Bit Char-g DYNO stage 1 complete

[micro_Amps]

Here’s a sneak peak at my current project.
Its a micro car dyno.
At this stage it is speed measuring only, but that was the objective for stage 1.
Next stage is to put an electric load onto the car running the dyno and measure the power produced, but that comes later.
Even tho it is a speedo only at this stage there are some interesting results showing up between the different cars and motors.
This pic shows one of my twin cell bits doing 15Km/h but since this was taken I have rescaled the computer to show 10x the speed, so it now will show for example 157Km/h meaning 15.7Km/h. The computer in this setup will show up to 30.0 Km/h which is perfect for BCG use. The extra decimal place is important just to be more accurate and see minor changes in speed.

If any of you can contribute more ideas on the mechanics of a micro dyno, I’d be very interested to know. I have a few ideas but the more the merrier.
:)uA

Edited by – micro_Amps on 24 April 2003 17:07:12

[Admin]

Very nice, truely impressive!

Help me Obi Wan Kenobi, you’re my only hope!

[ph2t]

I’d like to see some pics of its guts!!!

cool!

ph2t.

[micro_Amps]

Yeh, of course YOU would !! :smiley2:
That will come in time ph2t. I’ll leave those until it is a fully working dyno.
For now, this is all you get. :D:evil:
:)uA

Edited by – micro_Amps on 24 April 2003 17:37:21

[Efarel]

Hi,
is that a bicycle type computer ?
How much for it in your country ?
You have cabled the reed switch to the rotary axis, don’t you ?

Can you post an “under the hood” picture please ?

Ciao
Efarel

[barto_85]

that is very cool and clever. nice job micro_amps

[micro_Amps]

Yes Efarel, you are very close.
It is a cycle computer, it runs through a reduction gearbox to the senser. Thats really all it is at this stage.
The computer can show speed, distance, elapsed time, total distance, and maximum speed. All the usual things.
Did you know these little cars can run for over a kilometer in a straight line before they go flat !!
All will be revealed “under the hood” as the project is nearer completion.

For your info Efarel, a cycle computer like this sells for about AU$35 (thats about US$21).
:)uA

Edited by – micro_Amps on 24 April 2003 20:03:51

[leonli17]

I just can’t wait until u uncover what’s in this amazing machine.

And Nice work micro Amps.

Let’s do 1/4 Mile under 8 Seconds!!!

[Efarel]

Hi micro_Amps,

greetings from Italy.

Good job indeed, I was thinking to adapt a slotcar type dyno but your idea is a great new way to solve this problem. Thank you !
Ciao
Efarel

[spanky]

well, how do you accomidate for the size of the wheel that is being spun by the tires.. bike computers rely usually on the hub of the bike, through a contact placed on the hub. i have also seen ones that place the contact on the wheel its self, and others that attach to the spokes… either way. many computers are designed for certain size wheels or can accomidate a couple different size wheels. some are universal… i guess it just depends on the computer.

if you place larger tires on your car than the stock tires your speedometer will be off. and the faster you go the greater it will be off.. your 15Km/h just seems kinda high for a dual cell.. (thats roughly 9Mph) many people have been doing speed tests with tread mills.. set the tread mill to 2mph and slowly accelerate it till the bit stays in one place. i have yet to hear of a dual cell hitting more than 7mph. (i believe thats the scale speed for breaking the sound barrier) what kinda motor are you using?

I think your idea and setup are AWESOME. but the calculations seem a bit off.

but i guess all of this depends on the type of computer this is..

Rock on Dude! have you thought of doing up a comparasion chart for different motors and battery configurations, and gear setups?

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
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[ph2t]

In my discussions with Micro, Spanky I believe he used his treadmill to calibrate the results.

ph2t.

[Shypo]

lmao thats damn cool…

—-
Go Fast, Be Free with Low CC

Undisputed Post Pimp

[micro_Amps]

I can assure you it is accurate, I have the equipment to be able to calibrate this kind of thing. Its what I do for my work.

