If Mike Golden or someone could provide a utility to aid in gearing selection based on what you selected as the criteria power/rpm/etc.
It would sure be useful to us guys that don't have 10 yrs experience racing with electric motors.

Popsracer

Mike is going to have to start charging for his program if it gets much more usefull... :)

Racers of all types that I know use roll out...

I can tell you this right now pops... motors, gears, and such are a very minor part of racing for a average driver it's almost not funny. What I mean is that most of us racers driving and other car setup issues are a much bigger issue.

Even for myself, this stuff is not going to do much for my on track proformance. My driving just really isn't good enough for it to matter that much. I personaly love playing with motors and dynos, and that's the main reason I do it. It also helps me understand fully that my driving is a problem...

I know Fred and Rich personaly, we often race at the same places, and I know these guys are good enough that getting the most out of a motor can actually help them a significant amount. I know other racers that couldn't tell the differance between a GREAT motor and average motor under any conditions. I am somewhere in between.

Fred, Rich, and nearly any good driver will tell you that the secret to speed is to keep it in the corners... If you slow down too much you'll never keep up with the really fast guys... I'm learning that this is also a huge factor in how high you can gear a motor... I could probably gear either Fred or Rich's cars about 2 teeth higher then I could gear my own car... they can keep the speed up in the corners and I can't... so their cars never get so low in the RPM range that they really work hard like mine would at the same gearing...

So... keep all that in mind when you start trying to apply dyno data to on track proformance.

Mike is going to have to start charging for his program if it gets much more usefull... :)

Racers of all types that I know use roll out...

I can tell you this right now pops... motors, gears, and such are a very minor part of racing for a average driver it's almost not funny. What I mean is that for most of us racers driving and other car setup issues are a much bigger issue then motor tuning.

Even for myself, this stuff is not going to do much for my on track proformance. My driving just really isn't good enough for it to matter that much. I personaly love playing with motors and dynos, and that's the main reason I do it. It also helps me understand fully that my driving is a problem...

I know Fred and Rich personaly, we often race at the same places, and I know these guys are good enough that getting the most out of a motor can actually help them a significant amount. I know other racers that couldn't tell the differance between a GREAT motor and average motor under any conditions. I am somewhere in between.

Fred, Rich, and nearly any good driver will tell you that the secret to speed is to keep it in the corners... If you slow down too much you'll never keep up with the really fast guys... I'm learning that this is also a huge factor in how high you can gear a motor... I could probably gear either Fred or Rich's cars about 2 teeth higher then I could gear my own car... they can keep the speed up in the corners and I can't... so their cars never get so low in the RPM range that they really work hard like mine would at the same gearing... This is as true in oval racing as it is in roadcourse...

So... keep all that in mind when you start trying to apply dyno data to on track proformance.

I'll try to explain what I'm talking about and add a disclaimer.

In comparing the data (Disclaimer: assuming that the gear is optimized for motor 2)given the same gear ratio, motor 2 will be faster on the track. It will pull max power in the turns and taper down from that in the straights. Even though it uses more power in the process it will be faster until it heats up, then it will probably take the MVP style power dump.

Motor 1 will be undergeared and never really use it's entire powerband. If geared up it will perform similar to motor 2. Perhaps marginally better near peak power and marginally worse at high speeds (low current draw).

I would actually choose to run motor 1 because it has a wider powerband and is more efficient. Motor 2 will probably heat up and fall off at the end.

If you read this before the edit, all I can say is noodle fingers...

I see what your saying now... Your talking about if you optimized the gearing for motor two in your car, and then simply put in motor 1 and didn't change anything else...

Under those condtions I beleive a realatively bad driver like me, might actualy go faster with Motor 1... Because I would be going slower in the corners and because it was undergeared it would acclerate better for me as I came out of the corners slower....


We are deffintely getting closer to the same page on this... I'm not sure I agree with your final assement of how each motor would proform if they both had their own gear that was optimized for each motor... however it does seem that we pretty much agree that what ever differances there are, they are reasonably small..

I also am not sure how you figure motor 2 is more effcinent. Maybe when it's pulling more then 35 amps, but certianly not when it's pulling less then 35... Perhaps ther is a typo? or are we seeing something totaly differnt here?


I just thought of a Yoggi Berra(sp?) type saying for RC racerss... (actualy maybe for all racers...)

The faster you go, the faster you can go...

that is... the more spead you carry in the corners, the higher gear you can pull in your car, and this leads to faster entry into the next corner... I think the only point where this falls apart is on a really big track where you might get to the point where wind and rolling resistance prevents you from going any faster.

Originally posted by DynoMoHum
The faster you go, the faster you can go...

that is... the more spead you carry in the corners, the higher gear you can pull in your car, and this leads to faster entry into the next corner...

