I tried some different gears on the Lipo on Wednesday. I ran the 23,24 and 25 to see the speed difference.
I got the fastest times 4.4 out of the 23, the other two gears were increasingly slower. Just needs more work, the 1600s I was able to run 4.2s.. Could be the Lipo battery finally waking up, as the best run was in the main..
I have a statement and a bunch of questions in addition to Perjota's.
Cornering speed and handling was better. Bet you where eating up the competition in the corners and loosing some on the staights.
Testing reports that I heard about on a flat carpeted 125ft driveline track, stated that switching to the 1S 3.7 LiPo, speeds were significantly reduced from that of the 4.8 volt 1600's.
I have experienced and witnessed that running a Spec - Spec Legends on a 210 ft track top speeds is at 23-26 mph with laps times in the mid to low 6's with some peaking into the high 5's; with a 4.8 volt, 1600 battery. Same cars (and Drivers) on 120 ft carpet track, same set-up; top speeds are at 16-18 mph lap-times low 4's with a few 3.4 to 3.9's thrown in for good measure. Taking into account of the 3 teeth pinion rule 20, 21, 22, temps are wildly different on the two tracks.
What sized LiPo? You didn't mention - - - 3.7 1 (1S) or 7.4 (2S)?
How were your motor, ESC and Battery temps?
Long/Short Track, how long was the drive line, you didn't mention.
What was the race time and total laps turned, and how did you place?
Please be a little more specific in your reporting, as these cars are simple but react significantly to slightest change. Your input is great and I take it all in, weigh it, think it through and put it into application. I let my car down far more than it fails me!
We have now been running the SMC 4000mah 1 cell Lipo for the past 5 weeks..
It is important to discharge the lipo and put a good 5-8 amp charge on it.
I have now gone faster laptimes with the lipo than I ever ran with the 1600s, and I ran one tenth off at the end of a 6 minute run.
The biggest difference is that the Lipo doesn't slow down during the run.
We now run 5 minute heatraces and 6 minute mains..
All 5 cars in the A last night were using the lipos..
We've got a Legends race coming up in two weeks. I know i have a 1-cell and so does another guy... we'll try to run some practice laps and see what happens.
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Brevard Electric Auto Racers- Palm Bay, Florida
VTA and RCGT
We have been running SMC 1 cell lipo in Legends for a year. We also run 13.5 Novak motors.
I have never discharged a Lipo. My Orion and Peak Lipos say in the instructions never to discharge them. Because of that, I haven't the SMC either. Performance does not seem to have changed.
We run four minute qualifiers and five minute main. Have never experienced any heat in ESC, motor, or batt. High banked short carpet oval. Fast lap for Legend is 3.6 seconds. Run full speed continuously with no braking unless to avoid a wreck. To make turns back slightly off throttle. Tires are 2.22" with gearing of 24 pinion and 81 spur.
Unless the Trinity Spec Motor has improved significantly, you are not going to get much more than 16000 rpm from a straight off the shelf motor, IF your lucky* *There are a few motor builders that frequently exceed stock spec motors advertised performance.
With at 16000 rpm motor at dyno'd 5 volts, that translates to:
In addition to my questions not answered in from my last post, I have some more; my new questions are:
Does overcharging a LiPo (above the recommended C rating and that of the manufactureres recommendations) give you the extra voltage to make up for the "in theory" rpm loss... a good NiCad will only cause the motor to loose 1000-2000 rpm in 5 minutes due to drop in battery voltage. If you are exceeding the C rating and/or the manfacturers charging recommendations, are you not risking damage to your LiPo and putting other people at risk?
Again in theory, to make up for the RPM loss of 3520, then the recommended gearing for Legends Classis being exceeded by a few teeth, if you are maintaining the same lap times and speeds as a 4.8v battery.
The track I frequent has "opened up" the Legends gearing in order to make the LiPo competative with the NiCads. Also, from the reports I am getting/seeing the "go fasters and previous series champs" are sitting out the summer heat and leaving the LiPo testing to those less fortunate.
Does the weight difference in batteries make up for the voltage loss? The cars set-up must change doesn't it?
In order to go as fast as 4.8v battery; a 3.7v battery must be: Overcharged, Over-geared; something has changed to make up for such a loss in rpms.
I am confused by your testing without more details.
We have been running SMC 1 cell lipo in Legends for a year. We also run 13.5 Novak motors.
I have never discharged a Lipo. My Orion and Peak Lipos say in the instructions never to discharge them. Because of that, I haven't the SMC either. Performance does not seem to have changed.
We run four minute qualifiers and five minute main. Have never experienced any heat in ESC, motor, or batt. High banked short carpet oval. Fast lap for Legend is 3.6 seconds. Run full speed continuously with no braking unless to avoid a wreck. To make turns back slightly off throttle. Tires are 2.22" with gearing of 24 pinion and 81 spur.
Now we are sort of getting close to apples and oranges.
