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Hawk 7 oddity!


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#1 tazman

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Posted 12 November 2017 - 10:30 PM

I tried to run my recently broken in Hawk 7 and I was upset to say the least. Broken in at 4 volts for 15 mins. and sounded real good. Clean up and installed the gears and tires - tried it out today and it was a dog!

 

After close examination I noticed that the comm was wrapped with twine like an HO hot stock arm. The spot that was tied was pointed up towards the can hole.

 

What is the purpose for this? I noticed that the worn motors I had did not have this.

 

Has anybody had the same problem? Insights?

 

abb5ad790782793fb137ec1a610e1898.jpg


Rick Ortogero




#2 Ramcatlarry

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Posted 13 November 2017 - 12:13 AM

Try an 11t 64p pinion. 

 

The tie is to keep the wires from being thrown off... as most modern motors need to be when they exceed 40K RPM.


Larry D. Kelley, MA
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#3 Racer36

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Posted 13 November 2017 - 08:15 AM

Is that a 6 tooth pinion on a Hawk 7? Are you racing around the inside of a teacup?


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#4 JK Products

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Posted 13 November 2017 - 08:15 AM

Hi Rick,

 

Larry is correct, that is what is called a "tied comm" - a wrapping around the wires on the commutator so they can better handle the high RPM and not "throw a wire." They are standard on most modern motors. 

 

Secondly, I think you might have the motor very poorly geared and this could very well account for what you are calling "dog" performance. That looks like about a 7 tooth pinion which would not be appropriate for these type of motors. As Larry again correctly indicated, an 11 tooth pinion is much more common, maybe along with a 37 tooth gear or thereabouts. Please ask at your local track what people usually run. 

 

Tim


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#5 havlicek

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Posted 13 November 2017 - 08:19 AM

  When I first saw this, I thought I just wasn't getting what the problem is... like it was just me.   :)


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#6 gotboostedvr6

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Posted 13 November 2017 - 08:35 AM

I used to gear Hawk 7 motors the following:

12:38 / .710" tire
11:36 / .710"
11:35 / .700"
14:43 / .710"
13:40 / .700"
13:44 / .760"
13:42 / .740"

If by chance you actually have a Retro Hawk 7 drop 1 or 2 teeth on the spur.


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#7 havlicek

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Posted 13 November 2017 - 08:49 AM

Larry is correct, that is what is called a "tied comm" - a wrapping around the wires on the commutator so they can better handle the high rpm's and not "throw a wire". They are standard on most modern motors.

 

In other words, that "twine" is a good thing, rather than a bad thing!


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#8 dalek

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Posted 13 November 2017 - 09:09 AM

Recently, I bought three Hawk 7s. Two of them behaved as follows:  
 
On my power supply, I started at 2 volts, and increased the voltage.  
 
From about 8 volts to about 9 or 10 volts, the motor RPM didn't increase much, but the amps draw did (up to about 1.3 amps).  
 
As I continued to increase the voltage, suddenly the RPM would jump up and the amps drop off.
 
At 12 volts, the normal current draw for a Hawk 7 seems to be about .75 amps.
 
******************
However, the third motor wouldn't make that leap to the higher RPM. This was the case, both before and after the brushes were fully seated.  
 
By the time I had increased the voltage to 12 volts, the motor was pulling about 1.7 amps and quickly getting hot (holding it between my fingers) but the RPM was only about what a good Hawk 7 would be turning at about 9 volts.
 
As it turned out, that third motor was a dog when installed in a car.
 
******************
 
If you test your bad motor as described above, I'd be interested to know what the results were.

Dale King
 
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#9 MSwiss

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Posted 13 November 2017 - 09:40 AM

Dale King,

 

You shouldn't be running your motors without a load at 12v.


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Mike Swiss
 
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#10 tonyp

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Posted 13 November 2017 - 09:44 AM

Absolutely.
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#11 dalek

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Posted 13 November 2017 - 09:59 AM

The motors are 12 volt rated and I've never seen any info from a manufacturer that says they will be damaged if run at 12 volts with no load.
 
One of those two "good" motors (that I mentioned above) was in my JK Indy car this past Saturday at the Florida Slot Car Series races.  
 