The cars speed is correct, it has been faster in the past but is running a different motor now. It has a 3.8, 8.25 gears and 2.4v Nimh cells and goes like a rocket

I will be doing some comparison tests with different motors and batteries etc, but not for a while. I will be putting my spare time into developing the power measuring part of the dyno.
Stage 2 is to build and install a variable electric load that will load the rear wheels of the bits from zero load to lock up. Zero load is actually the hard part!
Stage 3 is to measure the output of the load in stage 2 driven by the rear wheels, probably in micro watts, only then will it be a true bit dyno.
Stage 4 is to work out the torque. I have ideas for all stages except this stage, maybe I will seek help from all of you when I get there.
But there is still a long way to go.

Spanky thanks for your comments, I appreciate healthy criticism, and also the good words of ther people too.

As I develop this further, I will post the results.

:)micro_Amps

Edited by – micro_Amps on 25 April 2003 16:00:06

[spanky]

I BOW TO YOUR GENIUS!!!:shock:

im not worthy…. im not worthy….

all i can think about for zero load would be to incorporate some ball bearings or someting…, but then the weight of the car its self would produce some load… unless that counts for zero load…

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
email: custombitbodys@attbi.com
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[ph2t]

An idea that comes to mind is to have part of the cylinder that rotates being metal. Sorrunding a portion of this (on the stator) would be a coil that would attract the metal part of the cylinder when current was applied to it. More current, greater resistance/load. Unfortunately the load would not be even since it only occurs on a fragment of the total cylinder………

ph2t.

[micro_Amps]

I am planning to have a modified DC motor, running as a generator, driven by the bit runnng on the dyno. The strength of the bit motor will determine the output of the generator, which will be measured (voltage and current).
Just ideas ticking over…..
:)uA

[jord001]

Incredible work micro but you need some sort of stop for the bit. Saves you holding it. Do the different tyre compounds make a difference??? 1 big question, how did you embedd that picture into your post. I would love to know how. I have a couple of albums at webshots and i know how to put the url in for it, but i can’t put a picture in a thread and you can. HOW?

jord :approve:

Mini Cooper B3.0 Anyone else got one?
R34 skyline booster
R32 skyline standard
Yellow Supra B2.2
others B2.2’s but standard.

My Pics @ http://community.webshots.com/user/jord01

[Efarel]

Hi Ph2t,

has the computer you used something to set the bike’s wheel diameter or is it a simpler computer ?
I just found a computer bike here for 9 usd but it has not the adjustable wheel diameter. Is it usable for your dynotype project ?

Greetings
Efarel

[spanky]

Quote:

how did you embedd that picture into your post. I would love to know how. HOW?
jord :approve:

hey, imbeding a pic is pretty easy. you first have to have your images hosted somewhere on the internet. unfortnately not all online pic hosting services will allow you to link directly to a pic. if you have your pics online, all you have to do is click on the “insert image” button on the top of the reply screen. or you can type it in by hand.

if you hand code your image link in like that it should also work.

if you want i can host pics for you and you can put your albums up on my site. i will be completely remodeling my site in a couple more days. so things will be a lot more 56k friendly….

email me if you would like me to host some pics for you.

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
email: custombitbodys@attbi.com
website: http://custombitbodys.home.attbi.com

Edited by – spanky on 28 April 2003 08:04:16

[ph2t]

Quote:

Hi Ph2t,

has the computer you used something to set the bike’s wheel diameter or is it a simpler computer ?
I just found a computer bike here for 9 usd but it has not the adjustable wheel diameter. Is it usable for your dynotype project ?

Greetings
Efarel

Mate, I think you should be asking micro, not me…..:smiley2:

[jamiekulhanek]

Micro_Amps, ive been thinking about a dyno for quite a while now. My original idea was to have a bit motor connected to a mA meter (say 200mA). Then have the motor connected to a set of bcg gears, which is connected to a roller. The gears should be reversed, i.e. geared up. The the car is placed on the rollers….etc….etc…

This would put a load on the car, and can give you an idea of the power output.

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[jamiekulhanek]

Ok micro amps i read your idea which is prettymuch the same as mine.

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[jamiekulhanek]

Sorry for the multiple posting, but i think this has just opened the door to the possibilities of dyno competitions for bits 😯 I could imagine different classes of bits etc.

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[Cranga]

Brilliant Micro!