You just hit the nail right on the head! I've raced 1/12 scale 4-cell onroad, 4 and 6 cell oval, offroad truck, buggy, and 4wd, touring, etc. and one thing always holds true -- among the better drivers, corner speed becomes the thing that separates the TQ from the rest.

Example: I don't get to race oval as much as I used to, but I still enjoy it. I can build good horsepower, and I can gear it "just right", and the big dogs still eat me up. I'll pull them on the straight (but only because "my" gearing is lower than theirs so I can get punch out of the turns after bogging down), but I don't carry the speed in the corner (I have to set my chassis up "tighter" than they do due to being a bit "rusty"). So my HP and my straight line speed doesn't help me -- they lap me at under two minutes into a race... Using identical motors, they can always gear one tooth taller than I can -- that corner speed of theirs just compounds and multiplies by virtue of their ability to pull that extra gear...

Guys;

I am definetly not a Pro caliber driver, but I am a respectable club level driver that most always finishes in the top 3 spots for the "A" Mains. I do believe that with most of us having less than perfect laps. That any little extra bit can only help you overcome lost time from the occasional bobbles. I can't remember how many times that I have errored or been hit and sent to last place and then been able to make it back in the top 3. WHY, because every bit you do to improve your TOTAL package of Car, Driver and equipment, can only help to make you faster in the long run. It's ALL a Delicate balance of Man and Machine, no matter what your skill level is.

Popsracer

That's good pops... I could not remember what level of driver you had said you were... You are likely to learn alot from the dyno...

Hey, I took the Robi text file and put both M1 and M2 in a Excel spreadsheet... made it calculate wheel speed and torque at the wheels after gearing is applied... If I gear M2 with a 21 tooth pinion and a 81 tooth spur, and use a 24 tooth pinon and 81 Spur on M1, the torque and RPM is so close to identical that it almost amazed myself...

Sometime this weekend I'll put up the spreadsheet , graph, and data on a web page.

I'm telling you these two motors put out exactly the same power, torque and RPM once gearing is applied correctly for both. The only thing significantly differnt between the two is that M1 has a bunch more effciency from 50% to 100% RPM... In my opion the effciency advantage alone is the only thing left to sway the choice of which of these two motors to choose.

Ok. Now my brain really hurts.:lol:
It's this that makes me understand the statment "Ignorance is bliss"


I have learned a lot about motors, dynos, and what dynos tell you about motors. The only thing I'm not too clear on is how to apply this knowledge to get me around the track faster.

Of course using the dyno to tune/find my best motor will get me around the track faster. I don't think I understand how to use the dyno to pick a gear ratio. I not even sure I can pick the right motor. From all this discussion it sounds like the right motor doesn't nessasarily have to be the motor with the highest peak power.
It sounds like the best motor for the track is the one that has the peak power in the right place. How do I determin where that place is?
And What can I do to move the peak power to where I need it to be?

Good stuff dynomohum. Its nice to see people who are able to use the latest technology, and better yet understand it to yield lower lap times. I saw the rejection of your wonderful data you were so thoughtful to provide over on that "moronothon" motor site recently :)
Those guys who are stuck using technology from the eighties are still making horsepower from the eighties anyway! Personally I appreciate your work here as should any one who wants to learn.

well thanks for the support... however I really would appreatiate it if we could keep insults to anyone down to something that aproaches silence... I have learned ALOT from just about EVERYONE on this board. I also would like to say that I am not thoough figuring this out... Two months ago I didn't beleive any of what I'm currently thinking about how to effectively judge one motor vs. another. I was totaly convinced that veiwing data in relation to amp input was the best way to go. I still can look at data that way and make alot of sense out of it. So I'm not willing to say viewing data in relation to amp input is completly wrong, however I'm getting close to that point... :)

I know for sure if it had not been for this discussion right here I would never have started to ponder the path that I'm on now. Tfram, Rich, Fred, John, Snuffy, popsracer, Mike, and everyone else that has been contributing to this has been a HUGE help to me.

What Tfram was asking earlier about how viewing motor data in relation to amp draw and how it can bias you towards thinking the most effcienct motor is always the best motor is what I'm trying to ponder mostly right now. Especialy as it relates to how a person could use a TurboDyno more effectively...

I think there's going to have to be some math involved. At this point I just don't see any other way around it. Basicly the issue I'm thinking is needed is to know exactly what RPM a motor achives at some minimum power figure. Then you view all torque and RPM (and in effect Power) by looking at this with gearing involved. Torque get's multiplied by the gear ratio, RPM gets devided... The only way it seems to work is if you pick the correct gearing point... and I think this MUST be done using POWER as the common element for the point you use.

Robitonic's data in relation to %RPM sort of does this... but they use some minimum value for torque as the point for max RPM. This is flawed however... but it does usualy get pretty close. They also don't modify the torque and RPM figures so they are corrected for gearing, so it still kind of confuses the issues.

