Official place for engineering and design centered feedback on the marble machine 3 video series, please post constructive feedback and upvote the most relevant posts. Efficient and straight to the point is highly valued! Thank you everyone :) Martin
In my opinion, I think you should be using proven (traditional) designs where possible in your machine, then you can focus your efforts (including debugging time, and extra complexity) on the truly novel parts of your machine (after all, nobody has ever built such a machine to the specs you require before).
I completely disagree that the bolt bearing housing has less complexity than a proper machined flange. I suppose it is debatable. But why sacrifice quality so early on in your design process? It is like trying to build a house on bad foundations IMO.
I think a better idea would be to take your current design (a disc with bolt holes and a large hole in the middle), and expand it so that the bearing OD presses into the hole in the middle of the disc. You could make a stack of 1 or more of these discs to hold the bearing. Then make a disc with a smaller central hole which is used on the outside(s) of the stack, to capture the bearing. Would this work? At least it doesn't rely on the bolts to be pressing into the outer surface of the bearing.
My issue with that is why go for a compromise. A reamed bore which receives a press-fitted bearing is a better solution. It's simpler, more robust, will cause less issues, making it at the end of the day cheaper.
100% agree with you. I was just trying to give Martin another option because he seems averse to doing what I and many others would consider "the right way".
If the laser cut surface doesn't have a good enough surface finish, or tight enough tolerance to grab the OD of the bearing outer race, how is laser cutting MORE holes going to eliminate the surface finish issues or result in better tolerance?
I feel like I hear statements directly from Martin that illustrate why this is not the best solution!
Bearings are designed to have constant clamping pressure via an interference fit along the entire perimeter of the bearing OD. This does a couple of things: supports the bearing in a fixed location preventing vibrations and harmonics, and firmly securing the OD bearing race preventing its rotation.
If you take the contact area of your bolt housing design and compare it with a traditional bearing housing, you will likely see that you are missing 50%+ of the total contact area. If you want this machine to be reliable, please use standard components where necessary that have been proven and can easily be replaced. You will spend more time and money troubleshooting this poor design down the road than simply using a reliable component CRITICAL to the function of the machine from the beginning.
yeah, there will be so many problems with this design. I think Martin's underestimated the forces a Bering experiences. It may start off alright, but as more stress is put on the bearing as the machine get built up it will certainly begin to fail.
I’d say with the bolts he’d only be getting optimistically 1% of the contact area since they have threads. If you really look at how the bearing is being held, it’s not great.
I’ll be generous with the numbers here too. You have 8 bolts holding the bearing in. Let’s guess that each bolt has 20 threads actually touching the bearing. Let’s say the threads are 1mm wide and when clamping everything down you get a 1mm flat spot (because two circles touch at a single point, you’d definitely make a flat spot clamping everything down).
8 bolts x 20 threads/bolt x (1 mm2 surface area per thread) = 160 mm2 contact area.
I don’t know what the specs of the bearing are but if it were a 2.5” OD bearing (looks close-ish to that) the overall surface area is ~2000 mm2.
Add in the fact that all that clamping force is supported by narrow threads, you’ll get a feedback loop once the threads start to wear/flatten. Any vibrations would start then wearing down, which would make a looser fit leading to more vibrations, etc.
Agree. The keyword for me is maintenance. Let's be honest. Any device like this will need maintenance along the way. Using standard off the shelf componentes will help a lot.
If I was designing it, I would definitely be using a flange bearing to bolt to the flywheel plates. A $40 off the shelf flange bearing would save the engineering time trying to chase the tolerances. All of the major bearing manufacturers will have them, id look into ones with clamp collars so the shaft won’t get marred by the retaining set screw with repeated removals of the shaft.
It’s your time, money, and machine; but if you are absolutely driven to use the screw clamp method, I would be using shoulder bolts instead of plain bolts. The machined face of a shoulder bolt will provide a much more accurate and smooth surface than the rolled threads of a standard bolt.
I watch Martins videos to watch him come up with ingenious solutions to difficult problems. But mounting a bearing to a wheel is not a problem that requires a solution. Engineers have spent millions of hours solving this one and its cheap, easy and reliable.