This proves we have some smart aussies out there!
somewhere!:dead:

Its nice to be important,

But more important to be nice.:approve:

[Efarel]

[/quote]

Mate, I think you should be asking micro, not me…..:smiley2:
[/quote]

Yes, for sure !
A little freudian mistake !

Sorry Ph2t and sorry micro !

but the question is the same, do I need a bike computer with variable wheel radius setting or can I use a simpler (and cheaper) unit ?

Ciao
Efarel

[PandaBear]

Quote:

but the question is the same, do I need a bike computer with variable wheel radius setting or can I use a simpler (and cheaper) unit ?

Just butting in here, but I did once used to ride a pushbike too…:)

You’ll find that *all* bike computers have “variable” wheel size settings, as all bikes have different wheel sizes (24″, 26″ etc etc). You define it in the initial setup.

The simpler/cheaper units probably just have less functions, maybe no clock etc. Or the box might supply 2 sets of sensors and mounts so you can install it on 2 bikes.

[micro_Amps]

Quote:

but the question is the same, do I need a bike computer with variable wheel radius setting or can I use a simpler (and cheaper) unit ?

Efarel, the cycle computer I used, it is able to be set to ANY wheel circumference from 5mm to 4000mm. It is very versatile.
That makes it usable for just about any speed measuring project so long as you know the circumference of the wheel being measured.

Jamie, we are thinking along the same lines, but I have no accurate idea what kind of power these cars will put out. Depends on the output voltage too, not just the current.
Keep one thing in mind tho, you need to start readings with ZERO load, if you are using constantly meshed gears with a permag motor you will never be able to remove the load.
The motor being used as a generator will probably be a ‘wound field’ motor specifically for this application.
I’m still working on it……

And yes I am also thinking of dyno comps, distance comps etc, etc
It may open up a new dimension for these little cars.

:)uA

[spanky]

hey panda, the reason that i mentioned the wheel size earlier is that i looked at several bike computers that would fit only 2 different tire sizes. so not all bike computers are variable tire size.:sad:

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
email: custombitbodys@attbi.com
website: http://custombitbodys.home.attbi.com

[PandaBear]

Quote:

hey panda, the reason that i mentioned the wheel size earlier is that i looked at several bike computers that would fit only 2 different tire sizes. so not all bike computers are variable tire size.:sad:

Wierd!! They must have cut costs even further now… blackeye:
Last one I looked at was a Cateye or something like that.
Quite a flashy one but it was just A$45 or so.

Yeah, guess you gotta check what is the possible settings on the machine you do buy. But I swear you’ll be getting wierd looks when you ask for something that does 10mm wheels… :smiley2:

[PandaBear]

Quote:

Efarel, the cycle computer I used, it is able to be set to ANY wheel circumference from 5mm to 4000mm. It is very versatile.
That makes it usable for just about any speed measuring project so long as you know the circumference of the wheel being measured.

I might have to go buy meself one of those things real soon too… was thinking of taping a magnet to the tailshaft and using that to check the roadspeed. Might be a tad more accurate than a 50yo moving-magnet-in-a-steel-cage speedo (you both know what for :smiley2:).

Either that or am real tempted to buy meself a K-band doppler radar gun… I’d just point it at a stationary passing tree, eh? But these are still a little outside the justifiable pricerange. :blush:

[Namuna]

Micro, great work!

Spanky brought up a good point, which now makes me believe I need to look at my resutlts (I did Power/RPM tests at: http://tinyrc.com/forums/showthread.php?s=&threadid=10662).

The encoder wheel used to test the RPMs (in my tests) is CONSIDERABLY larger than the standard wheel diameter.

Does anyone know what the calculations are to compensate for such things?

Thanks.

[spanky]

Namuna i think your results are right on.. just look at your rpm results. they are pretty much right on par with what they should be for the respective motors..

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
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[Namuna]

While the lower RPM motors seem pretty right on, i’m worried that whatever calculation I’m not accounting for (while no noticable factor at lower RPMs) is showing itself at the higher RPMs…Explaining why I got readings 2,000RPMs lower than rated on the 3.8 motors.

[spanky]

you could be correct.. simmilar error is apparent when you put different size tires on your car. at low speeds the speedo reads correct or fairly close, but the faster you go the further off it is.. i think that would be called an exponential curve..

either way here are some formulas that they use to compute error with different tire sizes.. i think this might help figrue out if or how much error there is.

