BEARINGS -The Secret Life of Components - a series of guides for makers and designers - Episode 8

[Music] [Applause] [Music] [Applause] [Music] good bearings can make things move really easily this video is about my experience of using bearings i make arcade machines and clocks and other weird contraptions i've been in this workshop 40 years and practically everything i make has bearings of some sort of rather in it uh i'm not a bearing expert though and i'm sure some bearing experts will be horrified by what i do if you want to skip to a particular chapter here are the contents well when i was a kid and i didn't have my nice workshop or any tools it was very hard and i feel sorry for today's kids trying to make things out of paper cups and drinking straws and stuff like that because i didn't have there wasn't pva there wasn't hot glue there weren't even bamboo kebab sticks which uh i'm quite fond of now so you just poke it through a shoe box i should have said i make used to make everything out of shoe boxes when i was a kid and she bought shoe boxes and sellotape and then um i haven't done this i haven't even done this very straight but you'll get the idea it actually runs quite smoothly but this video is not really about making things like that now i've got my nice workshop and tools this uh video is more about conventional bearings of course in ancient times they did use wood a lot as bearings and they made almost everything out of wood so shafts and bearings with wood it's not ideal because wood gets hot when it's uh with the friction it has caused spires and mills from the 16th century onwards uh when tropical hardwoods became available um things improved so some extraordinary woods were imported like a lignum v-type three times harder than oak it's it's so hard when you put it through the saw it comes out already polished much heavier than water sinks like a stone this actually feels quite oily in fact i can show you it as a bearing so i've just drilled some holes in my bits of lignan vitae uh just put it through here and it runs it runs perfectly smoothly but it actually carried on being used for the bearings of ship propeller shafts right up until the 1960s the americans first nuclear submarine had lignan vitae bearings but of course today there are lots more materials available and also very little lignum vitae so it's no longer used now a much more common material that came in to use in the middle ages is brass steel uh shafts running in brass is very common really uh if you think of all the classic victorian bits of engineering so brass was used for very big things like steam engines but also for very tiny things for clocks so this is a just typical 19th century clock though mechanical clocks are still made the same way and there's always two brass plates and all the the gears and stuff are in the gap in the middle this one's all gone rather rusty um and these steel shafts are just supported by the brass plate you can see um the holes these little depressions and that's where the ends of the shafts that run through now something interesting about these shafts i'm just going to undo one one of the shafts this is the one that supports the [Music] pendulum now there's there's the shaft that's the shaft this has got the pallets all very rusty but the interesting thing about it is the ends of the shaft you see how much smaller they are both both ends very much smaller than the rest of the shaft and these are what poke through um the brass this is the little hole that that that pokes through and this obviously stops the shaft slipping sideways but the other advantage is that it reduces the friction i think it probably is because the viscosity is the oil there's less area for that to slow the thing down i didn't used to use a lot of brass because it's quite expensive i've only started using it recently since somebody retired and left me a whole lot of brass and it's lovely stuff to turn it uh it's really quick to make pulleys and little bits and pieces that collars and shaft mounts and that sort of thing so i enjoy using it now one thing i haven't talked about is oil the friction of one material running on another is much less with an oil film between them put a drop of oil on there's then actually a coating of oil all around the shaft it's very thin but it's enough to make quite a big difference in fact if you look at the tables the coefficients of frictions it's like 10 times or more less friction so although there's a drag from viscosity solids run amazingly well in liquids sort of almost friction free in the 19th century canal boats and which took about 70 tons load um they were pulled by horses along the bank but when he went through a tunnel the crew had to push them through with their legs it was called legging it and that's where the expression to legit comes from today they're still some of the beautiful frontal lens assemblies in lighthouses actually float in whole bars of mercury uh almost 100 kilograms of the stuff in the past i use a lot more hard plastic particularly this stuff called delrin proper name is acetyl it's the stuff that's used when you buy a plastic gear that's made of the same stuff you can see uh how well it machines you see the inside of the hole how smooth it is and that's just with a drill so what i tend to do for a delrin bearing have a set of drills that uh go up in 0.1 mil increments so for an 8 mil shaft i'll use an 8.1 mil uh drill bit and that that just gives you a nice free running um shaft and i find that works better than using a proper reamer a similar plastic well it's not really similar but it has is used for similar things is a toughnel brown plastic traditionally this was quite an expensive thing it's the price has come down quite a lot now it's extraordinary