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#1 Zippity

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Posted 13 May 2017 - 11:11 PM

or tall, that you can gear a motor and it still remains competitive?






#2 swodem

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Posted 13 May 2017 - 11:27 PM

Of course.

#3 Zippity

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Posted 14 May 2017 - 12:08 AM

So what is that magical number?

 

Or it it just when the times starting getting slower?

 

The reason I am asking this dumb(?) question, is because I have been playing around with completely different ratios to what is normally accepted for our track, and the results have been nothing short of amazing.

 

Maybe it is the armatures, maybe it is the cans and magnets, but whatever it is, its throwing all my previously held thoughts and beliefs, out the window :)

 

I have rearranged a gear ratio chart to make this task more simpler to understand - well for my brain anyway.

 

Attached File  GearRatios_LtoS.pdf   24.53KB   106 downloads



#4 Samiam

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Posted 14 May 2017 - 12:47 AM

What kind of motors are you building?


Sam Levitch
 
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#5 Zippity

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Posted 14 May 2017 - 12:56 AM

G12 and S16D. We also race the PS4002FK :)

 

What got me going on all this, was that I had placed a 38° Bill Bugenis Large Diameter arm into a Cahoza setup with T2 magnets and it was as slow as a wet week.

 

We normally gear our G12 motors at 8:42 and race them in Eurosport chassis on our 175 foot flat track.

 

I started with a 9:41 ratio but that was too slow. Then I tried 8:42, 7:42 and 10:40 but all got progressively slower.

 

Today I tried 11:42 and my car was a flyer :)



#6 chasbeeman

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Posted 14 May 2017 - 04:28 AM

I'm curious what motors have been used that defy the previously recommended gear ratio?
Charles Beeman

#7 Samiam

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Posted 14 May 2017 - 07:10 AM

I would have thought the 10/40 gear set would have started to show an improvement. The ratio you settled on is on the other end of the chart from the norm. As long as it doesn't leak smoke, keep on truckin' .

 

I guess this shows that we should try out of the box ratios before throwing a motor into the dog house. Especially the sealed ones where there are no other options. 


Sam Levitch
 
"If you have integrity, nothing else matters, and if you do not have integrity, nothing else matters."
     Robert Mueller, special counsel (2013)

#8 slotcarone

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Posted 14 May 2017 - 07:35 AM

It will most likely go up in smoke!! :) 


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#9 Zippity

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Posted 14 May 2017 - 09:08 AM

Methinks hope you are wrong.
 
The motor was quite cool after many laps running. :)

#10 MSwiss

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Posted 14 May 2017 - 09:11 AM

I think Mike K was answering the question in the title.

Like, Sam, I'm surprised 10/40 wasn't an improvement.

Mike Swiss
 
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Two-time G7 World Champion (1988, 1990)
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#11 Zippity

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Posted 14 May 2017 - 09:23 AM

Oh?

 

OK :)

 

Maybe it is the armature, maybe the air gap??



#12 Samiam

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Posted 14 May 2017 - 09:25 AM

Ron,

Off hand, do you know what air gap is in that motor?
Sam Levitch
 
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     Robert Mueller, special counsel (2013)

#13 Zippity

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Posted 14 May 2017 - 09:36 AM

Sorry Swiss,

 

I just checked my notes, and the car did indeed go faster with the 10:40 ratio gearing. I cranked the timing up to 11:42 and it went even faster. Hence my question about how far can I go  :)

 

Sam, the air gap is .556" and the arm diameter .540"



#14 Samiam

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Posted 14 May 2017 - 10:04 AM

That's a pretty tight gap for a cool running motor.  Have you ran it race hard for one of your heat lengths?


Sam Levitch
 
"If you have integrity, nothing else matters, and if you do not have integrity, nothing else matters."
     Robert Mueller, special counsel (2013)

#15 MSwiss

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Posted 14 May 2017 - 10:31 AM

Too many Mother's Day chores to get into a long desertation on air gaps, but .005" or .006 a side, was very common.

Increasing the distance of the arm to the magnet,while increasing the volume of air passing through the motor, also effectively makes the magnet weaker.

Mike Swiss
 
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990)
Eight-time G7 King track single lap world record holder
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Make checks out to Chicagoland Woodworking, Inc.


#16 Les Boyd

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Posted 14 May 2017 - 11:36 AM

The 9:41 (4.56) would be slow but going to 8;42 (5.25) is slower and 7:42 even slower. At these ratios the motor should run some what cool as you are not putting much load on them.

10:40 (4.0) is closer but I would try close to 3.8 to 3.6 ratio 10:38 to 36 or 11:41 to 39.
  
Check your motors after a few laps they may start to slow down as the motor builds heat, and could go up in smoke.
The answer is run the ratio as low as you can without toasting the motor.

#17 gotboostedvr6

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Posted 14 May 2017 - 12:01 PM

Zippity,

Pull your brushes and take a picture of the faces for me.

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."
-David Parrotta


#18 jimht

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Posted 14 May 2017 - 12:48 PM

I'm surprised at all these opinions when nobody asked abut the tire diameter or track voltage.   :unknw:


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#19 Zippity

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Posted 14 May 2017 - 04:44 PM

.682" JK 8710PP and 12.55 volts. :)

#20 jimht

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Posted 14 May 2017 - 05:39 PM

And there you are... what makes sense at 13/16" and 13.2v may not be sensible at .682" and 12.55v.
5.60 vs. 4.63 at 11/42, effectively 5.60 gearing and that isn't too tall with a small tire at a lower voltage.
 