Ford Motorsports Also Uses This Formula:

(Driven Gear Teeth = Drive Gear Teeth x Axle Ratio x Tire Rev. Per Mile)/1000

FourWheeler Magazine uses:

(Old Tire Diameter x Indicated MPH = Actual MPH)/New Tire Diameter

im sure there are other formulas to do the same thing out there. hope this helps..

i found these formulas by doing a search for Speedometer correction.
http://www.therangerstation.com/Speedogear.html

:clown:

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
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website: http://custombitbodys.home.attbi.com

[jamiekulhanek]

Micro_Amps, I presume you need the voltage and current readings so you can calculate wattage?? I dont really think that it is accurate enough. My idea is just to have a generator across a current meter, to measure current under a slight load that increases as rpm increases. This will be good for comparisons and dyno comps etc.

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[micro_Amps]

Quote:

but you need some sort of stop for the bit. Saves you holding it. Do the different tyre compounds make a difference???

Jord, there will be a stop to hold the bit in place….I am imagining a 3 sided sponge foam lined arrangement to keep the bit from moving.
I had only just finished stage 1 of this project when I took the photo, so it was not made yet.
Yes tyres do make a difference to the speed. The softer stickier (pink or purple) tyres form the BCG coloured tyres set grip the best and give the best results. With other tyres you need to push down just a little to get good traction.

Quote:

Spanky brought up a good point, which now makes me believe I need to look at my resutlts (I did Power/RPM tests at: http://tinyrc.com/forums/showthread.php?s=&threadid=10662).

Namuna, your work is accurate. The diameter of the wheel being measured does not effect the amount of pulses being produced, the rpm does. It will still measure one pulse per revolution regardless of the diameter of the wheel. A 5mm wheel spinning at 20,000 rpm is spinning at the same rate as a 20mm wheel spinning at 20,000 rpm. The surface speed at the outside edge may be faster but thats not what you were measuring, it was the rpm, and your method is accurate, well done.
When car manufacturers quote various formulas for correcting measured speed with different tyre sizes, they are measuring the speed thru the driven wheel being measured, whos diameter will change with every different tyre. A dyno is different.
A dyno (as in this situation) measures the speed ‘of the road’ instead. I know it sounds silly, but the dyno measures the speed at the outside edge of the tyre, the road surface. On a dyno, changing the tyre diameter WILL change the speed measured, but wont change the accuracy of the dyno measurement. Its kinda confusing, but dont compare it to a speedo in a car, its not the same.

The discrepencies in rpm at the higher speed motors is to be expected. You will probably find an error tolerence in production. They are not a highly precise motor. Perhaps if you lube the shaft ends with a little silicon or teflon oil, you may find the revs come up a little. I have found this is the case on the dyno/speedo.

Quote:

I presume you need the voltage and current readings so you can calculate wattage?? I dont really think that it is accurate enough.

Jamie, yes you are correct, I will be using wattage as the measure of the power output of the BCG motors. It is actually more acurate that way because……
A high revving motor producing a high voltage will probably produce a low current and therefore a medium wattage output,
A lower revving motor will produce a lower voltage but may be able to produce a higher current output, thus a higher wattage output, therefore it is the STRONGER motor of the two. This is primarily what I want to prove amonst all the different (OEM) motors.
There are 3 things to be considered
#1 is speed (rpms)
#2 is output power produced
#3 is output torque produced.
All of these things are different, they are related but they are different. It is easy to cross over between them when talking about motor power and speed and stuff like that.
I still have a long way to go before perfecting the power output part of this dyno but I am getting there.

Im going to stop rambling now.

:)uA

Edited by – micro_Amps on 30 April 2003 20:22:23

[Namuna]

uA…

Thanks for laying my concerns to rest, now I don’t have to worry about it.

Something to keep in mind…The BCG PCBs have mA limitations. Initially I tested this by using my Multimeter, in a closed circuit with no load I got a reading of less ~275mA (A 350Z booster PCB read ~320mA, boosted).

