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Old 02-16-2015, 08:11 PM   #11686
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for anyone running on high bite wet clay using slicks, what is your thoughts on foams.

Here is what I have noticed.

- Proline seem to be good right out of the box, but fade quickly
- AKA reds, need about 2 packs out of the box and then are done after 4-6 weeks.
- JC Grey foams? I have not tried these yet
- Panther orange....like bricks and never seem to break in. Thus the car is sketchy as all get out.

I have been using 2.4 wheels for the most part and there is not much sidewall to refoam, and the rip soon after the foams are done anyway. It would be nice to have a foam that breaks in quickly and holds performance longer. Chances are, I am getting to budget minded, and just need to bite the bullet and replace my tires/foams every 20-30 packs.

going back to 2.2 wheels and tires and refoaming would probably be the most cost effect solution. thoughts?
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Old 02-16-2015, 08:16 PM   #11687
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I dont run a fan because I "need", I run a fan because it is insurance. Less power fade with a cooler motor and longer motor life. I gear my motors for about 150 without a fan, then add a fan to drop temps to 125. this way if my fan fails, I wont fry the motor. last weekend my fan failed and I came off at 150.

Also, we run 5 minute quals and 8-10 minute mains. 150 over 5 minutes becomes 170+ over 8 minutes. Most everyone here is running fans in 17.5. I would not bother in mod.
I was watching a Tekin video the other day and Randy Pike was selling their ESC data logging features by talking about a case where someones fan was dragging down their battery voltage to the point where it was having an impact on performance. Might be worthwhile to understand what kind of load your "insurance" is creating on your battery in such a competitive class. Especially if your fan is always on while you're lining up to start and such.
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Old 02-16-2015, 08:23 PM   #11688
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I have the same track conditions and everybody runs Panther slicks, we ditch the Orange foams and install aka red soft foams. Seems to be the hot ticket.
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Old 02-16-2015, 08:24 PM   #11689
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I was watching a Tekin video the other day and Randy Pike was selling their ESC data logging features by talking about a case where someones fan was dragging down their battery voltage to the point where it was having an impact on performance. Might be worthwhile to understand what kind of load your "insurance" is creating on your battery in such a competitive class. Especially if your fan is always on while you're lining up to start and such.
How can you track fan draw if you're running your fan directly off your Lipo, because you want the most voltage, and want to limit the amount of possible issues with driving the fan?
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Old 02-16-2015, 08:33 PM   #11690
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How can you track fan draw if you're running your fan directly off your Lipo, because you want the most voltage, and want to limit the amount of possible issues with driving the fan?
I didn't intend this to be a Tekin commercial but with my ESC, I just connect the hotwire after a run and download the data. It gives me a nice graph of voltage over time.

Without that capability, I might try checking my voltage at the battery before turning on the fan then turn on just the fan for 60 seconds and check it again. That should give an idea of how much the fan is dropping your voltage on its own. It shouldn't be too hard to wire a multi meter inline to measure amperage draw from the fan as well.

I would be willing to bet some of you guys are losing way more performance with those fans than you would gain by dropping a full ounce of weight.
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Old 02-16-2015, 09:02 PM   #11691
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I have a suggestion for page one. When I got my swaybar kit I tried searching for how to install it before I opened the package. It was hard to find anything. Once I opened the package it was easy to figure out but it could be helpful to have a note about it. Below are pictures from couple different angles. If they aren't clear enough I can get out the real camera instead of using my iPhone.
I'll be happy to add any "how to" on the front page. Work up a writeup with well lit pictures and text, and I will add it. Don't just demand something be done. Be an asset and make a contribution.

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Old 02-16-2015, 09:07 PM   #11692
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isn't the amp draw on these fans less than a full amp (and these stock motors can't draw enough amps to tax our batteries anyway)? i find it hard to believe it would draw enough to negatively impact speed/punch.

of course i could be wrong. wouldn't be the first time...
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Old 02-16-2015, 09:28 PM   #11693
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There is no way running a fan is going to effect your performance that you would notice I would bet. They are MANDATORY on 17.5 TC and voltage is way more sought after and important there IMHO.

It is a nice piece of insurance as Wildcat sad. Plus it's cool... literally.