Gear chart at .825"
 
Gear chart at .682"

Jim Honeycutt

"I don't think I'm ever more 'aware' than I am right after I hit my thumb with a hammer." - Jack Handey [Deep Thoughts]


#21 gotboostedvr6

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Posted 14 May 2017 - 07:21 PM

It's too tall. Way too tall in fact.

Zip races on a flat track.

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

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#22 jimht

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Posted 14 May 2017 - 08:57 PM

Post #5: "Eurosport chassis on our 175 foot flat track".

 

Why argue with a lap timer?

 

So, high torque cool running big diameter arm in a lightweight Eurosport chassised car, low voltage, and the gear ratio works because of the effectively lower ratio of small tires that allow it to wind up quickly.

 

Regardless, I've seen umpteen totally different cars turn the same times and an equal number of identical cars turn radically different times... welcome to hand made slot cars.

 

If there weren't such a fetish for similar (identical) tracks to make it easier for the travelling racer to beat the locals there would be more open-mindedness toward actual reality here.


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#23 Samiam

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Posted 14 May 2017 - 09:27 PM

If it don't leak smoke, and it turns fast laps, then it is right. It may have perplexed Ron enough to post this thread, but it seems that something about this set-up demands this gear set. Same car, tires, and track. Is it the magnets? Arm? What is different about this motor that required such a huge swing in the gear ratio? What are the particulars of the other motors that needed 5.3:1?

 

I only have one car similar to what Ron is running. No flat tracks here but I have run it on the Port Jeff Gerding King. Drives like a wing car. It is geared 7/42.


Sam Levitch
 
"If you have integrity, nothing else matters, and if you do not have integrity, nothing else matters."
     Robert Mueller, special counsel (2013)

#24 Robert BG

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Posted 14 May 2017 - 10:07 PM

Zippity, I think tire size has a bit to do with your results. But having said that, I also think you are seeing the benefits of the larger diameter arm. They usually tend to have a bit more torque from the added mass.

 

What type of set-ups were the others normally running? Something tells me there's going to be a few .518" diameter set-ups being run by those recommending the other ratios.


Robert Fothergill

#25 gotboostedvr6

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Posted 14 May 2017 - 10:58 PM

ISRA guys typically run Open 12 cars with .680" or smaller tires and gear 7/41 or 42.

On our 220 foot Engleman we run scale 12 cars with 8 tooth gears.


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."
-David Parrotta


#26 Zippity

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Posted 14 May 2017 - 11:02 PM

I believe that I am the only person racing a large diameter armature here at the moment.

 

It is not my fastest motor by a long shot, but as I had inherited the armature from the estate of a dear friend, I wanted to give it a run.

 

At first, it was so slow, that I nearly binned it, but decided to persist and think outside the square - hence the rather tall timing.

 

It will make for a great "B" car.  :)



#27 Robert BG

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Posted 15 May 2017 - 10:33 AM

Big diameter arms tend to generate more torque and drive like a V-8 whereas the smaller ones love to rev. Chances are you might be able to throw some more gear at it, just keep an eye on temps. But it should handle it because of the extra mass adds some cooling and carries more torque like I said earlier.

 

As far as someone saying the gap is too tight, listen to Mike because you're right on the mark. I actually will go smaller at times on big arms. But you're right where you need to be.


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#28 anarot

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Posted 18 May 2017 - 11:07 PM

Not only ratios, but also how you get the ratio that counts. eg. 37/11 = 3.63 ratio or 36/10 = 3.6 ratio. Even though the ratio is (almost) the same it makes the motor behave differently. 


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#29 Zippity

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Posted 18 May 2017 - 11:19 PM

11:37 is 3.3636

 

snip.JPG



#30 Benno - SAC

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Posted 19 May 2017 - 12:18 AM

Not only ratios, but also how you get the ratio that counts. eg. 37/11 = 3.63 ratio or 36/10 = 3.6 ratio. Even though the ratio is (almost) the same it makes the motor behave differently. 


Besides your wrong example, could you explain why?
I think, i.e. with 8/32 and 9/36 the motor behaves exactly the same (with same tire diameter of course).

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#31 anarot

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Posted 19 May 2017 - 01:57 AM

So I got the last 2 numbers the wrong way round, but it still doesn't alter the fact that it makes the motor behave differently. I don't know why but it dose. Something to do with the torque I guess.It will be something like because  a 9 tooth pinion the motor will spin higher and the 36 spur gear will spin slower V's the slower spinning 8 tooth motor and the faster spinning 32 spur gear. ( I think I have it the right way round)   Use the example above. 1 will usually have more brakes than the other while the other 1 will be slower off the start line than the other but both will have the same top speed.  

I have of course no proof of this it all to do with the "feel". 

(I am thinking of setting up a 8m long drag strip with timing every 1-2 metres to see if it is true or not but that could be awhile) 


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#32 anarot

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Posted 11 July 2017 - 12:28 AM

Besides your wrong example, could you explain why?
I think, i.e. with 8/32 and 9/36 the motor behaves exactly the same (with same tire diameter of course).

Sorry been away and forgot about this. As I said before I don't really know why. It will be something like with a lower number of teeth on a pinion the motor will be harder to turn but the spur gear easier to turn and vice a versa. In theory a 42 spur and a 14 pinion and a 30 spur and a 10 pinion will give you the same ratio of 3:1 but the motor will behave differently. . Google might be your friend on this one. Here is just one example. 

"The pinion size ( from a 8 to a 7 or vice versa ) change will put the motor in a different RPM/torque curve even if the overall ratio was identical, you could still see, hear and feel a difference in the motor performance."

http://www.racesrp.com/helpful-info-17


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