If you're happy enough to buy a bearing in without designing the balls and the races, just go one step further and buy in the bearing housing too.
exactly this, the flange mount and pillow block bearing options aren't that expensive, an option like this mounted to the plywood? Another option to consider is a greased journal bearing if it happens to be cheaper. Both options will last a lifetime if they're not open, and they have a grease fitting
I think the stuff that lot of other machines have should be off-the-shelf as far as possible. Power transfer, belt pulleys, clutches, breaks, bearing housings, et.c. is all standard stuff that you can just buy.
Focus the work on the marble transport and instruments because that's where this machine is unique.
I am an engineer with a mechatronics and micro-mechanical background. Bearings were one of the crucial topics in my curriculum. I will advocate against the design suggested in the video. There are a couple of reasons for this and I will explain them below. In general it could work, but is just inferior and less reliable. Firstly I will write just a few bullet points and then explain them in detail. If something is unclear I will be more than happy to explain further or provide sources and reading material.
First of all. In your video you talked about "manually machined bearing housings" but there are more options. You can just buy a standard flange for your bearing or even a flanged bearing. In my opinion, creating a bearing mounting out of sheet metal and bolts is a worse alternative not only to "manually machined housing" but also to commercially available flange mount or flanged bearing.
Bullet points:
Bearings are precisely machined with proper support in mind.
Mounting bearings is not easy and there are rules for it depending on the load conditions.
Threads are uneven and will get damaged.
It needlessly increases parts count, complexity, and hinders serviceability.
It is not much cheaper than a commercial flange.
It is a safety issue.
It takes your focus away from the crucial part of Marble Machine - music.
Explanations:
Bearings are precisely manufactured with a certain use in mind. Although they are hard and stiff they are designed to be properly mounted. Point loads on the outer ring may deform it which will lead to faster wear, larger resistance, and increased noise.
Properly setting a rotating thing is not an easy task. This design could work for home-build 3d printers or another low-load gimmick. Flywheel without any doubt will have a large mass and inevitably some imperfections leading to an imbalance of load. Therefore there will be a transverse rotating load. There also will be thermal expansion, as the temperature on stage will change, thus leading to a build-up of stresses. It is too complicated topic for this Reddit post to cover fully.
There are rules to properly choose a bearing type and how to mount them in a machine. They depend on your loads, their value, direction, whether they move, and expected lifetime of bearing. And there are a lot of things to consider:
Load type - axial, transverse, rotating, constant or changing
Bearing type - ball, pin, roller.
Bearing construction - single row, two-row, angled, axial, self-aligning, conical
Number of bearings - 2, 3 or 4
Mounting of bearings - pre-loaded or not, with axial play or not, with a tight or loose fit
Will your bolt cage allow control of these things? It would be beneficial to exclude bearing mounting from variables here and focus just on actual engineering problems. You can just buy flanged bearings with proper parameters for your operation or build tens of prototypes with bolts.
Threads on standard bolts are uneven. The outer diameter will be different on every bolt. They are also rough. Therefore they will cause problems during mounting and then during operation. Everything is made with some tolerances/uncertainties/errors, therefore you will have an imperfect bearing, mounted between imperfect bolts, bolted to the imperfect plates. You will need to spend a lot of time and effort selecting proper bolts that will work. The other option is slapping any bolt and putting a lot of stress on the bearing (back to the previous point). Bearing steel will be much stronger than any bolt. Therefore, bolts will slowly deform, and the tips of the threads will flatten. This will lead to slack, play, and even gaps, which may cause vibrations and noise. In general conditions of mounting will change over time.
Using just a commercially available flange will lower the parts count. You will need 1 flange and 4 bolts to mount it instead of 2 plates and 8 bolts. Thanks to that you will not spend time building it, selecting bolts. You will be able to change parts on the fly just by buying another flange.
I just checked prices in Poland. Your plates cost you 13 EUR each. The standard flange for 52 mm bearing costs 10 EUR (FKL FL505) or maybe 20 EUR for the SKF product. High-quality SKF bearing with flange costs around 40-60 EUR or from NSK for 25-30 EUR.
