TeamGoodWrench

The longer pair goes to your power supply. the shorter pair powers the motor being tested.

There is actually 2 windows versions of the Facts machine software.
The other Windows version is the production version.
I think that's even more inacurate than Facts II. It only purpose is to produce a label for the motor. It's test cycle is settable between 3, 5, and 7 seconds. It also has a setting to adjust the test voltage between 5 and 7 volts. But the dyno has to be modified to use it.
And it ALLWAYS ALLWAYS shows higher numbers for a motor.

Teamgoodwrench,

Let us know how you did with your first dyno-run!
Good luck.


Best regards,
Pizza

Last night I was trying to figure out just how much this flaw I see with the Fantom could effect the way I would typicaly tune a motor. At this point I'm inclined to think that it would not have much effect on the way I tune a stock motor.

Based on my current thinking, the flaw is most significant when you are attempting to compare two motors with drasticly differnt Torque and/or RPM curves. Such as when trying to compare a P2K to a Revenge of the Monster motor. The effects of this flaw are directly related to the slope of the acceleration curve... the steeper the curve the bigger handicap placed on the motor. In my experiance a steeply sloped acceleration curve pretty much directly assoicated with higher peak torque(initial torque on these motors).

I don't have the data for my Ex-Spec motor, but I beleive a motor like this is likely to be handicaped a great deal by this flaw. Because it has a very steep slope, due to it's high torque and low RPM. I really woulld like to view the data of my test of the Ex-Spec and one of my Paradox motors, I think it would tell me alot.

So... my advice right now for Fantom users would be to be carefull when comparing motors with drasticly diffent Torque/RPM curves... My best guess is that when compareing two of todays's stock motors, such as the P2K to a Revenge of the Monster motor, the P2K is likely to be handicaped by 1 or possibly 2% at peak power. I can't say for sure and I really don't know much about how much the flaw will effect power at other points...

Your best bet would be to only compare simmilar model motors to one another...

I do beleive that changing the timming of a motor will also cause this flaw to have greater effect then anythiing like spring tension... I'm not sure how differnt brush compounds would effect the slope of the accleration curve. I just don't have much experiance with the effects of differnt brush compounds as it relates to torque and RPM.

Oh... actualy the thing to watch out for is when you are attempting to compare two motors with drasticly differnt spin up time... this flaw seems directly related to spin up time since spin up time is directly related to accleration and/or torque... the shorter the spin up, the more negitive effect... The longer the spin up, the less likely the flaw will effect the data... this is in very general terms because the slope of the acceleration curve can change at differnt points in the dyno run depending on motors being tested.

If you should ever play with timmed brushes, this would also likely have cause this flaw to rear it's ugly head... Changing the width of the brush contact surface will also likely awaken this flaw to one degree or another. Also as with all dyno testing, if the brushes are not fully broken in, your results could be really strange and unpredictable, this is mostly due to the fact that the actual contact area of the brush and comm will not be consistant untill after full break in.

Snuffy,

I'm currious about this other version of the software... From what I can see, one of the effects of this flaw is to cause lower overall output power on all motors I've looked at. It just simply effects high torque motors to a greater degree.

If the output power numbers are higher on this other version of software, it's possible that they may have corrected the problem... but then the higher numbers you speak of could be due to something entirely differnt.

Yep -- Once I looked at it for a minute I figured it out.

Thanks !

Dynomohum-I took a look at your Fantom Data graph. Seems like a dramatic difference between your calculations and the Fantoms. I had a couple of questions. Did you calculate your Power and Efficiency numbers based on the spin up times? What numbers did you use for the Rotational Inertia of the flywheel and for the armature.

Another wrinkle in comparing different brands of dynos is that the Robitronic Dyno uses an armature inertia (the default 4.20)that is an average for mod motors. If you run stock motors on it, it will tend to read a little high. If you want more accurate stock motor data use 3.12 for the armature inertia (moment of inertia). (The value for a stock motor with proper units and powers of ten is 3.12 x 10^-6 kg-m^2 This is calculated for a stock arm which weighs about 47 grams and has a 2.304 cm diameter)

Yes there is a dramtic change in output power when you calculate things the way I think they should be done. However if you look at it in realtive terms, the error is fairly small (about 1% near as I can tell). Realtive to best case senero to worst case, and adjust for the new power differances. At least this is true for all 18 of the motors in Snuffy's Fantom II data. I always felt Fantom's power and effciency numbers seemed really low, my calculations bring them up closer to what I would expect... My power and efficnecy expectations are based on my experiance with both the TurboDyno and the Robtroinc dyno.