For all who still are thinking I'm crazy... Well I would have thought the same thing a few months ago... and I'm sitting here awake at 6Am on a Saturday moring trying to figure out a way to convince myself and others that I'm at least on the right path...

maybe I am crazy... when I can't sleep because dyno data is bouncing around in my head, and it's all just a toy car... that is saying something... :)

I have to agree.
This thread really does what's suppose to do.
People with different opinions giving there point of view.
And being open minded to listen what the other has to say.

We do not have to agree about everything, just as long as respect each others opinions.
A healthy discussion is what's happening her.
I too have learned quite a bit from all of you, but maybe not figuring out everything as specific as you guys do.

Regards,
Pizza.

One thing that i think needs to be said is not to overthink all this data. It still really comes down to one thing: The motor with the best balance of power and efficiency usually runs best on the track. After 10 years of racing before i got a dyno, I learned all this stuff based on feel on the track. Now i am able to confirm my gut feelings with the dyno. The combination of the two is hard to beat, when your dyno confirms your gut feeling for what gear or motor to run you know you are really on the right track.

DynoMoHum,

You read it before the edit...I was writing a report and posting at the same time so everything was running together. Motor 1 is more efficient.

The motors will be the same speed at peak power as long as you compensate for gearing. They make the same power. When you gear motor 1 to hit it's maximum load slightly above peak power it will probably be slightly faster out of the corners and about the same at the end of the straight.

OK, here is the view that I belive tells the story pretty effectively. My opion is that geared as shown in this graph, there isn't a racer in the world that would be able to tell the differance between these two motors on the track. At least not for the first minute or so. Eventualy M2 will drain the battery of more power then M1 does, and the batteries will have less voltage due to the way bateries behaive. Motor 2 will also eventualy get warmer then M1 will, and M2's effciency and power output will delcine more as a result... so in the end you would stay faster for a longer period of time with M1.

http://www.wiltse.net/images/geared.gif

If you'd like to look at the data for these motors and play around with the gearing and see what happens, you could download the Excel file I used to make this last graph... It's really kind of interesting... as you can see what changing one tooth will do... or changing the Spur gear, etc...

www.wiltse.net/zips/M1vM2.zip


I think this whole study in these two motors and the various ways of viewing the same data point out some down falls of nearly every commonly used way to display dyno data... I'm thinking a graph like this last one is the best way to veiw things... Mike Golden's DynoViewer creates a very simmilar graph... however there seems to be a bug/feature that makes it impossible to see differance between the dotted lines and the solid lines...

Snuffy... I'll have to get back to you on your last comment/question... The basic answwer is Peak power and effciency are both critical... Large peak power with poor effciency will not work well... neither will high effciency and low peak power.

Mayhem basicly said this... in his last post... however I beleive you can figure this out with a good dyno and some knowlege of how to best interpet the data. It's my mission to figure out the best way to do this. I am very confident I can do it with a Robitronic Dyno...

Today I've been trying to figure out the best way to go about it with a TurboDyno. I think the best way would be to plug the numbers in a spreadsheet and figure it out based on gearing... However I've been looking at my Robi data and trying to imagine what I would do with a TurboDyno and only 6 steps to work with....

I think in 90% of all cases the following method would work reasonably well... for 6 cell racing... use the following steps at 7 volts constant... 10, 15, 20, 25, 30, and 35. Find the motor that has the highest power at 30 amps. Most likely this motor will also have the higest power numbers at 35 as well... Peak power should come somewhere very close to 35 amps... but it may not be super critical if you don't find the exact location... The next part of the process will be to evaluate the effciency of the motor, do this by examining the rest of the numbers... If you find a motor that has awesome power at 30 amps and also has good power at 20 amps, then you have a good motor... I couldn't tell you exact numbers to look for however... You'll have to figure that out on your own... I would say that 100 watts at 20 amps is still a good number to shoot for, however if your 30 and/or 30 amp numbers are not also excelent then motor will not be as good as it can be...

For 4 cell the process would be simmilar, but I think peak power is probably between 25 and 30 amps at 5 volts, so 35 amp will likely be lower then the 30 amp number on nearly any stock motor...

Dynomohum- Only rub here is the ratios selected have to actually work in the car. A slight difference in the ratio selected produces distictly different curves on your spreadsheet. When you multiply the ratios in your spreadsheet by the car ratio (which you might add) you get quite a spread in gears. One is very low for a stock motor one is quite high. More than say going from a green machine to a P2K in my experience, but then maybe not in your experience. Looks like an interesting approach.

I'm a pan car guy mostly... so this is the exact ratio the car would see from motor to wheel in a pan car...

