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Old 11-10-2010, 04:22 PM   #931
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Had my first big race with my 1/12 scale last weekend, and things went pretty well (2nd B-Main), with one problem: starts.

When the car was put on the track before the heat with a fully charged pack, it was a rocket - punch it, and the car was up to full speed very quickly. However, at the start of the heats (and the main ), when the peak on the battery is gone, starts were very sluggish. This cost me big-time in the main, as I dropped immediately from 2nd to 4th - I was able to fight back up to 2nd, but that was as far as I got. Bummer.

My thoughts are that gearing and timing was such that the motor needed a fully charged pack to get going - once the voltage dropped down to a steady-state for the duration of the race, there wasn't enough juice to get the car moving very rapidly from a dead-stop. Once the car was up to speed, it was very fast; nothing on the track was faster.

I don't have my car in front of me right now, but I was running a lot of boost (around 45), and about 18 turbo, with a delay of 0.1, and a ramp of 2. I don't remember what my gearing was, but it was very similar to what other people where running.

I've experienced this problem with both a Tekin 17.5 (with the standard amount of timing (12?) on the can), and an Orca 17.5 with fixed can timing.

Speedo was upgraded to 212; I don't think I was experiencing this problem with the prior version.

Suggestions? Perhaps decreasing the rollout?
I'm betting that your diff was slipping. Nine times out of ten, from a standing start, if the car does not instantly launch, the diff is slipping. Your diff should be so tight that you cannot move the spur with your thumb when holding both tires. However, the diff must also be free and not binding. A well built and functioning diff is one of the most important parts of an efficient 1/12th.
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Old 11-10-2010, 07:12 PM   #932
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Motor Temp....`1cell lipo set-ups don't seem to work well when the motor is over about 135*. I've run many test, gearing high, low, timing high, low, 40c, 50c packs, the response is always the same, once the motor reaches about 140 the punch is gone. I can gear up to keep the speed up but it will loose punch and ultimately lap times drop.
Mama always told me it's ok to talk to myself, but if I answer back, well, that's not so good

From the sounds of it, I may have to go to a lower FDR to avoid driving the temperature up too much. I'll have to give it a try this weekend.

It was also suggested that my diff might be loose. I talked with another very experienced driver, and he checked my diff and said it was ok. Besides, if the diff was loose, I would have noticed it at the beginning of warmup, which I didn't.

We have lots of time before racing this Friday, so I may have to run a few tests to narrow down the cause.
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Old 11-10-2010, 07:41 PM   #933
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the diff is a little tighter than a TC diff
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Old 11-10-2010, 07:47 PM   #934
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the diff is a little tighter than a TC diff
Tighter? Hmmm, not what I was told.

I've scored the diff rings with sandpaper in two directions, one at right angles to the other. I was told that this was supposed to give the balls something to bite into once the groove was established, so you didn't have to tighten the diff as much, which means it runs a bit smoother.

This seemed to work for my friend, as he finished 2nd in the A-Main in the 10.5 1/12 class....then again, in that class you would naturally have to have a tighter diff due to the extra power being laid down...

But, it's worth a try. Perhaps I didn't score the rings enough, and that, combined with the slightly looser diff may be causing the problem.

I know that if a TC diff is loose, you'll hear it squeal from the driver's stand - will a 1/12 diff make the same sound, or does the reduced power cause it to be quieter?
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Old 11-10-2010, 07:58 PM   #935
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Mama always told me it's ok to talk to myself, but if I answer back, well, that's not so good

From the sounds of it, I may have to go to a lower FDR to avoid driving the temperature up too much. I'll have to give it a try this weekend.

It was also suggested that my diff might be loose. I talked with another very experienced driver, and he checked my diff and said it was ok. Besides, if the diff was loose, I would have noticed it at the beginning of warmup, which I didn't.

