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Can a dyno find the good motors?


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#51 Butters37

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Posted 08 March 2016 - 01:28 AM

That is correct, Cap.
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#52 Brinkley47

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Posted 08 March 2016 - 02:37 AM

Are you looking for higher amp draw or lower amp draw on the power supply? To determine a "good" motor.
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#53 Samiam

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Posted 08 March 2016 - 03:13 AM

Off the subject... the motor issues would not be an issue if you design a class where the motor is so much better the the chassis... but then everyone would be flying off track.


It is called Eurosport. Expensive motors but you only buy two or three and you're done. But they can use the money they save on front wheels. :)
 
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#54 Noose

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Posted 08 March 2016 - 06:54 AM

I will say it once again. I saw 33 racers this past weekend. I was the 34th.  HP was not a problem out there. I saw (in tech and on the track) some of the sloppiest set-ups and of course these people had lots of issues out on the track.
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#55 tonyp

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Posted 08 March 2016 - 07:05 AM

Another thing that doesn't get mentioned is how much practice time you have on that RH along with the four or five races before they are worn out. Cheapest laps for the $$.
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#56 JerseyJohn

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Posted 08 March 2016 - 10:01 AM

the most effective way I've found (in the real world) was to break in a motor under a lite load. Most 1/1 motor shops put engines on test stands (dyno) and place a load against it while they set the rings and bearings.

I'm working on a propeller based test stand using a modified in-line motor bracket that sits atop the power supply and by using a prop as the load, it additionally cools the motor during testing and break-in.

just my $.03

 

With that in mind, Jeff, why can't you just mount the motor in a chassis with gear and tires and load it that way?


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#57 Butters37

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Posted 08 March 2016 - 10:18 AM

Would you put that on rollers, John? Like the old Tamiya break-in stand I believe? Have the rear tires actually run on painted wood rollers to simulate the track I mean.
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#58 MSwiss

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Posted 08 March 2016 - 10:31 AM

With that in mind, Jeff, why can't you just mount the motor in a chassis with gear and tires and load it that way?


That's not much of a load, with the tires not touching a sticky track and propelling the car.

Stu had a dyno with a big solid aluminum freewheel on it, maybe 9"-12" in diameter. All it did was confuse him.

What looked like it would run good on the track, didn't, and what didn't, did.

The only true dyno is the track. You'll never be sure you have a stud or a dud, unless you try it.
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#59 Steve Deiters

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Posted 08 March 2016 - 11:10 AM

I've wondered over the years if we used watts instead of amps to determine when a motor is being broken-in if that would be a better measure of it.
 
1) Being "broken in" meaning the brushes are now "seated".
 
2) Being at its maximum potential and is defined by an empirical number of some sort.
 
Thoughts?

#60 Butters37

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Posted 08 March 2016 - 11:35 AM

I've been recording ohms lately. The theory is that the meter will read the tab going in... through the brush... into the comm... through the windings... back out the comm... through the other brush to the tab.

A lower value should depict less flaws in the motor assembly thus giving a more efficient motor. All my values have been recorded.... I'm breaking them in now. Going through them at the track

I have a Fluke meter, not a cheap five-dollar Harbor Frieght unit. The values I've seen are 1.5 ohms (my best currently)... to 55 ohms.
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#61 Cheater

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Posted 08 March 2016 - 11:41 AM

Stu had a dyno with a big solid aluminum freewheel on it, maybe 9"-12" in diameter. All it did was confuse him.


Some years ago I had a brass flywheel made to fit on the motor shaft, sized (via guessimate) to simulate the load a motor sees pushing a car down the track. Got a photo tach with RS-232 output to graphing software. The idea was to see graphically how quickly the motor would spin up the flywheel, i.e. generate an RPM vs time curve. Give it 12v and see how steep the RPM curve that was generated, thinking the motor with the quickest RPM rise under the same voltage and load would be the "best" motor.

I never completed the project, because I came to realize that each track's unique power and wiring could not be simulated.

As I've mentioned before, I've experienced situations numerous times where a motor that was the worst I tested at one track was a world-beater at another track.