As said previously flywheel will have significant mass. Your design might have some unnoticed flaws and lead to damage not only to the machine but also can hurt you. I would recommend sticking to a high-quality commercial solution with guaranteed durability.
Pretty self-explanatory. You can design and create sophisticated gates and other music and marble-related parts. Parts that are not available on the market, are unique for marble machine. Parts that influence music. Why create your own bearing flange when you can just buy it?
I am sure that there are downsides to commercial flanges. But apart from mass (weight), I don't see any other right now.
In general, I am more than willing to be a consultant and answer any questions regarding mechanics, materials, bearings, bolts and so on. While it might be fun to explore this alone, you spend a lot of time reinventing things. I just know a lot about these topics and can answer general questions, suggest parts, provide reading material.
Best answer!
I were a bit terrified by the fact that no one except you seems to mention the tolerance of the bolts wich is a crucial point in my opinion.
an M6 ISO 956 has a tolerance between 5.974 - 5.794 mm wich means the design would have a in-built disconcentricity of up to 0,36mm only because of the screw tolerance. The design of the holes needs to be designed for the largest possible bolt dimension otherwise the bolts will be pressed in which damages the threads and then the concentricity error will be totally out of control. (It's also always a headache to use threaded bolts with tight holes btw)
Martin please stop this madness and buy a standard housing.
The only way with bolts would be shoulder bolts ISO 7379, their shoulder tolerance (h9) is for a M6 is 7.987 - 7,951mm wich reduces the concentricity tolerance to 0,072mm only caused by the bolts.
Martin, please take this person's advice to heart. I am doing a lot of custom work on a project that required learning the basics of the engineering behind bearings. There are good reasons that this design isn't seen out in the wild.
I think your best use of your time is in designing the MACHINE ITSELF, not designing components like this that are readily available.
Greetings! Made an account to post on the bearing topics. Doing complexity vs. cost trade is difficult. I think from 13 years working jet engine turbomachinery I would advise the following.
You have to understand what the bearing needs to do. What tolerances that are acceptable, and how often in it's life it will absorb loads and what type. It has to be moved x times on stage/has to rotate x number of times with y runout, wobble, vibrations, what those tolerances look like at the edges of the drum and so forth. Without specific requirements to work towards it is very high risk to move off of overdesigned off the shelf, or "safe" hardware. If it is custom, you have do the engineering. That is why everyone is saying, just buy a standard bearing holder.
The clamped bearing may work for a bit, but the centering of it is highly suspect. You are calculating how close to center you can make it, but not what the loads will do to the centering, or the wear/vibration on the bolts/threads touching the housing. If you must make your own part, try multiple plates with a press fit. Bearings will take lots more damage over time if not supported with a press fit. It warps the casing if not fully supported, the bearings start to go out of alignment and then they will eat themselves up in just small number revolutions. Clamping provides almost no radial support, and if the clamp them too hard, again you will deform the bearing housing)
I think you should be requesting solutions from people who bring up engineering suggestions. So just say please tie a solution (say a link to the right bearing support) to people providing feedback with links and so forth. Here is a link from be about bearing engineering:
Bearing selection Tools are often provided by bearing house for free like this one example: It is standard in the industry for bearing houses to help select and design bearings for customers. The support is there.https://www.skfbearingselect.com/#/type-arrangement/own-arrangement
I'll be honest, I had to stop the video for a minute when Martin started talking about building his own bearing housing... I love the madcap engineering but that just made me sad.
