Hello. I am trying to design a new Mecanum wheel and I read in a few papers that, “when designing a new drive system for a vehicle, there exist a certain number of rollers that makes the ideal compromise between having a small number of large rollers per wheel, and having a large number of small rollers per wheel”
Is there any basis on which this assumption/approximation can be done?
I am trying to find a justification for arriving at the number of rollers for the Mecanum wheel to be designed, depending on the drive wheel diameter.
For example, I am designing a Mecanum wheel of diameter 6" for medium duty application. According to survey of various manufacturers, the rollers in the wheel are ranging from 8-15 in number and I am wondering how to decide the same for my design of a new Mecanum wheel.
Anything related to this will be much appreciated. Thanks in advance.
Sometimes decisions like this depend on ease of manufacture, or cost. So, how it’s going to be made, might be important to know for this decision. And you didn’t tell us.
I intend to design a 6 inch Mecanum wheel. The cost need not be extremely low as it will be done in a group. So my main criteria would be the vertical vibrations, smoothness of ride and the load capacity of the wheel.
And when it comes to how it’s going to be made, we have access to fairly sophisticated machines to comfortably manufacture any type of Mecanum wheel.
I am not able to completely understand the initial design process, that is, arriving at the number of rollers for a 6 inch. wheel diameter. Maybe the attached files would give clear insight on the same.
Do you have a list of priorities for these characteristics? When there are trade offs, you kind of have to figure out which is more important to you.
I am aware of this sir. I just want to know the process of selection of the number of rollers for a 6" Mecanum wheel heavy duty applications. Because various manufacturers have used different number of rollers and the selection is not justified anywhere.
Have you seen any difference in the specifications for these different wheels? ie. do some have a higher load capacity, longer life, lower cost, less weight, etc?
You still have to figure out what your priorities are, then perhaps you could design a few different wheels with different numbers of rollers, and see how the designs compare, as far as how much load they can take with the materials you intend to use, etc.
Let me preface this by saying I don’t directly know the answer to your question. Two important features of mecanum wheels that seem to depend on the number of rollers are: load capacity and roundness.
Fewer rollers would allow you to use larger rollers & larger axles, which would support higher loads.
Because a mecanum wheels is composed of rollers, it isn’t actually round. As it rolls, its effective diameter changes a bit (directly over a roller vs. halfway between rollers). I haven’t looked into it too much, but I think you can accomplish a rounder wheel with more rollers.
Fewer rollers would allow you to use larger rollers & larger axles, which would support higher loads.
Yes I agree with it. But we say fewer rollers allow us to have a higher load capacity and more number of rollers will give roundness.
But there is no clear quantification on the exact number of rollers for the design purpose. There has to be some justification for the selection of number of rollers right?
You still have to figure out what your priorities are, then perhaps you could design a few different wheels with different numbers of rollers, and see how the designs compare, as far as how much load they can take with the materials you intend to use, etc.
That’s the neat thing about design. You have to make a decision, and there isn’t always an equation to plot the optimum answer. Try a few designs, see how they compare…
You’re asking an engineering question about optimization.
The problem with an optimization problem is that it varies by what you want to do and the specific requirements for the job.
You’re asking us to optimize your problem for you. We can’t. We don’t know what your requirements are.
So this is where the previous poster’s suggestion of “try a few designs, see how they compare” comes into play. Take a best guess at what you’ll need for your specific requirements. Design the wheel. Run strength analysis and smoothness analysis. Do it again with a different number of rollers. Maybe do it a few more times. THEN, look at ways to play with the rollers on acceptable strength measures to get a smoother ride.
Going back to the original question: There is no particular method other than to iterate in this particular case. If you’re trying to find that method, you’ll probably have to develop it yourself (and please do share it if you do).
Fewer, larger rollers will have higher load ratings because you can use larger pins/bushings in them. However, I suspect either the smoothness of ride or the kinematics will suffer if you have too few rollers. I am far from an expert on roller design, but this may be a tradeoff.
Many smaller rollers will probably cost more due to high production quantities, and have a lower per-roller load rating, but also will lend a smoother ride if you have suboptimally designed rollers. I would definitely try and print a few small mecanums with 4-10 rollers just to see if your roller design is good and how the smoothness/efficiency is affected.
My process would be to select the smallest roller that can take the loads I want it to, then check cost compared to doing a smaller number of larger rollers. I have little faith in my ability to analyze a properly curved mecanum roller, so I would try and compensate with additional rollers. Multiple full-scale prototypes would be helpful to test efficiency. If your group can analyze a mecanum roller properly then your approach will probably change.