what is your calculated mph?
05-13-2005, 06:17 PM
#26
Member
Join Date: Mar 2005
Location: Los Angeles,
CA
Posts: 91
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is your calculated mph?
ORIGINAL: rustler08
34.26 mph. and with a hacker on 18 cells rated at 1.18 volts per cell and are matched, is 128,000 rpm's! with 20% deducted, i got 134 mph. somewhere around there.
34.26 mph. and with a hacker on 18 cells rated at 1.18 volts per cell and are matched, is 128,000 rpm's! with 20% deducted, i got 134 mph. somewhere around there.
Tarkus
05-13-2005, 08:03 PM
#27
Senior Member
Join Date: May 2004
Location: Pittsburgh, PA
Posts: 2,093
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is your calculated mph?
ORIGINAL: sleepy23
hey skrap, how many cells did you use in your calc and what is the rpm/v on your feigao?
hey skrap, how many cells did you use in your calc and what is the rpm/v on your feigao?
The calculation is fluid. Whatever number of cells you have, multiply that my 1.2 ( volts per cell). I know there's no cell in the world that will truly give you 1.2v, but it's a good ball park figure to work with.
The Feigao 8s is rated for 4436 k/volt and the 6s is rated at 5915 k/volt. My APS dyno isn't the greatest, but it shows about 4388 k/volt static on the 8s and 5993 k/volt static on the 6s. In application, at 1.175v per cell 6 cells, the 8s got 24,884 under load, and the the 6s clocked in at 33,800 rpm. Not bad, considering I had a 20% torque load on the motor.
I just don't trust it, because it uses an optical rpm sensor. It's not a TRUE dynometer, but again, it gets me a ball park figure.
05-13-2005, 11:40 PM
#28
Banned
Join Date: Jan 2004
Location: Knoxville, TN
Posts: 5,195
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is your calculated mph?
Sleepy, it is indeed overgeared.. Like to the moon =) But it makes for one killer qualifying setup when the track is right. I ran it 20 laps tonight and temp'd it, 194.. heheheh It showed me what I wanted. I actually backed it off a tooth after than and it ran just as strong and 30 degrees cooler. I spent the rest of the night working on the T4.. The Losi made me happy.....
05-14-2005, 01:52 AM
#29
Thread Starter
Join Date: Oct 2004
Location: Yuma,
AZ
Posts: 254
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is your calculated mph?
I just thought of something, at work, I have a little speed device that I use to measure RPMs on our generators. I could put a motor in a vice(very carefully of course) and hook up the tool to it. It kinda looks like a dremel tool. Basically how it works is, with the engine running, I put the tip of the tool up to a belt or pully on the engine, which would spin the end of it and it reads how fast it's going. I suppose I could use it to see what kind of condition an RC motor is in by how many RPMs it cranks out. I think it also does MPH or instead of miles, feet or something. Been a long time since I used it. But might help with tuning...?
05-14-2005, 12:39 PM
#30
Senior Member
My Feedback: (1)
Join Date: Sep 2003
Location: Maryville, TN,
Posts: 5,002
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is your calculated mph?
well looks like i will soon be find out how fast i am going and if my eagletree is being accurate when its upderload....i just won a gps on ebay ( got the yellow one everyone else has). i think i am going to go ahead and get an 8 cell pack from elmo and try it all( including my ti driveshafts and my brand new 3gram top shaft) out maybe by next weekend.
i am pretty excited about that.
i am pretty excited about that.
05-14-2005, 07:06 PM
#32
Senior Member
Join Date: Dec 2004
Location: Izmir , TURKEY
Posts: 1,172
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is your calculated mph?
actually depending on the tranny, the average on euro cars is about 14-18% thru the transmission
ORIGINAL: 45mph pede
Yup, just like a 200hp motor is not going to pull 200hp, you lose about 5%-8% in the tranny.
-Wes
When you do that calculation, you need to figure on about a 12-15% difference between the theoretical top speed, and the true top speed. The 12% drop is due to voltage inconsistencies, friction loss, wheel slip, aerodynamic drag etc. That percentage becomes exponential, the faster you go. I really need to develop a bell curve to illustrate that.. My brushless B4 for example, has a 28.7% difference between real speed and theoretical speed. (85.44mph calculated speed, 61.2mph measured speed.)
-Wes