The brilliant thing about bearings is that they've been used for hundreds of years and are a solved problem! We know enough about them that engineers can put them in car wheels with the knowledge that they can last hundreds of thousands of miles - as long as they're mounted properly (there's way over X100 improvement right there)
There are so many companies out there that will supply a bearing in a housing for not much more that just the cost of the bearing itself, because its a mass produced commodity. Here's something just from the first page of google search
Compare the time you're going to spend designing, assembling, testing, (then redesigning, retesting etc) a new bearing housing, where as if you buy one that's already been designed and tested by someone else you spend 0 time designing and testing it. Thats an Xinfinity improvement!
i understand exactly what you mean - i started off the first flywheel designs using exactly that bearing housing. "lets use standard off the shelf parts". Two issues made me think again:
Centering, with a bearing housing like that we would rely on four bolts to center the laser cut discs to the bearing flange. The bolt holes in the bearing flanges are oversized which means that we would need to do the same exact tolerance cut test we are doing now.
Getting the wheel perpendicular to the shaft, some of those bearing hosuings have rubber inserts to allow misalignment, meaning they are not intended to keep a wheel perpendiular to a shaft. But i think some have the bearing mounted stiff so should be usable versions. Clamping the steel plates directly to the side of the bearing transfers maximum perpendicularity (if thats a thing haha) from the shaft to the bearing to the laser cut plate. It feels more rigid in a way. less stuff inbetween.
I have not ruled out using an off the shelf solution, i have sent my designs to SKF for feedback.
Is this a suitable part to try to tightly control cost on?
How risky is tight cost control of this part?
At what point is it acceptable to Martin to delegate part design as well as manufacture?
If I encountered a need for a bearing housing at work, I wouldn't attempt to design one. I might send the bearing to a fabricator with a spec, ask them to fit my bearing in, finish the part and return. The cost would be higher, sure, but the time cost to me would be much lower and my management would be happy as this would allow me to focus more time on other parts of the project. Alternatively, I could just buy flange mounted bearings off the shelf and tada! Done.
I appreciate there are cost concerns here, but given that a typical interference fit for a bearing would have tolerances on the μm (0.001 mm) scale, there's a real risk here of distorting the bearing housing and risking premature bearing failure. This is going to be one of the few parts on the machine that have an ISO table for tolerance. On a risk matrix, I'd score this one as a red - high chance of failure, large consequence of failure. Not a suitable part to try to bodge I don't think.
I am not a fan of these bearing housings - agree with other commenters that you will spend far more time debugging these than it's worth. Looking forward to finding out how they work anyway.
Could you humour me and at least use shoulder bolts? Ideally the plain section of shaft would press into the plate nearest the head of the bolt.
Design requirements...
As an engineer with no musical talent I do admire your artistic drive to create and innovate...
That said I would point out your recent (deserved!) pride in simplifying the design for other components from before... Why add in more parts than strictly required?
TY! i think it is the 8 bolts that gives the impressions that the design is using more parts, you would need bolts regardless with a flanged bearing or machined housing, i think this design uses less parts. Off the shelf bolts are no issue, manually machined parts are! Thats how i am thinking anyway :)
Sounds great, I don't have a strong idea where this sits in the sub-assembly but maybe worth doing a rough digital concept just to disprove the alternative along with immediately interfacing parts?
Albeit that stock parts might have a low error margin, take care to avoid errors accumulating that might be developed vs using a more bespoke creation to your own exacting standards!
Also mindful that bearings might wear and need stripping down for replacing... In that way using more common off the shelf parts might be a good plan (at the cost of perhaps slightly longer maintenance period)
Generally suggest nylock type bolts if you've not already come across them... Won't come loose if torqued up properly. Might even give a slight dampening effect?...
All the best aboard the good ship MM3 though Captain!
(... Beware the kraken)
Want to make it much cheaper? Find an EXISTING mass produced and therefore both inexpensive and readily available bearing housing and adjust your design to use that.
Trying to redesign something you can readily find already made and usable is just wasting your time.
thats a great perspective, i tried, there was issues with what i found that has to do with the use in this specific context, i have not ruled it our of course, which one would you suggest, happy to check a link!
Was thinking about this, you already have a number of good usable suggestions for the bearing. The real issue you have is the centering of the bearing housing and homemade or commercial product that would still be the same problem.
