Arlo's DIY inertia Dyno

Ok so this is it I have been working up to this for ~8 years and have had plans for my own dyno since I was about 18 (~16 years ago)
I first made a RC car dyno out of a couple rollers to get a feel for it. I ordered an electronics set from dyno 46 and it worked ok on the right computer for a while.
Then as I was shopping for something that would suit my needs I was looking pretty hard at Performance trends products when Dr.Bass showed me the simple dyno free to use software. I have since worked with Damon form simple dyno and added a current sensor and voltage input via a Arduino uno board. I can configure the inputs for temperature and Air fuel among other things. So far everything is working pretty well I just used a VR senor on a motorcycle sprocket for the signal this feed into the mic port on my laptop I wanted as many teeth per roller rpm as the software would allow for a better low speed full power start reading with the electrics.
https://sites.google.com/site/simpledyno/home

This is the very start >[youtube]XdjQ445WoJw[/youtube]
This is the rc dyno modded to run scooters. > [youtube]09dtmRzcRLQ[/youtube]
I used the compressor motor running though a 50:1 reduction box then with a chain and sprockets to get the rpm where I wanted it!
Diy machining who needs a lathe? > [youtube]6PHoKwk8h_A[/youtube]
And the final knurl finished today. > [youtube]7yDuN-bgXTo[/youtube]
Drift trike on the dyno.> Also before putting a better knurl on the roller. [youtube]kC97BLvGr7s[/youtube]
This is a run with the ysr before adding the better knurl which required very tight strapping on the rear wheel to keep it from slipping. That will also contribute to the 4000-5000 watts at max speed and full rpm with out any more acceleration at the end of the run.
[youtube]3Z2WcchbHXU[/youtube]

This is awesome! and even a low torque sensing sprocket.dang cool .. great for torque numbers. I think its lacking in electric power readings.

Very nice job Arlo! I have to find myself a pair of those "safety sandals!"

bigmoose said:

Very nice job Arlo! I have to find myself a pair of those "safety sandals!"

Click to expand...

LOL thanks. Last Tuesday I was in my bare feet with the father in law helping pressure wash the pool and roll it up, when I walked down our sharp cement stairs and didn't step out far enough and sliced the heal open on my right foot so the only way I can do anything is with sandals on.

Hey guys I need to add a brake... Mostly to slow the roller down but it would be cool to add a known steady load at a given speed so maybe a eddy brake?
With the eddy brake on my friends dyno in Edmonton he could use it to start a motor (bike or sled) because it would spin the roller up for him. This would be handy for karts and some of the motocross bikes I will be tuning.

Anyone know about this? I work at a bike wrecker so I can get all kinds of brake components for free but the eddy brake... Would I be able to use a induction motor or part of it?

So I'm really thinking about making a couple spools of wire to make a eddy brake. I think the best way will be on plastic spools with copper wire so there will be no drag from residual magnatisim when I dont want it. As for a measurement of the load I should be able to measure the twisting force on the eddy brake it self to know the toque right?

Arlo a true eddy current brake will not work as a motor.

Now you are great at experimenting. Take an alternator rotor and put it inside a piece of aluminum pipe. Try to have a tight gap. Power up the field and it will induce recirculating currents in the aluminum. The aluminum will get hot. Load will be sort of proportional to field current and rpm. If the small alternator size works, then you can scale up using a wound rotor from a synchronous motor.

A couple of years ago I posted some eddy current brake papers on a thread that Jeremy Harris started. I'll have to try to find it.

OK Dave thanks I will try to find it. But I'm thinking spools of wire on the ends or outter dia of the rotor and limit the amps to control the drag. I will post pictures soon I have a feeling the force will be Dependant of rpm and current not just current because the slip will increas as rpm increases.

Great work Arlo. What's the voltage and current at peak power output on the YSR? I see the 295A, but I don't know if that occurred at peak power out. I see max voltage, but I'm looking more for minimum voltage.

I know you guys used to tuning gassers always focus on peak power out, but while peak power is interesting to me, it doesn't become all that useful without knowing power input at peak power out.

John in CR said:

Great work Arlo. What's the voltage and current at peak power output on the YSR? I see the 295A, but I don't know if that occurred at peak power out. I see max voltage, but I'm looking more for minimum voltage.

I know you guys used to tuning gassers always focus on peak power out, but while peak power is interesting to me, it doesn't become all that useful without knowing power input at peak power out.

Click to expand...

The voltage and the amperage on the battery side are logged into the dyno program and are graphed out with a option for efficiency curve. So far total system efficiency was ~67% as a good average. I will be testing the new controller build asap. See this thread for further controller discussion. > http://endless-sphere.com/forums/viewtopic.php?f=30&t=35387

The efficiency curve for that run from 0 up to 15.1hp out sounds interesting, but at a minimum I'd need efficiency at peak power out. Average efficiency doesn't do much for me unless it's for a specific significant ride.

