Rollers on a Track

[Anonymous]

I've been working on a side project lately to test out the functionality of an engine design I came up with some years ago. It involves rollers following a curved track. The rollers are attached to a swivel head which is attached to a connecting rod which is intended to connect to a piston, however, I haven't added those parts because I am just testing out the roller/track aspect first and I am finding trouble getting the component assembly to function with all the added joints and what not.

I would add some pictures to help with the understanding of the model but the forum appears to be having problems and is broke down to a text based format and is too confusing to figure out how to add a photo.

So just imagine there is a slightly ellipse shaped circle that has been extruded outwards by 4 inches. The Ellipse is attached to a circular wheel which attaches to a shaft that is connected to a bearing housing acting as a revolution joint. Then on the top and bottom of the 1 inch thick ellipse track are placed two rollers with a bit of space between everything to allow some slack in the movements. Then the two rollers are attached to two pins on which to roll on, here a revolution joint is added for each roller. The pins are attached to a head assembly which is also put on a revolution joint. Finally a connecting rod is attached with a revolution joint on the swiveling head assembly, containing the inner and outer roller wheels.

Now one would think that when you rotate the entire assembly, the rollers would follow the track and cause the connecting rod to move up and down as it traverses the ellipse track line. However, the program seems to fail at accomplishing this feat. When I rotate the ellipse it binds and sends the connecting rod flying up or down inside its slider joint.

I might add that I added contact sets and made a new contact set for both rollers and the tracks, and even one roller and the track, but either way, it fails to animate properly.

I don't know if my computer is lacking the computational abilities required for a task like this or if the programs is not quite designed to handle these kinds of mechanical circumstances.

I would appreciate if someone could demonstrate that it is actually possible to get a roller system to follow a track, preferably a circular track with some changes in the diameter of the circular tracks.

If someone could show me how to do this and supply the steps involved in making it happen that would be great.

Maybe a video showing the model in action as well? Or some pictures that would be great.

The forum seems to be under construction at this point, so I understand if you have troubles as well getting back to me about this with things like pictures and video added.

Maybe I should start simple and just work with a horizontal track that has some bends in it to move the connecting rod up and down as the rollers follow the tracks. The circular part of the model seems to be giving the program some troubles making the accurate calculations to represent realistic mechanical function.

Sorry, I did add some pictures by using the part below that say add attachments, so I hope that works.

Thanks.

[TrippyLighting]

Forget contact sets. Really quickly!

They are a huge performance hog and often interfere with normal joints, which is why the often don't work.

What can possibly work is a motion link or a motion study.

[Anonymous]

Thanks for the reply and the tips. However, the main focus is to actually
utilize the joints available to test the functionality of the engine design
idea's using simulation software such as Fusion 360 provides.

>From what I understand about motion links and motion studies is that the
movement of the components instructed to move will not be doing so in
relation to other contact points and joints involved in the system of the
engine model design. In other words it would be like faking the engine to
work, when I really don't know exactly how everything is going to perform
under continuous rotation or operation. Of course, the only definitive way
to find out how well something like an engine works is to build the real
thing and test it. However, I believe that if I utilize the correct joints
with the optimal engine design configuration, I will be able to determine
with a greater degree of certainty how well the engine would perform under
real world circumstances, and that is the main point to modeling the engine
on Fusion 360.

I understand after learning from your suggestions that I can manipulate the
components to make it look like its functioning, but it isn't necessarily
simulating the realities within the functions of the engine design and that
is something I don't want to skip over because, for example, when I first
began the engine design model on Fusion 360, I found out that the two
rollers needed to be attached to some kind of swivel to prevent binding
issues when the angle of the roller track (the camshaft style crankshaft)
became too steep, an issue I never foresaw to any degree prior to running a
contact set style simulation, and was very important to learn in order to
determine whether or not the engine design is possible or not.

I have done some further studying about Fusion 360 and I am now hoping that
if I use a "Planar Joint" for the idealistic rollers that follow the cam
lobe style track, I might be able to have a functioning contact set that
functions as intended based on the engine design.

Therefore, I am going to pursue this option and try some different systems
for the, cam lobe track, and see if I can get it to simulate realistic
function with those joints and various involved contact sets.