If I was interested in a car with a gear box, I would take into account the final drive ratio including the gearbox... once you did this, you could acomplish the same thing.

Tire size and roll out ultimately need to be considerd as well... The spread sheet as it stands now, is just a starting point. However in my humble opion, it proves that these two motors could be geared to make them have virtualy identical RPM and Torque at the wheels when geared apropreately.

Yes the curves change significantly when the gears get changed.... Just as in real life... :) I don't beleive there is any mistake in what I did, unless you are looking at it from the perspective of a guy with a gearbox in his car... You are correct that this would be a nice feature to add... as would rollout.

Any one got a typical gear box drive ratio that I could start with? I'm not up on my gear box car info...

For what it's worth M1 is a P2K and M2 is a GM3... neither of these motors is what I would call excelent. That is, I have other motors that are better, and I have seen a few other motors that some of my competitors have that are MUCH better (when tested on my dyno). I'd call these motors average... and I personaly would never use a motor that didn't proform at least as good as either one of these does. I also beleive this is quite typical of the differances I often see between a typical GM3 and a typical P2K, and this is exactly why I don't perticularly care for the GM3 motors. I don't really mean that as a slam on GM3s, but this really is very typical of what I see with both of these types of motors.

Dyno,

I've been looking at your motor comparison sheet in Excell.
I like it !

How can I use it myself?
Import my own motordata into it, and fiddling around with gearing?

BTW did you use the robi gear calculation at first to check its recomendation?
Or does it differ from your own findings?

Thanks,
Pizza

Mike Golden's DynoViewer basicly does the same thing as my spreadsheet, it just doesn't give you actual torque and RPM at the wheels the way my spreadsheet does. With Mike's DynoViewer you can load data direct from Robitronic text files, or past Fantom Facts II data in from the clipboard.

My spreadsheet is pretty easy too add other Robitronic data in, but it would be harder to try and make Fantom data work...

Robitronic's gear utility has what I consider to be a flaw... it uses some minimum torque amount as the common point for calculating gearing. This doesn't work all that well... In my opion POWER must be used as the common element... So, no I didn' t use Robitronic's gearing utility for this. Mostly I just played with it, till I got the torque curve to match up...

I've played with about 5 of my best looking older dyno runs, trying to test the theory that Peak Power is the single biggest facotor in determining how well a motor will work for a short duration. It seems to hold up very well. Effciency is the next most important factor as far as I can tell. I don't have a fool proof plan for determinging just how much efficiency is enough and/or best... My basic thinking is that if your loosing more then a couple percent of peak power by tweaking things to get more effciency, your basicly playing a loosing game.

Based on my early exploration, I think the concept of a wide or narrow power band is a myth... that is of all the motors I've put in my spreadsheet, they all show the same basic power curve when you gear appropreately... I'll try and demonstrate this soon with graphs and such.

Right now I want to try the same basic idea with some TurboDyno data... Since I sold my TD this weekend, all I can do is find some old data to play with... I really want to see if this what I'm seeing only applys to Robitronic data or if the principle will hold up with other data.... For the time being I'm not going to monkey with Fantom data much, because quite frankly I still don't trust it... On the other hand I have Snuffy's data already in a spread sheet and it wouldn't be hard to play with.

I've started to anyalize some TurboDyno data I had for the Monster and a P2K... the same two motors that Mike Golden did a anyalisis of usig my Robitronic data for the same motors...

Anyway... I can get the slope of the Torque curves to line up in a very simmilar way to what I see when I use the Robitrnoinc data... I have to use drasticly differnt gear ratios then I expected to do it... and even then the RPM range from start to finish is differnt with the two ... Given the the fact that the TD is a breaking type dyno, and the Robi is a flywheel, this may account for it all...

Basicly I'm still tring to figure it out.

I'm currious now about the Fantom and if I can get data from it to show up simmilar to what I see with the Robitronic data...

FYI...

For those of you that may have at one time or another doubted the voltage curve that the Robitronic dyno uses when it tests motors... I was just trying to evaluate the differance between a ESC that I felt was causeing me proformance problems, and a new Keyence Zero V. I jamed the dirve train on my car, with a 19T chameleon moto in it, measured the voltage across the motor and the battery while I gave the ESC full throttle... on the old ESC I had just 1.4 volts across the motor, and 3.97 volts at the battery. WHen I put the new Keyence ESC in the car, I did the same procedure... I got 2.25 volts across the motor, and 3.0 volts at the battery... THis is all with a 4 cell GP 3300 pack, about 50% charged. Reading 5.1 volts at rest.

So what does this mean? Well first off, it means my old ESC was a big burden on my proformance and I should really see a differance on the track the next time I go racing...