it's actually layers of cloth um with and then under high pressure with the resin and it makes a very rigid plastic i really like this stuff or you can sort of see the texture of the cloth there too yes it's very hard wearing as you can see in this arcade machine i made a few years ago in the housing ladder you try to get a small figure inside to climb to the top the figure is made of toughnel he's climbed the ladder about 55 000 times now and there's still very little sign of wear in his joints congratulations the house is yours conventional wisdom is that the bearing material is softer than the material of the shaft but actually i quite often use steel as a bearing material with steel shafts um i use it all the time for prototypes but also for things that don't run that fast or run during your run intermittently it works surprisingly well and then of course all you have to do is just drill a hole in a bit of steel so it's very very quick if you've got box section then you can drill two holes if you're just starting out a drill press is a great first tool to get you can get little ones very cheap because it means you can drill accurately at 90 degrees to something so you make your holes perpendicular to the material and also where you have to push hard to drill through steel and uh of course a drill press makes that really easy and so you know that's your bearing done and it actually spins pretty freely and will last a long long time without too much wear best to grease it if it's a permanent thing just because it'll start to squeak but um i think it's sometimes it's underestimated and after all hinges are just steel running on steel it's not that bad so uh next i'm going to talk about bearing bushes these go between the shaft and the material you're they're mounted on and my favorite sort of bush is uh scented bronze uh impregnated with oil if we zoom in i think you can almost see the structure they're actually made of powdered bronze um that squashed together and then filled with oil when they're hot they feel completely dry but uh there is actually a lot of oil inside them i'm now going to try and heat one up and uh with a heat gun and see if i can get some oil to come out of it [Applause] actually start dripping i'm not sure oh yeah there we go [Applause] so these bearings they stay oiled for a very long time i've never ever had to replace one actually in any of my machines and they're quite easy to use the fit isn't as critical as you might think the outside uh if it's too tight you can quite often hammer it in or squish it in in advice sometimes i make the hole too big by mistake it's just like for this one for instance i've got it a bit too big so you can even a fit a loose baggy fit like that you can put loctite retaining compound in it or um you can sometimes dot punch around the steel around the edge to squish it in i'll try and do that now um and then it's pretty well held then the inside of these bearings um they're usually rather a tight fit to start with um so a good tool to use is a reamer um these are you can buy them on ebay or they're not that expensive but they leave a smoother hole um certainly in these bearings than a drill bit another quite common sort of bush is a plastic bush some plastics have been developed specifically for bearing uses uh i used to use quite a few of them and they they initially they seem to work beautifully um so if i just they they slide over a shaft really really nicely you don't have none of that fitting with a reamer or anything and they just sort of they just they feel lovely but the problem is they wear or at least in my applications they wear this water clock on south or pier has some plastic bearings it wasn't a good choice there's hardly anything left to do now but somehow it all manages to carry on working despite the enormous room in most situations i've abandoned abandoned them one place where i still use plastic bushes i use these small ones i quite often use them inside delrin uh because both delrin and these you don't need oil they run dry um but the delrin does wear with thyme and these we're slightly less fast than the delrin so it can be an improvement another sort of bush used in watches are the jewels in watches they are actually just the bearing bushes this is a pocket watch old pocket watch proudly saying it has 15 jewels uh these are the jewels you uh i don't know if you can see them the round round there they're actually tiny little bits of ruby uh with holes cut in them um you can't really see their ruby in that one but in this ladies walk they're much more obviously red you can almost see the hole through it in the one in the middle uh i was going to say a little bit more about oil um one of the most important things about oiling bushes or any sort of bearing is not to put in too much if you have just oil hanging about it uh it attracts dust and grit uh and becomes sort of grinding paste and i've had things where quite badly with uh with this uh so it's amazing how little oil you actually need this pen uh is um my watch oiler and so little comes out of it uh that i have to test it out on a bit of paper every time i use it just to see whether so if i do a little dip there yeah i can see that uh something is coming out and so literally all i would need to do to oil my pocket watch a bearing on the pocket watch is just to put uh dip it in a couple of times and i wouldn't even see it i'd oiled it but uh i have and the same is true for bigger things though you can use a little bit more oil obviously of course some bearings bushes run completely submerged in oil most obviously in a car engine in the sump the bottom half the engine is full of oil uh and so the crankshaft is rotating in oil so this is the shell and the bottom end of the big