[spanky]

if namuna did the rpm tests on the setup shown on the first page the rpm readings would be off. RPM’s are usually not measured by the wheels. if two different size wheels(tire on car and spindle) are used you get the same effect that you would as with the gearing on your bcg. where as a larger wheel will spin a smaller diameter wheel faster. and vise versa. yes MPH would not be effected, provided you have the correct equipment. but rpm’s can really only be measured by sticking the motor on the spindle which is read by the bike computer.

i guess what im saying is if you have your 5mm bit wheel spinning at 20,000 rpm, which is spinning a 10mm wheel. the 10mm wheel will not be doing 20,000 rpm. the exact rpm of the 10mm wheel would be…. (circumference of 5mm wheel is roughly 15.7mm, and of a 10mm wheel is roughly 31.4) so for every 2 rpm of the 5mm wheel you will get 1 rpm on the 10mm spindle.

Circumference = 2*pie*radius

This was what i was worried about with the error. i thought that you did it correctly. However even the smallest amt of error, can grow to a large error given the size of the test field. (rpm’s)

anyway

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
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[Namuna]

Well, so much for concerns being rested.

When I get home tonight I’ll get another encoder wheel setup, with as close a diameter setup to the stock BCG wheels as possible.

I should’ve done that in the first place anyway, even with any errors, this will give as close to ‘real world’ results as possible.

[spanky]

well if you know the ratios then you dont need to change the sizes.. just figure out the circumferences and use the formulas..

i dont have a ruler with me but im assuming a bit wheel is about 5mm diameter. so that would be roughly a 15.7mm circum. if its like stated above. that would be a 2:1 gearing ratio.. so what ever your computer is reading is exactly one half of the auctual output. the ratio comes from the 31.4mm/15.7mm, or 2:1.

so you can stay with your same setup. just figure out what the circumference of the wheel your comp is running from.

Hey Micro. i think you might be a bit better with this than me. but am i thinking in the correct direction. or am i just babbeling?

I have also heard that RCmod is getting some new motors in sometime in the next few days. hopefully its that monster that weve all been wating for.. (i want a 60,000 rpm motor that kicks booty with one cell)

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
email: custombitbodys@attbi.com
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[jamiekulhanek]

MIcro_Amps, consider many different interchangeable rollers to change the gearing bit by bit, that will help you get the max performance for a motor. (Im guessing you probably already know that)

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[PandaBear]

The roller has a geared reduction unit underneath it, Jamie… :smiley16:

[ph2t]

Hehe, Panda and I have seen the guts of this thing in real life. Maybe more Melbournians would be coming to the next meet knowing such goodies are available to check out!
😀
ph2t.

[micro_Amps]

Quote:

guess what im saying is if you have your 5mm bit wheel spinning at 20,000 rpm, which is spinning a 10mm wheel. the 10mm wheel will not be doing 20,000 rpm. the exact rpm of the 10mm wheel would be…. (circumference of 5mm wheel is roughly 15.7mm, and of a 10mm wheel is roughly 31.4) so for every 2 rpm of the 5mm wheel you will get 1 rpm on the 10mm spindle.

Spanky you are spot on here. But if you have a cycle computer calibrated to read the SPEED (not rpm) of the 10mm spindle, you would still be accurate in your speed measurement of the 10mm spindle which is the same as the road speed.

This is getting a little confusing, it is difficult to talk of rpm, speed, (and power and torque) and not overlap lines of thought.
I appologise if I am unable to convey things with more clarity, I wish I could. I wish I could SHOW you exactly what I mean. I think part of the problem we have here is that delayed, written explanations dont have the ‘to and fro’ of real conversations.
I know we are both on the same track spanky, just a little unclear. We could go on for ages on this kind of thing, and I wont…..
But,
Let me try once more on Namunas rpm readings……
The readings are correct, I assure you. So long as the frequency (Hz) found at the rear wheel disc is multiplied by the gearing ratio on the bit then the readings are accurate.
Forget about the “speed”, we are talking rpms only here, and rpms is independant of speed. Speed is a relative term, rpm is not.
The size of the wheel with the slot in it is irrelevent. The slot will still come around once per revolution regardless of the size of the wheel. This frequency x the gearing ratio = motor rpm. Simple!!
Namuna you are correct, I bet my left one on it. If you do the readings with a different size slotted wheel, you will get the same results from the same motors.
Now I suppose I have made that as clear as mud.