If I cannot manage to get the engine design model to operate/animate
properly, then I think I just may take you up on your ideas to skip contact
sets all together and just implement the motion links and emulate the basic
function of the design.

In my mind I know the engine design will work, its just a matter of
deciphering which configuration and versions is the most optimal based on
categories such as, durability, strength, efficiency, power, adaptability,
structure, and dependability. Fusion 360 is helping me do just that, and I
really don't mind if other collaborate on the engine design and help come
up with the best solutions to the existing problems by participating in the
design and testing process. I'm not currently pursuing a patent on this
design because it still needs a proof of concept, so anyone is welcome to
tackle the design.

The design is unique in that, like a radial engine design it can have a lot
of pistons/cylinders surrounding the central camshaft-crankshaft, such as
24 pistons/cylinders in larger scale designs, and remember the thickness of
the engine is only 3 to 6 inches, therefore the engines can be stacked
together to create phenomenal power outputs in a compact lightweight
design. So in certain applications and configurations, the design could
produce extensive fuel efficiency while still maintaining high power
output. Yet, yes, it is somewhat theoretical, I'm just stating what I know
from experience with engines in general.

Well I better get to it then. Good day. Thanks again.

[TrippyLighting]

The planar joint is not going to work for a cam operation.

In fact, CAM operations are a very weak spot in Fusion 360.

[Anonymous]

We should clarify what we mean by "CAM". The type of cam I am referring to
is the camshaft of an engine. It has cam lobes, cam bearings, and a cam
shaft. I use this term because of the oblong shape to a cam lobe. I'm sure
your familiar with the camshaft of an engine. I think, as far as I can
tell, you are referring to the use of the word cam as the "CAM" mode of
software for instructing machining tools to carve out designs in blocks of
metal. This is not the cam I'm meaning.


Secondly, the planar joint idea came from this video here that clearly
demonstrates that a roller type of object can follow a curved track or slot
when a planar joint is applied and the necessary contact sets are put into
place. This video here:

https://www.youtube.com/watch?v=NvDBC-44uok

[davebYYPCU]

You can read what Trippy said, as ... CAM follower operations .... to take on what he meant.

The pics you supplied make it hard to advise, but your linked video was fine for the demo he is teaching, two components and one Joint, contact set, all good, your model had more parts than that demo.

I am confident you will Animate your parts, but in the stage you are at, which bit is grounded?

Hidden for clarity?  A Revolute and Slider Joint with a motion link will Animate those parts I can see, when you have the stationary bits to relate to.

Might help...

[TrippyLighting]

No "we" don't have to clarify what you meant with CAM. It took me just a brief look to understand what you are trying to achieve, it's not really that complicated 😉

I've been a mechatronis engineer for some 27 years and was a certified German industrial mechanic before going to college. I've started using CAD and 3D modeling software in college almost 30 years ago and Fusion 360 is really only one of the tools I use currently. 

I've also logged a couple of thousand hours just helping users like you here on the forum and have logged another couple of thousand hours in my own and my clients work. I've analyzed hundreds of Fusion 360 assemblies, from noob to pros, from simple to complex with hundreds of components.

When I tell you that the planar joint and contact sets don't work then that is based on that experience. You might want to take note that the "assembly" in that video has a grand total of 2 components. Yes, with 2 components  contact sets might work, but I've seen them failing in situations with only a hand full of components.

Once a design gets more complex with more joints and that is naturally going to happen in yours contact sets will fail.

[chrisplyler]

He's talking about a cam in the context of your needing a Joint that will follow an elipse or any other curved surface that is more complex than a simple circle or arc. Fusion 360 does not have such a Joint.

I love Fusion 360. But like a young woman loves her young man, I love it for what I think it can become. Right now it's got some shortcomings.

[ToddHarris7556]

Just building on what @TrippyLighting already offered re: contact sets:

I've been using mostly Inventor Professional for the last 15 of my 30-odd years designing. A lot of that has involved machine design, but also rigging studies (i.e. how to move that 90-ton reactor vessel into place without hitting structural steel or piping), ergonomic optimization, kinetic art and interactive exhibit usability studies. 

