Simplest DYNO for RC Engines! - Prony Brake Dynamometer! 

This guy is about to have a whole rc car garage, what's next an alignment machine?

There's nothing quite like the hiss of tooling metal. So satisfying.

Self integrity is just one of the reasons I enjoy your channel. Thank you.

You need to make sure your force measurements and RPM measurement happen simultaneously. Also, peak torque almost never happens at the same RPM as peak power. Having finer control over the braking force applied would be nice. What about making an electronic brake using a BLDC, a three phase rectifier and a rheostat. Another option would be a pump (fixed displacement) attached to the crankshaft and a needle valve. The body of the motor or the pump would be mounted to the arm that goes to the scale. You would probably need one support bearing at the opposite end of the motor or pump. By varying the brake force the speed of the engine could be controlled at WOT and if the engine speed is not changing then the torque generated by the engine is the same as the torque absorbed by the brake. Take a reading and adjust the brake to change engine speed in 1000 rpm increments. You could develop a whole torque curve this way and then calculate horsepower.

There is a misconception in this attempt of yours to measure the torque the engine is producing. When you clamp the crankshaft until it stalls, you are measuring all the inertia of the engine to brake to a complete stop after reaching the 6500+rpm. To measure the actual torque the engine is producing you need to progressively clamp the crankshaft axle until you reach the steady state condition. The value measured will then be the actual torque that your engine is producing. Cheers and keep up with the awesome work you are doing!

Johnny's saw struggled for a sec on that second cut. Next episode: 4 stroke wood saw. Brand new supercharger.

I am a dyno technician. And i have never thought to test rc engines like this, this is smart! This is a "load cell" dyno. How about an electric motor or something to provide resistance?

ΓιάννηQ μπράβο για τις φοβερές κατασκευές σου, εξαιρετική δουλειά με πολλές λεπτομέρειες και αποτέλεσμα. Συνέχισε να μας εμπνέεις μικρούς και μεγάλους!!!!!

Now THAT is a nice contraption. Real data from real measurements. Kudos! PS: Power measurement and calculations are part of my profession. Here's a few tips: What you were measuring now was peak torque, and peak torque is always WELL below peak HP. Second thing that went wrong, is that with full throttle, if you bog down the engine, such a simple carb will most definitely not hold mixture, so your actually measured value will not represent what the engine is capable of. Richen up your HS needle a bit and I am pretty sure you will see higher torque values right before stalling. Reason is, dropping RPM reduces intake vacuum, and that reduces fuel draw, and your mixture will lean out because that throat diameter is designed for 10+K, and you are running only 6K. Now, your peak HP will be around 10, maybe 11 K So if you want to know your peak HP, set the brake for around 10K RPM, then peak the needle and if necessary readjust the brake to maintain around 10K. Now try to get torque readings in steps of 200 RPM between 10 and 11 K, and I am pretty confident that you will see higher HP numbers. Realistically, I do not expect 0,5 hp, but 0,4 should definitely be within the range of what is possible. My own 5 cc fourstroke runs on gasoline (less power than Methanol) and manages about 0,3 HP @ 9,5K On methanol, 0,35~0,4 should be absolutely possible.

Allways clean and tidy, never make a mess, nice to watch

Integrity is So Rare in RU-vid Videos. Thanks!

It's not unfair, it's a valid measurement as long as you use it your own engines to see improvements.

Wow no intro or nothing it’s just straight into action, how good.

Love the way you set all this up. Bravo my friend. You are teaching me new things as well. 👏👏👏👏👏👏

I always enjoy and share your videos since I've been in the hobby of radio-controlled 4 over 30 years and wish I had the equipment our friend here has. Enjoy your RC cars my friends and stay safe with this virus. RC4LIFE 👍👍😎💙😀

Glad to you see finally did this to test engine performance.

Wow I would really want to have one for my homemade RC cars!!