I would run smaller wires to that motor too.. It will clean it up even more and loose those precious grams... LOL.
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Old 02-16-2015, 09:30 PM   #11694
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isn't the amp draw on these fans less than a full amp (and these stock motors can't draw enough amps to tax our batteries anyway)? i find it hard to believe it would draw enough to negatively impact speed/punch.

of course i could be wrong. wouldn't be the first time...
The amperage pulled by a fan will depend on how much airflow it creates and how efficient it is at creating that airflow. As I understand it, some 17.5 racers are doing ridiculous things to get temp reductions in IR of their batteries. And people will spend money to get a 1 percent reduction in rotating mass. Drawing one amp of current for two or three minutes before a race begins could certainly make a difference.
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Old 02-16-2015, 09:35 PM   #11695
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There is no way running a fan is going to effect your performance that you would notice I would bet. They are MANDATORY on 17.5 TC and voltage is way more sought after and important there IMHO.

It is a nice piece of insurance as Wildcat sad. Plus it's cool... literally.

I would run smaller wires to that motor too.. It will clean it up even more and loose those precious grams... LOL.
Really? And just how many amps would you need to pull while you do a few hotlaps and wait for a race to start before it makes a noticable difference?
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Old 02-16-2015, 09:43 PM   #11696
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Quote:
Originally Posted by Wildcat1971 View Post
for anyone running on high bite wet clay using slicks, what is your thoughts on foams.

Here is what I have noticed.

- Proline seem to be good right out of the box, but fade quickly
- AKA reds, need about 2 packs out of the box and then are done after 4-6 weeks.
- JC Grey foams? I have not tried these yet
- Panther orange....like bricks and never seem to break in. Thus the car is sketchy as all get out.

I have been using 2.4 wheels for the most part and there is not much sidewall to refoam, and the rip soon after the foams are done anyway. It would be nice to have a foam that breaks in quickly and holds performance longer. Chances are, I am getting to budget minded, and just need to bite the bullet and replace my tires/foams every 20-30 packs.

going back to 2.2 wheels and tires and refoaming would probably be the most cost effect solution. thoughts?
Our track doesn't seem quite as high traction. A Few guys run slicks, but most stick to treaded/ghosted tires as the track always tends to dry out later in the night. But I would still consider it high-grip clay.

That being said most everyone runs either AKA reds or JC Dirttech (grey). The reds come in faster, but don't last quite as long. The JC take a while to break in. More like 4-6 runs. But they have tended to last longer and provide better traction. It seems that if you have the time to break them in, run the JC grey, but if you need the tires sooner run the AKA red.
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Old 02-16-2015, 09:50 PM   #11697
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The amperage pulled by a fan will depend on how much airflow it creates and how efficient it is at creating that airflow. As I understand it, some 17.5 racers are doing ridiculous things to get temp reductions in IR of their batteries. And people will spend money to get a 1 percent reduction in rotating mass. Drawing one amp of current for two or three minutes before a race begins could certainly make a difference.
You realize we have a minimum 2 minute practice before a 10 minute main, right?

I have a strong feeling you're not a 17.5 racer, and are using tons of theorycraft and creative guessing to come to some sort of point that running a fan isn't a good idea because of the small amount of amp draw it MIGHT have. Your terms like, "temp reductions in IR of their batteries" literally makes no sense.

The amp draw of a common 30mm fan is so negligible, it's a non factor with the current batteries we're using. The added bonus it gives a 17.5 racer far out weighs any sort of possible amp draw. I know some basic 12V 92mm fan amp draw numbers off the top of my head, and you're in the realm of .15 to .2 amp hours of usage.

Let's say it's a steady curve of efficiency, and a 30mm fan is 1/3rd the size of the given numbers above, this will put it's presumed amp hour at .05.

This would convert to the fan consuming 500MAH over a 1 hour period. The car is physically turned on for let's say 12 minutes. This would show a total possible consumption of 99.6 MAH over this time frame.

I would give up 100 MAH of my 5000MAH, this is literally 2% of total battery consumption for an entire run during a main event.

The amount of feel added by running a fan is massive - I dropped literally 45 + degrees, and can now run taller gear, thus allowing my car to move faster and more efficiently around the course, while also extending the life of the motor and other electronics.

Sorry if this comes off as inflammatory, I have an issue with people guessing and not doing basic math to figure out a very obvious claim.

Edit: Another comment you had was about dropping an ounce of weight. Any serious 17.5 racer is under the 1499 limit, and is adding weight in certain places to get back to the minimum.
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Old 02-16-2015, 10:06 PM   #11698
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You realize we have a minimum 2 minute practice before a 10 minute main, right?