If I hadn't missed 2-1/2 heats reparing a broken guide wire, I would have finished second or first (based on my lap times in the heats that I ran).
 
Apparently, that motor didn't mind having been run at 12 volts with no load.
Dale King
 
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#12 gotboostedvr6

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Posted 13 November 2017 - 10:08 AM

IMO 4 or 5 volts max free spinning no load.

You burn the trailing edge of both the brushes and the comm segments with a low load/high RPM situation.

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#13 DOCinCocoa

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Posted 13 November 2017 - 10:18 AM

FWIW: I never run my slot car motors above 6v without a load. With Group 12 and Hawk 6 motors with the "big dog arm," I never went about 5v. If you ever reach 40,000 RPM, it is time to shut it down.


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#14 havlicek

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Posted 13 November 2017 - 10:20 AM

The motors are 12 volt rated and I've never seen any info from a manufacturer that says they will be damaged if run at 12 volts with no load.
 
One of those two "good" motors (that I mentioned above) was in my JK Indy car this past Saturday at the Florida Slot Car Series races.  
 
If I hadn't missed 2 1/2 heats reparing a broken guide wire, I would have finished 2nd or 1st (based on my lap times in the heats that I ran).
 
Apparently, that motor didn't mind having been run at 12 volts with no load.


Here's the thing here (and yes, running a motor at more than low volts with no load = no bueno).  

If a motor is rated at 12VDC, that doesn't mean it is rated to run at that voltage with no load. Why?, well for one thing, a motor running at 12VDC will be spinning faster than it would installed in a car. Motor ratings are something of an average guess. Manufacturers look at an average life-span of a motor running at an "average" voltage and then come up with their definition of what is an acceptable life span.  In use, these motors don't run full punch all the time. If they did, they'd fail much faster. 

On whatever else is going on here, all motors are never equal. Inexpensive motors do amazingly well all things considered, but there will always be standouts and others that seem to fall further back in the pack.  It does seem though that some of this is due to the end-user (I'm not saying this is the case here)... bad gear choices, poor set-up, harmful "break-in" procedures all come into play as well as just the "chance" involved in mass-production.


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#15 Racer36

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Posted 13 November 2017 - 11:12 AM

Any device designed to do work (motor or engine) should never be run without load. Try running your gas engine at redline RPM without load. Stand back a touch so none of the flying innards hit you.


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#16 Gator Bob

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Posted 13 November 2017 - 11:19 AM

IMO 4 or 5 volts max free spinning no load.

You burn the trailing edge of both the brushes and the comm segments with a low load/high RPM situation.

 

If the brushes are installed 90 deg. off of what used to be 'normal', how do you even tell?

 

"Will the real trailing edge please stand up"


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                            Bob Israelite

#17 MSwiss

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Posted 13 November 2017 - 11:20 AM

John explained it well, but I'll add a few things.

I don't see any spec sheets included with these motors, let alone any that state what they are "12v rated".

Any references to voltage, either state the break-in voltage, which would be no load, and IIRC, it never exceeds 5 or 6v.

Any other references to voltage also refer to a gear ratio.

IOW, these motors are marketed as slot racing motors, not free-spinning noisemakers.

Just because your 12v free spinning didn't damage that particular motor, that doesn't mean it's a good idea.

There is zero point to it, because any amp readings you get are pointless pieces of data, because in real racing, the motors never run at no load, at 12v, of course, unless you spin a pinion, or a crown gear.

Mike Swiss
 
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#18 Gator Bob

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Posted 13 November 2017 - 11:29 AM

Most Mabuchi FK motors are 'rated' at 3 - 6 volts.

That's why they run so good but don't last at 12-14v.
 
They sell 6 volt motors rated at 20 something thousand RPM. If you run it up to 12+ volts and you have a 40 something thousand RPM motor.
 
"Breaking them in" might find more 'speed' but it definitely will reduce lifespan.
 
Seems straightforward to me.
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                            Bob Israelite

#19 Fast Freddie

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Posted 13 November 2017 - 11:40 AM

Just a small point of interest. 