of a big end and the bearing is just the bush it's just this bit of uh metal on the inside whoops called white metal very thin and it it's extraordinary really when you think about it this this skinny little bit of metal it rotates at least 2 000 times a minute and goes hundreds of thousands of miles usually the whole lifetime of a car you never have to replace these things and that's all it is i'd forgotten though uh until i stripped that engine apart that uh the crankshaft has holes in it so that there is oil being squirted on the inside as it goes round i'm sure that helps there's also a weird thing if dirt does get into a bush um so hard bits get embedded in the bush material like in the white metal of the car engine or in one of my oil light bushes and these can be really hard bits that then wear away at the shaft so you you open up a damaged bearing and you find the hard part of it has worn more than the actual softer bearing material well that's why and so when you have to replace the big ends on a car you nearly always have to have the crankshaft reground at the same time in bushes the sl the shaft slides round the surface of the bush so it's it which is called sliding friction um the alternative is rolling friction so to show you the difference i'm going to use this great big lump of cast iron put on the bench and connect it to a spring balance so to get it to move just sort of nearly three and it's always more to get it started and then it goes down a bit once you've got it moving i can probably get it a bit lower by adding some oil to the table and uh spread it around yeah that's more like two or two point now it's got to stick a bit so it's definitely it's definitely a little bit better than it was before but now rolling friction and i'm going to roll the lump two steel rollers more okay so connect the spring balance as it dramatically reduced yes quarter of a kilogram big difference and that's why ball races are so widely used they are wonderful amazing things the inner race rotates on the balls which in turn roll against the stationary outer race leonardo had the idea um but it wasn't possible to make them until uh the 1870s uh they initially just designed for the first bicycles so this is a ball royce um there are nine balls inside a cage in the middle and so the balls roll around between the inner and the outer and they do roll incredibly smoothly if i get my blow gun and squirt a bit of compressed air onto the rim of the ball rice [Applause] it'll actually stay spinning for a very long time several minutes so ball races are good any any situation where you need low friction uh and i use them quite a lot it's quite often very useful to me one particularly dramatic example uh was some gates i made for london zoo they were vertical sliding gates for a tigering closure and they'd specified this very heavy solid metal to protect themselves and the tigers obviously uh and so the gates ended up being very very heavy i had to add pulley blocks to uh so you pulled further and to lift the gate and it all seemed to work fine and was passed initially by the keepers but then late in the day they came to inspect the finish thing and some of the keepers are actually very tiny and they couldn't lift the gates even with the pulley blocks uh well i've made it by then it was sort of the first one it would have been a major business to start all over again but i realized that i just use ordinary yachting pulleys um these these little um these little things oh i think i think the bearing has just finally just stopped spinning um yeah ordinary yachting pulleys you can get uh yachting pulleys with ball races but they're usually open ones and because these are going in the tiger cages i thought they'd all get clogged up with straw so and they were the only ones with ball races i could find so um i decided to make my own and uh out of aluminium um with uh two ball races in between i can show you the difference it's dramatic so this is the little yachting pulley that i that i've first tried the tiger gates with um i string it up here uh this is two and a half kilograms i'm lifting it the weights uh put the spring balance on and uh i have to lift with about three and a half kilograms force so now um i'll swap this for my homemade pulley with bearings with ball races actually already feels less effort and though maybe that's psychological and put the spring balance on and yeah it's less than three uh i don't know if you can see it exactly what are we reading god it's yeah it's sort of too it's varying a bit but it goes between 2.5 and 2.9 so with the yachting pulley the bush yachting pulley i was having to pull an extra kilogram more than the weight so that was all the friction in the pulley with the ball race i was only having to pull an extra quarter of a kilogram so a quarter of the friction big difference so even the tiniest keeper can now lift the gates easily so there are millions of different sorts of bearings but actually i usually use them way below their rated load and borrow their rated maximum speed i usually just keep in stock one of each size 6 8 10 12 and 16. there are some varieties you can get extra skinny ones so the outer diameter is a lot smaller and that's useful if you're tight for space and it makes a particularly big difference when you get up to bigger diameter bearings can be very useful then you can also get stainless steel ones they're good uh on the pier for me whether with the salt air and everything and they do last longer so the other thing uh to know about bearings is that the the edges the the shields come in three different sorts you can get an open one or you can get a dust shield with little metal caps or you can get the rubber ones which are fully sealed and then the oil lasts a