According to the Novak Charts that particular brushless motor provides approx another 1000 rpm over the stock Trinity Spec Motor with a 3.7v battery. Brushless motors make more torque than a brushed motor and it's heavier.
From the gearing, track type/surface (short-high banked), motor, and driving style leaves little doubt.
Pertinent information is not being provided to substantiate or validate these testing claims.
We did need to gear up a couple of teeth on the Brushless to make it as fast as the Spec motor. Also you need extra gear to utilize the power delivery from the Lipo. They are not over geared or over charged. No extra heat, no dead lipos, speeds and laps are very similar, we made no changes in the springs, tires, or anything else. I just changed motors and the battery and went racing.
Yes, it does help in comparing. This is on your short track? Your information shows that something needs (and was) to be done differently. Really, we aren't comparing the motors, but the voltage supplied to the motors, 4.8 vs 3.7.
It appears from earlier information, its necessary to go outside the Legends Gear rules (hence my term - over gearing) in order to run the same speeds or lap times with a 3.7 volt LiPo compared to a 4.8 NiCad.
In and earlier post, you mentioned there was a larger flat carpet track. Have you done comparisons there? What kind of information have you gotten from it?
I collect data ... I guess you can tell that... that's all I am after. The more I get, the more comfortable I feel in new situations. The track I frequent is changing to the 3.7 LiPo's too! Regretably, I cannot be there every week to do my own testing.
Your information on the 13.5, is 1 more confirmation that it could be a comparable motor to the spec motor now used. If the situation with parts availability continues to be "iffy". Actually, everything that you have posted has been helpful in some way due to its content.
But there is a lot of difference in a high banked oval compared to a flat tight turned oval.
Thanks for the info...
Pejota: Let us know how you do with the 3.7's. Should be interesting.
Tight, flat, concrete oval, and i mean TIGHT. I'll take measurements when i'm there.
We're currently running 4-cell, unrestricted mah, NiCads and handout motors, 27 turn i think but i'll verify. Everything else is per the rules.
I'll do a direct battery swap and get lap times. Then i'll gear up to try and match the NiCad times. I do have a 13.5 but that will be in my COT car so i probably won't be able to test with that.
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Brevard Electric Auto Racers- Palm Bay, Florida
VTA and RCGT
We will be doing testing on the large carpet oval this fall. I did some limited testing previously. I ran with the stock Legends but my laps did not count. Tires again were 2.25" 81 spur 22 pinion Novak XBR ESC and EX 13.5 motor. With the Trinity Spec 1600 battery the speeds were equal to the stock legends. I could run down the straight at the same speed and carry the same in the corner as the other Legends.
I did not get a chance to test on this track with 1 cell Lipo but imagine it will require a larger pinion to be the same speed as the stock Legends. Plans are that I will test further with the Race Director monitoring so we can adjust rules to make both types of cars compatible.
I took some time this weekend and reviewed the data that I have gleaned over time for a 120 ft flat carpet oval, 8 to 10 ft inside turns.
In a 5 minute heat, I pulled 67 laps at 4.4 sec avg lap times with a NiCad 1600 - 81/20 gear ratio and tires at 2.44 in. Finished 2nd a lap down due to some fender rubbing. A couple of laps here and there, varying between 3.9 to 4.4, with a bunch of 4.1's and slowing at the end. There were a few laps of 5 and 7 sec. Motor efficiency was at 97% (which several of us have validated). The average efficiency loss of 3 percent is acceptable.
In order to maintain that pace and maintaining the motor efficiency from the same motor. Gearing the car to 81/25 to 27, should be the ticket! That should glean 81 to 85 laps and make up for the rpm loss due to less voltage of a 3.7 LiPo.
Now I need to validate the loss of 25% in motor rpm requires roughly to a 18-25% change in gearing. This appears to be in the ballpark?
Ran 3rd of 5 in the A last night with Trinity spec 4cell batteries. 81/24 gears and ran some 4.6 laps maybe a 4.5 lap at Speed Sports in AZ. The top two had lipo and were ridiculously fast. My first heat I ran last. I changed motors and that was the big difference. Won the 2nd heat to make the A. I am concerned about gearing higher because of the possibility of draining the battery faster. Will the lipo start to have the big advantage because of the ability to run higher gears and last much longer? I am hoping to find a way to compete for the top spot in the A without going to lipo but I am not sure that will happen. Any thoughts?
It appears that you have unlimited gearing in your Legends class. If they can gear up lipos to any point they choose, you will find it hard to compete with spec batt (IMO). Even in a four or five minute race the fact that the lipo does not loose punch is a definite advantage when they are geared right.
You might be able to find another gear for your spec batt that would better match the lipo but you might also kill the spec batt too fast for a competitive race. Spec batts may become very rare soon and that is why our tracks (four in my area) are switching to lipo.
Looks like I am looking at switching to lipo I definitely do not want to worry about my battery dumping when competitors are running lipo and I am not. I need to get that extra straightaway speed also with those larger gears
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