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Old 07-12-2006, 06:48 AM   #181
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Finally Josh has managed to identify the root cause of the problem.

Point 4 sums it up nicely. Existing motor technology (wet magnets etc) has been the mainstay of the 540 size motors we use for years, possibly since the beginning.

Winds have gone down, endbell designs have changed, but the internal magnets are pretty much the same.

Energy cannot be destroyed - merely transferred. In motors, the inefficiencies of the motor mean the excess energy is converted to heat. Look at the labels on you dyno printouts, how many motors get above 70% efficient at peak RPM?

Find a solution which means more efficient (brushed) motors and a corresponding reduction in the number of cells means that we can be as quick but without the heat and wear and tear issues.
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Old 07-12-2006, 07:01 AM   #182
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Wow, couple of great points made by Josh. I'm not a person that runs modified. However, a few of the stock guys and myself in my area have noticed the heat issue in stock as well. The past weekend I over-heated 2 speedo's running stock in Jackson, NJ. Which brings me to a question. Are we noticing the heat issue to be prevalent running rubber tires? I've never smoked a speedo or had heat problems running foams indoors. That leads me to beleive that a big part of the issue would be the rolling weight of the drive train of the car with rubber tires. Accelerating all that weight and slowing it down upon corner entry. I understand the difference between climates (72*-80* indoors vs. 90*+ ambient track temps outdoors). So, the 2 speed and/or mechanical braking system make a lot of sense to me. Making either work and/or fit in the car is whole different issue without adding a significant amount of weight to the car. These things are too heavy to begin with, but as Josh suggested, dropping a cell or two may bring that over-all weight back to the same point or even less.
I like the idea of adding vents to the body. However, would that be enough air to the motor and speedo in tight slow sections of a course? Never tried it so I can only speculate. I guess a little testing could go a long way.
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Old 07-12-2006, 07:20 AM   #183
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*applause for Josh* i'm with you...

1 thing though: an 'electric' 2-speed would have to be more complicated than a gas 2-speed. You can't use 2 1-way bearings for electric, since you need the motor to do the braking!

A little birdie told me that the 'Blue' team was against sintered/stacked magnets for Brushless. Burito?
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Old 07-12-2006, 07:25 AM   #184
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[QUOTE=elvo]*applause for Josh* i'm with you...

1 thing though: an 'electric' 2-speed would have to be more complicated than a gas 2-speed. You can't use 2 1-way bearings for electric, since you need the motor to do the braking!

[QUOTE]

Same here, plus adding a 2 speed would be adding rotating mass, and would be yet another 80$+ part to add to the car.. not my favourite choice.

But Josh voices some great options, 5 cell is probably a good choice.
It will not ask for a radical resign of the cars, nor a drastic motor change, and would be somewhat easy to implement quickly...

Will the battery matchers be happy to sell 1/6th fewer packs ?? (just kidding)
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Old 07-12-2006, 07:35 AM   #185
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@Elvo:
Where did you here the stack issue??

Its pretty stupid, or lets say much more complicated to run those bonded stacks, like it is in the EFRA or Ifmar now......
With the bonded magnets you are almost forced to run an ugly sensor wire and those magnets brake faster.
Also you have more heat problems with the bonded stacks.

I wonder how this rule was decided?? It could have been so much easier and more reliable with a full neodym stack.....

Markus
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Old 07-12-2006, 07:37 AM   #186
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One more add:

With a full neodym stack for BL, you have to go to 4 cells though, as the power is better than with a bonded BL stack....
Markus
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Old 07-12-2006, 07:46 AM   #187
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just thought i'd share what i found in testing at a local race meet tonight..

track is indoor asphalt ~10-11 seccond lap.

motor used was 7x1, 12 timing for 6 cell, 18 for 4 cell (didn't play with spring tensions - MR 3.8).

dropping to 4 cells reduced motor temp by ~25C.

lap times were around 0.1 - 0.3 secconds per lap slower.

less blackening on edge of comm from arcing and in gernal looked _alot_ better.

gearing up a few teeth with 4 cell gave best results, if taken too far lap times slowed.
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Old 07-12-2006, 07:50 AM   #188
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Always on the assumption that something needs to be done - which I am still sceptical about, it looks like the 2 easiest ways of reducing speed/improving reliability are 1 - limit battery capacity to say 3000mah, 2 - limit battery voltage by going 4 or 5 cells, and 3 - for reliability alone but not speed - do something about motor magnets.

Neither of these 3 suggestions will require any radical changes in car design, so that has got to be a plus.

