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Old 12-09-2009, 10:00 AM   #16
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Originally Posted by gacjr0 View Post
I agree in principle, but here we are talking about 20g, less than 1.5% of the car total weight.

OTH adding 100g to the car in the right places might make the car more stable, better balanced, give more traction and the guy would become unbeatable?
Perhaps 100g is a bit much, but in conditions of low traction adding weight in the right places is not a bad idea.
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Old 12-09-2009, 11:07 AM   #17
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How about:

Why the hell are you bothered about 20g ? I'd keep it this way, this way you'll never have any issues with the car being found underweight.
+1 ,I'm surprised nobody wrote that before...

Furthermore, with Lipo and some handout/spec tires I feel we are close to experience lack of sufficient pressure on the tires. Really 20 grams can't hurt at all, I'd even be tempted to say the contrary...

Off topic: wouldn't it be a good idea to go back to 21mm tires with lipos in order to increase pressure on the rubber ?
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Old 12-09-2009, 12:25 PM   #18
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I've seen more cars lose their batteries since the new weight limits. I've kept my lipo balancing weights, as the car is both balanced and the batteries are held in securely.

Car is 1400g, depending on tyres. And thats with 70g of lipo weights. Its all very well having a light car, but to finish first, first you have to finish, so if lightweight parts are introducing reliability issues, then whats the point of them?
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Old 12-09-2009, 12:59 PM   #19
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i am happy to be running my cars at 1400g

i cannot get down to 1350 without loosing the cars balance and stability

at least i wont fail Tech inspection because of weight
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Old 12-09-2009, 02:20 PM   #20
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I know 20g isn't much, but I like to stay sharp on 1400g
In high traction conditions there are better to have a light car, but some of you guys say that on low traction conditions you should put weight in the right place; where is the right place?

Another question about heatsink:

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Originally Posted by niznai View Post
Nah, heatsinks are exactly that: things that sink heat. They work by increasing the surface area of the body that is heating up, so heat is more effectively dissipated. As long as you can't put one on the rotor, the outside of the motor is next best thing.
When you have a 13.5 motor, should I run with or without heatsink? I mean, last time on a big competition I didn't have a heatsink because of the weight, but do the heatsink dissapate the heat from the motor when it is like 105 degres celsius?
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Old 12-09-2009, 05:33 PM   #21
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I know 20g isn't much, but I like to stay sharp on 1400g
In high traction conditions there are better to have a light car, but some of you guys say that on low traction conditions you should put weight in the right place; where is the right place?


When you have a 13.5 motor, should I run with or without heatsink? I mean, last time on a big competition I didn't have a heatsink because of the weight, but do the heatsink dissapate the heat from the motor when it is like 105 degres celsius?
i run on carpet with rubber tires and i never use a heat sink on the motor some times on esc but not allways.
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Old 12-09-2009, 06:10 PM   #22
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i run on carpet with rubber tires and i never use a heat sink on the motor some times on esc but not allways.
+1

If you're not running mod, ditch the heat sinks and fans, their useless.
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Old 12-09-2009, 06:46 PM   #23
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Originally Posted by niznai View Post
Nah, heatsinks are exactly that: things that sink heat. They work by increasing the surface area of the body that is heating up, so heat is more effectively dissipated. As long as you can't put one on the rotor, the outside of the motor is next best thing.
The problem is that the heatsinks never make great contact all the way around the can. That's why PC heatsinks use compound etc to help conduct heat.

I just think the problem is that someone has their motor running right on the limit temp wise, so they stick a heatsink/fan on it and the temp drops, they then gear up as they think the motor will now take a lot more.

I just believe that the heatsink on the outside (although it does obviously dissipate some heat) gives a false impression compared to the real temps inside the can where it actually matters. i.e. the temp outside drops by 15-20degC but inside maybe only 5degC etc.

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Old 12-10-2009, 06:22 AM   #24
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|How about Running car with and without heathsink &fan and Check the Temp. Difference
With Fan & Heathsink Total temp -5 to -10 Degrees means They Works
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Old 12-10-2009, 08:08 AM   #25
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|How about Running car with and without heathsink &fan and Check the Temp. Difference
With Fan & Heathsink Total temp -5 to -10 Degrees means They Works
Well, the temp outside the motor drops with about 20-30 degrees with a heatsink on the motor, so I belive that it make some diffrence. I know you don't need a heatsink in modified, but I don't fance buying new motors all the time (I've burnt three motors without heatsink).