Quote:

consider many different interchangeable rollers to change the gearing bit by bit

Jamie, I am way ahead of you on this one mate. I hope to be able to vary the load from zero (high speed) to standstill (or very low speed). That should accomodate all bits, single, duals, triples, and frankensteins. As ph2t has already mentioned, there is a reduction gearbox under there that will handle any speed.

Quote:

have also heard that RCmod is getting some new motors in sometime in the next few days.

Spanky if you hear they have them, can you email or PM me, I would love to get my hands on some of those.

:)uA

[spanky]

im not talking about speed at all. If you use the dyno as shown in the pic on the front of this post and dont account for the size of the spindle that the tire is spinnning on your readings will be off for RPM’s.

Yea, you basically just restated what i said.. I never said that MPH was an issue. however to get correct RPM readings you have to know the ratio from the rear wheel to the spindle. if you dont do this calculation are you assuming that the spindle is the same as the rear wheel of the car. This does matter!

either way, once you find out the correct RPM’s you can calculate the exact mph for the car. by using the circumference.. in fact through calculation you can find out the max speed under no load. taking namunas results and doing the math with the specific gearing ratios that you use in the car… for example a 12:1 ratio would suggest that for every 12 revolutions of the motor the wheel will make 1 rev. from there you know the wheel rpm.. with the wheel rpm and wheel circumference you can find distance traveled per min. and your mph…

We are basically both talking about different ways of measuring rpm.. Namuna was using the slot in the wheel. where as your machine can also measure RPM if you do the calculations. in fact you should create a spreadsheet on your computer so you just enter in the speed, and the gear ratio.. and through formulas it spits out rpm…

cool thing is. namuna can figure out what the rpm and speed are for no load.(other than the wheel) your setup can find speed and rpm with the load of the car…

Custom bodys: Ferari 250 GTO, 69 doge charger, Micro Cooper, Beemer 320i Turbo, Baha Beatle, New Beatle Rsi Porche 911
email: custombitbodys@attbi.com
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[micro_Amps]

Yep, Spanky you are dead right.
I wasnt assuming the spindle was the same size as the rear wheel. Actually the cycle computer is calibrated to the spindle not the BCG wheel size. So that anything causing the spindle to spin will have its speed measured by the computer.
You obviously have a good grasp of all this and I appreciate your feedback.

I will be doing a spreadsheet of running speeds but I will wait until I have perfected the power measuring mechanics.
I have achieved some promising results so far but lots of work still needed
:)uA

[Efarel]

Hi,
a maybe stupid question…

I connected a voltmeter to a rear end chassis with motor, rear axle and wheels (no battery no radio equipment, wired directly to the motor).

If I put a BCG on the rear axle and press forward I’ll read some millivolts on the voltmeter.
What am I measuring in this way ?
Can I take this numbers as a performance indicator of that bcg or that motor ?

Ciao
Efarel

[micro_Amps]

Not a stupid question at all. 🙂
Efarel, you have the basis of a very crude dyno there my friend. As you cause the wheels to spin, power is generated in the freespinning motor, which is now running as a generator, and your multimeter is showing you this.
The faster your powered bits can make the motor spin, the more power will be produced.
Unfortunately using this method will only show more power for a faster motor, it doesnt show a high power output for a slower ‘stronger’ motor.

If you keep your multimeter on the same motor and change the motor that is doing the driving you should see differences between the driving motors. This is a difference between the speeds of these motors and to a lesser extent differences between the power of those motors too.
Well spotted Efarel, you have indeed found a way to determine output strength of bit motors.

I am using a similar theory to determine the power produced from a BCG motor, but it is using a wound field DC generator. This will show the wattage (in milliWatts most likely) produced from the BCG motor driving the dyno.

Some good news, tonight I have been able to get the first decent power readings from the dyno.
I still have a way to go but it looks promising.
From here it is a matter of fine tuning, putting it all together and testing it further. Hopefully I can do this over the weekend.
It is getting closer.

🙂 uA

[jamiekulhanek]

Remember, a electric motor has linear torque vs rpm curve. Unlike the logarithymic curve of a piston engine. So if the motor is revving harder, its putting out more power than before.