Contact sets can very very useful, but within very narrow constraints, as Peter suggested. They're great when you need to isolate a couple of parts and watch how they interact as you drag them around. When it's more that a couple of parts, though, the computational load can become obscenely huge very quickly. Combine contact sets with other constraints, and you get very scary math. It's not just the amount of number-crunching that's an issue, it's fundamental precedence/priority. In physics, solving for two-body equations is pretty easy. Add a third one, and everything falls apart mathematically. Add 10, and it becomes surreal. 

In practical terms, we run pretty powerful workstations here, and I would would only use contact sets very sparingly to look at isolated issues in your engine. Try to turn the entire assembly into a contact set, and I wouldn't expect it to work, never mind in a 'usable' sense. 

My .02 worth.

[dieselguy65 · Accepted solution]

that works, in that simple model.

as soon as the model gets more complicated, it will fail, or bog down the work to the point of being unuseable

as Trippy said, forget contact sets.

i have tried them, and been advised against it for all but the simplest models.

i have since learned to take his advice, as he is one of the more knowledgable contributors here.

[Anonymous]

I would like to report that I tried using the "Planar Joint" for the
sliding part of the engine and while using contact sets to make the
movement realistic, it worked perfectly! I am really pumped that it works
so smoothly. I don't have to rotate the moving parts in the model slowly
with the mouse. I can just hit "Animate Model" in the joints list and it
animates smoothly without any glitches.

Now I can move on to adding pistons and cylinders (possibly valves if I
make it a 4-stroke engine) and then surround the crankshaft with as many
pistons/cylinders as possible to complete the engine design. If it still
functions smoothly when animating I will record the animation and upload it
and link it to this topic to show the engine design working.

Thanks for everyone's input. I think the problem I had was solved.

[TrippyLighting]

The problem you have is that you aren’t listening and evidently that isn’t solved.

Good luck in your further endeavours, however. You’ll need it.

[Anonymous]

I haven't had a chance to respond to everyone's reply yet.

I believe I mentioned the forum is all corrupted for me right now. When I
go to the forums it loads up a hundred blue links all stack on top of one
another.

Therefore, when I am trying to read the responses on my topic, I am having
trouble loading them all up, so bare with me I'm trying to figure it out.

I certainly respect the ideas and thoughts that I have been fortunate
enough to read and I have learned a lot from those posts I've been able to
get through so far (I remember the forum was a colorful graphical interface
type of tool. Certainly Fusion 360 wouldn't have a text/code based forum
structure when everything else is so well made.)

I've listened very well, so I don't know why you make this accusation. I
said clearly that I understand there is different methods that can be
applied to accomplish the same functionality with the engine as opposed to
using contact sets.

However, I wanted to find a way to make it work with joints and contact
sets because I need to make some kind of assessment that the design is not
somehow flawed, and what I've also learned is that the joints/contact sets
have been able to show me that there is in fact a way to make the engine
design function. Now certainly, now that I have been able to make that
simulated assessment, using contact sets, I will feel more comfortable
using something like a motion link to make the animation smoother and more
reliable. However, as you can see I didn't want to skip directly to a
motion-link because I wanted to take advantage of the software and have it
look for problems I may have looked over or missed. With that being said, I
DID find some problems that needed fixing not just for the sake of using
contact sets, but also, fundamentally in respect to the engine design,
because there are a few different ways to design and model the parts,
features, and characteristics. I find there to be an optimum realistic
design that would work best in real world application, that Fusion 360
seems incapable of testing using contact sets, then there is an optimum
virtual design that seems to work best for Fusion 360 applying joints and
contact sets.

So far, I have built a cylinder/piston cutaway that extends from the
connecting rod. I've added a total of 3 cylinders/piston combos at the top
(north), at 90 degrees (east), and at 180 degrees (south) and I'm just
working out the kinks to get implement contact sets to test out the
functionality of these 3 cylinders working all at once.

Just before writing this reply, I had made some changes to the preferences
and settings to speed up the frames/sec and lighten the load on the
processor to see how much that makes a different during animations and
generalized usage of the program.

Again, is anyone else having problems with the forums? Is it all text/code
for you guys as well?

[TrippyLighting]

---

@Anonymous wrote:


Again, is anyone else having problems with the forums? Is it all text/code
for you guys as well?

---

It works on my side, but that does not really mean much. They recently changed things graphically and it may not look the same across the different web browsers and OS. I am on macOS mostly using Safari. Sometimes I use Chrome. Sometimes I use Chrome and  Win 10 on 2 different computers.