What about the weight of the car, do you know more ways to lower the weight?
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Old 12-10-2009, 08:18 AM   #26
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Originally Posted by Skynet View Post
Well, the temp outside the motor drops with about 20-30 degrees with a heatsink on the motor, so I belive that it make some diffrence. I know you don't need a heatsink in modified, but I don't fance buying new motors all the time (I've burnt three motors without heatsink).

What about the weight of the car, do you know more ways to lower the weight?
20 grams over isn't exactly portly, I've seen scales off that much. Also if your burning up motors all the time maybe heat sinks and fans aren't the answer, maybe you should try changing your FDR instead. Just a suggestion.
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Old 12-10-2009, 10:18 AM   #27
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Running the car with a heatsink can sometimes mask a problem rather than solve it as suggested by many people here. The point about contact is quite good too. There are places that sell the compound you need to make sure you've got good heat transfer between can and heatsink. I have used it, and it does the job. But again, that might not be the solution. Heatsinks work as long as there is a temperature gradient between the source and the ambient, no matter how small. Of course they are less efficient when the gradient is small, but they do work.

As someone already pointed out, if you're burning out motors, I am too inclined to think that you have a problem elsewhere. One thing is sure after all this discussion. It's not the extra 20 grams that's burning your motors. I can guarantee that one.

Not to mention someone pointed out already that the scales we use are not that accurate and can be out by 20 grams easily.

As for being right on the legal weight, that's very risky. One solid knock, you lose a 5gram weight, you're disqualified. I have seen it happen too many times.

Come to think of it, your car will lose enough weight for you to get disqualified from the relativistic effects of converting electric power to mechanical work during the race alone, so you gotta watch that!
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Old 12-10-2009, 11:01 AM   #28
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As someone already pointed out, if you're burning out motors, I am too inclined to think that you have a problem elsewhere. One thing is sure after all this discussion. It's not the extra 20 grams that's burning your motors. I can guarantee that one.
Well, I know the motors doesn't burn because of the 20g. I don't want to mix these two topics. When I use heatsink, I can have a higher FDR, when I don't use a heatsink, I must use a lower FDR.

I know 20g isn't much, but I just want to know what I can perform on my car to get rid of these 20g. Next time it can be 100g, what should I do then? This thread wasn't meant to become a discussion between if 20g does any matter, I started it because I want to know how to ger rid of the extra weight
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Old 12-10-2009, 11:32 AM   #29
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Originally Posted by Skynet View Post
Well, I know the motors doesn't burn because of the 20g. I don't want to mix these two topics. When I use heatsink, I can have a higher FDR, when I don't use a heatsink, I must use a lower FDR.

I know 20g isn't much, but I just want to know what I can perform on my car to get rid of these 20g. Next time it can be 100g, what should I do then? This thread wasn't meant to become a discussion between if 20g does any matter, I started it because I want to know how to ger rid of the extra weight
As has been mentioned already, change everything for lightweight versions of parts, keep wires as short as possible etc.

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Old 12-10-2009, 11:59 AM   #30
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Quote:
Originally Posted by Skiddins View Post
The problem is that the heatsinks never make great contact all the way around the can. That's why PC heatsinks use compound etc to help conduct heat.

I just think the problem is that someone has their motor running right on the limit temp wise, so they stick a heatsink/fan on it and the temp drops, they then gear up as they think the motor will now take a lot more.

I just believe that the heatsink on the outside (although it does obviously dissipate some heat) gives a false impression compared to the real temps inside the can where it actually matters. i.e. the temp outside drops by 15-20degC but inside maybe only 5degC etc.

Skiddins
I know this forum is about how to lose 20grams, but on the topic of brushless motors and heat sinks with a 13.5, it's my impression that they do make a pretty big difference, for me anyway they bring the temps down 20deg or so. With a brushless motor i would think that all the heat produced stays in the can for the most part and doesn't transfer to the rotor. The heat comes from resistance in the windings which are attached to the can itself. The magnetic force isn't going to transfer heat, to the rotor. It's a different story in brushed motors however because the current is running through the rotor, so obviously the resistance in the wires on the rotor will produce the heat.

I don't know about you guys but I still plan on running a heat sink with fan. The thermal compound would also help but it will get messy i think.

my 2cents, eventhough the bank won't accept it.
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