A significant portion of the engine's output may be lost to heat at the wood/metal interface. A lot of people have suggested an electric motor as a load, I think it's a good idea too. The trick will be calibrating it. Possible calibration procedure: - attach a pulley to the motor - wrap a string around it several times - tie a known mass to the string - drop the mass off the table The falling mass will provide a constant known torque. (mass * pulley radius * acceleration of gravity) If you record the drop with a camera, and have a meter stick behind the mass, you can measure the acceleration and velocity of the system. The input energy can be easily calculated using the distance the hanging mass fell. There's a few more math steps after that, but nothing too crazy.

Tiny engines are so cool

Hey, you are part of my inspiration for engineering school. Keep it up!

NICE!!! I just got my FS S100!!

This measurement is really cool! Shouldn't you place another bar of the same length and weight on the opposite side of the scale to prevent gravity from acting on the scale? Because the weight of the part on the scale can give the wrong measurement when your engine is running.

One of your simplest creations yet still works awesome!

I would love to see this done with your rotary motors when you have the correct fuel.

Very cool! Can't wait to see more engines get tested 🙂

Friday afternoon, good bowl and a JQ90 video, I am all set!

Morning Johnny

Love seeing your projects keep up the great work!

If you're after a mini-dyno, another interesting thing to look at would be an eddy current brake - using the lorentz force as a brake. It's substantially more tuanble than a direct mechanical brake. A spinning disc of aluminium within a strong magnetic field produces eddy currents within the aluminium, the eddy currents themselves also produce a magnetic field that opposes the rotation of the disc (which is the braking mechanism), the result is a torque transfer to the electromagnets, and heat in the aluminium. A few ways to attack this in your application would be: (1) to get a bunch of neodymium magnets and modulate their proximity to the disc, though the torque would need to be measured through the structure that holds the magnets as well, which complicates the construction difficulty. (2) to get a bunch of electromagnets off eBay, and modulate the current within them with (an adjustable) constant current power supply - this may be easier to facilitate the torque measurement, but would likely cost more if you don't already have the supporting equipment. Though it is my preferred solution, as I've been designing a system like this in my own endeavours (with 50cc engines) because (if you're ok with microcontrollers/etc...) you'll be able to perform basic run-and-hold tests with an RPM feedback into a microcontroller. The microcontroller would allow the engine to run to X rpm, and then actively track and adjust the electromagnets to prevent it going any higher (thus allowing the engine to run under full load without revving out). With a bit more development after that, you'll be able to do full dyno runs and graph the results. (3) use a brushless DC motor to generate power. By directly hooking up a motor (as a generator) and varying the electrical load on the generator. You would want to measure the torque transfer on the generator chassis and RPM, don't even worry about measuring the electrical output power to gauge input power (though it might help to confirm your findings) - using motors as generators is notoriously inefficient and the output electrical power wouldn't be an accurate number.

Απλα δεν υπάρχεις!Οτι και να πω ειναι λιγο!Τελεια δουλειά!!!

Your math is off. Hp= tq x rpm / 5252 Using the force measured at 3:57 - 3oz @ 1/2 ft = 6 oz/ft or .375 lb/ft .375 x 6600 / 5252= .471 hp. Great work and thank you for the quality content.

Excellent video, my friend respect from Venezuela.💯👍🤘💯💯💯

Es es hermoso Tu arte me haces llorar cada vez que me hablas lo que estás haciendo no puedo comprender tanta maravilla No tengo más que agradecimiento Gracias por todo amor que nos obsequia y locas con ternura jamás volveré a ver al metal como una cosa muerta si no como que me grita para revivir

That is very simple very genius design. congratulations!

I've been wondering how to make a small scale dyno for a while now. Great job.

Already 20 comments after a minute!! 😲 Love the vids bro.... keep up the great work!!

Your measurement of the arm should have been from shaft centre to the point of contact with the scale. A pointy-er pointer would have been better to keep control of the point of contact better as well. A pump or a eddy current brake is going to be the only thing that’s going to give you anything like a reliable result or a situation where you can hold the load long enough to read the scale. Did you read my comment on the centrifugal supercharger? A plenum could be the solution there. Really nice machining work, you are very patient and skilled. One of my favourite channels.

Would really like to see more of this

I would have never thought of something like that good job man

realy cool idea!!!👍🏼😉👌🏼

Good job my friend👍🏼👍🏼👍🏼💪🏻💪🏻💪🏻 I'm from indonesian present

Wow,VERY interesting and unique idea here!!! Thanks for posting this one JohnnyQ90!!!