But  have noticed that AD's web sites work faster on Chrome, particularly I a forum thread/post includes a screencast.

Have you tried a different web browser ?

[Anonymous]

I am trying a new browser now. I'm using windows 10 with lots of RAM Memory, and a decent Processor. I usually use Firefox as an internet browser but Firefox is just shows a pile of links and words all stacked on top of each other in the middle of the screen. Then I tried Google Chrome, I got the same results, a messy pile of confusing text. Now I am using the default Microsoft Edge Explorer and I am finding that sometimes it loads the forum normally, showing the proper graphical interface but once and awhile it goes back to the crazy text thing.

Anyway, what's more important is that I was able to read through all the replies now and I see what people are saying. That is, as the experienced users have said, contact sets will fail with complex designs, so don't bother with them. Then,  "Trippy Lightning" suggested that I use the motion link feature or I could use a motion study as well.

I went on the program and checked out these tools and watched some YouTube video lessons about motion links and motion studies and found that it did seem like a good idea if I wasn't doing experimentation with the engine design.

So it seemed that using contact sets taught me some important things about the original design I had formulate some years ago. Now, because of the application of contact sets to the design phases, even with the limited usability of that feature, I was able to evolve the design to something that might actually be function in a real world application. My business focuses on the production of innovative products such as this and I am going to put this design project into the innovation resources vault to work on later or chances are, I might designate an employee to work on it for me, one that I think is going to be capable to build something that is structurally sound and can use the program Fusion 360 to run some simulations on the structural integrity of the model.

I've discovered that with the current engine design I can fit a cylinder every 30 degrees around the center axis of the engine cam-crankshaft. That equates a total of 12 cylinders acting on the central cam-crankshaft. With the given specs of a piston diameter of 4 inches and a stroke length of 3 inches that totals up to being a: (7.4 Liter) or a (452 cubic inch). And what's interesting is that you can arrange the engine so that two cylinders combust with a power stroke at the same time at opposite sides of the engine as the, combustion order then rotates around with 2 cylinders firing in unison, meanwhile, the engine, even setup with valves, like a 4 stroke, can enable a cylinder to fire on every cycle of the engine like a 2 stroke engine, as opposed to a 4 stroke engine. This is because with an ellipse cam-crankshaft there is 4 strokes of each cylinder for each rotation. And alternatively, instead of having two cylinders fire at the same time on opposite sides of the engine, it can be arranged so that the firing order goes around the engine, say, clockwise, with each cylinder firing after the previous, supplying a constant power to the cam-crankshaft every 30 degrees as opposed to every 180 degree's with a common crankshaft engine design. I find these specs remarkable. The power output could be tremendous, yet there are some stress points I'm worried about and would like to learn to put through the simulator to see exactly what's going on with the engine parts when the engine is firing with a power stroke or operating at high RPM's. 

I'll keep everyone updated about the progress.

[Anonymous]

This is what I have put together for the animation of the engine using contact sets. I haven't tried adding more, but I believe you were all right that when the design gets complicated with more and more contact sets it will start to slow down and glitch out. I can't use the "Animate Model" feature because it just freezes. It made me wonder... Is there a way to slow down the speed of a "revolute joint"? Or in other words, slow down the speed of motion of a joint when using the "animate model" feature?

Here is a video of the 4 cylinders I have functioning on the Ellipse Drive Crank (Cam-Crank) Engine. I had to move things somewhat slow to get it to work.

https://youtu.be/v5rM419ep7Y


Now I am going to try working with a motion link or motion study, or possibly even the animation mode in the Fusion 360 program.

If I had a faster computer with a better graphics card I'm sure I could add more cylinders.

Again, if there is a way to slow down a revolute joint? That might help with the animation.

[dieselguy65]

It works now, because it's simple.
I'll bet money it fails with enough parts added to make an engine

[Anonymous]

I got it to function with 12 cylinders with joints and contact sets. Its
slower than heck though. I can't move it much faster than it shows in this
video or else it will glitch out. However, if I had a real good quad core
and a high end graphics card (I think I only got a 64mb onboard) it would
run much smoother.

Here is the video:

https://youtu.be/DTugxYZyWOM