I guesstimated voltage sag and came up with less than 55% efficiency at peak power, which surprised me because I thought Colossus could handle a lot more current.

John in CR said:

The efficiency curve for that run from 0 up to 15.1hp out sounds interesting, but at a minimum I'd need efficiency at peak power out. Average efficiency doesn't do much for me unless it's for a specific significant ride.

I guesstimated voltage sag and came up with less than 55% efficiency at peak power, which surprised me because I thought Colossus could handle a lot more current.

Click to expand...

Colossus can handle more power I need to provide a controller that can accomplish this. The efficiency is real time not an average but because its a bit spikey I use a rough average.

If efficiency was 67% at peak power out of 15.1 hp with 295A from the battery, then voltage would have to sag to 57V. That doesn't sound right. You can talk about how much power Colussus can take, but if efficiency is in the low 50's at peak power, then you're about done, and you'd need to increase voltage to get much more power. That is unless there is something else wrong causing a hit to efficiency.

Face palm john this is total system and the sag was NOT that low remember this is losses in the controller the motor the brake drag the tire flex the wheel bearings etc.. I will come back to this.

Time for some new batteries if voltage was sagging from 84V all the way down mid to high 50's. With 20ah of the cheapie 20c hardpacks I was only getting voltage to sag from 84V down to 71V while pulling 425A.

John in CR said:

Time for some new batteries if voltage was sagging from 84V all the way down mid to high 50's. With 20ah of the cheapie 20c hardpacks I was only getting voltage to sag from 84V down to 71V while pulling 425A.

Click to expand...

JOHN WHERE THE HELL DID YOU THINK MY VOLTAGE WAS SAGIN TO 50'S??????????????

I WILL POST MORE TO EXPLAIN THIS SOON BUT SERIOUS ARE YOU DRUNK?

Ok John here is a screen shot this is showing the steady decline in battery voltage as rpm goes up and the wattage goes up as well. Remember with true phase current something you have not ever experienced the motor amps stay the same and the battery amps climb until you are about at the max hp. I will try to find more screen shots to help you understand.

EPIC face palm really you are not listening to me at all. BUT I will try to bare with you to explain it. 95% motor right... say just a guess 90% controller right... Say 90% bike this is the chain brakes and wheel bearing and tire flex losses its strapped down hard. Say 2% drag from the bearings in the dyno it self which my new program will hopefully work for the coast down run to add back those losses....
Say 5% in the wires and connectors. Lets see that's 5 + 10 + 10 + 2 +5 = 32% losses TOTAL system (68% efficient) this is not even talking about sag because my dyno measures the voltage and amperage going into the controller so sag is not even a factor! That 68% number was just a guess at the numbers of each part. Also this is with 3 packs in parallel on the bike at the moment Im running 5 in parallel.

NEVER DID I SAY my system efficiency was battery sag to 50v or some weird number you pulled out of thin air. Just because you ride around and your motor is not warm to the touch doesn't meen shit in the real world. When I run colossus at 350 phase amps with 16khz it never went above 40 deg RIGHT on the windings!

John in CR said:

If efficiency was 67% at peak power out of 15.1 hp with 295A from the battery, then voltage would have to sag to 57V. That doesn't sound right. You can talk about how much power Colussus can take, but if efficiency is in the low 50's at peak power, then you're about done, and you'd need to increase voltage to get much more power. That is unless there is something else wrong causing a hit to efficiency.

Click to expand...

Your math is all wrong dude.

Its 15.1 hp at the wheel....
With about 28.5 hp going into the system. The battery was only sagging to about 72v at this point BUT THE SAG IS NOT A MESUREMENT OF LOSS IN MY SYSTEM. I am measuring the voltage and amperage at the controller so the DYNO calculates power in VS power TO THE DYNO ROLLER. I can't make this any more clear.

You can facepalm and claim I'm wrong all you want, but my math was spot on since my guess of voltage sag was only 1V off. You gave us output power and current input, so all I needed was voltage to get power input in order to compute efficiency. I realize perfectly well that is total system efficiency, which includes some other losses. By your own numbers you tell us 53% efficiency at peak power, so my guesstimate was spot on. If your tire and chain friction and controller losses add up to 14%, which is what it would take to get to the 67% efficiency you claimed for the motor, then something seems horribly wrong.

I figured those other losses add up to only a few %, putting motor efficiency in the mid to upper 50's. Maybe the problem is the low pwm that you mentioned in the video as blame for extra motor heat, and a change in tuning will net higher efficiency at that power level. If not, then where is that extra 10% or so in losses that I'm not seeing?

John in CR said:

You can facepalm and claim I'm wrong all you want, but my math was spot on since my guess of voltage sag was only 1V off. You gave us output power and current input, so all I needed was voltage to get power input in order to compute efficiency. I realize perfectly well that is total system efficiency, which includes some other losses. By your own numbers you tell us 53% efficiency at peak power, so my guesstimate was spot on. If your tire and chain friction and controller losses add up to 14%, which is what it would take to get to the 67% efficiency you claimed for the motor, then something seems horribly wrong.