For the moment of Intertia I reverse engineered Fantoms Torque figures. I question the figure I came up with, not in it's accuracy based on Fantom's data... but I question if it shouldn't be a little higher. I beleive this based on power and efficency numbers that the TurboDyno gives for 5 volt tests. Even my new re-calculated power numbers are lower then the TurboDyno typicaly gives. This is a very minor issue however... as long as your looking at the data realative to other corrected data.

.0432 is what I came up with for the moment of intertia for the Aluminium flywheel Snuffy was using for his dyno runs.

I vaguely remember someone once saying that no two fantom flywheels are exactly alike... I don't know if that is really true or not, but it certianly would effect the true moment of intertia for any given Fantom dyno.

I'm using Fantoms figures for RPM and time interval, as given from the Facts II 'time based motor data'. I think torque should be calculated using delta RPM that uses 'present_RPM - previous_RPM', rather then 'next_RPM - present_RPM' like Fantom seems to be doing. Past, present, and next reffering to time intervals that are associated with the data as given by the Fantom...

Fantom also apprears to be useing present RPM rather then 'average RPM from previous to present' to calculate Power, using their apparently flawed torque figures. This issue of average vs. present RPM seems to have little or no effect on the output power numbers when viewed in realitive terms. I use Average RPM for my calculations. I based this on info leared from the following web site.

http://www.land-and-sea.com/dynamometer/kart-dynamometer-article.htm


It's good to see John come and particapate in this discussion... I welcome any and all reviews of my findings... Especialy from someone like John who has shown himself to be very objective and skillfull in anything I've ever seen him evaluate...


Oh... I did get Mike Golden to modify his DynoViewer to allow the option of calculating Fantom data my way... :) I think Mike would be comfortable in making this public... if so I will make it available soon.

Near as I can tell, the moment of intertia figures used does little more then cause ALL the power figures to go up or down in a uniform fashion. This also seems to be true for the armature's moment of intertia, although it's value plays an even smaller role... most likey because it is so much smaller.

So... if you change these values it might effect the peak power, but it also effect power at 10, 15, 20, or whatever. So in realtive terms it doesn't seem to matter much what you use.

I'm not trying to compare dyno numbers one for one... I don't think that can be done. There are just too many variables involved, such as test voltage... I do beleive that the Fantom should give nubmers that are a little closer to those that other dynos give. I bleive that test voltage seen at the motors is the single biggest factor in making it impossible to compare dyno number one for one on any electric motor dyno I've seen. The Robitronic varys it's voltage based on load and user settings... The Fantom uses constant voltage and it doesn't change with load... This causes torque, spinup, RPM, effciency all to be so much differnt then the Robitronic dyno that I don't think you could ever compare the two one for one.

(The same basic problem comes into play with the TurboDyno, but since it's not a flywheel dyno there's even more variables...)

The following web page attempts to show and explain the differances I see when comparing my calulations to Fantom's calculations... The graph is all the way at the end of the page...

http://www.wiltse.net/facts_iii.htm

There is a link to that page from my other page that addresses the oddity when I tested my Ex-Spec motor and a Paradox and attempted to compare them both useing a Fantom dyno... that page is located here...

http://www.wiltse.net/facts.htm

Guys;

I am truly greatful for all of this discussion on Dyno's. This has allowed me to make the informed decision of purchasing a Robitronics Dyno. I feel based on most everyones opinion that it will provide me with the most useful data out of all the Dyno's.

Again, Thank you, Popsracer

Well, I'm going to stick with my Fantom. It's the only one that is being used at our track. No one uses the CS or Robotronic and there is only 1 CE.

It would be too hard to compare my motors with all the other guys if we weren't all using a Fantom.

I'm the only one in my area that has a Robitronic dyno. I don't mind it... If I want to compare my motor to others, I'll ask them to let me dyno it on my dyno... or I'll dyno my motor on their dyno...

Dynomohum-I have a set of Fantom Dyno Runs. I reverse engineered the Flywheel inertia like you did and came up with 4.10x10^-5 kg-m^2. This is similar to the moment of the Robitronic Dyno flywheel. I took a different approach to calculating Power than you did to avoid the following dilemma.