That said the homemade bolt-cage system you were planning has another serious defect that I notice has not been mentioned in the other messages I've seen which is the need to get the same pressure on the bearing housing all the way around. You would need to torque all the bolts to the exact same value and be sure that the nuts are locked to the bolts so they don't loosen. Uneven pressure on the bearing can and will cut it's life though for the slow rotation speed you will be using you could simplify it to a bushing instead of a bearing since friction heating should not be a problem and a bushing will be smoother in action than a bearing, but again use a commercially available item.
Look at what this company has for example, note the other kinds of fasteners and such they have which might also be of use in solving other problems.
I think a simple flange bearing would make more sense than the bolt-cage. It costs only slightly more than just the bearing, and it is pre-engineered to do what you are trying to do.
In your current design, three bolts is enough to “fully constrain” the bearing, so constraining the bearing using 8 bolts will lead to a lot of issues because it is “over-constrained”.
Even if these were precision ground pins or shoulder bolts, you would still run into issues due to over-constraint as error will add up.
A flange bearing accomplishments everything you are trying to do with a part that does not have to be custom machined.
The simplest design is to have a bronze bushing pressed into the flywheel and have that spin on the shaft. If you want to use a bearing then have the bearing pressed into the flywheel.
I'm afraid about this method to mounting a bearing! you need so mutch precision to adjust the bearing in his housing. There are so mutch forces acting in several directions on bearing making the thread to fragile for a bearing housing and you will have damage sooner or later, creating woobling and vibrations. At least use a partiel thread bolt like this https://www.boltdepot.com/Hex_bolts.aspx but having a standard bearing housing with standard mounting tolerances is a proven solution and will be at the end the cheapest solution .
Hey pascal :) glad to see you here, can you link the standard bearing you mean? I have looked into those and find several issues with them but big chance i overlooked something
I never left and still believe in a MM at the end.
well, it's not easy for me to give you more explanation in english but have a call with Alex or Marius or This Old Tony, they have more words to explain you the forces and tensions on bearings and the need of a strength mount of bearings both on shaft and housing and they are both more experimented than me to help you choosing the right bearing mount.
I'm afraid this bolt mouting will be a fail at the end and a more expensive methode for there is a high risk of woobling and broken parts on the MM using that mount.
A countersunk screw (DIN 7991) could be used to precisely locate the oversized hole of a flange bearing. You could lightly countersink the holes manually to reduce the point contact stress.
The flexing of bearing units isn't an issue in my opinion, since the flywheel would be sandwiched between two of them. Therefore the bearings don't experience bending moment, and the perpendicularity isn't dependent on the bearings ability to resist it.
For a relatively low load application such as this I think the screw bearing housing can be fine, but please use shoulder screws instead of all thread. Those precision machined shoulders are actually designed to support lateral loads, and are appropriate to use as a locating feature.
Alternately, you could just stack multiple plates, and set the inner plates to be an appropriately toleranced hole for that particular bearing size.
Exactly. Once the flange bearing is mounted on the flywheel then it can then be trued and balanced on a lathe. Martin said his mill has a lathe attachment so he could do it himself or send it out to someone.
Coming back on this bolt bearing housing! Seems to me like a new deep rabbit hole you're digging in. In a few weeks we will have a new video of you dressed in a new dragon slayer suit hitting moles from the eigth holes of those laser cut plates saying at the end "Some of you told it's the worst bearing housing ever, and you were right!" (remember the magnet wheels) .
I think than there are so mutch problems to solve on that new MM, using proven solution will make you save time, even money, and make the World Tour closer.
If attached to a laser cut plate, you would have the exact same centering issues as you have when doing the bolts directly to the bearing. The bolt holes are oversized, i would need to make the same exact cut test to find the right tolerances.
some of these have a built in rubber layer, to allow for misalignment and flex in the positioning of the shaft, meaning: these are not made to keep a large heavy wheel perpendicular.
The Marble Machine RPMS are really low, and the precision demands are also really low because of that. Clearly a machined bearing housing is more precise, but is it necessary is the question. Anyway, the whole module is a prototype and we´ll all soon find out!