I'd like to know just how much heat it took to attach those wires to the motor. You are aware that excessive heat can weaken the springs in those motors and that could very well be why it ran like a dog.
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#20 tazman

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Posted 13 November 2017 - 08:11 PM

I appreciate all the insights you guys shared and I forgot to mention two things.

 

One, the gears are 72 pitch 9/43 and second the tires are .700" JK tires. This is the original set-p for this car as I was doing a replacement - it was plenty quick before the original motor ran out of motor brushes. I cut the excessive twine sticking upwards on the comm in the new motor and it sounded better but, it still ran like a dog! I am convinced that this motor was a dog to begin with and nothing would change that!

 

On to a new motor!


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#21 dalek

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Posted 13 November 2017 - 08:13 PM

I don't see any spec sheets included with these motors, let alone any that state what they are "12v rated".

 

I assume that the motors are rated at 12 volts because on the JK Products web pages, it used to state that the Hawk 7 was a 48,000 RPM motor.

 

From measurements I've made in the past, using my motor test stand with optical tach, I was seeing motor speeds in that range while testing with the smallest prop I have.


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#22 MSwiss

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Posted 13 November 2017 - 09:13 PM

You went from "The motors are 12 volt rated" to "I assume that the motors are rated at 12 volts."
 
Where does 48,000 RPM imply it's "rated" at 12v?
 
If a slot car motor would be "rated," it just stands to reason to reason it would be for the application the motor is attended to be used, which in this case is with a load on it.
 
Here are the back of the cards of the two different JK motors I have in stock. (I sold the last of my Hawk 7s on Friday.)
 
It's pretty clear that the 12-12.5v and 12-12.8v refers to the track voltage while racing.
 
And also, it only OK, free revving, up to 5v during break-in.
 
There isn't any implication that it's OK to free-rev to 12v, for who knows what non-real slot car world reason.
 
These motors might withstand 12v free-revving, partly because they are fairly mild winds and are amazingly well-made for a cheap motor, but as discussed, it's pointless to do it.
 
And free-revving a powerful wing car, or Eurosport motor, to 12v, is a safety hazard, with a chance of a lamination, or laminations, flying out of the motor, at the point of a big balance hole.
 

20171113_195755-1.jpg


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Mike Swiss
 
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#23 Ramcatlarry

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Posted 14 November 2017 - 12:21 AM

8-9/43 is gearing we used for built Grp 12 C-cans good for 100K RPM for the ISRA Worlds production cars. Still need a bigger pinion.


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#24 Kevin Donovan

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Posted 14 November 2017 - 06:09 AM

FWIW, the last two Hawk 7 Motors I bought were “dogs,” too. I’m really tired of these things.



#25 havlicek

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Posted 14 November 2017 - 07:57 AM

This all brings to mind something I've wondered about. 

 

Since these motors use a "folded and welded" type com connection (as opposed to a flat tab), is the tying even necessary at all with such a relatively mild wind? I mean, besides (I guess) maybe seeming more secure, there's also a "possible" downside. A simple knotted piece of "string" (and these aren't... can't be... a kind of tying that requires a lot of attention because of cost) around the wires could also cause an itty-bitty "imbalance" as well as some turbulence... I guess.

So I wonder if it's done just to make people feel better. Has anyone taken a bunch of these arms, removed the string from half and then run them all to destruction and tabulated the results? I wouldn't be surprised if the tied ones weren't any less prone to failure than the untied ones.


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#26 MSwiss

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Posted 14 November 2017 - 08:12 AM

"Has anyone taken a bunch of these arms, removed the string from half and then run them all to destruction and tabulated the results?"
No.

A racer wouldn't waste his time because there is no end game. I doubt a manufacture would also waste their time.

Spend a $1,000 in their own labor time, to maybe save $1,000, in the future, in manufacturing cost?

$1,000 they can always pass on to the consumer in the price of the product?


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Mike Swiss
 
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17B West Ogden AveWestmont, IL 60559, ( 708) 203-8003
mikeswiss86@hotmail.com (also my PayPal address) 
Note: Send all USPS packages and mail to: 5858 Chase Ave., Downers Grove, IL 60516
Make checks out to Chicagoland Woodworking, Inc.