"I'm using Fantoms figures for RPM and time interval, as given from the Facts II 'time based motor data'. I think torque should be calculated using delta RPM that uses 'present_RPM - previous_RPM', rather then 'next_RPM - present_RPM' like Fantom seems to be doing. Past, present, and next reffering to time intervals that are associated with the data as given by the Fantom..."

Instead I made a graph of Angular Velocity vs time based on the RPM data in the data file of a stock motor. I fitted a fifth order polynomial to this data so that I would have an equation to predict the instantaneous angular velocity at any point in time. The derivative of this equation would give the instantanious angular acceleration at any point in time. Torque can be calculated from Torque = Rotational inertia * angular velocity. The Power in Watts can then be calculated as Power = Torque * angular acceleration. The graph of my calculated power and Fantoms are very similar. Be glad to share the spreadsheet with anyone. E-mail me at JohnStranahan@aol.com

And of course the RPM data that we are using is calculated from more basic measurements that have the same dilemma, where to center your average. If I had a set of the more basic time measurements at each rotation of the flywheel, I coud bypass the dilemma completely.

Have not tinkered with the efficiency yet.

DynoMoHum & John S;

You guys are WAY too smart for me. Have you ever considered working on flying saucers? :wave:
REALLY, I am very impressed with your methods of Dyno comparisons. Why don't you use your calculations to write a better program for the Fantom Dyno.

Popsracer

I agree with popsracer! My brain hurts just reading your results. It would probably explode if I tried to figure all this out for myself.:lol:

I also believe that the main problem with the Fantom dyno is the software. I'm just don't know enough about programming to write my own program. I have, however, created a schematic diagram of the electronic circuitry inside the dyno itself. I just don't have the equipment to extract the prom data.

I guess I should state my main point another way. I don't see a problem with the Fantom Dyno Software. Seems to calculate power and efficiency OK.

I was wondering if anyone knows what fantom has up their sleeve for their new nitro Dyno? I am either going to make my own inertia dyno or get the fantom one if it looks good.

My other question is how do you figure out angular velocity? Would Time Base * Angular Velocity = Torque work for a nitro motor if I had the time base for a set acceleration? Or would it be better for a nitro motor to use Torque = Polar Moment * rpm per second / 9.551? :confused: I hope I don't come off sounding like a idot, I'm only a Senoir in HS. Thanks. :wave:

TMFU:

A couple of ideas to throw out to you.

1. I don't remember how I got the raw (number of revolutions, time) that the Fantom calculates everything from. If we get a snow day tomorrow, I'll see if I can get you some raw data from the DOS version. I think these values are better to work from: I seem to remember the RPM's are calculated with a centered difference formula, the acceleration from a centered difference also. Both would be second order accurate. There is probably enough round-off error in the rpm numbers you wrote down to give a couple percent error in a calculated peak power, but the Fantom calculation wouldn't have that. (Just a guess/recollection at this point, it's 10+ years since I tried to sort all this out myself.

2. Another thing to "screw with ya" (ha, ha). Run the CE dyno going from low amp draw to high. Let the motor/magenets rest overnight, then do the same test, but go from high to low. The curves will not be the same. It seems whatever we do for dyno comparison, the "history" of the test plays a role in our stuff. To make comparisons, you have to have the same "test history", not just the same loads.

Pops and Snuffy... John has lost me... I'll leave the space ship building to others... Now I might be willing to take it for a test drive and give my opion of it when it's done... but I'm no engineer... I did manage to figure out that John was saying he didn't think that Fantom is/was doing anything wrong.

John, If you don't think there is anything wrong with the Fantom's Torque, power, and effciency numbers, then can you offer some explinations for a few things that I see as very odd?

For starters... Why is the power output and efficiency reported by Fantom so low? Low when compared to the TurboDyno and/or the Robitronic dyno. On a TurboDyno at 5 volts, a average stock motor can easily achive 85 watts of peak power, and also has no trouble at all achiving over 60% peak effciency. While from what I've seen on a Fantom a really good stock motor will be hard pressed to achive 70 watts, and often they put out 65 watts or less. On the Fantom I have rarely seen or heard of a motor that will achive more then about 50% peak effciency. This all seems very odd to me.