I needed this today!!!!

That would interesting to ad a cable to a clamping mecanism, you would have a more precise way of testing the engine at different rpm with two levers

One of the things I noticed that make power is the heat range of the glow plug, it’s the same as to advancing or regarding ignition. Most useful when using high nitro content fuels.

There is a bit of inaccuracy due to you having to screw those in, it does offset the result a little bit. But still love the video, looking forward for more.

2:22 Actually, you want them in kilograms and meters...

This is actually a genius way to measure power

Very hardwork dude

Yep we gotta see more testing. Plus the testing on your engine upgrades.

I really wanna see you Dyno all the engines you've had especially the supercharged twin and 2rotor

The arm distance is actually going to be a little over 0.5 ft because you need to be measuring to end of the 3D printed point not to the base of it. Putting that point there essentially puts the arm there. may not make a huge difference but in something like this it's worth noting.

I hope you Dyno the Turbocharged twin cylinder next!! awesome Video

Suggestion: Instead of using wing nuts and possibly adding weight to the scale with your fingers touching the wing nut. You could mount a high torque servo in some fashion to the brake and then use use a simple dial adjustment to clamp down on the brake for real precise braking and measurement. Just an idea I came up with watching it.

Great idea

When you are using horse power as a unit, could you please also show the value in watts? It would make so much more sense to me, as these engines are more comparable to small electric motors than big IC-engines.

Amazing video as usual!

Always a good day when when a of yours video is out. Awesome work as always, keep it up 💪

Could you finger on the wing nut be causing a lower reading..?

I think and electric motor with variable resistance would be a much easier and more accurate way to do this. Because you are only measuring such small output power it should actually be quite easy.

Hi Johnny, for a coorect mesure of the power you need to make it every time at full trottle, and adjusting the rpm by clamping the brake, otherwise you do not measure the maximum torque at the various rpm

There's a few reasons this is inaccurate. Horsepower isn't just RPM*torque, it's torque x RPM / 5.252. Also you're losing a huge amount of power on that method of measuring. Most of it will be lost to heat/friction on the shaft.

I can't say I'd trust those scales as a precision Dyno. The clutch housing might be an easier way to get better figures. The point where the engine output meets the drivetrain. This way you can make some sort of lazy clutch where it's always under friction (maybe without springs) then when you rev. it will up the load on the bell housing (connected to that arm you made)

Great job man!! Your videos really helped me a lot :) :) :) :) :) :) :) :) :)

Can you do it on your twin 2 stroke nitro engine? I was hoping that you will do an rc 1/10 truck build using the engine

I really enjoy your channel and am in awe of the things you make, but I have never tested any internal combustion engine to a stall. HP is measured at a constant rpm. Say 6500 at full throttle. Then measure the force. Testing to stall is Testing to beyond what the engine is capable of doing. Try holding a set rpm of 8000 at full throttle and see what the scale says.

That’s awesome

Check if that mdf has constant friction/temperature. Seems like it could adjust more gracefully. Maybe larger diameter shaft and something else for braking material between metal/mdf torque arm?

You can calculate the HP mathematically also. The formula is HP = Bore squared X stroke X RPM and divide by 18000, I don't know the bore and stroke of your engine but this is the formula vehicle manufactures use to calculate the HP numbers for advertising and emission data.

Great job, i've wanted to see a dyno for awhile. can you use a R/c Disc brake for better control of drag? (so tightening wing nut doesn't effect reading) and i would love to know if your exhaust mods add power, and i would definitely love to see some numbers from your Blower(s). thanks for the video.

Nice job bro.

no views but 40 likes already!!! nice

You could use a brakedisk.

Great idea👍

You can have the engine spin a motor to create a generator then have known load and measure the watts... BTW where do you get those tiny boring bars?

