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Building a dyno question


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#1 Brian Ambrose

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Posted 31 May 2017 - 02:52 PM

Would a four-blade fan blade that s about 2 inches tall, be enough drag on the motor to be useful if I was using a photo tach on the fan blade?

I'm looking to build some sort of a dyno, so I don't have to have the motor in a chassis.




#2 gotboostedvr6

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Posted 31 May 2017 - 02:58 PM

4" x 2.5" is the best prop to start with

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#3 swodem

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Posted 31 May 2017 - 05:56 PM

Personally I wouldn't use a prop screw. It loads up the bearings/bushings with a high level of thrust not designed for.

I would use a weight.

#4 Brian Ambrose

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Posted 31 May 2017 - 07:06 PM

That makes since, however wouldn't an angled gear do the same thing... making thrust?

#5 gotboostedvr6

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Posted 31 May 2017 - 07:46 PM

Never gave me trouble. Gotta oil liberally.

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#6 swodem

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Posted 30 July 2017 - 08:25 PM

That makes since, however wouldn't an angled gear do the same thing... making thrust?


No, it just improves mesh.

#7 Bazzie

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Posted 02 August 2017 - 07:06 PM

Drive a larger prop/fan through gears, that way you can avoid the thrust and change motor loading as required.

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#8 CoastalAngler1

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Posted 02 August 2017 - 07:11 PM

Does someone have a slot car motor dyno that can post a picture? Video?

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#9 bbr

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Posted 02 August 2017 - 08:03 PM

i think a dyno is good info if the motor tested was a precision-made motor.

With Retro motors, the on-track heat cycling determines the quality of a motor. Until it is run on track you don't know what you have.
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#10 crazyphysicsteacher

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Posted 03 August 2017 - 07:37 AM

Try the Simple Dyno website. 

The site has a program that can be used to build a dyno from.  ry using a 2 mm shaft gear to mount the small magnet the program requires. 

Any dyno really lets you make comparisons on it. So your system will work for you but will be really hard to compare to other results. I say keep going, there is merit to having a way to compare motors. 
I suggest using a system that lets you screw in the motor like you do in a chassis. 

Then use a belt drive system, like Pro Track or Parma make for rentals, to load a second wheel that spins to read the data. It will be more complex but will allow you to load the motor bushings how they will be used.

The important part of this is to be able to program in a voltage increase and rate of increase to measure voltage versus RPM change to compare how each test motor accelerates.
 
Let us know how it turns out.
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#11 Brian Ambrose

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Posted 03 August 2017 - 07:56 AM

Not looking to build a dyno any longer.

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#12 MSwiss

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Posted 03 August 2017 - 08:29 AM

Have you had success with it?

IOW, has it identified the motor that is fastest on the track?

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#13 Brian Ambrose

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Posted 03 August 2017 - 08:51 AM

I last night was the first time I've used it. Also going to be getting/building a chassis dyno.

#14 tonyp

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Posted 03 August 2017 - 09:04 AM

I've never had a 'bad on the dyno' motor run good on the track. Same with my chassis dyno, if it's good, it's good on the track. Saves a lot of thrashing on race morning.
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#15 Noose

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Posted 03 August 2017 - 09:33 AM

Once you have readings from the Trinity dyno and if you have a rolling dyno, you can correlate the readings to performance on the various tracks for sure. With the five tracks we have here in our series, I know the hi amp ones run better at certain tracks than do the low amp ones.
 
The rolling dyno results have proven very reliable for a given motor in a given car.

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#16 Shooter7mustang

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Posted 03 August 2017 - 10:51 AM

Is the Trinity still available ?


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#17 tonyp

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Posted 03 August 2017 - 04:07 PM

No, haven't been for years, but we sold a ton for brushed RC motors. Since RC went brushless they are no longer usable, so there has to be a couple of thousand out there.


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#18 bbr

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Posted 03 August 2017 - 07:35 PM

http://www.ebay.com/...F6KRmb-o5DQmMjQ

 

I made this work with slot car motors


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#19 bbr

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Posted 03 August 2017 - 08:55 PM

made an adapter to position the slot motor, will post a picture when I get home tonight.

 
what I really want is a fantom like dyno.
this company make this, I think it can be modified to work with slot motors
01-01-0001-MD1-00.232_grande.png
 _20170804_002244.JPG
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#20 dalek

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Posted 06 August 2017 - 01:57 PM

Even though Brian went a different route, I'm posting what I built.  The rig lets me compare motors to each other.

 

It's still a work in progress, but it looks like I'll eventually test each motor with two props.  A prop that causes about a 3.5 amp draw at 6 volts and a smaller prop that causes about a 3.5 amp draw at 12 volts.

 

1110 copy.jpg

 

1111 copy.jpg

 

1118 copy.jpg

 

1122 copy.jpg

 

1125 copy.jpg

 

1128 copy.jpg

 


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#21 Brian Ambrose

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Posted 06 August 2017 - 02:59 PM

Very interesting Dale.

#22 gotboostedvr6

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Posted 06 August 2017 - 05:51 PM

Are you using eagle tree?

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#23 dalek

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Posted 07 August 2017 - 07:14 AM

Are you using eagle tree?

 

I didn't know what eagle tree was so I searched for it.
 
 
I assume you are wondering if I use one of their sensors, such as airspeed or what not.
 
What you see in the pictures is all that I use.  
 