Secondly how can it be possible that a Ex-Spec motor that will put out over 105 watts peak at 5 volts, yet only barely is able to show up as 54 watts on a Fantom dyno???? Not to mention this Spec motor is greater then 19% better then a perticular Paradox on a Robi, and more then 24% better on a TurboDyno, yet the differance between these same two motors on a Fantom only shows as being 3%...


How can this be? Surely there must be something wrong with the Fantom... either that or the TurboDyno and the Robi are both wrong.

Quite frankly I don't really see how the TurboDyno could be wrong... It measures torque and I can verify it's numbers are quite accurate. If I had to put all my faith in one single dyno it would have to be the TurboDyno for giving accurate numbers.

For more details on this second odditiy, check out this page...

http://www.wiltse.net/facts.htm


I will send you a message requesting your data... At this point I really don't understand how your caluclating things... I would love to hear any thoughts on the odditys I've spoke of earlier in this post...

Dyno, in a few words, who cares what the exact numbers are that each dyno spits out. the key here is repeatability, and user friendliness. i started out with a turbo dyno, but after a year decided to switch to a fantom.... and continue to use the same dyno 8 years later. the key here is, it works for me. i don't care if i win the "biggest number" dyno war. what matters to me, is being able to tune my motors so i can go out and be competitive. that's it. as a side note, in the real world, i dyno test and tune race car engines for a living. the really saavy race car teams don't care a lick what numbers my real dyno spits out at the beginning of the day. the only thing they are interested in is the net improvement at the end of the day! 'nuff said.

RWB... I'm likely only to have my TurboDyno for a few more days... I will have to make sure I run a backwords and forwards test before I sell it. I have noticed that if I run a test what has steps of say 20 22 25 28 and 30 amps, then run another test with steps of 28 30 32 35 40 and 45 amps... the power numbers will not be exactly the same for the 28 and 30 amps steps of both dyno runs. However they are ussualy within a couple percent... I've not given this a whole lot of thought however.

My local Fantom owner (ther's only one guy I know that has one), says he regularly sees that the second dyno pull on his Fantom will show better numbers then the first pull...

My personal observation of consitancy on the Robitronic is that most motors will repeat the data easly within 1%. Ocasionaly you get a motor that will not repeat very well, but I suspect this is due to motor problems rather then dyno problems. I've got one motor that recorded a peak of 128 watts at 7 volts when I first got it... I've used it so much that the comm is down to about .271" and I still get dyno runs from this motor that are very close to the orginial run I made over a year ago. THis motor has always been my favorite stock motor. (P2K)

I do understand that the ideal torque/RPM measurments would be more or less instantainious and/or that you calculate torque and power all based on a very narrow window of time... if you don't use a very narrow window, then you lead to problems such as I've been seeing... I also realise that the numbers Fantom is reporting may not be the most precise numbers it has available, that is it's likely to have more accurate numbers used internaly... (at least I sure hope they do)... Either way... I still feel there is something very odd going on with the results typicaly seen on a Fantom dyno. I really would like to figure out what it is... at this point for me, it's just nagging at me and I just can't seem to let go of it.

If anyone knows of a way to get the actual voltage seen at the motor during the Fantom dyno runs that could be helpfull... It could be that it's not actualy keeping 5 volts constantly at the test motor. Even a small amount of voltage variation could explain alot...

Pancar... I'm not trying to win any biggest dyno number award, or anything close to that. I'm trying to understand dyno and motors to the best of my ablity.

As stated in my previous post, I get excelent repeatablity with my Robitronic dyno... I do agree with you that repeatablity is key to having a usefull dyno.

Why am I still interested in the Fantom and the numbers it gives that I feel are very odd? Well it's basicly just curriosity, and the possiblity that my efforts may help or be of interest to others.

The single biggest thing that nags at me now about the Fantom is... Why can it not see a large differance between the output of a 21 turn EX-Spec motor and a 27 turn 24 degree stock motor? Why does this nag at me? Well... If a dyno is unable to show a significant differance between two obviously differnt motors like this, what is going on? It just can't be good as near as I can tell.

Well I'm no MIT physicist... but the Fantom is an accelerometer while the Turbo Dyno is more of a load generator. To me it seems they are 2 completely different beasts.

Yes... but power is power, torque is torque... it sure seems to me that a good dyno could measure and/or calculate these in a way that would come very close to what another good dyno would read.