#27 dalek

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Posted 14 November 2017 - 08:36 AM

What does "recommended shortest gear ratio" mean?

 

Would 3.00 be shorter than 3.27?

 

Tim Homola, would you please answer the questions, or at least verify the answers that anyone else gives, since the Hawk motors are your product.

 

Thank you.


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Dale King
 
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#28 havlicek

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Posted 14 November 2017 - 08:36 AM

A racer wouldn't waste his time because there is no end game. I doubt a manufacture would also waste their time.

Spend a $1,000 in their own labor time, to maybe save $1,000, in the future, in manufacturing cost?

$1,000 they can always pass on to the consumer, in the price of the product?

 
Yep! So I'm left to figure that it's being done (probably) as much for appearances as any real benefit.  :D
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#29 havlicek

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Posted 14 November 2017 - 08:43 AM

What does "recommended shortest gear ratio" mean?
 
Would 3.00 be shorter than 3.27?
 
Tim Homola, would you please answer the questions, or at least verify the answers that anyone else gives, since the Hawk motors are your product.

 
The terms "short" and "tall" can be confusing and people can both misuse and misunderstand them. For "me," a "tall" gear ratio is a numerically high one... so a 4:1 setup is "taller" than a 3:1 one, and the 3:1 ratio is "shorter" than the 4:1 ratio... but I could be wrong about that!

What I know for sure is that both too-tall (where the motor is continually winding-out) and too-short (where the motor is lugging/overworking) gears can be motor-killers.  People ask me what gears are best for a motor, and I tell them honestly that I have no idea. Best is to ask other racers.
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#30 MSwiss

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Posted 14 November 2017 - 08:59 AM

Yep!  So I'm left to figure that it's being done (probably) as much for appearances as any real benefit.  :D

 

Not true.

On my Wednesday night racing, where we race on 12.2v, and racers quote getting 20 (16 minute) races with one motor, the comm tie is probably not doing much.

At raceways, where they run on up to 14.3v, it's probably real useful.


Mike Swiss
 
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Make checks out to Chicagoland Woodworking, Inc.


#31 havlicek

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Posted 14 November 2017 - 10:28 AM

OK... so then it "might" be doing something. 

That doesn't make my thought not true... just maybe not completely true  :D
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#32 Cheater

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Posted 14 November 2017 - 11:24 AM

Tall vs. short gearing has always been a little bit confusing.
 
To me (and see below), a shorter gear ratio would be 5:1 vs. 4:1.
 
A taller gear ratio would be 3:1 vs. 4:1.
 
Long/Short gear: What does it mean?
 
The Lowdown on Gear Ratios
 
Rear-End Gearing Simplified
 
What is the difference between short and tall gearing in bikes and cars?

 

The consensus in the in the 1:1 vehicle world seems to be that "taller" means lower numerically and "shorter" means higher numerically.


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#33 MSwiss

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Posted 14 November 2017 - 11:33 AM

I agree it's confusing and never use the terms, short or tall.

"Mike, my motor is running hot. What should I do?"

"Go to a higher numeric gear ratio".

"Mike, my car is running cool, but slow. What should I do?"

"Go to a lower numeric gear ratio".
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#34 Gator Bob

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Posted 14 November 2017 - 11:35 AM

BITD If you have a Dana, 12 bolt or a 9" with 3:08s it's tall (or long)... think long as a top end gear that takes 'longer' to get up to speed or takes longer to get to the 'redline.'
 
5:13s it's short... short track, short time to get to 'the redline.'
 
It can be counterintuitive and easy to mix up.
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#35 Eddie Fleming

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Posted 14 November 2017 - 11:36 AM

So lower is taller and shorter is higher?

 

I am so confused. 


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#36 Cheater

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Posted 14 November 2017 - 11:47 AM

Eddie,

Lower "numerically" is taller and higher "numerically" is shorter... yes.

A 3:1 gear ratio is "taller" than a 5:1 gear ratio.
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#37 Eddie Fleming

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Posted 14 November 2017 - 12:09 PM

I know.


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#38 JK Products

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Posted 14 November 2017 - 01:53 PM

Hi Dale,

As others have stated, 3.0:1 is taller than 3.27:1 and not recommended. The typical recommended ratios for our motors are between 3.3-4.2:1.
 