lifetime so i usually use the rubber ones but if you're after low friction it's not necessarily a good idea here i've got the full seal on that one and the just the dust shield on that one so if i spin them both at the same speed because there's more friction in the rubber seals uh that one will stop spinning quite a lot sooner than the um one with the dust shield and there have been occasions where i wanted something with particularly low friction before i realized quite what a difference there was so mounting ball races um the inside of ball races are easily usually very straightforward an ordinary bit of bright bar will fit through the hole so i think this is a 20 mil bearing so that fits straight through now this bearing this is a pillow block this is one of the easiest ones to use because you can just bolt it to your machine whatever it is in mobility masterclass people often get a bit carried away using it so the mechanism which moves the frame has to be very very strong hence the uh big plumber's block down inside the bottom [Music] and the other advantage if i get a second pillow block on here is that it doesn't matter if the things are misaligned even at some crazy angle the bearing mounts will accommodate it and it's quite clever how it does this uh if i swivel this one right round and take it out you can see the outer is curved and similarly with the housing it's uh dished and that's why it enables the bearing to swivel around so nicely um pillow blocks also come in a in a plate style so you could mount mount a plate with your shaft running through it the two styles are amazingly good value well all bearings are amazingly cheap i i should have said i use just cheap ones i don't bother with the expensive brand ones so sometimes though pillow blocks just take up too much space then i have to make my own bearing mounts one thing i find useful is little bits of thick wall tube this is called england anyway gas barrel tubing so you can often get a bit of tubing that's uh a bearing the outer diameter of the bearing is just bigger than the inside diameter of the tube and then you can just turn it down on the lathe and if you do both ends you end up with a um with a very nice sort of uh two holes precisely concentric so they're properly aligned and then of course it's very easy you just weld the tube to whatever you want to another material that is useful for mounting bearings i find is delrin and it's it's easiest if you start off with a round bar because again you can just turn them down to the right diameter on the lathe and in this case i just uh cut a flat on the bottom of it to mount it so that's another one i use sometimes you do have to mount bearings on a flat plate i find it hard to get the boring bar on my milling machine to be very precise so a trick that i use are these things called tolerance rings so you drill your hole uh a bit oversized um it gives you it tells you when you buy the tolerance ring it it it doesn't have to be too precise it's quite a range will work with this you fit your tolerance ring in the hole and then your your bearing made a little bit of persuasion just tap it in place um fits in very snugly and the other advantage is that uh the tolerance ring does allow for a bit of misalignment as well so uh one drawback of bull races is that um there's a very limited area of contact between the inner and the outer race just where they touch the balls and so there's enormous pressure on these areas so this effectively limits the load that they can carry if you need a really a large load more than to reduce friction you're better off with a bush so something like this digger all the pins on the arm and the grab at the bottom they're all bushes rather than ball races one way you can increase the area on a ball race is to use rollers rather than balls so you can see there are rollers inside they're little rollers and they rub against the shaft and i i love these things because they take up very little space and um they run very very freely uh i i was amazed that you buy them without often without an inner race just the rollers and the outer race and they will run very happily just an ordinary bright steel bar so if i put a couple on uh this is a these are eight mil um roller bearings and i um it'll go on spinning for a nice long time uh and i've i just thought the shaft would wear also i worried that dirt would get in as they're not fully sealed with rubber seals but again that's been less of a problem than uh i thought and i've had some that have been then machines for over 10 years now one drawback with roller bearings is that there's no they can slip perfectly happily sideways there's there's nothing to stop them um slipping along the shaft um the timken company um invented a way of around this problem of making a tapered roller bearing and these are often used in pairs so uh the wheels of cars um often have a pair of tapered roller bearings these easily take tremendous sideways loads when you're cornering in a car another place i use roller bearings tiny ones is on cam mechanisms this is a roller bearing for a three mil shaft and what i quite often do is to put this through um a cap head stainless bolt uh they the bolts often have an unthreaded bit at the top and sometimes i have to run a die over it to make it the right amount of unthreaded bar left then you can just thread this through and it's a very loose fit because it's not an accurate three mil on the bolt but um but it does run very very smoothly so this makes a very good cam follower that's a better way around so now as the cam goes round the cam follower is um turning on the uh on the roller bearing the load is all taken by the roller bearing and so this dip here is particularly steep and so that's got to rise pretty