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#62 Phil Hackett

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Posted 08 March 2016 - 11:56 AM

Testing is an area where you need to correlate the data with actual performance. Just because a dyno says a particular motor is better than another doesn't mean it is. You must create baselines and this is where the real work is. "Better" needs to be defined by parameters set out by the tester. Not all people (racers) define better the same way. Therefore "numbers" are relative only to the requirements of the user giving them.


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#63 Phil Hackett

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Posted 08 March 2016 - 11:59 AM

Off the subject... the motor issues would not be an issue if you design a class where the motor is so much better the the chassis... but then everyone would be flying off track.   :laugh2:

 

Not the better drivers… they wouldn't be flying anywhere.


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#64 John Streisguth

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Posted 08 March 2016 - 12:32 PM

Which is why there has to be a rule to limit how long any one racer can hog a lane. I just want to get a few minutes on an inside lane and the gutters.
 
But it's impossible when guys are testing five cars at a time.


I may have five cars, but I know within five minutes what's what with each. Then it's back to the pits to work on a few things.
"Whatever..."

#65 Arne Saknussem

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Posted 08 March 2016 - 01:11 PM

Greg hit the nail on the old crumpet. Drag your dyno to the track and use the track's power supply or (IMO) you're wasting your time.

 

Logical thought (and my own experience) yields the following which should be fairly obvious to all concerned (disclaimer: I haven't won a race in a dog's age).

 

RH draw @ 4V <1.0A = may or may not be fast but will run cool.

RH draw @ 4V 1.0A to 1.4A = MOMNBF, runs about average temp.

RH draw @ 4V >1.4A = MOMNBF, will lay over late in the race in direct proportion to the heat generated.

 

Your numbers may vary.


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#66 James Grandi

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Posted 08 March 2016 - 01:17 PM

Most of the guys trying multiple cars at once seem to be running the middle lanes (usually), in particular orange courtesy of that being the qualifying lane.

It certainly is a good idea that instead of waiting for one of the center lanes, tune the car to maximize the gutters if you can. I followed Matt Bruce when I was in Purple and he in black during Can-Am, I was pushing hard to run the same pace as him. And we weren't slow, we were clocking mid-5.4 second laps. You have to be kind and give yourself a car that works generally well in as many lanes as you can - but if I had to pick, a race is won or lost in the upper and lower gutters.

As to sorting motors - it's pretty clear at this point that the power supply, or a dyno, isn't going to be the tool to make the call although it is useful to a degree. Track testing and a notebook is about all there is. For those who unfortunately lack a local track or a track within reasonable distance, of which I know there are quite a few with that problem, the only real solution would be planning for the travel and cost of going to the next event a day early and practicing/testing then.


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#67 Marty N

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Posted 08 March 2016 - 01:19 PM

Can a dynamometer find the good numbers?
 
That’s the question is it not? What’s it do? It measures and reports motor performance against a known load. If well designed that load will exceed the maximum capability the motor has to offer. It reports watts produced against watts drawn and gives and electrical efficiency number. It measures torque and reports. Amps and reports. It reports the rate of acceleration in tenths of a second. It plots all this on a nifty little scatter graph that allows comparisons on the same chart to several motors. In a nut shell 100 watts is ‘better’ than 80 watts and 60,000 rpm in 5 seconds is ‘better’ than 60, 000 rpm in 7 seconds. It draws amp traces that allow you to look at both raw and smoothed data that shows you how stable the current draw is  up to the test voltage (RPM). Better is just better.
 
Motor A outperforms motor B on the dyno at X inertia load. Which by the way has a wheel with several times more inertia load than your car. Bur even if the cars load is twice that of the dyno load motor A will still outperform motor B in terms a dyno measures. What a dyno can’t do is measure your skills as a driver, as a chassis tuner, what the track conditions are or your chosen setups efficiency in delivering that improvement in real world results of quicker lap times. So yes, a dyno is more than capable of sorting a good motor from a bad one. It just can’t tell you how good you will be with the results it reports. That’s not it’s fault. It isn’t it’s job.
 
Blaming a dyno for ones inability to understand or use it effectively is like blaming a hammer for a bad meal. IMHO.
 
My 2 cents worth and a dime in change.