In the case of this Ex-Spec motor the differance in power output reported is about almost 100% greater on the TurboDyno then it is on the Fantom. I'd like to see a MIT physist explain why.

Originally posted by DynoMoHum
is there anyway to export data from the Fantom into a text file that Exel could read?

You can export it directly to Excel. When you save a motor it will as you if you want to save it as an ASCI II file. Answer yes. Open Excel and import the file to a spreadsheet.

Well... I'm not an MIT Physicist, but I did get 3 years of pre-engineering before settling down and getting a BS in Physics from a smaller college in the midwest... I confess that my Physics is too rusty for some of the detailed science involved in certain dynos, but I do recall one principle of Physics that probably plays a big roll in this discussion. Werner Heisenberg is the scientist who first put forth what we know as the "uncertainty principle" -- this, in simple terms says that when we measure something we either introduce a measure of error in the measurment or actually alter the thing we are trying to measure. For the Fantom dyno, for example, measurements are taken as RPM readings from a spinning disk by passing light through holes in the disk -- but those holes have a width, and the disk is constantly changing speed, so that even an average of the time it takes the hole to pass includes some error.

You can apply similar logic to almost every dyno out there and find minor flaws in one or another of the measures -- for example, a TD45 can produce flawed torque readings of the wires to the slave motor are allowed to bind on the sides of the hole where they pass down into the box (it's RPM measurements are also subject to an error similar to the Fantom's)...

None of this changes the central point: Know YOUR dyno, "baseline" your motors, note the way the dyno numbers compare (or DON'T compare) to on-track performance, and then GO RACE... I know guys who do well with a Tekin dyno, and I raced for 6-7 years using a home built dyno similar to the Buds unit. Do I do better now with my TD45? -- Sure! But I did "OK" before, because I knew what my dyno was "telling" me. You can't compare dynos -- heck, even Big Jim constantly reminds people to not even compare one TD45 to another!

For me, the issue is "Joe Racer" -- the person without a dyno, who trusts those labels on the motors in the hobby shop. That person is in a world of hurt -- totally at the mercy of Lady Luck, since those labels mean almost nothing. Like the person who started another current thread who was confused by Trinity's old and new labels, and thought that the much higher numbers from the Robi dyno (7v) meant a much better motor than the ones with lower numbers from the Fantom dyno (5v)...

I think we may need to start a new thread on "Reading Dyno Labels in the Hobby Shop" or something. Joe Racer wants to know what motor to buy off the shelf and doesn't care about the science -- us hard core types don't buy off the shelf and we care a great deal about the science. Two completely different discussions...? agree? disagree?

Along the "scientific" path, I have a question as a TD45 owner to other TD45 owners: By definition, doesn't the TD45 "favor" motors with more efficiency? Their lower amp draw at a given load seems to produce higher torque and power readings, since the dyno must load that motor more heavily to make it draw a specific amp value. Thus, with the TD45, the tendency is actually to "tune" for efficiency (whether we realize it or not). For 4-cell stock oval, I'm finding that this tends to encourage use of lighter springs (to make the dyno "happy"), but on the track, I seem to end up going up one level of firmness to get the performance I want... Am I correct in my assumptions? Why does the dyno disagree with the track? Is this unique to 4-cell stock oval, or does this apply to other racing classes?

I'm not saying the TD45 is wrong, just that my experience has raised this question... I guess I should note that I've been using 20 amp numbers and based on another discussion it looks like 4-cell stock oval motors actually average closer to 25-27 amps -- is this my problem?

Thanks in advance and keep that info flowing!

Here's one data point for consideration -- it comes directly from Dave at Decco software...

"The Robi only looks at the flywheel speed twice per revolution where the Fantom looks at it 4 times per revolution so the resolution is lower by 50% on the Robitronics. "


So... going back to tfrahm's post above, there IS a measurement difference between the Robitronics and the Fantom.

I definitely agree.

I've found that motors that pull a lot of amps typically have a lot of RPM and low efficiency. And, on the TD45 they don't look that great (like, 100 watts and below at 20A/7V) but look awesome on the Fantom Dyno.

All my motors that pull low amps and have a high effiency all show much better power numbers on the TD45 yet look horrible on the Fantom.