quickly as it goes up and if you didn't have a roller bearing that probably wouldn't work before i leave roller bearings um there's one very unusual sort of roller bearing it looks just like any other roller bearing there's a little arrow on it and this roller bearing is called a sprag clutch it'll only turn in one direction and you might think what on earth use is that but actually i found them quite useful in my arcade machine particularly where people are turning hands i thought i'd have to give you an example to make sense of it um i'm just going to push this strag clutch into a bit of doubling so this is just an 18 mil hole in a bit of delrin uh and then i'm also going to need a handle to turn so just so now i've just got a rod a bit of bar and a bit of string to put this weight along so if i put bar through now attach my handle now what if this does it'll if i go that way nothing happens at all if i go the other way it'll pull the the string so if on a machine if people were turning that way it wouldn't do anything if they turn it the right way it'll pull the weight now the last sort of bearings i'm going to talk about is linear bearings linear bearings come with sliding versions and rolling versions so this is a simple slider um just a carriage that goes up and down an aluminium rail it's useful because it's very compact um but it's not perfect has a limited life well from that i draw slides and and i use quite a lot of these things and these these are rolling friction it was slight problem with drawer slides is that this carriage with the balls can get out of alignment that end is just slipping without the carriage moving so there's a but there's another version which has this clever bit of cloth that keeps stops them getting out of alignment i like these they are pretty good the two-ton school run has a linear bearing running on a long shaft inside to make the car go up it works very very well uh this is a lovely linear bearing this is the bit that was left over from the two ton school run if i take one of the carriages off the end you can see there are rows of little balls in there and and they move round well you might think how on earth do they do that and it is extraordinarily clever this is a linear bearing that i've stripped so this top row is uh in contact with the shaft the bottom row is right hidden inside the bearing and that's where the balls return ready to come round again they stay stationary on the shaft but all run round the back to join in again uh now the one drawback with the circular type linear bearings is that they take up quite a bit of space so um if that's a problem uh there are then these wonderful things these are rectangular section rail and the bearing is completely rigid in all dimensions so that's all you need to make an object move of course the load would be limited but for a lot of the things i do just the single carriages is perfectly adequate and you can get them in other sizes as well it's exactly the same principle as the circular carriage with the recirculating balls with experience it's still very easy to make mistakes so i thought i would end with one it's a machine i made a couple of years ago and made quite a mess of the bearings it's a miniature amazon warehouse where you have to rush around picking as many products as you can against the clock while walking it's the walking mechanism i have problems with this is the prototype it's really quite simple i mean you you there's nothing much to go wrong you'd think but after being on the pier a couple of months uh all sorts of things started happening an e-clip popped off a shaft half came out it's just a succession of things i was under the machine every month or so uh adding bits and pieces and trying to get it to work eventually i got it back to the workshop well that prototypes long gone i don't keep them so for this video i've made a small working model it took me a couple of hours um so that's the walking mechanism uh your feet would go on there it is very simple and each of these is a pair of bearings so i've worked out that the problem was that people particularly when they get enthusiastic um there's a very odd sort of side loads that get on imposed on the on the frame so you can actually see this shaft bend as i push it sideways and of course a heavy person can quite quickly do a lot of damage and it puts a lot of stress on these would have been the two ball races only 20 mil apart uh so quite a lot of twisting force on those those bearings well once i've got it back in the workshop um i quite quickly uh managed to think of a way around it so the solution was to space out the bearings at the top before they were 20 mil apart and i think in the final version they're now probably about uh 150 ml apart so it's a big difference so if i now reassemble my model um but the but the inner one is now fixed to a new support in the center there so that's the that's the new arrangement and i think you can see it's much more rigid to these sort of loads pushing it in and pulling it out just by spreading these bearings out from there to there and actually i've had no more trouble with the machine ever since so it's actually very satisfying well done we're delighted to offer you a zero hour contract at the fulfillment center i think perhaps uh the thing about experience you still make mistakes but when something goes badly wrong like this you don't think oh no it's hopeless you just think oh that's an interesting problem and so i quite enjoy it i'd be bored if things didn't go wrong really anyway that's enough of bearings bye-bye [Music] [Music] you

Channel: tim hunkin

Views: 284,896

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Id: LyRzGFHWnIU

Length: 43min 39sec (2619 seconds)

Published: Thu Apr 22 2021