I went back and looked at a recent dyno run of this chameleon when tested on the Robi at the 5 volts setting.... at 69 amp (startup current) the Robi was putting 2.3 volts to the motor... Based on my observation during my ESC evaluation, I'd say the Robitronic dyno is doing something pretty reasonable with the way it does it's voltage curve thing...

Makes you wonder how valid a dyno test at a constant voltage is likely to be...

Here are my thoughts on Efficiency...

With an electric motor, we put Electrical Power into it and get Mechanical Power out of it. When tuning one of these motors, we would like it to convert all of the Power we put into it to Mechanical Power. This would be 100% efficient and impossible.

Now let me back to the point. When we tune a motor, what we are really doing is maximizing the efficiency of the motor at a specific Power Input. We can tune a motor at higher Power inputs or Lower Power inputs. Any motor that puts out more Output Power at the same Input Power is always more Efficient, as per the definition of Efficiency.

So we can tune a motor to be the most efficient at the Power Input that we feel we use the most while our car is on the track, or we can tune a motor to be more efficient at its peak. Either way we are still making the motor more Efficient somewhere with respect to a specific Power Input.

Efficiency is King in the motor tuning world, but the real question is, Where do we want the motor more efficient?

I totaly agree with your comments Mike. Now the question becomes, how best do we use a dyno to simulate as close as possible the condtions the motors will see on the track... Or at least get as close as possible. Also, how can we view this data in a way that doesn't mislead or confuse us?

I also beleive there could be a lengthy debate about what/where the effciency is best placed. For instance... should we average 20 amps, 25, or even 30 amps or higher to make most use of the power source and motors that we use???

Using Robitronic Dyno data, I beleive I can show with very little doubt that with todays batterys peak power is likely to be much more important then power at any other location. Essentialy my present thinking is that if you had a motor that put out 132 watts at 28 amps and just 90 watts at 20 amps on a TurboDyno, it would be a much better motor then a motor that put out 100 watts at 20 amps, and 129 watts at 28 amps. I don't have enough TurboDyno data to make a good study of this, however I beleive I have plenty of Robitronic data that I can make my point with. My next project is to illustrate this idea as best I can. I suspect that I will be able to convince at least a few people that this is likely to be true.

This is a complete flip flop for me... so I'm still trying to convince myself of this as well... That's the primary reason I'm persuing this. It turns out that in my past motor tuning, it just happend that 95% of the time when I tuned my motors I got better peak power along with better power at lower amp loads... so my past dyno data was pretty much always backed up by my on track proformance and doesn't really conflict with my current thinking.

Ok, ok... I have something that I beleive every racer with a dyno should see. In my humble opion this study of two motors I'm about to show you, proves what Tfram brought up a few days ago... Does viewing data in relation to amp input inherently cause a bias towards effciency? It's not the dyno that is causing the bias howerver... it's the way we see the data...

I call this one... the great paradox... ( I wonder just how Trinity did come to name there older motors Paradox...)

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

I really do encurage you to look at this and try and understand it... I beleive this is a key to understanding dyno data in away that I've never before seen quite so well defined... I also beleive it shows just how important peak power really is... Please feel free to discuss this. If I'm not mistaken this will stand conventional dyno viewing procedures on it's ear...

By the way... if you want to play with the spreadsheet with these two motors in it you can get it here...

http://www.wiltse.net/zips/paradoxical.zip

I think I changed the gearing on M8 before I ziped that excel document. You need both motors geared to 30 tooth pinions to get the graphs to show as I have them in the web page.

I,ve always tuned for peak efficiency at peak power. Assuming gearing is correct this would be nirvana and one would think the motor is optimised. This is easy to do but at the sacrifice a decent power rating. In my experience it is better to let the peak efficiency number slide a bit to gain a few extra watts. I tune for the highest power number, within reason, then try to maximize efficiency without letting max power degrade too much. Gearing that is really on the money will make up for a lot of sins of a motor that is a little in-efficient. After a while you come up with certain parameters you need for a good running motor confirmed by track testing. I like the Fantom for the fact that you can really fine tune the gearing calculator to be very accurate. Mine is usually accurate to within 1 or 2 rollout points for any given motor.

Side Note.

Paradox was named because it was the first rebuildable stock motor.

DynoMoHum

If I'm understanding you right, your saying it's better to compare motors on the basis of RPM and not Amp draw, right??

dynomohum-I see that you noticed that maybe the gear ratio spread to make two motors look just alike at the rear wheel might be too wide also. You can probably make the rear wheel torque of any stock motor look similar by picking a suitable ratio. They definitely behave differently on the track, though. How about picking two motors that you have optimized the gear ratios on the track, using lap times, and using their ratio data in your spreadsheet. Then I think you might get a more realistic comparison that might lead to a better way to compare motors. Maybe you have done this and I did not see it.