I'd expect any manufacturer's specs to be exaggerated, but 1/5 seems excessive. The fuel could make a difference, but there may be some measurement error there. Given the small scale, small errors can amount to huge variability in accuracy. Excellent concept, just a bit of refinement may be necessary 👍

I'm glad I stayed late 🔥🔥🔥

Nice build. I have herd stories of professional racers using 10% nitro fuel in races when 20% is the norm. I think they said that they were competitive because they increased the engine's compression to compensate.

it would be super intersting to see how much of a difference the right fuel makes

Hi, aweomse videos as usual, if i can give an advice: Don't use electronic scale, delay between actual mesure and display can be very different, this will lead to false measure and calculation moreover with small numbers where it makes HUGE differences (0.1 or 0.2 over 3 is already much diff) . Try to find a mecanic scale, you will notice the diff :) . Keep doing great stuff !!!

I would suggest making a small disc brake setup to load the engine with and mount the cable or servo actuated brake on the lever arm to push on the scale. You'll be able to load the engine without directly touching the arm and affecting the measurements. Also it'll involve some cool machining and fabrication.

The Amazing skill...

My Little Prony: Friction is Magic

This setup seems more suited for a static load like measuring the force it takes to break something. Im guessing real dynos have rollera for a reason so you can see how the engine behaves at different rpms

Interesting! Works very well for a proof of concept. I think if you were looking to do an upgrade at any point, a road bike brake disk and caliper would make a more robust and sensitive system. Also, you couldn't need to get so close to the rotating assembly.

My 2 ideas for the dyno brake: Use a conductive disk that spins with the crankshaft and place a stationary electromagnet behind it. Alternatively permanent magnets at variable distance. Should give a nice induction brake. Second option: Buy a large RC brushles motor, spin it as a generator. Attach a 3 phase rectifier, pwm controller and a resistor, then you can controll the braking torque with the PWM. The first option is probably easier and more scalable if you want to measure sth larger

You may want to change your center shaft to a larger diamater. This will decrease sensitivity to clamping and increase surface area allowing for more mental volume to absorb heat a little better. The prony brakes I have used typically have a hollow cavity inside the metal part to allow for adding watter to help with cooling.

Theres a worrying rattling sound 0:30 like the machine is wobbling or have bad bearings? Or is that normal?

This is what I live for

Did you apply the conversion constant? Horsepower isn’t simply pound-force x rpm. You have to divide by 5252 and I didn’t see you mention this. Also you are measuring torque force at 0.5 feet, so this also needs to be factored in. You might have done this but I didn’t see any mention of it.

Nice very smart

That’s a neat low-tech method, but instead I’d have made a simple (arduino) USB/serial datalogger, using a photo-interrupter and a load-cell ADC circuit. Should get me a whole torque curve from it. Planning do do something similar myself for a BLDC, though my motor’s torque is enough to send it into orbit, so I’ll have it vertically mounted with rotationally symmetric spars connecting the brake housing to the motor housing. Using an identical motor as an EM brake, because I have two of them anyhow, and it lets me easily dump all the heat into a water tank.

Try making mini disc brakes with calipers, I think it's a good idea!!

Wish to have lathe..

absolute genius... need a RC turbo 1.9pd lmao

Just amazing 👍 it

Oh, a prony brake. Neat.

Greetings my friend I'd Really like to know if I gave you dimensions four small RC parts aluminum possibly would you consider resale? Because I'm blowing away of your skills and I never missed the video you always upload and always share many of my friends follow you now I made my own custom parts for years but wish I had the machines. Please let me know since I'm dead serious.. 👍👍 - Godspeed my RC friends -

0:07 Can you record a thermal image of this please ? How hot are that blade like thing and the cylinder ?

I'm trying to design my own RC Dyno for bench testing 1/5 electric RC. I will be using gravity rollers mounted to a frame. there will be a pair of rollers between each wheel and I want to be able to adjust the resistance of the rollers but do not know what I need in order to also measure the resistance of the roller to create a "load" on the RC. I would also want to be able to capture the wheel RPM and eHP under the specific load. What is this type of attachment called and where could I find a power meter/analyzer like this? I need help and you are a genius with this stuff! My Goal is to be able to see how fast my RC will go under a specific load of resistance. And knowing the actual eHP output would be also very helpful since rated output is usually not even close to actual power output. Thanks!