I figured those other losses add up to only a few %, putting motor efficiency in the mid to upper 50's. Maybe the problem is the low pwm that you mentioned in the video as blame for extra motor heat, and a change in tuning will net higher efficiency at that power level. If not, then where is that extra 10% or so in losses that I'm not seeing?

Click to expand...

NO JOHN YOU WERE OFF BY MORE THEN 10 VOLTS!

Like I said this is not part of the equation and I had some weak wires etc. The battery it self was not sagging as much. New pack stays in the 80s non the less the controller that I was talking about is/was very inefficient. The motor was running a lot more efficient and could have been even better if the controller could have been used at a higher pwm frequency.
John so I say it again this is total system efficiency normally bikes like zeros are in the 70s for TOTAL SYSTEM. I'm not far off. With a properly designed controller and the right current to colossus it will be there as well.

Ok John here is 3 more screen shots. IM sorry you can't understand the basics. Remember this is before the roller was re-knurled so I had to strap down very tight.

But this is enough on this thread about this because I'm trying to add an eddy brake and that's what I was trying to discuss here not controller efficiency vs other system efficiencies.
AGAIN this is with an old controller which had lots of flaws and I was still only down a few % from an oem!

I can't understand the basics...really? Methods tried that route once and it didn't fly very far. I'll just stay in the Christmas spirit and leave it at the fact that I was talking only about your 15.1hp out run. You gave current for a 20s3p pack at 295A, so I estimated voltage at 71V. You tell me it was 72V, so 71v is pretty effing close for a guesstimate. Current times voltage is power in, and power out divided by power in is overall efficiency AT PEAK POWER, which is all that interested me. That's where the 54% comes from, yet you said efficiency was 67%, but now you're posting screen shots of 10hp and 66% max efficiency. Did you notice the speed for peak power and for peak efficiency? Something is wrong there too.

If for your 15hp peak power run you want to blame a bad controller for the overall low efficiency in the mid to low 50's, then fine I'll wait. Let us know when you have good numbers to look at. It's been a long time coming and I'm interested in what Colossus really does. What you claim it will do doesn't cut it, not when you post overall efficiency results of 54% efficiency at only 295A input at 72V with 15.1hp peak hp out, and not when it only hits 66% peak efficiency during a 10hp peak power run.

When results don't stand up to simple overall tests of reasonableness then I'll question them every time. If you say it's the controller, that seems strange, but fine I'll accept that. I won't accept the stupid comments though, not when I'm not the one so tangled in the trees that the view of the forest is obscured.

John in CR said:

Time for some new batteries if voltage was sagging from 84V all the way down mid to high 50's. With 20ah of the cheapie 20c hardpacks I was only getting voltage to sag from 84V down to 71V while pulling 425A.

Click to expand...

Right here john you are claiming voltage sagging to mid fifties....

John just because the voltage sagged to xx doesn't mean you add it to the system efficiency. The voltage rebounded to almost 84 meaning the energy was still in the battery. If I run this off a power supply then it would be not part of the equation when you buy a motor they don't estimate the battery sag for what your motor can do. You sir are the worst person for seat of your pants tuning and estimating keep running your junk I don't care.

John in CR said:

I guesstimate. Current times voltage is power in, and power out divided by power in is overall efficiency AT PEAK POWER, which is all that interested me. That's where the 54% comes from, yet you said efficiency was 67%, but now you're posting screen shots of 10hp and 66% max efficiency. Did you notice the speed for peak power and for peak efficiency? Something is wrong there too.

Click to expand...

NOPE its fine this Is how TRUE TORQUE THROTLE WORKS! In the motor the amps stay the same but as rpm goes up the battery amps increase.

john said:

If for your 15hp peak power run you want to blame a bad controller for the overall low efficiency in the mid to low 50's, then fine I'll wait. Let us know when you have good numbers to look at. It's been a long time coming and I'm interested in what Colossus really does. What you claim it will do doesn't cut it, not when you post overall efficiency results of 54% efficiency at only 295A input at 72V with 15.1hp peak hp out, and not when it only hits 66% peak efficiency during a 10hp peak power run.

When results don't stand up to simple overall tests of reasonableness then I'll question them every time. If you say it's the controller, that seems strange, but fine I'll accept that. I won't accept the stupid comments though, not when I'm not the one so tangled in the trees that the view of the forest is obscured.

Click to expand...

No the efficiency is not going that low its in the high 60s as seen in these 2 screen shots.
Sorry I had to pull up what I can for screen shots I have about 10 versions of the dyno software as I work though it with Damon to get the new one working the old files wont always load. But here is 2 shots of the 15.2 hp run and yes as speed increases so does HP but torque stays the same until about 80-90% of the max speed.