The picture sure looks like about a 7-tooth pinion but let’s use the gearing you listed, 43/9 = 4.8:1 gear ratio. This is short. With one of our motors geared this short I would expect it to be slow down the straights as you are likely not getting enough top end speed for most tracks.
 
This is normally what you would see with gearing that is too tall or too short.
 
Too Tall (i.e. 30 tooth gear/12 tooth pinion = 2.5:1 gear ratio)
 
This will leave the motor with lower RPMs.
+ This normally leads to higher top end car speed if you have a long enough straight
- worse brakes as not as much motor EMF available
- less torque coming out of the turns
- motor runs hotter
 
(This can even lead to the car starting the straight slowly and then accelerating quickly as the RPMs finally pick up because they started too slow coming out of the turn.)
 
The car is often more difficult to drive but could be quick depending upon the track.
 
 
Too Short (i.e. 43 tooth gear/9 tooth pinion = 4.8:1 gear ratio)
 
This will leave the motor with higher RPMs.
- possible lower top end car speed if you have long straights
+ better brakes due to larger motor EMF available
+ more torque coming out of turns as the RPMs stay higher throughout the turn
+ motor runs cooler
 
The car is usually easier to drive but could be slow depending upon the track.
 
The other major factors that need to be considered in gear selection are weight of the car, track layout (slow speed [turny, flat road course] or high speed track [most Kings]), and tire diameter.
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#39 Fast Freddie

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Posted 15 November 2017 - 12:26 PM

First of all anyone who races these motors knows that the brushes are installed bas ackwards.  If they were installed correctly it wouldn't take much to seat them and the motors would run very good from the jump.  Secondly running the motors with unseated brushes makes most of them seem like dogs.  When you use the non-recommended way of breaking in the motors, either in water or with Simple Green all you are doing, if your careful, is fully seating the brushes in a shorter span of time and with less heat.  Yes, using that method of break in does shorten the life span of the motor but only because the recommended break in is incomplete. If you use the recommended break in the brushes are still on the tips and not seated so technically they last longer.  I have done the recommended break in and when the motor was installed and on the track it didn't run even close to the motors with fully seated brushes.  If your goal is just to run your car for fun and longevity then there is no need for fully seated brushes but if your racing in competition there is and you'll just have to live with the shorter motor life.  Besides why would any motor manufacture be against shorter motor life?  They'll sell more motors especially if the motors run better.

 

One more thing.  Maybe you should be more concerned about FDR (final drive ratio) then gear ratios.  Would you ever gear an HR motor 13x36?  That's a gear ratio of 2.76 to 1.  Much steeper then the recommended ratio.  What if you paired it with .720 tires.  The FDR in this case is 3.85.  The most popular FDR in Retro racing using this motor is 3.83 with .8125 tires and a 9x28 gear ratio.  This FDR is something to consider.  Oh and by the way I've run this gear ratio using this same FDR and had no overheating problems and it ran very good.   


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#40 tazman

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Posted 15 November 2017 - 03:03 PM

Hi Dale,

As others have stated, 3.0:1 is taller than 3.27:1 and not recommended. The typical recommended ratios for our motors are between 3.3-4.2:1.
 
The picture sure looks like about a 7-tooth pinion but let’s use the gearing you listed, 43/9 = 4.8:1 gear ratio. This is short. With one of our motors geared this short I would expect it to be slow down the straights as you are likely not getting enough top end speed for most tracks.
 
This is normally what you would see with gearing that is too tall or too short.
 
Too Tall (i.e. 30 tooth gear/12 tooth pinion = 2.5:1 gear ratio)
 
This will leave the motor with lower RPMs.
+ This normally leads to higher top end car speed if you have a long enough straight
- worse brakes as not as much motor EMF available
- less torque coming out of the turns
- motor runs hotter
 
(This can even lead to the car starting the straight slowly and then accelerating quickly as the RPMs finally pick up because they started too slow coming out of the turn.)
 
The car is often more difficult to drive but could be quick depending upon the track.
 
