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Discussion Starter · #1 · (Edited)
Since the ROAR Region 5 Offroad Championship race was completed last weekend, I have had some time to break down someof the info I collected using the Eagle Tree System RC Car Data Recorder.

I ran it during 6 practice runs and recorded the following: battery volts, battery amps, RPM, throttle and sterring position, X and Y G-Force. 4 runs were made using an Assocaited T4 with a P2K2 tuned by me geared at 19/87. One run was made using a Putnam tuned Monster Stock geared at 17/87 and one additional run at 16/87 gearing.

The main info I got from the Data Recorder during the 4 pactice runs with the P2K2 (the normal motor I run) gave me base data and lap times. Of interest to me here was top speed was recorded as 28 MPH.

When running the the Putnam motor at 17/87 gearing, the top speed 30 MPH and the lap time was about 1 sec. faster.

When dropping to 16/87 gearing my top speed dropped back to 28 MPH but my lap time dropped an additional 1.5 seconds. From examining the data I could see I was losing about 1/3 sec. on the straight/long sweeper, but then gained about 2 seconds on the infield with a full 1 second gain between track points 3 & 6 (see track graphics below). That area of the track put a premium on accelleration and while I knew it was faster there I never would have throught it was that much.

Anyways, below is the data split out so you can see some interesting comparisions.

Track Picture and Track Layout Graphic

Steering & Throttle Positions plus RPM & Amps

Most of the data minus the G-Force. Netrual Throttle is about 140 on the scale, straight steering is about 120 on the scale.

Throttle Position vs Motor RPM

Interesting how the RPM ramps up after throttle is applied.

Motor RPM vs Watts (Battery Output)

See how Watts spike when hard throttle is applied and then trails off (points 1 through 3). Also shows where I was at netrual as the Wattage goes to zero and RPM slowly decreases, most noticable around point 3.

Battery Voltage vs Amp Draw

Shows effect of amp draw on battery voltage.

X (side to side) G-Force and Y (accel and decel) G-Force

Up to 1 G in both accel (Y) and cornering (X) even on dirt!

Throttle Position vs Y G-Force

Compare how throttle position effects accel (Y) G-Force.

Steering Position vs X G-Force

Compare steering to cornering (X) G-Force.

Any questions? Ask away!

1,023 Posts
hank thats real cool,1g on dirt who would of known
but if i had that i would just show me how bad my driving is...
but its realy cool to see this technoligy on rc cars. ...


12 Posts
Interesting to see your second graph there Hank - Motor RPM vs Throttle.

I've done a similar set of graphs over at www.rc-direct.co.uk - but with a touring car.

With my graphs, RPM's increase gradually after you open the throttle. But for you, the RPM's are peaking all over the place! Shows how much effect the bumps have on the traction you get - every time you lift a wheel or lose a bit of traction, the revs jump a little - astonishing how the data recorder picks it up.

I would imagine that a 4wd car still has a smoother RPM graph, because of the extra driven wheels that can keep traction over the bumps.

4 Posts
how did you manage to get such constand readings on your t4? i have my rpm sensor mounted in the same pace but with using shoe goo and lexan and i cant seem to get a good graph, its like its bouncin around alot. i hope to so try out my g-force sensor, last time i ran, i didnt have recent software. any hints with the rpm sensor would be great though.
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