-Rich

Originally posted by tfrahm
Along the "scientific" path, I have a question as a TD45 owner to other TD45 owners: By definition, doesn't the TD45 "favor" motors with more efficiency? Their lower amp draw at a given load seems to produce higher torque and power readings, since the dyno must load that motor more heavily to make it draw a specific amp value. Thus, with the TD45, the tendency is actually to "tune" for efficiency (whether we realize it or not). For 4-cell stock oval, I'm finding that this tends to encourage use of lighter springs (to make the dyno "happy"), but on the track, I seem to end up going up one level of firmness to get the performance I want...

TMFU:

It's been a while since I've seen a Robi dyno. How similar is the Robi flywheel to the Fantom flywheel. I was just thinking that, just as is the case for the CE where the loading (up or down) changes the readings due to heating of the winds, knocking off some of the magnetic flux at the magnet tips, etc, does the choice of flywheel and how it "stretches" rmps vs. time influence the values measured? And how much is this influence?

The Robi flywheel has 4 different sections, that means that it trips the sensor 4 times per revolution. Where they get twice I dont know. Again this tells me more and more that they either dont know what they are talking about, or just trying to sell their own product.

Pat

I was at a race in Toledo last year where the guy that writes the Fantom software was there. He went up to Josh Cyrul (I was pitting right behind Josh) and basically told Josh that he and the Trinity folks have no clue how to properly tune and build a motor.

Whether his claim is true or not, I don't know. But, the way he did it and said it sure didn't make any friends.

So why has Trinity now switched to the Fantom dyno for all of their motors ???

hmmmm ???

Robi - expensive and couldn't handle motors lower than a certain wind (until recently). I think it was a 10 turn limit? Still made, so it is an option.

Fantom - cheaper than the Robi plus can handle very low wind motors. Still made, so it is an option.

CE dyno - no longer made so not an option.


So, there are basically two options. The Robi or the Fantom. And, since the Fantom can handle pretty much any wind motor it would appear the Fantom would be the dyno to choose.

Well with the gobs of money that Trinity has, I'm sure if the wanted to they could use the Robi for Stock motors and the Fantom for Mods... if cost was the real issue.

Yep! Even without using a different dyno, the "track dyno" tells me similar things. It's not that the TD45 is telling me "bad" things, it's just that you have to understand how it works -- since it is normally used with fixed amp steps, a motor that pulls more amps will automatically produce lower power readings at 20 Amps for example.

(NOTE: My TD45 is "conservative" with it's numbers, so don't compare 'yours' to 'mine' -- my best reading ever at 7v was only 98 watts at 20A/7.00v, with most of my 'good' motors being in the low to mid 90's...)

I've found that my 97 watt motors (lower no-load amp draw, etc.) feel "soft" on the track and don't have the punch that these power readings would imply -- yet I have had very good on-track results with motors that "only" produce 90-92 watts (higher no-load amp draw). In fact, my 91-93 watt motors almost always out perform my 97-98 watt motors on the track. Clearly there is a point where this breaks down -- if I try a motor that shows in the mid 80's on power, it is usually a slug on the track, so this theory only goes so far.

This implies that for MY TD45, the "sweet spot" is probably around 91-93 watts, as this shows a motor that has 'power', but also has a bit lower efficiency, but has a good "balance" of performance. (This is why I talk about knowing YOUR dyno and what it is "telling" you.) When tuning motors, I'll initially tune for max power (shoot for that 97-98 reading), as that indicates an efficient, well built motor, then I'll go up on the spring tension a step, knowing that the power readings will fall into the low to mid 90's, but the extra punch (and reduced brush bounce) from the stronger springs will pay off on the track. It took me a while to figure this out, but the final payoff has been more than worth it!

Originally posted by Rich Chang
I've found that motors that pull a lot of amps typically have a lot of RPM and low efficiency. And, on the TD45 they don't look that great (like, 100 watts and below at 20A/7V) but look awesome on the Fantom Dyno.

All my motors that pull low amps and have a high effiency all show much better power numbers on the TD45 yet look horrible on the Fantom.

-Rich

Yeah, a buddy of mine who works in the dyno department for Tennecco Automotive said I might want to start using the TD45 in torque steps and not amp steps.

What do you think?

I'll have to mess around with that soon. Maybe over Xmas. :)

Originally posted by Rich Chang
CE dyno - no longer made so not an option.


Well... Actually not "quite" true... If Trinity went to the folks at CE and said they wanted to buy 10-20 TD45's -- I'd BET that they could work out a price that would "encourage" CE to build the dyno's they wanted!