The tachometer tells me when one motor is more powerful than another.

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#24 gotboostedvr6

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Posted 07 August 2017 - 07:32 AM

Does the tachometer use a optical sensor?

Those who work for a living are being quickly overwhelmed by those who vote for a living.

Thomas Jefferson: "Paper is poverty. It is only the ghost of money, and not money itself."
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#25 gotboostedvr6

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Posted 07 August 2017 - 07:34 AM

Edit. I see the sensor in the pic :)

Those who work for a living are being quickly overwhelmed by those who vote for a living.

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#26 Brian Ambrose

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Posted 07 August 2017 - 07:45 AM

Dale, have you had a great reading on a motor and it be a turd on the track?

#27 dalek

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Posted 07 August 2017 - 08:01 AM

Dale, have you had a great reading on a motor and it be a turd on the track?

 

The amount of testing I've done so far is minimal so I don't have enough experience with it to know how useful the device will be.
 
However, I did compare four PS 4002 FK motors to each other and the one that spun the prop the fastest turned out to be a strong motor on the track.
 
When I have time to do more testing, I'll try to remember to post some of my findings here -- both RPM and amps.

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#28 Ralph Thorne

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Posted 07 August 2017 - 11:13 AM

Dale, have you had a great reading on a motor and it be a turd on the track?

 

Happens to me all the time, and I've also had what I thought were duds turn out to be rockets. IMO dyno and RPM readings are useless, all you doing is determining what motors run best on your power supply at low votlage. If we raced power supplies it might be worth all the effort lol. You just have to try every motor on every track. Actual track power is way different then a power supply or "dyno" at 5 or 6 volts.


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#29 dalek

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Posted 08 August 2017 - 07:41 AM

 

Happens to me all the time, and I've also had what I thought were duds turn out to be rockets. IMO dyno and RPM readings are useless, all you doing is determining what motors run best on your power supply at low votlage. If we raced power supplies it might be worth all the effort lol. You just have to try every motor on every track. Actual track power is way different then a power supply or "dyno" at 5 or 6 volts.

 

I've seen similar comments in the past in other threads regarding dynos, so I knew in advance that my device would likely have limited usefulness.


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#30 tonyp

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Posted 08 August 2017 - 07:43 AM

I believe dynos can weed out bad motors if you have accrued enough data on the motors and track performance.


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#31 Eddie Fleming

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Posted 08 August 2017 - 08:06 AM

I think the dyno could work fine. the key and weak point is the data acquisition.

 

How quick will the motor accelerate a load?

 

What is the top end under load?

 

how quick will it decelerate a load under breaking?


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#32 Phil Hackett

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Posted 08 August 2017 - 09:35 AM

I think the dyno could work fine. the key and weak point is the data acquisition.

 

How quick will the motor accelerate a load?

 

What is the top end under load?

 

how quick will it decelerate a load under breaking?

 

Here are some more:

 

How hot will it get get under load?

 

How long will it need to run under load for a stable "run"?

 

How many amps will it pull through the range of load?

 

At what point will the harmonics of the balance affect the amp draw/rpms?

 

How close is the load you're providing to the real application of pushing a slot car around a track?

 

Data is the key and you should have a system of recording it and analysing it....


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#33 Ralph Thorne

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Posted 08 August 2017 - 11:44 AM

If simply putting a motor "under a load" on the power supply or dyno was the answer, explain the following that happened to me a few weeks ago...

 

Good dyno motor motor reads 33,200 rpms at 6 volts. It runs a 3.65 geared 13/35 and a 4.24 geared 10/35 with 13.5 volts track power.

 

Bad dyno motor reads 27,800 rpm at 6 volts. It runs 3.85 geared 13/35 and a 4.01 geared 10/35 with 13.5 volts track power.

 

Now if I was going by dyno readings I should have left the second motor at home. Glad I didn't because it was my best motor with a 10/35 gear on it. Just putting a load on a motor doesnt factor in the important things such as, weight of the car, track power, gear ratio, final drive ratio or the correct power band the motor will be in once you selected your pinion and spur gear. Some motors also run good with 1 car on the track and slow down with 8 cars and vice versa, again no way to replicate that IMO.  Anyone with brand new "bad dyno motors" send me a PM and I'll take them off your hands!



#34 SpeedyNH

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Posted 08 August 2017 - 12:51 PM

sounds as if one needs a dynamic acceleration load across Voltage. that would be a Lot of data!

but I'd love to be able to do it.

speedy


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#35 bbr

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Posted 08 August 2017 - 01:06 PM

Need a kid to track test your motors while you hangout with the gf.
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#36 Eddie Fleming

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Posted 08 August 2017 - 02:47 PM

Running a motor on 6V on a dyno is kind of like running a fuel engine at half throttle and expecting full usable readings from the dyno.

 

If you can't run it at full voltage it is not under enough load. or the wrong kind of load.

 

sampling and plotting enough data points is still the key to useful results.

 

Much easier to put it in the car and see how it runs.

 

IMHO


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#37 Danny Zona

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Posted 08 August 2017 - 02:48 PM

I have notes on Ralph with my dyno vision.

Ralph is about a half a tenth slower when the girlfriend is present.

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#38 Brian Ambrose

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Posted 08 August 2017 - 03:22 PM

Then he needs to bring more than 1 girlfriend to Florida in Nov.
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