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-   -   SE 1/4 mile speed tests (http://tinyrc.com/forums/showthread.php?t=22096)

Steve 02-04-2006 08:25 PM

SE 1/4 mile speed tests
 
EDIT - NEW INFO! 2/17/06

Built a scale 1/4 mile drag strip (20.625') with a full length timer and a laser speed trap at the last foot. Here are some results for a stock 4th Gen SE:

In all cases red idler and axle were used. No body or front tires. 3 "good" runs per motor.

21,500 RPM MOTOR (red)

2.951 @ 5.73 MPH / 4.77 MPH Average
2.959 @ 5.63 MPH / 4.75 MPH Average
2.911 @ 5.88 MPH / 4.83 MPH Average

23,500 RPM MOTOR (yellow)

2.673 @ 6.20 MPH / 5.26 MPH Average
2.640 @ 6.26 MPH / 5.33 MPH Average
2.741 @ 6.10 MPH / 5.13 MPH Average

28,000 RPM MOTOR (orange)

2.479 @ 6.75 MPH / 5.67 MPH Average
2.507 @ 6.75 MPH / 5.33 MPH Average
2.433 @ 6.75 MPH / 5.78 MPH Average

34,000 RPM MOTOR (purple)

2.475 / 5.68 MPH Average
2.535 / 5.55 MPH Average
2.463 / 5.71 MPH Average

I included the average speed numbers because I think it gives some idea of accelleration. There may be more to the numbers than meets the eye so I recorded everything.

EDIT: I did some more testing, and I think the top speed numbers I've been getting are not very accurate. The timer resolution isn't high enough to properly guage speed across the short 1 foot trap. The highest I've ever seen it go is 6.75 MPH, which is roughly .100s. The software won't register times below that. Which means, I need to lengthen the speed trap distance, but I don't think that those numbers would mean much either as I think the cars might still be accellerating at 17, 18 or even 19' down the track. SO, I've decided just to do away with the speed trap at the end of the track. For my purposes, it's really only the ETA that matters. For future testing, top speed numbers won't be available. As for the numbers already posted, I'll leave them there, just don't take too much stock in them.

rfnagel 02-04-2006 11:30 PM

That's some interesting info there Steve, thanks for the testing and posted results :thumbsup: -:)

Quite interesting stuff when compared to my Motor and Gear Ratio Chart (derrived from my ZipZaps Speed Calculator v4.0 utility).

(Edit)

Sort of proves what I've been saying all along (RE: This Web Page), that the higher RPM motors have more torque than the lower RPM motors.

A bit of explaination of this:

The higher RPM motors have more torque, hence errors with my Zipzaps Speed Calculator Utility (which is nothing more than a mathematical comparison/calculator) when compared to your real-world results are less with the 34,000 RPM (purple) motor due to it's higher torque... which would be affected less by friction, battery condition, PC board version, track surface, laws of physics, etc... (that my ZipZaps Speed Calculator utility does not take into account) because of it's higher torque.

Steve 02-05-2006 11:33 AM

Yeah, it is interesting. The lower RPM motors cetainly get up to speed faster, but they have less to go before they wind out. I suspect this is why they appear to have more torque, because they are usually operating in the higher RPM range. If the ZZ had a clutch (oooh!) which allowed the higher RPM motors to get going before applying power to the wheels, we might see some very different numbers in regards to torque.

It makes sense really when compared to real world engines. The smaller tuner type engines need to operate at high RPM's to maintain respectable power. With the fast ZZ motors, they have the power, it's just a matter of getting the engine up to speed so that it can be used.

What then? Well, the gearing options on the ZZ are such that we are extremely limited. We can't gear high enough to allow a low RPM motor to produce the speed needed on the 1/4 mile. They simply max out shortly after launch. The opposite is true with the fast motors. While the high end speed is good, we can't gear low enough to get a good launch.

I'm dying to get another laser pointer so that I can measure 1/4 mile TIMES. Until then, keep modding.

chilli_mp138 02-05-2006 08:49 PM

Steve--

Quote:

Originally posted by Steve
We can't gear high enough to allow a low RPM motor to produce the speed needed on the 1/4 mile.
For what kind of gear ratio are you looking to do the quarter mile?

chilli

Steve 02-05-2006 11:05 PM

IF...IF the 10k motor has more torque than the faster motors, we should be able to in theory, gear it higher, accellerate quicker, and possibly make the 1/4 mile in less time than a higher RPM motor that, although faster, takes much longer to accellerate.

The blue motor with red gearing still accellerates to top speed very quickly. I don't know the ratio, I was just thinking taller gears would be nice to play with.

chilli_mp138 02-06-2006 11:40 AM

Steve--

Thanks for your reply.

8-, 9-, 10-, and 11-tooth pinion gears are available by cutting apart the various ZZMT transfer gears. Similar pinion gears are also available on Super Slick motors. Perhaps these, depending on gear mesh, would give you the ratios to run a faster quarter-mile with the blue motor.

Will your new tire discovery also help?

chilli
http://www.gcrossett.com/zipzaps/mod..._gear_options/

hschnark 02-07-2006 03:17 PM

SE 1/4 mile speed
 
Steve,

What kind of a laser speed trap did you use?

Thanks,
Hugo

Steve 02-07-2006 05:38 PM

1 Attachment(s)
I used the setup in the drawing. The photocells are connected to a laptop via parrellel port. The laptop runs Laptimer 2000 slot car timing software. It's setup so one lane times the whole 20', and the other lane times only the last foot, so at the end of a run you get top speed and elapsed time.

hschnark 02-08-2006 03:04 PM

Steve,

Neat set up. I tried to do the one foot thing with a ZZ Speed & Lap Counter but the LED isnít strong enough. I suspect it would work if I had the right light source. Has anyone else tried that?

Hugo


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