How Fast Can We Spin A Titanium Skateboard Wheel? 

What would you guys suggest on how to get our RPMs higher? Our next three strategies are to try lighter materials (magnesium or carbon fiber), hollowed out wheels, and finally smaller diameter wheels. At this point those seem to be our only bottle necks, anything we’re over looking?

Should have just drawn a white line on the wheel

If you're asking if it would produce a sonic boom, that's a no. A spinning object doesn't produce the kind of compression force needed for a boom. A sonic boom is produced when air is compressed at a faster rate than it can expand itself. The wheel would have to be moving, not spinning. Since the wheel is a uniform shape, there's nowhere along the wheel for air to accumulate and compress. As far as producing a different pitch or tone, though... That's beyond me. I'm not familiar with that part of physics

I'm an engineer. The limiting factor on wheel RPM is parasitic drag from air resistance and bearing friction; not the weight of the material. If you had low enough friction, the outer surface would achieve the same velocity as the jet. The best way to achieve lower air drag is to polish the surface of the wheel, and place the whole contraption in a somewhat airtight cylindrical container, so a rotating mass of air can form around it, instead of accelerating the stationary air in the room. But by far the biggest improvement could be had by removing the grease from the bearing. After all you only need it to work once.

This is the type of unhinged video that got me hooked on youtube back in its early days.

Take it from a guy who mass machines titanium on the regular, whatever speed you think you should be running at, halve it. Most machinists who are unfamiliar with the material go way too fast and destory any cutting edge you once had. Bi-metal band saw blades will cut it but have to be sharp and run slow, 300 series stainless slow. Cutting it on the lathe, use carbide and go a hair slower than stainless steel speeds.

Try making a magnesium wheel but press fit a titanium sleeve around the outer diameter to give it more strength. Should hit crazy high RPMs as magnesium is significantly lighter than even aluminum.

You could possibly increase the max speed at the outer diameter by creating a tophat shaped wheel. Point the waterjet at the smaller diameter section and the larger half may move faster than the water from the jet just like higher gearing in a car. It will however be harder to spin.

This is the first video of yours that I've watched and while waterjet videos don't exactly peak my interest the comedy/editing will keep me watching haha, keep it up

Bearing will affect the sound/harmonics. Can’t use the previous frequency. Next time don’t anodize it so there is more contrast for the meter!!

First, use a silver or white line for contrast to get the Tachometer to work. Also, the titanium wheel would most likely have a different resonant frequency especially since you changed the bearings. Bearings are usually the noise maker anyway and since you upgraded them the frequencies almost certainly wouldn’t correspond to the same RPMS. You very likely exceeded the RPMs of the aluminum wheel with this experiment. Keep it up, i love this stuff, it’s why i like engineering!

2:30 I think it also helps that they're constantly showering the workpieces in hundreds of liters of coolant per minute

I like your sense of humor. Makes me feel at home.

Since the titanium isn't gonna get gouged out as much, to maximize the speed you are gonna want to have it hit the wheel further out so the water stream is hitting at an angle closer to tangent of the surface of the wheel.

This whole channel feels like a post-apocalyptic Waterjet Channel where a lone survivor stumbles upon the location and partial ruins of the Waterjet Channel and started making videos to keep from going insane.

Great entertainment. I can tell you have working around this shop forever as your ability to cover all ideas or theorys with tests along with funny spats makes this very fun to watch! Great job!

The trick to ti on the band saw... 1 flood coolant, 2 brand new Lennox blade! 3 turn the band speed as low as it goes, I don't care if the Internet gave you a different speed. If it's a variable speed, turn the adjuster till the band stops moving then turn it up till it barely works. If it's a multi speed, put a vfd controller on the motor to slow it down. I've been able to turn induction motors down to 15 hz which is 1/4 speed. It might even go down to 10hz. As for the lathe, If it's a fairly heavy lathe you can take pretty heavy cuts. If you have lots of cooling like a CNC you may even be able to go a reasonable RPM. Ti likes CNC lathes. Continuous cuts are good. Thick chips are good. Prefer a feed/rev relationship over higher rpm. Thin chips are bad, high rpm is generally bad unless you have the cooling capacity. For a manual lathe use power feed and if you want to be safe use a very low rpm. Always use new sharp tools. For a milling machine, well if it's CNC use climbing cuts and a fixed feed rate, no slowing down for corners. Use healthy oversteps. A thin chips will harden the work and break the cutter faster than an abrupt 90 corner with a heavier volumetric load will. If you are manually milling, you may be able to face it. But good luck profiling it. It hates conventional cuts and heat. But climbing cuts heavy enough to punch through the work hardened surface will likely draw the work into the cutter. You can try locking the gibs and letting the leadscrew pull through the friction. But a CNC with ball nuts is just a more reliable way to work with it.

