with Ansys. Before asking my question, I have searched through almost all the forums here, and I’ve already gathered some initial results regarding the parameters that people often use to manufacture camshafts. These include both the specifications and the machining process. However, I don’t quite understand where these parameters come from, and that’s what I’m stuck on. I dream of building a larger engine to install in my own motorcycle, so I want to fully understand the process. Currently, I’m taking this course: (it's in Vietnamese). A major storm is happening in Vietnam at the moment... so I apologize if I take some time to reply to everyone’s comments later.