 
Too Short (i.e. 43 tooth gear/9 tooth pinion = 4.8:1 gear ratio)
 
This will leave the motor with higher RPMs.
- possible lower top end car speed if you have long straights
+ better brakes due to larger motor EMF available
+ more torque coming out of turns as the RPMs stay higher throughout the turn
+ motor runs cooler
 
The car is usually easier to drive but could be slow depending upon the track.
 
The other major factors that need to be considered in gear selection are weight of the car, track layout (slow speed [turny, flat road course] or high speed track [most Kings]), and tire diameter.

I like your descriptors of running 9/43 ratio with 72 pitch gears. What you described is exactly the performance our cars have especially running on a small flat track - no long straightaways or a huge bank. Keeping the rpms up is the key for our track and that motor I broke in earlier just did not respond. It did not help with the way the twine was tied and the excess twine was pointed towards the motor hole. Sniped the excess twine off, some improvement but NO DICE! I pulled the motor apart and the stacks kind of looked normal except there was no balance marks on the stacks! All of my other H7 had balance marks - mistake or was it a perfectly balanced arm?

Sent from my SAMSUNG-SM-N920A using Tapatalk
Rick Ortogero

#41 tazman

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Posted 15 November 2017 - 03:03 PM

Hi Dale,

As others have stated, 3.0:1 is taller than 3.27:1 and not recommended. The typical recommended ratios for our motors are between 3.3-4.2:1.
 
The picture sure looks like about a 7-tooth pinion but let’s use the gearing you listed, 43/9 = 4.8:1 gear ratio. This is short. With one of our motors geared this short I would expect it to be slow down the straights as you are likely not getting enough top end speed for most tracks.
 
This is normally what you would see with gearing that is too tall or too short.
 
Too Tall (i.e. 30 tooth gear/12 tooth pinion = 2.5:1 gear ratio)
 
This will leave the motor with lower RPMs.
+ This normally leads to higher top end car speed if you have a long enough straight
- worse brakes as not as much motor EMF available
- less torque coming out of the turns
- motor runs hotter
 
(This can even lead to the car starting the straight slowly and then accelerating quickly as the RPMs finally pick up because they started too slow coming out of the turn.)
 
The car is often more difficult to drive but could be quick depending upon the track.
 
 
Too Short (i.e. 43 tooth gear/9 tooth pinion = 4.8:1 gear ratio)
 
This will leave the motor with higher RPMs.
- possible lower top end car speed if you have long straights
+ better brakes due to larger motor EMF available
+ more torque coming out of turns as the RPMs stay higher throughout the turn
+ motor runs cooler
 
The car is usually easier to drive but could be slow depending upon the track.
 
The other major factors that need to be considered in gear selection are weight of the car, track layout (slow speed [turny, flat road course] or high speed track [most Kings]), and tire diameter.

I like your descriptors of running 9/43 ratio with 72 pitch gears. What you described is exactly the performance our cars have especially running on a small flat track - no long straightaways or a huge bank. Keeping the rpms up is the key for our track and that motor I broke in earlier just did not respond. It did not help with the way the twine was tied and the excess twine was pointed towards the motor hole. Sniped the excess twine off, some improvement but NO DICE! I pulled the motor apart and the stacks kind of looked normal except there was no balance marks on the stacks! All of my other H7 had balance marks - mistake or was it a perfectly balanced arm?

Sent from my SAMSUNG-SM-N920A using Tapatalk
Rick Ortogero

#42 tazman

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Posted 15 November 2017 - 03:03 PM

Hi Dale,

As others have stated, 3.0:1 is taller than 3.27:1 and not recommended. The typical recommended ratios for our motors are between 3.3-4.2:1.
 
The picture sure looks like about a 7-tooth pinion but let’s use the gearing you listed, 43/9 = 4.8:1 gear ratio. This is short. With one of our motors geared this short I would expect it to be slow down the straights as you are likely not getting enough top end speed for most tracks.
 
This is normally what you would see with gearing that is too tall or too short.
 
Too Tall (i.e. 30 tooth gear/12 tooth pinion = 2.5:1 gear ratio)
 
This will leave the motor with lower RPMs.
+ This normally leads to higher top end car speed if you have a long enough straight
- worse brakes as not as much motor EMF available
- less torque coming out of the turns
- motor runs hotter
 
(This can even lead to the car starting the straight slowly and then accelerating quickly as the RPMs finally pick up because they started too slow coming out of the turn.)
 