The peak frequency of the fundamental tone on the Titanium sample reached a maximum of 953Hz (on my spectrogram). That equates to 57,180 RPM. I'd throw out your tachometer, and ignore any previous readings. Working out new speeds based upon the previous rpm measured with it will be giving falsely high results for everything. They can pick up false signals (harmonics) and give you twice the speed or more. Here's my measurements: *Resin + Titanium Shavings:* 429 Hz * 60 = 25,740 RPM *Copper:* 332 Hz * 60 = 19,920 RPM *Titanium:* 953 Hz * 60 = 57,180 RPM

Some bullets spin close to 300,000 RPM in flight. It's crazy how they stay together without exploding as soon as they leave the barrel.

10:11 If you had the world's first 100% energy transfer device; which would technically be breaking the rules of thermodynamics simply by the small distance.

Where did the original guys go?

my guess would be the tachometer functions on contrast to generate a differential pulse wave, then just spits out pulses per second to pulses per minute to get RPM, the blue anodization may have hindered the contrast (red laser), so maybe try a white spray paint and the sharpie black line, a wider black line may be beneficial because at higher RPM the contrast would produce a fainter pulse signal for a thin one with respect to the sensors sample rate.

I hope there is a part 2 to this video where you try different kinds of lead or metals. This was top 3 of videos you have ever done in my opinion. I want to see 2 bullets fuse now and hope you get it done. Good Luck and God Bless

Those laser tachometers usually come with a few little reflective stick on tape markers for such cases like this

Here's an idea to get the tachometer to read. You guys electrocuted it so it turned blue, well dip half of it In the solution so it becomes a different colour than the other half. I don't know how the tachometer exactly works, but it's how I think it does, it should be able to give a reading. And it won't rub off like the sharpie did.(I have no idea if it will actually work but it's an idea)

Im sure the harmonics would be completely different between the materials and bearings used. The pitch used between them for estimates can't be reliable

you calculate the upper limit on rotational velocity for the titanium wheel. the wheel will never spin faster than the surface velocity of the water hitting it. so you use the formula to convert surface velocity of a wheel to rotational (using the radius of your wheel) and that is your absolute upper limit. you know it will actually be less than that because the frictional forces of the bearing and the air will slow it down. you can combine all frictional forces into an overall coefficient of friction. you can get the drag coefficient for a stationary spinning wheel from an engineering data table, and you can get the coefficient of friction for that bearing from the supplier (or just do ceramic on ceramic). my WAG would be the actual rotational velocity maximum after friction is probably 80% of the frictionless value. The slowmo doesn't actually tell you the whole picture though either. it appears to be spinning 3 frames for full rotation, but you could be spinning a lot more than that. the sample rate of the camera could be relative slow such that the wheel spins multiple times per frame and simply shows up in a different location. there are a LOT of formulas for calculating and accounting for this to try and get a range of possible values. also the frequency is going to be tied to the density and volume of the disc, so it wouldn't map perfectly to the aluminum disc

Make sure it's perfectly balanced, I could tell just from the hand spin it was off balance since it ended up swinging back and forth around the heavy side. The imbalance is going to cause the bearings to wear unevenly and cause more friction. Use a hobby propeller balancer to get it as close as possible to perfect. I would also suggest rounding off the corners and trying to shoot for a flattened sphere shape to avoid air turbulence. Good luck!

Legend has it the wheel spins faster than Sonic

I wonder if this sort of thing will end up being turned into an actual manufacturing process to go along casting and stamping ...

Love the strong bad reference

7:17 nice pun with the earth/ground wire!

Haven't seen Strongbad in a hot minute

If you're gonna keep bumping up the RPMs, you'll need a better measuring method. Get a very small disc magnet, drill a hole in the side of your wheel (not the circumference, it'll get thrown off, just the side, as close to the bearing as you can to avoid imbalance), JB weld it in, balance it, and then use a read head pulled out of an old tape deck, hooked to an oscilliscope, to measure the speed of the wheel. An optical tachometer just isn't gonna keep up at these speeds, although you may have better results spray painting it black, and then adding a retro-reflective white strip.

Holy shit man You deserve your own show!! This is awesomeness🎉 You sir have just gained a huge fan:) Not like a fan fan, a fan😅

Some good precision machining the bore, and balance it when your done, the balance will greatly improve your rotational speed before failure. This very cool, thanks for sharing. Cheers!