Dyno,

Jon's suggestion is a challenge.
Can't wait to see the outcome on that one :)

CU
Pizza

Perhaps I was a bit too dramtic in my statment about how much value I see in this new way to view dyno data... and I didn't give enough information about the value I see in it. I'll try to better describe why I think that the best way to view dyno data is to apply some gearing and then compare the numbers...

So Snuffy, that answers your question... no I don't see viewing data in relation to RPM as being valid unless you apply gearing before you view it. At that point you could view in relation to RPM or torque equaly well I think. Adding the gearing is the key.

I told an untruth previously... to get the graphs I show on the web page I used gearing with a 30 tooth pionon and a 100 tooth spur gear. Previously i had mistakenly said I had a 81 tooth spur gear. The graphs actualy change a little when you use 81...

Yes, John, I beleive your idea is a good one. Take the two motors on the track, choose gearing based on lap times and then plug them in to this type of viewing senerio. It should tell alot. Unfortunately I don't own M7, and the guy who does, may not even know which of his motors it was/is. It was a year ago when I tested that motor for him.

My best motor is M8, a P2K. If/when I find another motor that has the charactoristics of M7, I will race it, and probably never look back on my days when my best motor was M8...

If you take my spread sheet and go up 2 teeth on Motor 8, you will see that the amp consumption of both motors gets to be more or less identical. At that point motor 7 has much better low end power, both motors then have nearly identical output at mid range, and M8 has higher power at high RPM. This makes it look pretty much like you'd expect from looking at the data in relation to Amp input.

If you choose 31 tooth for M8 it will be beaten in output power at all but the highest RPM range.

Choosing 30 tooth for both motors in my opion makes M7 have about 3% higher power throughout the intire RPM range. (actualy 30 toot for M7 30.5 tooth for M8 gives the most uniform torque/power advantage to M8. IF you gear this way, it's my opion that M7 will proforma better then M8 on all areas of the track. Current consumption will go up by aproximately 2.5 amps... So if you were like me, and your best motor was M8, and then you found M7, geared at 30/100 for each motor, your average current consumption would go up, but so would your on track proformance. Say if you were operating at a average current of 23... you would then be operating at about 25.5, however you would have better power on the track...

So... I really like this new way of viewing my dyno data. Only time will tell if the Robitronic dyno numbers are accurate enough to hold up to actual on track testing... I personaly feel I have a much better handle on motor proformance issues. I also feel I have a much better understanding of how gearing will effect the on track feel of a motor... If my Robi data is reasonably accurate, I feel confident that I could use this new dyno viewing method for chosing a proper gear for the new motor as long as I have a baseline gearing for a motor I already own.

If you down load the spreadsheet and start playing with the gearing I think you'll like it too...

Snuffy, I'll start playing with your Fantom dyno data in this mannor to see what it looks like when I do... I'll report back soon. I can tell you right now that your MOTOR TEST motor is likely to show up as the best motor.... (I think that was the name of the one I liked best)

Mike Golden,

I'm currious about what my spreadsheet is doing differntly then your DynoViewer... If I compare my Excel graph with gearing applied to your dyno viewer with some ratio changes, I can get some simmilar results, but the are not exactly the same. Apparently you and I are doing something slightly differnt then one another...

My procedure was to recaluclate torque and RPM based on gear ratios... I multiply the Torque by the final drive ratio, and I divide the RPM by the final drive ratio. I do this for each data point, and then graph all the data in relation to the newly calcluated wheel RPM.

One of the biggest differances I see with my method vs. yours is the amp numbers...

It seems that one of us is doing somethign wrong... either that or we are doing something that is not quite the same and can not be directly compared... I'm not sure which.

My head hurts reading these :)

How about this question for us mere mortals...

Using the Fantom FACTS software, I can get the required rollout to achieve a given number of laps. If I enter the TQ laps and time, and then get the required rollout, how do I know that the motor will actually "pull" that gear ??

In other words, when I dyno the motor and then go to the gearing screen, if the required rollout to make a TQ run is 2 or 3 teeth higher on the pinion than I've ever run on the motor, I would obviously be suspicious as to whether the motor can actually "pull" it and not be glowing red after the run.

Are there some indicators that you guys look at in this respect to determine whether the motor can handle the required gear ??

Thanks!

I am no expert at the Fantom or about the topic your asking about Goodwrench. However I have thought about a very simmilar thing in a differnt way. It's my beleif that there is no simple answer to your question. I belive it is highly dependent on car setup and driving driving ablity. It goes back to the idea I had that says... 'the faster you go, the faster you CAN go'...

To make it less complex lets talk about oval racing. The faster you can drive through the corner the faster you will be going when you come out of the corner. The faster you come off the corner the less force you will need to accelerate to a very high speed at the end of the straightaway. It all snowballs... This means the TQ guy's motor does not have to operate in such a broad range of RPM. It's my beleif that this allows him to gear much higher then you could if you can't get through the corner as fast as the TQ guy. He can gear for the most productive spot on his top level motor... you have to operate over a wider range, and it's virtualy impossible to get the same kind of power and effciency from your motor even if it is a top level motor.