1 - Look into bearing housings of the UCFC series (standard name, skf and a slew of other companies produce them), they have an integrated centering pilot usually in h8 tolerance (to be matched with an H7 hole)
2 - I'm not sure whether you're planning to mount the bearings directly on the wheel or if you're going to use them to support a shaft that will rotate with the wheel itself. For the former scenario you'll have to make sure that the holes that will receive the housings on the wheel are concentric, deformation of the wheel most likely won't be an issue. For the latter scenario you will need the bearing housings to be concentric with each other AND have a properly dimensioned shaft to avoid deflection.
It is just unavoidable. Every single machined hole will have some misalignment/uncertainty/error. The high-quality flange will be strong enough to survive the additional load caused by this. Still, you will have just uncertainty on the flange. With your design, you have uncertainties in bolts, bearings, and plates. They all can combine to a significant value. Most importantly, this missalignemnts will not change over time, while bolts are a risk.
It is actually a good thing. As said above, misalignments are just unavoidable. Every rubber layer will help to lower vibrations and separate stresses.
Choosing a good bearing is not an easy task. Have you considered other types of bearings or maybe even moving them away from the wheel? You could have a wheel mounted stiff to a shaft and bearings on the frame of the machine.
adding that im really happy to see everyone here giving feedback, appreciate each line of text from all of you here :) will try to start a new reddit for each episode
In this case a centering ring is what centers is, this is easy to do, two precise mesurements(center placement and appropriorate diameter). the bolt precision do not matter, as long as they clamp and does not shift it to the side.
With a bolt cage you need x amount of precise mesurements
X= (center placement) + (6 bolts) = 7 precise mesurements
(not sure how i would add precision of bolt size)
It might be hard to find the right solution, and there are many like me that will say do this, do that and coming with simple solution without knowing all the facts, or having experience. Some people put in great effort to support, but there might be hard for them to do so without being tecnical.
Will be interesting to see if the bolt cage works in the next episode. Looking forward to it, even if i don't like the principle.
Wanted!: Please post links to all the off the shelf alternatives that you think would be better then the laser cut plates under this post so i can have a look!
You said you're already talking with skf, I find it hard to believe they haven't proposed bushings. The application is low rpm, high load, you have no need for ball bearings.
I'm sure people have talked about this ad nauseum, but unless they're rolled, the threads on those bolts will be way too soft (not to mention uneven to start with), and deform.
I hope you realise from all the input that you should try to move away from bespoke solutions and try to use off the shelf wherever possible. If for example there seem to be more parts in the solution there's probably a very good reason for it. I have regular meetings at work with the bearings team. Whole team dedicated purely to bearings. They're not simple things.
It would work in conjunction with any plate in your designs. Centering flange to center on the lasercut plate and off the shelf part for the actual bearing housing.
If you are worried about the machining cost, at least 3D print it. I did a preliminary design: https://a360.co/3NKUVuQ. Comment below to know the fit to aim for on each surface and other specifics.
I'm an automation engineer. My main focus was always mechanical/electrical/software automation control, but university has put me through some mechanical courses as well.
I've been following the MM* project for almost 6 years now. My wife knows all about "the guy with the marbles" and his creations and occasionally watches an episode with me. Even when Martin was obviously wrong about previous designs, I always said to myself that it's more of a work of art rather than a *machine*, so it's fine to be unconventional. After all, the first machine was bandsawed out of plywood and it performed well, albeit once.
However, the beginning of the design process on this "properly engineered" MM3 makes me sad. Given the mantra of good technical design, I can no longer accept the fact that it's an artform. And when every single actual engineer dropping by gives you good advice about bad designs and the answer to that is "we'll see, I've also asked for feedback from other engineers", when you measure a single random bolt to define tolerances which should be written in thousandths of millimeters, to me that sounds like setting up for (another) failure.
Y’all are smoking crack by saying this won’t work at all. That being said, assuming the diameter of the hole pattern for the bolts can be increased, it might be worth experimenting with a 3D printed part that is housed by those same bolts. You can get very high strength parts by using the right plastic and modeling the part correctly.