It's not a waterjet channel video without a taste test. Good job.

you could cut out a little tab/wing on the side of the wheel that will receive air resistance instead of water, possibly allowing you to test the sound barrier idea

If you continue like this the universe will implode

This is the thing that keeps me up at night. 😂😊

I think fully precision machining the wheel is gonna end up being a needed step to really optimize it, that oughta get some interesting results! And I wonder if machining a groove in a resin wheel and then encasing wire might be cool? That’d be a fun comparison to this wire one! Ye could even try making a batch with different material wire, maybe?

RIP Dr Pepper who made the ultimate sacrifice for this video

You have few things you need to work out with yourself but other than that you are somewhat entertaining to a guy who never smiles. Take that as a compliment...

Finally, someone tackling the BIG questions!

Try using a fan to clear the water mist Also, thread a reflective bolt into the side so you can get an accurate tachometer reading.

Ok that was really cool

Mill it to relieve weight, machine sections of super fine grooves to catch the water, machine the rest of the surface with divots to reduce drag.

No amount of money would make me get my hands that close to a screeching titanium cylinder.

I got about 56300rpm using a spectrum analyzer on the audio. 1 rotation = 1 period/rotation. It made a fundamental tone at roughly 938hz * 60.

Check out the fitting of bearings on good downhill longboard wheels. Bearings are always a super tight fit. Also taking advantage of how durable titanium is, you should hollow it out a bit. Like a titanium whiffle ball. I think the groove it cut in those resin wheels really affected how it was spinning.

Your presentation and editing have gotten better... Keep it up

3:10 the forbidden flashlight

Have you spun nickel metal yet? Would also be cool to see the titanium wheel lightened up and see if you can increase that spead. Maybe Nurle the outside too for extra friction with the water and media. Awesome video, now i need to convince my company to let me try some experiments 😂

Next time use Liquid Paper. A black Sharpie over a dark surface won't work.

Do you put any classic cut in the waterjet or just run pure water? Have you tried the opposite (with/without the classic cut). Also do you use any sort of softener in the water?

Was not expecting a flashback to my childhood 1 minute into a water jet channel video

Does anyone know what happened to the original hosts of this channel?

I broke the titanium rods in my back😅

My father owned his own machine shop for 22 years. He took on a lot of aerospace projects. He too did not like working with titanium. I remember the companies always wanted any and all materials that were cut or machined off for recycling

Great video man. I wish I had access to a shop and materials to do goofy fun stuff like that.

if you were to machine rutts in the wheel you may get higher speeds since the water has something to grab

"How do we measure that?" With white tape or paint. Damn. Also, SURELY you can set up a safe system to read the RPMs without having to run up to it after it's already slowed down a bit. Danger isn't entertaining regarding these types of tests...at least not to me.

Holy Sh*t you just made me so damn happy with the "Will it Blend?" reference.

Might drill small holes into in the side and through the wheels, taking out material to lighten it up and also creating a surface that you might be able to get a reading. Just make sure every hole is precisely located to maintain balance.

damn thats fast

The Cheat is to the Limit, cmon fhqwhgads .

I didn’t like how few cuts i had on my hands so i decided to change that😂 genius!

have you calculated the water speed to know if with this pressure it even possible to acheave soun barrier

Make a wheel out of sodium metal

nice job 😁

There is no way i would have stood close enough to get the laser reading. That looks terrifying.

There is a fine line between genius and insanity, good luck with your travels

It's just not the same without Licky & the Bald Guy... rip

Magnetic mish metal girt is made this way. the wheel is cooled with liquid/gaseous nitrogen, and then a thin stream of molten metal is poured onto it. At the appropriate speed and mixtures, magnetic powder is formed. General Electric patented this process, decades ago. Used for many other similar manufacturing techniques.

Love the slapstick interludes, lad

Used to do this with series motors. Magnetic current is just as powerful as water. The whole motor comes apart with the G forces.

5:28 Interesting fact: In high-power rocketry they mix titanium sponge into some of the solid fuel motors and the result is a beautiful shower of sparks from the rocket as it blasts off into the sky.