Of course if your driving and setup are as good or better then the TQ guy... then you should be able to do what your asking about.

Does that make sense? and can you now understand why what your asking about is almost impossible to do? Or am I completely crazy?

OK... what does "can gear for the most productive spot on his top level motor" mean ??

Where exactly is the "most productive spot" ???

I'm still trying to figure that one out Goodwrench...

I'm thinking that at it's most basic level, it's geared in such a way that you you rarely operate at a RPM that is lower then the location of Peak power, yet you also do operate at Peak power a significant amount of time.

In oval my best guess is that you should be geared so you are operating at peak power in the corners. Then you'd accelrate up to the area where peak effciency occurs... My current thinking is that this is in the right ball park anyway.

Like I say... I'm still trying to figure out the answer to your question Goodwrench.

I agree that the faster driver can gear a little higher. About .1 higher on the overall ratio at ReflexRC in a touring car. Not a couple of pinion teeth unless it is a stock motor with a different style of armature say a P2K2 vs a P2K. You are not going to gear a stock motor up to draw 2.5 more average amperes unless it was really undergeared to start with. It will fade badly. The way a stock motor handles heat is an important consideration with on track performance. This is hard to simulate on the flywheel dyno's. The CE dyno does a better job of this due to the long test, but then there is more wear and tear on the motor as a result.

I think the only way to know if a motor will pull a gear is to stick it in the car and look at the lap time sheet. If the motor fades you will feel it toward the end of the race and see lower lap times as a result toward the end.

John -- that's exactly what I was getting at. Gearing it up to the point where it generates heat and fades badly.

I'd like to find a way to look at some data on the dyno run and be able to identify that the motor just won't be able to do a TQ run.

Thanks

So John, What kind of average amp consumption are you currently operating at in your racing? I haven't heard from too many TC guys on this topic.

Oval guys are telling me they operate between about 25 and 30 amps average during 4 minute races. The fast guys I race with rarely if ever fade much at the end...

I am at about 19 ampere average in the touring car. If I gear up .05 I loose considerable punch out of the corners,The car feels soft and unresponsive. I seems to be a very narrow range of gears on the touring car that will work well on the track. In the summer motor temperatures are about 180 F. Any higher and the motor fades or feels sluggish.

Interesting... 20 amps * 300 seconds is 6000 amp seconds... divide this by 240 seconds and you get 25 amps. 25 amps kind of the low end of what I hear fast Oval guys average. It seems that for oval... the smaler the track, the lower the amp average. (this seems counter intuitive to me... but thats what I'm hearing).

What size track is this that your running on John?

Also intersting is this... those last two motors I have shown data for have peak power at about 36 amps, and peak effciency at about 19 amps.

Actualy M7 hits peak power at 36.8 amps, and peak effciency is at 20.0 amps. M8 has peak power at 34.8 and peak efficency at 17.4 amps... Both peaks occur about 2 amps differnt on these motors.

Until I see differntly my theory on thes two motors is that you could go faster with M8, but you'd wind up averaging something close to 2 amps more doing it.

The track is medium sized indoor asphalt. Maybe about 120 x40 feet. Can't pull 25 amps average. The stock motor will be on fire. A touring car will pull much higher amperage coming out of corners than an oval car. This concentrates heat on the comm itself. That is the weak link. If you smell the motor after a run and smell burning Bakelite plastic then you are geared a little high. The shorting of motor 2% of time increases comm temperatures. The motor will also have less cooling than an oval car due to lower motor speeds.

Small comm mod motors can generally be geared to dump the pack on our track without feeling sluggish. They are more efficient and don't have the shorting to deal with. They run about 180 F at a 35 amp average on our track.

I'm not sure what you mean by 'shorting' of the motor. I don't beleive I've ever heard that term...

Well the other big factor is the time... Oval is typicaly 4 mintues, TC 5 minutes...

Even so, I was thinking some of my local TC fast guys were telling me they average up torward 25 amps... in 6 cell stock racing.

Touring 6-cell Stock -- Racing this summer on a concrete parking lot, large track with about a 285' racing line, TC3 with Optional AE motor clamp for more cooling AND small clip on heat sink as well(clip on heat sink stored in ice in cooler until right before race to maximize cooling, well tuned P2K's with a rollout around 1.15-1.24"... Motor temps ranged from 185-230 degrees F. (weather and air temp played a part here). Amp draw averaged around 25 amps, but this was REALLY pushing it (you could actually blister fingers on the motor after a 5 minute race). This is clearly as hard as you can push a motor and not kill it -- at this load, the comm would begin to discolor slightly, developing an orange color to it. Car was fast, made every A-main I attended all summer, and won my fair share, so this is about the limit I was willing to push the motor...