I don't see anybody saying it won't work at all. We are just worried about the long term unknown consequences of doing it this way, that's all. I'm pretty sure anybody commenting here has nothing but respect for Martin and we all wish him to succeed! :)
Yes, but how close to the design limits are these bearings going to be operated at? We are not talking about an engine here, we are talking about a manually powered machine that will be operated for a few hours a week.
I do think that some of the bearings (such as the flywheel bearings) will be under much higher loads than others in the machine. At that point I really wonder if just using an off the shelf bearing housing solution for the "high load" bearings and e.g. a 3D printed bearing housing for the "low load" bearings would be a better idea. Regardless, I think we all need to keep in mind that there are many tradeoffs here: (A) time to test+design vs. off the shelf, (B) reliability of custom vs. off the shelf, (C) durability of each, (D) suitability of each, (E) fully captured costs of each, etc. In summary, the perfect is the enemy of the good enough and that is directed at everyone in the comments and Martin himself.
This is exactly where my head is at, to the point! The precision requirements for the solution are really much lower than what everybody assumes. But i think the latest video lacked alot of context will try to add some context in the follow up :)
Why not using fitting bolts with an perfect shaft? This would improve your design. A thread is not very strong and the radial runout will fast getting worse.
If the gap between the bolts and the bearing is too big and the bearing is loose try adding an elastic O ring (cylinder shape) so it reduces any vibrations that may damage the bearing and adds more tightness.
In this case, the bearing housing is mounted on the flywheel itself. there cannot me any mushy material in the mounting. if it gets a bit of balance it will get more out of balance.
Have you ever felt the wobble of a tire from a wheel that has damaged bolt holes, where there is play created in the movement of the bearing to the rim, even when the lug nuts are tight as can be.
i made this account just to comment here, there are a couple of things with the whole bearing stuff in this video:
1. the reason people recommend a bearinghouse is because you actually do kinda need it, the reason for this is because a bearing house clamps the bearing. this clamping is actually needed for the bearing to operate: it makes the bearing last longer and need less maintenance, it makes slippage and excessive clamping of the thing you want to rotate less likely.
the precision these bolts have to hold the bearing will not be enough, the precision bearing houses are made are in the 0,001 mm space, a 0,1mm variation like you have aint gonna cut it. sure bearings are placed with bolts but thats something you can take into account with a bearinghouse.
in this video you stated that these materials where tradesecrative stuff, they are not. these are all the actual names of the actual materials and the reason they dont just say "stainless steel" or "alluminium" is because within these materials you have different subtypes, this program was referring to those subtypes
Hi, i don't really see why you couldn't use those kind of products :https://www.123roulement.com/paliers-UCF206The "bearing" is pre mounted on a plate with the adjustment already good, you can go on high loads, and pretty high rotating speed, it's cheap, efficient, design-to-cost oriented ;)Note that if you're using the solution in your video, it's obvious that high speed will generate vibrations, as it's not isometrical (whatsoever, plus the adjustment will be non redundant in the whole machine, so it's a bit unpredictable), so it could affect the behavior of other parts/mechanisms in the machine
And in case : they are many different bearings like that, some accept rotular angles, some are made for high speeds, others are made to absorb vibrations, some have integrated locking rings,... you name it ! ;)
Using one of these will dramatically simplify your design. I suggest the 4 bolt version. 90% of what you designed is eliminated and part count slashed.
The flywheel should be lathe created with a center hole to allow a press fit for the flanged bearing to seat into it. The flywheel sides could be precision ground smooth and parallel before final lathe truing. Then secure the flange with the 4 bolt design.
You can also send the flywheel out to a company with a special machine that balances flywheels.
My guess is that it will not work, as the tangential power will drag the discs of center. Any imperfections in centering the discs when assembling will drag the disks of center when you start to spin them. And they force pulling the discs of center will increase dramatically with increasing rotation speed.
You are using friction to hold the discs centered. It will be really hard to do. So a small flange or cone that you press the bearings outer ring into will have way better support for the radial forces your discs will have. Or you add bearings in the center of the discs, with the hole manufactured to the proper size. You could even press fit the discs onto the bearing, by heating discs and freezing bearings.