The car is often more difficult to drive but could be quick depending upon the track.
 
 
Too Short (i.e. 43 tooth gear/9 tooth pinion = 4.8:1 gear ratio)
 
This will leave the motor with higher RPMs.
- possible lower top end car speed if you have long straights
+ better brakes due to larger motor EMF available
+ more torque coming out of turns as the RPMs stay higher throughout the turn
+ motor runs cooler
 
The car is usually easier to drive but could be slow depending upon the track.
 
The other major factors that need to be considered in gear selection are weight of the car, track layout (slow speed [turny, flat road course] or high speed track [most Kings]), and tire diameter.

I like your descriptors of running 9/43 ratio with 72 pitch gears. What you described is exactly the performance our cars have especially running on a small flat track - no long straightaways or a huge bank. Keeping the rpms up is the key for our track and that motor I broke in earlier just did not respond. It did not help with the way the twine was tied and the excess twine was pointed towards the motor hole. Sniped the excess twine off, some improvement but NO DICE! I pulled the motor apart and the stacks kind of looked normal except there was no balance marks on the stacks! All of my other H7 had balance marks - mistake or was it a perfectly balanced arm?

Sent from my SAMSUNG-SM-N920A using Tapatalk
Rick Ortogero

#43 tazman

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Posted 15 November 2017 - 03:04 PM

Hi Dale,

As others have stated, 3.0:1 is taller than 3.27:1 and not recommended. The typical recommended ratios for our motors are between 3.3-4.2:1.
 
The picture sure looks like about a 7-tooth pinion but let’s use the gearing you listed, 43/9 = 4.8:1 gear ratio. This is short. With one of our motors geared this short I would expect it to be slow down the straights as you are likely not getting enough top end speed for most tracks.
 
This is normally what you would see with gearing that is too tall or too short.
 
Too Tall (i.e. 30 tooth gear/12 tooth pinion = 2.5:1 gear ratio)
 
This will leave the motor with lower RPMs.
+ This normally leads to higher top end car speed if you have a long enough straight
- worse brakes as not as much motor EMF available
- less torque coming out of the turns
- motor runs hotter
 
(This can even lead to the car starting the straight slowly and then accelerating quickly as the RPMs finally pick up because they started too slow coming out of the turn.)
 
The car is often more difficult to drive but could be quick depending upon the track.
 
 
Too Short (i.e. 43 tooth gear/9 tooth pinion = 4.8:1 gear ratio)
 
This will leave the motor with higher RPMs.
- possible lower top end car speed if you have long straights
+ better brakes due to larger motor EMF available
+ more torque coming out of turns as the RPMs stay higher throughout the turn
+ motor runs cooler
 
The car is usually easier to drive but could be slow depending upon the track.
 
The other major factors that need to be considered in gear selection are weight of the car, track layout (slow speed [turny, flat road course] or high speed track [most Kings]), and tire diameter.

I like your descriptors of running 9/43 ratio with 72 pitch gears. What you described is exactly the performance our cars have especially running on a small flat track - no long straightaways or a huge bank. Keeping the rpms up is the key for our track and that motor I broke in earlier just did not respond. It did not help with the way the twine was tied and the excess twine was pointed towards the motor hole. Sniped the excess twine off, some improvement but NO DICE! I pulled the motor apart and the stacks kind of looked normal except there was no balance marks on the stacks! All of my other H7 had balance marks - mistake or was it a perfectly balanced arm?

Sent from my SAMSUNG-SM-N920A using Tapatalk
Rick Ortogero

#44 Ramcatlarry

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Posted 15 November 2017 - 11:46 PM

Logically the arms are tied and balanced before the arms are assembled in the can.  Alteration of the tie would alter the balance.  The China balance is not a high precision balance, I believe.  I test the balance by how much the motors bounce around on the test bench. Some are better than others.


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#45 Rob Voska

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Posted 16 November 2017 - 07:39 AM

A while back someone posted about using a speaker & meter to measure vibration..... anyone remember that?







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