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[PandaBear]

Quote:

So if the motor is revving harder, its putting out more power than before.

A free-revving electric motor shouldn’t be “making” any
power at all (apart from, and ignoring, Friction).

Its only when you put a load on it that the ‘power’ is generated.

[micro_Amps]

Yes Jamie, the torque /rev graph should be linear, but it diminishes at higher revs

therefore it is inverse to a combustion engine

generally DC motors have higher torque at low revs, dropping off (linearly) as the rpm rises.

All that DC motor theory has finally came in usefull for something.

The Dyno is progressing,
I am getting output results for different motors, I would just like to get a higher output to play with. I am in the process of hand winding a mini DC generator to get a higher result, but progress on that is slow, it should work tho.
I’ll keep you posted.

:)uA

[jamiekulhanek]

Sounds pretty cool. Ya should sell kits 🙂

If life is a waste of time, and time is a waste of life, then let’s get wasted and have the time of our lives!!

[ph2t]

So what’s the story morning glory?

[micro_Amps]

Dyno IS progressing but slowly. I have been able to get some output power production, but it is a little on the small side.
I have some other ideas which I will try soon, it will probably mean redesigning the whole thing but that is ok, I just have to put more time into it to finish it.
I hope to have some time off work soon, fingers crossed I will be able to finish it, and get some decent results.
Then I can start the spreadsheet of results.

:)uA

[GT-ahh]

If someone could design an interface so you can connect it to your PC. hack the bike computer and get the pulse singal or however it works and run it into a serial port. You could use this data to generate bhp graphs and the like on your comp. now that would be an effort. maybe using a mouse roller as the input would be an alternate idea.

[spanky]

well im sure there are already some bike computers that link to your pc. i have a HRM that links to the pc. so i couldnt imagine why they wouldnt make a bike comp that does the same. basically you do your workout.. or in this case. your dyno run. and the comp stores it all.. then you link up with your pc and dl it all.. the software that comes with it should be able to do allyour graphing that you need…

only catch is cost.. it could cost 100+ for a bike comp that will link to pc…

[micro_Amps]

Interesting idea tho. Might have to look into that one. Any ideas which cycle computers link to PC ??
:)uA

[spanky]

yes i have found one that will even give power output as an option…

go to http://www.polarusa.com

http://www.polarusa.com/Products/Consumer/S720.asp
http://www.polarusa.com/Products/Consumer/S150.asp

look at the S720i. that one has everything.. but at a 320.99 price…. thats kidna steep. the S150 also does speed and distance and is only i think 150. but im sure you can find these cheaper at retail stores.

i own a S410, which is designed for runners. the uplink can be a pain in the but if you dont have the infared option. but it works pretty good. i am very happy with the uploads and the info i get from this thing…

[micro_Amps]

Thanks Spanky, I own a S410 as well, used to do alot of triathlon stuff.
I’m not sure that the ‘power usage’ they refer to would be useful to us. I think it is determined by rider weight and pedal cadence. But there is always the option of investigating and modifying.
Pricey tho.
:)uA

[spanky]

i just got a bicycle computer that allows me to enter in the circumference of the wheel. im not sure if they are all like this… but this would allow for the most precise calculations. by knowing the circumference of the wheel that has the magnet, and also figuring the circumference of the bit wheel.. you can calculate the auctual speed/rpm.

my bike computer

my bike computer…

[betty.k]

so, time to revive this sucker!
first, i wanna know how to custom make a sensor arrangement, i’m thinking maybe a magnet on a wheel with a steering coil wired to the contacts, am i on the right track?
next i wanna know how to calculate the geardown ratio and what sort of gears to use. let’s say the roller on my dyno has a circumference of 10cm. and i then set the wheel curcumference on the speedo to 100cm. am i correct in assuming a 10:1 reduction wil be the correct choice?
and what if i find a reduction gear i want to use, let’s say it’s 8.7:1. given that i know the curcumference of the roller, 10 cm, how do i calculate the figure to punch into the speedo:question::8ball:

Edited by – betty.k on 20 April 2004 04:02:54

[leonli17]

uA, if u can somehow open up the DYNO box again and take a photo of the inside, It’ll be great.

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