Yes, the drag on the wheel exponentially increases, the faster it spins. I would not rely on the tone of a wheel of a different material to estimate the speed of the Ti wheel. Measure it optically. If you have to, use an oscilloscope to probe the IR photodiode on your chinesium harbor freight tachometer, then count the frequency with the oscilloscope. Adjusting the position of the wheel vs the stream might help you in two ways 1. Optimizing the momentum transfer from the water to the wheel by 1a. Getting as close to tangent as possible without 1b. Reducing the amount & duration of water contacting the wheel before flying off 2. Reducing the friction on the bearings by reducing the downward force from the stream (the closer to the center of the wheel = more radial force & friction on the bearing and the less torque/ tangential momentum transfer to the wheel). Probably the best thing you could do to make this experiment easier is scuff a stripe on the wheel to reflect, sharpie the rest black. Setup your chinesium tach on a chinesium tripod, tap into your chinesium tach photodiode, connect an oscilloscope, monitor from a safe distance. Then start playing with your... Position of the jet. Then you're set. Bet.

The mass doesn't play that pivotal of a roll due to the upgraded bearing, at those speeds its main goal is just keeping the wheel balanced.

Sounds crazy! Use 1/2 white and black too see it better. Love the video

Whether or not it passed the sound barrier depends on the point of reference. From any given point of the wheel's perspective, it definitely did as it moved through space

You should machine a spot for a magnet and use a hall effect sensor to get the rmp. It would also be really cool to see the power you could genarate from it.

I work with CNCs, and one of my customers mass produces medical components, many of which are made from titanium (since it’s 1 of 2 metals that the body won’t reject), and it’s really not that difficult to work with compared to some other really hard alloys. Just keep a steady stream of coolant on the tools, and if you can get that coolant at a really high pressure, it’ll help break a chip. Also, having the right inserts for the job really helps.

There's a similar problem working with Inconel steel -- it's stupidly heat-resistant, AND hard. So mechanical cutting is a pain-in-the-ass... but so is heat-cutting. They use it for high-heat, high-stress turbine blades and silencer interiors.

You want to make it go really really fast using the same wheel and setup? Put the wheel on a slight tilt so that the water jet can it the side of the wheel. Then accelerate the wheel to the maximum (until frequency stops climbing) like you do here, but then move the water jet head to the side of the wheel starting from the outter diameter, and moving slowly in the direction of the center. The closer to the center the faster (RPM) the wheel will go, because the water speed is constant so is the surface speed wherever the water hits the wheel, and in a smaller diameter that means higher RPM. Just remember moving the jet slowly because the inner it goes the more rotational inertia it has to overcome in order to accelerate the wheel. To mesure the RPM you can paint a white stripe in the wheel, or paint the side white and put a black stripe.

Yes it would count as breaking the sound barrier because the outside surface of the wheel is indeed traveling, maybe in circles but it is traveling through space at a certain speed.

What you can do is cut the titanium wheels front to a slight conical like face instead of it being flat so that as the waterjet spins it the more in it goes to the center the faster it'll spin (may possibly break time and space with this method lol). Great video!

How fast things in the wild spin 😂😂😂 ya got me on that one, haha

it did not read the speed because of the color diffrence , you can glue a white paper with a dark line on the side of the wheel. (tho in this case the water wouldnt help much.) laser readers work much better if the line is much darker than the surface , but in this case theres not much you can do but paint the wheel white. a white line would probably give somewhat innacurate reading duo to the laser being red .

when you used the titanium shavings as a moustache, i subbed

Assist with air and paint it black with a white or silver mark to measure RPM . Get fingernail polish that matches the silver tape that was supplied with the tachometer. The air will serve two assisting properties. The motion and lower the pressure due to that Bernoulli thing.. You could also use an air bearing for reduced friction. Make a steel spool that fits the profile of the titanium and pump air out of the center of the spool. Replace any grease the bearing might have with WD-40. Good Luck

The strong bad reference earned you a new sub. [:

Love the strong bad reference!!!!

From someone that used to be a cnc machinist that worked with Titanium we used coolant / lubricant in all aspects , Ban saw had coolant/lube , As did the lathe and Mill and even then sometimes the machine would still catch fire if the coolant/ lube level was not paid attention to over the runs. Yes Titanium burns hot and it even requires a special extinguisher to put it out.

I need more water jet versus different wheel experiments.

I'd much rather watch *you* wrestle with that stuff. Thanks for the work so we could watch this.

first video ive seen, next level commentary

0:57 strong bad fqhwgahds reference???!! as a former homestar runner addict you got me good

I think if the jet can move slightly so that once it’s spinning fast, you can make the jet that it only hits side of titanium. May get that speed. Nice video, new sub. ✌️

When I saw the 1st video with the wheel stretching, Ive always wondered if it would be possible to stick something in and turn off the jet so the wheel closed around the the axel and the object and what would happen. Would the wheel throw it out? Cut it like an inveted saw or snap it? Or maybe it would stay in? Would be interesting to find out.