I wish they would. :)

I was told they couldn't get certain parts. But, that could mean they couldn't get certain parts for cheap anymore.

It sure might be worth a try... I know that I've seen torque readings from 7.0 down to 5.5 at 20 amps, yet motors all over that range "work" on the track, with good "punch", but with gearing that varies widely from one extreme to the other... Using torque steps (assuming you had an idea of what the "target" torque was for you tuning), you could measure/tune all your motors at (for example) 6.5 for optimum performance...?

It would be interesting to see how motors you KNOW are good, but which don't put up the big power numbers at 20 amps would look at some specific torque value...

Let us know if you get a chance to test...

Originally posted by Rich Chang
Yeah, a buddy of mine who works in the dyno department for Tennecco Automotive said I might want to start using the TD45 in torque steps and not amp steps.

What do you think?

I'll have to mess around with that soon. Maybe over Xmas. :)

On a CE dyno if you run your high amp test first it will alway be higher than if you run it last. There is considerable heating of the test motor when it is run for 4 seconds at each step. If you run the high amp step last the motor has been heated by 5 four second cycles previous to the high amp step.

One difference between the CE equipment and others is that it uses a separate small set of lead wires to sense voltage at the motor terminals. This is probably a better way of keeping the test voltage where its supposed to be. I am curious also what voltage the Fantom actually delivers to the motor terminal. There is considerable voltage drop over the lead wires at high amperages.

If I had two dynos and one was always reading low it would be hard to tell which dyno is more correct without a research grade instrument. It don't think these differences are that important. It is helpful if different machines of the same brand would read the same. All that I can attest to is the Fantom calculations seem to be OK. If you calculate power using the large .1 seconds steps of the ASCII file without some calculus you are bound to incurr some error that the fantom software does not have to deal with as it uses finer steps.

DynoMoHum

I know for a fact that the actual voltage at the motor is NOT 5v. I've measured it during a run. At the beginning of a pull it dips and ramps up. Very similar to what an actual battery pack. The voltage control circuit does get feedback from the motor to adjust the voltage as needed. The highest I've seen the voltage at the motor is 4.85 or so.

I've also talked to Al at wizard, the guy that builds theese things.
His calibration procedure involves putting a load in place of the motor and making sure he gets 5A at 5V with the load. He has a special program for this.

Rich:

I'd ask your friend why he think's that so. I can "understand" amps since that is related to the power source (the battery pack) and that you can to tune the power band to make use of that power.

If you test in torque increments, it's just like testing in rpm increments. A torquey motor would show one part of the power band, an rpmy motor would show another part of the power band, but how would you compare the two if the power bands don't overlap.

It's not torque, but the power and then choice of gearing to make use of that power. So I'm not sure what your friend is getting at "for electric motors." Now internal combustion engines, I could understand measuring based on torque steps.

Damn!!! guys.

I started this thread because I wanted to learn how to use my fantom dyno to tune motors, Not to start a "which dyno is better" war.

I think some of you are taking DynoMoHum's work and observation a little out of context. I really don't think he's trying to slam the fantom or any other dyno. He's just trying to understand it, as am I.

All dyno's have advantages and disadvantages.

The Robitronic Dyno also has small wires that attach more or less directly at the motor, these wires are used for measuring voltage. This is just like the CE TurboDyno. I did not pay that much to the wires on the Fantom, next time I use it I will pay more attention.

Along those same lines, I have played around with adding short peices of wire between the Robitronic motor leads and the test motor. I don't remember the exact numbers right now, but there was something like 1 watt drop in power for every inch of 12 gauge wire added. I don't think this alone would account for the realtively low power readings of the Fantom. In the tests I did with the EX-Spec motor and the Paradox motor, they both had the same hook up, so it really should be a non issue if we look at the numbers in relation to one anther. Either way the small voltage sensing wires are a good thing if your attempting to get accurate power and effiency numbers. This could easily account for some of Fantom's low power numbers if they don't use this type of thing to measure voltage.