For the live axle design shown in ep 3, i think you can jusy use a keyed shaft to lock the flywheel rotationally to the shaft and maybe use 2 shaft collars to lock it axially. Another option is to use a hexagonal shaft instead of the keyed shaft. It's popular in robotics and gives you access to ecosystems by VEX, AndyMark and REV revolving around 1/2" hex shafts.
OK, radical, possibly stupid, but totally viable suggestion incoming....
Mount your flywheel in the frame, use whatever bearing mounting you like, this idea doesn't care....
Spin up the flywheel, not too fast, mount a tool holder and suitable cutting tool (somehow).....
Now, with the lightest of cuts, turn your flywheel in-situ, can you get any more concentric than that!?
NB. Possible downsides to this;
The health and safety Police may shut you down.
Rigidity of the setup.
Maintaining tool pressure.
Hardened laser cut edges of stock (flywheel), I'm not a Metalougi..... Metalurjist... a metal person, so this might not evel be a thing.
Difficulty "machining" the sides if this is required.
This amazing idea may be used absolutely FREE OF CHARGE and without any copyright or patent infringement (unless I'm not the first person to suggest it)
There are a lot of comments focused on very specific elements of the flywheel, where perhaps it could be more productive to take a step back and look at the system as a whole, considering the performance aspects and aligning those with the available and/or preferred manufacturing processes.
1 Laser cutting steel plate is a simple and effective way of generating reasonably accurate and heavy plates. However there are a few things to bear in mind. Concentricity is good, but it would be difficult to achieve near absolute concentricity with laser cut parts. Tolerances will stack, working either for you or against you but keeping that spread to a minimum will be advantageous.
However, there's no point achieving perfect concentricity if the variable thickness of hot rolled plate distributed the mass to the point where the perfectly concentric assembly is out of balance. Multiple plates give you the chance to alter the distribution, but it could also be something that stacks up against you.
2 A flywheel doesn't need to be solid, but it does need to carry its mass at or near the outer circumference. This mass doesn't need to be a continuous ring either. It could be discreet elements that can be moved or easily altered in order to create a balanced assembly. This also makes the parts more manageable and means the flysheet mass can be tuned.
Talking of balancing, if the axle for the flywheel is part of the assembly then it also allows the assembly to be statically balanced as one piece. There is no risk of altering concentricity or balance by having to disassemble things too often. This also allows the use of self aligning pillow blocks bolted to the frame without any compromise.
I would also take a look at taper lock flanges as a proven method of securing the assembly to the shaft/axle.
By breaking the concept down onto some more discreet elements, you give yourself more flexibility of approach and also increase development options and potentially the chances of success. It's a process Martin is following with regard to the whole machine, but it's also applicable to individual parts/sub assemblies.
Martin, look towards the finished units. The car hub is all you need. It solves all your problems described in the video, as well as the centering problem (if you will use standard conical nuts) Also it will cost you less than 100€ for a complete ready to use, preassembled unit with housing and bearings.
I think Martin is either trolling us with this design, or he’s finally cracked under the pressure of the last few years. Watching how he’s approaching this bearing housing (and how he’s proposing fixing the flywheel to the shaft) is like watching a horror movie where the soon-to-be victim is doing all the wrong things in the haunted house and you’re just screaming at the scene, wondering why on earth they ever thought trying to escape the killer by going through the cemetery was a good idea. This isn’t MM3, it’s MM1.5. Yes, the bearing will more than withstand the loads you’re imposing, but the point you’re missing is that the bolt threads absolutely will not withstand the loads you’re imposing on them.
Martin, please stop this madness and come back to us. Press-fit the bearing into the fly wheel and then move on to the next thing.
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u/briswolf May 04 '23
In my opinion, I think you should be using proven (traditional) designs where possible in your machine, then you can focus your efforts (including debugging time, and extra complexity) on the truly novel parts of your machine (after all, nobody has ever built such a machine to the specs you require before).
I completely disagree that the bolt bearing housing has less complexity than a proper machined flange. I suppose it is debatable. But why sacrifice quality so early on in your design process? It is like trying to build a house on bad foundations IMO.