Looking for a Cylindrical (barrel) cam

[gwfami]

I did a quick 3D print of a cylindrical cam to verify that it would do what I need it to do. Problem is that the 3D print is way to weak. So even though these are supposed to be very common, I can't find a manufacturer/seller anywhere (and google isn't my friend on this) that doesn't bounce back to engine camshafts.

I don't have the capabilities to machine one myself, and I don't want to have one custom machined. Anyone know of a source for these?

This should give you an idea of what I'm looking for.

and https://grabcad.com/library/barrel-cam-8

Thanks,

Greg

 

[djc]

Search using different terms. Consult a textbook on cam design to see by what more precise name the item might be known.

'Barrel cam' or 'drum cam' give good results (there is a clue in the URL of the grabCAD model).

If it is 'small', someone who is associated with racing motorbike gearboxes (I think they are called 'removable cartridge' boxes) might point you in the right direction.

 

[Jasonb]

If you have the 3D file why not get it printed in a stronger material, one of the CF filaments or metal.

With endless option sfor the shape of the groove of a "cylndrical cam" finding one off the shelf with the required shape for what you need will be very difficult.

They can be made by fitting two pieces of tube over a central core, print some guides and use those to saw and file the ends of the tube to your profile.

 

[gwfami]

Search using different terms. Consult a textbook on cam design to see by what more precise name the item might be known.

'Barrel cam' or 'drum cam' give good results (there is a clue in the URL of the grabCAD model).

If it is 'small', someone who is associated with racing motorbike gearboxes (I think they are called 'removable cartridge' boxes) might point you in the right direction.

Thanks. I figured I'd find one similar to what I need then adapt around it. "Barrel cam' or 'drum cam' give good results", yes, but not for purchase. I did dig deeper into the racing motorbike gearbox, but as they are usually blind ended they won't work.

I appreciate the help.

 

[gwfami]

If you have the 3D file why not get it printed in a stronger material, one of the CF filaments or metal.

With endless option sfor the shape of the groove of a "cylndrical cam" finding one off the shelf with the required shape for what you need will be very difficult.

They can be made by fitting two pieces of tube over a central core, print some guides and use those to saw and file the ends of the tube to your profile.

I've had small items printed in metal, too expensive for what I need, plus they need to be milled to get a decent surface finish.

"They can be made by fitting two pieces of tube over a central core, print some guides and use those to saw and file the ends of the tube to your profile.". Interesting idea. Thanks, your advice is greatly appreciated.

 

[djc]

Would it be possible to do a hybrid approach? 3D print what you want and use it as a 'master cam' to guide a router or die grinder cutting a piece of metal?

Otherwise, could you use a metal core, 3D print the sides with a wider gap for the follower and then glue on some thin steel sheet to form a more robust running surface? You could use the two halves to squeeze the metal into shape. Use multiple thin layers with staggered joints.

Perhaps use your CAD software to work out the flat development of the cam running surface and make a round (it might actually be elliptical) washer of the same shape. Then deform it to the correct shape. That would give a running surface with no joint.

 

[L98fiero]

I did a quick 3D print of a cylindrical cam to verify that it would do what I need it to do. Problem is that the 3D print is way to weak. So even though these are supposed to be very common, I can't find a manufacturer/seller anywhere (and google isn't my friend on this) that doesn't bounce back to engine camshafts.

I don't have the capabilities to machine one myself, and I don't want to have one custom machined. Anyone know of a source for these?

This should give you an idea of what I'm looking for.

and https://grabcad.com/library/barrel-cam-8

Thanks,

Greg

Those cams were made long before CNC and 3D printers, whether you can make them or not depends on how much time and effort it's worth, and how accurate it has to be, here's a video showing how to do it manually.

 

[Richard Carlstedt]

Barrel cams can be made with a simple lever relationship
I saw one maybe 60-70 years ago and now do not remember the relationship of the levers,
but you are taking a cam and putting a sine wave in it. it took 4 easy setups and did one quarter of the cam at a time and just the X axis on the mill was moved and the cam would turn due to a link arm fastened to it. The second link arm was attached to a rigid point , not on the table and I think it was attached to the mill knee or saddle , The two link arms rotated the cam.
The link arms used a aircraft bearing at the adjustable joint.

Rich

 

[timo_gross]

Barrel cams can be made with a simple lever relationship
I saw one maybe 60-70 years ago and now do not remember the relationship of the levers,
but you are taking a cam and putting a sine wave in it. it took 4 easy setups and did one quarter of the cam at a time and just the X axis on the mill was moved and the cam would turn due to a link arm fastened to it. The second link arm was attached to a rigid point , not on the table and I think it was attached to the mill knee or saddle , The two link arms rotated the cam.
The link arms used a aircraft bearing at the adjustable joint.

Rich

Wait a minute! What is an aircraft bearing? (serious question).
I would

• a) grab tube of adequate size and material
  
• b) cut tube in two halfes @ desired angle
  
  
• c) make pin that fits inside tube
• c) put tube cut-offs on pin
  
  
• d) pin/glue/weld/solder or whatever the three pieces together.

Done!? To me it looks like a usable cam. (not high precision to me, but it took me only 5 min. (3 min taking pictures and typing)

Greetings Timo

Greetings Timo

 

[Jasonb]

Thats what I said eartlier and as the OP only has a file and no mill should be possible for him to do.

"They can be made by fitting two pieces of tube over a central core, print some guides and use those to saw and file the ends of the tube to your profile."

 

[timo_gross]

Thats what I said eartlier and as the OP only has a file and no mill should be possible for him to do.

"They can be made by fitting two pieces of tube over a central core, print some guides and use those to saw and file the ends of the tube to your profile."

I admit I overlooked that. Depending on required precision I think to get something usable "is possible". Some handfiling and fitting will be required.
I am curious how the OP will solve it

 

[Richard Carlstedt]

Wait a minute! What is an aircraft bearing? (serious question).

That is what they use to call them as they were common on aircraft
Here is a pic.
Rich

 

[RM-MN]

How do those differ from Heim joints?

https://www.amazon.com/Heim-Rod-End...rCGBo60emqEEDh5fCMtM9g3xjOEaAhGwEALw_wcB&th=1

 

[L98fiero]

How do those differ from Heim joints?

They are also called rod end bearings and I've heard them called spherical rod end bearings, I guess it just depends on where you are and what industry but they are essentially all the same.

 

[djc]

• b) cut tube in two halfes @ desired angle

There is quite a lot of subtlety in cam design. In particular, a cam made like that would not have a great action. At the end of each 'stroke' it goes instantaneously from 'descending' to 'ascending'.

There's a whole lot of maths behind it, but in essence, distance is a function of time. You take the derivative of that function to get velocity and the second derivative to get acceleration. The third derivative is known as 'jerk', which is the change in acceleration with time (units metres/second^3).

See: https://en.wikipedia.org/wiki/Fourth,_fifth,_and_sixth_derivatives_of_position

It is one area of maths/physics where the names make you smile.

----

Another way to make his cam would be to draw the profile on a flat piece of paper. You make the horizontal axis of the drawing equal to the circumference of the cam. Cut it out, wrap it around the stock and draw a line. Cut and file to that line. Making the cam profile this way also gives you a visual understanding of the motion - without any of the maths above, you can assess things like 'smoothness' (sharp corners) and 'steepness'.

 

[indian]

We call them rose joints