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#68 Cheater

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Posted 08 March 2016 - 01:52 PM

Most of the guys trying multiple cars at once seem to be running the middle lanes (usually), in particular orange courtesy of that being the qualifying lane...


If I was short on time, I always just tuned on the gutters. If I could run them, the middle of the track should be OK.

And as an even further aside, if it was possible, I always found it very instructive to do at least one session across the track, red to black or vice versa, say 5-15 mins on each lane. It teaches you a lot about a track.
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#69 Phil Hackett

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Posted 08 March 2016 - 02:29 PM

Nothing beats trigger time. Even $800 of special tools for working on motors... :D

 

Who ever "owns" black at BPR will always be up front because if you're not fast in the middle it won't matter.


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#70 Noose

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Posted 08 March 2016 - 03:22 PM

I run the gutters. If the car is fast there it is going to be great in the middle. Races are won and lost in the gutters. I have set many fast race lap times on the red lane. Usually that is the one that is the trickiest in the deadman on all tracks. 

So yeah, as John Streisguth said, with a couple of minutes with multiple cars I know exactly what works and what doesn't. 
 
BTW, I have never had a Hawk Retro motor read anything above .9 amps 6 volts and that as one that had many races on it. The norm for these is typically .48-.52 amps after a light break in.
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#71 tonyp

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Posted 08 March 2016 - 04:05 PM

Ditto.

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#72 Tim Neja

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Posted 08 March 2016 - 05:16 PM

I have read all the post on this and it looks like a lot of time is being taken trying to find a good motor but nobody wants to build a motor because it takes up to much time and money to buy motor building equipment.  

 

But yet you will spend $80 on a break-In motor stand and God only knows how much money is spent on these motors.

Just saying!!!

Why is it in slot racing--some find the need to slam something that has proven to work?  The Retro Can Am class IS one of the best racing class's slot racing has seen in 40 years!  But all you're doing is bitching about it?  WHY?? It's been a great revival for slot racing, yet you find the need to force a change?  In another thread clearly %95 of the racers posted they love NOT having to build motors. But that didn't satisfy you, so now you're bagging on that idea here as well? WHY?  Retro racing is successful because we don't build motors. It's become a proven fact.  Why not enjoy  that and attempt to continue to GROW the class?  As was pointed out--there ARE motor building class's even in retro. Why is that not good for the motor builders?   Just enjoy the racing we have -- if it's slot racing--it's all good! :)


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#73 CoastalAngler1

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Posted 08 March 2016 - 05:56 PM

I'm the new guy.  I can get in the A Main with these RH motors.  Why?

I learned to test car(s) at the track and tune them at the track with multiple motors.  This is not easy, others are much faster in the pits.  

I've been trained 5 motors for each class for each big race.  Locally you should be able to find enough HP with what is leftover.

3 chassis per class means one race car, one backup car, one practice car. The 3 bodies hopefully interchange and you test those too.  

Take testing notes, change one thing at a time, you can always go back.  

Drive better to get first place.

I can find a bullet right now in my 30 motors from 2015, the new batch of 10 are pretty darn good too.

There is not a big difference in these motors - mine happen to like swimming lessons before they learn to crawl.  :ph34r:

All races are big to me.  I do not save 'bullets' for out of town.  

RH motors do not like excessive heat.

I never, never spin them above 6v unless in a car.

I still want a Trinity Dyno  :shout:


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#74 JerseyJohn

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Posted 08 March 2016 - 06:37 PM

You mean thrashing like maniacs and ending up being one of the first five cars to go out for qualifying? That's me, every race LOL.

 

Another  issue is when A Mainer guys go up there with five cars. Practice and checking cars is out the door for a lot of us... Just saying...


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#75 James Grandi

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Posted 08 March 2016 - 06:42 PM

I don't bring up 5 cars to practice. I bring 2 cars per class, and I tend to only test those 2 cars at a time. At one point I did test a 3rd car for another racer, but even then I try to make sure I only run a minute or two per car at most.

I know there are some guys that do run 4-5 cars at once, and I've certainly experienced waiting in the rotation for longer than I think it should take sometimes, but I have no more or less opportunity at track time than any other racer
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