As for the CE and efficency stuff that Tfram is talking about... I have to re-read that and see if I can grasp it a bit better... I am however quite convinced that 20 amp numbers are only a small part of the picture in todays racing... especialy in Oval racing. If I was using a TurboDyno I'd look at 28 amp numbers as much or more then 20 amp numbers. Anything bellow 20 is pretty much not usefull... I see Big Jim basicly says that the 15 amp setting is just to get the motor warmed up/moving... I'd actualy be more inclinded to use 15 20 25 30 35 and 40... (or maybe 38)... Sometimes it's hard to get a CE TD to force a stock motor to pull 40 amps... I think many stock motors should peak between 35 and 40 amps, and I do beleive that peak power is very important these days.

I know for sure that I am quite easly averaging at least 25 amps in my stock oval racing, and higher in 19 turn. My batteries are starting to become a limiting factor from what I can tell.

12th scale road course is differnt... 20 amp numbers are probably still pretty important. However I also think 25 and 28 amp numbers would be a good indicator of acceleration in 12th scale...

I'll have to look at my schematic of the dyno but I don't believe there is any actual "measuring" of the voltage to the motor at all.

Hi,

Yeah, I asked him to post on here. This stuff is pretty much over my head (but I have definitely enjoyed and learned some stuff reading it all) so I would have no idea how to explain any of this. I just use the dyno to give me an idea as to what the motor is producing and work from there in conjunction with track performance. I'm definitely not getting the full potential out of the dyno readings. :)

-Rich


Originally posted by RWB
Rich:

I'd ask your friend why he think's that so. I can "understand" amps since that is related to the power source (the battery pack) and that you can to tune the power band to make use of that power.

If you test in torque increments, it's just like testing in rpm increments. A torquey motor would show one part of the power band, an rpmy motor would show another part of the power band, but how would you compare the two if the power bands don't overlap.

It's not torque, but the power and then choice of gearing to make use of that power. So I'm not sure what your friend is getting at "for electric motors." Now internal combustion engines, I could understand measuring based on torque steps.

Man Snuffy... your now giving us some info that could probably does explain alot... If the voltage is droping significantly bellow 5 volts during the test then the output numbers are deffintly going to be low. Just how low will depend alot on what the actual voltage is... If the effciency numbers don't take into acount the lower input voltage then tye too will be low...

Power = Voltage * Current... at 35 amps 1/10th of a volt is 3.5 watts. at 29% effcinecy that is 1 watt of output loss. It's critical that voltage is maintained to at least a 10th of a volt in my opion. Voltage drop is fine if it is consistant, repeatable, and you take it into account when you calculate effciency... but if you don't take into account the voltage drop your going to have all kinds of issues come up.

Generaly speaking the higher the load(amp load) the harder it is for a power source to keep up it's voltage. Higher the load, the more critical the voltage level is to maintain consistant and accurate numbers on a dyno.



One last thing Snuffy... I don't think too many folks here misunderstand my comments here... maybe one or two that have commented... but I beleive this discussion here has be very productive and quite helpfull to me. I think most others see it that way as well.


I do beleive it's very important that a dyno user understands his/her dyno very well... If you don't understand your dyno, you'r likely to misinterpet it's data... and we wouldn't want that. :)

Typically, motors become more powerful and less efficient as the brushes break in more. There's a point where this stops being true but that's what happens in general.

The problem is that it takes less torque to make a high amp draw motor (the brushes are full and overlap more) run at say 20 amps than a motor with more narrow brushes. Just because the motor makes more power at a given current doesn't mean that it doesn't make good power.

Looking at our motors by current draw doesn't make much sense with the new batteries because we don't dump. Have you ever heard anyone bragging about how much power their big block Ford makes at 20 gallons per hour of fuel? Nope... In the end the only way to compare 2 motors head to head is by using either RPM (like the auto industry) or by torque. At a given torque, the motor with the higher RPM makes more power regardless of the current that it takes to get there.

Amp draw is still very important because it can have an affect on efficiency. An inefficient motor will not perform at the end of the race because it's going to get hotter. More efficiency=cooler motor.

You can estimate the torque settings required with a little work on the track using your rollout and split times. Or just use settings in the area that you normally look for (around the 20-25 amp range).

BTW: I've seen over 40 amps in 12th and about 25 continuous.

DynoMoHum,

I agree that this discussion has ben very helpful and extreemly informative. It just seemed like some posts, the last few days, were a little on the argumentitive side. It's not a complaint, just an observation.

Knowledge is power. I for one have enjoyed participating in this thread emencely and have learned quite a bit.

I also want to personally thank you and everyone else for all the effort put into this thread and the sharing of your findings and knowledge.