I have a strong feeling you're not a 17.5 racer, and are using tons of theorycraft and creative guessing to come to some sort of point that running a fan isn't a good idea because of the small amount of amp draw it MIGHT have. Your terms like, "temp reductions in IR of their batteries" literally makes no sense.

The amp draw of a common 30mm fan is so negligible, it's a non factor with the current batteries we're using. The added bonus it gives a 17.5 racer far out weighs any sort of possible amp draw. I know some basic 12V 92mm fan amp draw numbers off the top of my head, and you're in the realm of .15 to .2 amp hours of usage.

Let's say it's a steady curve of efficiency, and a 30mm fan is 1/3rd the size of the given numbers above, this will put it's presumed amp hour at .05.

This would convert to the fan consuming 500MAH over a 1 hour period. The car is physically turned on for let's say 12 minutes. This would show a total possible consumption of 99.6 MAH over this time frame.

I would give up 100 MAH of my 5000MAH, this is literally 2% of total battery consumption for an entire run during a main event.

The amount of feel added by running a fan is massive - I dropped literally 45 + degrees, and can now run taller gear, thus allowing my car to move faster and more efficiently around the course, while also extending the life of the motor and other electronics.

Sorry if this comes off as inflammatory, I have an issue with people guessing and not doing basic math to figure out a very obvious claim.
How about you go and tell Randy from Tekin that his data was wrong.

Do you really have no clue that people are doing crazy things like double cycling their packs at very high rates to raise the internal temperature? That gives them a temporary reduction in internal resistance so the battery will supply more current. Does it make more sense to you now?

I was trying to be helpful and pass on something I learned in the Tekno video I watched. The attitude some of you have in this thread is really sad though. To me you come off like an angry little kid.

So why don't you do some math for us and post how much current draw it takes for how long to drop your battery voltage enough to notice. Otherwise you're just guessing whether or not it matters more or less than shaving a few grams of weight from your drivetrain.
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Old 02-16-2015, 10:20 PM   #11699
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How about you go and tell Randy from Tekin that his data was wrong.

Do you really have no clue that people are doing crazy things like double cycling their packs at very high rates to raise the internal temperature? That gives them a temporary reduction in internal resistance so the battery will supply more current. Does it make more sense to you now?

I was trying to be helpful and pass on something I learned in the Tekno video I watched. The attitude some of you have in this thread is really sad though. To me you come off like an angry little kid.

So why don't you do some math for us and post how much current draw it takes for how long to drop your battery voltage enough to notice. Otherwise you're just guessing whether or not it matters more or less than shaving a few grams of weight from your drivetrain.
I don't need math to figure that, I have real life experience. Motor temperature has played a bigger part in power fade than battery voltage in current racing for me. In all respect to Mr Pike, I think you're either misquoting or misinterpreting what he said as it pertains to 17.5 offroad racing. How about you post the tekin or tekno (You've said both) video for us to gather our own opinion.

As for discharge curves, those are very easy to figure out.

I would recommend taking a minute and reading this thread:

Benchmarking the Best 2S Lipos
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Old 02-16-2015, 10:30 PM   #11700
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So after some basic google research, I came across this PDF:

http://www.teamtekin.com/manuals/TWS...wTo_111513.pdf

Looking at the data, it's VERY easy to see the same conclusion that was drawn in the PDF file:

Quote:
Look closely at Fig. 4, do you see it? His battery voltage drops by 0.37V WITHOUT anything more than
some “Staging” RPM lining up for the loop!* * It turns out his battery was not “bad” but his car was
equipped with 2 fans to cool the motor. These fans were dropping his battery voltage significantly before
he even ran the car.**And yes, 0.37V IS enough to make your car look less punchy than the rest of the
field. So the suggestion; remove the fans. Look at the end of the run, his motor was only 120F, nowhere
near needing exterior cooling.**Next run was without fans. Let’s take a look.
This situation has literally nothing to do with 17.5 off road racing. We're not at a locked Final drive or timing class, nor would we run a battery that could lose that much voltage in such a short amount of time. I also don't see the day when two fans would be needed.

We're also not getting the full story here. Maybe he was only hitting 140 degrees in qualifying, but in say, a 10 minute main he's peaking at 175-200 degrees. A fan would be huge here, however Randy Pike is right in qualifying it isn't needed. I have a feeling this racer needs a new battery anyways based on the discharge data given in the PDF.
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