Josh says we are too small a market for the manufacturers to bother with. Are you sure about that? Don't Sanyo, Panasonic and GP still make 3000s? So if every single person racing RC around the world had no choice but to run 3000s wouldn't it be worth the manufacturers while stepping up production again?

Granted that the matchers don't bother doing anything but 4200s at the moment. That's understandable, but if everyone had to use 3000s we would soon see the matchers at work on 3000s again.

The other possibility of 4 cells and therefore less weight to carry around, is also attractive and easy to implement. There's just one problem with that one, that I see. What happens in a couple of years time when a 4 cell pack gives more power, time, etc than a present 6 cell, and we are running cars that are 150 grams lighter?

The only real solution is 4 cell with a 10 year limit on capacity, but again there are problems! I still think - if it ain't broke, don't fix it.
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Old 07-12-2006, 07:54 AM   #189
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Quote:
Originally Posted by Mr. Blonde
@Elvo:
Where did you here the stack issue??

Its pretty stupid, or lets say much more complicated to run those bonded stacks, like it is in the EFRA or Ifmar now......
With the bonded magnets you are almost forced to run an ugly sensor wire and those magnets brake faster.
Also you have more heat problems with the bonded stacks.

I wonder how this rule was decided?? It could have been so much easier and more reliable with a full neodym stack.....

Markus
@Markus: a little birdie that runs GM motors told me :-)

The bonded magnet rule was conceived, I think at the off-road Euro's in Vienna a couple of years ago. Representatives from most large manufacturers were there. (Mike, Oscar, probably Reto too...) (OK Markus, maybe GM wasn't represented...) The goal was to make sure that B/L motors would NOT be much more powerful than brushed motors all of a sudden. To keep things equal, since B/L and brushed would be raced together.


it's true, the current rules for B/L motors are way too restrictive. Maybe even a little silly.

We need neodymium magnets for brushed motors, too...
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Old 07-12-2006, 07:56 AM   #190
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Quote:
Originally Posted by johnbull

Granted that the matchers don't bother doing anything but 4200s at the moment. That's understandable, but if everyone had to use 3000s we would soon see the matchers at work on 3000s again.
Rather than having everyone go out and get new battery packs again, just put the cap at 4200 for the next "x" amount of years.
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Old 07-12-2006, 08:00 AM   #191
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Quote:
Originally Posted by modeltech
So Terry, get Clive to look at an external, inline, current/voltage restrictor that is small, simple to install, reliable, cheap to produce and flexible to be changed as required, you have a world wide market at your feet just crying out for it apparently..................good luck if you choose to accept this mission.....
Mike mission accomplished, at least the "what you need is one of these" part!!

What is needed to solve the problem has nothing to do with current or voltage or power. There's no need for expensive changes to cars, cells or other equipment. It's very high tech, in fact it's an amazing device. Nobody ever listened when we mentioned the idea before maybe there's more interest now? Anyhow the device to solve the problems is...

a solid state accelerometer

This device would limit acceleration, top speed and cornering speed. It would be simple to install in a car as it would easily fit in-line in the throttle channel and not require any wires to be cut or other modifications to be made. It would be very small and light and would most likely not be too expensive. The race organisers could bear the cost and supply them to the competitors. It could be used in any race class, either for electric or even for nitro cars.

Any better ideas guys???
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Old 07-12-2006, 08:00 AM   #192
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Quote:
McSmooth Quote:

Rather than having everyone go out and get new battery packs again, just put the cap at 4200 for the next "x" amount of years.

Too late, aren't there whispers of 4700's coming out there?
6000 or bust...

Last edited by TC Guy; 07-12-2006 at 08:06 AM. Reason: (sp)
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Old 07-12-2006, 08:05 AM   #193
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@Elvo

I think its not the point, that maybe someone was against that or not....
At that time maybe nobody even thought about the problems there are now.....

It just could be so much easier with the full type magnet..........
I've seen so many manufacturers having problems with bonded magnets....
Markus
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Old 07-12-2006, 08:11 AM   #194
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Do what Nascar does, have a gearing rule.... I'm going to bet that much of the heat is caused by people severly overgearing. Actually, I know it is, I've done it....
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Old 07-12-2006, 08:16 AM   #195
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Quote:
Originally Posted by Mr. Blonde
@Elvo
I think its not the point, that maybe someone was against that or not....
At that time maybe nobody even thought about the problems there are now.....
It just could be so much easier with the full type magnet..........
I've seen so many manufacturers having problems with bonded magnets....
Markus
Of course! At the AGM at the end of this year, one of the proposals will be "allow full (stacked) neodymium magnets". I will vote for my country to vote 'YES'.

Novak even wrap their bonded magnets with kevlar :-s
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