"Shorting" the motor -- Modern stock motors with laydown brushes have a "situation" that actually shorts out the comm. Fully seated brushes have too much overlap, and every comm segment will physically touch BOTH brushes (thus it creates a "short") twice per revolution (once at the "top", once at the "bottom"). So 6 times per revolution, for a brief moment, the comm is shorted and carrying high amp loads (HEAT)... My "solution" is to shave just under 1/32" from the trailing edge of each brush. This is a minimal change to the brush surface, and eliminates the short. I seem to gain torque and lose a marginal amount of RPM, but the motor is more efficient and runs cooler... (Trinity's P94 ads used to have good images of the laydown brush shorting situation...)

http://www.teamtrinity.com/motors/images/brush/brush3.gif

Note the yellow segment is touching both brushes -- the copper segment creates a dead short from one brush to the other....

Cool... thanks for the Info Tfram... I had never heard of this shorting issue... Learn something new every day... Somedays I learn more then one thing... :) Looks like the idea of triming the trailing edge could be just the ticket...

Another interesting tidbit about M7 and M8... at 21.6 amp load both motors put out exactly the same power (and by deffinition effciency). M7 produces greater power at higher loads then this, and M8 puts out more power at loads lower then this.

25 amps for 5 minutes would be very simmilar to 31 amps for 4 minutes... between 20 and 25 seems likely the range for TC and 25 and 30 for Oval... this is based largely on what others have told me, and somewhat on what I've seen with my own oval racing. This is for stock racing, with other motors like 19 Turn Spec or other mod motors they will work at higher amp loads because of their effciency curves.

Oval racers can get away with larger rollout as well because they don't slow down as much and punch at very low speed is not much of a factor.

Then if you go to 4 cell... it's a whole new game... 4 cell stock motors peak at a much lower point... more like 26 to 30 amps for peak power.
(Based on Robitronic data) Since the overall power is lower they can likely operate at higher at peak power though out a race without much trouble.

Just random thoughts about all this... :)

To directly look at the heat a motor will produce, all we have to do is look at the unused power.

Example:
M7 is 60% Efficient at 36.5 Amps, it is putting out 133 Watts while taking in 221 Watts, which leads to a 221-133 = 88 Watts of Heat.

M8 is 60% Efficient at 34.7 Amps, it is putting out 128 Watts while taking in 210 Watts, which leads to a 210-128 = 82 Watts of Heat.

The two samples I used above were the peak power of each motor. You can see that M7 will get hotter running at its peak than M8 will, even though they have the same Efficiency.



Also, you may find two motors that have the following characteristics:

M1 is 65% Efficient at 35 Amps, and putting out 137 Watts while taking in 210 Watts, which leads to a 210-137 = 73 Watts of Heat.

M2 is 63% Efficient at 33 Amps, and putting out 125 Watts while taking in 198 Watts, which leads to a 198-125 = 73 Watts of Heat.

These two motor, which I made up, would have a 2 Amp difference in battery consumption, but they would both run at the same temp.

I agree with your analysis of why some forms of stock racing can "get away" with pulling more amps than others...

With my TC3 for example, I run an LRP SR speed control (with the "chips" to control amp draw)... Even though the "average" was 25 amps, I did some testing and I can tell you for a FACT that I could feel the difference between a 50 A chip, a 65 A. chip, and running with NO chip (unlimited amp draw)... I normally ran with a 65 A. chip because it still allowed good punch with some reduction in motor temp.

But all this means that, at times, I WAS pulling that full 65 amps on the track! So the 25 amp average is misleading, because you have to be able to handle and dissipate the HEAT that 65 amp load generates! The average helps you tune the motor, but it only gets you in the ballpark...

On the other hand, a well setup oval chassis might have a motor that averages 30 amps (which would sound excessive if a 25 amp average nearly cooks a TC motor), but that motor may spend the whole race in the range of 25-35 amps, so it never has the monster heat and power demands of the TC at 65 amps...

My motors are about 20 degrees hotter on the top magnet than the bottom which is subjected to some airflow. I measure the bottom. Some things that happen when you run a stock motor too hot. The magnets get loose after a couple of weeks. The epoxy is weakened by the heat. I have a suspicion that this is why Trinity secures the magnet with springs and epoxy in the GM3's. Keeps the magnets in place. People seem to burn up this motor a lot from overgearing. The other thing is that the bakelite will burn off the inside of the comm segments. This creates a gap and increases the comm temperature. Both events result in a mysteriosly slow motor. You can get away with some overgearing when the motor is new, with a fresh large comm. After a couple of cuts then you probably have to change gearing a bit.