We have lots of time before racing this Friday, so I may have to run a few tests to narrow down the cause.
You have PM
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Old 11-10-2010, 09:02 PM   #936
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You have PM
Got it! Thanks very much, I'll have to give the setup a try. Just need to lay my hands on a Trinity 17.5 now
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Old 11-11-2010, 12:05 AM   #937
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My first thought was that 18 is a lot of turbo to be running along with 45 timing and a .1 delay. If it were me I would drop the turbo entirely for a quick run and see if the problem disappears. If so, add back turbo 2 degrees at a time until you feel the loss of power again and back up one step. I think a general rule of thumb is to not apply more than 60 degrees of timing at any time. My typical setups for 12th don't have more than 7 degrees of turbo and its usually 5 with 45 timing in 13.5 and 50 timing in 17.5

AWD

BTW, I think this below ought to be considered the Bible when it comes to building a diff. No fancy sanding or expensive balls are needed. Cheap steel balls cleaned with motor spray, AE 6636 lube, and rings straight out of the package after being cleaned with motor spray. I use the 1$ avid bearings, 2$ rings and buy the balls in bulk for something like $14 for 100. Kimbrough 76 spur, and you will be golden if you build it like Frank explains.

http://www.teamcrc.com/crc/modules.p...article&sid=36
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Old 11-11-2010, 01:49 AM   #938
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I think maybe drop your rollout will help with motor temps. If it was the diff slipping you would be able to hear it slipping I know I can on my 12th.
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Old 11-11-2010, 05:53 AM   #939
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My first thought was that 18 is a lot of turbo to be running along with 45 timing and a .1 delay. If it were me I would drop the turbo entirely for a quick run and see if the problem disappears. If so, add back turbo 2 degrees at a time until you feel the loss of power again and back up one step. I think a general rule of thumb is to not apply more than 60 degrees of timing at any time. My typical setups for 12th don't have more than 7 degrees of turbo and its usually 5 with 45 timing in 13.5 and 50 timing in 17.5
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i agree,my 12/wgt are between 50-60 with a few time there is no turbo
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Old 11-11-2010, 09:11 AM   #940
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Im interested to see what setting people are running with the D3 motor and 212 software on a small 80 x 40 track in TC
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Old 11-11-2010, 09:35 AM   #941
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Im interested to see what setting people are running with the D3 motor and 212 software on a small 80 x 40 track in TC
not saying you won't get any help in here. but there maybe racers that don't visit this thread because it is for 1s implementations. now if you are running 1s in your tc, this is the right place to be, but i have not seen many that run that configuration, so it may take a while to get an answer

you may try http://www.rctech.net/forum/electric...-sensored.html
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Old 11-11-2010, 11:11 AM   #942
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oops
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Old 11-11-2010, 11:17 AM   #943
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oops
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Old 11-11-2010, 01:14 PM   #944
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My recent experience with 1S and 203/208/212 is that people over-gear by a significant margin. Motor temps don't seem to guide so well on 1S as they do on 2S. The only reliable guide is the clock - the set-up that gives the lowest average lap time over eight minutes is the one to have.

As an example, I ran my 10.5 LRP X11 on 54mm/rev with a non-timing speedo. On 203 - 212 I am running 46mm/rev. If I put that up to 48mm/rev, the car is noticeably slower. On 46, the temps are barely above luke warm, but the car is a bullet. On 48, the temps are much higher, the car is slower, and the drop-off after seven minutes is noticeable.

Whenever the car seems slow, go down 5mm/rev and see what happens - you might be very surprised - and happy! HTH
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Old 11-22-2010, 08:22 AM   #945
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Hey guys...

When switching from Nimh to Lipo, did you guys have to gear it lower??? My car was drastically slower, and the punch was gone when I tried the Lipo... It was so slow that I practically could not drive it without crashing.

I switched back to Nimh and it was all back to normal... Does this mean with Lipo I should get a faster motor???

Thanks for your help guys.
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